Nautical Science Basic Studies Textbook PDF

Nautical Science basic studies Laurentiu CHIOTOROIU BASICS IN MARINE ENGINEERING. REMOTE CONTROL AND MONITORING SYSTEMS Textbook V.15_2024 Fachbereich Seefahrt und Logistik in Elsfleth Faculty of Maritime and Logistic Studies in Elsfleth Note: This textbook is a supplement to the classroom lect...

Nautical Science basic studies Laurentiu CHIOTOROIU BASICS IN MARINE ENGINEERING. REMOTE CONTROL AND MONITORING SYSTEMS Textbook V.15_2024 Fachbereich Seefahrt und Logistik in Elsfleth Faculty of Maritime and Logistic Studies in Elsfleth Note: This textbook is a supplement to the classroom lectures and should not be regarded as a scientific work / technical book. Not all cited or extracted texts and images have been marked. The present script has been created exclusively for use in the context of Prof. Dr. -Ing. L. Chiotoroiu's lecture. Duplication and other use is not permitted! The textbook contains also some results of the didactic project “JADE-BLESSC” 2018  Course Introduction (Einführung in Systemüberwachung) Term: WiSe 2024/25 Level: Undergraduate Coordinator: Prof. Dr.-Ing. L. Chiotoroiu Course meeting times: 2 lectures/week Class meeting: Face-to-face classes (alternatively Hybrid or online via Zoom) Consultation hours: Tuesdays 11:30 – 13:00 hrs. (per request) Office phone: 04404 9288 - 4159 E-mail: [email protected] Course structure: This course, designed for either face-to-face, hybrid- or online-study approach, has been organized into five major units: Part 1 – Familiarisation with the Engine Room and green technologies to reduce and control the GHG emissions Part 2 – Operating principles of marine power plants Part 3 – Basic knowlegde of equipments and ship’s auxiliary machinery Part 4 – Operating and auxiliary systems Part 5 – Bridge & engine room remote and local control of the machine Each of the five major units has been further divided into 12 Topics, where each topic covers an amount you might expect to complete in one week, i.e. in two lectures. At the end of each Topic, there are sets of Revision exercises & questions in the textbook, as well as Quizzes available in LMS Moodle, to test your understanding of the material. Jade UAS expects its students to spend about 125 hours on the Marine Engineering course during the winter semester 2024/25. More than half of that time (65 hours) is assumed to be spent by you for self-study, that includes reading of the textbooks & additional course literature and the self-study topics, preparing two home projects as result of teamwork, as well as watching the video clips posted in Moodle and testing yourself, using the formative self-assessment methods (quizzes or free-simulator VER6). It’s difficult to estimate how long it will take you to complete each weekly topic, but you can probably expect to spend on average four hours or more working for the preparation and follow-up of the Material / exercises, including the exam preparation. For a more detailed information, see the “Course estimated schedule_WiSe 2024” in Moodle. Instructional/Teaching strategies: The Marine Engineering course is built on the following teaching strategies:  1. Further reading The recommended literature for this course is available at “Other References” in.pdf format in Moodle. 2. Innovative technology brought into the classroom - Visualisation Based on an interactive learning approach, almost each Topic is accompanied by a number of resources in Moodle, such as short explanatory videos created using the Lightboard Studio (work in progress). Moreover, the use of the free Unitest simulator VER, the specialised desktop Unitest simulators TD5 and VER6 or the Unitest CBT’s will help you to visualise and better understand most of the topic concepts. 3. Independent study A number of Topics are given for self-study, as indicated in the “Course estimated schedule_WiSe 2024” file in Moodle. You should read and prepare for presentation two home projects, as well as the major unit 5, given as an e-learning module for self-study. 4. Assessment-based instructional strategy Almost every Topic in Moodle ends with a “Quiz_Topic XY”, that is a collection of review questions & exercises. You are encouraged to discuss with your mates about difficulties encountered and try solving them ! In addition, a free-version of the Unitest simulator VER is available for download. 5. Cooperative learning A series of Topics in Part 3 and Part 4 are given in form of home projects. The key idea behind is to work together in small groups (2-3 students) trying to research, analyse, interpret and present the respective home projects in front of your colleagues. Starting with WiSe 2023/24, the presentation of your home projects can be voluntarily done in form a (*.mp4) video, created in the new Lightboard Studio, located in W206. To those who prepare and deliver their presentation using the LBS (Lightboard studio), a number of 3 exam points will be allocated to each team member as a reward. So, in case of two home projects, you can already benefit from 6 points out of a total of 100 points. Marine Engineering Exam: Final examination: To be prepared for the final exam, check first that you are proficient in each of the Topics given in the “Exam summary” file. This document gives you a perfect idea about the exam and helps you getting confidence and improving your question-solving skills within the 2 hours exam time. As a rule of thumb, the exam summary is made available to you ca. 1 month in advance from the final exam.  Learning Objectives: On successful completion of this topic, the students should be able to: Use generally accepted engineering terms when describing and explaining the machinery space; Describe the layout and general arrangement of machinery and equipment in an engine room; Explain the advantages and disadvantages of different propulsion systems architecture.  Part 1 - Familiarisation with the Engine Room and green technologies 1.1. Basic machinery space arrangement and propulsion architecture In a ship, an engine room is where the main engine(s), generators, compressors, pumps, fuel/lubrication oil purifiers and other major machinery are located. It is sometimes referred to as the "machinery space". On modern ships, a sound-proofed, air-conditioned engine control room (ECR) is situated next to the engine room (ER), for the ship's machinery control systems. Figure 1.1. Engine room – general view1 Engine rooms are hot, noisy, sometimes dirty, and potentially dangerous. The presence of flammable fuel, high voltage equipment and prime movers means that a serious fire hazard exists in the engine room. That’s why the operation is monitored continuously by the ship’s engineering staff and various monitoring & control systems. 1 Picture from Future Ship Powering Options, 2013, page 69 V15_2024 Page 2  Part 1 - Familiarisation with the Engine Room and green technologies GENERAL MACHINERY SPACE ARRANGEMENT: PROPULSION ARCHITECTURE AND ENGINE ROOM LAYOUT The propulsion plant architecture, as well as the general engine room layout depends on the type and operating profile of the ship, as well as on the type of the prime mover installed. The main role of the prime mover is to propel the ship by delivering mechanical energy to the propeller. A detailed description of the most common prime movers is given in Chapter 2 of this textbook. The propulsion system architecture can be typically categorised as follows: 1. Mechanical propulsion 2. Electric propulsion 3. Hybrid propulsion 1. Diesel-mechanic propulsion This is still the preferred propulsion plant for ships that sail at a single cruise speed most of the time, because its fuel efficiency at full load is high. Examples of such ship types are cargo ships and fast crew suppliers. The propulsion power of cargo ships is delivered by a slow- speed or medium-speed main diesel engine directly connected to the propeller shaft (direct drive) or indirectly via a gear reduction box (geared). Alternatively, ships with a limited number of distinct operating modes can benefit from mechanical propulsion with multiple shafts and/ or multiple engines on one shaft, through a gearbox with clutches. These engines can be of the same type or of different types. Such configurations with multiple engines and shafts can also improve propulsion availability. For more information, see Combined Power Plant in Chapter 2.3. V15_2024 Page 3  Part 1 - Familiarisation with the Engine Room and green technologies Figure 1.2. Example of a diesel-mechanic propulsion plant with controllable pitch propellers and twin-engines2 For a typical diesel-mechanical propulsion, the engine room layout consists of the main engine(s) as well as all the other major machineries located at different levels/platforms: 1. Bottom plates level – above the ship double bottom (at the tank top plating); 2. Middle plates level – at the fuel pumps level; 3. Upper/Top plates level – where the main engine exhaust valves are located. The platforms are arranged in such a way as to ensure safe escape routes for the crew. The minimum sizes required by the classification societies are met to ensure sufficient headroom (h = min. 2m). A typical merchant vessel propelled by a low-speed diesel power plant is presented in the figure below3. 2 Picture adapted from T. Lamb (2003-2004), Ship Design and Construction, page 29-37 3 Picture 7 page 17 from Marine Engineering, SNAME V15_2024 Page 4  Part 1 - Familiarisation with the Engine Room and green technologies Typically, the machinery space is located in the aftermost hull compartment, at 1/3∙L or even 1/2L measured from aft perpendicular AP. However, the exact engine room location depends strongly on the complexity of the plant, the overall design and the ship type. 2. Electric propulsion Due to its success in the cruise industry since 1990s, electric propulsion has also been applied in ferries, offshore vessel fitted with DP (drilling vessels, cable layers, etc.), icebreakers. The choice for electric propulsion is mainly determined by their diverse operating profiles, as these lead to a large benefit for the power station concept. A typical architecture of an electric propulsion system is given in Figure 1.3. Figure 1.3. Typical electrical propulsion layout4 4 AP R.D. Geertsma et al. / Applied Energy 194 (2017), 30 – 54, page 38 V15_2024 Page 5  Part 1 - Familiarisation with the Engine Room and green technologies As given in Figure 1.3. above, the main components of a diesel electric power plant consist of a number of auxiliary diesel engines, electric generators that together with the diesel engines are known as “Gensets” or “Diesel Generators”, power cables for power transmission and the Propulsion Electric Motors (PEMs). Figure 1.4. Own Photo from Meyer Werft GmbH & Co KG Papenburg, Sept. 2019 Some advantages & disadvantages over the mechanical propulsion: (+) The electric propulsion is a fuel-efficient propulsion solution when the hotel load is a significant fraction of the propulsion power requirement and the operating profile is diverse, because the generator power can be used for both propulsion, through the electric motors, and auxiliary systems; (+) Reduced NOx emissions, because the propulsion power at full ship speed is split over more engines, which due to their lower individual power run at a higher speed; (+) Flexibility in positioning machinery spaces (due to the absence of the shaft-line); (+) Reduced maintenance load, as engines are shared between propulsion and auxiliary load and are switched off when they are not required. (-) Electrical propulsion incurs increased electrical losses, that lead to an increase in SFC, particularly near top speed of the ship; (-) When running redundant engines to achieve high propulsion availability (for example in DP operations), the engines run at low part load. This leads to poor fuel consumption and a lot of emissions. In the image below, you can note the shaft of the fixed pitch propeller (FPP) propulsion plant is not directly connected to the diesel engines (Gensets) via a gearbox, but to a propulsion electric motor (PEM). The electric power for the PEM and further consumers is produced by a set of generators (electric alternators) driven by medium-speed diesel engines, as displayed in Figure 1.5. This propulsion setup is termed as “diesel-electric propulsion” and, as mentioned, requires less space in the engine room since the PEM and gensets can be physically separated. In fact, only the electric motors need to be close to the propulsors. Gensets may be located at any convenient place in the ship. More information about the Diesel-electric drive can be found in Chapter 2.4. V15_2024 Page 6  Part 1 - Familiarisation with the Engine Room and green technologies Figure 1.5. Example of a diesel-electric propulsion plant with fixed pitch propellers FPP5 Electric podded azimuth POD-drive (or AZIPOD, if produced by ABB) This is a special electrical propulsion system available since 2000, with the FPP and the electric motor PEM mounted outside the hull, below the stern part of the ship, into a rudder- shaped steerable gondola. Figure 1.6. shows the separation of power generation by GenSets in the forward part of the engine room, and propulsion by PODs at the aft end of the ship. Figure 1.6. Example of a POD drive with fixed pitch propellers FPP6 Figure 1.7. Own Photo from Meyer Werft GmbH & Co KG Papenburg, Sept. 2019 5 Picture adapted from T. Lamb (2003-2004), Ship Design and Construction, page 29-37 6 Picture adapted from T. Lamb (2003-2004), Ship Design and Construction, page 29-37 V15_2024 Page 7  Part 1 - Familiarisation with the Engine Room and green technologies Nowadays, the POD drive represents one of two top choices to be installed on new-built cruise ships. 3. Hybrid propulsion The hybrid propulsion is a combination of mechanical and electrical propulsion, optimising the propulsion efficiency for ships with a flexible power demand. Typical applications of hybrid propulsion systems are those ships with different operation modes and sailing speeds, such as naval frigates and destroyers, towing vessels, offshore vessels and some ferries or yachts. A typical architecture of a hybrid propulsion CODLAD system is given in Figure 1.8. below. Figure 1.8. Typical hybrid propulsion layout7 The mechanical power, delivered by diesel engines work together in the propulsion train with the electrical power, provided by electrical motors. The E-motors (2) are fed from the GenSets and coupled to the same shaft through a gearbox (3), providing propulsion power for low speeds. In this case, the main engine is switched off. Additionally, a direct mechanical drive – main diesel engine (1) delivers propulsion power for high speeds, when running at full load with high efficiency. In this mode, the E-motor can be switched off, used as an electric assist motor or used as a shaft generator. More information about the hybrid propulsion configurations (CODLAD or CODLOD) are given in Chapter 2.3. 7 AP R.D. Geertsma et al. / Applied Energy 194 (2017), 30 – 54, page 41 V15_2024 Page 8  Learning Objectives: On successful completion of this topic, the students should be able to: Use generally accepted engineering terms; Describe the Marpol Annex VI regulations on CO2, SOx and NOx and know the methods to reduce and control the gas emissions; Explain the advantages & disadvantages and the principle of operation of different green technologies; Describe the chemical properties of LNG, the step-by-step bunkering procedure & the LNG storage system on board.  Part 1 - Familiarisation with the Engine Room and Green technologies 1.2. Technologies to reduce & control the exhaust gas emissions EMISSIONS CONTROL UNDER MARPOL ANNEX VI “Emission means any release of substances from ships into the atmosphere or sea” Exhaust gas emissions (pollutants) emitted from marine diesel engines comprise carbon dioxide (CO2), carbon monoxide (CO), oxides of Sulphur (SOx), nitrogen oxides (NOx), hydrocarbons (HC) and particulate matter (PM) such as particles, soot or smoke. The two main pollutants Nitrogen oxides (NOX) and Sulphur oxides (SOX) are of special concern as threats to vegetation, the environment and human health. During the 1990s, attention to air pollution and global warming led to new regulations restricting the emission of the oxides of nitrogen (NOX) and sulphur (SOX) pollutants produced during combustion in diesel engine cylinders and emitted in form of smoke to the environment. These regulations are stipulated in MARPOL Annex VI of IMO, first adopted in 1997. The revised MARPOL Annex VI (Regulation 13 ref. to NOX emission standards) is arranged in three tiers: Tiers I, II and III and entered into force on 1 July 2010. Figure 1.9. NOx limit – MARPOL Annex VI, Reg. 131 Tier I sets requirements for ships with a keel laying date on or after 1st January 2000 and prior to 1st January 2011. In general the operation of marine diesel engines of these ships is prohibited unless they meet the following nitrogen oxides NOx emission limits. The variable „n“ is the number of revolutions per minute. 17,0 (g/kWh) when n < 130 rpm 45 n (-0.2) (g/kWh) when 130 < n < 2000 rpm 9,80 (g/kWh) when n > 2000 rpm Tier II applies globally and consists of requirements for the operation of a marine diesel engine over 130 kW installed on ships built on or after 1st January 2011. The limits for nitrogen oxides NOx emission are as follows: 14,40 (g/kWh) when n < 130 rpm 44 n (-0.23) (g/kWh) when 130 < n < 2000 rpm 7,70 (g/kWh) when n > 2000 rpm 1 Picture from 6th Asian Shipbuilding Expert’s Forum, Guangzhou, November 22, 2012 page 5 V15_2024 Page 9  Part 1 - Familiarisation with the Engine Room and Green technologies Tier III The requirements apply to each marine diesel engine installed on ships with a keel laying date on or after 1st January 2016 when the ship is operating inside designated NOx Emission Control Areas (NECAs). 3,40 (g/kWh) when n < 130 rpm 9 n(-0.2) (g/kWh) when 130 < n < 2000 rpm 2,0 (g/kWh) when n > 2000 rpm Current NECA areas are the North American area and the U.S. Caribbean area. If the ship is not operating in a NECA, Tier II is applicable. Also Tier III shall not apply for marine diesel engines on board ships with less than 24 meters in length dedicated for recreational purposes or marine diesel engines with less than 750 kW rated diesel engine propulsion power if the ship is limited because of its design/construction. The revised MARPOL Annex VI (ref. to SOX emission standards) vary depending on where the ship is sailing. The Regulation 14 indicates that, starting with 1st January 2020, the Sulphur cap is reduced to 0,5%: We are here ! More stringent emission levels for SOX (0,1 % from 2015) apply in certain Emission Control Areas SECA’s: Currently there are four SECAs located in the: - Baltic Sea, - North Sea, - around North America and (coast of USA) - US Caribbean Sea. Discussed ECA’s: Mediterranean Sea Tokio Bay, Coasts of Mexico, of Alaska, Canada, Australia etc. Figure 1.10. Existing and possible future Emission Control Areas (SECA‘s) 2 2 Picture from Rickmers-Line GmbH & Co. KG 2017 V15_2024 Page 10  Part 1 - Familiarisation with the Engine Room and Green technologies 1.2.1. REDUCTION OF CO2 We all heard about the IMO strategy on reduction of GHG Emissions from ships: 40% reduction in carbon intensity of all ships by 2030, 70% by 2040 compared to 2008 baseline and Net-zero (total decarbonization) by 2050! On 1.November 2022, new amendments to MARPOL Annex VI entered into force: the technical measure EEXI and the operational measure CII. The requirements for EEXI and CII certification came into effect on 1 January 2023. The first annual reporting is to be completed in 2023, with initial CII ratings given in 2024. EEXI – stands for “Energy Efficiency Existing Ship Index” CII – is the acronym for “Carbon Intensity Indicator”. Source: https://www.imo.org/en/MediaCentre/HotTopics/Pages/EEXI-CII-FAQ.aspx From 1 January 2023 it became mandatory for all ships to calculate their attained EEXI to measure their energy efficiency and to initiate the collection of data for the reporting of their annual operational carbon intensity indicator (CII) and CII rating. In fact, both require ships to improve their energy efficiency in the short term and thereby reduce their greenhouse gas emissions. Source: https://www.imo.org/en/MediaCentre/HotTopics/Pages/EEXI-CII-FAQ.aspx V15_2024 Page 11  Part 1 - Familiarisation with the Engine Room and Green technologies Regarding the CII, ships are required to calculate their annual operational Carbon Intensity Indicator (CII) and associated CII rating. Carbon intensity links the GHG emissions to the amount of cargo carried over distance travelled. As already mentioned, the overall ambition is to reach net-zero GHG emissions by or around 2050. 1.2.2. METHODS TO REDUCE THE NITROGEN OXIDES (NOx) The term nitrogen oxides (NOx) is used to group both the (NO) and (NO2) components, that are formed during the combustion process in the diesel engine. The nitrogen N2 in the scavenge/intake air (ca. 79%) reacts with oxygen O2 and form nitric oxide (NO) and nitrogen dioxide (NO2). The combustion temperature and oxygen concentration represent the dominant factors influencing the (NOx) production: the higher the combustion temperature and longer the residence time of the combustion gases at these high temperatures, the more NOx will be created. Several technologies to reduce the level of harmful (NOx) emissions have already been developed or are in the process of adaptation to market needs. These NOx emissions can be abated by using primary and/or secondary methods: (ENGINE INTERNAL) PRIMARY METHODS Primary methods aim to reduce the formation of NOx emissions using a modified engine design approach. These engine internal methods met the IMO expected Tier II NOx emission levels. Some of the primary methods available today or under test and maturing for future regulations can be summarised as follows: Electronic control of fuel injection Delayed (retarded) fuel injection V15_2024 Page 12  Part 1 - Familiarisation with the Engine Room and Green technologies Reduction of cylinder lube-oil consumption, using Alpha Lubricator (MAN Diesel) or Pulse Lubrication System (Wärtsilä) Introduction of water in the combustion chamber – the so-called “Wet technologies”: Direct Water Injection (DWI); Water Emulsification or Water-in-Fuel (WIF) and scavenge air moisturising (SAM) or Humid Air Motor (HAM) Recirculating part of the exhaust gas: Exhaust Gas Recirculation (EGR). EGR = Exhaust Gas Recirculation EGR is a method related with combustion process: some amount of engine exhaust gases is send back to the scavenge space to mix up with the air to be supplied to cylinder for combustion. This reduces the oxygen content of the air and hence reduces formation of NOx. This means: Higher specific heat capacity of cylinder charge per unit mass of fuel (due to more CO2) Slower combustion (due to less O2 content) Reduced peak combustion temperature. EGRTC = Exhaust gas recirculation with T/C cut-out matching (alternatively, some new engines use the EGRBP with bypass matching system). EGRTC system layout – EGR not in use EGRTC system layout – EGR in use EGRTC in use – principle of operation At first, during EGRTC operation, the small T/C is cut out. Part of the hot exhaust gas (at ca. 4 bars and ca. 400 deg) is guided from the exhaust gas receiver through a Pre-Scrubber. The pre-scrubber cleans and cool down the gas by injecting water into the gas. The temperature falls to ca. 80 deg. due to water evaporation. The gas flows then through an EGR Cooler where is further cooled. The cleaned, cold gas goes then into a Water Mist Catcher (WMC). In this mechanical device, water is separated/ removed from gas – may disturb the lube oil film in the cylinder liner – by passing through a lamellar air flow reversing chamber. The water droplets are collected to the bottom of the manifold and drained out before enters the engine using a drain valve. V15_2024 Page 13  Part 1 - Familiarisation with the Engine Room and Green technologies Then the dry gas enters an EGR Blower, which raises the pressure to the right scavenge air pressure. Finally, the gas is mixed with normal scavenging air inside the air receiver. The ratio of recirculation (typically 30-40%) is controlled by the Blower, which in turn is controlled by the oxygen content ratio of intake air and exhaust. The remaining 60%-70% exhaust gas is matched with the large T/C unit. By using EGR system in combination with other technologies such as SAM, WIF or delaying the fuel injection, NOx Tier III standards can be achieved. (ENGINE EXTERNAL) SECONDARY METHODS Secondary methods reduce NOx in the exhaust gas by up/downstream treatment. Selective Catalytic Reduction (SCR) is such a system that can give the largest reductions: the emissions are cut by well over 90%. This means the expected Tier III 80% NOx reduction requirement can currently be met by the use of SCR technology. SCR = Selective Catalytic Reduction SCR is a technology related to exhaust gas after-treatment process, so regardless of combustion process. The SCR technology is equally applicable to low-speed and medium- speed engines. However, the place to fit the SCR unit differs due to the required temperature regime: from 300 to 400°C for an optimal catalytic reaction. Low-speed (crosshead) engines For the two-stroke engines, the exhaust gas has a temperature between 280 and 400°C. In this case, the SCR unit must be located before/ upstream the turbocharger, in the high- pressure side. The system is called SCR-HP or HPSCR. Medium-speed engines As the four-stroke engines have a sufficiently high exhaust gas temperature between 350 and 520°C, the SCR unit can be fitted anywhere, commonly after/ downstream the turbocharger. The system is known as SCR-LP or LPSCR. Standard working principle of a SCR system with ADBLUE for diesel engines in PKW’s (Automobile) V15_2024 Page 14  Part 1 - Familiarisation with the Engine Room and Green technologies NOTE: OXI-KATs are oxidation catalysts, used in diesel engines or gas or petrol engines for the exhaust gas after-treatment. Their main role is to reduce the CO, hydrocarbons and methane slip. On ships, there is no upstream or downstream Oxi-Kats (oxidation catalysts) installed, as there is a large oxygen concentration in the exhaust gas and the reduction of NO2 is therefore not possible. Principle of operation of SCR system on board ships: The SCR system converts NOx into harmless nitrogen and water, by means of a reducing agent – UREA. In practice, a 40% aqueous solution of urea is injected by means of compressed air into the mixing duct where mixes completely with the exhaust gas. The water in the urea solution is evaporated and urea decomposes to form ammonia and carbon dioxide before absorption onto the reactor catalyst. Here the NOx go through a reduction process, the end products of the reaction being pure nitrogen and water. No liquid or solid by-products are produced. Urea is favoured as a reducing agent because it is colourless, odourless, non-toxic, biologically harmless and can be transported and stored without problems. Figure 1.11. Marine SCR arrangement for a four stroke medium-speed engine3 In case of slow-speed engines, as mentioned, the common choice is the HPSCR because the exhaust gas temperature after the turbocharger can be smaller than 300°C. Recall the flue gas temperature should be min. 300°C for optimum catalytic reaction. If the temperature would be too low (less than 290°C), the reaction rate will also be too low, and condensation of ammonium sulphates will destroy the catalyst. On the other hand, if temperature is too high, above 400°C, ammonia will burn rather than reacting with NOx which will lead the system to be ineffective. Consequently, to keep the temperature within the required limits, the SCR system must be located between the exhaust gas receiver (1) and before/ upstream the turbocharger (4). The main components of such a SCR system are indicated below: 3 Picture from: Lloyds Register, Understanding exhaust gas treatment systems, Guidance for shipowners, page 32 V15_2024 Page 15  Part 1 - Familiarisation with the Engine Room and Green technologies (1) The exhaust gas receiver (2) A mixing duct or vaporizer, containing urea injection nozzle (3) SCR reactor (contains replaceable catalyst blocks and soot blower) (4) The turbocharger (5) A pump to transfer urea solution from storage tank to mixing duct (6) Urea dosing unit (typically 40% urea solution) (7) A soot/ash cleaning system (8) A control system Probably the biggest disadvantage of the SCR system is the massive dimensions of the SCR reactors, mixing ducts and the auxiliary equipment. This means to retrofit the installation on an existing vessel is far more complicated and impractical than to integrate the technology as the ship is being built. (2) (3) (4) (1) 1.2.3. METHODS TO REDUCE THE SULPHUR OXIDES (SOx) The sulphur oxides (SOX) derive directly from the sulphur content in the fuel. The ship emissions of SOx are harmful to human health and environment, causing respiratory problems, lung disease and damaging the vegetation. When the sulphur reaches the combustion chamber, get oxidised forming sulphur dioxide (SO2) and sulphur trioxide (SO3) in a minor proportion. On its way to the funnel and in contact with (NO2), sulphuric acid is formed leading to acid rain. V15_2024 Page 16  Part 1 - Familiarisation with the Engine Room and Green technologies As mentioned in Regulation 14 of the revised Marpol Annex VI, the sulphur cap has been reduced as indicated in the Table below: Implementation (SOx) (SOx) Emission date Global Control Areas (SECA) 1st January 2015 3,5 % 0,1 % 1st January 2020 0,5 % Table 1.1. Current fuel sulphur limits In addition, an EU Directive requires vessels while at berth in EU ports, including ports outside the ECAs, to burn fuel with a sulphur content not exceeding 0,1% (by mass). To comply with the strict emission limits laid out in IMO 2020, in particular in SECAs, there are currently three possibilities a shipowner can opt for: 1) Use of a low-sulphur fuel 2) Use of high-sulphur fuel (HFO) and install an approved Exhaust Gas Cleaning System EGCS = Scrubber. 3) Convert the ship to LNG operation (dual-fuel DF engines). The best solution will depend on a range of factors, including the amount of time spent in ECAs, the vessel’s machinery configuration, the fuel consumption and ship’s age. 1) Fuel switch to low-sulphur content fuel The average sulphur content of heavy fuel oil (HFO) used for marine diesel engines is between 2,7 to 3,5% by mass. It is known as HSFO (high-sulphur fuel oil). One way to comply with the maritime sulphur emission requirements is to replace (HSFO) with very low-sulphur fuels (VLSFO) with maximum sulphur content of 0,5% or ultra low-sulphur fuels (ULSFO) having a maximum sulphur content of 0,1%. VLSFO or ULSFO are distillate fuels: marine gas oil (MGO/DMA&DMZ), middle-distillate fuels, such as marine diesel oil (MDO/DMB&RMA10) or intermediate fuels/blends, such as residual fuel RMG180. Blends means the HSFOs are mixed/blended in different proportions with low-sulphur components (gasoil) to reduce the overall sulphur level to 0,5% by mass or below. The marine fuels ISO specifications are described in ISO 8217 fuel standard. ISO 8217:2017 (6th Edition) is a commercial standard covering both distillate marine fuels (DM) and residual marine fuels (RM). The fuel grade is given against a viscosity specification, e.g. RMG 180, where 180 denotes the maximum allowed kinematic viscosity of the fuel (in cSt = mm2/s): V15_2024 Page 17  Part 1 - Familiarisation with the Engine Room and Green technologies Current distillate marine fuels (DM) categories DMX DMA DMZ DMB DMC K. viscosity @ 40°C 1,4...5,5 2...6 3...6 2...11 < 14 Current residual marine fuels (RM) categories RMA RMB RMD RME RMG RMK K. viscosity @ 50°C 10 30 80 180 180 380 Table 1.2. Example of fuel grades in ISO 8217 Some of the shipowners may choose option (2): when the ship reaches a specified distance from an (ECA), it initiates the process of switching from burning HSFO (high sulfur fuel oil) to burning (ULSFO) low sulfur fuel oil. The duration of the switchover typically takes about one hour, depending on system component size and fuel burn rate. There are several implications of operating on ultra low-sulphur fuel. Some of the most common challenges are given below: 2) Use of HSFO and a Scrubber as EGCS (Exhaust Gas Cleaning System) If the vessel operates in SECAs, compliance can be achieved by using whatever fuel oil is available (such as cheap HSFO) and, in addition, a marine Exhaust Gas Cleaning System EGCS, often referred to as SCRUBBER, that removes the (SOx) and (PM) from the ship V15_2024 Page 18  Part 1 - Familiarisation with the Engine Room and Green technologies main engine(s), auxiliary engines and boiler’s exhaust gas. The power consumption when the EGCS system operates is typically between 1-2% of main engine power. Most of the international EGCS manufacturers (Wärtsilä, Alfa-Laval, Yara etc) and German manufacturers, such as Bilfinder SE (www.bilfinder.com) or SAACKE GmbH Bremen (https://www2.saacke.com), claim that the system is capable of removal of up 99 % (SOX) and up to 97% (PM) in exhaust gas. The location of the exhaust gas cleaning units EGCS is typically high up in the ship in or around the funnel area. The images below show the retrofit of a EGCS in case of a 15,000 tdw class tanker Levana (Carl Büttner GmbH). Two additional videos of such an installation can be watched in Moodle. Figure 1.12. Example of EGCS scrubber installation on a tanker4 Currently there are two main different EGCS scrubber systems: the WET SCRUBBER using either untreated seawater or treated freshwater as the scrubbing agent to remove (SOx) and particulate matter (PM) from exhaust gas and the DRY Scrubber, that uses dry chemicals as medium. Wet systems may be categorized as open loop, closed loop, or hybrid systems. As mentioned, they are all using water to filter out the Sulphur dioxide SO2. The main elements of an exhaust gas cleaning unit EGCS are: a) Jet scrubber (Venturi effect) b) Absorber After increase its velocity in the Venturi jet scrubber, the exhaust gas enters the dome/tower (called absorber) at the bottom and on the way to the top it comes in direct contact with the scrubbing medium in different stages. This happens either by a spraying nozzle in case of a liquid medium or in a packed tower with grids and granule in case of a solid medium. 4 Pictures from MT Levana (Photo courtesy of Mr. Sven Loske, Carl Büttner Shipmanagement GmbH) V15_2024 Page 19  Part 1 - Familiarisation with the Engine Room and Green technologies Figure 1.13. A typical scrubber and spraying nozzles inside the absorber The water gets into intimate contact with the exhaust gas and the Sulphur oxides in the exhaust reacts with the water forming sulphuric acid. The acid is neutralised by the natural alkalinity of the seawater (pH  8) or, alternatively by chemicals. Open-loop wet scrubber principle of operation The system takes in seawater for the scrubbing procedure. The seawater is pumped directly from the sea to a scrubber located in the engine exhaust uptake. The scrubber puts the water in direct contact with the exhaust gas. After the seawater has passed the scrubber the resulting water (now termed wash water) must be processed/ cleaned from heavy metals and solid particles/particulate matter before discharged into the sea again. This means that the wash water is not recirculated into the system. This system is capable of up to 98 % removal of SOx from the emissions. The pH of the wash water must be brought to a level that is acceptable for overboard discharge in most areas. This is achieved by diluting the wash water with a bypassed stream of seawater. NOTE! The pH of the washwater discharged into sea should be no less than 6,5. Positive aspects: (+) unlimited availability of seawater; (+) the system does not require additional storage space since the wash water is discharged directly; (+) no hazardous chemicals required; (+) The cheapest and simplest system in regard to installation and operating cost. Negative aspects: (-) wash water is a polluted water - there are some ports and areas where the discharge is prohibited due to the Sulphur content; (-) Operation in brackish or fresh water or in high water temperatures can inhibit scrubbing of SOx; (-) High seawater flow rate required (powerful pumps – large energy consumption). V15_2024 Page 20  Part 1 - Familiarisation with the Engine Room and Green technologies Figure 1.14. Open-loop wet SOx scrubber5 Closed-loop system principle of operation Closed-loop systems use fresh water to remove the SOx from the exhaust emissions. The fresh water is treated with – NaOH – Sodium hydroxide (i.e. caustic soda). As a result of the chemical reaction, the SOx is removed in form of sodium sulphate. Instead of discharging the wash water directly into the sea like the open loop system, in a closed loop system the water is recirculated. Before the water is recirculated through the scrubber, the water passes a tank where it is processed and cleaned = the process tank. Since the system does not discharge the wash water into the sea, more space is required for the storage. This also means higher costs. Nevertheless, the closed loop system also discharges small quantities of wash water from time to time. This is necessary to reduce the sodium sulphate concentration which creates crystals in the system limiting its effectiveness. A holding tank is installed for wash water that should be discharged but has to be stored during the passage of areas and ports where the discharge is limited. During the whole procedure of the closed loop system, freshwater gets lost due to evaporation, discharge and the treatment. Thus a certain amount has to be refilled into the system. Some advantages of the closed loop system include the following: (+) Large flexibility - the system can operate in all regions regardless of seawater alkalinity or temperature or local regulations; (+) Reduced FW flow required; (+) Effluent may be stored on board for whatever duration the tank volumes will permit. Some disadvantages of the closed loop system include the following: (-) Higher initial cost, as the system has more components than an open loop system; (-) The system requires a constant supply of sodium hydroxide solution, a hazardous substance requiring special handling, care, and additional running costs; (-) Large-size buffer tank required for the zero-discharge areas. 5 Picture from: Lloyds Register, Understanding exhaust gas treatment systems, Guidance for shipowners, page 18 V15_2024 Page 21  Part 1 - Familiarisation with the Engine Room and Green technologies Figure 1.15. Close-loop wet SOx scrubber6 Hybrid Scrubber systems A hybrid system is a combination of closed-loop systems and open-loop systems. It allows switching between one of these two systems when certain situations are required. 3) Convert ship to LNG operation Another “green” solution to reduce SOx is to switch from conventional heavy fuel oils to LNG (liquefied natural gas) that is being termed as the “fuel of the future”! The SOx is practically eliminated (zero sulphur oxide emissions), as LNG does not contain sulphur. A significant reduction in NOX and PM can also be achieved. The number of LNG-fuelled vessels (other than LNG carriers) is continuously growing: according to DNV 2019 statistics – 163 LNG-fuelled ships in operation and 83 on order and 112 are LNG ready (source: NOR-Shipping 2019). The major ship engine makers, such as Wärtsilä WinGD or MAN Diesel have already developed, converted to LNG powered and finally implemented the two engine concepts: Mono-fuel or lean-burn gas engines (engines capable of operating on gas fuel only) Dual-fuel DF engines. 6 Picture from: Lloyds Register, Understanding exhaust gas treatment systems, Guidance for shipowners, page 18 V15_2024 Page 22  Part 1 - Familiarisation with the Engine Room and Green technologies LNG as alternative fuel The Natural Gas NG is a mixture of gases, consisting mainly of METHANE CH4 (ca. 91%) with low concentrations of other hydrocarbons, such as ethane (ca.6%), propane (2%) and butane (ca. 1%). The exact gas composition depends on the source and the processing of the natural gas. LNG is the acronym for the natural gas in a liquid form. LNG chemical properties: The properties, characteristics and behaviour of LNG differ significantly from conventional marine fuels, such as HFO or distillate fuels, such as MGO: (1) LNG is odorless, colorless, non-toxic and non-corrosive. (2) The LNG average density (450 kg/m3) is ca. half the density of HFO (970 kg/m3) and slightly less than half the density of MDO (832 kg/m3). Because of this lower energy density per volume unit, it means roughly twice the LNG storage space is required compared to HFO/MDO for equivalent ship autonomy. (3) The calorific value Hu (LCV) of LNG is roughly 20% higher than HFO. If HFO has Hu ca. 40 (MJ/Kg) for LNG Hu is ca. 48 (MJ/Kg). (4) When cooled down at ca. -162°C at atmospheric pressure, the METHANE vapors boil and become liquid (LNG). Compare to NG, the LNG has a high density and a high energy content per unit volume: its volume reduces 600 times. In other words, a defined volume of LNG contains ca. 600 times more energy than the same volume of NG. To picture this property, imagine yourself shrinking a beach ball into a ping pong table tennis ball: (5) When in contact with water, the LNG floats on the surface, as it is much lighter than water and eventually warms and evaporates, as the water is warmer than LNG. There is no residue left over. This means in case of a spill on the water, no spill clean-up will be necessary. (6) In its liquid form, LNG does not burn: it is therefore not flammable and cannot ignite. It quickly evaporates as it warms. (7) However, in vapour phase, the LNG is highly flammable: the vapours may form explosive clouds and ignite when mixed with oxygen/air in a (5 % to 15 %) ratio combined with an ignition source of at least 500 °C. Some LNG advantages: For shipowners: (+) It is a feasible fuel alternative nowadays; (+) It is abundant & affordable: The LNG is ca. 25% cheaper than MDO and by mass production, the price can be even lower; (+) LNG can be used as fuel in all ECA (SECA/NECA) zones, so it complies with all actual regulations without the need of additional expensive catalysators; V15_2024 Page 23  Part 1 - Familiarisation with the Engine Room and Green technologies For population: (+) Less carcinogenic polycyclic aromatic compounds; For the environment is a clear benefit: (+) Is one of the cleanest burning fossil fuel; (+) SOx emissions are completely eliminated, as LNG has negligible sulphur content; (+) NOx emissions are reduced by 90 – 95% when used as fuel for engines and boilers; (+) 95% less ash (particulate matter PM); (+) LNG produces no visible smoke and causes no sludge deposits; (+) LNG reduces the noise level on board. Some major LNG disadvantages: (-) LNG infrastructure is not well developed; (-) LNG consists mainly of methane, that is ca. 25 times more harmful than CO2 and responsible for 25% - 30% of the global warming because methane traps more heat in the atmosphere than CO2. The problem with engines running on gas mode is the methane slip: ca 2% methane escapes into atmosphere, being unburned in combustion chamber; (-) Temperature of LNG during transport/bunkering is a main issue, as it has to be cooled down to a cryogenic temp. of ca. -162 °C; LNG is fluid between (-83 … -162 Celsius); (-) Special crew training required and higher maintenance costs; (-) LNG may not be feasible for some ship types (tramp ships with long voyage or high- powered ships that lack in space for the needed large LNG storage tanks); (-) Retrofitting for LNG is an unlikely option due to the lack of space for the LNG storage tanks & other equipment on board. The engine cubic capacity has also to be increased. Consequently, LNG demand in the sector will primarily be driven by new builds. LNG storage system The main function of a fuel gas system is to store the LNG (in liquid state), convert it to gas, and supply it to the engine under safe and stable conditions. Figure 1.16. Snapshot of a TTS bunkering system7 The LNG is supplied through a bunkering station which contains one LNG bunkering/filling line, one LNG vapor return line and one nitrogen supply/purging line. LNG circulates along vacuum insulated lines from the bunkering station to the cryogenic LNG fuel tank. The storage tank can be re-fueled through flexible connection hoses using one of the four different approaches: 7 Picture from: UNITEST DE-3D Simulator, Unitest Poland, Sept. 2020 V15_2024 Page 24  Part 1 - Familiarisation with the Engine Room and Green technologies (1) Ship–To–Ship Bunkering (STS): refuelling with a small LNG tanker/barge; (2) Mobile Tank Transfer (MT): through the exchange of the portable tank on-board; (3) Truck–To–Ship Bunkering (TTS): refuelling from a truck via pipeline (4) Terminal (Port)–To–Ship (TPS) via pipeline: refuelling via pipeline connecting to a refuelling station/Terminal. Figure 1.17. Basic methods of LNG Bunkering8 When the DF engines operate in gas mode, the gas is supplied from the LNG storage tank, installed on board above or under the deck, in a tank room. The LNG tank has to keep LNG at a very low temperature (-162°C) in liquid state and minimize the natural boil-off (BOG) in order to avoid an increase of pressure. To relieve this pressure in LNG tanks, (BOG) can be re-liquefied, used as fuel or burned in a gasification unit. The pressure inside the storage tank is 4- 6 bars. The cryogenic LNG tank is designed in accordance with IMO IGC Code tank classification and is of Type-C pressure vessel, in case of the low-pressure concept: it is a pressurised (p > 2 barg), cylindrically-shaped tank, double-wall vacuum insulated to minimise the LNG evaporation (BOG). The space between the two tanks, inner and outer, is filled with insulation material and kept under vacuum. Figure 1.18. Example of a LNG Storage Tank design9 A step-by-step demonstrator video, showing a TTS bunkering procedure is available in Moodle. The ferry ship has a diesel-electric propulsion plant, with 3 (three) DF medium-speed GenSets and 2 (two) azimuth thrusters. 8 Modified picture from International Fire Fighter Magazine, article LNG in your Port Part 2, https://iffmag.mdmpublishing.com 9 Picture from: Wärtsilä LNGPacTM, Product Leaflet, 2017 and Wärtsilä Technical Journal, Oct. 2015 V15_2024 Page 25  Part 1 - Familiarisation with the Engine Room and Green technologies Revision questions & exercises Topic 2: Question 1. MARPOL Annex VI Regulations refer to:  Water pollution from ships;  Air pollution from ships;  Garbage pollution from ships;  Oil pollution from ships;  Sewage from ships. Question 2. In 2018, IMO adopted an initial strategy to reduce greenhouse gas emissions (GHG) produced by ships, compared to 2008 baseline, by:  25% reduction in carbon intensity by 2025;  40% reduction in carbon intensity by 2030;  50% reduction in carbon intensity by 2050;  75% reduction in carbon intensity by 2050; Question 3. The release of substances from ships into the atmosphere or sea is called:  Smoke;  Air pollution from ships;  Emissions from ships;  Oil pollution from ships;  All the above. Question 4. Starting with 01.01.2020, the sulphur content in the fuel shall be not more than 0,5% (globally). This fuel is known as:  HSFO;  LSFO or VLSFO;  ULSFO; Question 5. What is the title of Regulation 14 of Marpol Annex VI?  Requirements for control;  Nitrogen oxides;  Sulphur oxides;  CO2 emissions; Question 6. Which is the exhaust gas ratio of recirculation in an EGR system:  10 – 30%;  30 – 40%;  40 – 60%;  60 – 80%; V15_2024 Page 26  Part 1 - Familiarisation with the Engine Room and Green technologies Question 7. Exhaust Gas Recirculation (EGR) technique is a method related to:  Gas after-treatment process;  Injection process;  Combustion process;  Supercharging process; Question 8. The primary pollutant most closely linked to the acid rain is:  Sulphur oxides SOx;  Nitrogen oxides NOx;  Particulate matter PM;  NOx and sun; Question 9. Consider an Exhaust Gas Recirculation (EGR) system. Which of the following statements are false?  Scavenge air has a higher specific heat capacity, when part of exhaust gases is recirculated as scavenge air;  Combustion process slows down, when part of exhaust gases is recirculated as scavenge air;  Exhaust gases must have same pressure as scav. air when entering the air receiver;  Exhaust gas temperature after the cylinder increases, due to an increased amount of scavenge air. Question 10. Which of the followings methods are considered possible candidates to reduce the NOx content:  SCR and EGR;  Exhaust scrubber and SCR;  Exhaust scrubber and EGR;  SCR, EGR and exhaust scrubber; Question 11. Selective Catalytic Reduction (SCR) technique is a method related to:  Gas after-treatment process;  Injection process;  Combustion process;  Supercharging process; Question 12. A SCR (Selective Catalytic Reduction) system is installed on a new ship. Identify which one from the following statements is true:  “Low pressure SCR” mounted after the turbine, in case of a slow-speed diesel engine;  “Low pressure SCR” mounted before the turbine, in case of a medium-speed diesel engine  “High pressure SCR” mounted before the turbine, in case of a slow-speed diesel engine.  “High pressure SCR” mounted after the turbine, in case of a slow-speed diesel engine; V15_2024 Page 27  Part 1 - Familiarisation with the Engine Room and Green technologies Question 13. Natural gas (NG) that is used by consumers is composed almost entirely of:  Methane;  LNG;  Propane;  Carbon Dioxide (CO2);  Ethane; Question 14. Identify which statement(s) about the LNG properties is TRUE:  LNG is not flammable and cannot ignite;  LNG is highly flammable and ignite when in contact with air;  LNG becomes a liquid at a cryogenic temperature of -162°C and atmospheric pressure;  LNG vapours are heavier than air and remain near the ground;  LNG is lighter than water and floats on the surface. Question 15. Identify which statement(s) about LNG storage tank is FALSE:  The LNG storage tank must be installed on board vessel above the deck only;  Despite a good tank insulation, heat slowly affects the tank, causing the LNG inside to evaporate and produce a substance known as boil-off gas (BOG);  The (BOG) can be released into atmosphere or re-liquefied, when possible;  LNG is commonly stored at atmospheric pressure in Type-C cylindrical tanks. V15_2024 Page 28  Learning Objectives: On successful completion of this topic, the students should be able to: Use generally accepted engineering terms; Know to describe the main marine power systems and their principle of operation; Produce schematic drawings of a complete marine power plant and explain the purpose of the various parts; Distinguish and know to explain the advantages and disadvantages of each marine power system.  Part 2 – Operating principles of marine power plants Based on marine propulsion power plant architecture, the merchant ships are propelled by various prime movers, such as: Reciprocating steam main engines; Steam turbines; Gas turbines; Diesel engines; Dual Fuel engines; Combined propulsion – CODOG, COGAG etc. Diesel Electric drive; Hybrid propulsion – (fuel cell technology + generator sets) WAPS-wind assisted propulsion systems– (sails and kites, Flettner rotors, Dynarig etc.) Only the first seven prime movers will be briefly presented in this course topic, because they are still the most common on board merchant or navy vessels. The first two uses the steam as the working fluid for powering the ship and represent the prime movers within a steam power plant. The third uses the exhaust gas expelled from an engine to power the ship. The fourth uses the good old Diesel engine for powering the ship and is still the most common choice for a prime mover. The fifth is the new in this course since 2021 - a diesel engine that can burn either diesel oil or fuel gas (methane). In addition, the sixth is a combination of the previous prime movers and the seventh represents a relatively new system suitable for cruise liners, ferry vessels or small offshore vessels fitted with a DP System (Dynamic Positioning System). 1. STEAM POWER PLANT Typically, the steam is produced by a marine boiler. The steam power plant uses the steam detention - expansion (taking place inside a prime mover - reciprocating steam main engine or a steam turbine) and converts it into work. Main elements: 1- Steam marine boiler 2- Prime mover (reciprocating steam engine or steam turbine) 3- Propeller shafting 4- Propeller 5- Main condenser, cooled by SW/FW 6- Air pump (usually driven by the main engine) or jet pump 7- Feed water filter tank 8- Boiler feed water pump 9- Feed water pre-heater SW = sea water FW LT = fresh water low temperature Figure 3.1. Diagram of a typical steam power plant V15_2024 Page 29  Part 2 – Operating principles of marine power plants The energy flow is: EP of steam → EK of steam → Mech. Work W Highly pressurised Steam expansion steam (p ) (p ; V ; T) The thermal efficiency of such plant is relatively low (20….40%). Principle of operation: The water inside the boiler (1) is warming up, the evaporation process begins and steam is produced. After leaving the boiler, the steam will expand inside the prime mover (2), acting the pistons or blades (depending on the prime mover type) and producing work, thus mechanical energy to drive the propeller (4) through the main shafting (3). The exhaust low pressure steam will pass to the main condenser (5) where through a heat exchange process the steam will condenses on the cold outer surfaces of the condenser and drops to the bottom of the condenser as water. This water, together with the air liberated from the steam when it condenses, is extracted by the air pump (6) and discharged through a feed water filter tank (7) to the feed water pumps (9). The air is released to the atmosphere. The filter tank extracts any grease or oil by chemical and mechanical filtering means. One or two feed pumps (8) draw the water from the tank (7) and pumps it up into the boiler. Before entering the boiler, the feed water is pre- heated (1st stage) in a feed water heater (9) (where the temperature will rise due to exhaust/used steam from auxiliaries). Finally, the resulting hotter water is pumped into the boiler (1), ready to be re-evaporated when the complete process is repeated. The auxiliary machineries supply with low-pressure exhaust steam many systems: - Accommodation spaces heating system; - Fuel tanks heating system; - Technical water system (hot water for kitchen etc.); - Ballast system - Kingston valves spray; - Deck machinery –steam driven on board tankers etc. The boiler has also an air and fuel auxiliary system. The air system supply the air required in the combustion process through a fan driven by electromotor, steam or gas turbine. The fuel system consists of fuel tanks, pipes, filters, fuel pump, heater and fuel spray nozzles. 1.1. Steam engines Reciprocating steam engines are rarely nowadays fitted on board ships as prime movers. However, they still exist on board old single hull tankers for auxiliary purposes: driving deck machinery (winches, capstans etc.) or driving the cargo or the strip pumps. First was built in 1807 and it has only 18 HP. The common type of reciprocating steam engine is the “triple expansion engine” which have three or more cylinders with 3 stages: HP, IP and LP; each successive cylinder is larger in diameter than the preceding one and works at a lower steam pressure. As a famous example, “Titanic” had 2 triple expansion main engines. V15_2024 Page 30  Part 2 – Operating principles of marine power plants Figure 3.2. Triple expansion steam propulsion engine on board Titanic Some advantages comparing with other propulsion systems: (+) Very short time needed for warming up and launch the main engine; (+) The slide valves are relatively simple to set up and easy to maintain. Main disadvantages: (-) Steam engine thermal efficiency: ca. 20% - the lowest; (-) Heavy construction with a large KG; (-) Large specific fuel-oil consumption (SFOC = ca. 400 - 600 g/kWh) – the highest; Construction and main elements of a simple main engine slide valve: A sketch of a typical steam reciprocating engine power plant is given at page 32. Figure 3.3. Piston slide valve, used on the reciprocating steam engine cylinders 1- cylinder 8- crosshead 2- piston 9- slide valve eccentric rod 3- steam inlet port 10- piston connecting rod 4- exhaust port (steam outlet) 11- slide valve connection rod 5- valve chest (steam distribution chamber) 12- crank 6- “D” shape piston slide valve 13- eccentric 7- piston rod 14- yoke 15- valve chest cover V15_2024 Page 31  Part 2 – Operating principles of marine power plants Principle of operation: The role of this simple slide valve is to admit and distribute steam. Steam from the boiler enters through a pipe into the valve chest (5). The valve chest cover (15) is fitted over the top and forms a steam tight box. The slide valve (6) which have a flat face at the bottom contacts is able to slide left and right over the valve port face (3) without steam leaking past the port face. (14) is a yoke which connects the valve with the eccentric rod (9). Element (9) exits the valve chest through a steam tight gland which allows the rod to slide but does not allow steam to escape (glands are generally made of several rings of graphite impregnated asbestos “rope”). A reciprocating engine works by steam pushing the piston (2) backwards and forwards along the cylinder (1), driving the crankshaft via a piston rod (7), connecting rod (10) and crank (12). On the crankshaft an eccentric (13) is fitted (is a disk mounted eccentrically around which a strap is fitted which allows the disk to rotate), the eccentricity is transmitted to the strap and by linking this by the eccentric rod (9), the displacement is transferred to the slide valve (6) again. An example is the steam icebreaker “STETTIN”, built in 1933 and located at moment in port of Hamburg. The main engine is a three-cylinder expansion steam engine running at n = 120 rpm. For more info visit: http://www.dampf-eisbrecher-stettin.de/ Below some photos taken during the SoSe 2023 excursion in Hamburg: V15_2024 Page 32  Part 2 – Operating principles of marine power plants 1.2. Steam turbines A steam turbine is suitable for high initial pressures and temperatures. It utilises the thermal energy of steam coming from boiler(s) and convert into mechanical energy to power the ship. Most of fast navy ships (destroyers) or the ones having high output (over 50.000 HP) are fitted with such propulsion system. In case of merchant ships, steam turbines are used for auxiliary power generation on board. There are two types of turbines: the impulse turbine and the reaction turbine. Because the first is perhaps more easily understood, we will confine to this type. Some advantages in comparison with the other power plants: (+) Extremely small wear of the turbine main elements and low maintenance; (+) Small overall dimensions, thus minimum space required in the E.R.; (+) Develop high rpm and output and tolerate low-quality fuels. Main disadvantages of the steam turbine consists of: (-) Relative high specific fuel consumption (SFOC = 230 -320 g/kWh); (-) Running at high speed (for example 5000 rpm) require a mechanical reduction gearing to reduce the rpm to a moderate speed (say 100 rpm); (-) Moderate effective thermal efficiency: 25.....30%; (-) When ship is going astern, the output decreases with approx. 30%. The most common steam turbine power plant is a cross-compound unit consisting of a high-pressure & speed turbine (HP) and a low-pressure & speed turbine (LP) which drives a single fixed-pitch propeller through reduction gears. In this cross-compound configuration, the two (HP) and (LP) turbines have separate shafts. Usually a complete astern turbine is fitted in the LP turbine casing. V15_2024 Page 33  Part 2 – Operating principles of marine power plants Figure 3.4. Typical high-pressure impulse turbine (HP)1 Figure 3.5. Steam turbine, source: MAN Diesel & Turbo Typical low-pressure turbine (LP) Construction and main elements: There are two categories of elements inside a steam turbine: 1. Fixed elements: the casing, the bedplate, the bearings, the diaphragms and nozzles; 2. Mobile elements: the curved wheel blades, the wheel rim (keyed securely to the shaft), the main shaft and the coupling devices. The specially designed nozzles (7) are mounted on the turbine casing and form the so-called STATOR, which transform the “potential” energy of the steam to velocity, or “kinetic” energy. The result is the steam will fall in pressure but leave the nozzle as a very high velocity jet. The small buckets or blades, mounted radially on the rim of a wheel on a shaft, form the ROTOR, which will rotate at high speed due to steam velocity imparted to the wheel and so drive the shaft. 1- Steam inlet 2- External packing gland 3- Bearing 4- Shaft 5- Inlet volute (radial channel) 6- Casing 7- Nozzle 8- Curved wheel blades 9- Exhaust steam outlet 10- Diaphragm Figure 3.6. Three stage (wheels) impulse turbine main elements 1 Figure 1 page 233 from Marine Engineering, SNAME V15_2024 Page 34  Part 2 – Operating principles of marine power plants Principle of operation: Steam enters through the steam inlet (1) and passes through a set of nozzles (7) in a division or diaphragm. The steam pressure falls by only a small amount and only a small proportion of the available velocity is developed in the first set of jets (process called expansion). These jets are directed on to the blades of the first wheel and cause it to rotate under the impulse of the steam striking the blades. The steam will then come out and enters the second set of nozzles. Again the steam pressure falls and in its place velocity is developed in the form of a second set of jets which strike the second wheel blades. The process will repeat depending on how many stages or wheels the turbine has. Note that the nozzles and blades are increased in size to accommodate the increased volume of steam, due to expansion. The blades are curved to suit the direction (angle) at which the jets strike them. Thus, they suit to one direction of rotation only. Separate blading, with the blades reversed, must be provided for running astern. Usually the astern turbine is on the same shaft (with separate steam connections and nozzles) and runs idly backwards when the vessel is going ahead. A sketch of a typical steam power plant with a tandem-compound unit is given on pp. 35. Tandem compound means the two turbines have a common shaft. Figure 3.7. Typical steam power plant with a tandem-compound unit V15_2024 Page 35  Part 2 – Operating principles of marine power plants 1.3. Turbo-generator system It is a WHRS (Waste Heat Recovery System). The unit is also known as the TG-Unit. The images below represent snapshots from the Unitest Simulator VER6. Principle of operation: A turbo-generator (TG) unit receives steam (superheated steam type) coming from a waste- heat boiler (1) fitted with a superheater. (1) ) The superheated steam enters a steam turbine (2) which is connected with an electrical generator (3) via a reduction gear. (2) (3) The generator (3), when connected to the main bus bar (4), will supply the ship with energy- electricity. To produce electricity, the TG must be first synchronised (same voltage, same frequency) with the grid of the main switchboard MSB. V15_2024 Page 36  Part 2 – Operating principles of marine power plants (4) ) The TG unit is operational only when the ship is underway and the waste-heat boiler is receiving exhaust gases from main engine(s). A sketch of a typical TG Unit is presented in the image below: Figure 3.8. Turbo-Generator schematic diagram 2. GAS TURBINE POWER PLANT In this case, the propulsion prime mover is a gas turbine. The marine gas turbine was derived from the gas turbine developed for aircraft applications (known as "jet engines”). To be “marinized”, materials were changed and a power turbine was incorporated. In marine applications, it is widely used on board Navy ships, fast RO/RO ships, fast Ferries and Cruise ships due to its high power-to-weight ratio and the ability to get underway quickly. Manufacturers: Rolls-Royce; Siemens AG, General Electric or MAN Turbomachinery. V15_2024 Page 37  Part 2 – Operating principles of marine power plants On modern merchant ships, a gas turbine is used for auxiliary power generation, as part of WHRS (Waste Heat Recovery System) and known as the PTG system or ST-PT system. Some advantages in comparison with the other power plants: (+) Proven very high power-to-weight ratio, compared to reciprocating engines; (+) Far less vibration than a reciprocating engine; (+) Large flexibility when locating them in a ship; (+) Simpler design and leads to high ship speed (more than 40 kn); (+) Low operating pressures and high operation speeds; (+) NOx emissions are low and SOx emissions negligible since higher grades of fuel are burnt. Also significant reduction of PM, CO and HC. Main disadvantages of the gas turbine consists of: (-) Poor efficiency at low-loads; For a better efficiency and compete with the diesel engine even at part loads, the gas turbine is combined with gas and steam systems, like COGES or COGAS; (-) Moderate specific fuel consumption (SFOC = 210-300 g/kWh); (-) More expensive than the others similar-sized engines; (-) Medium efficient (ca. 30-45% thermal efficiency) - lower than the thermal efficiency of diesel engines; (-) Little tolerance for low-quality fuels – use expensive high distillate fuel. Construction and main elements – A marine gas turbine consists of two parts: 1. A gas generator – provide gas at high pressure and temperature. Main elements: an air compressor, the combustion chamber(s) and a gas high-pressure turbine (HP). The HP turbine could be radial, axial, impulse or reaction type, single or multi - stage. 2. A power turbine (a LP turbine) – deliver useful work to propeller by expanding the gas. Both parts can be mounted on a common shaft or separately, in a twin-shaft configuration. a) Open Brayton cycle b) Closed Brayton cycle Figure 3.9. Diagram of a typical gas turbine power plant Source:Kurt Gramoll, http://www.ecourses.ou.edu V15_2024 Page 38  Part 2 – Operating principles of marine power plants Working principle of a gas turbine: The gas turbine converts chemical energy stored in the fuel into mechanical energy on the output shaft. The energy conversion takes place in two main stages: 1) First, the chemical energy is converted to thermal energy in the combustion process where air and fuel is mixed and ignited. The ambient fresh air is compressed at high pressure inside a multi-stage axial compressor (from atmospheric pressure to the working pressure of ca. 10 – 30 bar) and sends through a heater into the combustion chambers. Here fuel is injected through nozzles (distillate fuel, such as marine gas oil MGO). 2) Then, this thermal energy is converted into mechanical energy when the hot gasses expand and powers the HP turbine blades. Inside the combustion chambers, the resulting gas mixture has high pressure and temperature. The gas potential energy is transformed inside the HP gas turbine into kinetic energy. Thus, at the outlet, the gas having very high speed and temperature will expand in a power turbine (a LP turbine) after passing through an empty duct with no mechanical parts inside. The wheel blades of the power turbine will rotate at high speed under the gas jet velocity and drive the main shaft through a reduction gear. As mentioned, the power LP turbine can run on the same shaft with the gas generator or independently of the gas generator, thanks to a second shaft. When leaving the power LP turbine, the flue gases are directed to the funnel. If the exhaust gas enters first into a heater to pre-heat the compressed air, the gas turbine cycle is called a “recuperator” (Closed Brayton cycle with recovery of waste heat). Thermodynamic cycle of a gas turbine: The ideal simple gas turbine cycle is also known as the Brayton cycle, and is often used as a reference and/or comparison model when evaluating a real-life gas turbine cycle. When describing an ideal simple GT cycle, the following process are assumed: (1–2): Isentropic compression (i.e. at constant entropy) (2–3): Isobaric heat addition (i.e. at constant pressure) (3–4): Isentropic expansion (4–1): Isobaric heat rejection/removal. V15_2024 Page 39  Part 2 – Operating principles of marine power plants The main differences between the Brayton cycle and the real gas turbine cycle is the losses that occurs during the process: - Air friction losses in the compressor, the combustion chamber and the turbine sections; - Thermal losses when heat is transferring to the surrounding environment, mainly from the combustion chamber and the turbine side; - Combustion losses due to incomplete combustion of the added fuel; - Mechanical losses in all moving parts like bearings and auxiliary equipment - Pressure losses in all ducts. 3. COMBINED POWER PLANT The combined propulsion systems offer the possibility to combine different prime movers (diesel engines, gas-and steam turbines and electric-motors) and link them with various propulsors, such as CPP, FPP or Waterjet. These systems are very popular on board patrol boats and naval ships due to their ability to operate in extreme operating conditions. Examples of these systems fitted on board navy ships are: CODOG (COmbined Diesel Or Gas turbine), COGAS (COmbined Gas turbine And Steam turbine), COGOG, COGAG etc. In case of some commercial ships and also the new frigates F125- or F126-type, the hybrid propulsion becomes nowadays very common. Examples of hybrid propulsion are CODLAD, CODLOG etc. There are three important features of this type of propulsion: 1. There are two engines (prime movers): - The main one, operating at economical speeds, is called the cruise engine - The second one, operating under request, is called the boost engine. 2. The interconnectivity between the two engines: 1. Cruise engine OR Boost engine, which means they cannot operate simultaneously 2. Cruise engine AND boost engine, operating individually and simultaneously. 3. The prime movers may be of: - Different type (Diesel engine, gas turbine or steam turbine). Ex. CODOG, COGAS - Same type. Ex. COGOG, COGAG Figure 3.10. Typical CODOG configuration, source: www.wikipedia.org If we consider for example the CODOG configuration (Figure 3.10.), the cruise engine is a Diesel Engine and the boost engine is a gas turbine. The interconnectivity is of “OR” type which means the diesel engine cannot run simultaneously with the gas turbine. The “OR” configuration has a simpler gearing (+) but is less flexible (-) and less capital efficient (a very V15_2024 Page 40  Part 2 – Operating principles of marine power plants high fuel consumption at high speeds) (-). In case of the “AND” configuration the reduction gear is a weakness, being a very complex reduction gear (-). The separate operation is achieved through clutches, which are fitted between the two prime movers and the common transmission gearbox. In addition, the system has a reduction gear for the turbine to reduce the rpm of the turbine. As mentioned, for merchant ships, a hybrid propulsion configuration is more attractive: CODLAG (COmbined Diesel eLectric And Gas turbine) or CODELAG, CODLAD (COmbined Diesel-eLectric And Diesel engine), CODLOD (COmbined Diesel-eLectric Or Diesel engine) etc. These hybrid propulsion systems can be differentiated between the configurations above, with the mechanic power (diesel engines) and the electric power (E-motors) working together in the propulsion train. Examples are CODLAD, were the diesel engines and the E-motors work in parallel “AND” on the propeller or CODLOD where either the diesel engine “OR” the E-machines are used. In all cases, the systems have “clutches”. 4. DIESEL-ELECTRIC POWER PLANT For ships propelled by a conventional mechanical-diesel propulsion, the efficiency decreases noticeably when operate outside the nominal operation range (when the ship’s speed varies a lot). A solution would be to replace the main diesel propulsion engine with E-motors and split the power production into several small gensets. In other words, this type of propulsion is suitable for modern passenger ships, ferries or offshore vessels fitted with DP (Dynamic Positioning) system. Definition of a DP system “keeps the vessel in position by means of active thrust” Example of ships fitted with a DP system: - Supply vessels - Pipe/cable laying vessels - Survey vessels - Offshore vessels - Shuttle tankers - Vessels assisting divers etc. Advantages of DP system over other propulsion systems: - Huge ship manoeuvrability - Operates at any depth (anchor-free) - Fast setting-up and fast reaction to any environmental changes - Flexible power supply in different operational states - Low level of maintenance costs Main characteristics of power supply required in a typical DP system: - Must satisfy low and high power demands - Must enable the ship to react fast to any environment changes and to supply many “external consumers” i.e. thrust units. V15_2024 Page 41  Part 2 – Operating principles of marine power plants Advantages of Diesel-electric propulsion: (+) Reduced vibrations and lower propulsion noise (E-motors are far more silent than diesel engines) (+) Lower operational and maintenance costs (+) More flexibility in location of gensets and propulsors: the propulsors are supplied with electric power through cables, so they do not need to be adjacent to the diesel (+) Reduction of the machinery space, as diesel-electric propulsion plants take less space compared to a diesel mechanical plant (+) Improved ship maneuverability and station-keeping ability (+) Higher reliability, due to multiple engine redundancy (+) Reduced fuel consumption and emissions, due to possibility to optimize the loading of Diesel engines. Figure 3.11. Different location of A/E’s on the LNG DE-3D Unitest Simulator Disadvantages of Diesel-electric propulsion: (-) Higher initial costs of these plants in relation to conventional mech. Diesel propulsion (more components); (-) Hull shape changes are required to use the Azipod or Azimuth devices; (-) Increased risk of human safety in the use of electric devices, since electric systems have high voltage and produce disastrous consequences; (-) Crew training required in preparing to manage such complex systems; (-) Most of the Gensets use small 4-stroke engines with lower energy efficiency than a larger 2-stroke engine; (-) The Diesel-electric propulsion has a lower efficiency due to losses in conversion from- and to-electric energy (such as losses in cables and switches. This lead to a lower fuel economy of ca. 5%. Main elements of a diesel-electric propulsion: In diesel-electric systems, multiple diesel auxiliary engines called Gensets (each driving an electric generator), produce the electric power for propellers as well as other electrical loads on the ship. V15_2024 Page 42  Part 2 – Operating principles of marine power plants Principle of operation: - At first, there are two separated sections in the HTS (High Tension Switchboard) fed with 6kV, 11kV or another voltage at 60 Hz. The voltage level varies with the installed power, typically 11 kV for installed power above 20 MW. The HTS’s are supplied by a number of GenSets. Usually 3 to 8 A/E’s are fitted on board ships in different compartments to give redundancy to the system. Figure 3.12. Typical diagram of a diesel-electric configuration - Between the separate HTS (called Bus Bar 1 and Bus Bar 2) there is one or two bus bar switches (tie breakers). They have the role to connect the 2 HTS in case the whole power produced by the DG’s is required. As mentioned, the separate sections Bus Bar 1 and Bus Bar 2 will ensure redundancy. Depending on electrical demand, not all GenSets have to operate at all times. This means that, when a higher power is required to drive the active thrusts, one can switch ON an additional A/E which was previously on Stand By mode. - The unit which control automatically the whole power situation is the PMS (Power Management System). - From the HTS, a number of consumers is supplied with power. The consumers for propulsion & thruster drives are called “Primary consumers”: ST (stern thrusters), BT (bow thrusters), AZ (azimuth devices), FP (fire pumps), AC (air compressors), E- motors etc. - Through transformers, the voltage is transformed to 440V along the Main Tension Switchboard (MTS). Here, similar with HTS, there are two Bus bars separated through 1 or 2 tie breakers. The MTS supplies with power the “Secondary Consumers” like: pumps, lightening, motors etc. V15_2024 Page 43  Part 2 – Operating principles of marine power plants - Last, there is another Low Tension Switchboard (LTS) which fed with 230 V the low- voltage network for auxiliaries and hotel consumers, electrical outlets (sockets) for example. Between the MTS and LTS there are transformers 440 V/230 V. - This type of ships are usually propelled by two independent shaftlines instead of a “classic mechanical diesel engine plant”. There are two synchronous propulsion motors coupled with variable speed CPP’s (controllable pitch propellers). The electric motors connected to the propellers are energized by the electric power produced by the GenSets. Revision questions & exercises Topic 3: Question 1. Which propulsion prime mover has the best specific fuel consumption SFOC?  Diesel-electric drive;  Slow-speed Diesel engine;  Gas turbine;  Steam turbine. Question 2. What type of propulsive prime movers tolerate low-quality fuels, like Heavy Fuel Oil (HFO)? (multiple correct answers possible)  Diesel engines;  Gas turbines;  Steam turbines;  Diesel-electric drives; Question 3. What is the typical specific fuel oil consumption in case of a propulsive gas turbine (power turbine)?  SFOC = 160 … 230 g/kWh;  SFOC = 210 … 300 g/kWh;  SFOC = 230 … 320 g/kWh;  SFOC = 400... 500 g/kWh; Question 4. What drives the air compressor in a gas turbine?  The high-pressure turbine which is connected to a common shaft;  The low-pressure turbine which is connected to a common shaft;  A gas generator unit;  An electric motor; Question 5. What is the voltage on the High-Tension Switchboard in case of a diesel-electric propulsion plant?  440 V at 60 Hz;  more than 6000 V at 60 Hz;  230 V at 60 Hz; V15_2024 Page 44  Part 2 – Operating principles of marine power plants Question 6. Assign the image below with the correct combined/hybrid propulsion plant:  CODOG  CODLOG  CODAD  CODLAD  COGOG  CODLOD Question 7. Steam turbine blades do not change direction of steam coming from nozzle: True; False; Depends on the steam temperature; Question 8. In case of a steam turbine, the steam leaves the nozzle at a: High pressure and a low velocity; High pressure and a high velocity; Low pressure and a low velocity; Low pressure and a high velocity; Question 9. Assign the correct combined propulsion plant with the image below:  CODLOG  CODAD  CODLAD  COGAG  CODOG V15_2024 Page 45  Learning Objectives: On successful completion of this topic, the students should be able to: Use generally accepted engineering terms to describe a diesel engine fixed- or mobile part; Know to classify the internal combustion engines (ICE); Describe the advantages and disadvantages of a diesel mechanic power plant over the other marine power plants; Explain the role of each fixed- or mobile-part of a diesel engine; Distinguish the differences between a cylinder head and a cylinder cover.  Part 2 – Operating principles of marine power plants 1. DIESEL MECHANIC POWER PLANT Today, diesel propelled machinery is the principal means of marine propulsion. Diesel engines has also advantages and disadvantages comparing with the previous propulsion systems: Advantages: (+) Best fuel efficiency–best thermal efficiency (ca. 50%) (low-speed type); (+) Reasonable specific fuel consumption (SFOC = 160-230 g/kWh for HFO with lower calorific value Hu = LCV = 40,5 MJ/kg); (+) Relative short time in preparing the main engine for departure; (+) Relative large fuel autonomy; Disadvantages: (-) Main engine high construction price; (-) Main engine is relatively large in size and heavy; (-) Noisy in daily practice (especially the medium-speed engines) and produces vibrations in the ship’s hull; (-) Relative high maintenance costs (especially the medium-speed engines) (-) Produce CO2 emissions as well as NOx, SOx and particulate matter PM. The internal combustion engines (ICE) can be classified according to various criteria, the most important being presented below: The ignition procedure: The nature of functional engine cycle: 1. Compression ignition (CI) engines; 1. Two-stroke engines; 2. Spark plug ignition (SI) engines. 2. Four-stroke engines. The cylinder configuration solution: The speed (rpm): 1. In-line; 1. Slow-speed: 55 – 200 rpm; 2. In “V”ee form (two cylinders blocks); 2. Medium-speed: 200 – 1000 rpm; 3. In “W” form (three cylinder blocks); 3. High-speed: over 1000 rpm. 4. In “H” form (two engines); 5. In “X” form (four cylinder blocks) etc. The way the air is supplied into cylinder: The destination: 1. Natural admission – at atm. pressure; 1. Engines for terrestrial transportation; 2. Forced admission of the supplying air (boost 2. Engines for aerial transportation; pressure) = scavenge or supercharged 3. Marine Engines: engines: – Auxiliary engines (Diesel Generators); 2.1. Lower supercharging 1,1 – 1,3 atm. – Main engines – for ship propulsion; 2.2. Medium supercharging 1,3 – 1,8 atm. 2.3. High supercharging p > 2 atm. Beside the above criteria, there are many others ways of classifying the internal combustion engines: the piston acting procedure or medium-speed; aggregation phase of the fuel; cooling agent type; engine effective output; cylinder diameter etc. Most merchant ships are also fitted with medium or high-speed diesel engines (GenSets) to drive generator sets for auxiliary power purposes. Additionally, all merchant ships have an emergency generator (EG) as required by SOLAS. V15_2024 Page 46  Part 2 – Operating principles of marine power plants 2. Diesel engine fundamentals 2.1. Typical cylinder components Let’s analyse a cylinder and its various components in case of a medium- and slow-speed engine: Figure 4.1. Sketch of main cylinder components Figure 4.2. Sketch of an old (medium-speed engine) ported cylinder (slow-speed) The diameter of the cylinder bore, is denoted by D; When the piston is at the limit of its outward travel – it is at top dead centre (TDC); Any further rotation will cause the piston to move down. When the piston is at its inward most position – it is at bottom dead centre (BDC); Any further engine rotation will cause the piston to move upward again. The vertical distance between TDC and BDC is called the stroke, denoted by s; The piston displacement is called swept volume and is denoted by Vh :    D2 Vh =  (bore) 2  ( stroke) = s 4 4 The formula is valid for swept volume of any single cylinder. For the entire engine with “z” cylinders, the engine total swept volume is then:   D2 VH = Vh  z = sz 4 The space between piston at TDC and cylinder head is the clearance or compression volume representing the combustion chamber volume, denoted by VC. The sum of combustion chamber volume and piston displacement represent the total volume of the cylinder, denoted by Vt : Vt = Vh + VC The cylinder head seals the top of the cylinder and has openings for intake (inlet) valve, exhaust valve and fuel injector. V15_2024 Page 47  Part 2 – Operating principles of marine power plants Some cylinders may be constructed with inlet and exhaust ports (instead of valves) – it is called ported cylinder: The ports are located at different levels – this way exhaust port uncovers first and the inlet port last and closing in reverse order. The fuel injector(s) supply an energy source to the engine providing a metered amount of spray fuel to the cylinder at the appropriate time. In case of medium-speed engines, the injector is placed centrally (for 4 valves) and off-centre – on one side (in case of 2 valves). On slow-speed engines with a central exhaust valve, 2 to 3 injectors are placed radially. 2.2. Engine nomenclature Let’s analyse now the construction parts of a marine diesel engine: 1. BEDPLATE (TIEBOLTS) – represents the foundation of the engine. It must have enough strength because everything will be built from it – the fixed and moving parts of the engine. The bedplate is attached to the ship’s structure by its lower flanges (holding down bolts); The bedplate will support the crankshaft directly through the main bearings support; The lubricating oil for the engine is often collected within the lower part of the bedplate = crankcase. But for the marine-type construction, the cooling lube oil is stored in a separate area (double-bottom drain tank) because the bedplate is very shallow; It consists of a deep longitudinal box structure with stiffening members and webs for additional rigidity; Figure 4.3. Different views of an engine bedplate1 1 Pictures taken from www.marinediesels.co.uk and Wärtsilä