Lecture 4: Marine Internal Combustion Engines PDF

Rudolf Diesel cooperated with Sulzer to construct the first Sulzer diesel engine in 1898 Marine Internal Combustion Engines Lecture 4: Components and features of slow speed marine ICE...

Rudolf Diesel cooperated with Sulzer to construct the first Sulzer diesel engine in 1898 Marine Internal Combustion Engines Lecture 4: Components and features of slow speed marine ICE  Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead All tankers, bulk carriers and large container ships use the bulky low-speed two-stroke crosshead engine on heavy fuel oil for propulsion. These are the immensely large and also remarkably high (due to the crosshead construction) diesel engines They can get as high as 14 meters at a length of 30 meters and weighing 2300 tons.  Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Lubricating oil pipe (sheathed pipe) The curved lines show the lubricating-oil supply High pressure ducting for the operation of the exhaust valves. lubricating oil pipe The exhaust valves 1 with valve casing that exceeds two meters.  Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Lubricating oil pipe (sheathed pipe) The lubricating oil pipe is a two layer pipe For example: Imagine the pipes of home gas heaters shown in the next photos Braided Sheathings Notice the braidings surrounding the pipes Sheathed = covered Sheathed pipe = a pipe that is covered by another layer of metal  Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead But, why sheathing? With what do we sheath? In the event of leakage from the high pressure (HP) pipe connecting the valve lube oil pump and cylinder, a fire could result from the hydraulic oil spraying on the hot exhaust manifold. To safeguard against such an incident, the HP pipe is surrounded by a braided steel pipe and there is a narrow gap between the HP pipe and the braided pipe. Sheathing is a safety measure  Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead How do we detect failure in HP (sheathed) pipe? 1. Defective operation of the exhaust valve with consequent poor cylinder performance which would be brought to the attention of the engineer through the exhaust temperature. 2. Leaking oil then drains from the gap between the HP and braided pipes, via small holes in the actuator pump body, into the cam box. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Looks like a cage Exhaust valve Keep this logo in your mind Four studs with hydraulically-tightened Cylinder nuts cover Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Valve cage Cylinder cover A valve cage is especially designed for single exhaust valve located in the center of the cylinder cover detachable valve seat Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead studs with hydraulically-tightened nuts Valve cage The valve is connected to the cover by means of four or more studs and hydraulically-tightened nuts. Valve cages are made from cast iron as they are not subject to any excessive mechanical or thermal loading, although a detachable seat is employed. Why detachable seat?! Cylinder cover Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Valve cage studs with hydraulically-tightened nuts Cylinder cover Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Detachable seat A detachable seat is made from a material such as molybdenum steel which is able to resist the thermal loading and corrosive environment and, being detachable, can be machined with relative ease Detachable following removal from the cage. valve seat Cylinder cover Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Detachable seat Cylinder cover detachable valve seat Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Detachable seat (3D) O-ring = sealing ring Detachable valve seat = a corrugated hollow cylinder Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Detachable seat The actual seat area generally incorporates an insert, of Stellite or similar material, which improves the operating life of the unit due to its wear and damage resistance. Seat Valve Stellite is a hard alloy that, Seat although expensive, has very good corrosion and damage Stellite: A solid solution based on cobalt resistance at high temperatures. Valve 50% with other hard alloys such as chromium-tungsten Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve cooling The valve cage is as part of the engine system Valve generally passes to the exhaust valve body from the cylinder cover by means of. However, in some cases, there is a direct connection between the water space in the cylinder cover and the seat region of the valve cage. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve cooling Valve generally passes to the exhaust valve body from the cylinder cover by means of. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve seal/bush A bronze bush (hatched in the next figure) fitted in the valve body acts as a guide for the valve spindle. The seal prevents wear of the spindle or leakage from the air cylinder Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Nimonic: a family of nickel-based high-temperature low creep super alloys. It consist of more than 50% nickel and 20% chromium with additives such as titanium and aluminium. Exhaust valve spindle Nimonic is used extensively for valve spindles due to its wear and corrosion resistance at elevated temperatures. It is an expensive nickel-based alloy that has good corrosion and wear resistance at high temperatures. Engine builders tend to use nimonic for the entire valve due to the high loading on the valves. Material selection is important to ensure optimum operating life when burning low quality residual fuels with high levels of Sulphur, vanadium and other damaging chemicals. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Inconel 625 is a nickel-based superalloy: High Strength, Excellent Corrosion Resistance, Good Fabrication Properties, Wide Temperature Range Exhaust valve spindle Cermet: is a composite material consisting of ceramic (cer) and metallic (met) materials. The underside of the valve disc, the part facing into the combustion chamber, is sometimes coated with a material such as Inconel 625 to reduce the rate of hot corrosion. Valve stems are coated with a layer of chrome or cermet to reduce wear on the part that passes through the stem bushing. Compared to chrome, Cermet has no environmental problems and has greater wear resistance. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve spindle Valves may generally be classified as one of the following types: 1. Stellite facing on the seat and chrome/cermet coating of stem for wear resistance. 2. A Nimonic head and no insert on the seat and chrome/cermet coating of stem for wear resistance.. 3. A one piece Nimonic valve with no Stellite insert. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve rotator/spinner/rotating mechanism Spinners or valve rotators prevent valve tilting, uneven forces, overheating, and accumulation of exhaust solidified slags on the sealing faces of the valve as follows: 1. Spinners induce a light grinding effect at the sealing faces of the seat and valve disc, which removes the highly corrosive vanadium pentoxide slag. This prevents tilting as it ensures an even sealing face Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve rotator/spinner/rotating mechanism 2. Spinners redistribute heat and prevent localized overheating of the valve disc. This is achieved by turning the disc, at each engine cycle, so that a new section of the disc receives the overheating. (regulation of uneven thermal stresses) 3. As the valve rotates, the uneven combustion force exerted on the valve seat is distributed more evenly. This helps to prevent the valve from tilting in any particular direction and prevent localized wear and tear. 4. Spinning the valve aids in reducing tilting caused by valve guide (seal) wear Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Sheathed Keep this logo in pipe Exhaust valve hydraulic your mind 1- Hydraulic cylinder cylinder 2- Air cylinder a piston on the top of the 3- Valve housing valve stem/spindle, operates in a hydraulic cylinder connected to an actuator/oil pump unit by means of a high pressure sheathed Stem/spindle pipe. Actuator/oil Pump Piston Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve A pair of piston rings provides sealing in the open bottomed hydraulic cylinder. An oil bleed valve, located at the top of the hydraulic cylinder, allows a controlled amount of oil to pass to the air cylinder, located immediately below the hydraulic cylinder, to provide lubrication. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Sheathed pipe Exhaust valve actuator/oil pump Actuator/oil Pump Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve actuator/oil Sheathed pump pipe The camshaft-driven actuator pump delivers oil to the valve cylinder on the upwards stroke of its piston causing the valve to open, so that on the downwards stroke oil returns to the actuator pump cylinder. A relief valve is located at the top of the pump cylinder A puncture valve on the actuator pump body may be actuated to Actuator/oil release some pressure from the Pump system. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve actuator/oil pump A make-up oil connection to the pump body to ensure that there is always a full oil charge in the system. The make-up connection is located just above the top of the pump piston when it is at the bottom of its stroke, and oil is supplied under pressure from the cam-box lubrication system. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve air spring cylinder Air spring cylinder provide some positive force to ensure the valve closes after the hydraulic opening force is removed. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve air spring cylinder A piston is fitted to the valve stem below the hydraulic cylinder and this piston reciprocates in a cylinder, compressing the air in the cylinder when the valve opens. This compressed air acts on the piston to close the valve when the opening hydraulic force is removed. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve air spring cylinder Air leakage from the cylinder is made-up from an air supply system maintained at a pressure of 5 bar a non-return valve in the supply line prevents backflow during opening of the valve. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve air spring cylinder Lubrication of the cylinder wall is provided by controlled leakage from the oil bleed valve located in the hydraulic cylinder. Sealing air to the gland contains oil mist to limit wear at the seal and valve stem. Oil mist: compressed air that contains oil particles of less than 10 μm in size Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve air spring cylinder A Tell-tale is a device that provides a visual indication of the air pressure within the cylinder to aid air cylinder pressure monitoring. Tell-tales can be glass tubes filled with liquid that indicates the air pressure. Alternatively, they can be electronic indicators that provide a digital readout or pressure gauges that are more accurate than liquid types Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve air spring cylinder Check rod is used to enable the engineer to check that the valve is lifting and rotating. At the top of the casing is a spring-loaded check rod which passes through a bush and has contact with a groove in the top of the air piston. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve air spring cylinder As the piston reaches the top of its stroke, it causes the check rod to lift, indicating that the valve is closing. The action of valve rotation produces further movement of the check rod, indicating that the valve is rotating as it closes. Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Exhaust valve detailed components: Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead Low speed, 2-str, crosshead turbocharged Engine Low-speed diesel engines 1500 to 100,000 kW shaft power, fuel H.F.O., two-stroke with crosshead 8 Low speed, 2-str, crosshead turbocharged Engine 8 is above 9, why? 9