MEC 756 Power Plant Engines - Lecture Notes (PDF)

1 MEC 756 CHAPTER POWER PLANT ENGINES 2 Lecture Notes: Faculty of Mechanical Engineering Universiti Teknologi MARA, RECIPROCATING 40450, Shah Alam, Selangor Prepared By:...

1 MEC 756 CHAPTER POWER PLANT ENGINES 2 Lecture Notes: Faculty of Mechanical Engineering Universiti Teknologi MARA, RECIPROCATING 40450, Shah Alam, Selangor Prepared By: INTERNAL Idris Saad, Ph.D COMBUSTION ENGINES Update: Oct 2020 Part 4 For students EM 703  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines Outline Learning Objectives: Explain the Purpose and Fundamentals of Compression-Ignition (CI) Engines Identify and Describe the Key Components of a Compression-Ignition Engine Illustrate and Analyze the Diesel Cycle Derive and Calculate the Thermal Efficiency of the Diesel Cycle Apply Knowledge of the Diesel Cycle to Real-World Engineering Applications Key Points: 1. Introduction to Compression-Ignition (CI) Engines 2. Basic Components of a Compression-Ignition Engine 3. Four-Stroke Compression-Ignition Engine Operation 4. Two-Stroke Compression-Ignition Engine Operation 5. Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 6. P-V and T-s Diagram 7. Work, heat, and efficiency calculations MEC 756 – POWER PLANT ENGINES 2  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.1 – Introduction to Compression-Ignition (CI) Engines 2.4.1.1 – Purpose of CI Engines Definition and Application CI engines, commonly known as diesel engines, are widely used in heavy-duty vehicles (trucks, buses), industrial equipment, marine vessels, and power generation due to their high efficiency and durability. They rely on compression to ignite fuel, unlike spark-ignition (SI) engines. Key Features High thermal efficiency and fuel economy. Designed for high torque output at low engine speeds. Advantages Durability: CI engines are built to withstand higher pressures. Fuel Type: Can use less refined fuels (diesel), which are typically more energy-dense. MEC 756 – POWER PLANT ENGINES 3  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.1 – Introduction to Compression-Ignition (CI) Engines 2.4.1.2 – Combustion Fundamentals in CI Engines Ignition Process Air is compressed in the cylinder to a high pressure and temperature. Fuel is injected into the cylinder, where it spontaneously ignites due to the heat of compressed air (no spark plug). Combustion Phases Ignition Delay: Time between fuel injection and the start of combustion. Rapid Combustion: Large portion of fuel burns, producing peak pressure. Controlled Combustion: Fuel injection continues; combustion is moderated. Late Combustion: Remaining fuel burns as pressure decreases. Emissions Profile Higher NOx and particulate matter (PM) emissions compared to SI engines. Lower CO and hydrocarbon (HC) emissions. MEC 756 – POWER PLANT ENGINES 4  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.1 – Introduction to Compression-Ignition (CI) Engines 2.4.1.2 – Combustion Fundamentals in CI Engines Diesel Fuel: Overview and Key Characteristics 3. Types of Diesel Fuel 1. Definition Petroleum Diesel: Diesel fuel is a hydrocarbon-based liquid Derived from crude oil through fractional fuel derived from petroleum or biomass, distillation. designed for use in compression-ignition Most common type of diesel fuel. (CI) engines. Biodiesel: It is less volatile than gasoline and ignites Produced from renewable sources (e.g., vegetable due to high compression, not a spark. oils, animal fats). Designated as B100 (pure biodiesel) or blends like 2. Chemical Composition B20 (20% biodiesel, 80% petroleum diesel). Primarily composed of alkanes (paraffins), Synthetic Diesel (GTL/FT Diesel): cycloalkanes (naphthenes), and aromatics. Produced from natural gas or biomass using Carbon chain length typically ranges from C10 to Fischer-Tropsch synthesis. C22. Offers cleaner combustion and lower emissions. Biodiesel alternatives are derived from vegetable oils or animal fats. MEC 756 – POWER PLANT ENGINES 5  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.1 – Introduction to Compression-Ignition (CI) Engines 2.4.1.2 – Combustion Fundamentals in CI Engines 3. Typical Cetane Numbers Cetane Number: Overview and Key Points Diesel fuels typically have a cetane number between 1. Definition 40 and 55. The cetane number (CN) is a measure of the Petroleum diesel: ~40–50 ignition quality of diesel fuel. Biodiesel: ~50–65 It represents the fuel’s ability to ignite quickly after Synthetic diesel (Fischer-Tropsch): Can injection into the combustion chamber. exceed 70 4. Effects of Cetane Number on Engine Performance 2. Scale and Reference Fuels Low CN Fuel: The cetane scale ranges from 0 to 100, based on two Increases ignition delay, causing rough operation reference fuels: and high emissions. Cetane (n-hexadecane): CN = 100 (ignites May lead to incomplete combustion. easily). High CN Fuel: α-Methyl Naphthalene: CN = 0 (very poor ignition Reduces ignition delay, resulting in smoother and quality). quieter engine operation. A fuel’s cetane number is determined by its ignition Enhances cold starting performance. performance relative to a blend of these references. MEC 756 – POWER PLANT ENGINES 6  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.1 – Introduction to Compression-Ignition (CI) Engines 2.4.1.3 – Comparison with Spark-Ignition (SI) Engines Aspect CI Engines SI Engines Ignition Method Compression-based (auto-ignition) Spark plug-initiated Fuel Type Diesel Gasoline Fuel Efficiency Higher due to lean combustion Lower Power Output Higher torque at low speeds Higher power at high speeds Thermal Higher Lower Efficiency Emissions Higher NOx and PM Higher CO and HC Operating Costs Generally lower (better fuel economy) Higher fuel cost per mile Less frequent but potentially costlier Maintenance More frequent, lower-cost repairs repairs MEC 756 – POWER PLANT ENGINES 7  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.1 – Basic Components of Diesel Table: Basic Components of Diesel and SI Engines Component Diesel Engine SI Engine Houses cylinders for high-pressure Designed for lower pressures. Often made of Cylinder Block combustion. Made of cast iron or reinforced lighter aluminum alloys. aluminum for strength. Contains fuel injectors, valves, and Contains spark plugs, valves, and Cylinder Head intake/exhaust ports. No spark plugs. intake/exhaust ports. Heavier, robust design to withstand higher Pistons Lighter, optimized for high-speed operation. compression and pressures. Sturdy design to handle high forces from Lighter design for lower pressure and high- Connecting Rod combustion. speed applications. Heavier to convert high torque from pistons to Lighter, designed for high RPMs with lower Crankshaft rotational energy. torque. Controls valve timing, synchronized with fuel Controls valve timing, synchronized with Camshaft injection timing. ignition system. MEC 756 – POWER PLANT ENGINES 8  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.1 – Basic Components of Diesel Table: Basic Components of Diesel and SI Engines Component Diesel Engine SI Engine Fuel injector delivers fuel at high pressure Spark plug ignites the air-fuel mixture, Fuel Injector / Spark Plug for combustion. requiring an external ignition system. Commonly used to enhance air intake Optional, used in performance-focused Turbocharger pressure, improving efficiency and torque. engines for increased power. Heavier, smooths power delivery in slower Lighter, optimized for engines with higher Flywheel engines with high torque. RPMs and lower torque. Requires robust oil to handle high friction Uses lighter oils as engine operates under Lubrication System and heat. lower stress. Larger, designed to dissipate higher heat Smaller, handles lower heat loads from Cooling System levels from combustion. combustion. MEC 756 – POWER PLANT ENGINES 9  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.1 – Basic Components of Diesel Table: Components Exclusive to Diesel and SI (Petrol) Engines Component Diesel Engine (Exclusive) SI Engine (Petrol) (Exclusive) Directly injects fuel into the combustion Not present; instead uses a Fuel Injector chamber at high pressure. carburetor or port fuel injector. Used to preheat the air in the combustion Not needed; ignition relies on Glow Plugs chamber for cold starts. spark plugs. Less common; used primarily Turbocharger (Commonly used in Increases air intake pressure to improve in performance-focused SI Diesel) efficiency and power output. engines. Intercooler (Often paired with Cools compressed air from the Optional; typically found in turbocharger) turbocharger to increase air density. turbocharged petrol engines. Higher Capacity Cooling Designed to manage the higher heat from Smaller cooling system for System diesel combustion. lower heat generation. MEC 756 – POWER PLANT ENGINES 10  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.1 – Basic Components of Diesel Table: Components Exclusive to Diesel and SI (Petrol) Engines Component Diesel Engine (Exclusive) SI Engine (Petrol) (Exclusive) Not present; ignition relies solely on Present to ignite the air-fuel mixture Spark Plug compression of air-fuel mixture. via an electric spark. Not required; no need for external Distributes high voltage to spark Distributor/Ignition Coil ignition system. plugs for ignition. Controls air intake, critical for Not used in traditional diesel engines; Throttle Body regulating engine speed and air intake is unthrottled. performance. Less common in older diesel engines, Catalytic Converter (Standard in Standard to reduce harmful but modern ones include diesel modern petrol engines) emissions in petrol engines. oxidation catalysts (DOCs). Not used in diesel engines; fuel is Found in older petrol engines to Carburetor (Older SI engines) injected directly. mix air and fuel before combustion. MEC 756 – POWER PLANT ENGINES 11  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.2 – Fuel Delivery System in Compression-Ignition (CI) Engines 1. Overview of CI Engine Fuel Delivery System The fuel delivery system in CI engines ensures precise fuel injection into the combustion chamber at high pressure. Unlike SI engines, CI engines rely on compression ignition, meaning fuel is injected directly into highly compressed hot air for combustion. MEC 756 – POWER PLANT ENGINES 12  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.2 – Fuel Delivery System in Compression-Ignition (CI) Engines 2. Key Components of the Fuel Delivery System Component Function Fuel Tank Stores the diesel fuel. Fuel Pump Draws fuel from the tank and supplies it to the fuel injectors under high pressure. Fuel Filter Removes impurities and contaminants from the fuel to protect the injectors and the engine. Fuel Injector Delivers precise amounts of fuel into the combustion chamber at extremely high pressure. High-Pressure Fuel Lines Transport fuel from the fuel pump to the injectors while maintaining high pressure. Common Rail (if Stores pressurized fuel and delivers it to the injectors uniformly (used in modern diesel applicable) engines). Precisely controls the timing and amount of fuel delivered to the injectors in older CI Injection Pump systems. Glow Plugs (Optional) Preheat air in the combustion chamber for better cold-start performance. MEC 756 – POWER PLANT ENGINES 13  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.2 – Fuel Delivery System in Compression-Ignition (CI) Engines 3. Working Principle 1. Fuel Supply and Filtering Fuel is drawn from the tank by the fuel pump. It passes through the fuel filter to remove any impurities. 2. Fuel Pressurization The fuel is pressurized by the injection pump or sent to the common rail in modern systems. High pressure is crucial to ensure fine atomization during injection. 3. Fuel Injection The fuel injector sprays the fuel into the combustion chamber. Injection timing and quantity are precisely controlled to ensure efficient combustion and power generation. 4. Combustion The injected fuel mixes with hot, compressed air and ignites spontaneously due to high temperatures. MEC 756 – POWER PLANT ENGINES 14  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.2 – Fuel Delivery System in Compression-Ignition (CI) Engines 4. Types of Injection Systems Direct Injection (DI): Fuel is injected directly into the combustion chamber. Used in most modern diesel engines for higher efficiency and better performance. Indirect Injection (IDI): Fuel is injected into a pre- combustion chamber connected to the main cylinder. Offers smoother operation but lower efficiency compared to DI. MEC 756 – POWER PLANT ENGINES 15  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.2 – Fuel Delivery System in Compression-Ignition (CI) Engines 5. Advantages of CI Fuel 6. Maintenance Considerations Conclusion Delivery System Fuel Filters: Require regular The fuel delivery system in CI High Efficiency: Direct replacement to prevent clogging engines is a critical component injection allows for better and injector damage. that ensures efficient combustion fuel economy. Fuel Injectors: Need periodic through precise fuel injection. Robust Performance: cleaning or replacement to Advances like common rail Capable of handling high maintain precise fuel delivery. systems have improved the torque demands. High-Pressure Lines: Must be performance, efficiency, and Better Atomization: High- inspected for leaks or wear to emissions of modern diesel pressure injection ensures ensure system integrity. engines. fine fuel atomization for efficient combustion. MEC 756 – POWER PLANT ENGINES 16  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.3 – Glow Plugs 1. Purpose of Glow Plugs Glow plugs are critical for the cold starting of diesel engines, particularly in colder temperatures. Their main function is to preheat the air in the combustion chamber, ensuring the fuel ignites when injected, even when the engine is cold. MEC 756 – POWER PLANT ENGINES 17  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.3 – Glow Plugs 2. Working Principle of Glow Plugs Glow plugs are heating elements powered by electricity. When the engine is cold, the glow plug is energized, causing it to heat up. The heated glow plug raises the temperature of the air in the combustion chamber, assisting in the ignition of the diesel fuel once injected under compression. In modern engines, glow plugs are also used to assist with smoother idling and reduce emissions during the warm-up phase. MEC 756 – POWER PLANT ENGINES 18  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.3 – Glow Plugs 3. Key Components of a Glow Plug System Component Function The heating element that heats up to raise air temperature in Glow Plug the combustion chamber. Regulates the timing of glow plug activation and deactivation, Glow Plug Control Unit based on engine temperature. Power Supply Circuit Supplies the necessary current to heat the glow plug. Monitors and manages the glow plug temperature to prevent Thermal Management System overheating or damage. MEC 756 – POWER PLANT ENGINES 19  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.3 – Glow Plugs 4. Types of Glow Plugs 1. Conventional Glow Plugs (Older Design) Made of metal and require longer preheating times. Common in older diesel engines. Typically remain on until the engine reaches a certain temperature. 2. Fast-Heating (Ceramic) Glow Plugs Made of ceramic material, which heats up faster and can withstand higher temperatures. Common in modern diesel engines, providing quicker start-up times and more efficient performance. 3. Intelligent Glow Plugs Equipped with sensors to control the temperature and adjust the preheating cycle more precisely. Used in newer diesel engines for better control over emissions and fuel consumption. MEC 756 – POWER PLANT ENGINES 20  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.3 – Glow Plugs 5. Operation Sequence (Glow Plug Activation) 1. Cold Start When the engine is cold, the glow plug control unit powers the glow plugs to preheat the combustion chamber. 2. Pre-Heating The glow plugs remain on for a certain period (up to 20-30 seconds, depending on engine temperature) to warm the air in the combustion chamber. 3. Injection and Ignition After the preheating phase, fuel is injected into the chamber, and the heat from the glow plug helps to ignite the fuel under compression. 4. Post-Heating (In Modern Engines) In modern engines, glow plugs may stay active for a short period after ignition to reduce emissions and ensure smoother engine operation during the warm-up phase. MEC 756 – POWER PLANT ENGINES 21  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.3 – Glow Plugs 6. Signs of Faulty Glow Plugs 7. Maintenance and Care Conclusion Hard Starting: Difficulty in Routine Checks: Glow plugs Glow plugs play a vital role in the starting the engine, especially in should be inspected for wear or cold starting and efficient operation cold weather. damage, especially in cold of diesel engines, particularly in low- Increased Smoke: Excessive weather. temperature conditions. Their ability smoke or rough engine running Replacement: Faulty or worn to preheat the combustion chamber during startup. glow plugs should be replaced ensures smooth ignition of fuel, Poor Engine Performance: to ensure efficient starting and leading to improved engine Reduced power, increased fuel fuel combustion. performance, reduced emissions, and consumption, or poor idle quality. Electrical Connections: reliable starting even in harsh Ensure that electrical climates. Regular maintenance of the Check Engine Light: A warning connections to the glow plugs glow plug system is essential for light may appear if the glow plug are clean and tight to avoid optimal engine functionality. system is malfunctioning. faulty operation. MEC 756 – POWER PLANT ENGINES 22  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.4 – Supercharger in Diesel Engines 1. Purpose of Supercharger A supercharger is a forced induction system that increases the air intake into the engine's combustion chamber, which in turn enhances engine power and efficiency. In diesel engines, a supercharger helps overcome the inherent limitation of the air-fuel mixture's density, improving the compression ratio and ensuring that more air enters the combustion chamber. MEC 756 – POWER PLANT ENGINES 23  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.4 – Supercharger in Diesel Engines 2. Types of Superchargers Type Description Uses two rotating lobes to force air into Roots the intake manifold. Provides instant Supercharger boost. Compresses air between two meshing Twin-Screw screws, creating high pressure and Supercharger airflow. More efficient than Roots. Uses a rotating impeller to draw in and Centrifugal compress air, typically more efficient at Supercharger higher engine speeds. Powered by an electric motor, eliminates Electric parasitic power loss from the engine but Supercharger typically used in hybrid systems. MEC 756 – POWER PLANT ENGINES 24  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.4 – Supercharger in Diesel Engines 3. Working Principle of a Supercharger 1. Air Compression: The supercharger compresses the incoming air before it enters the engine’s combustion chamber. This results in a higher air density. 2. Increase in Air Intake: By forcing more air into the combustion chamber, a greater amount of oxygen is available for combustion, enabling more fuel to be burned. 3. Boost in Power: The increased air-fuel mixture allows for more powerful combustion, thereby increasing engine output and efficiency. 4. No Lag: Superchargers provide instant boost because they are mechanically driven by the engine’s crankshaft. MEC 756 – POWER PLANT ENGINES 25  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.4 – Supercharger in Diesel Engines 4. Benefits of a Supercharger in Diesel Engines Increased Power Output: More compressed air in the combustion chamber allows for more fuel to burn, increasing engine power. Improved Engine Efficiency: With more oxygen in the chamber, combustion is more efficient, leading to better fuel efficiency and reduced exhaust emissions. Better Performance at High Altitudes: Since air density decreases at higher altitudes, the supercharger compensates for the lower oxygen levels, maintaining engine performance. Reduced Turbo Lag: Unlike turbochargers, superchargers provide immediate power and eliminate the lag associated with waiting for exhaust gases to spool up the turbo. MEC 756 – POWER PLANT ENGINES 26  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.4 – Supercharger in Diesel Engines 5. Applications of Superchargers in Diesel 6. Disadvantages of Superchargers Engines Power Loss: Superchargers are Heavy Duty Diesel Engines: Superchargers mechanically driven by the engine's are used in diesel engines of trucks, buses, and crankshaft, meaning they draw power construction machinery to improve low-end from the engine, reducing overall torque and overall power, especially when efficiency (known as parasitic loss). dealing with heavy loads. Fuel Consumption: Because they Performance Diesel Engines: Used in high- draw power from the engine, performance diesel vehicles, like those in superchargers may lead to higher fuel motorsport or modified diesel trucks, to increase consumption in some applications. power and responsiveness. Heat Generation: Compressing air Marine Diesel Engines: Superchargers increases its temperature, which can enhance performance and power for marine lead to engine knocking or reduced applications, especially in high-load conditions. efficiency unless an intercooler is used to cool the intake air. MEC 756 – POWER PLANT ENGINES 27  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.4 – Supercharger in Diesel Engines 7. Maintenance Considerations Conclusion The supercharger in a diesel engine Lubrication: Superchargers require boosts air intake, improving power, adequate lubrication to prevent wear and efficiency, and overall engine performance. tear on the rotating components. While it offers instant power and helps Air Filter: Ensure that the intake system maintain performance at high altitudes, it has clean air filters to prevent dirt and comes with some trade-offs in terms of fuel debris from entering the supercharger and efficiency and engine load. Superchargers causing damage. are particularly beneficial in heavy-duty Belts and Pulleys: Regular inspection of and performance diesel engines, where the belts and pulleys that drive the increased torque and power are essential. supercharger is crucial to ensure optimal operation. MEC 756 – POWER PLANT ENGINES 28  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 1. Purpose of Turbocharger A turbocharger is a forced induction system that uses exhaust gases to drive a turbine, which in turn compresses the intake air, increasing the amount of air (and oxygen) entering the engine. The primary function is to increase engine power and efficiency by improving the combustion process and maximizing fuel utilization. MEC 756 – POWER PLANT ENGINES 29  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 2. Working Principle of a Turbocharger 1. Exhaust Gases Drive the Turbine: The turbocharger is powered by the exhaust gases produced during combustion. These gases spin a turbine connected to a compressor. 2. Compression of Air: The turbine’s rotation drives the compressor, which draws in and compresses the incoming air before it enters the engine’s intake manifold. 3. Increased Air Intake: The compressed air contains more oxygen, allowing the engine to burn more fuel, which results in greater power output. 4. Boost in Engine Power: By forcing more air into the combustion chamber, the turbocharger enhances the efficiency and power of the engine without increasing its size. MEC 756 – POWER PLANT ENGINES 30  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 3. Key Components of a Turbocharger Component Function Driven by exhaust gases, it spins to power the Turbine compressor. Compresses intake air to increase its density Compressor before entering the combustion chamber. Compressor Encloses the compressor and directs air into the Housing engine’s intake system. Turbine Encloses the turbine, directing exhaust gases Housing through it to generate power. Regulates the flow of exhaust gases to control the Wastegate turbocharger’s speed and boost pressure. Bearing Supports the rotating shaft between the turbine System and compressor to reduce friction. Intercooler Cools the compressed air before it enters the (Optional) combustion chamber, improving efficiency. MEC 756 – POWER PLANT ENGINES 31  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 4. Types of Turbochargers Type Description One turbocharger for the entire Single Turbo engine. Common in many modern diesel engines. Two turbochargers of similar size Twin-Turbo working in parallel to boost engine (Parallel) power. One smaller turbocharger for low- Twin-Turbo speed boost and one larger (Sequential) turbocharger for high-speed boost. Variable Adjusts the geometry of the turbine Geometry blades to optimize boost pressure Turbocharger across a wide range of engine (VGT) speeds. MEC 756 – POWER PLANT ENGINES 32  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 5. Benefits of a Turbocharger in Diesel Engines Increased Power and Efficiency: By using exhaust gases to compress intake air, a turbocharger enables the engine to produce more power without increasing engine size. Improved Fuel Efficiency: Since more oxygen is available for combustion, the engine can burn fuel more efficiently, leading to improved fuel economy. Better Performance at High Altitudes: In higher altitudes, where the air is thinner, the turbocharger compensates for the reduced oxygen, maintaining engine performance. Lower Emissions: The more complete combustion resulting from better air-fuel mixing can reduce harmful emissions, such as NOx and particulate matter, compared to naturally aspirated engines. MEC 756 – POWER PLANT ENGINES 33  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 6. Turbocharger vs. Supercharger Aspect Turbocharger Supercharger Driven by exhaust gases produced during Driven mechanically by the engine’s Power Source combustion. crankshaft. Can experience lag due to the time taken for Boost Response Provides instant boost without lag. exhaust gases to spool the turbine. More fuel-efficient as it uses exhaust gases for Less fuel-efficient due to parasitic Efficiency power. power loss from the engine. More complex due to exhaust routing and Simpler, with fewer components than Complexity turbine/compressor integration. a turbocharger. More maintenance due to higher heat and pressure, Easier maintenance, but can lead to Maintenance especially on the bearings and compressor. more wear on engine components. MEC 756 – POWER PLANT ENGINES 34  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 6. NA vs.Turbocharger vs. Supercharger – AUDI R8 V10 MEC 756 – POWER PLANT ENGINES 35  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 7. Benefits of a Turbocharger in Diesel Engines 8. Challenges and Disadvantages of Turbocharging Higher Power Output: A turbocharged engine can produce significantly more power than a naturally aspirated engine of Turbo Lag: There is often a delay in boost the same size, which is particularly useful for heavy-duty response as the turbocharger requires time to applications like trucks and construction machinery. spool up, especially at lower engine speeds. Fuel Efficiency: Since more air is compressed into the Heat Generation: Turbochargers generate a lot combustion chamber, the engine burns fuel more efficiently, of heat, which can cause engine components to increasing miles per gallon. wear more quickly if not properly managed. Compactness: A turbocharger increases engine power Maintenance Costs: Turbochargers are complex without requiring a larger engine displacement, saving weight systems with high wear and tear, requiring more and space. maintenance and higher replacement costs. Improved Low-End Torque: With the use of variable Potential for Overboost: Without a properly geometry turbochargers, modern diesel engines can generate functioning wastegate or boost control system, greater low-end torque, improving acceleration and drivability. there’s a risk of over-boosting, which can damage the engine. MEC 756 – POWER PLANT ENGINES 36  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.5 – Turbocharger in Diesel Engines 9. Maintenance Considerations for Turbocharged 10. Applications of Turbochargers in Diesel Engines Diesel Engines Heavy Duty Diesel Engines: Turbocharging is Regular Oil Changes: The turbocharger relies on common in large trucks, buses, and construction clean oil for lubrication, so regular oil changes are machinery to increase fuel efficiency and performance. essential for its longevity. Performance Diesel Vehicles: Diesel engines in Intercooler Maintenance: If an intercooler is used, it sports cars and performance vehicles often use should be regularly cleaned to ensure that the intake turbochargers for enhanced power output and quicker air remains cool and dense. acceleration. Inspection of Turbocharger Components: Regularly Marine Diesel Engines: Turbochargers are used in check for signs of wear on the turbocharger’s marine diesel engines for improved efficiency and bearings, turbine, and compressor. Look for oil leaks power, especially in high-load conditions. or unusual noise, which can indicate failure. Power Generation: Turbocharged diesel engines are Wastegate Functionality: Ensure the wastegate is widely used in power generation applications, working correctly to prevent excessive boost pressure, providing a balance of power, fuel efficiency, and which can damage the engine. durability. MEC 756 – POWER PLANT ENGINES 37  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.6 – Intercooler in Diesel Engines 1. Purpose of an Intercooler An intercooler is a heat exchanger used in turbocharged or supercharged engines to cool the compressed air before it enters the engine’s combustion chamber. Compressed air from the turbocharger or supercharger is hot; cooling it increases its density and improves combustion efficiency. MEC 756 – POWER PLANT ENGINES 38  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.6 – Intercooler in Diesel Engines 2. Working Principle of an Intercooler 1. Air Compression and Heating: When air is compressed by the turbocharger, its temperature rises, reducing air density. 2. Air Cooling: The hot, compressed air passes through the intercooler, where heat is dissipated, typically to the atmosphere. 3. Denser Air to the Engine: The cooler, denser air enters the combustion chamber, allowing more oxygen to be mixed with the fuel. 4. Improved Combustion: Denser air results in more efficient combustion, improving engine performance and reducing emissions. MEC 756 – POWER PLANT ENGINES 39  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.6 – Intercooler in Diesel Engines 3. Types of Intercoolers Type Description Uses ambient air to cool Air-to-Air the compressed air. Intercooler Commonly located at the front of the vehicle. Uses coolant (water) to Air-to- cool the compressed air. Water More efficient but requires Intercooler a separate cooling system. MEC 756 – POWER PLANT ENGINES 40  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.6 – Intercooler in Diesel Engines 4. Comparison of Intercooler Types Aspect Air-to-Air Intercooler Air-to-Water Intercooler Cooling Medium Ambient air Coolant (water) Depends on vehicle speed and Consistent, regardless of vehicle Cooling Efficiency ambient temperature speed More complex, requires additional Installation Simple and lightweight components Higher due to the need for a cooling Cost Lower system Suitable for heavy-duty or high- Use Case Ideal for high-speed vehicles performance applications MEC 756 – POWER PLANT ENGINES 41  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.6 – Intercooler in Diesel Engines 5. Key Components of an Intercooler System Component Function Main heat exchange area where compressed air is Core cooled. Inlet and Connects the turbocharger to the engine, allowing Outlet air to flow through the intercooler. (Optional) Increases airflow through the intercooler, Cooling Fans especially at low speeds. (For air-to-water systems) Circulates coolant to Coolant Pump absorb heat from the compressed air. Heat (For air-to-water systems) Transfers heat from the Exchanger coolant to the ambient air. MEC 756 – POWER PLANT ENGINES 42  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.6 – Intercooler in Diesel Engines 6. Benefits of an Intercooler in Diesel Engines 7. Maintenance Considerations for Intercoolers Increased Power Output: Cooling the air increases Regular Cleaning: Dirt, debris, and oil can accumulate its density, allowing more air and fuel to be in the intercooler, reducing its efficiency. Regular combusted, which increases power. cleaning is essential. Improved Fuel Efficiency: Denser air improves Leak Checks: Inspect for air or coolant leaks, as they combustion, leading to better fuel utilization. can lead to reduced performance or overheating. Reduced Engine Knock: Lower intake air Coolant Levels (for air-to-water systems): Ensure the temperature reduces the chances of premature coolant is at the correct level and free of contaminants. detonation (knock). Inspect Connections: Check hoses and clamps for Lower Exhaust Gas Temperature: Cooler intake air wear or damage to prevent air leaks. helps reduce exhaust gas temperature, minimizing thermal stress on engine components. Lower Emissions: Improved combustion reduces emissions of NOx and particulate matter. MEC 756 – POWER PLANT ENGINES 43  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.2 – Basic Components of a Compression-Ignition Engine 2.4.2.6 – Intercooler in Diesel Engines 8. Common Issues with 9. Applications of Intercoolers in Diesel Conclusion Intercoolers Engines The intercooler is a critical Heat Soak: In prolonged high- Passenger Cars: Enhances performance component in turbocharged performance situations, the and fuel efficiency in turbocharged diesel diesel engines, enhancing intercooler may retain heat, engines. performance by cooling and reducing its cooling efficiency. Commercial Vehicles: Improves power and densifying intake air. This leads efficiency in trucks and buses for better to better combustion, improved Leaks: Damaged cores or load-carrying capacity. power, increased fuel efficiency, connections can result in air and lower emissions. Proper leaks, reducing boost pressure Performance Vehicles: Used in high- maintenance ensures optimal and engine performance. performance diesel cars to maximize power performance and extends the Corrosion: In air-to-water output. intercooler’s lifespan. systems, coolant contamination Marine and Industrial Engines: Maintains or poor-quality materials can efficient operation under heavy and cause internal corrosion. continuous loads. MEC 756 – POWER PLANT ENGINES 44  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.3 – Four-Stroke Compression-Ignition Engine Operation 2.4.3.1 – The Four-Stroke Cycle Overview Compression-Ignition (CI) engines, also known as diesel engines, operate on the Diesel cycle. Combustion is initiated by heat generated from air compression rather than an external spark. Key Features No spark plug: Relies on compression heat for ignition. Fuel injection: High-pressure fuel injectors ensure precise timing and atomization of fuel. MEC 756 – POWER PLANT ENGINES 45  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.3 – Four-Stroke Compression-Ignition Engine Operation 2.4.3.1 – The Four-Stroke Cycle Four Strokes of Operation 1. Intake Stroke Objective: To draw air into the cylinder. Process: The intake valve opens while the piston moves downward. Air is drawn into the cylinder. No fuel is introduced during this stroke. 2. Compression Stroke Objective: To compress the air to high pressure and temperature. Process: Both intake and exhaust valves are closed. The piston moves upward, compressing the air. Compression ratio is typically high (14:1 to 25:1), generating sufficient heat to ignite fuel. MEC 756 – POWER PLANT ENGINES 46  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.3 – Four-Stroke Compression-Ignition Engine Operation 2.4.3.1 – The Four-Stroke Cycle Four Strokes of Operation 1. Power Stroke (Combustion Stroke) Objective: To produce work by burning fuel. Process: Near the end of the compression stroke, fuel is injected into the cylinder at high pressure. The compressed air ignites the fuel, causing rapid combustion. The resulting expansion forces the piston downward, generating power. 2. Exhaust Stroke Objective: To expel burned gases from the cylinder. Process: The exhaust valve opens while the piston moves upward. Burned gases are pushed out of the cylinder, preparing for the next cycle. MEC 756 – POWER PLANT ENGINES 47  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.3 – Four-Stroke Compression-Ignition Engine Operation 2.4.3.1 – The Four-Stroke Cycle – Thermodynamic Processes (P-v Diagram) MEC 756 – POWER PLANT ENGINES 48  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.3 – Four-Stroke Compression-Ignition Engine Operation 2.4.3.1 – The Four-Stroke Cycle Key Features No spark plug: Relies on compression heat for ignition. Fuel injection: High-pressure fuel injectors ensure precise timing and atomization of fuel. Turbocharging (optional): Often used to improve efficiency and power output by increasing the intake air pressure. Advantages High thermal efficiency: Due to high compression ratio and better fuel economy. Durability: Designed to withstand high pressures and temperatures. Fuel versatility: Can use biodiesel, diesel blends, and alternative fuels. Disadvantages Higher emissions: Nitrogen oxides (NOx) and particulate matter (PM) are significant concerns. Noise and vibration: CI engines are generally noisier than spark-ignition engines. Cost: Higher initial cost due to robust construction and complex fuel injection systems. MEC 756 – POWER PLANT ENGINES 49  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines Definition 2.4.4.1 – Definition & Key Assumptions The Diesel Cycle is an idealized thermodynamic cycle used to describe the functioning of a compression-ignition (CI) engine, commonly referred to as a diesel engine. It represents the series of processes involving air as the working fluid under idealized conditions. MEC 756 – POWER PLANT ENGINES 50  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines Key Assumptions 2.4.4.1 – Definition & Key Assumptions 1. Working Fluid: The working fluid is treated as an ideal gas (typically air), with constant specific heats. Combustion is replaced by an equivalent heat addition process. 2. Processes: The cycle consists of four processes, assumed to be internally reversible: 1. Isentropic Compression: Air is compressed adiabatically (no heat exchange). 2. Constant-Pressure Heat Addition: Heat is added at constant pressure (representing fuel injection and combustion). 3. Isentropic Expansion: Air expands adiabatically, performing work (power stroke). 4. Constant-Volume Heat Rejection: Heat is rejected at constant volume. MEC 756 – POWER PLANT ENGINES 51  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.1 – Definition & Key Assumptions Key Assumptions 3. No Friction: There are no frictional losses; all processes are assumed to be ideal. 4. Air Standard Assumptions: The cycle assumes an air-standard analysis, meaning only air is modeled, ignoring the actual fuel-air mixture and chemical reactions. 5. Closed Cycle: The cycle assumes a closed system where air undergoes cyclic processes without intake or exhaust, unlike the real open system of a diesel engine. 6. Heat Source and Sink: Heat addition and rejection are treated as occurring with an external source and sink. MEC 756 – POWER PLANT ENGINES 52  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.2 – Thermodynamic Analysis Process Description Related formula k Isentropic P2V2 − P1V1 mR(T2 − T1 ) k P1  V2   T1  k −1 1-2 W1→2 = = =   =    compression 1− k 1− k P2  V1   T2  Constant 2-3 pressure heat Qin = mC p (T3 − T2 ) Qin = c  m f  CHV addition k Isentropic P4V4 − P3V3 mR(T4 − T3 ) k P3  V4   T3  k −1 3-4 W3→4 = = =  =    expansion 1− k 1− k P4  V3   T4  Constant 4-1 volume heat Qout = mCv (T4 − T1 ) rejection MEC 756 – POWER PLANT ENGINES 53  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.2 – Thermodynamic Analysis ❑ Thermal efficiency of the Diesel cycle Wnet Q  th , Diesel = = 1 − out Qin Qin ❑ Apply the first law closed system to process 2-3, P = constant. Qnet ,23 − Wnet ,23 = U 23 3 Wnet ,23 = Wother ,23 + Wb ,23 = 0 +  PdV = 0 2 = P2 (V3 − V2 ) ❑ Thus, for constant specific heats Qnet , 23 = U 23 + P2 (V3 − V2 ) Qnet , 23 = Qin = mCv (T3 − T2 ) + mR(T3 − T2 ) Qin = mC p (T3 − T2 ) MEC 756 – POWER PLANT ENGINES 54  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.2 – Thermodynamic Analysis ❑ Apply the first law closed system to process 4-1, V = constant Qnet ,41 − Wnet ,41 = U 41 1 Wnet ,41 = Wother ,41 + Wb,41 = 0 +  PdV = 0 4 ❑ Thus, for constant specific heats Qnet , 41 = U 41 Qnet , 41 = −Qout = mCv (T1 − T4 ) Qout = −mCv (T1 − T4 ) = mCv (T4 − T1 ) ❑ The thermal efficiency becomes Qout  th , Diesel = 1− Qin mCv (T4 − T1 ) = 1− mC p (T3 − T2 ) MEC 756 – POWER PLANT ENGINES 55  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.2 – Thermodynamic Analysis ❑ Define a new quantity, the cut-off ratio, 𝑟𝑐 PV PV 4 4 = 1 1 where V4 = V1 v3 V3 T4 T1 rc = = v2 V2 T4 P4 = T1 P1 ❑ Recall processes 1-2 and 3-4 are isentropic, so PV 1 1 k = PV 2 2 k and PV 4 4 k = PV 3 3 k ❑ Since V4 = V1 and P3 = P2, we divide the second equation by the first equation and obtain k P4  V3  =   = rc k T4  V2  ❑ Therefore, 1 rc k − 1 th , Diesel = 1 − r k −1 k ( rc − 1) MEC 756 – POWER PLANT ENGINES 56  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.3 – Factors Affecting Diesel Cycle Efficiency 1. Compression Ratio (rv): Definition: The ratio of the maximum cylinder volume to the minimum cylinder volume. Effect: Higher compression ratios improve thermal efficiency by increasing the temperature and pressure of the air before combustion. Efficiency increases because of greater energy extraction during expansion. 2. Cut-off Ratio (rc): Definition: The ratio of the cylinder volume after heat addition to the cylinder volume before heat addition. Effect: A higher cut-off ratio reduces efficiency, as a greater portion of heat addition occurs at lower pressures. Lower cut-off ratios improve efficiency by limiting the extent of constant-pressure heat addition. 3. Specific Heat Ratio (γ\gammaγ): Definition: The ratio of specific heats (k or 𝛾). Effect: A higher specific heat ratio increases efficiency, as the air behaves more ideally during compression and expansion. MEC 756 – POWER PLANT ENGINES 57  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.4 – Real-World Deviations from the Ideal Diesel Cycle 1. Non-Isentropic Processes Compression and Expansion: Real processes involve heat transfer and friction, making them non-adiabatic and non-reversible. Losses reduce the efficiency of compression and expansion compared to the ideal cycle. 2. Incomplete Combustion In practical engines, combustion is not instantaneous or complete, leading to: Residual unburnt fuel. Reduced efficiency due to incomplete energy release. 3. Heat Loss Heat is lost to the surroundings through the cylinder walls, reducing the amount of heat available for conversion into work. 4. Pressure and Temperature Drops During heat addition, pressure and temperature may not remain constant due to: Delayed combustion. Variations in fuel injection timing and spray patterns. MEC 756 – POWER PLANT ENGINES 58  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.4 – Real-World Deviations from the Ideal Diesel Cycle 5. Exhaust Gas Flow Real engines lose energy in the form of high-temperature exhaust gases, which the ideal cycle assumes to be negligible. 6. Friction and Mechanical Losses Friction between moving parts, such as pistons and cylinders, and losses in the crankshaft mechanism lower the mechanical efficiency. 7. Air-Fuel Mixture Deviations The ideal cycle assumes pure air as the working fluid, but real engines deal with: A fuel-air mixture. Variations in air-fuel ratios leading to inefficiencies. 8. Variable Specific Heats Specific heats (cp and cv) vary with temperature, unlike the constant values assumed in the ideal cycle. This affects the thermodynamic calculations and efficiency. MEC 756 – POWER PLANT ENGINES 59  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.4 – Diesel Cycle: The Ideal Cycle for Compression-Ignition Engines 2.4.4.4 – Real-World Deviations from the Ideal Diesel Cycle 9. Ignition Delay Real diesel engines experience a delay between fuel injection and combustion, which: Alters the timing of heat addition. Affects pressure and temperature profiles. 10. Pumping and Scavenging Losses Real engines require work for: Intake of fresh air. Exhaust of burnt gases. These pumping losses reduce the net work output. 11. Knock and Noise Combustion irregularities, such as knocking and noise, can occur due to uneven burning of fuel, impacting performance and longevity. MEC 756 – POWER PLANT ENGINES 60  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.5 – Comparison between Otto and Diesel Cycles Aspect Otto Cycle Diesel Cycle Used in compression-ignition (CI) Used in spark-ignition (SI) engines. Air-fuel Working Principle engines. Fuel ignites due to high mixture is ignited by a spark. pressure and temperature. Heat Addition Process Heat is added at constant volume. Heat is added at constant pressure. Higher (14–22), as knocking is not an Compression Ratio (rv) Lower (6–13) to prevent knocking. issue. Higher for the same compression ratio but Higher due to higher rv but decreases Thermal Efficiency limited by lower rv. with higher cut-off ratio. Fuel Type Gasoline or volatile fuels. Diesel fuel with higher energy density. Higher CO and HC due to incomplete Emissions Higher NOx and particulates (soot). combustion. MEC 756 – POWER PLANT ENGINES 61  Faculty of Mechanical Engineering, UiTM Idris Saad 2.4.5 – Comparison between Otto and Diesel Cycles Aspect Otto Cycle Diesel Cycle 1 1 rc k − 1 Efficiency Formula 𝜂𝑡ℎ,𝑂𝑡𝑡𝑜 = 1 − th , Diesel = 1 − k ( rc − 1) 𝑟𝑣𝑘−1 r k −1 Higher power due to faster combustion Lower power per cycle but efficient at Power Output and engine speed. high loads. Depends significantly due to constant Specific Heat Ratio (k) Depends on both k and cut-off ratio. volume heat addition. Trucks, buses, ships, trains, heavy- Applications Cars, motorcycles, light vehicles. duty vehicles. MEC 756 – POWER PLANT ENGINES 62