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DIESEL TECHNOLOGY. ENERGY AND POWER. Rudolf Diesel , inventor of the diesel engine.
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DIESEL TECHNOLOGY ENERGY AND POWER
Rudolf Diesel, inventor of the diesel engine. • In 1878, Rudolf Diesel was attending the Polytechnic High School of Germany (the equivalent of an engineering college) when he learned about the low efficiency of gasoline and steam engines. This disturbing information inspired him to create an engine with a higher efficiency, and he devoted much of his time to developing a "Combustion Power Engine." By 1892 Diesel had obtained a patent for what we now call the diesel engine. Rudolf Diesel
OBJECTIVES • On completion of this chaptera learner should: • Identify the two major differences between petrol and diesel engines. • Understand the function and operation of air and diesel fuel supply components • Explain the different combustion chambers. • Explain the difference between different fuel-injectors. • Understand the operation of diesel engine control systems and components • Understand the methods used to test and repair diesel fuel injection • Explain how to maintain a diesel system.
OVER VIEW • Diesel engines have long been the source of power for heavy-duty trucks, trains, and ships. • During the past few years, diesel engines have become more common as power sources for automobiles.
Basic Diesel Fuel Delivery System 1. Fuel Return Line 2. Fuel Injection Pump 3. Injectors 4. Fuel Filter 5. Fuel Tank 6. Swirl Pot 7. Fuel Feed Line
DIESEL vs OTTO ENGINE The main difference between Diesel vs Otto Engine is: The burning of the fuel. • In a Gasoline engine the air/fuel mixture enters the cylinder and creates a stoichiometric homogeneous mixture 14,7:1, which is ignited and the flame travels from the spark and outwards to the liner. • In the Diesel air enters the cylinder, fuel is injected, self-ignites and burns with a diffusion type of combustion (Air/Fuel Ratio of 40:1)
MAIN ADVANTAGES OF DIESEL OVER PETROL • Diesel powered automobiles average about 25% more kilometers per liter than petrol powered vehicles. • Specific power output – high torque • Operational safety • Production costs • Economy - fuel • Economy of operation • Reliability
MAIN DISADVANTAGES OF DIESEL OVER PETROL • Diesel engines, however, must be made larger, stronger, and heavier than petrol engines. • They must withstand combustion pressures two to three times higher than those produced in gasoline engines. • The added weight needed for strength reduces the acceleration of the automobile. • A diesel engine of the same horsepower as a gasoline engine is larger. • Noise • Greater NOx and soot generation
Compare Diesel vs Petrol • Spark ignition: • Gasoline engines use spark plugs to ignite fuel/ air mixture • Compression ignition: • Diesel engines uses the heat of compressed air to ignite the fuel (intakes air, compresses it, then injects fuel) • Fuel injection: • Gasolineuses port fuel injection or carburetion; • Diesel uses direct fuel injection or pre combustion chambers (indirect injection) • Glow plugs: • electrically heated wire that helps heat pre combustion chambers fuel when the engine is cold • when a diesel engine is cold, compression may not raise air to emperatureneeded for fuel ignition
Working Principle: 4-stroke Diesel • 1. Induction - Pure air is drawn into the cylinder • 2. Compression - The air is compressed to - high temperature and pressure (14:1 to 23:1) • 3. Power Stroke - Around TDC fuel is injected, which self-ignites - and burns, further increasing pressure and - thereby forcing the piston down. • 4. Exhaust - The hot gas is released to the surrounding
Diesel Fuel-Injection Components • The main components in a diesel fuel-injection system are the fuel-injection pump and the fuel injectors. • The job of the fuel injectors is to inject a measured amount of fuel into the combustion chamber. • When pressure is applied to the fuel, the injector opens and sprays fuel into the cylinder. • Combustion begins immediately.
High Pressure Fuel Injection Pumps • Can be of ‘Rotary’ or ‘In line’ design. Driven by the engine at half crankshaft speed • Pressurises the fuel and delivers it to the injections at the correct time for combustion • Accurately meters the fuel quantity to match engine load demands • Incorporates a governor to control engine speed and prevent the engine over speeding and damaging itself
Fuel-Injection Pump • Function: • The fuel-injection pump produces the necessary high fuel pressure. • On injection, diesel fuel must be under enough pressure to offset the pressure inside the combustion chamber (about 1000 psi during combustion). • If the fuel pressure were not at least as high as the pressure in the combustion chamber during combustion, the fuel would not inject. • Instead, pressure would leak from the combustion chamber into the injector nozzle
Fuel-Injection PumpContinued • The injection pump has two other functions. • It must regulate the amount of fuel directed to the cylinder. • It must also control the timing of the fuel injection. • Engine power depends on the amount of fuel supplied to the cylinders. • The time at which injectors spray fuel into the cylinders is just as important. • The injection pump controls this timing. • It makes sure that the injectors spray fuel just before TDC (top dead center) of the compression stroke. • By the time the fuel ignites, the piston will have started its downward motion.
The Diesel Governor Function of governor: • Controls idle speed • Controls Medium speed • Controls full speed • Supply extra fuel during cold start Automatically controls the engine speed and output by adjusting the fuel injection quantity in accordance with the load on the engine, and the amount that the accelerator pedal is depressed.
Combustion Chambers (Cylinder) Indirect-Injection Engine (IDI) Direct-Injection (DI)
Direct Injection • • Direct-Injection (DI) or Open Chamber Engine: • In this design, the fuel is injected directly into the cylinder chamber. • Direct injection engines have two design • philosophies: • -High-swirl design, which have a deep bowl in • the piston. • and moderate injection pressures. • -Low-swirl or quiescent engines are • characterized by having a shallow bowl in the • Piston. • All newer diesel engines use direct fuel injection • • Much higher fuel pressure then indirect fuel • injection (example TDI )
Indirect-Injection Engine (IDI) In this design, the fuel is injected into a small pre-chamber attached to the main cylinder chamber. The combination of rapidly swirling air in the pre-chamber and the jet-like expansion of combustion gases from the pre-chamber into the cylinder enhances the mixing and combustion of the fuel and air. Starting is aided by a high compression ratio (24-27) and a glow plug mounted in the pre-chamber. This design has the advantage of less noise and faster combustion, but typically suffers from poorer fuel economy.
Fuel Injectors • Two types: • Hole type (Direct injection) • Pintle (Indirect injection)
Fuel Injectors • Fuel is delivered to the injectors via thick walled high pressure steel pipes Injector pipes are of equal volume/length to ensure accuracy of timing between cylinders • Each injector is fitted in the cylinder head above each combustion chamber Each injector sprays atomized fuel in to the combustion chamber to insure complete combustion
Fuel Injectors “Fuel return to tank” (leak off) 2. Pressure adjusting shim 3. Pressure spring 4. Injector body 5. High pressure fuel supply 6. Pressure pin 7. Needle valve 8. Nozzle retaining nut 9. Nozzle
Glow Plug Function of the glow plug: • Heating element • Warms the air in the pre-combustion chambers during cold start
Diesel fuel filter with water separator 1 Inlet 2 Outlet 3 Filter element 4 Water drain plug 5 Cover plate 6 Housing 7 Supporting tube 8 Water accumulation chamber
Maintenance • Change fuel filters regularly • Clean water traps regularly • Repair all diesel leaks • Use clean diesel • Replace cam belt at prescribed interval • Check for loose injectors • Repair / replace worn out injectors • Secure all air leaks on engine intake manifolds • Calibrate diesel injection pumps according to manufacturing specification. • Listen for diesel knock
Largest Diesel Engine in the World: The TheWartsila-Sulzer RTA96-C Turbocharged Two-Stroke Diesel Engine • Total engine weight: 2300 tons (The crankshaft alone weighs 300 tons.) • Maximum power: 108,920 hp at 102 rpm
Thank you Any questions?
Combustion Chambers (where the fuel is burnt) In the C.I. engine the fuel is injected into the combustion chamber, it the has to mix thoroughly with the air, ignite and burn all at the same time. To insure this happens, two types of combustion chamber have been developed. Direct Injection Indirect Injection
Fig 8 1 Multihole injector 2 ω piston recess 3 Glow plug
Fig 23 1 Fuel tank 2 Resupply pump 3 Fuel filter 4 In-line fuel-injection pump 5 Nozzle-and-holder assembly 6 Overflow valve 7 Overflow restriction ___ Supply line ----- Return line
DISADVANTAGE OF IN-DIRECT INJECTION • Indirect-injection diesel engines are less thermally efficient due to • the greater surface area of their combustion chambers and so suffer • more from cold-start problems. They require longer pre-heating • times than direct-injection engines which often do not need glow • plugs at all in temperate or hot climates even for a cold start. • In a typical diesel engine the glow plugs are switched on for • between 10 and 20 seconds prior to starting. Older less efficient • or worn engines may need as much as a minute (60 seconds) of • pre-heating.
The compression ratio is likely to be selected on the basis of the lowest compression ratio thatwill provide satisfactory cold-starting performance, and even this compression ratio can behigher than that for optimum efficiency. For direct injection diesel engines with a displacementof 0.5 Lcylinder, the compression ratio is approximately 18: 1, whereas for larger engines(say, 1 Lcylinder and greater), the compression ratio will be approximately 15: 1 or slightlylower. The larger displacement engines have a better volume-to-surface-area ratio; thus, lessheat transfer occurs, and satisfactory cold-starting can be achieved with a lower compressionratio.
Fuel Injection Equipment • To obtain small droplets that will evaporate quickly, the fuel injector nozzle holes can be assmall as 0.15 mm. To inject sufficient fuel in the short time available, injectionpressures must be 1500 bar or higher. These high pressures also ensure that the fuel jetdisperses well within the combustion chamber. Likewise, these high pressures have led to theuse of electronic unit injectors (EUI) and common rail (CR) injection systems in preferenceto the traditional pumpline-injector (PLI) systems.
