“DIESEL ENGINE” A SUMMER TRAINING PRESENTATION ON www.engineersportal.in

What is an engine? An engine is a device which transform the chemical energy from fuel supply into thermal energy which is used to produce mechanical power. www.engineersportal.in

CLASSIFICATION OF ENGINE EXTERNAL COMBUSTION ENGINE INTERNAL COMBUSTION ENGINE - STEAM ENGINE - PETROL ENGINE - DIESEL ENGINE www.engineersportal.in

Diesel Engines Internal Combustion engine operates using diesel cycle manufactured in two stroke and four stroke versions www.engineersportal.in

4 STROKE DIESEL ENGINE This is a simplified model of a single cylinder Diesel engine to show the principal parts, their relationships to each other and how the engine works. Is not based on any real engine, but is generally representative of real engines. Most real engines are made up of several of this unit sharing a single flywheel and cam shaft drive e.g. Three, four and six cylinder engines. Many minor details and some components are left out for clarity, for example the bearings, exhaust pipe silencer, air intake filter and the fuel injection pump. www.engineersportal.in

MAIN COMPONENTS OF DIESEL ENGINE 1.CYLINDER 2.CYLINDER HEAD 3.PISTON 4.CONNECTING ROD 5.CRANK SHAFT 6.CRANK CASE 7.LINER 8.INLET VALVE 9 .OUTLET VALVE 10.CAM SHAFT 11.FLYWHEEL 12. FUEL INJECTOR www.engineersportal.in

CYLINDER AND CYLIDER HEAD CYLINDER- Cylinder, a large round hole bored straight and parallel through the Block CYLINDER HEAD- The Cylinder Head sits on the top of the Block to close off the top of the Cylinder. It also carries the Valves, Fuel Injector and the Inlet and Exhaust passages www.engineersportal.in

PISTON AND PISTON RINGS Piston- the part of the engine that moves up and down in the cylinder converting the gasoline into motion PISTON RINGS- The Piston Rings fit in grooves on the Piston. They seal the Piston to be ‘gas tight’ in the Cylinder of the Block www.engineersportal.in

CONNECTING ROD The Connecting Rod is inserted into a large recess in the bottom of the Piston The Piston is attached to swivel on the ‘little end’ of the Connecting Rod by the Gudgeon Pin through the side of the Piston. The ‘Big end’ of Connecting Rod fits onto the ‘throw’ of the Crank Shaft The Connecting Rod connects the linear ‘up and down’ motion of the Piston within the Cylinder with the circular rotary motion of the Crank Shaft. Little End Big End www.engineersportal.in

VALVES One set of a Cam and a Valve controls the Inlet flow of fresh air into the Cylinder. The other set controls the burnt Exhaust Gases out of the Cylinder. Both these Valves are spring loaded to shut and seal the Cylinder during the Compression and Power strokes. They open into the Cylinder, so that they are held closed by the high pressures during the Compression and Power strokes. www.engineersportal.in

FUEL INJECTOR The Fuel Injector is connected to a high pressure pump that is not illustrated. It sprays a small amount of diesel fuel into the Cylinder at the end of the Compression Stroke and beginning of the Power Stroke. The fuel is sprayed through several very small holes at very high pressure in order to form a fine mist of droplets of fuel that will ignite easily and burn quickly in the hot air Nozzle tip with several small holes for fuel spray www.engineersportal.in

Camshafts turn at one half crankshaft speed. Camshafts can be driven with a gear, chain and sprocket, or toothed belt. Camshafts have one lobe for each valve. www.engineersportal.in

ONE CYCLE OF DIESEL ENGINE COMPLETES IN FOUR STROKES- WORKING OF DIESEL ENGINE ONE CYCLE OF DIESEL ENGINE COMPLETES IN FOUR STROKES- 1.SUCTION OR INTAKE STROKE 2.COMPRESSION STROKE 3.EXPANSION OR POWER STROKE 4.EXHAUST STROKE www.engineersportal.in

Intake Stroke Piston moves from TDC to BDC creating vacuum in the cylinder Intake valve opens allowing only air to enter the cylinder and exhaust valve remains closed www.engineersportal.in

Compression Stroke Both valves stay closed Piston moves from BDC to TDC, compressing air to 22:1 Compressing the air to this extent increases the temperature inside the cylinder to above 1000 degree F. www.engineersportal.in

Power Stroke Both valves stay closed When the piston is at the end of compression stroke(TDC) the injector sprays a mist of diesel fuel into the cylinder. When hot air mixes with diesel fuel an explosion takes place in the cylinder Expanding gases push the piston from TDC to BDC www.engineersportal.in

Exhaust Stroke Piston moves from BDC to TDC Exhaust valve opens and the exhaust gases escape Intake valve remains closed www.engineersportal.in

V ALVE TIMING DIAGRAM www.engineersportal.in

Inlet Valve opening and closing : VALVE TIMING DIAGRAM Inlet Valve opening and closing : In an actual engine , the inlet valve begins to open 5°C to 20 °C before the piston reaches the TDC during the end of exhaust stroke. This is necessary to ensure that the valve will be fully open when the piston reaches the TDC. If the inlet valve is allowed to close at BDC , the cylinder would receive less amount of air than its capacity and the pressure at the end of suction will be below the atmospheric pressure . To avoid this the inlet valve is kept open for 25° to 40°after BDC. Exhaust valve opening and closing : Complete clearing of the burned gases from the cylinder is necessary to take in more air into the cylinder . To achieve this the exhaust valve is opens at 35° to 45° before BDC and closes at 10° to 20° after the TCC. It is clear from the diagram , for certain period both inlet valve and exhaust valve remains in open condition. Fuel valve opening and closing : The fuel valve opens at 10° to 15 °before TDC and closes at 15° to 20 ° after TDC . This is because better evaporation and mixing fuel. www.engineersportal.in

Cetane Number and Fuel Stability • Measures the readiness of a fuel to auto-ignite. • High cetane means the fuel will ignite quickly at the conditions in the engine (does not mean the fuel is highly flammable or explosive). • Most fuels have cetane numbers between 40 and 60. • ASTM D 975 requires a minimum cetane number of 40 (so does EPA for on-highway fuel). Fuel Stability- • Fuel will undergo chemical degradation if in contact with oxygen for long periods or at high temperatures. • There is no method specified in ASTM D975 for diesel fuels. • ASTM D 2274 is most commonly referenced. • FIE/OEM have a strong interest in stability www.engineersportal.in

Turbochargers & Superchargers • Increase or compress more air to be delivered to each engine cylinder • Superchargers: mechanically driven from engine crankshaft • Turbochargers: driven by waste exhaust gases • increased air mass improves the engine's thermal efficiency (fuel economy) and emissions performance, depending on other factors. • Turbochargers must operate at high temperatures and high rotational speeds. • Variable Geometry Turbochargers www.engineersportal.in

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COMPARISON B/W PETROL AND DIESEL ENGINE PETROL ENGINE DIESEL ENGINE 1.WORKS ON OTTO CYCLE WORKS ON DIESEL CYCLE 2.FUEL USED IS PETROL FUEL USED IS DIESEL 3.SPARK PLUG USED FUEL INJECTOR USED 4.LOW COMPRESSION RATIO HIGH COMPRESSION RATIO 5.HIGHER MAXIMUM RPM LOWER MAXIMUM RPM 6.LIGHTER IN WEIGHT HEAVIER IN WEIGHT 7.HIGHER MAXIMUM EFFICIENCY LOWER MAXIMUM EFFICIENCY 8.FUEL AND AIR MIXTURE IN SUCTION STROKE FUEL IS INJECTED DIRECTLY INTO COMBUSTION CHAMBER AT THE END OF COMPRESSION STROKE www.engineersportal.in

APPLICATIONS www.engineersportal.in

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