26-02-2011, 10:20 AM
presented by:
A.BALAKRISHNAN
DG Engine Presentation.ppt (Size: 1.35 MB / Downloads: 203)
DG ENGINE PRESENTATION
Engine
• Diesel engine (also known as a compression-ignition engine and sometimes capitalized as Diesel engine) is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to spark-ignition engines such as a petrol engine (gasoline engine) or gas engine (using a gaseous fuel as opposed to gasoline), which uses a spark plug to ignite an air-fuel mixture. The diesel engine is modeled on the Diesel cycle.
• Major Parts of Engine:
Cylinder Blocks * Water Pumps * Crankshafts * Oil Pumps * Camshafts
Turbochargers * Governors * Fuel Pumps * Flywheel Housings
Manifolds * Oil Cooler Groups * Flywheels * Gear
Engine operation
Intake stroke
Piston moving down
Intake valve open
Exhaust valve closed
Pure air gets sucked in by the piston sliding downward.
Compression stroke
Piston moving up
Intake valve closed
Exhaust valve closed
The piston compresses the air above and uses thereby work, performed by the crankshaft
Power stroke
Piston moving down
Intake valve closed
Exhaust valve closed
In the upper dead-center, the air is max. Compressed: Pressure and Temperature are very high. Now the black injection pump injects heavy fuel in the hot air. By the high temperature the fuel gets ignited immediately (auto ignition). The piston gets pressed downward and performers work to the crankshaft.
Exhaust stroke
Piston moving up
Intake valve closed
Exhaust valve open
The burned exhaust gases are ejected out of the cylinder through a second valve by the piston sliding upward again.
Each stroke takes 180° of crankshaft rotation to complete
All cylinders fire in 720° of crankshaft rotation
720 divided by number of cylinders = firing interval
Odd fire V-6 engine (90° block with 120° rod journals)
Piston dwell time
Piston travel is at a minimum. . .
TDC and BDC
Crank moves horizontally
Piston velocity
Maximum when rod is 90° to crank
Acceleration
Maximum 30° earlier
Best VE is obtained by synchronizing valve opening with piston speeds
Other engine cycles
Overlap
Both valves are open
End of exhaust & start of intake
Low pressure in exhaust port
Blow down
Exhaust valve opens before BDC
To help evacuate cylinder before piston reverses
Pumping losses at end of exhaust stroke