The Diesel Cycle Avinash Jayakumar Objective To introduce

The Diesel Cycle Avinash Jayakumar Objective: To introduce and explain the basic concepts of the diesel cycle

If you Dare to Care… • The diesel cycle is the combustion process of a type of internal combustion engine • The burning of the fuel is triggered not by a spark plug as in the Otto cycle, but rather by the heat generated in compressing the fuel-air mixture. • Used in automobiles, emergency power generation and diesel-electric submarines.

If you Still Dare to Care… • Only air is drawn into the engine and compressed. • The fuel is then injected directly into the cylinder with a highpressure fuel injector when the piston reaches the top of its motion. • The fuel is thicker and burns more slowly than petrol, so the piston is already moving down by the time the combustion completes. • Compression Stroke - Adiabatic compression of gas fuel mixture in the cylinder. Ignition of gas fuel mixture. Fuel is ignited by high temperature due a large compression. Burning takes places while the pressure is essentially constant. • Expansion Stroke. Adiabatic, isentropic expansion of gases. This is the part of the cycle that does positive work. Exhaust of the spent gases and the intake of a new fuel mixture into the cylinder. The volume is the same at beginning and ending of the exhaust and intake stroke.

Bringing it into Focus…

An example… The four cycles of the diesel engine are: 1 - The piston is moved away from the cylinder head by the crankshaft, drawing only air into the cylinder. 2 - The piston moves towards the cylinder head, compressing the air. At the end of the stroke vaporized fuel is injected into the cylinder and is ignited by the high temperature of the air. 3 - The piston is forced away from the cylinder head by the gas, expanding after the ignition of the fuel. 4 - The exhaust valve is opened and the piston moves towards the cylinder head, driving the exhaust gases from the cylinder.

Finally…(!) • A thermodynamic cycle in which only air is admitted in the intake stroke. • The air is then adiabatically compressed, and fuel is injected into to the hot air in the form of many small drops (not a vapor). • Each drop burns over a small time, giving an approximation of a isobaric explosion. • The explosion pushes the cylinder outwards. • The power stroke, valve exhaust, and exhaust stroke which follow are identical to those in the Otto cycle.

Sources of Knowledge: • http: //www. ac. wwu. edu/~vawter/Physics. N et/Topics/Therm. Law 2/Entropy/Gas. Cycle. E ngines. html • http: //scienceworld. wolfram. com/physics/D iesel. Cycle. html • http: //science. howstuffworks. com/twostroke 1. htm • http: //en. wikipedia. org/wiki/Diesel_cycle