A Volkswagen Passat has a six-cylinder Otto-cycle engine with compression ratio

Question

A Volkswagen Passat has a six-cylinder Otto-cycle engine with compression ratio r=10.6. The diameter of each cylinder, called the bore of the engine, is 82.5 mm. The distance that the piston moves during the compression in the (Figure 1) , called the stroke of the engine, is 86.4 mm. The initial pressure of the air-fuel mixture (at point a in the (Figure 2) ) is 8.50×104Pa, and the initial temperature is 300 K(the same as the outside air). Assume that 200 J of heat is added to each cylinder in each cycle by the burning gasoline, and that the gas has CV=20.5J/molK and =1.40.

Calculate the volume of the air-fuel mixture at point a in the cycle.

Calculate the total work done in one cycle in each cylinder of the engine.

Calculate the heat released when the gas is cooled to the temperature of the outside air.

Explanation / Answer

Solution: Efficiency of engine = 1 - 1/(10.6)^(0.4) = 0.61

The total work done per cycle per cylinder is then

Work_cycle_cylinder = 200 * 0.61 = 122 J

The heat released into the environment per cycle per cylinder is the difference between the input heat and the work done, this is

Heat_released_cycle_cylinder = 200 - 122 = 78 J

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