Question 84Motor Plants - Assistant Engineer

The correct answer is D) volume. After the fuel is ignited in the cylinder of a diesel engine, but before the piston reaches top dead center (TDC), the volume of the cylinder remains relatively constant. This is because the piston has not yet reached the point of maximum compression, so the cylinder volume has not yet started to decrease. The other options are incorrect because: A) the temperature is increasing due to the combustion of the fuel, B) the pressure is increasing due to the combustion, and C) the energy is increasing due to the combustion, but the volume remains constant during this specific phase of the engine cycle.