From Top Dead Centre (TDC) to Bottom Dead Centre (BDC) on the practical power stroke, what happens to the temperature of the gases?

During the practical power stroke of a reciprocating engine, the transformation of gas behavior is critical to understanding engine efficiency and performance. As the piston moves from Top Dead Centre (TDC) to Bottom Dead Centre (BDC), the gases within the cylinder undergo significant changes in temperature, pressure, and volume according to the laws of thermodynamics.

Initially, at TDC, the gases are at maximum compression, resulting in high pressure and temperature. As the piston descends towards BDC, the gases expand. This expansion, especially if it occurs rapidly, leads to a brief rise in temperature due to the conversion of pressure energy to thermal energy as the combustion process occurs. However, once the engine reaches BDC and the expansion is no longer confined, the temperature begins to decrease as the gases cool and the volume increases significantly.

This option accurately describes the behavior of gases in a typical power stroke where temperature is influenced by both the combustion process and the expansion of the gases. The temperature rise is related to the combustion event that takes place shortly after TDC, while the initial energy of the gas molecules contributes to a short-term increase before they begin to cool as the piston approaches BDC.

Other choices, while they touch upon different aspects of gas behavior, do