A compression-ignition engine runs on a fuel of the following analysis by weight: carbon \(84 \%\), hydrogen \(16 \%\). If the pressure at the end of combustion is 55 bar, the volume ratio of expansion is \(15: 1\), the pressure and temperature at the end of expansion are \(1.75 \mathrm{bar}\) and \(600^{\circ} \mathrm{C}\) respectively, calculate:

a. the variable specific heat at constant volume for the products of combustion; and

b. the change in entropy during the expansion stroke per kg molecule.

The expansion follows the law \(p V^{n}=\mathrm{C}\) and there is \(60 \%\) excess air. The specific heats at constant volume in \(\mathrm{kJ} / \mathrm{kmol} \mathrm{K}\) between \(600{ }^{\circ} \mathrm{C}\) and \(2400{ }^{\circ} \mathrm{C}\) are:

The water vapour \(\left(\mathrm{H}_{2} \mathrm{O}\right)\) may be considered to act as a perfect gas. [(a) \(22.1+0.0184 T\); (b) \(-11.42 \mathrm{~kJ} / \mathrm{kmol} \mathrm{K]}\)

Transcribed Image Text:

02 HO 32+0.0025T N 29 +0.0025T 34 +0.087 CO 50+ 0.00677