While the geometric compression ratio of an engine is VJV,,,, the actual compression process starts somewhere between bottom-center and when the inlet valve closes, and it is conditions at time of...

While the geometric compression ratio of an engine is VJV,,,, the actual compression process starts somewhere between bottom-center and when the inlet valve closes, and it is conditions at time of spark (for an SI engine) or fuel injection (for a CI engine) that determine ignition. At low engine speed, compression starts about the time when the inlet valve closes. With this assuplption, for the diesel engine of Prob. 4.13, calculate the air pressure and temperature at the start of injection. The inlet valve closes at 30' after BC; injection commences 15" before TC. Use the gas tables. Compare your answers with those of Prob. 4.13(b). Internal energy of combustion of butane at 298 K is Air = -2.659 MJ/gmol. Extract from gas tables for products of combustion for 50 percent stoichiometric fuel :