A Parametric Study of the Exhaust Valve Requirements of High Output Truck Engines

The paper presents the first phase of a research project to study the relationship between valve design parameters and the performance of turbocharged truck engines.

The results discussed were produced by computer simulation of the diesel engine and its associated intercooler and turbocharger. Three aspects of exhaust valve design are studied : the rate of valve opening, the size of the exhaust valve in relation to the inlet valve and the timing of the exhaust valve opening event.

Rate of exhaust valve opening is found to be an important influence on exhaust pulse energy and may Drovide a means of increasing low-speed boost. Valve area ratio had only a small effect on engine performance over the range studied (0.8 ≤ A_I /A_E ≤1.2), whereas the timing of exhaust valve opening proved to be an important parameter, having a significant effect on the thermal efficiency of the system.