Calculations of the Effect of Rate of Heat Release on the Shape of Cylinder-Pressure Diagram and Cycle Efficiency

Abstract

In these papers the gas pressure, temperature and cycle efficiency are calculated for various assumed simple heat-release diagrams using a digital computer. It is concluded from these calculations that for a given heat-release period, the cycle efficiency is essentially a single valued function of peak pressure and is independent of the actual shape of the diagram. There is an optimum peak pressure beyond which no gain in efficiency can be expected. The rate of pressure rise, however, depends on the initial slope of the heat release diagram. It is therefore both desirable and possible to have a slow rate of pressure rise for the same peak pressure with only slight loss in efficiency. The effect of compression ratio and the period of heat release have also been investigated. The theoretical cycle is then compared with what is regarded as the practically attainable ideal cycle. Finally, the optimum peak pressure for a given compression ratio, or alternatively the optimum compression ratio for a given peak cylinder pressure is defined.