The Idealized Limited-Pressure Compression-Ignition Cycle: An Empirical Treatment of Its Response to Varying Operating Parameters

A computation of the idealized compression-ignition cycle with the aid of thermodynamic charts does not produce speedy and accurate results because (a) the procedure involves laborious trial-and-error methods, and (b) the charts available do not cover the whole range of mixture strengths at which this type of internal combustion engine may operate. It is shown in this paper that existing thermodynamic charts may be used to develop empirical equations for efficiency, work output, and mean effective pressure of the cycle for a range of mixture strengths and, in general, with improved accuracy. The equations are presented in the form of nomographs enabling performance to be estimated for compression-ignition or “Diesel” engines of unsupercharged design and operating on the mixed cycle.