The Limits of Engine Performance — Comparison of Actual and Theoretical Cycles

The limits on reciprocating engine performance are set by the idealized constant-volume cycle. Heretofore, fuel-air cycles have been computed by tracing them out on thermodynamic charts -- a long and tedious process. By programming the thermodynamic characteristics of the fuel-air media and the cycle processes on a digital computer, it has been possible to compute the characteristics of fuel-air cycles over a wide range of fuel-air ratios, compression ratios, and initial conditions and present the results in graphic form.

The results are used to compute equivalent theoretical cycles for comparison with real engine performance.

The ratio of actual to ideal thermodynamic performance of engines can be computed using equivalent cycles. The method to evaluate engine performance is illustrated, and a number of actual cycles are compared with their equivalent fuel-air cycles, and losses are considered.