In-Cylinder Fuel Evaporation and Heat Transfer Information Inferred from the Polytropic Character of the Compression Stroke in a Spark-Ignition Engine

In the absence of accurate in-cylinder temperature measurements it is difficult to quantify the extent of in-cylinder fuel evaporation present in carburetted spark ignition engine. This paper reports on the analysis of the polytropic coefficient during the compression stoke in a CFR engine running on propane and a variety of liquid fuels, in addition to being motored without fuel. The inferred heat loss rate calculated from the polytropic coefficient allowed for optimisation of the form and parameters in a theoretical heat transfer model. By assessing the total inferred latent heat loss during liquid fuel operation, it was possible to quantify the extent of the in-cylinder fuel evaporation. The in-cylinder heat loss was correlated with the fuel volatility and latent heat of evaporation.