Residual Gas Fraction Measurement and Estimation in Spark Ignition Engine

To meet future pollutant emissions standards, it is crucial to be able to estimate not only the cycle by cycle mass, but also the cycle by cycle composition of the combustion chamber charge. This charge consists of fresh air, fuel and residual gas from the previous cycle. Unfortunately, the residual gas fraction cannot be directly measured.

Therefore, an experimental method has been designed to determine the residual gas fraction. The method is based on an in-cylinder sampling method coupled with CO₂ analysis.

A residual gas fraction model as a function of engine parameters and operating parameters has been developed. The parameters of the model have been fitted on the experimental results.