Residual gas fraction measurement and computation

Abstract

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. Two experimental methods have been designed to determine the residual gas fraction. The reference method is based on an in-cylinder sampling method. The second one is based on a hydrocarbon (HC) analysis of the exhaust gases. Two models have been compared to the experimental results. A one-dimensional computational fluid dynamics (CFD) code (WAVE) and a zero-dimensional model (AMESIM), which takes into account gas compressibility. The aim of the study was to compare the results of CFD codes (one- and zero-dimensional) to experimental results. If the code is validated by the experiments, it should be possible to determine residual gas fractions without needing a large experimental set-up.