A Study on Practical Utilization of Diesel Combustion Calculation (Second Report)

- An Improvement Approach for Exhaust Gas Estimation -

Abstract

A chemical reaction calculation with a reduced chemical elementary reaction model brought us to predict ignition delay time precisely because of considering slight heat release from the low temperature oxidization reaction. That enables us to estimate precise in-cylinder pressure. The low calculation speed which is a serious defect of the chemical calculation was drastically improved by the high speed calculation algorithm in our previous paper. It can be expected that some engine adaptation works are supported by using this CAE technique, when some reliable exhaust gas estimation procedures are provided. The Hiroyasu-NSC(Nagle and Strickland-Constable) model for the soot generation and oxidization process and the extended Zeldovich mechanism for NO(nitric monoxide) had already been introduced in our calculation code, but the both didn’t work so well in some partial engine operating conditions. Therefore the soot estimation is improved by introducing an orthogonality technique into the calculation mesh generation and revising the calculation mesh density. Those help to reduce artificial viscosity and replicate real flow properties around the wall, and eventually the proper amount of soot generation and oxidization can be obtained. We are trying to improve the NO estimation with a prompt NO model. The overview of calculation methods and some calculation results are shown here.