In-cylinder Heat Transfer at a Low Flow Region on the Cylinder Head of a Direct Injection Diesel Engine

Abstract

This paper introduces a new approach to model in-cylinder convective heat transfer at a low flow region on the cylinder head of a diesel engine. Previous convective heat transfer model predicts that the heat flux should be low at a low flow region. However, experimental results indicate that the heat flux at a low flow region is not significantly lower than the heat flux at a high flow region. A new model is proposed which is based on solving the turbulent kinetic energy from two coupled k-ϵ equations and the results are matched with the law-of-the-wall relations to obtain an equivalent velocity. The equivalent velocity is substituted into a Colburn analogy relation to obtain the convective heat transfer coefficient and then the convective heat flux. A radiative heat transfer model previously established by the authors is also briefly outlined. The simulated total heat flux, ie. convective heat flux plus radiative heat flux, are found to match with experimental results.