Search Results

This paper presents a combined experimental and computational study of steady flow through a curved inlet port. Three-dimensional flow within the port and cylinder for the intake process has been simulated using the CFD code STAR-CD. Flow structures affected by the valve lift and port shape were predicted. Local static surface pressure was measured on a twice full size model of the port, valve and cylinder assembly. The static pressure maps from both measurement an computation provide detailed information on the intake port flow. The numerical predictions show an appreciable pressure recovery for a favourable flow passage between the valve seat and the valve head, which confirm earlier port design procedures. An optimum valve size for the present curved port was explored.

The Computational Fluid Dynamics (CFD) code KIVA has been modified to include a combustion model and the Shell autoignition mechanism, and has been applied to a disk-chambered homogeneous charge spark ignition engine. The effects of ignition timing, turbulent kinetic energy and EGR were investigated for offset ignition. The effects of swirl and central ignition were separately investigated. For the central ignition case the influence of asymmetry of piston and cylinder head surface temperatures was also considered. The results of the computational study are in general agreement with experimentally observed trends regarding heat release rate and phasing and their influence on cylinder pressure development, autoignition and knock. With the CFD code it was possible to observe, following autoignition, large amplitude pressure waves and acoustic resonant modes in the combustion chamber, which are generally in agreement with the published literature.

This paper describes the application of the discrete transfer model of thermal radiation in the engine CFD code KIVA for the simulation of diesel combustion and heat transfer. The comprehensive modelling of flows and heat transfer in engines requires accurate evaluation of transient temperature and radiation properties of the gaseous combustion products. A submodel for autoignition chemistry and a soot formation and oxidation model have been incorporated in the general computational fluid dynamics procedure, and Hottel's mixed grey and clear gas concept has been used to evaluate emissivities. Results of calculations are presented for engine aerodynamics, cylinder pressure and temperature, soot concentration, and radiative heat fluxes. Radiative heat fluxes have been compared with data, in similar experimental engines. Comparisons between the predictions and data show encouraging agreement.