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CFD simulations have been conducted to investigate the combustion in a direct-inject (DI) diesel engine using the Ricardo engine CFD program VECTIS and the Ricardo Two-Zone Flamelet (RTZF) combustion model. The simulation program covers full load and part load operating conditions, each including 6 to 7 cases forming an injection timing swing. CFD simulation results are compared against engine tests for the in-cylinder pressures and NOx emissions. The comparison shows that the RTZF combustion model performs well in all cases studied with no tuning of model coefficients necessary. The detailed time history of spray, fuel distribution and flame development obtained from the CFD simulation provides useful information towards gaining a better understanding of the features of combustion in DI diesel engines.

This paper describes the application of the Ricardo non-linear, one-dimensional engine performance simulation program, WAVE, to the problem of exhaust system design for the Chrysler 3.5 liter V6 24 valve engine. This computer-based analysis offers substantially reduced lead times over the ‘build and test’ methods traditionally employed. Furthermore, because tailpipe noise, engine performance and pressure loss are all predicted at the design stage, a more complete solution can be found. Comparisons between measured and predicted results are shown in this paper and the value of many alternative design changes are assessed. Digital sound synthesis techniques developed at Ricardo have also been used to assess the effect of design changes on the perceived sound. Based on this analysis recommendations were made to improve the exhaust system design and the paper concludes with a discussion of the implementation of these changes by Chrysler and Walker Manufacturing, the system supplier.