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In internal combustion engines, liquid fuel injection is one of the most prevalent means of fuel delivery and air-fuel mixture preparation. The behavior of the fuel spray and wall film is a key factor in determining air-fuel mixing and hence combustion and emissions. A comprehensive model for the liquid fuel spray has been developed in conjunction with the one-dimensional gas flow code WAVE. The model includes droplet dynamics and evaporation, spray-wall impingement, wall film dynamics and evaporation. The fuel injector can be placed in the manifold, inlet port or cylinder. Liquid fuel droplets are injected with a prescribed size distribution, and their subsequent movement and vaporization are modeled via the discrete particle approach, frequently used in multi-dimensional CFD codes. This approach ensures conservation of mass, momentum and energy between the gas and liquid phases.

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.

The common method for achieving less than full power operation in a spark ignition (SI) engine is reducing charge density via a throttle. However, a significant fuel economy penalty is associated with the pumping losses across the throttle valve. An alternative method to aid in reducing fresh charge density has been investigated on an Oldsmobile Quad-4 engine: exhaust gas recirculation in combination with inlet air heating. Brake thermal efficiency gains of about 6% were realized. The exhaust hydrocarbon increases associated with EGR were mitigated largely by inlet air heating.