Port throttles applied to a high-performance 4-valve S.I. engine.

摘要

The first section of this thesis includes a Literature Survey. This review covers the basics of SI engine operation and details the combustion process, looking at the formation of pollutants in particular. The reasons for adopting 4-valve cylinder heads are discussed and their inherent weaknesses are detailed. Current techniques for improving engine performance and reducing emissions are discussed, before assessing the work that has already been carried out on port throttles. As pan of the research programme, a computer model was developed for predicting engine behaviour with port throttles. The theory behind the model is covered in detail. A period of engine testing was undertaken to validate the computer program, and the results are included in this section. The way in which the model was used in optimizing the throttle design is also discussed later in a parametric survey. Engines running with increased valve overlap have also been considered. A port throttle assembly was designed and built for engine testing at Ford's Research Centre. A steady-flow rig was also set up to assess the effect that port-throttles have on in-cylinder air motion. Results from these tests are discussed, showing that a slight change in design to the throttle assembly could lead to improved engine performance. Engine testing at Ford involved full exhaust gas analysis. Several throttle configurations were investigated, and the effect that these changes have on emission levels is discussed in detail. The tests highlighted the possibilities for using port throttles in conjunction with lean burn technology. In the final section, the future for port throttles is covered and conclusions from the research programme are discussed, including the author's suggestions for future investigations.