The Development Of A Hd Diesel Engine Combustion System Based On EGR

In recent years, the rapid growth in number of vehicles in the world poses increasing pressure on energy and environment. The internal combustion engine emissions are the major source of urban air pollution. Therefore, many countries have proposed stringent regulations to limit engine emissions, which bring new challenges to the development of modern internal combustion engine. Exhaust gas recirculation is one of the key technologies to reduce emissions. This paper focuses on the development of a heavy duty diesel combustion system based on EGR and its impact on diesel engine performance and emissions.The research was conducted on a heavy-duty common rail diesel engine. Two EGR systems: venturi system and intake throttle system were tested to identify which is the better configuration. Result showed that adequate EGR rate can be achieved by applying the intake throttle system, as well as better fuel economy, therefore intake throttle system was chosen as the optimized EGR system. Based on this EGR system, further combustion system optimization was carried out; adjusted parameters include various turbochargers, combustion chambers and injectors. Results show that the turbocharger with smaller turbo flow area is conducive to realize EGR, while still maintaining relatively larger intake air flow, which helps to achieve better fuel economy and emissions. Better performance and emissions can be realized by applying higher compression ratio chamber (17); injector with smaller nozzle hole diameter is also helpful to reduce soot emission.Based on the former research results, experiments were conducted to investigate the effects of injection parameters (injection timing, multiple injections and injection pressure) on the performance and emissions. Results showed that emissions can be improved by optimizing injection timing; smoke can be significantly reduced by increasing injection pressure which can also improve the trade-off relation between NOx and smoke. Smoke can be effectively further reduced by post injection, especially at high-speed and high-load conditions.Final test results showed that through the optimization of combustion system based on EGR, on the promise that NOx meets State Stage IV legislation, soot emission can be reduced to much lower levels fuel economy could also be improved compared to the original engine. The result showed that by applying this EGR-based combustion system, it is possible to meet State Stage IV legislation with simplified aftertreatment devices (DOC/POC) and waste gate turbocharger.