Quantitative Analysis of the Influence Saliency of VVA and EGR on the Fuel Economy and Mixture Combustion Characteristics of a Turbocharged Spark Ignition Engine.

To meet the stringent emission regulations and fuel economy demands of the spark ignition (SI) engine, more and more new technologies such as turbocharging, variable valve actuation (VVA), and exhaust gas recirculation (EGR) are being developed. For the turbocharged SI engine, the high boost pressure can lead to higher laminar combustion velocity with higher maximum burned gas temperature, which induces more emissions; it also carries a risk of serious knocking, which can not only deteriorate the brake-specific fuel consumption (BSFC) but also destroy the engine. As is well known, the dilution mixture gas methods, which include VVA and EGR, are effective techniques to advance the combustion phase and suppress knocking in the SI turbocharged engines. The effects of VVA and EGR rates on the BSFC and combustion characteristics of an SI engine were analyzed through 100 groups of engine experiments, and the quantitative analysis of the influence saliency of VVA and EGR rates has been introduced. Then, the optimal level of each factor was obtained by a comprehensive balance method. The results indicated that the EGR rate has the most significant influence on the BSFC and CA50. At the same time, the BSFC was only 211.7 g/kWh, which has been improved significantly, and CA50 was 12.55° CA ATDC, which effectively enhances the knock resistance when applying the optimization parameters.