3D CFD combustion simulations of multiple injection strategies using two different injector concepts

Abstract

Consulta en la Biblioteca ETSI Industriales (9023)

[EN] Within the last decades, diesel engines have become the most used engine in trucks and buses and this trend is increasingly seen also in passenger cars. In terms of their superior fuel consumption, high torque at low speed as well as their durability and reliability, the high-speed direct injection diesel engine has become a realistic alternative for passenger car applications leading to its increasing popularity in the market place. Pollutant emissions produced by compression ignition engines are of concern to engine builders. Emission regulations are becoming more stringent year by year as interest in environmental issues grows. Over the last years, many Diesel engine researchers throughout the world have contributed greatly to the reduction of engine-out emissions in an effort to meet these governmental regulations in the most efficient ways possible. Efforts have been made to improve combustion, and recently there has been a trend to review and modify combustion types themselves. One way to meet the NOx requirement has been the employment of exhaust gas recirculation (EGR). However, in conventional Diesel combustion strategies, increased EGR causes the engine-out PM emissions to increase, creating the well-known trade-off relationship between NOx and soot. Other research studies focus on the fuel injection process since the quality of the combustion process is directly related to the quality of the fuel spray and the air-fuel mixture /5/. Improving the mixing process between fuel and air in direct injection compression engines can decrease both particulate and nitrogen oxides. That leads to the development of new and more sophisticated high pressure injection systems to more precisely control the injection process, such as those with rate-shaping or multiple injections strategies /1/ /2/ /3/ /4/. New generations of common rail fuel injectors, which make a higher injection pressure and a better response to the electric signal possible, in combination with exhaust gas recirculation are playing an important part in matching the emission target /6/.The complex task of studying the combustion in the engine in order to improve the process is nowadays carried out by a combination of advanced experiments and computational studies. In this field, three-Dimensional Computational Fluid is becoming increasingly important. This tool is used to better understand the in-cylinder processes such as mixture compression, fuel injection, heat release because of combustion and pollutants formation.