Combustion System Development of Direct-Injection Diesel Engine Based on Spatial and Temporal Distribution of Mixture and Temperature

Abstract

This study developed a Distributed Combustion Design (DCD) method, based on spatial and temporal distribution of mixture and temperature in cylinder, to optimize the combustion of high-pressure common-rail direct-injection diesel engine. Due to the significant improvements of fuel atomization and evaporation by high-pressure common-rail system, mixing control of fuel and air becomes a critical factor to improve efficiency and emissions. Bowl shape, spray angle, multiple-injection and swirl ratio are effective approaches to control the fuel distribution and movement in cylinder both spatially and temporally, therefore can be used to improve the mixing. The whole space in cylinder was divided into three zones, Chamber, UPcham and Outerclearance. And the start of combustion, the timing of injection impacting on bowl lip, the end of injection and the end of combustion were selected as critical timings for temporal zoning controls. Studies proved that the history of fuel quantity distributed to Chamber was an important parameter affecting mixture and temperature distribution, then thermal efficiency and emissions. Combustion and emissions histories and their relationship with mixture distribution were studied under different approaches and schemes and were validated by single cylinder optical engine tests. Furthermore, the DCD method was put forward. As a result of its application, 2 % reduction of fuel consumption was achieved on a 9 L diesel engine.

F2012-A06-048