Influence of premixed charge compression ignition and direct injection combustion on engine performance

The study on the influence of partial premixed charge compression ignition-direct injection(PCCI-DI) compound combustion on engine performance such as brake thermal efficiency and emission was experimentally conducted in a 2105 engine. In the experiment, PCCI-DI combustion was realized by the way that the partial homogeneous mixture composed of the pilot DME and air entered a combustion chamber through the intake pipe and diesel fuel was directly injected into the combustion chamber with the fuel injection equipment of the compression ignition engine at the terminal stage of a compression stroke. Experimental results show that, compared with the conventional compression ignition combustion, both NO_x and smoke emission decreased and the brake thermal efficiency rised, however, HC and CO emissions were significantly higher with PCCI-DI combustion at low and medium speed and load. In addition, NO_x emission decreased slightly and smoke emission decreased by 30%-40% with an increase in DME premixed ratio.