The effects of injection timing on NOx emissions of a low heat rejection indirect diesel injection engine

Abstract

Higher NO, is one of the major problems to be overcomed in a low heat rejection (LHR) diesel engine as insulation leads to an increase in combustion temperature about 200-250 degrees C compared to an identical standard (STD) diesel engine. High combustion temperatures alter optimum injection timing of a LHR engine. With the proper adjustment of the injection timing, it is possible to partially offset the adverse effect of insulation on heat release rate and hence to obtain improved performance and lower NOx. However, the injection timing and brake specific fuel consumption (BSFC) trade-off must be considered together in performance and NO., emission point of view. In this study, optimum injection timing was found with 4 crank angle (34 degrees CA) retarded before top dead centre (BTDC) in LHR diesel engine in comparison to that of STD diesel engine (380 CA BTDC). When the LHR engine was operated with the injection timing of the 38 crank angle, which is the optimum value of the STD engine, it was shown that NOx emission increased about 15%. However, when the injection timing was retarded to 34 degrees CA in the LHR case, it was observed a decrease on the NOx emissions with about 40% and the brake specific fuel consumption (BSFC) with about 6% compared to that of the STD case. Thus, by retarding the injection timing, an additional 1.5% saving in fuel consumption was obtained. (c) 2005 Elsevier Ltd. All rights reserved.