Experimental study of NOx emissions and injection timing of a low heat rejection diesel engine

In this study, an experimental study of the effects of injection timing on nitrogen oxide (NOx) emissions of a low heat rejection (LHR) turbocharged direct injection diesel engine was conducted. The injection timing and brake specific fuel consumption (BSFC) trade-off must be considered together in performance and NOx emissions analysis. For the original injection timing of the 20° before top dead centre, the brake specific fuel consumption value of the LHR engine was approximately 6% lower than the original engine. NOx emissions were also higher (about 9%) than the original engine. To reduce NOx emissions released by diesel engines, the method of injection timing retard was utilized. Thus, the LHR engine was tested for two different injection timings; 18° and 16° crank angle before top dead centre (BTDC), at the same engine speeds and load conditions. The results showed that the BSFC and NOx emissions were reduced 2% and 11%, respectively by retarding the injection timing. Optimum injection timing for the LHR engine was obtained through decreasing by 2° BTDC.