Quantitative Investigation of the Effects of EGR and Spark Timing Strategies on Performance, Combustion and Emissions Characteristics of Atkinson Cycle Engine

Abstract

To study the effects of exhaust gas recirculation (EGR) and spark timing strategies on performance, combustion and emissions characteristics of Atkinson cycle engine, the experimental test was conducted and evaluated under operating condition of the engine speed of 2800 r/min and the load of 6 bar by changing EGR rate and spark timing angle (SA). The main results are listed that (a) both the in-cylinder pressure and heat release rate (HRR) are decreased with the increase of EGR rate, while increase with increased SA. The EGR could not be higher due to the misfire phenomenon, but increasing the SA could solve this problems. (b) There is optimal SA that the brake thermal efficiency (BTE) is the highest and the brake specific fuel consumption (BSFC) is the lowest. The highest BTE is almost the same in different EGR rate, and is similar to the change trends of effective expansion ratio (EER) and effective expansion efficiency (EEE). (c) The NOx emissions increase linearly and sharply with the increase of EGR, and decrease with the increase of spark timing, the amount of nitric oxide metabolite (NOx) without EGR is 8 times about the amount NOx of 13% EGR. In a word, increasing the SA is good way of increasing the in-cylinder pressure and temperature. Furthermore, the data could be used to evaluate and optimize the performance through changing different technologies or adding optimization methods in the future.

Keywords: EGR and spark timing strategies, EER, performance, Emissions, Atkinson cycle engine