Numerical study of the effects of split injection strategy and swirl ratio for biodiesel PCCI combustion and emissions

Abstract

New methods have been studied in the past few decades to decrease exhaust emissions and fuel consumption of diesel engines. Using new combustion methods as low-temperature combustion (LTC) strategies and also utilizing new fuels as bio-diesel are beneficial ways to overcome diesel engine issues. This numerical study focused on the effect of split injection strategies as well as swirl ratio (SR) on the biodiesel premixed charge compression ignition (PCCI) combustion process and the related emissions. In this regard, KIVA-3V code as a CFD tool has been utilized to analyze the combustion and emission characteristics of the diesel engine. Single and split injection strategies have been executed on biodiesel PCCI combustion and have been compared in order to probe and examine the injection strategies. The results show that in both strategies, advancing the injection timing can lower the combustion emission and improve the engine performance by optimizing the start of injection (SOI) as sweet spot value. Utilizing a high swirl ratio with the split injection strategy has a negative effect on overall combustion, emission, and performance in comparison with the single injection strategy. For multi-injection scheme, SOI = −35 ATDC, SR = 1.1, and for single injection scheme, SOI = −40 ATDC, SR = 1.1 are considered as optimum cases regarding minimum total exhaust emissions and highest performance.