Comprehensive analysis of combustion behaviors of hydrogen (H2)/diesel reactivity-controlled compression ignition (RCCI) in a light-duty diesel engine
Huiquan Duan, Ming Jia, Zhen Xu, Yaopeng Li, Guangqing Xia
Abstract
In this study, a comprehensive analysis of the combustion behaviors of hydrogen (H 2 )/diesel reactivity-controlled compression ignition (RCCI) was conducted toward the achievement of reliable and flexible combustion control of H 2 RCCI. The interplay between H 2 and the direct-injection (DI) high-reactivity fuel in RCCI combustion was revealed under various operating conditions, and the potential of H 2 /diesel RCCI in enhancing engine performance was excavated. The results suggested that under the single DI strategy, the maximum indicated thermal efficiency (ITE) of H 2 RCCI is considerably higher than that of gasoline RCCI. Compared with the single DI strategy, using the double DI strategy can significantly improve ITE and nitrogen oxides (NO x ) emissions simultaneously for H 2 /diesel RCCI. Under the double DI strategy, the ignition and combustion of H 2 are more sensitive to intake boost than gasoline in RCCI. Meanwhile, compared with gasoline, H 2 can inhibit to some extent the low-temperature heat release from the DI high-reactivity fuel in RCCI. By evaluating the emission performance of H 2 /diesel RCCI under different double DI strategies, it was found that NO x emissions of H 2 /diesel RCCI are mainly dominated by the homogeneity of the DI fuel/air mixture but not the combustion rate. In addition, increasing the premixed ratio can effectively improve combustion stability, ITE, NO x , and soot simultaneously with reduced peak pressure rise rate for H 2 /diesel RCCI. Attributed to the absence of carbon elements in H 2 , the soot emissions of H 2 RCCI are considerably lower than that of gasoline RCCI.