Evaluation of reactivity controlled compression ignition mode combustion engine using mineral diesel/gasoline fuel pair

Abstract

Stricter emission norms, scarce availability of conventional fuel resources, and moderate engine efficiency are primary concerns for both spark ignition (SI) and compression ignition (CI) engines. The use of advanced low-temperature combustion technologies can resolve these issues, amongst which reactivity-controlled compression ignition (RCCI) mode combustion has emerged as an important one. RCCI mode combustion exhibits significantly lower exhaust emissions (oxides of nitrogen [NOx] and particulate matter [PM]) compared to CI mode combustion and delivers higher BTE compared to SI mode combustion. In this study, RCCI mode combustion has been investigated in a single-cylinder research engine using gasoline and mineral diesel as low reactivity fuel (LRF) and high reactivity fuel (HRF), respectively. Experiments have been performed at different premixed ratios of LRF (premixed ratio [rp] = 0, 0.25, 0.50, and 0.75) and four-engine loads (1 bar to 4 bar BMEP) at a constant engine speed of 1500 rpm. The use of gasoline in RCCI mode combustion resulted in relatively smoother RCCI mode combustion compared to baseline CI mode combustion. The presence of low reactivity gasoline led to a slightly retarded start of combustion (SoC) and combustion phasing (CP), which improved the performance of the RCCI mode combustion engine. RCCI mode combustion produced relatively lower NOx emissions compared to baseline CI mode combustion. However, hydrocarbon (HC) and carbon monoxide (CO) emissions from RCCI mode combustion were significantly higher than the CI mode combustion. Lower PM emissions from RCCI mode combustion was an important observation of this investigation. Qualitative correlations between different parameters such as PM number and mass-size distributions, total particulate mass (TPM)-NOx, etc., revealed that RCCI mode combustion was capable of simultaneous reduction of NOx and PM, which is otherwise difficult in conventional CI mode combustion engines