Rate of heat release characteristics of supercritical sprays of dieseline blend in constant volume combustion chamber

In present experimental study, combustion characteristics of homogeneous supercritical (SC) fuel spray injection system are analyzed in cylindrical constant volume combustion chamber (CVCC) at experimental conditions similar to diesel engine-like operating conditions. A comparative study is also performed between SC fuel spray and normal diesel spray combustion under similar conditions. Combustion characteristics of SC fuel sprays includes rate of heat release (ROHR) and peak pressure (PP). Operating parameters include hot surface temperature range (673 K-723 K), pre-firing cylinder air pressure range (20 bar-40 bar) and injection pressure (IP) range of 100 bar-300 bar. Piezoresistive pressure transducer is employed for indicating and recording combustion processes. Diesel fuel and dieseline blend (50% gasoline and 50% diesel by v/v) are used for normal diesel spray and SC spray combustion respectively. It is found that ROHR in SC fuel spray combustion is smaller than in normal diesel spray combustion at all operating conditions. In SC fuel spray combustion, ROHR increases with increase in IP but decreases with increase in HST and CP due to homogeneous and hot air combustion nature of SC fuel sprays. Percentage reduction in ROHR of SC fuel spray combustion as compared to ROHR in normal diesel spray combustion is found to be nearly 34% at normal operating conditions of diesel engine. PP reached during SC spray combustion is noted to be less than PP reached during normal diesel spray combustion in all cases and is responsible for reduced NOx formation in SC spray combustion.