Experimental Study of High-Pressure Reacting and Non-reacting Sprays for Various Gasoline Blends

Abstract

Research into efficient internal combustion (IC) engines need to continue as the majority of vehicles will still be powered by IC or hybrid powertrains in the foreseeable future. Recently, lean-burn gasoline compression ignition (GCI) with high-pressure direct injection has been receiving considerable attention among the research community due to its ability to improve thermal efficiency and reduce emissions. To maximize GCI benefits in engine efficiency and emissions tradeoff, co-optimization of the combustion system and fuel formation is required. Thus, it is essential to study the spray characteristics of different fuels under engine-like operating conditions. In this work, high-pressure spray characteristics are experimentally studied for three blends of gasoline, namely, Naphtha, E30, and research octane number (RON) 98. A single-hole custom-built injector was used to inject fuel into a constant volume chamber with injection pressure varying from 40 MPa to 100 MPa. The chamber pressure was varied from 4 MPa to 7 MPa. The spray parameters measured were liquid and vapor penetration, liquid and vapor spray plume angle, and spray and flame luminosity area for reacting and non-reacting sprays. The measurement techniques used were shadowgraphy, Schlieren method, and flame luminosity area measurement. Liquid penetration followed the fuel density pattern and was shortest for Naphtha, followed by RON 98 and E30. The increase in injection pressure did not significantly affect liquid penetration, but improved atomization as well as reduced soot intensity. In addition, vapor penetration was increased on account of higher injection velocity and vaporized mass. The higher chamber pressure drastically reduced liquid and vapor penetration on account of increased drag. Compared to non-reacting sprays, vapor penetration and spray plume angle for reacting sprays deviated according to the fuel type. Ignition of the fuel increased vapor penetration and spray plume angle due to the expansion of hot gases. Naphtha ignited the earliest on account of its low RON and high volatility. It had the highest deviation from the corresponding non-reacting case for vapor penetration. RON 98 fuel only showed a slight increase in vapor plume angle indicating the start of reaction, whereas E30 did not show any deviation.