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.
