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Direct-injection spark-ignition (DISI) engines have been investigated for many years but only recently have shown promise as a next generation gasoline engine technology. Much of this new enthusiasm is due to advances in the fuel injection system, which is now capable of producing a well-controlled spray with small droplets. A physical understanding of new combustion systems utilizing this technology is just beginning to occur. This analytical and experimental investigation with a research single-cylinder combustion system shows the benefits of in-cylinder gasoline injection versus injection of fuel into the intake port. Charge cooling with direct injection is shown to improve volumetric efficiency and reduce the mixture temperature at the time of ignition allowing operation with a higher compression ratio which improves the thermodynamic cycle efficiency.

A modified CFR Cetane engine was used to analyze combustion characteristics and emissions of minimally processed coal liquids (MPCLs). To aid in combustion of the coal liquids, the ability to heat the fuel and inlet air was added. The MPCLs are derived from atmospheric distillation of coal liquids. The coal liquids are byproducts of coal gasification of Elkhorn bituminous and North Dakota lignite using the atmospheric, air blown Wellman-Galusha and pressurized, oxygen blown Lurgi gasifiers, respectively. The MPCLs were compared with three reference fuels: diesel No. 2, U12 (21 cetane number) and #-methyl napthalene (0 cetane number). The inlet air was heated from 340 to 535 K and the compression ratio was varied from 13 to 31 to provide sufficient range in temperature and pressure necessary for the combustion of low cetane number fuels. At each operating condition, fuel consumption, cylinder pressure, ignition delay, and emisions were measured.