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The requirement of reduced emissions and improved fuel economy led the introduction of direct-injection (DI) spark-ignited (SI) engines. Dual-fuel injection system (direct-injection and port-fuel-injection (PFI)) was also used to improve engine performance at high load and speed. Ethanol is one of the several alternative transportation fuels considered for replacing fossil fuels such as gasoline and diesel. Ethanol offers high octane quality but with lower energy density than fossil fuels. This paper presents the combustion characteristics of a single cylinder dual-fuel injection SI engine with the following fueling cases: a) gasoline for PFI and DI, b) PFI gasoline and DI ethanol, and c) PFI ethanol and DI gasoline. For this study, the DI fueling portion varied from 0 to 100 percentage of the total fueling over different engine operational conditions while the engine air-to-fuel ratio remained at a constant level.

This paper focuses on the numerical investigation of the mixing and combustion of ethanol and gasoline in a single-cylinder 3-valve direct-injection spark-ignition engine. The numerical simulations are conducted with the KIVA code with global reaction models. However, an ignition delay model mitigates some of the deficiencies of the global one-step reaction model and is implemented via a two-dimensional look-up table, which was created using available detailed kinetics models. Simulations demonstrate the problems faced by ethanol operated engines and indicate that some of the strategies used for emission control and downsizing of gasoline engines can be employed for enhancing the combustion efficiency of ethanol operated engines.

An experimental study is performed to investigate the fuel impingement on cylinder walls and piston top inside a direct-injection spark-ignition engine with optical access to the cylinder. Three different fuels, namely, E85, E50 and gasoline are used in this work. E85 represents a blend of 85 percent ethanol and 15 percent gasoline by volume. Experiments are performed at different load conditions with the engine speeds of 1500 and 2000 rpm. Two types of fuel injectors are used; (i) High-pressure production injector with fuel pressures of 5 and 10 MPa, and (ii) Low-pressure production-intent injector with fuel pressure of 3 MPa. In addition, the effects of split injection are also presented and compared with the similar cases of single injection by maintaining the same amount of fuel for the stoichiometric condition. Novel image processing algorithms are developed to analyze the fuel impingement quantitatively on cylinder walls and piston top inside the engine cylinder.