A Study of Fuel Impingement Analysis on In- Cylinder Surfaces in a Direct-Injection Spark- Ignition Engine with Gasoline and Ethanol-Gasoline Blended Fuels

An experimental study is performed to investigate the fuel impingement on cylinder walls and piston top inside a directinjection 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. Qualitative details of spray tip penetration are also presented to reveal the effects of ethanol fuels compared to that of gasoline. It is found that the split injection is an effective way to reduce the overall fuel impingement on in-cylinder surfaces. No significant difference is observed on fuel spray pattern when gasoline is compared with E50 and E85. However, spray tip penetration is slightly higher with gasoline than that of ethanol fuels. Results also show that the wall impingement is higher with gasoline compared to ethanol fuels. INTRODUCTION Improvement in fuel efficiency and reduction in exhaust emissions are the main goals behind the new developments in internal combustion (IC) engines. The concept of directinjection spark-ignition (DISI) engine has the potential to achieve such goals. In this technology, fuel is directly injected into the engine cylinder, which offers great flexibility to control the fuel injection timing, its duration and the number of injections. Note that the fuel-air mixture preparation in the combustion chamber is one of the key factors that influences the in-cylinder combustion characteristics and hence the engine performance (Hung et al., 2007). Therefore, optimizing the fuel-air mixture homogeneity is an important parameter for the engine designers. In general, a homogeneous fuel-air mixture is achieved by injecting the fuel during the intake stroke. However, due to in-cylinder injection and higher injection pressures, the fuel impingement levels on in-cylinder surfaces in DISI engines are typically higher than those in port-fuel injection (PFI) engines (Pereira et al., 2007). This results in an increase in the levels of un-burned hydrocarbons and smoke emissions, which reduces the potential fuel economy benefits associated with the direct-injection engines. Therefore, it is important to control the fuel injection timing precisely in order to minimize the fuel impingement on incylinder surfaces. Several studies have been reported on fuel spray pattern visualization and its influence on mixture formation inside the cylinder of direct-injection systems. Grimaldi et al. (2000) A Study of Fuel Impingement Analysis on InCylinder Surfaces in a Direct-Injection SparkIgnition Engine with Gasoline and Ethanol-Gasoline Blended Fuels 2010-01-2153 Published 10/25/2010