Abstract

Spray-wall impingement is a widespread phenomenon applied in many fields, including spray-wall cooling system, spray coating process and fuel spray and atomization in internal combustion engines. In direct-injection spark ignition (DISI), it is difficult to avoid the fuel film on the piston head and cylinder surfaces. The wet wall caused by impingement affects the air-fuel mixture formation process, which finally influence the subsequent combustion efficiency and performance. Therefore, the fuel spray and impingement under gasoline engine-like conditions were characterized. Mie scattering technique was applied to visualize the spray evolution and impingement processes in a high-pressure and high-temperature constant chamber. Meanwhile, the adhered fuel film on the wall was measured by refractive index matching (RIM) under non-evaporation and evaporation conditions considering the effects of different injection pressures, ambient pressures and ambient temperatures. Additionally, the fuel film formation and evaporation evolution models were proposed with the help of these mechanisms.

Highlights

  • Compared to port fuel injection (PFI) engine, direct-injection spark ignition (DISI) engines as a greatly potential alternative become more and more widely used for their significant advantages [1, 2]

  • The impingement affects the fuel-air mixture prior to combustion, which is a possible source for unburned hydrocarbon (UHC) and particulate matters (PM) [3]

  • Tanaka et al [4] showed the relationship between the deterioration ratio of engine particle number (PN) emissions and fuel film volume, indicating that PN emissions increases with the increasing of fuel film on the wall

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Summary

Introduction

Compared to port fuel injection (PFI) engine, direct-injection spark ignition (DISI) engines as a greatly potential alternative become more and more widely used for their significant advantages [1, 2]. Under the high injection pressure condition, the cavitation and turbulence are generated from the injector holes, which should be the main reason for this mechanism. By considering the competitions from the pure electric vehicle (EV) and concerns on environmental pollution, it is urgent to understand the interaction of liquid droplet and piston wall thoroughly to improve the spray atomization in engine work process. Analyze the impinging spray evolution characteristics which belongs to the single-hole nozzle under the non-evaporation and evaporation conditions. Mie Scattering technique was implemented to obtain the observations of gasoline spray emerging from single hole injector under different conditions. RIM technique was adopted to analyze the formation process of fuel liquid on the wall qualitatively and quantitatively under both non-evaporation and evaporation conditions

Experimental apparatus and measurement methods
Mie scattering method
Effect of temperature
Effect of injection pressure
Effect of ambient pressure Figure 17 shows the S under different ambient pressures, with results of
Fuel film evaporation characteristics
Findings
Conclusions

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