We have investigated a fuel spray from a multi-hole nozzle under gasoline port fuel injection conditions, the classification of the spray using dimensionless numbers in fluid dynamics is estimated to be in the wave like breakup region. In this study, shadowgraph photography was used to visualize the sheet breakup process of the gasoline spray. It was confirmed that the fuel formed a liquid sheet and broke up into droplets with a distribution along the axial distance from the nozzle. Also, the effects of the nozzle angle and differential injection pressure on the dynamic characteristics of fuel droplets were investigated by applying Particle Tracking Velocimetry (PTV) analysis. From these results, the direction and dispersion of droplets propagation are affected by the nozzle angle and differential pressure of injection.
In a direct-injection gasoline engine, strict control of pollutant emissions at cold start is a critical point to comply with new regulations, and the fuel film formed by spray impingement on the piston wall is closely related. In this context, the purpose of this study is to clarify the fuel film formation process of spray impinging on a low temperature wall. Total internal reflection laser induced fluorescence (TIR-LIF) method was applied to the fuel film formed by wall impingement gasoline spray. TIR-LIF method can measure the fluorescence from fuel film without the influence of the spray droplet. The fluorescence intensity from the fuel film depends on the film thickness and temperature. In this paper, the temperature dependence of the fluorescence from the fuel film was investigated under the condition that the laser light is totally reflected from the top surface of the film. The order of magnitude of the heat transfers due to the mixing of spray droplets and fuel film, the heat transfer from the ambient gas, and the heat transfer from the wall were compared and modeled. A method to simultaneously calculate the unsteady change in fuel film thickness and fuel film temperature was developed. Then, the model analysis method was applied to the measured experimental data and verified.
A breakup model used in spray combustion simulations was developed to predict the breakup process of spray droplets, which has large influences on the mixture formation and the combustion process in internal combustion engines. Taylor Analogy Breakup (TAB) Model is widely used as a droplet breakup model. Improved TAB (ITAB) Model has been developed by improving model constants and the breakup/non-breakup boundary condition of TAB Model. ITAB Model reproduces the dimensionless breakup time based on the observation results of the single droplet breakup behavior and CFD simulation results. In this study, calculation methods of droplet diameter and droplet velocity after breakup in ITAB Model are modified to avoid fitting model constants during spray analysis. Droplet diameter after breakup is determined by calculating Sauter Mean Diameter and using the droplet diameter distribution after breakup based on the observation results of the single droplet breakup behavior. The calculation constant for Sauter Mean Diameter is a function of Weber number to reproduce the breakup phenomenon of single droplets. Droplet velocity after breakup is calculated based on the energy conservation law of droplets used in Enhanced TAB Model. This model shows that Sauter Mean Diameter after breakup is almost same and perpendicular motion of droplets after breakup is more active than TAB Model. This model also considers the effects of the fuel physical properties on breakup characteristics. Model analysis shows that droplet diameter after breakup of the high boiling point component fuel is larger under same conditions and the effect of temperature change is larger than that of the low boiling point component fuel.
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