Study On The Spray Characteristics Of Ethanol Blended Fuel

The study of the spray process of liquid fuel is an important way to improve the combustion efficiency and stability,reduce pollutant emission and prolong the service life.The consumption and ecological destruction of fossil fuel can be largely reduced by the wide using of biofuel.The spray characteristics of ethanol-diesel,ethanol-aviation kerosene and ethanol-biodiesel blended fuel had been experimentally studied in this article.The major work may be summarized as the follows:The experimental platform and image processing program had been designed and constructed for the spray test.The platform includes three parts:High-pressure common-rail injection system can provide the fuel injection pressure from 30MPa to 150MPa for the multiple fuels.Visualization pressure device can provide the ambient pressure from latm to 12MPa and the ambient temperature from room temperature to 500K.High-speed CCD schlieren optical system can measure and record the comprehensive spray process."High-speed Photography Schlieren Image Processing"program had been written to process and analysis a series of experimental data.The spray characteristics of ethanol blended fuel had been studied in this article.The influences of the ethanol blended ratio,injection pressure and ambient pressure on the spray characteristics of ethanol-diesel blended fuel had been studied under low pressure environment.Then,the spray characteristics of ethanol-aviation kerosene blended fuel had been studied under the transcritical pressure environment.At last,the influence of the ambient temperature and ambient pressure on the spray characteristics of ethanol-biodiesel blended fuel had been studied.The results showed that the spray tip penetration and velocity were significantly increased with the increase of the injection pressure,but the spray cone angle would not change too much.With the increased of the ambient pressure,the spray tip penetration and velocity were reduced and the spray cone angle was increased due to the resistance to the spray transverse and axial diffusion.The liquid-phase penetration was linearly increasing with the increase of ambient temperature due to the evaporation process.In addition,the fragmentation degree and distribution uniformity of the droplets had been improved with the addition of ethanol for the high viscosity liquid fuels such as diesel and biodiesel.According to a lot of experimental spray data of the blended fuel,the coefficient of empirical formula had been fitted and corrected to present the non-evaporation spray calculation modified model based on the Hiroyasu model and the evaporation spray calculation modified model based on Siebers and Dent models.The spray tip penetration,spray cone angle and spray tip velocity of the ethanol-diesel and ethanol-aviation kerosene blended fuel were calculated and verified by using the non-evaporation spray model.The results showed that the model can accurately reflect the change trend of the spray cone angle and the calculation of spray tip penetration reflected higher precision in dense spray environment.In addition,the calculated values of the model for spray tip penetration and the tip velocity were more consistent with the experimental results in the late injection.The formula coefficients of the evaporation spray model for the calculation of the liquid-phase and gas-phase penetration and spray cone angle were modified and verified for the ethanol-biodiesel blended fuel.The undetermined coefficients of the formula for calculating the spray gas-phase and liquid-phase penetration were obtained through the analysis of a lot of experimental data respectively.The coefficient of the calculation formula of spray cone angle was obtained based on a large amount of experimental data,which was increasing with the increase of ethanol blended ratio.The results showed that the modified model can accurately calculate the spray penetration and spray cone angle of the blended fuel under various working conditions.It can be concluded that the addition of appropriate proportion of ethanol would not have a huge negative impact on the spray characteristics.In other words,the application of ethanol blended fuel of appropriate proportion can be carried out without changing the combustor structure.In addition,the calculation modified models,which were proposed in this article for the prediction of relative characteristic parameters,showed commendably consistant with the experimental results.Thus,they can be directly adopted to calculate the spray process of ethanol blended fuel.