Investigation Of Spray Characteristics Of Ethanol Gasoline Under Flash Boiling And Injector Deposit Condition

In order to improve the internal combustion quality of the engine and ensure energy security,ethanol gasoline has been widely promoted in my country.The increasingly stringent emission legislation casts the demand for higher fuel atomization effect in gasoline direct injection(GDI)engines.As a promising method to improve atomization of fuel,flash boiling has received interests from researchers;in addition,the injection deposit in GDI engines will affect the flow in the injector holes,eventually affect the quality of mixture of air and vaporized gasoline.This dissertation studies spray characteristics under flash boiling and deposit in the injector.This topic uses a five-hole injector to study the spray characteristics of ethanol gasoline,ethanol and E10 ethanol gasoline(ethanol volume fraction accounts for 10%)was used.The high-speed optical camera is used to capture the transient spray image,and a MATLAB program is used to post-process the image of spray to obtain the spray width,penetration distance,spray cone angle and other parameters during the development process.The research results show that the spray curling phenomenon will occur at the end of the transitional flash boiling spray.At this time,the spray penetration distance decreases,and the spray width near the outlet increases,and near the outlet,the spray width rises in a parabolic shape.The plumes come together under flare flash boiling,which called spray collapse.At this time,the spray penetration distance increases significantly,and the higher the superheat,the greater the increase in penetration distance.In addition,the high-speed camera was used to study the spray characteristics of ethanol gasoline.The results show that ethanol gasoline can exhibit typical nonflash boiling spray characteristics when the superheated degree is relatively low.Under the same conditions,ethanol Gasoline is more prone to flash boiling than ethanol;but under high superheat,the spray parameters of ethanol gasoline are less affected by superheat.According to the basic physical properties of ethanol and gasoline,a mixture model of physical properties of ethanol gasoline was built in PRO ? software,and by calculating the bubble point and dew point of ethanol gasoline,the superheat under different working conditions was obtained and compared with spray of ethanol gasoline.The comparison of the test results proves that the model is more accurate in predicting the flash boiling conditions of ethanol gasoline.With the respect to deposit,the FLUENT software was used to simulate the flow phenomenon in the holes of different injectors.The types of injectors are:non-carbon deposit injectors,inlet carbon deposit injectors,light deposits in counterbore,and heavy deposits in counterbore.The results show that the main cavitation flow inside the nozzle hole is mainly the sheet cavitation at the entrance of the counterbore,the cloud cavitation at the boundary between the inner hole and the counterbore,and the vertex cavitation caused by backflow at the wall surface of the counterbore;the presence of carbon deposits will affect the inside of the hole Cavitation effect,carbon deposits at the counterbore mainly affect the strength and development direction of the cavitation at the counterbore.In addition,the flow velocity and turbulent kinetic energy at the outlet of different injectors are compared.