Study On The Evaporation And Combustion Characteristics Of Single Droplet Of Diesel-Tung Oil-N-butanol Blended Fuel

The shortage of petroleum resources and environmental pollution issues are pressing concerns.It is urgent to find efficient and clean alternative fuels for diesel vehicles,and vegetable oil as an oxygen-containing substitute fuel has the advantages of being clean and efficient.However,tung oil,as a non-edible vegetable oil,has the problems of high viscosity and poor volatility.By blending tung oil with appropriate alcohol fuels and diesel,it can better serve as a vehicle substitute fuel.In this paper,direct blending method was selected to blend tung oil with n-butanol and diesel to prepare diesel-tung oil-n-butanol blended fuel.Using a hanging droplet single droplet evaporation test device,the evaporation and combustion characteristics of the fuel droplets were studied.The main research work of this paper is as follows:In this study,different proportions of binary diesel-n-butanol blended fuels(D90B10,D80B20)and ternary diesel-tung oil-n-butanol blended fuels(D70T10B0,D70T20B10,and D60T20B20)were prepared using the direct blending method,and the physicochemical properties of the two types of blended fuels were determined.Using a single droplet evaporation test device,single droplet evaporation and combustion tests of the fuels were conducted at different ambient temperatures,with initial droplet volumes of 0.6 μL,0.8 μL,and 1.0 μL.A high-speed camera was used to photograph and collect the evaporation and combustion process.An image processing program based on MATLAB was used to extract the droplet diameter data during the evaporation and combustion process.Temperature data of the droplets were collected using a temperature acquisition card,and the effects of different ambient temperatures,fuel characteristics,and initial droplet volumes on the evaporation and combustion processes were studied.The results show that:At an ambient temperature of 723K,the droplet evaporation process of the diesel-nbutanol binary blended fuel can be divided into three stages: stable expansion stage,fluctuating evaporation stage,and equilibrium evaporation stage.The droplet evaporation process of the diesel-tung oil-n-butanol ternary blended fuel can be divided into two processes: the first evaporation process consists of fluctuating evaporation stage and equilibrium evaporation stage,while the second evaporation process consists of secondary micro-explosion preparation stage and secondary micro-explosion stage.At ambient temperatures of 723K,and 773K,the total evaporation time of the binary blended fuel and the duration of the first evaporation process of the ternary blended fuel with the addition of tung oil are correspondingly related.At 723K,773K,and 823K ambient temperatures,the higher the temperature,the faster the evaporation rate of the blended fuel,the higher the probability of micro-explosion occurrence,the shorter the delay time of micro-explosion,and the greater the intensity of micro-explosion.The larger the initial volume of the blended fuel droplet,the slower the rate of temperature increase,the slower the evaporation rate,the longer the delay time of micro-explosion,and the smaller the intensity of micro-explosion.The higher the content of n-butanol in the diesel-tung oil-n-butanol blended fuel droplet composition,the shorter the time required for droplet evaporation,the higher the probability of micro-explosion occurrence,the shorter the delay time of micro-explosion,and the greater the intensity of micro-explosion.The higher the content of tung oil in the composition,the longer the time required for droplet evaporation,the lower the probability of micro-explosion occurrence,the longer the delay time of micro-explosion during the fluctuation evaporation stage,and the greater the intensity of micro-explosion.At an ambient temperature of 823K,the higher the content of n-butanol in the blended fuel composition,the longer the ignition delay period,the shorter the combustion duration,and the smaller the comprehensive combustion index.Compared to the base fuel,the combustion improvement is better.The higher the content of tung oil in the composition,the longer the ignition delay period,the longer the combustion duration,and the larger the comprehensive combustion index.Compared to the base fuel,the combustion situation is worse.n-butanol and tung oil promote the occurrence of micro-explosion in the combustion process of the blended fuel droplet.