Experimental Investigation Of The Combustion Characteristics And Cyclic Variations Of Emulsified Diesel

With the continuous increasing production and possession of motor vehicles,enormous energy consumption and serious environmental pollution are still existed problems we humans have to face.Solving environmental pollution and achieving sustainable development of energy have become worldwide problem,and in addition seeking for alternative clean energy and renewable energy has become extremely important.Emulsified diesel which contains water can improve the fuel performance of low-quality fuel,optimize the atomization of fuel,which make atomized particles smaller and reduce pollutant emissions.And at the same time,it contributes to reduce the consumption of fossil fuels.Therefore,it has received extensive attention by researchers.In this thesis,optimal formula of emulsified diesel was obtained through stability test.Moreover,under the condition of not changing the engine parameters,engine bench test was conducted fuelling emulsified diesel and pure diesel.The performance,emission characteristics,combustion characteristics and cyclic variations of a high pressure common-rail heavy-duty diesel engine were investigated experimentally fuelling two different fuels,and different trend of two fuels were analysed.In order to obtain the optimal formula of emulsified diesel with better stability,firstly influence factors were screened and determined the high and low level,then the central composite test in Design-expert software was used to carry out different experimental designs,and the response values of each group were obtained.Through analysis of variance,model matching,and regression model analysis,the optimal formula of emulsified diesel that can be used for engine bench test was finally gained.The optimal formula for HLB value was 5.3,the latent solvent volume fraction was 2%,the emulsifier volume fraction was 2%,the stiring time wes 9.96 minutes,and the predicted stabilization time was 268 hours,the average stability time obtained from the test verification was 254 hours.And there is an error of 4.7%between the theoretical value and actual value.From the engine bench test,the results showed that compared with pure diesel,at full load and different engine speeds varying from 1100-2500 r/min,the power performance of emulsified diesel was decreased,its power and torque was decreased by an average of 20.2%and 20.4%respectively;but the economic parameter fuel consumption was decreased by an average of 4.5%,which could play a certain role of fuel-saving.Furthermore,NOx and soot emissions were significantly reduced by an average of 13.9%and 74%,respectively,however HC and CO emissions were increased,the average increment were 11.7%and 18.6%,respectively.At the speed of 1500 r/min,three combustion parameters including the in-cylinder pressure,heat release rate and pressure rise rate,of emulsified diesel were higher than that of diesel fuel at medium and low load;when the load is higher,the results was just on the contrary.At the different engine loads of 35%,50%,70%and 100,the coefficient of variation of the in-cylinder maximum pressure fuelling emulsified diesel is higher than that of diesel,which is 7%,25%,14%and 10%higher,respectively.In addition,at the different engine speeds,the coefficient of variation of the emulsified diesel was higher than that of pure diesel,but the difference was not significant.The coefficient of variation was within 10%when using two fuels and burning emulsified diesel will not affect the stability of the engine.Moreover,the coefficient of variation of the peak pressure rise rate in the in-cylinder fueling emulsified diesel showed a decreasing trend with the increase of loads.