Study On The Influence Of Fuel Temperature On Combustion And Emission Performances Of Biodiesel

Biodiesel， as a green renewable energy, can directly substitute for diesel, thus attractingmore and more attention. However, it may cause the increase of automobile NOXemissions.So the researchers carry on many attempts and research to reduce the biodiesel NOXemissions. Based on the research of biodiesel at domestic and abroad, the paper studies thethermodynamic properties of biodiesel and diesel engine performance by the way of changingtemperature of the inlet oil. By the means of simplified mathematical model, this paperanalyzes the impact of temperature and pressure on the thermodynamic properties of biodieseland fuel temperature on the influence of the injection system of diesel engine. Four oiltemperatures are chosen, and a engine test with the fuel thermostatic device is set up. Then,combustion and emission performances of fuel are researched systematically and relativerules are ascertained. And the paper predicts the impact of oil inlet temperature on the currentmainstream diesel engine electronically control injection systems. Accordingly，the paperprovides academic and experimental base for new environmental and economical alternativefuels.The research have shown the following results: Firstly, the sonic speed, density and bulkmodulus of biodiesel decreases with the rise of the fuel temperature, but the compressibilityincreases. With the increase of pressure, the sonic, density and bulk modulus of biodieselincreases, but the compressibility decreases. With the rise of temperature and fuel temperature,injection timing delay, the injection rate decrease and injection duration extend.Secondly, compared with biodiesel temperature of10℃, HC、CO and soot emissions ofthe biodiesel temperature of25℃、40℃and55℃increase at load characteristics, but the NOXemission decrease and the absolute value of HC and CO emissions is the lower and theabsolute value of soot emission is the lower at1800r/min.Thirdly, with the increase of inlet temperature, pressure and instantaneous heat releaseratio curves leave far away from the top dead center and at high loads curves delay obviously;peak combustion pressure and peak instantaneous heat release ratio decrease and at high loadsthe range of decreasement increases; heat release ratio at after-combustion period increases；with the increase of fuel temperature, the cycle difference rate decreases.Fourthly, the impact of inlet temperature on injection system of electronic inline pumpand electronic unit pump depend on the installation position of the solenoid valve. When thesolenoid valve is installed in the high-pressure pipe or pump, the impact of different temperature biodiesel on the injection system of electric control line pump and electronic unitpump are similar to the traditional diesel. The increase of biodiesel temperature will prolongthe pressure build-up period of fuel injection system, when electronic control injection systemuse electromagnetic injector. Due to the bulk modulus decreased and the fuel amount ofcompression of plunger chamber increased, the pump-fuel rail pressure build-up period ofhigh pressure common rail injection system is prolonged and it directly affects the dynamiccharacteristics of the pressure Common Rail Diesel Engine. The fuel quality of per unitvolume of the high-pressure common rail injection system lessens with the decrease of fueldensity, so, it result in fuel injection duration and after-combustion period extension at thesame operating conditions.