Effect Of PODE On Combustion And Emission Characteristics Of Diesel/biodiesel Blended Fuel

With the continuous increase in the number of vehicle ownership,the problem of energy shortage and environmental pollution have become increasingly prominent.Diesel engines are widely used in commercial vehicles,agricultural machinery and engineering equipment,due to their high thermal efficiency,good dynamic performance,and safety and reliability.However,since diesel engines themselves contain high NOx and PM substances,which limit its large-scale application.Under the increasingly stringent emission regulations,it is necessary to find effective ways to reduce and curb NOx and PM emissions for the purpose of achieving energy saving and emission reduction of heavy diesel vehicles.Due to the defects of the existing diesel engine exhaust treatment technology and the problems in the use of diesel engines,the development and use of clean diesel alternative fuel is an important way to solve the problem of energy shortage and reduce diesel emissions.Polyoxymethylene dimethyl ether?PODEn?,as an alternative fuel for diesel,can be obtained from coal-based fuels such as methanol,dimethyl ether,and methylal.PODEn has the characteristics of stable solubility with diesel,high cetane number and high oxygen content.It can be precisely applied to the diesel engine.It is not necessary to modify the fuel supply system and injection system of the diesel engine,it can effectively improve the combustion performance and emission performance of the diesel engine.The application prospect is very broad.In this paper,Diesel/Biodiesel fuel as the base fuel,marked as D100,selected PODE_2-5as the base fuel blended fuel.Adding 5%,10%and 15%volume fraction to the base fuel to prepare PODE/diesel/biodiesel blend fuel,respectively labeled as D95P5,D90P10,D85P15.The physical and chemical properties of different proportions of PODE/Diesel/Biodiesel blends were studied,and the effect of mixed fuel on combustion process and emission characteristics of diesel engine was studied based on a turbo-pressurized,six-cylinder common rail diesel engine test.The research results show that:?1?With the increase of the proportion of PODE blending in the base fuel,the cetane number and density of the blended fuel gradually increase;distillation range,pour point,kinematic viscosity,and lower heating value gradually decrease.?2?At low load and partial load,compared with D100,the combustion starting points of fuels D95P5,D90P10 and D85P15 are advanced.The peak combustion pressure and peak heat release rate of mixed fuel are higher than that of D100.At this time,the diesel injection strategy is pre-injection plus main injection..At medium and heavy loads,the diesel engine has only main injection,and the peak combustion pressure of fuels D95P5,D90P10,and D85P15 is reduced.Under the whole load,the stagnation period gradually decreases with the increase of the engine load.When the load is the same,the stagnation period gradually decreases with the increase of PODE blending ratio.?3?At low loads and partial load,the CA10s,CA50s and CA90s of Diesel/PODE blend fuels advance and both rapid combustion and late combustion phases shorten.At medium loads and high loads,CA10s advance,CA50s remain unchanged and CA90s clearly advance.Rapid combustion phases increase very little,while the late combustion phases clearly shorten.Combustion durations shorten in each engine operation.?4?When the diesel engine is operated at 1400r/min and 2000r/min,compared with D100,the peak combustion temperature and diffusion combustion temperature of fuels D95P5,D90P10,and D85P15 are higher than D100 under the entire load conditions,resulting in NOx emissions.Ascending,soot emissions dropped significantly.?5?Compared with D100,when the diesel engine was operated at 1400r/min,the ultra-fine particle number and volume concentration of the fuels D95P5,D90P10,and D85P15 decreased significantly.With the increase of PODE blending ratio,the decreasing trend was more obvious.After the PODE is blended in the fuel under the entire load,the particle size distribution of the particles is shifted toward the small particle size.