The Study Of Atomizing Characteristics Of Hybrid Fuel Of Biodiesel And Diesel Based On Constant-Volume Napalm Bomb

Biodiesel is a long-chain fatty acid methyl ester obtained from esterification reaction between grease and short-chain alcohols such as methyl alchohol and ethyl alchohol. Such grease is obtained from raw materials including tallow, various waste grease, oil-bearing crops such as soybeans and ricinus communis, woods such as pistacia chinensis bunge and palms, oil and aquatic plants such as engineered microalgae as well as microbial oil.Biodiesel is of great biodegradability and low toxicity. Under the condition that internal combustion engine doesn't change significantly in structure, diesel could be replaced by biodiesel, animality would not be reduced, and low emission of toxic substances such as sulfide, aromatic compounds, soot and carbon monoxide can be achieved, all of which are of great significance in decreasing emission of toxic substances of diesel engines as well as alleviating global energy crisis. Meanwhile, the atomizing characteristics cast direct influence on combustion and emission of diesel engines, hence, studing atomizing characteristics of hybrid fuel of biodiesel and diesel is of great significance.The experiment firstly built a testbed of subsystems including the body of constant-volume napalm bomb, common-rail oil atomizer testbed, optics system, electronic control system, high-pressure nitrogen gas system and high-speed photography system, secondly wrote a program to analyze and process images with MATLAB, then conducted operations such as picture segmentation and contour extraction, thus analyzed atomizing parameters such as spray cone angle and spray penetration.Based on the proportion of biodiesel in the hybrid fuel of biodiesel and diesel, the experiment employed six proportions, that is,0%(no diesel)?10%? 30%?50%?70%?100%(pure biodiesel), and repectively studied the atomizing processes under different pressure of oil spout (75MPa?95MPa?115Mpa? 135MPa).At last, following findings were achieved through analyzing and processing the images:Under the condition that the pressure of oil spout doesn't change, as time changes, the changes of spray cone angle and spray penetration of same-proportion hybrid fuel are as follow:at earlier stage, the spray increases rapidly; at medium stage, the speed of growth slows down; at later stage, the spray almost doesn't change and tends to be stable gradually.Under the condition that the proportion of hybrid fuel is the same, the spray cone angle and spray penetration increase as the pressure of oil spout increases, and the effect of the pressure of oil spout on spray cone angle is between 3°to 4°. The magnitude of the increase of spray cone angle and spray penetration with the increase of oil pressure will increase as the blending ratio of bio diesel increase.Under the condition that the pressure of oil spout doesn't change, the spray cone angle of hybrid fuel increases as the proportion of biodiesel increases, and the spray penetration reduces as the proportion of biodiesel increases. But the increasing amplitude of spray cone angle is much larger than the reduction amplitude of spray penetration,so the overall atomization effect is enhanced when the bio diesel mixed ratio increase.With comparison, for hybrid fuel of biodiesel and diesel of same proportion, controlling the pressure of oil spout between 95MPa to 115MPa, spray penetration of proper size can be achieved, in which condition the hybrid effect of fuel and air as well as the combustion effect are optimum.