Study On Spray And Combustion Characteristics Of Acidic Oil Biodiesel

Under the pressure of petroleum shortage and more stringent vehicle emissionregulations in the present time, to find the green and renewable alternative fuelbecomes the important research direction of the internal combustion engine. Due to theincrement of oil imports it is urgent to find the clean alternative fuel which will meetthe diesel power and economic performance requirements. Biodiesel with therenewable characteristics and wide resources was concerned, applied and promotedextensively. Biodiesel, the fatty acid ester, is produced by biological oil and lowcarbon alcohol with the catalyst, and the power and economic performance ofbiodiesel is similar to the conventional diesel. Therefore, the essay is studied about thespray characteristics of biodiesel to provide relevant theoretical support.The common rail fuel spray test bench is built based on the EFS fuel singleinjection measuring instrument driver module, the synchronous operation of theinjector and the high speed camera controlled by the Freescale MC9S12DG128SCMto take pictures of the fuel spray process synchronously.The biodiesel studied in this article is the acidic oil biodiesel. First of all, thecomposition and scale of acidic oil biodiesel was measured; then the physical andchemical characteristics of acidic oil biodiesel blends were measured; the influence ofthe biodiesel proportion, the injection pressure and the constant volume combustionbomb ambient pressure on the blends spray characteristics was discussed. The resultsshow that:The injection quantity is insensitive to the change of ambient pressure, motorspeed and biodiesel content. Then the effects of different acidic oil biodieselproportion on the spray characteristics show that: the spray penetration of B100is thebiggest, B0spray cone angle is higher than other blends; the spray tip of conventionaldiesel is bigger and the atomization effect of that is better; in addition, the speed of the spray tip increases with the increasing of the biodiesel content. And with the rising ofthe injection pressure, the fuel atomization effect with the same volume improves, theentrainment of spray tip and gas is intensively, and the structure of the spray tip isricher; in the late fuel injection process, the spray penetration of injection pressure50MPa and80MPa is almost the same, however, the spray penetration of the injectionpressure130MPa has a downward trend; the influence of injection pressure on thespray cone angle is smaller. In addition, as the ambient pressure increases, the spraypenetration and the spray tip speed of B50both decrease, and the spray cone angle ofthat increases, and higher ambient pressure goes against the atomization andevaporation of the droplets. Moreover by comparing the broken time of three injectionpressure, it is found that with the increasing of injection pressure, the spray brokentime shortens, and the spray tip speed goes higher; then there is also some influence ofambient pressure and biodiesel content on the spray tip speed, the increasing ofambient pressure or reducing of biodiesel content both can result in the lower spray tipspeed. At last the combustion and emission characteristics of the electronicallycontrolled, high pressure and common rail diesel engine fuelled with differentbiodiesel/diesel blends have been experimentally investigated. The results indicate thatwith the increasing of biodiesel proportion, the peak of the premixed combustion anddiffusion combustion in the cylinder increase, the combustion start point advances, thecombustion duration shortens and the maximum combustion temperature rises; in thewhole load curve, with the rising of diesel load, CO and HC decrease, however, NO_xincreases; moreover the NO_xof biodiesel is higher than that of diesel.