Diesel Numerical Simulation Study Of The Combustion Process

Because the energy and environment problems become increasingly serious, all people’sviews are focused on saving energy and protecting the environment. Diesel is refined bypetroleum,so many countries’s rules are more and more strict on emission of internalcombustion engine for saving oil resources. So we need to delving into the combustion andemissions. The study methods of diesel engine combustion are mainly experiment method andsimulation method. They have both merits, this paper adopts the second method for dieselcombustion numerical simulation research.In this paper, we use the software FIRE to build a model of diesel combustionchamber,and set up reasonable boundary conditions,initial conditions and mathematicalmodel.Then simulate the process from the inlet valves close to the exhaust valves open. Bycomparing the experimental and simulation data, the model is validated. On the rated speed of2500r/min, thermal parameters and in-cylinder flow field ard studied.The results show thatpressurepesks at17.34MPa in367°CA; The average temperature reaches1888K in376°CA;exothermic is fastest in359.2°CA; NOx’s mass fraction is max for1.45×10-5in410°CA; TheSoot is generated a companing oxidation,whose mass fraction is max for3.365×10-5in359.2°CA then reduce slowly. And we can see from the temperature field, near the top deadtemperature is particularly high duing to the rate of pressure rise is extremely large in thecylinder.The temprature reaches the highest point of2735.7K in the368°CA. The temperaturein cylinder reduces gradually as the combustion intensity is reduced.On this basis, this paper studies the influence of spray cone angle. It mainly affects oilbeam through the location in the cylinder and the location of oil particles hit the wall.If spraycone angle is too small,it make oil mist has a large number of accumulation in the pits of thecombustion chamber.And it is bad for diffusion and mixing of the fuel. Bigger spray coneangle can promote fuel air mixture.In addition,this paper also studies the influence of fuel injection advance angle on thecombustion.The result shows reducing the advance angle, the heat release rate curve moves back and its max value will decrease. Advance angle increases, the combustion starting pointin cylinder is advanced, the max pressure in cylinder, pressure rise rate, the highesttemperature is significantly larger,Appropriately reduce the advance angle can avoid dieselengine’s roughwork and combustion noise decreases，and NOxhas a creasing trend. The massfraction of NOxis increased from1.1×10-5to1.9×10-5, When the advance angle is from5°CAto9°CA, So it can be concluded by decreasing advance Angle can effectively reduce NOxgeneration. But with the increase of advance Angle, Soot emissions decrease.when advanceangle is different and concentration has obvious differences in same crankshaft Angle. In acertain range, increase the advance angle, mixture is more when fire.