The Simulation Analysis Of EGR On The Combustion And Emission Characteristics Of Diesel Engine

Diesel engine used more and more widely, but also vehicle emission regulations aremore and more stringent, especially the contradiction between NO and the particles isdifficult to solve. So we must seek the effective control measures on emission. Researchshows that EGR can significantly reduce NO exhaust, but still need reveals the effectmechanism meticulous deeply from microcosmic angle. The influence of EGR is complexto particulate exhaust soot, therefore, should from the macro and micro perspectives toreveals the influence of EGR to particulate exhaust soot. To find out the generationcondition of exhaust soot and NO, using Φ-T map comprehensive analysis the process ofcombustion in the whole cylinder. To discuss the swirl strength on improving theperformance of the diesel engine, add the single factor---swirl ratio, on the basis of EGRrole. This paper will research the several problems in turn using the simulation method.To build the geometry model and the calculation mesh of the4100direct injectiondiesel engines, using ESE module of the3D simulation software AVL FIRE. To constructa scientific and reasonable simulation platform, using the CFD module to set boundaryconditions, initial conditions, setting reasonable calculative step length, and selectingspray son model, the burning son model, emission son model and adjusting all parameters.First set the single factor EGR rate changes, then the oil flow of every cycle, the initialconditions in cylinder pressure, temperature, density and swirl strength, boundaryconditions the cylinder head temperature, cylinder walls temperature remain constant, tofind out the EGR rate on influence on the performance of the diesel engine. And then setthe single swirl ratio change, analysis influence of the diesel engine performance withswirl strength change.First of all，simulate the combustion process of3200r/min,50%load,swirl rate of2.3,no EGR condition. And then add EGR of0.1,0.15,0.2,0.3,0.4, etc, simulate theprocess and analysis the influence of EGR on combustion. With setting EGR rate on0.4,changing the swirl rate (1.5,2,2.3,2.6,3,3.5,4), the influence law of the diesel enginecombustion and emission of swirl. The results show that: First, EGR can significantlyreduce the NO. Second, with the increase of EGR rate, the average temperature reduce;according to temperature reduction, carbon smoke present different situation; when the temperature is more than1800K, EGR increases carbon smoke cargoes; when thetemperature is less1800K, EGR can reduce carbon smoke cargoes. Three, by Φ T(equivalent than-temperature) diagram analysis, equivalent ratio is less than2, and localcombustion temperature keeps in2200K, it can avoid the high concentration NO produce;Carbon soot formation conditions is high yield ratio and middle combustion temperaturearea (1800K to2200K). Four, increasing swirl ratio can improve combustion in cylinder,in small range of temperature rise and can greatly reduce NO.