Simulation Study On Particulate Formation And Deflagration Phenomena Of A Direct Injection Gasoline Engine

With the development of technology and the progress of civilization, people began tobecome more increasingly concerned about the environment. Direct injection technologyhas begun extensively used in gasoline engine for its flexible mixture formation, goodpower and fuel economy, more thorough combustion and less emission. Direct injectiongasoline engine is special because of its spray pattern, so it is easy to produce soot becausethe uneven mixture. High compression ratio also leads to deflagration. This paper simulatesparticulate formation and deflagration phenomena of a GDI engine.In this article, the author built the mathematical model on which the turbulentdispersion model, spray models, combustion model, ignition models and emission modelswere selected based AVL FIRE software. Using the moving mesh module FEP, the authormeshes the three-dimensional geometric model of the engine to make a moving grid whichcan be used to calculate and sets the suitable initial and boundary conditions according tothe actual engine.This Paper mainly simulates the influence of soot formation, distribution anddevelopment process and deflagration phenomena in a GDI engine under the differentconditions of injection timing, injection angle, injection duration, injection position, thefuel injection quantity as well as temperature, oxygen content and other combustioncylinder of different parameters and compares direct injection gasoline engine with portfuel injection gasoline engine. The results we get are as follows:(1) Soot form after theignition and its mass fraction first increased and then decreased. The position, in which sootform, transfer from the middle to the surrounding gradually with the progresses ofcombustion. Soot form at the edge position near the cylinder wall in the post-combustion.(2) Temperature and oxygen is a major factor in soot formation. The locations that sootform are at a temperature of1600K-2200K and the oxygen mass fraction under10%.(3)With the crank angle changes, soot formation and distribution are different under thedifferent conditions of injection timing, injection angle, injection duration, injectionposition and the fuel injection quantity. The mass fraction will appear1-2peaks and theaverage mass fractions of soot are also different at the exhaust valve opening time.(4)Direct injection gasoline engine has a bigger difference to port fuel injection gasoline engine on soot formation. Soot mass fraction of port fuel injection gasoline engine is higherthan homogeneous combustion direct injection gasoline engine until the time of exhaustvalve opening but is less than stratified combustion direct injection gasoline engine in latestage.(5) It is the maximum probability which deflagration occurs that when thecombustion is near the end of the urgent combustion period. The area that deflagration mayoccur in combustion chamber is generally at the exhaust side far from normal combustion.With the crank angle changes, the probability size of deflagration is similar to the averagemass fraction of intermediate curve. The temperature is higher when the probability ofdeflagration is large. This is the same to port injection gasoline engine...