Research On The Characteristic Of Intake And Combustion For Small Gasoline Engine With Supercharger

This paper is from the actual research project.In this project,the intake process andcombustion characteristic was simulated and researched for a1.5T gasoline engine. Thepredecessor of the research object is a1.8L natural inspiratory gasoline engine and thecommission unit would be proposed to transform it into a1.5T gasolineengine.Prototype had been completed.When the performance testing, knock problemshad been found in the low speed region.This problem leaded to ignition advance angleautomatic move backward and even to the TDC.Because of power down and emissionincreases,the engine could not put into production.So the commission unit entrusted ourunit to improve it.In this paper, the intake and combustion process was simulated for the originalengine at first,and the reason of knock had been found.Then by increasing the squeezegas surface,the combustion chamber design was improved.The simulation analysis ofthe new combustion chamber had been carried out again.Compared with the originalmodels,knock problem had been solved in the sense of simulation.The cylinder cover oforiginal engine was transformed by the project commission unit according to the designof the combustion chamber.Performance test showed that the knock problem hadalready no longer appear.The results proved that the research work was successful.The simulation work of this paper depends mainly on FIRE software. The originalengine was simulated firstly. Including:Pro/E software was used to establish inlet andcombustor geometry models for the original engine,and then the model was imported toFIRE for generating set grid and dynamic grid. Preparation was completed through theboundary and initial conditions, choosing turbulence model, calculation methods,relaxation factors, trying to calculate and so on.The intake and combustion processwas simulated for the original engine and instantaneous flow field and simulation dataof combustion process was obtained.Based on the analysis of the original machinesimulation results,the reason of knock had been found.The second step was to designand improvement for the original engine combustion chamber. Two squeeze gassurfaces had been increased in the combustion chamber through Pro/E software.Finallythe simulation analysis of the new combustion chamber had been carried outagain.Compared with the original models,modification machine was obviously superiorto the original machine.so the problem of the knock had been solved from thesimulation level.The innovation points of this paper are using a high level of FIRE softwaresuccessfully to solve the knock problem which happens in the process of new productdevelopment for a kind of internal combustion engine.The use of theory, method,process and conclusion have obvious significance for colleagues.