Simulation And Experiment Study On HCCI Based On Exhaust Port STRATEGY

In today’s society,energy and environment problem have become more and moreserious.As vehicle production constantly increases,petroleum source consumption hasbeen accelerated,the internal combustion engine develops towards energy saving andemission reduction. HCCI is a new kind of combustion model,it combines theadvantage of diesel engine and gasoline engine,with the technique of VVT,HCCIcombustion can reduce pumping loss,NOXand PM emission,increase compressionratio,improve thermal efficiency and economy performance with inner EGRstrategy.People hope HCCI engine can replace the traditional engines and do well inenergy saving and emission reduction.。HCCI is a new kind of combustion.As it fits a lot of fuels,and the combustionmechanism have not been found,it is very difficult to control ignition and combustionrate.People can control EGR using inner EGR strategy so that they can control engineload.They always use air intake heating with inner EGR strategy to control thetemperature and concentration in the engine.People hope they can control the ignitionprocess with changing these parameters.The paper uses GT-Power and CHEMKIN software to simulate HCCI engineworking process,seek the specific process of combustion and the effect of varied VVTto dynamics and economy performance. This paper establishes the HCCI experimentplatform and does some preliminary experiment of HCCI combustion based onexhaust port strategy and compares them with the simulation results.This papermainly does the following research:(1).Build HCCI simulation platform.Introduce GT-Power and CHEMKIN,useGT-Power to solve the quality,momentum and energy equation;solve the isentropicflow equation in intake and exhaust valves.Use CHEMKIN to solve the specificchemical mechanism of heptane and iso octane，solve zero zone quality, momentum,species,energy equation. The convergence condition is made at last.(2).Build HCCI experiment platform.Change the compression rate to11.5withlengthening piston and lengthening cylinder liner.Settle the spark plug in the mounting hole of the fuel injector.Add ignition control system and fuel injectionsystem to make sure the engine can work with HCCI/SI style. Replace the cam valvesystem with the electro hydraulic valve system.Use the self made engine electroniccontrol system to control the spark plug electro hydraulic valve and the fuelinjector.Use the data acquisition system to gather cylinder pressure,valve lift andcrank angle signals.Do some preliminary experiment of HCCI combustion with thisplatform,observe the effect of the varied extake closing angle to engine combustionand compare the results with simulation.The experiment highest pressure is lowerthan the simulation result.The simulation curve catches the start of the combustion.(3).Use the found platform to simulate HCCI combustion based on exhaust portstrategy.Observe the regulation of combustion and gas exchange when the exhaustvalve closing timing changes.The EGR increases as the exhaust valve closing angleincreases from31%to62%. T13changes from909K to1026K.The accumulate heatrelease curve moves towards left as the exhaust valve closing angle increases. IMEPdecreases as the EGR increases from0.256Mpa to0.56Mpa.BSFC increases as EGRincrease from261g/kw-h to369g/kw-h.(4).Observe the dynamics and economic conditions as the EVC changes from450°CA to550°CA and IVO from360°CA to400°CA.EGR changes from32.2%to73%.Volumetric efficiency changes from19.8%to47%, BEMP changes from0.1437Mpa to0.52Mp.BSFC changes from290g/kwh to530.6g/kwh. Observe thedynamics and economic conditions as the EVC changes from450°CA to560°CAand IVC from540°CA to570°CA. EGR changes from33.2%to70.4%. Volumetricefficiency changes from17.6%to46.5%，BMEP changes from0.11Mpa to0.502Mpa,BSFC changes from294.0g/kw-h to507g/kw-h.