Simulation Of Exhaust Reinduction On The Gasoline CAI Engine Combustion And Gas Exchange

Energy sources and environment protection are main problems that confronted to thehumankind.As the development of society, the amount of automobile increase andautomobile not only become the main energy consumption source but also the largestemission pollution resource. As a developing country, the conflict between energy sourceand environmental protection should be resolved to keep the country harmonious andsustainable development. The researchers in the internal combustion engine businessshould find new combustion form with higher thermal efficiency and correspondingalternative fuels.Controlled AutoIgnition (CAI) is receiving increasing attention from the worldwideautomotive industry as well as academia., it is different from combustion in spark ignition(SI) and compression ignition (CI) engine. It not only is equal to the diesel engine thermalefficiency but It emerged as a promising technology for reducing exhaust emissions andimproving fuel economy of CAI engines So it has attracted widespread attention of theinternal combustion engine field. But CAI combustion of the high octane value fuelactually faces the fire difficulty and the difficult of combustion rate control. The earlierperiod research indicated that the use of internal EGR solves these two questionseffectively.The simulation of CAI engines is a new area and a complete engine simulation codewith detailed chemical kinetics of CAI combustion is not yet available. This article hasestablished the gasoline CAI engine circulation model coupling with engine simulationsoftware GTPower,programme software MATLAB and the largescalechemical kineticsanalysis software CHEMKIN .The research on the model are as follow:1 The effect of fully flexible valve actuation system driven by the camless electrohydraulicvalve operating system is analyzed to find the effect of the differentmatch factor to the in internal EGR rate. The range of exhaust port recirculation(EPR) wasinvestigated by the simulation model at the speed of 1000r/min. The simulation resultsindicates that:Using the Exhaust Port EGR strategy,the load arrange can be extend high.The result show that when EGR rate is lower than 39.2%,the temperature at the IVC islower than 475.1K,this temperature is too low to carry out CAI. when the EGR rate ishigher than 83.3%, the concentration of charge is too low, misfire appears.Therefore theEGR rate to realize CAI is 39.283.3%.2 The parameter of combustion and gas exchange were investigated at the speed of1000r/min by different strategies and various vavle lifts. Effects of the strategies on load,fuel economy,m ax. rate of pressure rise,tr apped gas temperature and temperature at TDCwere studied. including the development of pressure,temperature and speciesconcentration. By the analyse of the mass flow rate of the intake and exhaust valve, anearly IVO results in a strong reverse flow which leads to a high EGR level.It was foundthat ormaldehyde (CH2O) concentration is related to ignition delay whereas hydroxyl (OH)concentration rapidly increases at the start of the main combustion stage. Thecharacteristics of CAI combustion in the engine were investigated, The internal EGR hasthe dual function to the CAI , one function is to heat fresh air to make it easy to fire?theother function is the heat capacity and the dilution function,which may reduce the chemicalreaction speed,postpone the fire, lengthen the burning duration. When EGR rate is smallerthan 64.8% heat function performance to be remarkable. Along with EGR rate increasing,fire beginning spot is ahead of time?and the burn durationwill be shorten. When EGR rate isbigger than 64.8%, reducing the chemical reaction rate act to be remarkable role. Alongwith the EGR rate increasing, the fire beginning spot postpones,the burn duration will beprolonged.We find the characteristics of CAI combustion has little influence at high vavlelifts.3 The combustion characteristics of gasoline and ethanol were compared.The gasolineadvance the ignition timing ,the combution duration and combustion temperature.The effects of speed on EGR rate of EPR was contrasted in this paper.The results showthat ,when the engine works at low speed, due to reverse flow ,the rate of EGR get obviouschange from a lower level to a higher level,the rate of EGR can reach 83.3% at most. Oncethe speed reach 1400r/min,at this speed,there was neither flow backwards nor intakeresistance,so the CAI range at this speed is wider than the others.When the speed exceed1600r/min there was intake resistance in the intake and exhaust port,for the area of intakevalve late for 020°CA ,the rate of EGR was too low to realize CAI combustion.Moreover ,the intake resistance get worse along with higher speed. the crank angle atwhich can realize CAI combustion comes later .4 This model is used to forecast the range of the speed and the load of the CAI engine.