Numerical Research On Control-Oriented Intake Model Of Direct Injection Supercharged Gasoline Engine

Turbocharger,Downsizing,Gasoline Direct Injection,and Dual VVT technology have gradually become the mainstream of gasoline engine technology development,It can effectively improve the power and economy of gasoline engines.To meet stringent emission regulations,gasoline engines are generally equipped with three-way catalytic converters.Controlling the air-fuel ratio within a narrow range around the stoichiometric air-fuel ratio can maximize the conversion efficiency of the three-way catalytic converter.Thus,the precise control of gasoline engine air-fuel ratio is the key to electronic control system.As the basis of the feedforward control of the air-fuel ratio,the in-cylinder intake air mass is particularly important for its accurate estimation.As VVT,EGR,VGT and other new technologies are applied to the gasoline engine,the complexity of the air system flow of the gasoline engine is increased.The traditional speed density method needs to calibrate the volumetric efficiency multi-dimensional map to calculate the in-cylinder air charge,so the calibration workload is huge and there is no portability.In response to this,based on physical methods,this research proposes a control-oriented turbocharged gasoline engine intake model that reflect the air flow characteristics during engine intake and exhaust.The calibration workload is small and the model is portable.First,a 1.5L direct-injection supercharged gasoline engine equipped with dual independent VVT technology is used as the research object,then design a supercharged gasoline engine test platform and carry out bench tests,based on the thermodynamic simulation modeling method,establish a gasoline engine GT-POWER simulation of the original engine model.According to the bench test data,perform full-load and partialload multi-condition calibration on the simulation model.Secondly,based on the mean value engine model,a control-oriented model for intake air is proposed,including residual gas sub-model,throttle sub-model,and exhaust system sub-model.While reflecting the gas flow motion characteristics of the gasoline engine’s intake and exhaust process,the intake model is simplified as much as possible,and based on MATLAB/SIMULINK software,a complete intake model is further established.According to the bench test data and the GT-POWER simulation model,the key parameters of the intake model are calibrated.Completed the calibration of the key parameters of residual exhaust gas,heat transfer factor in the intake port,turbo expansion ratio,pressure loss of the pre-catalyst and main catalytic converter,etc.Thirdly,according to the GT-POWER simulation platform,at three different valve overlap angles of 0,30,and 60°CA,running at 1600 r/min,2800 r/min,4000 r/min,and5200 r/min speeds respectively to verify the comparison The steady-state intake air mass calculated by the intake model and GT-POWER simulation.Combined with the engine bench test,under the full-characteristic operating conditions of 1200-5200 r/min,the intake air mass flow calculated by the intake model is compared and verified with the measured value of the bench.The results show that the error between the calculated value of the intake model and the measured value of the bench is within 5% except for a small number of points in idle speed and heavy load conditions.Finally,according to the GT-POWER simulation platform,two sets of transient acceleration and deceleration conditions were verified on the intake model.In the transient operating conditions of the throttle opening transient and the engine speed step,the intake manifold pressure,exhaust pressure and exhaust temperature calculated by the intake model have good transient response.To evaluate the transient response of the intake air mass of the intake model,A state observer is introduced to compare the intake air volume estimated by the state observer and the intake air volume calculated by the intake model with the GT-POWER simulation value.The results show that the transient response of the intake model is better than that of the state observer,and the steady-state error is smaller than the estimated value of the state observer.The intake model proposed in this study reflects the characteristics of the air flow motion during the engine’s air exchange process,and reduces the solution of algebraic equations by means of map interpolation.The intake model has a simple structure,small calibration workload,the calibration workload is small,and it is versatile and portable for engines equipped with VVT technology,and can be used as a control model for ECU.Adapted install MAP and MAF sensor engine.When the engine structure parameters are known,only the measurement parameters such as intake manifold pressure and temperature can be used to quickly calculate the air mass in the cylinder.It shows that the proposed air intake model provides a more feasible method for engine system control.