The Study Of Active Control Method Of Combustion Process Based On Target Heat Release Law Of High Speed DI Engine

The rapid development of the world economy and automobile industry has brought the problem of oil shortage and environmental pollution.In order to deal with the increasingly strict emission regulations,it is very important to choose the power source with lower energy consumption and better emission performance.Diesel engine stands out as an important power source to solve the energy crisis and environmental pollution with its high thermal efficiency,low CO emissions,durable and reliable advantage.The performance of diesel engine relys on its combustion process,optimization and controlling of the combustion process is the key to deal with energy crisis and environmental pollution.The controlling of heat release law shape is the key to realize high efficiency low emission combustion process,although the thought of active control of heat release law or combustion process has not been proposed home and abroad,with the gradual maturity of lower exhaust pollutants technical measures and high efficiency clean combustion mode,not only providing a good technical reserves for the implementation of heat release law control,but bringing a new idea to realize the active control of heat release law:the key to realizing high efficiency and ultra-low emission through control of heat release law is to determine and realize the target heat release law of high efficiency and ultra-low emission,To determine and realize the target exothermic law,the following three problems need to be solved:?1?A reasonable quantitative evaluation of the nonlinear transient combustion process is conducted through the curve shape characteristics of heat release law.?2?Making sure of the influencing factors of the quantitative evaluation parameters,and then explore the method to determine the boundary conditions of the target heat release law according to the engine performance.?3?Developping an open-loop prediction and control model of the heat release law that accurately realizes the target heat release law. To solve the above problems,and explore the fully effective ultra-low emission potential method through control of heat release law of diesel engine,based on the JiLin Province natural fund project"The key problem of combustion process control strategy based on target heat release law to achieve the limit of low carbon of vehicle internal combustion engine research on and key problems?20150101032JC?,combined with the2.0L high pressure common rail diesel engine combustion system development project,the following study was carried out:?1?The high pressure common rail diesel engine combustion system simulation model was established with AVL special 3D simulation software FIRE,the transient microcosmic physical fields of the mixture formation and combustion process in cylinder and heat release law were calculated,the dynamic characteristics of mixture formation and combustion process of diesel engine was analyzed,and the quantitative evaluation method which can describe the characteristics of actual combustion process of diesel engine was put forward,and the quantitative evaluation parameters were defined.?2?The transient physical field and heat release law of cylinder under different injection system parameters and intake system parameters was calculated with software FIRE,and the influence law of different influencing factors on quantitative evaluation parameters was compared and analyzed,so as to determine the main influencing factors of each quantitative evaluation parameter.?3?The Bench test was used to collect the pressure rising rate,fuel consumption and heat release law at different injection pressure and injection timing,heat release law combined with average temperature in cylinder and NO generation emissions calculated by FIRE,the mehod to ensure the boundary of target heat release law according to the the limiting conditions of pressure rising rate,the average temperature in cylinder and fuel consumption rate target was studied.?4?On the basis of the above research,based on the intelligent control theory,an artificial neural network model for open-loop prediction of heat release law was established on the MATLAB software platform.The type,structure and algorithm of the artificial neural network model was optimized using bench test data to achieve accurate prediction of quantitative evaluation parameters under different control parameters.In addition,particle swarm optimization?PSO?algorithm was introduced to establish the control model of heat release law.The quantitative evaluation parameters which is the most closed to target heat release law and control parameters was achieved after the optimization of model running parameters.?5?The control accuracy of the heat release law control model was verified by using the open-loop prediction model of heat release law.An artificial neural network model for open-loop prediction of engine performance was established to verify the optimization effect of engine performance.Therefore,the intelligent control method of combustion process based on target heat release law was explored.The research results show that:?1?The impact point of injection can clearly distinguish the characteristics of different stages of mixture formation and combustion process,and correspond well to the characteristics of heat release law curve.According to the characteristics of combustion process before and after the impact point of injection,the combustion process of diesel engine is divided into premixed combustion stage and diffusion combustion stage.Thus,the combustion starting point,premixed combustion rate, diffusion combustion rate and combustion duration were defined,which were used as quantitative evaluation parameters to quantitatively evaluate the transient combustion process or the heat release law curve.?2?The injection timing is the main factor affecting the combustion starting point.Under different injection pressures,within the range of-15°CA^-9°CA before the upper TDC,the quantitative relationship between the injection timing and the combustion starting point is:_?88??7?=495))+10.5.;Injection pressure is the main influencing factor of premix combustion rate,diffusion combustion rate and combustion duration.The quantitative function relationship between injection pressure and premix combustion rate is:?=0.0356P-1.498;The quantitative function relationship between diffusion combustion rate and injection pressure is:?=0.00341P-2.502.The quantitative relationship between the pre-mixing combustion rate and diffusion combustion rate during the studied injection pressure range is?=0.6891?₊0.2607;The quantitative relationship between the duration of the combustion and the premixed combustion rate is:=-6.1974?+52.248.?3?The limited value of pressure rising rate that can meet the requirements of combustion noise is 0.6MPa/°CA,and the limited value of the average temperature in the cylinder that can meet the requirements of NO_x emission in the corresponding VI emission regulations under the studied conditions is 1923K.The boundary of combustion starting point that can meet the requirements of both pressure rising rate and fuel consumption rate is-2.5°CA^-0.5°CA.The boundary of the premixed combustion rate,which can satisfy both the pressure rise rate and the limit of the average temperature in the cylinder is 3.65J/°CA².The diffusion combustion rate boundary,which can meet the restriction conditions of average temperature in cylinder and fuel consumption rate at the same time is 2.68J/°CA²².77J/°CA².The boundary of combustion duration that can meet the requirement of fuel consumption rate is30.32°CA.Under the premise of meeting the pressure rising rate,the limiting condition of average temperature in cylinder and the fuel consumption rate corresponding to national VI standard,the combination of the best quantitative evaluation parameters of fuel consumption rate,namely,the boundary value of the target heat release law is:combustion starting point-0.5°CA,premixed combustion rate 3.65J/°CA,diffusion combustion rate 2.77J/°CA and combustion duration 30.32°CA.It is shown that the high efficiency and ultra-low emission combustion process of diesel engine can be achieved by controlling the heat release law to achieve the boundary value of the target heat release law.?4?Based on intelligent control theory,the open loop prediction model of heat release law with the artificial neural network was established,the highest prediction accuracy was achieved when the BP training method was used under the single hidden layer,the number of neurons in hidden layer is 18 and trainlm algorithm is used in hidden layer,which can reflect control parameters and the heat release law of the nonlinear function relationship between the quantitative evaluation parameters well.The particle swarm optimization?PSO?algorithm is introduced to set up the heat release law control model,the minimum error of quantitative evaluation parameters and target exothermic regularity of the boundary value can be achieved when the particle swarm size is 40,the learning factor is 3,the iteration step length is 900,the output of the corresponding conditions as follows:the injection pressure is 144.04 MPa,the injection timing is-9.081°CA,fuel injection proportion 1.84:38.26?pre injection mass 1.84mg,main injection mass 38.26mg?,EGR rate 23.6%and VNT opening 50%.?5?The optimal solution of PSO is input into the heat release law open-loop artificial neural network prediction model,and the error between the quantitative evaluation parameters obtained and the boundary value of the target exothermic law is less than 5%,indicating that the control precision of the control model of heat release law meets the requirements.In order to verify the optimization effect of engine performance,an engine performance open-loop prediction model based on artificial neural network was established,when trainlm algorithm was adopted in the hidden layer with the number of neurons of 15,the prediction accuracy was the highest,and the engine performance could be predicted under different quantitative evaluation parameters.the optimal solution of the quantitative evaluation parameters of heat release law open loop prediction model of is input and output fuel consumption rate and NO emission values are lower than the corresponding threshold based on the national VI regulations,HC and PM emissions and the basic conditions based on the corresponding national VI regulations limit is the same,showed in this paper,the development of heat release law of open loop prediction and control model is a good way to realize optimization of the performance of diesel.