Research On Key Technology Of EURO ? Heavy Duty Diesel Engine Particulate Filter Regeneration And Control

As a device for solving particulate emissions in engine exhaust,diesel particulate filters have received extensive attention.During the working process of the particle trap,as the running time of the vehicle increases,the deposition amount of particulate matter in the trap increases,which causes the exhaust back pressure of the engine to increase,causing problems such as poor intake air and incomplete exhaust.In-cylinder combustion deteriorates and pollutant emissions rise sharply.Therefore,the regeneration of particulate matter in the filters becomes a key issue that must be solved.In the engine normal operation mode,due to the low temperature of exhaust and the NO2 content,it is difficult to ensure complete regeneration of the particulate matter only by passive regeneration of NO2 in the exhaust gas.Therefore,active regeneration of particulate matter is required.In order to ensure the safety and economy of active regeneration,the judgment of the active regeneration timing of soot in the particulate filter and the temperature control of the active regeneration process become difficulties.In this paper,aiming at the key point of soot load estimation in diesel particulate filter and temperature control of active regeneration process,it is expected to establish a soot loading estimation model to accurately estimate the soot in real time.At the same time,combined with the precise control of the inlet temperature of the particle filter,the active regenration should be kept safe.To this end,this paper establishes a model of soot load by considering the model coupling soot capture mechanism model considering the diffusion of NO2 in the passive regeneration process.And to estimate the soot load in real time by the filter pressure drop characteristics.The two methods jointly determine the mass in filter effectively solves the problem of carbon load estimation.In order to control the temperature of the active regeneration process in the filter,the temperature response process of the semi-physical oxidation catalyst model structure is proposed as a multi-stage inertia plus delay,and the equivalent inlet temperature step of the fuel oxidation reaction of the exhaust pipe.Combined with the test test,the control oriented oxidation catalyst model is established.The Smith observer effectively solves the delay problem of temperature response during active regeneration.And an adaptive control algorithm is designed to resolve the variable parameters of model.Active regeneration control strategy tested through the WHTC transient cycle.And this paper selects oxidation catalyst and coated particulat filter in heavy-duty diesel aftertreatment system as the research object.The main research works and conclusions are as follows:1.The soot loading estimation model was established by analyzing the source,consumption and pressure drop characteristics of the particulate filetrs.By analyzing the mechanism of the pressure drop of the particle filter,the relationship between the pressure drop in the clean state and the exhaust flow rate is established.Combined with the pressure drop model of soot loading state,the linear relationship between the pressure drop and the exhaust flow rate is established.The results show that the estimated error range is 8%-12%,in the low exhaust flow region.The error can be controlled within 5%in the high exhaust flow interval.At the same time,a method for estimating the soot loading of the passive regeneration model coupled soot capture mechanism model with NO2 diffusion mechanism was established.The verification results show that the estimation error can be controlled within 10%at all test conditions.2.A control-oriented oxidation catalyst model was constructed.By analysed the oxidation catalyst working process,the main chemical reactions,heat and mass transfer processes occurring inside the carrier were analyzed.Three-dimensional CFD model and one-dimensional chemical reaction kinetics model were established respectively.The radial and axial temperature distribution of the carrier was analyzed by model simulation.Based on the analysis of the system characteristics,the multi-step inertia plus delay semi-physical model structure was proposed.Combined with the test,the control oriented oxidation catalyst model is established.Select the appropriate working conditions to identify and verify the model parameters.The results show that the third order model can well indicate the temperature response characteristics of the oxidation catalyst outlet temperature.Considering the complexity of the system,the first-order and third-order model are selected as the basis of the control system design.3.An effective control strategy was proposed based on the smith structure,which solved the system response delay and control parameter adaptation.Based on the feedforward predictive control,the smith observer is developed based on the Smith predictive controller architecture.The control stratery based on first-order model is designed by ITAE standard PI controller.And the control stratery based on third-order model is designed as the equivalent optimal control system parameters.To deal the saturation of the system,an anti-saturation filter is designed.The back calculation and tracking algorithm is used to design the filter.The control strategy is built under the simulink platform.4.The verification of active regeneration control strategy was carried out based on the WHTC transient test cycle.Through the control of the fuel injection of the exhaust pipe,the temperature control effect of the oxidation catalyst outlet was verified,and the temperature distribution characteristics in the particle trap of the active regeneration process were analyzed.The PI control strategy based on the first-order model developed a large fluctuation of the oxidation catalyst outlet temperature.A large overshoot of the system was emerged because the model has a mismatch.The PID control strategy based on the third-order model designed can control the DOC outlet temperature to within ±20 ? of the target temperature under the WHTC cycle.The temperature of the internal temperature carrier of the particle trap gradually increases along the axial direction.At z/L=7/8,the maximum temperature of the regeneration process reaches 715.7 ?.After WHTC cycle regeneration,the soot loading changed from 3.91 g/L to 0.31 g/L.The active regeneration efficiency was as high as 92.07%.