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VGT Turbocharger – Learn About The Fast-Growing Development In 3 Minutes
This paper briefly introduces the development of VGT turbocharger control system at home and abroad。
General Situation Of The Development Of VGT Turbocharger Control Systems Abroad
Foreign countries have always been in a leading position in the research and innovation of VGT turbocharger (variable geometry turbochargers) control systems. The United States, Germany, and Japan have developed a variety of typical and practical variable nozzle turbocharger control systems.
Honeywell has developed a VGT turbocharger system in the last century, which is mainly composed of nozzle vane actuators, PCM valves, vacuum pumps, control units, sensors and various instruments. The nozzle vane actuator adopts a diaphragm-type negative pressure actuator, and the actuator is powered by a vacuum pump installed at the rear end of the generator. A PCM valve is installed between the actuator and the vacuum pump to control the negative pressure of the actuator.
The control unit sends a control signal to the PCM valve according to the engine sensor signal and adjusts the negative pressure generated by the vacuum pump by changing the time ratio of opening and closing of the PCM valve, thereby controlling the angle of the nozzle vanes. The control system takes the boost pressure as the control target parameter.
To improve the stability and smoothness of the system under non-steady state conditions, a feedforward PI control algorithm is used: the engine speed and load are determined under steady-state conditions. The nozzle opening load ratio is used as feedforward and added to the PI control algorithm to realize the control of the PCM valve.
American GM has also developed a VGT turbocharger system for gasoline engines. The system consists of an actuator, electronic pressure regulator (EPR), electronic vacuum regulator (EVR), electronic control unit and sensors.
The difference between the system diaphragm type pressure actuator and the previous diaphragm type actuator is that the actuator air chamber is divided into two parts by the diaphragm, and the diaphragm is simultaneously affected by the intake manifold and the booster from the air intake manifold before the compressor after the throttle valve.
The pressure difference between the two air chambers of the compressed intake manifold pushes the diaphragm to drive the nozzle ring blades to rotate, to ensure that the pneumatic actuator can effectively overcome the resistance from the nozzle pull rod under various working conditions.
In addition, the pressure in the two air chambers is controlled by EPR and EVR, respectively. The control strategy is to first create a steady-state working condition boost pressure control MAP map and store it in the ECM, compare the current boost pressure with the target boost pressure in the ECM, and the electronic control package adjusts the control signal according to the difference to make the execution The controller acts to realize the optimal control of boost high pressure.
In addition, Japan Ishikawajima-Harima Heavy Industries Co., Ltd. also applied fuzzy control to a six-cylinder diesel engine power equipped with a VNT turbo, using a stepping motor to drive the actuator, and achieved good control results.
Research Status Of Domestic VNT Turbocharger Control System
Domestic research on VNT turbochargers is slightly behind foreign countries, and there are few units engaged in this research. Among them, Tsinghua University, Beijing Institute of Technology, Tongji University and other colleges and universities have done some work in the VGT control system.
In 1995, Wang Junqiu of the Beijing Institute of Technology and others developed a VGT control system. The system consists of electronic control unit ECU, turbine section opening actuator (torque motor), sensor and control object J6110Z diesel engine and so on.
The system accepts signals such as engine speed, boost pressure at the compressor end, and displacement of the nozzle blade actuator at the turbine end. Through a certain algorithm, the control signal is output to the nozzle blade actuator to change the rotation angle of the nozzle ring blades, thereby controlling the turbine nozzle opening.
In 2000, Ma Zhaochen from the Beijing Institute of Technology and others designed a mechanical starting control system for the VGT matched to the J6110Z six-cylinder diesel engine. The position of the nozzle ring blade of the supercharger is controlled by a swing rod, which adopts the lever principle.
The two ends of the swing rod are the nozzle ring blade and the spring respectively. The balance of the pressure difference across the actuator diaphragm drives the nozzle ring vanes to rotate. The design point of the turbocharger is selected at the calibration point, at which time the tension of the spring is balanced with the compressor outlet pressure acting on the diaphragm.
The State Key Laboratory of Automobile Safety and Energy Conservation of Tsinghua University has developed the VGT turbocharger control system on the Volkswagen TDI engine, which is characterized by using a stepper motor as the actuator, and checking the MAP map through the two signals of the engine speed sensor and the accelerator position sensor. , get the target boost pressure, and carry out PID control.
In the steady state, the PID control with the change of the variable nozzle opening is adopted to achieve good control of the target boost pressure. In the transient condition, the control method of PID parameters is different from the steady state and the introduction of the prediction function is adopted to enhance the response speed of the system in the transient condition, and the test is carried out on the developed software and hardware system.
Epilogue
Variable nozzle exhaust gas turbocharging technology has a wider space than traditional exhaust gas turbochargers in terms of energy saving and emission reduction of internal combustion engines. It is the current development direction of supercharging technology.
Its research and development are of great importance to promoting the upgrading of China VGT turbocharger industry. After decades of technical accumulation abroad, the variable nozzle turbocharger is far ahead of China in terms of overall technology and control technology, while the research on variable nozzle turbochargers in my country is only in the theoretical research stage.
