It is a pneumatic engine, which is a power machine that converts stored pressure energy into mechanical energy output by high pressure compressed air expansion in the cylinder. It can achieve true zero emissions without consuming petroleum fuel.
Compressed air engines are actually a way of applying electricity. Normal air is compressed using an air compressor and stored in a high pressure gas cylinder. Using the high-pressure compressed air stored in the cylinder, the pressure energy released by the expansion in the engine cylinder pushes the piston down to drive the car.
Compressed air engines have no combustion process compared to conventional internal combustion engines. Therefore, the working pressure and pressure increase rate in the engine cylinder are both low, which makes the engine work stably, the noise is low, the material strength is not high, the structure is simple, the size is small, and the manufacturing cost is also low. At the same time, the fund project: Tsinghua University's national safety and energy conservation is the theoretical P-Y diagram of the four-stroke compressed air engine. Among them, 0°CA~180°CA is the natural intake stroke, the intake valve is open, the exhaust valve is closed, and the atmospheric air is sucked into an atmospheric pressure; the 180 degree CA ~ 360 degrees CA is the compression stroke, and the intake and exhaust valves are Closed, the completion of the compression of 0.1MPa atmospheric pressure to 2MPa of the end ~540 °CA for the jet, expansion stroke, the intake and exhaust valves are still closed, the high-speed solenoid valve is opened, closed after the completion of the isostatic jet process, high-pressure air In the engine cylinder, the expansion is completed. The ~720°CA is the exhaust process, the exhaust valve is opened, the intake valve is closed, and the air with reduced pressure is discharged from the engine cylinder to complete the exhaust process, which is a new round of work process. be prepared.
1 The overall design of the electronically controlled injection-type compressed air engine In the research of the compressed air engine, as mentioned above, many people have done a lot of effective work, mainly based on the mechanical two-stroke compressed air engine. It is not difficult to find that there is an inherent weakness in this type of compressed air engine: it is impossible to achieve the best jet advance angle and jet pulse width under all operating conditions of the engine, thereby affecting economy and power.
Since the mechanical compressed air engine is driven by the intake cam to control the jet advance angle and the jet pulse width, the intake cam profile determines the post-jet advance angle and the jet pulse width. The engine must be operated under different working conditions, and different gas distribution parameters are required to achieve the optimal operation of the engine. Obviously, the mechanical compressed air engine is difficult to meet the optimal operating conditions of the engine under all conditions.
Caused a part of the throttling loss. Because the mechanical compressed air engine can't adjust the pulse width and output power by adjusting the pulse width, it is bound to cause the section to adjust the output speed and input power by installing a control valve on the gas pipeline to control the intake flow cross section. Flow loss. The theoretical corpse of a single-cylinder four-stroke compressed air engine has a large structural change. In addition to the previous Pan air engine, there is an important way to change the four-stroke engine to the two-stroke mode, which requires heavy reasons. The analysis found that if the compressed air expands according to the isothermal process, the newly designed valve train releases the most mechanical energy. This requires the engine to absorb as much heat as possible from the surrounding environment during operation to approximate the isothermal expansion curve. During the natural intake stroke, the compressed air engine draws in fresh air at ambient temperature (incorporating ambient heat from the outside air) and compresses it to the top dead center of the piston. Then the solenoid valve is opened, and the high-pressure air is injected into the cylinder, and the hot air in the cylinder is mixed and expanded to push the piston down.
The core of the entire electronically controlled jet compressed air engine design is the design, fabrication and commissioning of a compressed air engine management system. It consists of four parts: sensor, actuator, electronic control unit ECU and PC monitoring system. The basic idea is that the electronic control unit ECU determines the engine according to the input signal of the relevant sensor (mainly the engine speed and pedal position). Operating conditions at the location; the main microcontroller learns the pulse injection (MAP) map of the intake injection timing and the injection pulse width calibrated in the external memory according to the operating conditions of the engine, and according to the intake pressure and the atmospheric temperature The auxiliary signal such as the battery voltage makes necessary corrections to the intake injection timing and the injection pulse width; the human single-chip microcomputer receives the intake injection timing and the injection pulse width transmitted by the main single-chip microcomputer, and forms a driving signal of the high-speed solenoid valve, The drive circuit controls the intake injection process (ie, controls the opening and closing of the high speed solenoid valve).
Shown is a schematic of the overall design of an electronically controlled jet compressed air engine. Working medium High pressure compressed air is supplied by the gas distribution system and is delivered to the injectors of each cylinder of the engine through a high pressure gas line. The high speed solenoid valve is mounted in the solenoid valve seat and is coupled to the injector to control the intake injection process. The electronic control unit ECU determines the operating conditions of the engine based on the two main control signals of the engine speed and the pedal position, and obtains the required intake injection timing and injection pulse width, and is assisted by an auxiliary signal such as intake pressure. The atmospheric temperature, the battery voltage, etc. are corrected, and then the drive signal is output to control the opening and closing of the high-speed solenoid valve, thereby completing the intake injection process of the high-pressure compressed air.
13. Engine body assembly 14 starter motor 15. Jet valve, check valve and valve seat assembly 16 coupling 17 photoelectric encoder (top dead center sensor) 18. advance angle adjustment slide 19. advance angle adjustment screw 20. Hardware Design of the Bracket 2 Electronically Controlled Jet Compressed Air Engine Management System The electronic control unit ECU is mainly composed of three parts, namely a logic circuit part, a power drive circuit part and a power supply module part.
Among them, the logic circuit part adopts the dual single chip structure, that is, there are main and slave single chip microcomputers. The communication mode between them is the SPI working mode of Synchronous Serial Port (SSP), and the two share a 4MHz clock circuit. The digital signal and analog signal input by the sensor are received, processed and analyzed by the main MCU. The MCU is responsible for synthesizing the high-speed solenoid valve drive signal corresponding to the engine operating condition, and is driven by the power according to the position signal of the camshaft. The circuit controls the opening and closing of the high speed solenoid valve. The communication between the electronic control unit and the PC is also completed by the host microcontroller through the Serial Communication Circuit (SCI). The power module section is responsible for providing each module with the form of power supply that is required. Shown is the basic structure of the electronic control unit box 5671. Digital input analog input power supply module LSPI communication I main MCU from MCU rate drive circuit solenoid valve 3 electronically controlled injection compressed air engine management system software design electronically controlled injection Compressed air engine management system software is divided into three major modules, namely engine management module, injection control module and PC monitoring program module. The overall architecture of its software is shown.
The engine management module is completed by the main microcontroller of the electronic control unit ECU, so it is also called the host program. The main tasks include the collection and processing of relevant information of the compressed air engine during operation, and the engine operating conditions are determined accordingly, and the corresponding control strategies are implemented, so that it can be divided into several sub-modules.
The PC monitoring program module is completed by the PC. The main task is to send the operating parameters of the compressed air engine in real time through the SCI serial communication module, such as the speed, pedal position, intake pressure, atmospheric temperature, battery voltage, and The gas injection timing, the injection pulse width, and the like are displayed, and the modified MAP map can be written online in the external memory of the host microcontroller.
4 Preliminary experimental study of electronically controlled jet compressed air engine The engine used in this study is to transform the R175 diesel engine. Chinese mechanics 2 Chen Ying, Xu Hong, Tao Guoliang and so on. Research and development of compressed air-powered vehicles 3 Anda, Tan Jian, Zuo Chengji. Compressed air engine design and preliminary experiments. Journal of Hefei University of Technology, 2005, 4 Zuo Chengji, Qian Yejian, Ouyang Minggao, Yang Fuyuan. Analysis of the energy transfer system of a pneumatic engine. China Mechanical Engineering, 2007, 7 (8) 870-873. 5 Zuo Chengji, Qian Yejian, Tan Jian. Wait. An electronically controlled common rail injection system for liquefied fuel. Journal of Internal Combustion Engines, 2002, 20 (6) 481-486. Improvement of the electric control unit of the ignited coalbed methane engine and the design of the ignition control system D. School of Mechanical and Automotive Engineering, Hefei University of Technology, 7 Lu Xiangyou. Research on electronic control unit of dimethyl ether engine D. School of Mechanical and Automotive Engineering, Hefei University of Technology, 2007. 8 Zuo Chengji, Qian Yejian, Anda, Ouyang Minggao, Yang Fuyuan. Experimental study of a pneumatic engine. Journal of Mechanical Engineering, 2007, 4(43) 93-96.
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