Study On Injector Performance Testing Based On Pressure Wave

Injector has an important effect on engine power, economy and exhaust emission. However, the way to test injector in our county lags behind, by using hand pump to test injector, there is great subjectivity, not high detection precision and inconvenient use. It is necessary to improve injector testing way in order to enhance injector passing rate,control engine exhaust emissions and reduce energy consumption.This paper analyzes the various faults of injector and its impact on the pressure wave, and design an injector testing system based on high-pressure in the pipe with electronic technology, sensor technology and signal processing technology. Main results and conclusions are as follow:(1)According to the main problems in the injector testing line, design an injector testing system whose microcontroller is MCU and study object is pressure wave.(2)Hall sensor is used to test engine speed, recursive average filter is used to filer noise, and then get engine speed. Determine sampling frequency according to engine speed.(3)Piezoelectric sensor clipped on outside of pipe is used to test pressure, wavelet transform is used to remove noise in order to get sheer pressure wave signal. Symbolic method is used to extract opening pressure, maximum pressure and secondary opening pressure from sheer pressure signal.(4)Complete the design of system hardware, mainly included MCU microcontroller, external clip-on piezoelectric sensors, Hall switch sensor, data processing circuit, A / D converter circuit, the external memory expansion circuit, LCD display circuit, sound and light alarm circuit , the keyboard circuit, power circuit, clock and reset circuit. Bread board is used to build actual circuit.(5)Complete the design of system software, mainly included initialization module, engine speed measurement module, the pressure signal acquisition and A / D converter module, the pressure waveform feature extraction module, external memory read and write modules, LCD display module, keyboard, and sound and light alarm module. Use C language to design software program. (6)By the combination of Keil and Proteus system debugging and simulation, set the actual engine speed 1000r/min, the system detects the speed 999r/min; extract the pressure wave and three characteristic parameters ,the opening pressure P0, the maximum pressure P1, secondary opening pressure P2.the actual hardware on the system was verified. The results show that high-pressure tubing to the pressure by extracting the feature parameters to detect the waveform performance of the injector is feasible, to achieve the desired detection performance of the injector.