Research Of The Drive Circuits And Spray Characteristics For GDI Injectors

Gasoline Direct Injection (GDI) technology is one of effective methods to decrease fuel consumption and reduce emission in spark-ignition gasoline engines. The spray characteristics of GDI injectors are important factors to affect GDI engines performance. Therefore, the research of spray characteristics on GDI injectors is meaningful.To investigate the spray characteristics of multi-hole injectors, a measurement system based on constant volume chamber was installed, including a fuel supply system, an electronic control system, an air supply system, an optical path and a high-speed camera. Based on PIC18f4550 MCU, the drive circuits for GDI multi-hole injectors and high-pressure fuel pumps were designed. The advantage of current-drive injectors was discussed and a synchronous drive controller is designed based on spray time sequence.The drive circuits were verified by the current waveform measured by current clap and parameters of spray characteristics gotten form experiments. Based on MATLAB, spray image processing programs were written, which make use of SUSAN algorithm and morphology operation to accurately and quickly get the edge of spray images obtained from a high-speed camera. The parameters of spray characteristics such as overall spray cone angle and spray penetration can be calculated by the spray image outline.The influence of injection pressure, back pressure and temperature in a constant volume chamber on the spray characteristics was studied. The conclusions are as follows.The injection pressure has little influence on the overall spray cone angle. However, increased injection pressure may significantly reduce spray penetration and improve fuel vaporization.The back pressure in the constant volume chamber also has little influence on the overall spray cone angle and significant influence on the spray penetration, which is apparently reduced by increasing back pressure. The increased back pressure can effectively decrease the speed of fuel vaporization, which is of disadvantage to the mixing process of fuel and air.The increased temperature in the constant volume chamber may increase the speed of fuel vaporization and spray penetration which however has little influence on the overall spray cone angle.The research is great worth to the research and development for combustion system of GDI engine and verifying the validity of 3-D numerical simulation results.