연료 레일 체적이 가스분사 특성에 미치는 영향(2) - 레일 내부 압력 변동 특성

This study is to investigate the characteristics of fuel rail pressure fluctuation according to fuel injection pressure, injection pulse width and engine speed in a gas fuel injection system. The fuel rails with the volume of 5, 100, 200, and 435 cc were used. Compressed air was used as an analogous fuel, and injection was controlled using an injector driver. A pressure sensor, a piezo-resistive amplifier, and an oscilloscope were used. The pressure waveform was averaged by measuring 100 times. The injection pressures were set at 1.5, 3.0, 4.5 and 6.0 bar, and the engine speeds were set at 750, 1000, 1500, 2000, 3000, 4000, 5000 and 6000 rpm and injection periods were 3, 5, 8 and 13 ms. As the engine speed increased and the injection pulse width became longer, the pressure inside the fuel rail decreased drastically and the pulsation phenomenon gradually disappeared. Increased engine speed and injection period started to connect almost continuously in the period of operation of the injector and overlapped each other finally. It was believed that the fuel rail was not supplied with additional fuel enough to recover the pressure due to an increase in injection flow rate than the increase in supply volume of the pressure regulator. Regardless of the volume change, the tendency of the in-rail pressure drop was very constant, but the pressure fluctuation decreased as the volume of the fuel rail increases, contributing to securing the fuel injection stability to some extent. Since the reduction in rail pressure did not ensure the required injection flow rate under full load conditions. Therefore, it is necessary to devise a method for maintaining the pressure inside the rail.