Experimental study on fuel line pressure fluctuation of biodiesel–DME blends in a common-rail injection system

Abstract

The fuel line pressure fluctuations at the injector outlet of biodiesel–dimethyl ether (DME) blends in a common-rail injection system are investigated using the wavelet packet transform. The effects of injection condition and DME blending ratio on the pressure fluctuation characteristics are determined. The results show that the pressure fluctuation intensity determines wavelet packet energy distribution in the three subsignals. The overall pressure fluctuation is reflected by subsignal Sig1, which is composed of subsignals Sig2 and Sig3. Sig2 exhibits medium-frequency pressure fluctuations, and mainly occurs in the pressure rise stage and the pressure drop stage. Sig3 exhibits high-frequency pressure fluctuations, and mainly locates in the pressure stabilization stage. The pressure fluctuations at high injection pressure are more significant compared with those at low injection pressure. Biodiesel–DME blends display similar effects of injection pressure. With the increase of injection pressure, the mean energy and the standard deviation of Sig1, Sig2, and Sig3 increase, especially those of Sig1 and Sig3. When DME is blended in the biodiesel, the pressure fluctuations for biodiesel–DME blends are more significant compared with biodiesel. With the increase of DME blended ratio, the mean energy and the standard deviation of Sig1 and Sig3 gradually increase.