Ways to reduce the failure rate of high-pressure fuel lines？

Abstract:

A study on the fluctuation of residual pressure of high-pressure fuel pipe of diesel engine was carried out by using AMESIM simulation software, which analyzed the influencing factors of residual pressure, eliminated the unfavorable factors, and selected the parameters, to reduce the failure of high-pressure fuel pipe.

1 Introduction

The reliability of diesel engines occupies a higher and higher proportion, and the working conditions of diesel engines are harsh. At present, to achieve the Euro II emission standard, the injection pressure of direct injection diesel engines should be not less than 80~100MPa, and some of them have higher injection pressure to achieve the Euro III standard, or to realize the higher requirements [1]. Therefore, the fuel injection system of the high-pressure fuel pipe needs to withstand a huge load, and the pipe alternately reciprocates fluctuations in pressure, resulting in diesel injection efficiency and injection volume fluctuation changes, affecting the diesel engine ignition and combustion performance. In this paper, the use of the AMESim simulation model, the study of diesel engine residual pressure fluctuations in the residual pressure factors, to improve the working conditions and performance of diesel engines.

2 Modeling

A diesel engine's high-pressure fuel pipe is connected to the injection pump at one end, the other end is connected to the injector, the high-pressure fuel pipe is subject to reciprocating pressure fluctuations, the fluid in the high-pressure fuel pipe can be regarded as a one-dimensional fluid is not constant, this paper utilizes the AMESim simulation model [2], through the experimental state of the ideal data, the control variables, observe the residual pressure of the fuel pressure at the nozzle end, and then find out the influencing factors of the fluctuation of the residual pressure.

3 Experimental study

In the experiment, the basic parameters are: camshaft speed is 500r/min, high-pressure fuel line length is 0.9m, the thickness of the fuel line is 2.25mm, the diameter of the fuel line is 1.8mm, and the diameter of the nozzle hole is 0.26mm. Firstly, the length of the fuel line is changed, and the contrasting parameters is 0.8m and 1m, as shown in Fig. 1, with the increase of the length of the line, the peak of the residual pressure fluctuation increases significantly, but the wavelength is relatively small, which also determines that the line can not be made to be the same length. It also determines that the pipeline can not be made too long, is easy to the second injection of the injector; can not be too short, and will cause fuel injection instability. Secondly, change the thickness of the high-pressure fuel line, the comparison parameters are 2mm and 2.5mm, as shown in Fig. 2, it can be found that, with the increase of the thickness of the high-pressure fuel line, the peak value of the residual pressure wave does not change, the phase is delayed, the wavelength becomes longer, and the residual pressure decays more quickly, and then change the diameter of the high-pressure fuel line, the comparison parameters are 1.7mm and 1.9mm, and the experiments found that, with the increase of the diameter of the high-pressure fuel line, the wavelength becomes shorter, the wavelength is shorter, and the residual pressure decays faster. The experimental results show that, with the increase of the diameter of the high-pressure fuel pipe, the wavelength becomes shorter, the wave peak decreases, but there are irregular fluctuations, and the aperture diameter should not be too small, otherwise, it will increase the pulsation, which is due to the throttling effect as the aperture diameter decreases; finally, change the diameter of the orifice of the nozzle, which has a significant effect on the characteristics of the injection, and the comparative parameters are 0.28mm and 0.24mm, as shown in Figs. 3 and 4, and it is found that, with the change in the orifice diameter, the residual pressure will also change accordingly [1]. Through the experimental comparison found that, with the change of orifice diameter, the residual pressure will also produce corresponding changes [3], orifice diameter increases, the residual pressure wavelength becomes smaller, but the peak value is increased accordingly, which will abnormal injection [4], at the same time, this is also the main factor of fuel atomization is poor, but the diameter of the orifice is too small, it will to the increase in the frequency of the reciprocal propagation of the pressure wave inside the tube, resulting in the pipeline is unstable, and the pulsation is increased.

4 Conclusion

In this paper, we use a simulation model and control variable method to study the influence factors on the residual pressure of high-pressure fuel pipe.