There are many noise sources from the vehicle fuel system to generate noise inside a vehicle. Among them, the pressure pulsation due to the rapid opening and closing of gasoline engine injectors can cause undesirable fuel pulse noise. As the pressure pulsation propagates in the fuel supply line toward to rear end of the vehicle, the pressure energy is transferred from fuel lines to the vehicle underbody through clips and into the passenger compartment. It is crucial to attenuate the pressure pulsation inside the fuel line to reduce the fuel pulse noise. In this paper, a case study on developing an effective countermeasure to reduce the objectionable fuel pulse noise of a V8 gasoline injection system at engine idle condition is presented.
First, the interior noise of a prototype vehicle was tested and the objectionable fuel pulse noise is exhibited. The problem frequency ranges of the pulse noise were identified. In order to find the countermeasures to reduce the pulse noise, several test iterations were conducted. It was found that adding the expansion chamber in the fuel line is an efficient countermeasure to reduce the fuel pulse noise in the problem frequency range. Secondly, a one-dimensional (1D) simulation model based on GT-Suite was developed to analyze the wave dynamic behavior of pressure pulsation in the fuel line. The early expansion chamber used in the initial test was evaluated by the simulation model and good correlations are obtained between the simulation and the test results. Then, several expansion chamber designs based on the package space were analyzed by the developed simulation model. The expansion chamber design which reduced the pulsation most effectively and also met the package requirements was recommended. Finally, the recommended expansion chamber was built and the interior noise with the design in the fuel line was tested. The results showed that the fuel pulse noise was reduced to accept level and met the NVH development requirements.
From this study, it was concluded that proper countermeasures need be implemented to attenuate the fuel pulse in different problem frequency ranges. An accurate simulation model can efficiently evaluate different technologies to reduce the pressure pulsation in the fuel line and assist developing timely NVH solutions for a production launch of a vehicle.