Reduction of Pulsation Noise in CNG Vehicles

Natural gas is increasingly being utilized for vehicle applications both to reduce vehicle emissions and as an alternate energy source to gasoline and diesel fuels. Natural gas can be used to reduce carbon dioxide emissions while the global distribution of natural gas allows energy independence for regions with gas rather than oil reserves. Thus natural gas as alternative vehicle fuel not only provides emission benefits but also provide an economical option in comparison to the Hybrid and Electric Vehicles. An increasing number of vehicles worldwide are being manufactured to run on CNG. CNG/NGV vehicles produce 20-30% less carbon dioxide than gasoline and diesel [1]. The CO₂ contributes to global climate change due to greenhouse effect. Further CNG vehicles decrease noise pollution by having a smoother and more silent engine performance compared to gasoline and diesel engines.

The CNG injection technology is developed to obtain engine performance equivalent to gasoline engines unlike the conventional venturi system wherein the performance and drivability is compromised. One of the major challenge associated with using injector based CNG system is cabin noise due to the injector noise. The operational metallic and gas pulsation noise associated with sequential functioning of the gas injector is generally higher as compared to liquid fuels like gasoline due to dry nature of the CNG fuel. This paper describes the methodology adopted for reduction of CNG injector noise and suggests an experimental set up to predict the noise at early design stage. Experimental data suggests correlation between bench simulation and actual vehicle noise. The iterative process followed for improving the NVH performance by measurement of operational and gas pulsation noise from CNG injector can thus be avoided to reduce overall development time.