Resonator Design Study to Reduce Pressure Pulsation from CNG Injector

With the advent of upcoming stringent automobile emission norms globally, it is inevitable for original equipment manufacturers (OEMs) to shift towards greener alternatives. Use of compressed natural gas (CNG) is a preferred solution as it is a relatively clean burning fuel and it doesn’t have significant loss in vehicle efficiency and performance. Modern day customers are more aware and sensitive towards vehicle noise, vibration and harshness (NVH). Hence, OEMs must cater to this demand through optimized design and layout. In a passenger vehicle, CNG is stored at high pressure and delivered to injectors after pressure reduction at a regulator. During engine idling, the opening and closing motion of the CNG injector generates back pulsation and these pulsations cause vibrations which may propagate through other components in the delivery path and perceived as noise inside vehicle cabin. To identify the frequencies involved in pressure pulsation, a 1-D simulation of CNG fuel system is performed using commercially available simulation software GT-Suite through which excitation frequencies and pressure pulsation peak amplitude has been identified. To validate the model, actual pulsation measurement testing has been performed and pressure peaks amplitude are compared with simulation. Based on correlation with actual testing, multiple resonator designs are created to dampen the identified excitation frequencies range. These designs have been virtually validated for pressure peak reduction by simulating resonators with fuel system layout in GT-Suite.