Resonator design study to reduce pressure pulsation from CNG Injector

With the advent of upcoming stringent automobile emission norms globally, it is inevitable for OEMs to shift towards greener alternatives. Use of 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. Current customer has become aware and sensitive towards vehicle NVH. Hence, OEMs have to 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 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 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.