A numerical investigation of the cooling effect of compressed natural gas throttling on engine delivery ratio

A theoretical study was conducted to investigate the cooling effect of thro ttling compressed natural gas during the pressure regulation process. The c oncept of using this effect in cooling down the induction air was investiga ted. A thermodynamic model was developed for a typical fuel delivery system used on a vehicle fueled with compressed natural gas. The model was based on a set of integral conservation laws applied to each component of the fue ling system. Several heat exchanging arrangements between the throttled gas and the inlet air were examined. The effect of rite added heat exchanger o n engine delivery ratio was examined for different engine sizes as well as for different operating conditions. An increase of 1 to 2.5% in engine deli very ratio was predicted due to the added heat exchanger.