Method and apparatus for dispensing natural gas

摘要

A supply plenum connected to a source of compressed natural gas (CNG) and a control valve assembly for selectively turning on the flow of CNG through a sonic nozzle and out through a dispensing hose assembly. Pressure and temperature transducers connected to the supply plenum measure the stagnation pressure and temperature of the CNG and the ambient temperature, and a pressure transducer fluidically connected to the vehicle tank via the dispensing hose assembly monitors the discharge pressure of the CNG. An electronic control system connected to the pressure and temperature transducers and to the control valve assembly calculates a vehicle tank cut-off pressure based on the ambient temperature and on the pressure rating of the vehicle tank that has been pre-programmed into the electronic control system and automatically turns off the CNG flow when the discharge pressure reaches the cut-off pressure and determines the amount of CNG dispensed through the sonic nozzle based on the stagnation temperature and the stagnation pressure of the CNG and the length of time the CNG was flowing through the sonic nozzle.