A Measurement of Instantaneous Flow Rate of an Automotive Gaseous Fuel Injector

Injection rate measurement of an automotive gaseous fuel injector was carried out by use of a one-dimensional pipe flow. A production gaseous fuel injector for an NGV (Natural gas vehicle) was used, which is for an intake port fuel injection. The injection pressure was set at 255 kPa(g), and the injection duration was varied from 3.4 to 20 msec. Nitrogen gas was used as the test gas. The test gas was injected into a pipe from the injector, and the static pressure history was acquired with a piezoelectric pressure transducer. One-dimensional, compressible, inviscid, adiabatic flow was assumed, and the instantaneous mass flow rate inside the pipe was estimated. By integrating the injection rate during the injection duration, the total amount of mass flow per one stroke was calculated. Calibration test was carried out by use of a pressure vessel, from which the total mass flow during one stroke was estimated. Both data are compared, and it is shown that the injection rate measurement was carried out with an error of about 10 %.