Improvement of Injection Rate Measurement Accuracy of a Gaseous Fuel Injector

Abstract

Accuracy of an injection rate measurement of a gaseous fuel injector was improved by modification of equations and static pressure correction. 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 5 to 20 ms. 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 piezoelectronic pressure transducer. One-dimensional, compressible, inviscid, adiabatic flow was assumed, and the instantaneous mass flow rate inside the pipe was estimated using newly modified equations. The pressure gradient due to pipe friction was corrected using Darcy-Weisbach equation. By integrating the injection rate during the injection duration, the total amount of mass flow per one stroke was calculated. The data obtained by the injection rate meter are compared to that of the calibration test, and it is shown that the injection rate measurement was carried out within the error of 2 to 3%