Experimental Evaluation of the Influence of the Diameter of the Outlet Nozzle Bore of a Gas Injector on Its Flow Characteristic

Despite the growing share of electrically powered vehicles, internal combustion engines are still one of the primary sources of propulsion in transportation. One way to decarbonize engines is to use alternative fuels, where liquefied petroleum gas (LPG) accounts for a large share. Popular car gas systems are LPG indirect vapor phase injection systems, in which the low-pressure gas-phase injector is the actuator. The purpose of the research and analysis presented in this paper is to determine the flow characteristics of three injectors that are structurally different depending on the diameter of the outlet nozzle bore. The tests are conducted, which is new, with pulsed operation of the injector, which, as it turned out, helps explain the discrepancies found. The obtained characteristics are fitted with a polynomial of the second degree, obtaining high-quality indices. In the group of three tested injectors, the average values of volumetric flow rate decreases relative to the maximum by 19.6 and 35.8%. Differences in opening times of 29.3 and 36.6%, respectively, are cited as one of the main reasons for this. Closing times are similar to each other. In addition, the injector with the highest volumetric flow rate and the shortest opening time obtains 1.8 and 9.94% lower average cycle pressures measured at the outlet of the injector nozzle. The differences in opening times and average cycle pressures are considered as possible reasons for the differences in flow characteristics. The obtained characteristics are applicable to engine conversions and calculations.