Effects of Different Port Injection CNG System Configurations on a 3.8L V6 Engine

Abstract

In light of sustainable mobility and increased fuel prices in Australia, vehicles and engines operated on gaseous fuel are becoming more popular. This paper investigates the effects of different aftermarket compressed natural gas (CNG) fuel delivery system configurations on combustion stability, fuel economy and emissions utilising a commercially available internal combustion engine (ICE). The investigated parameters include the effects of the injector location in relation to the intake manifold as a function of engine speed/load, equivalence ratio as well as injection and ignition timing. Using a combination of computer simulation tools and experiments, effects on the engine and its mechanisms are clarified. A 1D model (Lotus Engine Simulation) of the engine is used to produce realistic pressure fluctuations and flow velocities at the injector nozzle position in the intake manifold, for different engine operating conditions. A computational fluid dynamics code (ANSYS) is used to investigate the fuel distribution in the intake manifold and pulsations in the injection system. The CNG jet was visualized in a spray vessel using Schlieren techniques to increase understanding of the gaseous jet behavior. And finally, the computer simulations and spray visualisations are evaluated together with experimental data to explain the engine’s behaviour as a function of different fuel system configurations.