Injection Timing Evaluation of a Compressed Natural Gas Direct Injection Engine Based on Experimental Data and One-Dimensional Simulation

Abstract

Compressed Natural Gas (CNG) is a widespread hydrocarbon fuel in power generation, commonly injected upstream from the intake valves of an internal combustion engine, reducing volumetric efficiency and consequently power density. Recent developments use Direct Injection (DI) to overcome these losses. Some aspects regarding injector construction, injection pressures and flow rates are essential to the success of CNG - DI. This paper demonstrates the usefulness of a one-dimensional simulation tool such as GT-Power to check injector capabilities under operational conditions. The main parameter analyzed was volumetric efficiency for different injection timings, which is directly proportional to the maximum engine power output for a given speed and air to fuel ratio. Simulation was calibrated using experimental data from a Single Cylinder Research Engine (displacement of 2059 cm³).