In-water injection of high-pressure pulsed gas jet: A simple analytical tool for direct injection of gaseous fuels in automotive engine

Abstract

Visualizing high pressure pulsed gas jet can be challenging due to its weak scattering of light which requires reliable flow tracer. Complex and costly laser source and high speed camera settings using shadowgraph, Schlieren and Laser Induced Fluorescent (LIF) techniques with seeding of flow tracers such as acetone have been used. In the spirit of simplification, this paper presents a technique to visualize high pressure pulsed gas jet in liquid ambient. It can be used as predictive tool to investigate the structure, dynamic and interaction of gas jet with the environment [1]. A gas injector with square-shaped nozzle was used. High pressure nitrogen gas at 5 and 6MPa with 12ms injection pulse exits the injector through a 1mm2 square nozzle into quiescent water. The injector tip is immersed below water surface in an optically-accessed container and placed inside an extremely low illuminated square chamber. Two small windows on opposite walls of the chamber allow image capturing with injection-flash light synchronization. Images of the gas jets formed from nozzle at various time after the start of the injection (SOI) were captured by a digital camera. During exposure, the flash light was triggered for 1ms at some times after SOI, thus images captured correspond to the flash timing.Results showed that the shape of the gas jet was in agreement with the vortex ball model but with difference in the magnitude of penetration with respect to previous works. Some similarities in the gas injection behavior are found in the liquid and gas ambient. The tip penetration and gas width in water environment are about half of the magnitude in the gas environment. A dimensionless gas dynamic analysis shows a good agreement in the trend of jet development between the gas environment using Planar Laser Induced Fluorescent (PLIF) imaging and in-water imaging techniques. Results indicate that both gas jet length and width are very sensitive to injection pressure.