Visualization and Analysis of Gaseous Jet Process for an Outward-Opening Nozzle 2019-01-0275
In this article, the effects on the jet process of natural gas through an outward-opening nozzle were analyzed at different injection pressures. Visualization and analysis of the jet process is based on schlieren methods. High speed schlieren imaging is used to capture the growth of transient gaseous jet in a quiescent chamber at atmospheric conditions. The schlieren images collected by high speed camera are automatically processed through Matlab program. The characteristic parameters of gas jet were obtained such as jet radial and axial penetrations, spread angle, jet radial and axial velocity, jet area and jet volume etc.
Experimental results showed that the axial and radial penetrations increase with increasing injection pressure. The increasing rate of penetrations decreases while the injection pressure exceeds a certain value. This trend is more significant in the radial direction. The radial penetration characteristics are different from the axial penetration characteristics for all injection pressures. The spread angle decreases as the gas jet advances at the initial phase of the injection which indicates that the jet curves inwards along the axis of the nozzle. After this phase, the spread angle decreases slowly. The spread angle increases with increasing injection pressure. After the jet pressure exceeds a certain value, the spread angle decreases with an increase in injection pressure. The radial and axial jet velocity increase during the initial phase of jet. The velocity in both directions peaks when the injector is fully opened. After the injector is fully opened, the gas jet experiences drastically deceleration. The jet area and volume increases with an increase in injection pressure and both quantities show a similar increasing trend. The rate of increase reduces with an increase in injection pressure, which is similar to penetration rates.
The study about the effects on the jet process of natural gas through an outward-opening nozzle, which is based on the visualization experiment, provide the basis for the establishment of gas injection numerical model, and make preparations for the development of efficient and clean natural gas engines.
Jianhui Zhao, Weilong Liu, Leonid Grekhov