Experimental study on the effect of nozzle geometries on twin jet flow characteristics

Abstract

Jets issuing from two convergent nozzles kept parallel to each other at a certain distance is termed as twin jet. The need for non-circular nozzles aroused as the necessity for faster large scale and small scale mixing, increased spreading rate and better maneuverability increases. There is less work found in the literature on twin jet issued from two different geometry nozzles. The combination of circular nozzle with non-circular one is a unique technique to enhance mixing and to study other flow characteristics. The main objective of this work is to experimentally study the flow characteristics of twin jet issuing from a combination of both circular and non-circular convergent nozzles. The nozzle configurations used in this present study for creating twin jet are circle-circle, circle-ellipse, circle-hexagon, circle-square, circle-star and circle-triangle. The experimental work gives an insight about various flow characteristics such as jet flow structure and its development, mixing of two jets at various Mach numbers. newlineIn this study, experiments have been carried out for Mach numbers 0.4, 0.6, 0.8 and 1 in both axial, radial directions and also for underexpanded conditions (Nozzle pressure ratios i.e., NPR 2, 3 and 4). The Mach number is non-dimensionalized (M/Me) and plotted against X/D ratio (the axial distance X is non-dimensionalized with circular exit diameter D). The centerline is the line from the center of the nozzle spacing and extends along the axial direction which is taken as a line of reference in this experiment. From CMD profiles, it is observed from the merge point and combined point that the mixing occurs faster in twin jet from circle-ellipse nozzle than twin jets from other nozzle configurations. However, for twin jets from circle-circle and circle-hexagon nozzle configurations, the merging and combined point occurs later. newline