Spray and atomization characteristics of gas-centered swirl coaxial injectors

Abstract

To achieve uniform and efficient combustion in a rocket engine, a fine uniform spray is needed. The same is achieved by designing an injector with good atomization characteristics. Gas-centered swirl coaxial (GCSC) injector elements have been preferred recently in liquid rocket engines because of an inherent capability to dampen the pressure oscillations in the thrust chamber. The gas-centered swirl coaxial injector chosen for this study is proposed to be used in a semi-cryogenic rocket engine operating with oxidizer rich hot exhaust gases from the pre-burner and liquid kerosene as fuel. In this paper, nine different configurations of gas-centered swirl coaxial injector, sorted out by studying the spray angle and coefficient of discharge with swirl number varying from 9 to 20 and recess ratio of 0.5, 1, and 1.5 are investigated for their atomization characteristics. Spray uniformity, spray cone angle, and droplet size in terms of Sauter mean diameter and mass median diameter are studied at various momentum flux ratios for all configurations. Sauter mean diameter is almost independent of recess ratio, whereas cone angle was inversely proportional to the recess ratio. A finer atomization was observed for injectors of high swirl number but the pressure drop also increased to achieve the same flow rate. An injector of medium swirl number and recess ratio of 1.5 is deemed most fit for above-mentioned application.

Experimental Study of Spray and Combustion Characteristics in Gas-Centered Swirl Coaxial Injectors: Influence of Recess Ratio and Gas Swirl

“…The experiment used four injector types, as shown in Figure 1. Given that the GCSC injector mixes gas and liquid within a designated length denoted as L R before expelling it from the injector outlet for combustion, the recess length emerges as a crucial shape variable significantly impacting combustion performance [18]. The recess length is defined as the dimensionless recess ratio (see Equation ( 1)).…”

“…Variance in spray angle and droplet size distribution were noted, with LCSC injectors demonstrating self-pulsion traits under specific conditions. Anand et al [18] examined changes in spray angle and droplet size concerning variations in swirl number and recess ratio under various momentum-flux ratios, evaluating the influence of variables. Canino et al [19] analyzed the unsteady hydrodynamic characteristics of GCSC injectors using a numerical method and examined the influence of gas and liquid properties and geometry.…”

Influence of Mass Flow Rate on the Atomization Characteristics of Screw Conveyor Swirl Injectors

“…Chen Chen et al [11] researched the influences of different pressure drops and ambient pressures on the spray angle and discharge coefficient of an open-end swirl injector and obtained the images of the atomization field by using a high-speed shadowgraph system. Rahul Anand et al [12] studied the influences of the swirl number and recess ratio on the atomization characteristics of a gas-centered swirl coaxial injector and analyzed the particle size by using a Malvern particle sizer.…”