Master's Thesis Proposal 

Matteo Trucchi

(Advisor: Prof. V. Yang)

"Internal Flow Dynamics in Liquid Swirl Injectors with Coaxial Gas Flow"

Wednesday, August 30 

9:00 a.m.

Montgomery Knight Building 325

Abstract

Injectors are essential components in aerospace propulsion systems, serving a crucial role in achieving high-quality propellant atomization and mixing, as well as engine stability. They are integral components within a complex dynamic system and are responsible for coupling the feed system to the combustion chamber. A profound understanding of injector dynamics is imperative to attain a robust engine design.

Since the early studies, the typical configurations of interest have involved closed-end and open-end swirl injectors. Both these designs feature a closed head-end where the liquid propellant tangentially enters the vortex chamber. Therefore, the liquid has only a tangential velocity component at the head-end, and gains axial velocity as it proceeds towards the combustion chamber. Previous theories rely on axisymmetric models for the swirling flow and do not account for the shear stress at the interface between the swirling liquid and the gaseous core, due to small relative velocity in the axial direction. Furthermore, past models introduce an artificial viscosity factor to account for oscillations damping.

This work proposes to conduct a theoretical and numerical study of an alternative configuration for open-end swirl injectors. The distinctive feature of this configuration is an open head, and a high speed gas flow that moves coaxially with the swirling flow towards the injector exit. The effect of shear stress at the gas-liquid and liquid-wall interfaces is taken into consideration. Thus, the wave equation for disturbance waves in the liquid flow will be modified, producing a new wave speed and an analytical damping or amplification factor. The theoretical impact on current models will be addressed. In addition, comprehensive and systematic numerical simulations will allow the computation of the injector transfer function for a range of oscillation frequencies 0-3000 Hz. The effect of gas flow velocity, pressure drop, and geometry variation will be investigated. Geometrical parameters of interest are vortex chamber diameter and length, number and diameter of inlet channels. Finally, numerical results will be compared to analytical findings.

Committee

• Prof. Vigor Yang – School of Aerospace Engineering (advisor)
• Prof. Adam Steinberg – School of Aerospace Engineering
• Prof. Joseph Oefelein – School of Aerospace Engineering