Title:
Internal Flow Dynamics in Liquid Swirl Injectors with Coaxial Gas Flow
Internal Flow Dynamics in Liquid Swirl Injectors with Coaxial Gas Flow
Author(s)
Trucchi, Matteo
Advisor(s)
Yang, Vigor
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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. Thus, 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-head injectors, where the liquid propellant swirls around a stationary gas core. Gas-liquid interactions were introduced with recessed coaxial swirl injectors and air-blast injectors with major emphasis on the atomization process. The classical theory on injector dynamics lacks the consideration for the effect of the shear stress at the liquid-wall and gas-liquid interfaces in the governing equations. Therefore, the damping effect on propagating waves is modelled exclusively through an artificial viscosity factor.
This work conducts a theoretical and numerical investigation for an alternative configuration of open-end swirl injectors. The distinctive feature of this configuration is an open head and a high speed gas that flows coaxially with the swirling liquid towards the injector exit. Unlike a recessed coaxial injector, the gas immediately interacts with the tangentially injected liquid into the chamber where the gas is flowing. The comprehensive review of classical steady-state and transient theories on swirl injectors led to the identification and resolution of inconsistencies. The analytical inclusion of shear stress at the liquid-wall and gas-liquid interfaces produced a modified wave equation, and the new solution was employed to extend the classical theory to Open-Head-Open-End injectors. A parametric study for frequencies up to 2000 Hz involving gas flow velocity, injector pressure drop, and geometric parameters highlighted the significance of friction coefficients tuning for an accurate calculation of the injector transfer function. Computational Fluid Dynamics provided a qualitative description of the flow physics involved in the injector configuration of interest.
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Date Issued
2023-12-06
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