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Ph.D. Thesis Proposal by
(Advisor: Prof. Vigor Yang)
Tuesday, September 5th, 2017 @ 1:30 p.m.
Montgomery Knight Building Room 317
Abstract:
Recent efforts led by the Air Force Research Laboratory (AFRL) aim to help transition US-based rocket manufacturing from conventional gas-generator cycle Liquid Rocket Engines (LREs), such as the Saturn V's F-1 engine and Space Shuttle Main Engine (SSME), to higher performance closed-cycle designs such as the oxidizer-rich staged combustion (ORSC) cycle employed in many Russian-developed engines including the RD-180. Even as conventional LREs are being driven to higher chamber pressures to meet the requirements of next-generation payload delivery, combustion instabilities remain nearly impossible to predict a priori. These high-amplitude pressure oscillations become exceedingly dangerous as the energy density of the thrust chamber assembly (TCA) increases, leading to catastrophic structural failures and expensive engine testing programs. Bringing instability prediction on-line in the design process would both reduce costs and improve safety drastically, and one particularly promising avenue combines the robust modal analysis of a linearized acoustic solver with the detailed physics captured by high-fidelity simulations, providing a framework by which rapid prototyping of engine designs becomes computationally feasible.
The proposed research investigates a novel approach for modeling the response of TCA injectors to acoustic excitation, using Large Eddy Simulation (LES) to capture the detailed physics in turbulent reacting flowfields representative of full scale ORSC engines. Single element simulations will be conducted on both full and reduced computational domains, while reduced-domain multi-element simulations are proposed to specifically investigate proximity effects of both bordering elements and combustion chamber walls. Dynamic Mode Decomposition (DMD) is used to precompute the combustion response terms for incorporation into a COMSOL-based linearized acoustics model for rapid prediction of natural acoustic modes and their associated linear growth rates. Single and multi-element sub-scale ORSC experiments conducted by the Georgia Tech Combustion Lab and NASA Marshall Space Flight Center (MSFC) serve as benchmarks for both direct validation of the LES accuracy and demonstration of the predictive capabilities of the overall framework.
Committee Members:
Dr. Vigor Yang (Advisor)
Dr. Timothy Lieuwen
Dr. Lakshmi Sankar
