Date of Award

5-2016

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Graduate Studies

Committee Chair

Dr. Mark Ricklick

First Committee Member

Dr. Eric Perrell

Second Committee Member

Dr. Habib Eslami

Abstract

Jet impingement cooling is an internal cooling configuration used in the thermal management of temperature sensitive systems. With rocket engine combustion temperatures rising as high as 3600 K, it is essential for a cooling method to be applied to ensure that the nozzle integrity can be maintained. Therefore, a novel heat transfer study is conducted to investigate if jet impingement cooling is feasible for a regenerative cooling rocket nozzle application. Regenerative cooling for liquid propellant rockets has been widely studied. However, to the best of the author’s knowledge, there is currently no literature describing this method in conjunction with impingement cooling techniques.

In this study, a literary empirical model my Martin (1977) is compared to a computational fluid dynamics (CFD) model designed for single and round nozzle (SRN) jet impingement with conjugate heat transfer (CHT) analysis. The CHT analysis is utilized to investigate the resulting surface temperatures in the presence of convection and lateral conduction effects while investigating the Nusselt number (Nu) and temperature profiles of the impingement configuration. Heat transfer data is first extracted for air impinging onto a heated flat plate, whose results are used as the benchmarking model.

The model is then altered to assess its application feasibility for a regeneratively cooled rocket nozzle throat similar to that of the Space Shuttle Main Engine (SSME) with LOX/LH2 propellants. A 1-D thermal analysis of supercritical LH2 coolant at 52.4 K and 24.8 MPa for the SSME with various nozzle wall materials, such as Stainless Steel 304 (SS 304), Inconel x-750, copper and ABS plastic, is conducted. The material selections were chosen to cover a range of thermal conductivities. It was found that none of the selected materials are feasible with impingement cooling alone due to the extremely high heat transfer rates within the throat.

With material temperature limitations below 200 K. the materials cannot withstand the high stresses acting on the nozzle even with alterations to the benchmark model. Therefore, it is concluded that an additional cooling method is required to increase the hot-side thermal resistance. To ease the thermal stresses on the remaining metals, an average film cooling effectiveness (n) of 0.5 was assumed, to stimulate the benefit of film cooling. Having been incorporated into the hot gas side calculations, it decreased the adiabatic wall temperature from 3561 K to 1667.3 K, allowing the materials to be properly cooled on the inner side of the nozzle. Even with this assisted cooling method added, it is concluded that only SS 304 and Inconel x-750, with their low material resistance and high temperature capabilities, were capable of withstanding the rocket nozzle temperatures. CFD simulations for these two materials are studied for their feasibility of a SSME-like nozzle throat region. It was concluded that film cooling cannot be eliminated from the system with the SSME parameters studied. Additionally, with minimal differences between the 1-D analysis and CFD simulations, lateral conduction effects are minimal, which proves 1-D analysis is sufficient for future analysis.

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