Aerodynamic design of a multi-point operational high-speed inlet

Buanga, Björn Heinrich

Abstract

In air-breathing supersonic transport aircraft the efficiency of the engine inlet has a huge influence on the engine and the aircraft performance. Nowadays, variable inlet geometries allow optimised inlet geometries and by this also maximum performance at multiple Mach numbers. The downside of this approach is the high weight fraction of the variable geometry mechanics. Determining and evaluating alternative approaches in computational fluid dynamic (CFD) simulations is the intention of this research.
Discussing state-of-the-art flow control methods leads to the most promising method, shock angle increase by mass flow injection at the beginning of the compression ramp. The concept is found in the literature but no further flow investigations have been acknowledged. Effort to increase the understanding in this particular area is done in this study by CFD simulations. Firstly, a validation of the used axisymmetric-injection and extraction boundary conditions is accomplished. After that, in quasi-three-dimensional simulations a parameter sensitivity study about the injection total pressure and injection angle is performed on a two-ramp axisymmetric configuration and on NASA’s Hypersonic Research Engine inlet geometry, which was extensively studied in wind tunnel experiments. With the obtained knowledge of the axisymmetric injection simulations, there follows three-dimensional analyses of the identical inlet to confirm the findings of the preliminary study. In addition, the flow control possibilities and its behaviour are investigated at a small angle of attack. Finally, this dissertation concludes with a summary of the key findings.
Concerning the results chapters, validation of the relevant boundary conditions verifies that the used flow solver, the DLR TAU-Code, ensures correct and accurate results. In the preliminary analysis, the influence of the injection angle is analysed. It turns out that best performance can be achieved when injecting with an angle of 45° to the main flow direction. In the following studies, the influence of further injection parameters, total pressure and total density, is evaluated. The injection total pressure is identified as the main parameter influencing the shock angle. In concluding studies, it is shown that the total pressure recovery of a Mach 6 inlet in a Mach 8 freestream flow can be enhanced by 9.5 %, when injecting 0.9 % of the captured mass flow rate at the centre-body tip, in comparison to the non-controlled case at the same Mach number.
Finally, in asymmetric flow around an inlet at a 3° angle of attack it was investigated, whether the flow control by injection can be used for performance increases. The results were indicating that the applied asymmetric injection is not leading to performance increases in the selected configurations. However, it is shown that asymmetric injection, in the chosen configuration only at the lower inlet side, influences the flow field around the complete inlet, when regarding a position considerably downstream of the injection.

• Thesis Type: Thesis
• Publicly Available Date: Jun 6, 2019
• Keywords: supersonic flow control, shock angle control, hypersonic research engine, mass flow injection, injection validation, extraction validation
• Public URL: https://uwe-repository.worktribe.com/output/811744
• Award Date: Sep 23, 2014