Shock tunnel studies of scramjet phenomena

Commissioning of the new T4 shock tunnel at the University of Queensland implied that it was no longer necessary to focus the work of the research group about an annual test series conducted in the T3 shock tunnel in Canberra. Therefore, it has been possible to organize a group for work to proceed along lines such that particular personnel are associated with particular project areas. The format of this report consists of a series of reports on specific project areas, with a brief general introduction commenting on each report. The introduction is structured by project areas, with the title of the relevant report stated under the project area heading. The reports themselves follow in the order of the project area headings

A Survey of Gaps, Obstacles, and Technical Challenges for Hypersonic Applications

The object of this study is to canvas the literature for the purpose of identifying and compiling a list of Gaps, Obstacles, and Technological Challenges in Hypersonic Applications (GOTCHA). The significance of GOTCHA related deficiencies is discussed along with potential solutions, promising approaches, and feasible remedies that may be considered by engineers in pursuit of next generation hypersonic vehicle designs and optimizations. Based on the synthesis of several modern surveys and public reports, a cohesive list is formed, consisting of widely accepted areas needing improvement and falling under several general categories. These include: aerodynamics, propulsion, materials, analytical modeling, CFD modeling, and education in high speed flow physics. New methods and lines of research inquiries are suggested such as the homotopy-based analysis (HAM) for the treatment of strong nonlinearities, the use of improved turbulence models and unstructured grids in numerical simulations, the need for accessible validation data, and the refinement of mission objectives for Hypersonic Air-Breathing Propulsion (HABP)

Impact of Vibrational Nonequilibrium on the Simulation and Modeling of Dual-Mode Scramjets

The practical realization of supersonic flight relies on the development of a robust propulsion system. These air-breathing scramjet engines process fuel and high-speed air to generate propulsive thrust. Unlike conventional jet engines, scramjets achieve efficient thrust by compressing air through a system of shocks. As a result, the reliability of the engine is highly sensitive to the stability of these shock structures. Physically, these shocks are located in an engine component called the isolator. The shock structures are spatially distributed leading to a region of pressure increase, which is termed the pseudoshock. As vehicle operating conditions change, the length of the pseudoshock will change, reflecting changes to inflow conditions and operation of downstream combustor component. The overall objective of this thesis is to understand the complex flow inside these isolators. Of particular focus is the role of molecular processes in the development of the shocks. At high enthalpy conditions, the internal motions of the molecules are moved out of equilibrium due to compression shocks, which affects not only the thermophysical properties of air, but more critically the fuel-air mixing and chemical reactions. While there exists a vast body of literature on scramjet isolators, almost all of these works focus on low enthalpy conditions due to laboratory experimental limitations, or simply rely on equilibrium thermodynamics. In this work, the effect of nonequilibrium on isolator and scramjet combustors at high-altitude high-enthalpy flight conditions was studied using high-fidelity numerical simulations. Detailed models for the description of molecular nonequilibrium, in the form of multi-temperature model was used. Computational chemistry derived reaction rates were used to describe the combustion processes. These studies revealed the following key features: a) nonequilibrium of vibrational states greatly increases pseudoshock length, b) contrary to external hypersonics, nonequilibrium accelerates chemical reactions in the combustor, reducing the distance from fuel injection to flame ignition and stabilization, c) while multi-temperature models are adequate to express such nonequilibrium effects, more detailed state-specific representations clearly demonstrate that molecular populations do not follow the Boltzmann relation even at subsonic but compressible flow conditions. In a related study but using equilibrium thermal conditions, it was shown that the isolator shock structure can develop a resonance to inflow perturbations that can vastly increase the pseudoshock spatial oscillations. These results verify that isolator flow is a complex nonlinear process and clearly demonstrate that the design of scramjets needs to include the effect of thermal nonequilibrium. To begin addressing this process, reduced-order models in the form of a flux-conserved one-dimensional formulation for estimating pseudoshock length was developed for thermal equilibrium conditions.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/143909/1/rfievet_2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143909/2/rfievet_1.pd

Aeronautical enginnering: A cumulative index to a continuing bibliography (supplement 312)

This is a cumulative index to the abstracts contained in NASA SP-7037 (301) through NASA SP-7073 (311) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled by the Center for AeroSpace Information of the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, foreign technology, contract number, report number, and accession number indexes