Numerical investigation of aerodynamic effects of distributed propulsion

The concept of distributed propulsion is to integrate the propulsion system with the airframe to exploit synergies of such a configuration. This report describes a CFD study of the aerodynamic effect of distributed propulsion. Firstly, a preliminary design model is established and studied. Several configurations of 2D model of distributed propulsion have been analyzed, using a new BC to model the engine. Finally a 3D model of an aircraft equipped with a distributed system is studie

Quasi-0D-model mapping of reflected shock tunnel operating conditions

Reflected shock tunnels have been widely used for ground testing of hypersonic airbreathing engines. These facilities are able to replicate the total enthalpy and pressures experienced along hypersonic flight trajectories. Designing the relevant operating conditions is complex, and extensive guidance about operation condition design in reflected shock tunnels is scarce. To facilitate the operation of a reflected shock tunnel, it may be advantageous to develop a database of attainable conditions and the operation parameters required to achieve them. For this, a model to calculate global thermodynamic states and shock speeds also accounting for piston location and tube length (quasi-0D-model) is proposed. This model uses the NASA Chemical Equilibrium with Applications code to solve real gas and high-temperature effects. A number of conditions are calculated to produce maps of operating conditions. As test cases, the reflected shock tunnel under development at Tokai University, and T4 at the University of Queensland are used. Maps obtained sweeping rupture pressure or compression ratio, and initial test gas pressure for different driver compositions are presented. This methodology can be adapted to similar facilities. Moreover, observation of the presented maps provides a quick reference of the influence of each parameter when modifying existing conditions or fine-tuning tunnel operation

Multidimensional effects and self- absorption on spectroscopic observations of Saturn entry radiation

Shock visualization and direct radiation measurements were conducted in an expansion tube facility at the University of Queensland to investigate the multidimensional effects and self-absorption on spectroscopic observations of Saturn entry radiation. Cylindrical test models with varying aspect ratios were used to generate shock layers with varying optical depths for laboratory observations. High speed imaging was employed to visualise the shock, and emission spectroscopy was used for radiation measurements of Balmer series. The shock standoff distance was found to be affected by the aspect ratio. Significant self-absorption in H-alpha was shown by the data in normalised 2D zone, while the H-beta self-absorption becomes stronger as the optical depth along the line-of-sight increases. The results show the aspect ratio of at least 3 is required to avoid significant edge effect for this Saturn entry condition. Increasing the aspect ratio from 3 to 4 will not affect the H-alpha radiation measurements much, while the self-absorption in H-beta will decrease when the optical depth along the line-of-sight increases. These results emphasis the multidimensional effects and self-absorption on the radiation measurements, and highlight the selection of measured transitions for Saturn entry condition

Performance considerations for expansion tube operation with a shock-heated secondary driver

A shock-heated secondary driver is a modification typically applied to an expansion tube which involves placing a volume of helium between the primary diaphragm and the test gas. This modification is normally used to either increase the driven shock strength through the test gas for high-enthalpy conditions, or to prevent transmission of primary driver flow disturbances to the test gas for low-enthalpy conditions. In comparison to the basic expansion tube, a secondary driver provides an additional configuration parameter, adds mechanical and operational complexity, and its effect on downstream flow processes is not trivial. This paper reports on a study examining operation of a shock-heated secondary driver across the entire operating envelope of a free-piston-driven expansion tube, using air as the test gas. For high-enthalpy conditions it is confirmed that the secondary driver can provide a performance increase, and it is further shown how this device can be used to fine tune the flow condition even when the free-piston driver configuration is held constant. For low-enthalpy flow conditions, wave processes through the driven tube are too closely coupled, and the secondary driver no longer significantly influences the magnitude of the final test gas flow properties. It is found that these secondary driver operating characteristics depend principally on the initial density ratio between the secondary driver helium gas and the downstream test gas

The X3R Free-Piston Reflected Shock Tunnel: Australia's New Large-Scale, Long-Duration Hypersonic Testing Capability

X3R is a new, large-scale free-piston driven reflected shock tunnel designed and operated at the University of Queensland, Australia. The facility is a derivative of the X3 super-orbital expansion tube, which uses a combination of new and pre-existing hardware. It is capable of generating 600 mm diameter Mach 7 test flows at 25 kPa and 50 kPa dynamic pressure for durations of approximately 12.5 ms. Previously, hypersonic testing in Australia was limited in both scale and duration, due to the size of the local facilities capable of experimentation in this regime. This paper presents the new facility and summarizes its current operational capabilities. This includes a description of the facility geometry, and details of the two currently available operating conditions. These conditions were specifically designed to overcome the drawbacks of the tunnel’s relatively short free-piston driver, and use a high helium fraction driver gas to produce a long duration but low compression ratio driver response