Shock Vector Control applied to a Converging-Diverging Nozzle and a Hypersonic Vehicle

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Copyright: Van Pelt, Hilbert
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Abstract
Shock vector control (SVC) is a technique to control airplanes and spaceplanes by means of fluid injection into the nozzle flow. SVC is part of fluidic thrust vectoring, a technique whereby a control force can be generated by means of fluid injection in the engine exhaust. For this thesis the application of shock vector control to a converging-diverging nozzle and a hypersonic vehicle was investigated. The experiments with a converging-diverging nozzle with an injector took place in an experimental facility which houses extruded two-dimensional nozzle profiles of 8 mm thick. The profiles are sealed by two windows on either side of the nozzle for optical access. The nozzle is a linear converging-diverging nozzle with a sonic injector placed at 71% length of the diverging section. On this geometry two-dimensional steady state simulations have been performed, as well as time accurate simulations and a large eddy simulation. It is shown that the injected mass creates a blockage for the incoming flow generating a shock wave. This blockage causes the core flow to separate before the injector, meaning that there is a high pressure region before the injector creating the sideforce. It was demonstrated numerically and experimentally that the sideforce, relative to the axial force, has a linear relationship with the injected mass until the shock wave hits the opposite nozzle wall causing a shockwave boundary layer interaction that is detrimental to the net sideforce. It is shown that this type of nozzle flow can be modelled with analytical relations based on blast wave theory. The established analytical methods were calibrated based on an orifice injector and therefore the calibration constant needed to be changed from 1.2 to 2.36 because of the full width injector. In an orifice injector the cross flow can go around the injected fluid, while in a two-dimensional flow case all the nozzle flow is being turned by the injected fluid, and therefore the calibration constant needs to be increased. It was demonstrated that for the small scale experiment the force establishment time is 0.2 msec, which is faster than most solenoid valves available on the market. Analytically it is shown that the establishment time will increase with the size of the nozzle, but it will remain fast enough to be used as a control system for a full scale rocket or scramjet. The experimental supersonic geometry was modelled with Large eddy simulation (LES) and compared to Reynolds averaged Navier-Stokes (RANS) simulations. It was shown that the flow shows three-dimensional effects at the point where the sidewall meets the injector, but is more iii two-dimensional towards the middle of the nozzle. To test the hypersonic implementation of SVC a scramjet of similar shape to the X-43 was designed with a single slot injector close to the trailing edge of the nozzle. The pressure in the hypersonic environment is orders of magnitude lower than in the supersonic experiment and therefore a large expansion of the Mach disk at the injection point was seen. An increase of sideforce and moment is present with an increase in injection massflow for the experiments and simulations up to the point where the size of the separation zone does not anymore match the size of the Mach disk at high injection pressures. For the current experimental setup it is therefore shown that efficient control can be established with an injection pressure lower than 39 times the static flow pressure.
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Author(s)
Van Pelt, Hilbert
Supervisor(s)
Neely, Andrew James
Young, John
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Publication Year
2018
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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