Propulsion simulation in a magnetic suspension wind tunnel with special reference to force measurement

The primary aim of this research was to demonstrate the feasibility of simulating an engine exhaust flow in a wind tunnel, using a model levitated by a Magnetic Suspension and Balance System (MSBS). The project formed part of a continuing effort to prove the

viability of the MSBS as an aid to wind tunnel testing. It is important that propulsion simulation can be performed in a future commercial MSBS wind tunnel facility. The MSBS eliminates support interference, which often affects the regions of a flight vehicle

also influenced by the engine exhaust. During exhaust simulation in an MSBS there is no physical connection to the model through which exhaust gas can be supplied, and the model must incorporate a gas generator.

Two techniques for gas generation on-board a suspended model are considered in this thesis. A compressed gas thruster is shown to be unsuitable for exhaust simulation at this scale, because the thrust profile produced varies strongly with time and is incompatible with the control and data analysis requirements. The issue of acceptability of thrust profiles is addressed. It is concluded that the Southampton MSBS hardware, rather than the control software, was the limiting factor during this project in deciding what constituted an acceptable thrust profile. Solid propellant rocket thrusters were also investigated, and a rocket motor was developed which allowed a successful demonstration of propulsion simulation testing in an MSBS.

A deficiency in the ability to measure the forces influencing a suspended model was highlighted by the propulsion simulation research. A study showed that the concept of an external balance for measuring the forces produced by the MSBS electromagnets was both under-exploited, and suitable for development with the Southampton facility. This thesis describes the design and production of a three-component balance. The balance was used initially to improve the ability of the control system to generate independent force and moment components on a model, and later in a test series investigating high angle of attack aerodynamics. This was the first such test series performed in an MSBS wind tunnel.

University of Southampton

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