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Electrical power generation from standing shock waves

University of British Columbia

Standing shock waves in a supersonic flow field produce density gradients across which an electrical potential is established. If electrodes are mounted upstream and downstream of the standing shock, an electrical current can be extracted. The electrical power output by such a system (called a bow shock generator) has been measured. To produce the supersonic flow an overdriven detonation shock tube, capable of producing Mach 12 shocks in 5 Torr argon, was constructed and used as a short duration supersonic wind tunnel. The open circuit voltage of a single bow shock generator with a 2 cm electrode separation was measured to be 0.95 V, and the maximum power output to 53 mW. By reducing the electrode separation to 1 cm the maximum power output was increased to 90 mW, while the open circuit voltage remained unchanged. It was found that when two bow shock generators are mounted side by side in the flow a parallel connection of their outputs produced a small increase in current. However no increase in output voltage was observed when the generators were connected in series. It was also found that when an oblique shock and its reflection from the wall were connected together in series, the output voltage was less than that of the oblique shock alone. However this was likely due to a short circuit path between the electrodes through the boundary layer. Some of the measurements were inconclusive due to an insufficiently long test time. A preliminary analysis was done on a system in which a set of bow shock generators is used as a topping system for a conventional electrical generation system. It was shown that the bow shock generators must be operated at very low Mach numbers if they are to be efficient in this application.

Text

2010-03-22

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http://hdl.handle.net/2429/22262

Physics

University of British Columbia

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