A set of inner and outer brush seals capable of bidirectionally restricting flows in a wave rotor has been successfully fabricated and tested. Unconventional techniques, such as pulsed combustion and wave rotor topping cycles, have been suggested. However, the achievement of high efficiency through these means will depend on the ability to control leakage losses by means of adequate sealing.
Pulsed combustion can result in combustion with a pressure gain.
A wave rotor topping cycle, which can also be thought of as pressure gain combustion, appears to generate higher pressure ratios than pulsed combustion currently does, and so is more attractive. Fuel intercooling and wave rotors could be used in conjunction in the same engine to enhance performance. In the wave rotor machine both compression and expansion occur, and in some cases chemical reactions take place. Advantages cited for the wave rotor include enhanced efficiency, rotor material temperatures lower than the peak gas temperatures, lower speed rotation with reduced stress, simple robust construction, and rapid transient response. Sealing can be a major factor in the wave rotor, and the seal is dynamic.