Rotary compressor and expander, and rotary engine using the same

A rotary engine for use with compressible fluids, the engine comprising:

• a first rotation element mounted to rotate about a first axis;
• a casing having a surface enclosing at least a part of the first rotation element, an elongate cavity of varying cross sectional area being defined between a surface of the first rotation element and the casing surface;
• and
• a plurality of second rotation elements mounted to rotate about respective different second axes, each second rotation element being mounted to project through a slot in the casing surface and to cooperate with the first rotation element surface so as to divide the cavity into adjacent working portions,
• wherein each second rotation element comprises a plurality of projecting portions having respective different radii about the second axis, the different radii causing the projecting portions to project into the cavity by respective different amounts, so that the volumes of the working portions vary as the first and second rotation elements rotate,
• wherein, during a cycle of an engine operation, fluid in a working portion undergoes compression, combustion and expansion as a closed volume, the closed volume being defined during the compression, combustion and expansion by an adjacent pair of second rotation elements.