Rotary positive displacement machine

A rotary internal combustion engine comprising

• a casing with intersecting rotor compartments,
• rotors able to rotate in said compartments and turning about axles which are supported by the casing, each said rotor being in the shape of a disc with abutments or lobes defined between alternating tips and roots with respective outer and inner radii,
• gearing on the axles controlling said rotors to rotate without contact of respective interleaving lobes in such a way that interior surfaces of said casing and opposing tips and roots of first alternating adjacent pairs of said rotors define a transfer volume between separated compression and expansion regions on respective sides of a plane through axes of said rotors of each said first adjacent pair,
• apertures in the casing to permit output and input of working fluid or gases from and to said compression and expansion regions under the action of the other adjacent interacting rotor pairs, each said first alternating adjacent pair of interleaving rotors providing a periodic transfer of a respective volume of the fluid or gas between the respective compression region via the transfer volume to the respective expansion region, and
• means for igniting the working fluid or gas in said transfer volume between the respective compression and expansion regions,
• wherein the peripheral length of each said tip is shorter than the respective peripheral length of each opposing root, said transfer volume is defined to extend between respective opposing sides of said abutments or lobes of the respective first interleaving rotor pair when said interleaving lobes are equally spaced from said plane of the respective first rotor pair, respective opposing tips and roots of each said first rotor pair have a point of closest contact in said plane thereof, and each said transfer volume contains a part of the working fluid or gas from the respective compression region that is sectioned off as a result of the respective interleaving rotors, which part expands into the respective expansion region, as the rotor rotates.