this rotary engine is made up of three parallel encased rotors : a central male rotor , flanked by a female compression / combustion rotor and a female separation rotor , all three coupled for synchronous rotation . the male rotor has lobes projecting from it , which mesh with complementary cavities in the female rotors during rotation . these cavities have hollows , so that as the lobes mesh with them combustion chambers are formed in the compression / combustion rotor cavities and compression zones are formed the separation rotor cavities . a passage connecting the lobe and combustion chamber provides more opportunity to convert combustion energy into rotational mechanical energy . the separation rotor serves as a pump and separates intake from exhaust gases . passages connecting the compression zone to the combustion chamber , and that to the exhaust port , help purge residual combusted gases from the combustion chamber .