Gerotor compressor and gerotor expander

An engine comprising: a compressor for compressing ambient air; a combustor for burning said compressed air, said chamber to produce combustion exhaust gas; an expander for receiving said exhaust gases from said combustor and expanding said exhaust gases; and a regenerative brake comprising: a pressure tank, wherein said pressure tank stores said compressed air; at least one first valve coupled to said compressor; expander clutch; and a clutch expander, wherein during braking said clutch expander is disengaged and said clutch compressor is engaged, and wherein said at least one first valve isolates said compressor during engine start or during acceleration, isolates said combustion chamber during braking and isolates said tank during steady state operation.