Positive displacement engine with separate combustion chamber

Claim 1

A low pressure, low combustion temperature engine of the Brayton or Joule type having reduced level of pollutants in its exhaust and having a steady state mode, a braking mode and a peak power mode, the engine comprising: means defining at least one power stage including a positive displacement chamber; a combustion chamber located externally of said displacement chamber to supply a power fluid to said displacement chamber; a reciprocating piston provided in said displacement chamber and driven by said power fluid during power strokes of an operating cycle; air inlet means including a first valve opening into said displacement chamber for supplying air at ambient atmospheric pressure to said displacement chamber and air outlet means including a second valve opening out of said displacement chamber for allowing compressed air to exit said displacement chamber, said air inlet means and said air outlet means operating during a portion of engine operation to provide compressed air for passage via said outlet means to said combustion chamber to form part of the power fluid during power strokes in the steady state mode, said air outlet means supplying air from said displacement chamber during about each fifth stroke of said piston during the normal steady state mode of the engine; and accumulator coupled to said displacement chamber to receive compressed air therefrom via said air outlet means and to supply stored compressed air to said combustion chamber; control means effective during a braking mode of operation to interrupt flow of power fluid from said combustion chamber to said displacement chamber via a third valve and flow of exhaust from said displacement chamber via a fourth valve and to enable said piston to compress air on each compressing stroke and pass compressed air to said accumulator; and means to selectively supply compressed air from said accumulator to said combustion chamber both on starting the engine and during the full power mode of the operating cycle while interrupting flow of air from said displacement chamber to said accumulator.