Abstract: K. Engine (KE) is rotary internal combustion engine, combination Reciprocating Engine (RE) and Gas Turbine (GT) comprising coaxially separate piston rotary compressor and turbine having housings with annular channels, outside combustion chambers (CH) unified with rotary valve mechanisms, staggered partitions dividing the annular channels for separate cylinders or freely passing the pistons; control means governing the partitions allow operational adjustment displacement volume KE without a brake effect; separate CHs secure ideal combustion in constant volume, unrestricted analog of advance of an ignition and forced ventilation; combined Otto- Brighton cycle and simple design provide high efficiency and reliability, great fuel economy, small sound and pollution; optimal work diapason KE is wider of both GT and RE; weight and size KE led to RE of the same displacement volume is 10 times less but more power and torque.