Abstract: An exhaust energy extraction system for a multi-cylinder engine, comprising n axial flow turbine arranged to convert time-spaced exhaust pressure pulses into turbine rotor rotation. Output flow from the axial flow turbine is directed through a diffuser that converts velocity pressure to static pressure; a second radial flow turbine is operated by the steady state flow produced by the diffuser. Any tendency of the diffuser to exert an adverse back pressure on the axial flow turbine is counteracted by a pressure-responsive vent valve that establishes a ceiling on the diffuser pressure.

Abstract: Greater overall power is obtained from an internal combustion engine utilizing a power recovery turbine operated by the exhaust gases from the engine cylinders by dimensioning the stacks connecting the exhaust valve flow areas to the turbine such that each stack has a cross sectional flow area less than the cross sectional flow area of the exhaust valve when fully opened. While there results a slight increase in frictional losses in the stack and pumping losses to the piston, such losses are more than made up by the substantial decreases in throttling losses across the exhaust valve flow area during the valve opening process.