Abstract: A hybrid turbogenerator and a method of operation are provided to configure a gas turbine engine. In the context of a method, a hybrid turbogenerator including a gas turbine engine coupled to an electric motor-generator alternates between a standby mode and a charging mode. In the standby mode, the method at least partially closes one or more inlet guide vane(s) to limit air flow through a compressor and into a turbine. In the standby mode, the method provides power to both a power bus and the electric motor-generator from an energy storage device. In the charging mode, the method at least partially opens the inlet guide vane(s) to increase air flow through the compressor and into the turbine relative to the standby mode. In the charging mode, the method provides electric power from the electric motor-generator to both the power bus and the energy storage device.

Abstract: The fuel efficiency of an internal combustion reciprocating piston engine may be increased through selective secondary expansion of exhaust gas in the engine cylinders in order to recover exhaust gas energy which is otherwise wasted by cylinder blow-down at the end of the power stroke. Exhaust valve cam switching, intake valve deactivation, multiple exhaust valves, a specialized exhaust manifold arrangement and an exhaust gas diverter valve can be configured to enable a reciprocating engine to selectively operate in efficient eight stroke cycle compound mode when moderate engine power is demanded, then revert to conventional four stroke cycle non-compound mode operation when high engine power is demanded, without stopping the engine.

Abstract: The fuel efficiency of an internal combustion reciprocating piston engine may be increased through selective secondary expansion of exhaust gas in the engine cylinders in order to recover exhaust gas energy which is otherwise wasted by cylinder blow-down at the end of the power stroke. Exhaust valve cam switching, intake valve deactivation, multiple exhaust valves, a specialized exhaust manifold arrangement and an exhaust gas diverter valve can be configured to enable a reciprocating engine to selectively operate in efficient eight stroke cycle compound mode when moderate engine power is demanded, then revert to conventional four stroke cycle non-compound mode operation when high engine power is demanded, without stopping the engine.