Abstract: An expander for a heat engine, the expander being capable of converting a high pressure gaseous working fluid to useful work, the expander including: •high pressure working fluid supply means; •at least one reciprocating piston reciprocating in a cylinder between top-dead-centre (TDC) and bottom-dead-centre (BDC) with a long dwell time at TDC; •a working fluid inlet valve that opens and closes to introduce, while open, high pressure working fluid from the working fluid supply means into an expansion chamber in the cylinder at or near TDC; •power transfer means that transfers work done on a piston by the working fluid to a form of useful work output; and •an exhaust valve to release expanded working fluid from the expansion chamber to a volume of low pressure working fluid; wherein piston travel is small during transition of the inlet valve from open to closed and from closed to open.

Abstract: A heat engine includes a boiler, an injector for injecting working fluid into the boiler, a retainer for releasing the hydraulic fluid for movement away from a start position once working fluid vapour pressure in the boiler reaches a predetermined level, a returner for returning the hydraulic fluid to its start position following expansion of working fluid vapour in the boiler, resulting in reciprocating hydraulic fluid motion, and an exhaust valve to release expanded working fluid vapour from the boiler. The vapour pressure increase in the boiler causes a change of state from liquid to gas of a least a portion of the injected working fluid, followed by a substantially constant pressure heating of the working fluid, giving rise to a change of state from liquid to gas of substantially all of the remaining injected working fluid.

Abstract: The invention relates to a reciprocating engine and a working fluid inlet system therefore. The engine includes at least one cylinder with a reciprocating piston therein and a variable volume expansion chamber capable of receiving a working fluid via an inlet valve. The inlet system includes a pilot valve having an open condition and a closed condition. In the open condition, the secondary fluid passes therethrough to act on the inlet valve. The system also includes an actuating means for controlling the condition of the pilot valve. The inlet valve is adapted to open in response to the action of the secondary fluid. The engine may also include exhaust means, possibly by porting in the piston and a cylinder wall. The working fluid may be used as the secondary fluid.

Abstract: The invention relates to a reciprocating engine and a working fluid inlet system therefore. The engine includes at least one cylinder with a reciprocating piston therein and a variable volume expansion chamber capable of receiving a working fluid via an inlet valve. The inlet system includes a pilot valve having an open condition and a closed condition. In the open condition, the secondary fluid passes therethrough to act on the inlet valve. The system also includes an actuating means for controlling the condition of the pilot valve. The inlet valve is adapted to open in response to the action of the secondary fluid. The engine may also include exhaust means, possibly by porting in the piston and a cylinder wall. The working fluid may be used as the secondary fluid.

Abstract: A control system for a cogeneration unit, the cogeneration unit including a heat engine and an alternator, driven by the heat engine, which generates AC electricity for an electrical load. The control system includes a parameter sensing means for sensing one or more parameters, and providing a sensed parameter value for each sensed parameter. For each sensed parameter, a comparator means compares the sensed parameter value with a respective desired value and provides an error signal according to the difference between the sensed parameter value and the desired value. One or more controlling means use the one or more of the error signals to provide a plurality of control signals, such that each control signal is able to regulate one or more of the controlling characteristics of the alternator and a temperature of a body heated using energy from the cogeneration unit.

Abstract: A control system for a cogeneration unit, the cogeneration unit including a heat engine and an alternator, driven by the heat engine, which generates AC electricity for an electrical load. The control system includes a parameter sensing means for sensing one or more parameters, and providing a sensed parameter value for each sensed parameter. For each sensed parameter, a comparator means compares the sensed parameter value with a respective desired value and provides an error signal according to the difference between the sensed parameter value and the desired value. One or more controlling means use the one or more of the error signals to provide a plurality of control signals, such that each control signal is able to regulate one or more of the controlling characteristics of the alternator and a temperature of a body heated using energy from the cogeneration unit.