Abstract: A circuit is provided for providing a drive signal. The circuit comprises a live input and a neutral input, an output for providing a drive signal, a master logic gate. The first output is connected to the master logic gate output. A dc signal is connected to the input of the master logic gate so that the output of the master logic gate changes when the state of the input changes. A shunt is connected to the live input and is capable of being switched into and out of the circuit in response to the live input voltage changing from positive to negative with respect to the neutral input voltage and vice versa. The shunt is also arranged to provide a short circuit for the dc signal to bypass the input of the master logic gate.

Abstract: A linear-free piston Stirling machine comprising a displacer and a power piston. A rod is attached at one end to the displacer, extends through the power piston and is mounted to the casing at its opposite end via a spring. A resilient stopper at the opposite end is arranged to contact the engine casing if the displacement of the displacer exceeds a predetermined limit.

Abstract: A Stirling engine (1) to which an annular burner (2) is attached and is sealed to the engine by a flexible annular sealing member (5). An annular coolant channel (4) in the form of an annular coolant channel member (24) with a U-shaped cross-section attached to a mounting bracket (3) cools the seal (5). The channel member (24) has an upwardly extending annular flange (29) to shield the interface between the burner (2) and mounting bracket (3). An annular lip (33) extends from a lower region of the coolant channel (24) and the top of the sealing member (5) is fitted around this lip. The sealing member (5) is fitted in place after the coolant channel member (24) has been mounted to the bracket (3).

Abstract: Apparatus and method are provided, for connecting prime mover driven alternator to circuit that has an existing alternating current. Alternator is connected to circuit when minimum current flows to or from alternator. The actual current is measured by controller following connection and the value of this current is used to determine the optimal connection conditions when alternator is next connected. Alternator is disconnected by controller by running down prime mover, monitoring the current and stalling prime mover when the current flow is at a minimum.

Abstract: A circuit is provided for providing a drive signal. The circuit comprises a live input and a neutral input, an output for providing a drive signal, a master logic gate. The first output is connected to the master logic gate output. A dc signal is connected to the input of the master logic gate so that the output of the master logic gate changes when the state of the input changes. A shunt is connected to the live input and is capable of being switched into and out of the circuit in response to the live input voltage changing from positive to negative with respect to the neutral input voltage and vice versa. The shunt is also arranged to provide a short circuit for the dc signal to bypass the input of the master logic gate.

Abstract: A linear free piston Stirling machine having an overstroke prevention mechanism for the power piston. A resilient member is fixed to the casing which contacts the power piston 4 when its displacement exceeds a predetermined level.

Abstract: An annular burner assembly having an annular burner mesh. An annular gas/air supply duct supplies a combustible gas/air mixture to the burner mesh in a substantially axial direction. A flow modifier is provided in the vicinity of the burner and has a plurality of fins each extending in a substantially radial plane to define a plurality of passages arranged circumferentially around the supply duct to substantially laminarise the gas/air mixture. The fins provide a thermal link from the burner to a location radially away from the burner. The burner assembly is particularly suited to a Stirling engine.

Abstract: A switching regulator and method of regulating an ac input signal to provide an ac output signal, receiving the ac input signal, generating a reference signal, detecting the points when the ac input signal is zero and synchronising the reference signal to these points, performing a subtraction between the reference and ac input signals to obtain an error signal, dividing the error signal by the reference signal to obtain a fractional error, and producing a regulated ac output signal by modulating the ac input signal to correct for the fractional error. The switching regulator uses a modulating transistor and clamping diode for each half-cycle of the input signal.

Abstract: Apparatus and method are provided, for connecting prime mover driven alternator to circuit that has an existing alternating current. Alternator is connected to circuit when minimum current flows to or from alternator. The actual current is measured by controller following connection and the value of this current is used to determine the optimal connection conditions when alternator is next connected. Alternator is disconnected by controller by running down prime mover, monitoring the current and stalling prime mover when the current flow is at a minimum.

Abstract: A method of assembling the head of a Stirling machine. Two sets of fins are fixed within the head casing. At least one regenerator element is passed through a central opening in the fins and is located in place between the two sets of fins. The regenerator elements are made from compacted wire and decompress in situ.

Abstract: A linear free piston Stirling machine having a displacer piston mounted on first and second planar springs. The first spring has a stiffness which increases with increasing spring displacement. The second has a stiffness which is less variable with spring displacement to provide a combined stiffness which rapidly increases once the displacer piston displacement exceeds a fixed limit. Each of the springs has a plurality of spiral spring portions and a stress relieving hole beyond the outer edge of the spiral spring portions.

Abstract: A magnetic assembly for a linear electromechanical machine, the assembly comprising an annular support centered on an axis of reciprocation of the machine. A magnet assembly is attached to the annular support. The magnet assembly comprises at least one annular part which is substantially magnetic. The annular part has at least one non-conductive portion in a substantially radial plane and extending at least half of the way through the wall of the annulus.

Abstract: A Stirling engine includes a reciprocating piston which drives an alternator to provide an electrical output. The current signal is measured by a current monitor and a fast Fourier Transform value is produced. The FFT of the current signal has been found to be directly related to the stability of operation of the Stirling engine. As harmonic peaks in the FFT increase, this indicates that the stroke length of the piston is approaching or exceeding a safe maximum. Correction action, such as a reduction in heat to the Stirling engine, can be taken in consequence. A variety of stroke length detectors are also disclosed, for use in combination with, or separately from, the FFT analysis of the current signal. Optical and mechanical switches and analogue sensors are disclosed, along with an accelerometer mounted upon the casing of the Stirling engine.

Abstract: A heating arrangement for heating a fluid, the arrangement comprising an elongate housing having a main axis. An inner chamber (21) for a first fluid surrounds the axis. A plurality of axially extending fins (22) project into the inner chamber. An exhaust gas inlet which receives exhaust gas, for example, from a Stirling engine, is provided at one end of the inner chamber. A supplementary burner (20) at the opposite end of the chamber is arranged to fire radially outwardly on to the fins. An outer chamber (30) for a second fluid surrounds the inner chamber.

Abstract: A domestic combined heat and power (dchp) unit includes a Stirling engine 1 to provide heat for a domestic dwelling along with a source of electrical power. Under normal operation, the dchp is supplied with power from the national grid. When there is an interruption in the mains power from the grid, the dchp switches into a grid independent mode wherein power is generated by the dchp and is supplied to a controller 26 and to a water pump so as to maintain integrity of heat supply to the dwelling; the remaining power after that is supplied to selected domestic electrically powered equipment such as lights or television sets. The invention also discloses methods for black start of the dchp during a mains power loss, and also modification of the operating voltage on start up of electrical equipment during a power loss, to prevent the Stirling engine stalling.

Abstract: The present invention provides a connector arrangement operative to connect a prime mover driven alternator to an alternating current circuit with an existing alternating current. For example, the connector arrangement may be used to connect an alternator driven by a Stirling engine to an alternating current mains electricity supply. The connector arrangement includes a circuit with an adjustable resonant frequency, adjustable between a first resonant frequency tuned to an initial operating frequency of the prime mover and a second resonant frequency detuned to the initial operating frequency. This adjustable resonant frequency is beneficial as it allows operation to be tailored to the exact operating conditions of the prime mover that is likely to have its own resonant frequency that may vary according to its operating condition.

Abstract: A splitter valve comprising an outer sleeve and an inner sleeve both having orifices. The relative position of these elements determines the split of the flow. The orifices are configured so that the relative split between the two streams has a linear relationship with the relative position of the inner element and outer sleeve. A perforate plate is provided across at least one outlet to laminarise the flow.

Abstract: A linear free piston Sirling machine having an overstroke prevention mechanism for the power piston. A resilient member is fixed to the casing which contacts the power piston 4 when its displacement exceeds a predetermined level.

Abstract: Apparatus and method are provided, for connecting prime mover driven alternator to circuit that has an existing alternating current. Alternator is connected to circuit when minimum current flows to or from alternator. The actual current is measured by controller following connection and the value of this current is used to determine the optimal connection conditions when alternator is next connected. Alternator is disconnected by controller by running down prime mover, monitoring the current and stalling prime mover when the current flow is at a minimum.