Abstract: A resonant free-piston Stirling engine having a new and improved start-up and control method and system. A displacer linear electrodynamic machine is provided having an armature secured to and movable with the displacer and having a stator supported by the Stirling engine housing in juxtaposition to the armature. A control excitation circuit is provided for electrically exciting the displacer linear electrodynamic machine with electrical excitation signals having substantially the same frequency as the desired frequency of operation of the Stirling engine.

Abstract: A stability control system for a free piston Stirling engine/alternator power unit whose engine power is an exponential function on the engine piston stroke and whose alternator power demand is also an exponential function of the piston stroke, and wherein the engine exponent is normally equal to or greater than the alternator exponent, includes a connection through a rectifier between the alternator output terminals and the alternator field windings. This increases the alternator exponent above the engine exponent to make the system stable. The large time constant of the field winding inductance, which would tend to slow the response time during transients, can be avoided by adding a suitable resistance in series with the field winding.

Abstract: A hydraulic drive system operating from the periodic pressure wave produced by a Stirling engine along a first axis thereof and effecting transfer of power from the Stirling engine to a load apparatus therefor and wherein the movable, or working member of the load apparatus is reciprocatingly driven along an axis substantially at right angles to the first axis to achieve an arrangement of a Stirling engine and load apparatus assembly which is much shorter and the components of the load apparatus more readily accessible.

Abstract: A heater head for a multi-cylinder double acting hot gas engine in which each cylinder is surrounded by an annular regenerator unit, and in which the tops of each cylinder and its surrounding regenerator are interconnected by a multiplicity of heater tubes. A manifold for the heater tubes has a centrally disposed duct connected to the top of the cylinder and surrounded by a wider duct connecting the other ends of the heater tubes with the regenerator unit.

Abstract: A free piston Stirling engine inertial cancellation system includes a displacer reciprocating in a hermetic vessel enclosing a working space to circulate working gas through a heater, regenerator, and cooler to create a pressure wave in the working space. A power piston, mechanically unconnected to the displacer, is reciprocally driven by the pressure wave to produce a power output stroke in one direction and a working gas compression stroke in the other direction. The displacer and the power piston form substantially a first mass in the working space. A second mass, outside the working space and preferably including an alternator plunger, is mounted in the vessel and is coupled to the first mass momentum exchange relationship.

Abstract: In a Stirling cycle engine having a plurality of working gas charges separated by pistons reciprocating in cylinders, the total gas content is minimized and the mean pressure equalization among the serial cylinders is improved by using two piston rings axially spaced at least as much as the piston stroke and by providing a duct in the cylinder wall opening in the space between the two piston rings and leading to a source of minimum or maximum working gas pressure.

Abstract: A power control is disclosed for a free piston Stirling engine having a hermetically sealed vessel enclosing a working space in which oscillates a displacer for circulating working gas through a heater, a regenerator and a cooler for creating a pressure wave in the working gas which acts against a power piston for a producing power stroke. The displacer includes a post mounted in a well which forms a gas spring and cooperates with the working gas pressure wave to maintain the displacer in axial reciprocating motion. The post includes a tapered portion which reciprocates opposite a proximity probe to produce a unique signal for each axial position of the displacer to provide stroke, phase and amplitude information regarding the displacer motion. A gas spring volume control is provided, controlled by the displacer sensor, for adjusting the gas spring stiffness to control the amplitude and phase of the displacer required to produce the power to meet the engine load requirements.

Abstract: A free piston Stirling engine has a hermetic vessel containing a displacer piston and a power piston coupled to each other and to the vessel by gas springs. An additional mass is coupled to the vessel by a gas spring which is tuned to the operating frequency of the engine geometrically. The vibration absorber is effective at all engine frequencies because the absorber gas spring follows the engine working gas mean pressure and changes the absorber natural frequency as the engine frequency changes.

Abstract: A power control method and apparatus for a Stirling engine including a valved duct connected to the junction of the regenerator and the cooler and running to a bypass chamber connected between the heater and the cylinder. An oscillating zone of demarcation between the hot and cold portions of the working gas is established in the bypass chamber, and the engine pistons and cylinders can run cold.

Abstract: A mechanical device for effecting a phase change between the expansion and compression volumes of a double-acting Stirling engine uses helical elements which produce opposite rotation of a pair of crankpins when a control rod is moved, so the phase between two pairs of pistons is changed by +.psi. and the phase between the other two pairs of pistons is changed by -.psi.. The phase can change beyond .psi.=90.degree. at which regenerative braking and then reversal of engine rotation occurs.

Abstract: A motion conversion device for converting between the reciprocating motion of the pistons in a Stirling engine and the rotating motion of its output shaft, and for changing the stroke and phase of the pistons, includes a lever pivoted at one end and having a cam follower at the other end. The piston rod engages the lever intermediate its ends and the cam follower engages a cam keyed to the output shaft. The lever pivot can be moved to change the length of the moment arm defined between the cam follower and the piston rod the change the piston stroke and force exerted on the cam, and the levers can be moved in opposite directions to change the phase between pistons.

Abstract: A two-stage harmonic reciprocating Stirling engine has a primary heater and a pair of regenerators with an intermediate heat exchanger disposed in the fluid flow between the two regenerators. High temperature heat above 5000.degree. F. is supplied to the heater head of the engine while lower temperature, otherwise wasted, heat between 500.degree. F. and 1500.degree. is supplied to the intermediate heat exchanger. The lower temperature heat can be from exhaust gases of the primary burner, or can be waste heat from another process for use in a cogeneration installation.

Abstract: A gas bearing for the axially reciprocating displacer and power piston members in a free piston Stirling engine includes a bearing sleeve having a pair of interconnected annular pressure plenums formed by ribs on the outer surface of the sleeve which form a seal with the inner walls of a cylinder in which the sleeve is seated. The outer side of the raised ribs provide a second set of interconnecting drain plenums. A source of a high pressure gas, pressurized internally by the engine itself, is connected to the pressure plenum which communicates with the axially reciprocating members through a multitude of narrow orifices. The bearing gas is drained into the second or drained plenum through a large number of larger sized orifices.

Abstract: A free-piston Stirling engine includes a hermetically sealed vessel enclosing a working space within which reciprocates a displacer. The displacer is mounted at its cold end on mounting means including a first portion, preferably a post, which reciprocates in a second portion, preferably a sleeve, fixed to the vessel. The relatively reciprocating mounting means includes a gas spring. The mounting means also reduces the effective area exposed to a pressure wave of the displacer cold end relative to the displacer hot end so that the thermodynamic system provides power by virtue of the differential areas of the displacer ends. The periodic pressure wave together with the gas spring maintain the displacer in oscillation.

Abstract: A phase and stroke control apparatus for the pistons of a Stirling engine includes a ring on the end of each piston rod in which a pair of eccentrics is arranged in series, torque transmitting relationship. The outer eccentric is rotatably mounted in the ring and is rotated by the orbiting ring; the inner eccentric is mounted on an output shaft. The two eccentrics are mounted for rotation together within the ring during normal operation. A device is provided for rotating one eccentric with respect to another to change the effective eccentricity of the pair of eccentrics. A separately controlled phase adjustment is provided to null the phase change introduced by the change in the orientation of the outer eccentric, and also to enable the phase of the pistons to be changed independently of the stroke change.

Abstract: A free piston Stirling engine includes a hermetically sealed vessel enclosing a working space which is filled with a working gas such as helium. A displacer is mounted in the working space on a suspension apparatus for axial reciprocation to displace working gas back and forth sequentially through a heater, a regenerator, and a cooler to create a cyclic pressure wave which drives a power piston. The displacer is connected to a mounting flange fixed to the vessel by a bellows which permits the displacer to move axially. A diaphragm is connected to the mounting flange and seals an oil cavity whose sides are defined by the bellows. The top of the oil cavity is formed by a transverse wall in the displacer, in which is formed a cylinder which receives a stationary piston mounted on a spider in the oil cavity and fastened to the mounting flange.

Abstract: A diaphragm suspension system for a free piston Stirling engine includes a transverse wall across the cold end of the displacer. An upper diaphragm is attached to the displacer shell above the transverse wall, and a support diaphragm is attached at its center to a partition fixed to the engine vessel, and is attached at its peripheral edge to the lower end of the displacer. A lower oil cavity is defined between the transverse wall and the support diaphragm, and an upper oil cavity is defined between the upper diaphragm and the transverse wall. A cylinder is formed in the transverse wall communicating between the oil cavities, and a piston is disposed in the cylinder and is fixed to the partition. When the displacer moves, the piston remains stationary and compensates for the oil displacement caused by the support diaphragm flexing into and out of the oil cavity, so the support diaphragm experiences only or primarily displacement induced stress rather than pressure induced stress.

Abstract: A free piston Stirling engine having a hermetically sealed vessel enclosing a working space which can be charged with a working gas under pressure. A displacer, mounted in the working space at the cold end by a spring diaphragm member, to circulate the working gas through a heater, a regenerator, and a cooler to create a pressure wave in the working gas which acts against a power piston to produce output power. The spring diaphragm member provides an effective decrease in the area of the cold end of the displacer which causes the thermodynamic system to provide motive power for maintaining the oscillation of the displacer, supports and centers the displacer in the working space, and functions as a spring to return the displacer towards its center position when it is displaced toward the cold or hot end.

Abstract: A reciprocating-to-rotating motion conversion and power control device for a Stirling engine includes a hub mounted on an offset portion of the output shaft for rotation relative to the shaft and for sliding motion therealong which causes the hub to tilt relative to the axis of rotation of the shaft. This changes the angle of inclination of the hub relative to the shaft axis and changes the axial stroke of a set of arms connected to the hub and nutating therewith. A hydraulic actuating mechanism is connected to the hub for moving its axial position along the shaft. A balancing wheel is linked to the hub and changes its angle of inclination as the angle of inclination of the hub changes to maintain the mechanism in perfect balance throughout its range of motion.

Abstract: A free piston Stirling engine having a free displacer mounted in a sealed vessel and suspended on a diaphragm. A rigid wall on the displacer forms, with the diaphragm, a closed oil cavity. A moving wall such as a piston or bellows in the rigid wall accommodates volmetric changes in the cavity when the displacer oscillates in the engine working space to control pressure induced stresses in the diaphragm.