Abstract: Adiabatic positive displacement gas cycle machinery is designed with explicit control of the heat flow between the gas and the walls. The control is achieved by maintaining near-laminar flow and a small wall area to volume ratio. The most stable near-laminar flow in a cylinder is an axial vortex because of symmetry, and hence the induction port design should establish an axial vortex and a low velocity. Induction and exhaust port designs to achieve this flow are applied to a vane pump, an adiabatic air compressor, a diesel engine, and two and four stroke Otto cycle engines. The gain in thermal efficiency for these designs can be significant, up to a factor of 2, since the largest inefficiency in nearly all positive displacement machinery is imperfect control of heat flow.

Abstract: The design of a cryogenic regenerator for an isothermal Stirling cycle is based upon separately minimizing the losses due to the static heat mass regenerator material and the thermodynamic losses of the gas transferred through the regenerator. This leads to a sequence of regenerator sections each designed for a given temperature region (temperature difference/temperature=1/2) where the gas flows in a constant width channel in contact with a smooth channel wall. Two alternate designs are given, one with the channel walls of a thin stainless steel backed up by bands of lead and the second using a special alloy of pure lead and roughly 1% of a heavy soft metal such as bismuth or cesium. The composite banded regenerator leads to an overall efficiency relative to Carnot of 50% at 4.degree. K. and 15 Hz and the special lead alloy regenerator leads to 25% efficiency at 4.degree. K. and 30 Hz.

Abstract: Positive displacement isothermal gas cycle machinery is designed with explicit control of the heat flow between the gas, the walls of the chamber and a thermal reservoir externally of the chamber. The control is achieved by providing a large chamber wall area to chamber volume ratio through the use of bellows-like walls having a configuration that ensures during each stroke numerous heat exchanges between the working gas and the bellows-like walls. The machinery includes Stirling cycle heat pumps and motors and isothermal compressors. Significant gains in thermal efficiency, up to a factor of 2, are attainable because the largest inefficiency in all isothermal machinery is imperfect control of heat flow. A regenerator for the isothermal machinery minimizes cycle losses due to gas transfer friction, gas thermal conduction, dead volume, regenerator heat mass, regenerator heat mass thermal skin depth, and regenerator mass thermal conductivity in the gas flow direction.