Abstract: A turbocooler includes a multistage turbine wheel for simultaneous and independent interaction with multiple gas streams to reduce the temperature levels of the gas streams. The turbine wheel includes at least two turbine stages designed to discharge the respective gas streams at different temperature levels, wherein the warmer gas stream is interposed between the colder gas stream and a turbocooler load. The warmer gas stream thus provides a thermal barrier isolating the colder gas stream from turbocooler heat sources thereby permitting increased temperature reduction of the colder gas stream for use, for example, in cryocooler applications. The multistage turbine wheel further facilitates bearing lift-off, for example, in a foil bearing machine.

Abstract: An improved free piston power unit includes a pair of power pistons at opposite ends of a common power cylinder, wherein the power pistons are linked for reciprocation in unison in opposite directions. The power pistons carry a respective pair of compressor pistons disposed within compressor cylinders to generate a supply of compressed air or the like upon power piston reciprocation. The power pistons further cooperate with a respective pair of gas-containing bounce cylinders which provide pneumatic reaction forces to return the power pistons through a compresion stroke at the conclusion of a combustion expansion stroke. The bounce cylinders each have a relieved end face to provide an increased minimum bounce cylinder volume thereby limiting the maximum pressure and temperature to which the bounce cylinders are subjected, without requiring increase in the overall envelope size for the power unit.