Heat recuperative engine with improved recuperator

In an engine of the type having

• (1) compression means for compressing a fluid working medium,
• (2) means for heating the compressed fluid working medium, and
• (3) work producing means for inducting the compressed heated fluid working medium and producing work by expansion of the working medium,
• the improvement of a rotary positive displacement mechanism utilizing the expanded working medium exhausted from the work producing means to heat compressed working medium prior to its induction into the work producing means, the rotary positive displacement mechanism comprising
• (a) a housing having a first chamber with an inlet port for admitting compressed fluid working medium and an outlet port,
• (b) a pair of external spur rotors disposed for rotation in the first chamber, the external spurs being meshed and the rotors extending across the chamber to form a blockage between the inlet and outlet ports,
• (c) each of the spur rotors having its external spurs fitting closely with a segment of the chamber wall having embedded heat pipes forming an array around an appreciable extent of the chamber wall, the spaces between adjacent external spurs on a spur rotor providing constant volume enclosures as the external spurs sweep around the closely fitting chamber wall segment,
• (d) the housing having a second chamber adjacent to the first chamber, the second chamber having an inlet port for admitting expanded working medium exhausted from the work producing means and having an outlet port,
• (e) a second pair of external spur rotors disposed for rotation in the second chamber, the external spurs of the second pair being meshed and the rotors extending across the second chamber to form a blockage between the inlet and outlet ports,
• (f) means for driving the first and second pairs of rotors to cause the first pair of rotors to rotate in directions counter to those of the corresponding rotors of the second pair,
• (g) each of the rotors of the second pair having its external spurs fitting closely with a segment of the chamber wall having embedded in it extensions of the heat pipes embedded in the corresponding wall segment of the first chamber, the spaces between adjacent external spurs on a rotor providing constant volume enclosures as the external spurs sweep around the closely fitting wall segment whereby the heat pipes effect recuperative heat exchange between compressed working medium confined in the constant volume enclosures of the rotors in the first chamber and the expanded working medium confined in the constant volume enclosures of the rotors in the second chamber.