Abstract: A heater head assembly for a multi-cylinder heat engine the stirling engine, such as a multi-cylinder Stirling engine, having a plurality of regenerators and cylinders. Each regenerator has a regenerator manifold and each cylinder has a cylinder manifold. First identical cast heater tubes connect the regenerator manifold to first heater tube openings in a heater head manifold. Second identical cast heater tubes connect second heater tube openings in the heater head manifold to the cylinder manifold. The first and second heater tubes are parallel with respect to each other and form a pair of partial concentric staggered arrays. The heater tubes are rotationally asymmetric, having fin sections with less surface area upstream than downstream and thicknesses which decrease radially away from the central passageways of said heater tubes.

Abstract: Low friction material particularly adapted for use at high temperatures in the regenerator portion of gas turbine engines, the material comprising a work surface layer on a substrate, the work surface layer prior to a break-in period comprising an iron oxide (wustite--FeO, magnetite--Fe.sub.3 O.sub.4, or hematite--Fe.sub.2 O.sub.3) matrix containing an interspersed trapping material in the interstices thereof, the trapping material comprising an inorganic compound such as a salt or oxide; and subsequent to the break-in period, the work surface layer acquires a substantially continuous film of hematite--Fe.sub.2 O.sub.3 iron oxide in which the hexagonal Fe.sub.2 O.sub.3 crystals or cells provide a highly oriented structure. Transfer of the oriented film to the mating surface occurs during run-in.

Abstract: Diffusion-alloying of aluminum into copper brazed joints and structures, particularly for turbine engine regenerator cores.