Design and testing of a heat pipe gas combustion system for the STM4-120 Stirling engine

Evaporators of a novel geometry, designed to have a more compact size yet the same output as larger, conventional heat pipes, have been fabricated and tested. A technique was developed to calculate capillary pressure required inside the heat pipe. Several quarter- and full-scale evaporators were designed and successfully tested. The burner, film-cooled combustion chamber, and preheater were designed and tested separately. A complete heat pipe gas combustion system (HPGC) was tested, showing an efficiency of 89% was measured at 20 kW_th. A film-cooled combustion chamber was tested with flame temperatures of 2200°C and wall temperatures below 1000°C using preheated air for film cooling. Also, a full-scale HPGC was tested at an excess of 95 kW_th, showing efficiency in the range of 85 to 90% under steady-state conditions. Results of transient and startup tests, carried out to evaluate the performance of the heat pipe, all also reported