Stirling engine thermal system improvements

In a thermal cycle engine of the type having a piston undergoing reciprocating linear motion within an expansion cylinder, the expansion cylinder having a cylindrical wall and containing a working fluid heated by conduction through a heater head of heat from an external thermal source, the improvement comprising:

• a heat exchanger for transferring thermal energy across the heater head from a heated external fluid to the working fluid, the heat exchanger comprising a set of heat transfer pins, each heat transfer pin characterized by a height and diameter, where the height and diameter of a subset of the set of heat transfer pins, up to the entirety thereof, varies along a direction of a flow path of the external fluid, the heat transfer pins extending from the heater head into the external fluid.

In a thermal cycle engine of the type having a piston undergoing reciprocating linear motion within an expansion cylinder, the expansion cylinder having a cylindrical wall and containing a working fluid heated by conduction through a heater head of heat from an external thermal source, the improvement comprising:

• a heat exchanger for transferring thermal energy across the heater head from a heated external fluid to the working fluid, the heat exchanger comprising a set of heat transfer pins having a set of characteristics, at least one characteristic varying in a direction of a flow path of the external fluid;
• and
• a pin backer for guiding the heated external fluid in the flow path characterized by a direction past the set of heat transfer pins.

In a thermal cycle engine of the type having a piston undergoing reciprocating linear motion within an expansion cylinder, the expansion cylinder having a cylindrical wall and containing a working fluid heated by conduction through a heater head of heat from an external thermal source, the improvement comprising:

• a heat exchanger for transferring thermal energy across the heater head from a heated external fluid to the working fluid, the heat exchanger comprising a set of heat transfer pins;
• and
• a pin backer for guiding the heated external fluid in a flow path characterized by a direction past the set of heat transfer pins, the pin backer having a dimension perpendicular to the heater head that decreases in the direction of the flow path.

In a thermal cycle engine of the type having a piston undergoing reciprocating linear motion within an expansion cylinder, the expansion cylinder having a cylindrical wall and containing a working fluid heated by conduction, through a heater head, of heat from an exhaust gas of an external combustor having a fuel supply, the improvement comprising:

• a. a thermal sensor for measuring a temperature of the heater head at a point of maximum temperature of the heater head.

In a thermal cycle engine of the type having a piston undergoing reciprocating linear motion within an expansion cylinder, the expansion cylinder having a cylindrical wall and containing a working fluid heated by conduction, through a heater head, of heat from an exhaust gas of an external combustor having a fuel supply, the improvement comprising:

• a. a secondary ring burner for supplying additional fuel to cause additional combustion of the exhaust gas.