Self-pressurizing Stirling engine
View Patent ↗A solar thermal powered aircraft powered by heat energy from the sun. A heat engine, such as a Stirling engine, is carried by the aircraft body for producing power for a propulsion mechanism, such as a propeller. The heat engine has a thermal battery in thermal contact with it so that heat is supplied from the thermal battery. A solar concentrator, such as reflective parabolic trough, is movably connected to an optically transparent section of the aircraft body for receiving and concentrating solar energy from within the aircraft. Concentrated solar energy is collected by a heat collection and transport conduit, and heat transported to the thermal battery. A solar tracker includes a heliostat for determining optimal alignment with the sun, and a drive motor actuating the solar concentrator into optimal alignment with the sun based on a determination by the heliostat.
1. An improved Stirling engine of a type having a crankcase with opposing hot and cold heat exchanging ends, a piston capable of reciprocating within said crankcase between the hot and cold heat exchanging ends, a crankshaft coupled to said piston and extending out from said crankcase so that reciprocation of said piston rotates said crankshaft, and a journal surrounding said crankshaft, the improvement comprising:
a working fluid within an hermetically sealed crankcase;
a crankcase pressure relief valve for controlling the crankcase pressure and the power output of said Stirling engine;
a closed reservoir for receiving working fluid released from said crankcase pressure relief valve; and
at least one helical groove on a surface of one of said crankshaft and said journal and bounded by a surface of the other one of said crankshaft and said journal, said helical groove(s) communicating between an inner crankcase volume and said closed reservoir so that the relative motion between the rotating crankshaft and said journal pumps the working fluid into said
crankcase to self-pressurize the same, whereby the working fluid released from said crankcase is recycled back into said crankcase.
2. The improvement of claim 1 ,
wherein the working fluid is helium.
3. The improvement of claim 1 ,
wherein the working fluid is hydrogen.
4. The improvement of claim 3 , further comprising:
a hydrogen permeable cap capping the hot end of the Stirling engine; and
a lithium-hydride based thermal storage medium in contact with said hydrogen permeable cap and the hot side of said Stirling engine;
wherein the slow loss of hydrogen from the lithium-hydride is balanced by a slow gain from the Stirling engine hydrogen working fluid through said hydrogen permeable cap, whereby the hydrogen containment of the thermal battery is extended.