Beta Free Piston Stirling Engine In Free Casing Configuration Having Power Output Controlled By Controlling Casing Amplitude Of Reciprocation

Abstract

The power output of a free piston Stirling engine mounted in a free casing configuration is controlled by having a spring drivingly linking the displacer to the casing and controllably varying the amplitude of reciprocation of the casing. A variable casing reciprocation restraint is linked to the casing for applying a variable restraining force to the casing. The restraining force is increased for decreasing the displacer amplitude of reciprocation and thereby decreasing the power output from the Stirling engine and the restraining force is decreased for increasing the displacer amplitude of reciprocation and thereby increasing the power output from the Stirling engine.

1 . A method for controllably varying the power output of a free piston Stirling engine contained within a casing and mounted in a free casing configuration permitting reciprocating movement of the casing with respect to a reference ground, the engine including a displacer and a piston that reciprocate at an operating frequency, the displacer having a spring drivingly linking the displacer to the casing, the method comprising:
 controllably varying the amplitude of reciprocation of the casing with respect to the reference ground by applying and varying a restraining force applied to the casing, the restraining force being increased for decreasing the displacer amplitude of reciprocation and thereby decreasing the power output from the Stirling engine and the restraining force being decreased for increasing the displacer amplitude of reciprocation and thereby increasing the power output from the Stirling engine.   
     
     
         2 . A method according to  claim 1  wherein drive power is applied to drive the displacer by the spring from the casing and that drive power is greater than the sum of any other displacer drive power applied to the displacer. 
     
     
         3 . A method according to  claim 2  wherein the spring drives the displacer with at least 70% of the displacer drive power driving the displacer in reciprocation. 
     
     
         4 . A method according to  claim 3  wherein the spring drives the displacer with at least 99% of the displacer drive power driving the displacer in reciprocation. 
     
     
         5 . A method according to  claim 1  and further comprising applying the restraining force from the ground to the casing by braking the reciprocation of the casing and increasing the restraining force by increasing the braking. 
     
     
         6 . A method according to  claim 1  wherein the restraining force is applied by drivingly coupling a mass to the casing. 
     
     
         7 . A method according to  claim 1  and further comprising increasing the restraining force as a load driven by the engine approaches closer to a selected operating limit so that the power output from the engine is an increasing function of the difference between the operating limit and the current load. 
     
     
         8 . A method according to  claim 7  wherein the restraining force is applied by a self controlling load connected between the casing and the reference ground, the self controlling load increasing the force required to drive the load as the load approaches closer to a selected operating limit. 
     
     
         9 . A method according to  claim 8  wherein the self controlling load is a fluid pump that is pumping fluid into a vessel and the fluid pressure increases as the vessel fills with the fluid. 
     
     
         10 . A method according to  claim 1  and further comprising applying a drive force on the casing in phase synchronism with the reciprocation of the casing as driven by the reciprocation of the displacer and piston for increasing the amplitude of reciprocation of the casing and thereby increase the power output from the Stirling engine. 
     
     
         11 . An improved free piston Stirling engine contained within a casing and mounted in a free casing configuration permitting reciprocating movement of the casing with respect to a reference ground, the engine including a displacer and a piston that reciprocate at an operating frequency, the improvement comprising:
 (a) a spring drivingly linking the casing to the displacer and, during operation, applying a drive force to the displacer from the reciprocation of the casing for driving the displacer in reciprocation, wherein drive power applied to the displacer from the casing is greater than the sum of any other drive power applied to the displacer; and   (b) a power output control that is a variable reciprocation restraint drivingly linked to the casing, the reciprocation restraint being capable of applying an increased restraining force on the casing for decreasing the amplitude of reciprocation of the casing and of applying a decreased restraining force on the casing for permitting the amplitude of reciprocation of the casing to increase.   
     
     
         12 . An improved free piston Stirling engine according to  claim 11  wherein the spring is the only displacer drive for driving the displacer in reciprocation. 
     
     
         13 . An improved free piston Stirling engine according to  claim 11  wherein the variable reciprocation restraint is connected between the casing and the reference ground. 
     
     
         14 . An improved free piston Stirling engine according to  claim 13  wherein the variable reciprocation restraint is a brake. 
     
     
         15 . An improved free piston Stirling engine according to  claim 13  wherein the variable reciprocation restraint is a self controlling load driven by the casing, the self controlling load having the operating characteristic of increasing the force required to drive the load as the load approaches closer to a selected operating limit. 
     
     
         16 . An improved free piston Stirling engine according to  claim 15  wherein the self controlling load is a fluid pump connected for pumping fluid into a vessel and the fluid pressure increases as the vessel fills with the fluid. 
     
     
         17 . An improved free piston Stirling engine according to  claim 11  wherein the spring drives the displacer with at least 70% of the displacer drive power driving the displacer in reciprocation. 
     
     
         18 . An improved free piston Stirling engine according to  claim 17  wherein the spring drives the displacer with at least 99% of the displacer drive power driving the displacer in reciprocation. 
     
     
         19 . An improved free piston Stirling engine according to  claim 11  wherein the variable reciprocation restraint is a variable mass that is drivingly linked to the casing. 
     
     
         20 . An improved free piston Stirling engine according to  claim 11  wherein the spring is a gas spring within the displacer, the gas spring having a connecting rod extending from a gas spring piston within the displacer to a perforate support formed in a compression space of the free piston Stirling engine and fixed to an interior wall of the engine. 
     
     
         21 . An improved free piston Stirling engine according to  claim 11  wherein the displacer has a connecting rod extending from the displacer, through the piston into a back space of the engine and the spring is a gas spring formed adjacent the back space. 
     
     
         22 . An improved free piston Stirling engine according to  claim 11  wherein the displacer has a diameter that is larger than the diameter of the piston.