Heat engine and method of operation

Abstract

A closed cycle heat engine is provided. The heat engine includes first and second expansion pistons that are fluidly coupled to a heater. The expansion pistons are also fluidly and operably coupled to a compression piston. A regenerator extracts heat from a working fluid flowing from the expansion cylinders to the compression cylinders to preheat the working fluid flowing to the heater. A cooler is arranged in between the regenerator and the compression cylinder to remove additional heat before the working fluid reaches the compression cylinder. The heat engine is arranged such that the working fluid travels unidirectionally within the engine. The heat engine may further include one or more actuated valves for controlling the flow of the working gas. In one embodiment, the pressure of the crankcase is controlled to be at or less than the heat engine minimum pressure.

1 . A closed cycle heat engine comprising:
 a first expansion piston arranged in a first cylinder;   a second expansion piston arranged in a second cylinder and operably coupled to said first expansion piston, wherein said second cylinder is fluidly coupled to said first cylinder;   a compression piston arranged in a third cylinder and operably coupled to said first expansion piston, wherein said third cylinder is fluidly coupled to received a working fluid from said second cylinder and transfer said working fluid to said first cylinder.   
     
     
         2 . The heat engine of  claim 1  further comprising a drive linkage coupled to said first expansion piston, said second expansion piston and said compression piston. 
     
     
         3 . The heat engine of  claim 2  wherein said drive linkage is a cam plate. 
     
     
         4 . The heat engine of  claim 2  wherein said drive linkage is an articulated crankshaft. 
     
     
         5 . The heat engine of  claim 2  further comprising:
 a drive case coupled to said drive linkage, said drive case being operated at a pressure less than or equal to a minimum pressure of said working fluid that occurs in said first cylinder and said second cylinder during operation of said heat engine.   
     
     
         6 . The heat engine of  claim 1  further comprising a regenerator arranged to transfer thermal energy from said working fluid flowing from said second cylinder to said third cylinder to said working fluid flowing from said third cylinder to said first cylinder. 
     
     
         7 . The heat engine of  claim 6  wherein said regenerator is a counter flow heat exchanger. 
     
     
         8 . The heat engine of  claim 6  further comprising:
 a heater thermally coupled between said regenerator and said first cylinder; and,   a cooler thermally coupled between said third cylinder and said regenerator.   
     
     
         9 . The heat engine of  claim 8  further comprising:
 a first valve fluidly coupled between said heater and said first cylinder;   a second valve fluidly coupled between said second cylinder and said regenerator;   a first check valve fluidly coupled to said third cylinder to allow said working fluid to flow into said third cylinder; and   a second check valve fluidly coupled to said third cylinder to allow said working fluid to flow from said third cylinder.   
     
     
         10 . A heat engine having a working fluid comprising:
 a first set of cylinders having a first expansion piston fluidly and operably coupled to a second expansion piston and a first compression piston fluidly and operably coupled to said first expansion piston and said second expansion piston, wherein said first set of cylinders is arranged in a first closed cycle to provide a first unidirectional flow of said working fluid.   
     
     
         11 . The heat engine of  claim 10  further comprising:
 a second set of cylinders operably coupled to said first set of cylinders, said second set of cylinders having a third expansion piston fluidly and operably coupled to a fourth expansion piston and a second compression piston fluidly and operably coupled to said third expansion piston and said fourth expansion piston, wherein said second set of cylinders is arranged in a second closed cycle to provide a second unidirectional flow of said working fluid.   
     
     
         12 . The heat engine of  claim 11  wherein said first set of cylinders and said second set of cylinders are arranged 90 degrees apart. 
     
     
         13 . The heat engine of  claim 12  further comprising a regenerator thermally coupled to said first closed cycle and said second closed cycle. 
     
     
         14 . The heat engine of  claim 13  further comprising a heater coupled to said first closed cycle and said second closed cycle to transfer thermal energy to said working fluid. 
     
     
         15 . The heat engine of  claims 14  further comprising a radiator coupled to said first closed cycle and said second closed cycle to transfer thermal energy from said working fluid. 
     
     
         16 . The heat engine of  claim 15  wherein said regenerator is arranged in a first portion of the first closed cycle between the second expansion piston and the first compression piston, and is arranged in a second portion of the second closed cycle between the fourth expansion piston and the second compression piston. 
     
     
         17 . The heat engine of  claim 11  further comprising a drive case operably coupled to said first set of cylinders and said second set of cylinders, said drive case having an operating pressure less than or equal to a minimum pressure of said working fluid in said first set of cylinders and said second set of cylinders during operation of said heat engine. 
     
     
         18 . A method of operating a closed cycle heat engine comprising:
 heating a working fluid;   expanding said heated working fluid into a first cylinder to move a first expansion piston to a first position;   flowing said heated working fluid into a second cylinder to move a second expansion piston to a second position;   flowing said working fluid from said first cylinder and said second cylinder to a third cylinder;   compressing said working fluid in said third cylinder with a compression piston; and,   flowing said working fluid from said third cylinder to said first cylinder.   
     
     
         19 . The method of  claim 18  further comprising transferring thermal energy from said working fluid flowing from said second cylinder to said third cylinder to said working fluid flowing from said third cylinder to said first cylinder before said step of heating said working fluid. 
     
     
         20 . The method of  claim 19  further comprising cooling said working fluid before said step of compressing said working fluid in said third cylinder. 
     
     
         21 . The method of  claim 20  further comprising dwelling said first expansion piston at said first position during said step of flowing said heated working fluid into said second cylinder. 
     
     
         22 . The method of  claim 21  further comprising the step of dwelling said second expansion piston at said second position during said flowing of said working fluid from said first cylinder to said third cylinder. 
     
     
         23 . The method of  claim 18  further comprising:
 adjusting a drive case to a first pressure less than or equal to a pressure of said working fluid in said first cylinder and said second cylinder when said second expansion piston is in said second position.   
     
     
         24 . A heat engine comprising:
 at least two expansion pistons fluidly coupled to each other, each expansion piston being arranged in an expansion cylinder;   at least one compression piston fluidly coupled to said at least two expansion pistons, each compression piston being arranged in a compression cylinder;   a drive linkage operably coupled to said at least two expansion pistons and said at least one compression piston, said drive linkage arranged in a crankcase, wherein said crankcase is fluidly coupled to said expansion cylinder and said compression cylinder; and,   a pressurized vessel fluidly coupled to said crankcase, wherein said pressurized vessel is arranged to add pressurized gas to said crankcase in response to a change in operation of said heat engine.