Abstract:
A thermodynamic system for powering a reciprocating device includes a refrigerant passing in a closed loop between a refrigerant compressor, a condenser, an expansion valve, and an evaporator. The system includes a heat source for heating the refrigerant, and an engine for receiving the heated refrigerant. The engine includes a housing, a shaft axially movable within the housing, a piston attached to the shaft, a shifter for reversing piston direction, and porting for passing the refrigerant into and out of the engine housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority from U.S. Provisional Application No. 61/547,105 filed on Oct. 14, 2011, the disclosure of which is incorporated herein by reference for all purposes. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to heat powered reciprocating piston engine capable of powering a compressor, a pump, an alternator, or any device using reciprocating power. The piston engine is particularly suitable for use at sites where electrical power is unavailable and at sites where waste heat is available. 
     BACKGROUND OF THE INVENTION 
     Rankin cycle heat driven engines such as automobile engines have been available for years. Successful hydrocarbon combustion engines have reached efficiencies upward of 40% have been critical in the industrial development over the past century. The heat driven engine proposes to utilize a portion of this waste heat to drive all auxiliary equipment such as air condition, generator, and hydraulic systems on mobile and stationary engines. Although hybrid power systems are improving car mileage, the removal of energy consuming auxiliary systems will become critical to greater efficiency. 
     The power from gas turbine systems increases with inlet air temperature drop. Because gas turbines provide a significant percent of the world&#39;s electrical power, effort has been underway for decades to improve their power output efficiency. By utilizing turbine exhaust heat to power the heat engine which can drive a reciprocating refrigeration system, inlet air can be chilled, thereby increasing generator output. 
     Because of environmental effects changes in fluorocarbon compounds have affected air conditioning efficiencies, efforts have been made to improve the operation and efficiency of the compressor, condenser, evaporator, and components of these systems. Energy costs are increasing and are anticipated to continue to increase. Use of “free” energy, such as solar or wind, are increasingly attractive. Providing a solar heat driven reciprocating piston engine to power a refrigeration compressor to augment an existing air conditioning system can greatly reduce the electrical energy requirements. 
     U.S. Pat. No. 5,275,014 discloses a heat pump system which employs a diaphragm attached to the face of the piston. Diaphragms of this type do not reliably work in heat pump systems over time due to the repeated flexing of the diaphragms and the ability of the refrigerants to escape from the system through a very small crack. U.S. Pat. No. 4,765,144 discloses a solar powered pumping engine suitable for use in oil field pumping. Other patents of interest include U.S. Pat. Nos. 3,839,863, 3,960,322, 4,068,476, 4,103,493, 4,178,989, 4,459,814, 4,571,952, 4,720,978, 4,739,620, 7,340,899, and 7,426,836. 
     U.S. Pat. No. 7,536,861 discloses a solar heat engine system, and U.S. Pat. No. 5,246,350 discloses a solar powered pumping system. U.S. Pat. No. 7,877,999 discloses an environmental heating and cooling system, and U.S. Pat. No. 7,845,345 discloses a solar-powered system for providing utilities. A solar energy powered generator is disclosed in U.S. Pat. No. 7,779,635, and a stirling cycle engine is disclosed in U.S. Pat. No. 7,726,129. U.S. Pat. No. 7,621,129 discloses another version of a geothermal power system. 
     The disadvantages of the prior art are overcome by the present invention, an improved heat powered reciprocating engine is hereinafter disclosed. 
     SUMMARY OF THE INVENTION 
     In one embodiment, a thermodynamic system is provided for powering a reciprocating device. A thermodynamic system includes a refrigerant passing in a closed loop between a compressor, a condenser, an expansion valve, and an evaporator. A thermodynamic system further comprises a heat source for heating the refrigerant, and an engine for receiving the heated refrigerant. The engine including a housing, a shaft axially movable within the housing, a piston attached to the shaft, a shifter for reversing piston direction, and ports for passing refrigerant into and out of the engine housing. 
     These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of the heat powered reciprocating piston engine powering a gas turbine system. Inlet air to the gas turbine inlet air chilling system is chilled by the piston engine to increase generator output. 
         FIG. 2  is a diagram of the heat powered reciprocating piston engine powering the compressor of a refrigerant system. 
         FIG. 3  is a diagram of a reciprocating piston engine utilizing waste heat from an automobile to power the compressor or other device on the vehicle. 
         FIG. 4  is a detailed cross-sectional view of the reciprocating piston engine according to the present invention. 
         FIGS. 5-7  illustrate the sequential operation and porting of the reciprocating piston engine and shifter. 
         FIG. 8  is another embodiment at a heat powered reciprocating piston engine. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Gas turbine electrical power generation systems provide an excellent application for the heat engine. Turbine power output increases with turbine inlet air temperature. A reduction in inlet temperature of approximately 20 degrees F. produces an increase of 5% in the turbine power output. Because gas turbines provide a significant share of the worlds&#39; electrical power, improving their power output efficiency is highly desirable. By utilizing turbine exhaust heat to power the proposed heat engine which drives a reciprocating refrigeration system, an inlet air chiller results in increased generator output. 
     Referring to  FIG. 1 , the cycle begins in the “boiler”  21 , which is a tube bundle which lines the inside of the turbine exhaust stack. The boiler is utilized to boil a refrigerant. As heat energy is added, the refrigerant elevates in temperature and pressure. The gas is collected in the gas surge tank  22  where it is fed into the inlet of the heat engine  24  through a temperature actuated control valve  23 . The engine  24  drives a refrigeration compressor  25  which compresses the cooling refrigerant to high pressure. The discharge of the heat engine goes to the condenser  32  where it is liquefied and is pumped to the liquid surge tank  29  through pump  30 . The liquid surge tank  29  supplies high pressure liquid refrigerant to the boiler  21  which is controlled by pressure control valve  31  where the cycle repeats. The work added to compress the gas in compressor  25  elevates its temperature which is removed in a condenser  26  and the compressed gas is liquefied. The discharge from the condenser  26  feeds the evaporator  28  through expansion valve  27  that chills the inlet turbine air. The discharge of the evaporator  28  returns to the compressor  25  to repeat the cycle. Condenser  32  condenses the gas to a liquid. Temperature control  33  supplies a control signal to control valve  23 . 
     Referring now to  FIG. 2 , the reciprocating piston engine of the present invention may also be used to increase the efficiency of an air conditioning system. More particularly, a parabolic solar collector  36  boils the refrigerant which powers the reciprocating piston engine  38 , which in turn powers a piston compressor  39  and a fluid pump  40 . Exhaust from the engine passes through a condenser  41  where the exhaust gases liquefy. The DC powered condenser fan  42  may be powered by a solar panel. Refrigerant is passed through the pump and returned to the solar collector  36  and the cycle is repeated. 
     In  FIG. 2 , the solar collector  36  boils the refrigerant, which powers the reciprocating piston engine  38 , which drives the piston compressor  39  and the fluid pump  40 . Liquid refrigerant is passed through the pump  40  and returned to the solar collector where the cycle is repeated. Gas surge tank  22 , expansion valve  27 , evaporator  28 , liquid surge tank  29 , liquid control valve  31 , and control valve  23  each serve a similar purpose to the same components in  FIG. 1 . The refrigerant compressor may be connected in parallel to an existing air conditioning system to provide supplemental cooling. The system of the present invention may provide a significant increase to the primary system cooling capacity, which should be as much as 50% when the temperature is hot and the sun is shining. The system of the present invention may be skid mounted requiring only a connection to an existing refrigerant system. 
     As explained more fully below, the engine includes a one-piece cylinder with movable parts internal of the cylinder. The engine is fluidly connected to the solar connector on one side and the condenser on the other by conventional piping. When the heat sun is adequate to boil the refrigerant, the engine will start. More sunshine results in greater cooling and enhanced efficiency for the refrigerant system. By utilizing the engine powered by the sun&#39;s heat, the powering of a rotary air conditioning compressor may be eliminated or reduced. 
     The system will have supplemental power, either from an electrically-driven compressor operating in parallel with the heat-driven compressor or from a gas-fired boiler operating in parallel with the solar boiler. The unit may be used as an air conditioner in summer and a heater in winter. There need not be a moving shaft penetrating the pressure shell; the engine compressor pump (ECP) may be hermetically sealed to prevent leakage of refrigerant. 
     The environmental impact this air conditioner would avoid over time, compared to a standard unit, far exceeds the impact of a complete refrigerant leak. The ECP&#39;s ability to retain its refrigerant or use a less harmful form will be important. Condenser and evaporator temperatures are set by environment and by cooling needs, while boiler temperature must be set by a balance between solar boiler efficiency and engine efficiency. 
     The ECP has a double-acting engine driving a double-acting compressor and a single-acting pump. Work is transmitted by the piston rod with no rotary motion. Compressor and pump flows are controlled by check valves, while engine flows are controlled by an internal shifter. The shifter valve driven  18  by control logic using data from a rod position sensor. Since engine cylinder pressure decreases as compressor cylinder pressure increases, the design must make use of piston inertia to complete the compression process. 
     Referring now to  FIG. 3 , a waste heat driven engine  54  utilizes waste heat from the vehicle radiator and exhaust systems to power auxiliary equipment, such as air conditioning, generator, and hydraulic systems on a mobile or a stationary engine. Boiled fluorocarbon gas will drive a reciprocating cylinder. The exit gas is cooled to a liquid in a condenser, its pressure elevated in a piston pump driven by the engine, and returned to the boiler where it repeats for another cycle. As hybrid power systems are improving car mileage numbers the removal of energy hungry auxiliary systems will become critical. 
     The cycle begins by heating a refrigerant within an exhaust heat exchanger or boiler  51  utilizing the engine exhaust gas. The boiler  51  boils a refrigerant. As heat energy is added, the refrigerant elevates in temperature and pressure. The gas is collected in the gas surge tank  22  where it is fed into the inlet of the heat engine  54  through a temperature actuated control valve  23 . The engine  54  drives a refrigeration compressor  55  which compresses the cooling refrigerant to high pressure. The discharge of the heat engine goes to the condenser  32  where it is liquefied and is pumped to the liquid surge tank  29  through pump  50 . The liquid surge tank  29  supplies high pressure liquid refrigerant to the boiler  51  which is controlled through pressure control valve  31 , where the cycle repeats. The work added to compress the gas in compressor  55  elevates its temperature which is removed in condenser  56  where the compressed gas is liquefied. The discharge of the condenser  56  feeds the evaporator  28  through expansion valve  27  that chills the automobile air. The discharge of the evaporator  28  returns to the compressor  55  to repeat the cycle. The reciprocating engine can power a hydraulic system for power brakes and steering, or may power an alternator to power the vehicle electrical systems. 
       FIG. 4  illustrates in greater detail a suitable engine  60  according to the present invention. The piston  61  is attached to a shaft  62 , with the piston and shaft positioned within an outer housing  63 . The engine shifter assembly  67  may have various configurations, as discussed below. The end plates  65  and  66 , and the engine shifter  67  connecting the plates, move as an assembly within the housing  63 . Gas pressure is applied to the shifter chambers  75  and  76  through slider valve  68  (shown in  FIG. 5 ) by inlet  69  passing through the slider valve  68  (shown in  FIG. 5 ) and into ports  70  and  73 . Depending on the slider valve  68  (shown in  FIG. 5 ) position, the shifter assembly  67  directs working gas into the cylinder areas through ports  71  and  77  pushing the piston  61  to the right or left where it is held by the pressurized gas. Gas is exhausted from the cylinder areas where it returns back to the condenser through ports  74  and  78 . The piston pushes the shifter assembly  67  discussed subsequently at the end of each stroke which reverses the supply and exhaust ports to reverse the piston direction. The shifter allows the entire engine to be sealed, thereby reducing the possibility of refrigerant leakage. 
     One end of the shaft may be utilized to pump the refrigerant which is liquefied in the condenser back to the solar collector. The pump may be required because the solar collector is above the engine operating pressure. Liquid flow may be directed by check valves, and a pressure controller is utilized to control the engine and gas flow and ensure sufficient gas for operation. The compressor has a piston smaller in diameter than the piston engine to provide an increase in pressure necessary for the cooling cycle. Check valves provide for one way flow in the cooling system. 
       FIG. 5-7  illustrate the sequence of operation of the heat engine. The engine start position is shown in  FIG. 5 . The piston  61  and shaft  62  assemblies are in the retracted left position. The engine shifter  67  and the slider valve  68  are also in the left position. Operating gas pressure holds the engine shifter  67  in the left position through the slider valve  68  and ports  69  and  70 . When operation of the engine is desired, gas pressure is introduced into the heat engine outer housing  63  through port  71 . The piston  61  and shaft  62  move to the right as shown in  FIG. 6 . The slider valve  68  remains unmoved as the shaft  62  passes through it. Slightly before the piston  61  reaches an wall  65  of engine shifter  67 , the enlarged portion  72  of the shaft  62  strikes the slider valve  68 . As the enlarged portion  72  of the shaft  62  continues to travel right, it shifts the slider valve  68  to the right as shown in  FIG. 7 . When the slider valve  68  shifts, it redirects port  69  shutting off gas flow to the right side of the shifter  75  while opening the right side to the exhaust line to exhaust port  80 . At the same time, the shifted slider valve  68  closes the left side shifter vent  81  and opens the gas flow into the left side  76  of the shifter assembly  67 , causing the shifter assembly  67  to shift to the right. This realigns the shifter assembly  67 , isolating ports  71  and  77 , and opening ports  78  and  74  passing gas pressure to the right side of the piston  61 . The piston  61  travels left reversing the sequence until the pump piston  79  shifts the slider valve  68  to the left reversing all slider valve ports. This cycle repeats until gas pressure is shut off. 
       FIG. 8  illustrates controlling the shifter  67  using two control rods  82  and  83 . Control rod  82  controls the shifter end pressure, and control rod  83  controls the shifter end exhaust. 
     The engine start position is shown in  FIG. 8 . The piston  61  and shaft  62  assemblies are in the retracted left position. The engine shifter assembly  67  and both control rods  82  and  83  are also in the left position. Operating gas pressure flows through control rod  82 , which is undercut at  70  into the right shifter void  87 , thereby holding the shifter in the left position. Control rod  83  is also in the left position allowing the undercut area  88  to vent gas pressure on the left shifter  67  end through the pipe  85 . 
     When operation of the engine is desired, gas pressure is introduced into the heat engine outer cylinder  63  through port  71 . The piston  61  and shaft  62  move to the right. As the shaft  62  continues to travel right, the control rods  82  and  83  also move right until pressure ports  73  and  89  are reached. Port  89  exhausts the pressure in the shifter right void  87  and pressure is introduced into the shifter left void (between the left plate  66  and the piston  61 ) through pressure port  73 . Shifter  67  shifts to the right, shutting off the left gas supply  71  and opening the right side gas supply  77 . Simultaneously, the shifter closes the right side gas exhaust opening  74  and opens the lift side gas exhaust opening  78 . Piston  61  and shaft  62  then return to the start position and the cycle repeats. 
     Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.