Abstract:
An apparatus and method is disclosed wherein mechanical power is returned to a prime mover producing waste heat. The apparatus includes a working fluid configured to receive thermal energy from the waste heat, a collector to hold the working fluid, an evaporator fluidly coupled to the working fluid collector for transferring the waste heat to the working fluid to change the working fluid to vaporized working fluid, a feed pump to cause the working fluid to flow between the working fluid collector and the evaporator, an expander fluidly coupled to the evaporator to receive the heated working fluid to create rotational mechanical power, and a condenser to cool the expanded working fluid. The expander is mechanically associated with the prime mover directly or via a clutch.

Description:
RELATED APPLICATIONS 
     This application is a Continuation of U.S. patent application Ser. No. 12/653,718 filed on Dec. 16, 2009 and entitled “Power Compounder”, which is a Continuation-in-Part application of U.S. patent application Ser. No. 11/656,309, now U.S. Pat. No. 7,637,108, filed on Jan. 19, 2007 and entitled “Power Compounder”, and which claims priority from U.S. Provisional Patent Application No. 60/760,633, entitled “Power Compounder” filed on Jan. 19, 2006. The instant application claims priority from and incorporates herein by reference in their entireties all three of the applications enumerated above. 
    
    
     BACKGROUND 
     The conversion of fuels into electricity has long been the focus of engineers. The supply of the fuel to a generation site, as well as the reliability and cost of the supply, is factored into the engineering decision process. 
     The thrust of waste heat recovery technology is to make use of thermal energy normally discarded from a primary power conversion process. In many prior art devices, the discarded thermal energy (i.e., waste heat) is harnessed to drive additional thermo-fluid processes that can yield additional energy (i.e., electricity). 
     Referring to prior art  FIG. 1 , the prior art waste heat recovery system directs a supply of waste heat measured at temperatures between 300° F. to 800° F. from a heat source to an evaporator (see numeral  1 ). The waste heat is transferred to a working fluid in the evaporator. The working fluid is evaporated; changes from a liquid to a vapor, in the evaporator and is expanded through a turbine (see numeral  2 ). The expansion of the working fluid through the turbine drives the turbine. The turbine, in turn, drives an electric generator coupled to the turbine. The generator produces electrical power. The working fluid flows to a condenser and changes phase from vapor to a liquid (see numeral  3 ). The liquid working fluid is then pumped back to the evaporator and begins the cycle again (see numeral  4 ). The above described system employs a closed-loop Organic Rankine Cycle to produce electricity from a thermal energy source, such as waste heat. This example illustrates that the prior art waste heat recovery systems were utilized to produce electricity. 
     Using the above concept of a reverse refrigeration cycle, either a Rankine Cycle or Organic Rankine Cycle (ORC), the waste heat of an engine can be converted to produce a more efficient engine; not electricity. However, the above example relies on turbines to operate the generator. Turbines operate at a greater rotational speed than conventional engines and require extensive, complex machinery in order to try and capture the thermal energy for reuse as mechanical energy. 
     What is needed in the art is a Rankine Cycle or an Organic Rankine Cycle system to convert waste heat from an engine into useful power for the engine that is simple, reliable and cost effective. 
     SUMMARY 
     The following presents a simplified summary of the present disclosure in order to provide a basic understanding of some aspects of the present disclosure. This summary is not an extensive overview of the present disclosure. It is not intended to identify key or critical elements of the present disclosure or to delineate the scope of the present disclosure. Its sole purpose is to present some concepts of the present disclosure in a simplified form as a prelude to the more detailed description that is presented herein. 
     A power compounder is disclosed. The power compounder comprises a working fluid configured to receive thermal energy from waste heat of a prime mover, a working fluid collector, an evaporator configured to transfer waste heat to a working fluid producing a phase change to vapor (or gas) in the working fluid, a double screw expander configured to receive the working fluid for creating rotational mechanical energy, and a condenser configured to produce another phase change in the working fluid to liquid. The double screw expander transfers the rotational mechanical energy via a shaft to the prime mover. 
     The disclosure is also directed toward a power compounder system. The power compounder system comprises a prime mover producing waste heat and a power compounder coupled to the prime mover. The power compounder comprises a working fluid configured to receive thermal energy from the waste heat from the prime mover; a working fluid collector configured to hold the working fluid as a liquid working fluid; an evaporator fluidly coupled to the working fluid collector, such that the evaporator is configured to transfer the waste heat to the working fluid to change the working fluid from a liquid working fluid to a vapor working fluid; a double screw expander fluidly coupled to the evaporator, such that the expander is configured to receive the vapor working fluid to create rotational mechanical energy from expansion of the vapor working fluid through the double screw expander, the double screw expander transfers the rotational mechanical energy via a shaft to the prime mover; and a condenser fluidly coupled to the double screw expander, such that the condenser is configured to receive the vapor working fluid and change the vapor working fluid to the liquid working fluid, the condenser is fluidly coupled to the working fluid collector. 
     The disclosure is also directed toward a method of using a power compounder system. The method comprises directing waste heat produced in a prime mover to a power compounder; transferring thermal energy from the waste heat to a liquid working fluid; transforming the liquid working fluid to a vapor working fluid in an evaporator; directing the vapor working fluid through a double screw expander fluidly coupled to the evaporator; creating rotational mechanical energy in the double screw expander when the vapor working fluid flows through the double screw expander; transferring the rotational mechanical energy via a shaft of the double screw expander to the prime mover; and directing the vapor working fluid to a condenser for transforming to the liquid working fluid, the condenser is fluidly coupled to the expander. 
     A power compounder system is provided and includes a prime mover producing waste heat and a power compounder coupled to the prime mover. The power compounder includes a working fluid configured to receive thermal energy from the waste heat from the prime′ mover, a working fluid collector configured to hold the working fluid as a liquid working fluid, an evaporator fluidly coupled to the working fluid collector, the evaporator configured to transfer the waste heat to the working fluid to change the working fluid from the liquid working fluid to a vapor working fluid, a feed pump configured to cause the working fluid to flow between the working fluid collector and the evaporator and a double screw expander fluidly coupled to the evaporator, wherein the expander is configured to receive the vapor working fluid to create rotational mechanical energy from expansion of the vapor working fluid through the double screw expander, such that the double screw expander transfers the rotational mechanical energy via a shaft to the prime mover. The double screw expander is further coupled to the prime mover via at least one of a mechanical clutch, an electrical clutch and a Sprag clutch. The power compounder further includes a condenser fluidly coupled to the double screw expander, wherein the condenser is configured to receive the vapor working fluid and change the vapor working fluid to the liquid working fluid, wherein the condenser is fluidly coupled to the working fluid collector. 
     A method of using a power compounder system is provided and includes directing waste heat produced in a prime mover to a power compounder, transferring thermal energy from the waste heat to a liquid working fluid, transforming the liquid working fluid to a vapor working fluid in an evaporator, directing the vapor working fluid through a double screw expander fluidly coupled to the evaporator, wherein the double screw expander is further coupled to the prime mover via at least one of a mechanical clutch, an electrical clutch and a Sprag clutch, creating rotational mechanical energy in the double screw expander when the vapor working fluid flows through the double screw expander, transferring the rotational mechanical energy via a shaft of the double screw expander to the prime mover and directing the vapor working fluid to a condenser for transforming to the liquid working fluid, wherein the condenser is fluidly coupled to the expander. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Referring now to the figures, wherein like elements are numbered alike: 
         FIG. 1  is a diagram of a prior art waste heat recovery system; 
         FIG. 2  is a schematic of an exemplary power compounder system; 
         FIG. 3  is a side view of an exemplary power compounder system; 
         FIG. 4  is another side view of the exemplary power compounder system of  FIG. 3 ; 
         FIG. 5  is a side view of another exemplary power compounder system; 
         FIG. 6  is a bottom view of a double screw expander; 
         FIG. 7  is a front view of a double screw expander; 
         FIG. 8  is a front view of a profile of the rotors of a double screw expander; 
         FIG. 9  is a front view of another profile of the rotors of a double screw expander; 
         FIG. 10  is a side isometric view illustrating a clutch device being employed between the expander and a prime mover; and 
         FIG. 11  is a side isometric view of illustrating a clutch device being employed between a pump and the expander. 
     
    
    
     DETAILED DESCRIPTION 
     Persons of ordinary skill in the art will realize that the following disclosure is illustrative only and not in any way limiting. Other embodiments of the disclosure will readily suggest themselves to such skilled persons having the benefit of this disclosure. 
     The present disclosure is a power compounder system that converts waste heat thermal energy from a source (or prime mover or engine) into rotational mechanical energy. Power compounding is the process of directly attaching an expander (or a compressor configured to act as an expander) to a shaft of a prime mover. For example, in a typical combustion engine, the thermal energy is normally discarded via jacket water heat through a radiator, engine exhaust out a stack, oil cooler, or any other conventional means. In the present disclosure, the normally discarded waste heat is recovered from the engine and harnessed. The waste heat is harnessed using either a Rankine Cycle or an Organic Rankine Cycle (ORC) power compounder having an expander (i.e., double or twin screw). The waste heat is harnessed by conversion to rotational mechanical energy which is redirected back to the engine, increasing the engine&#39;s net power output by as much as about 10% additional horsepower. This additional horsepower is achieved without using additional fuel or producing additional emissions. 
       FIG. 2  is a schematic of an embodiment of the present disclosure.  FIGS. 3, 4, and 5  illustrate exemplary embodiments of the power compounder  10  system coupled to a prime mover (e.g., an engine)  12 . The power compounder  10  has an expander  14  that is coupled to the prime mover  12  via a shaft  16 . In one embodiment illustrated in  FIGS. 3 and 4 , elements (i.e., the evaporator  18 , the condenser  20 , and the like) of the power compounder  10  are contained within a system cabinet  22 . 
     Although a combustion engine is illustrated in  FIGS. 3, 4, and 5  as the prime mover  12 , any machine that utilizes mechanical energy can be utilized, including but not limited to, pumps, external combustion engines, internal combustion engines, turbines, compressors, and the like. 
     Referring again to  FIG. 2 , as the prime mover  12  is operated, waste heat (illustrated as arrow  24 ) is discarded from the prime mover  12 . The waste heat  24  can be transferred via any known means compatible to the prime mover, including but not limited to, engine lube oil, coolant, exhaust, water jacket, and the like. Waste heat is a term that generally covers various sources of thermal energy in a transfer medium at temperatures as low as about 140° F. (such as a fluid, a hot gas, hot oil, hot water, steam, and the like). In another embodiment disclosed on page 45 of Provisional U.S. Patent Application No. 60/760,633, previously cited as priority for the instant application and incorporated herein by reference in its entirety, the waste heat supply has a minimum temperature of 180° F. The waste heat can be supplied from a wide variety of sources including but not limited to: internal combustion engines, gas turbines, gas flares in landfills, industrial manufacturing processes that continuously produce thermal energy, incinerators, boilers, water heaters, geothermal wells, methane, bio-gas sources, and the like. 
     In the preferred embodiment, waste heat  24  is directed from the prime mover  12  to the power compounder  10  via an outlet  26 . The thermal energy  28  is transferred to a working fluid (illustrated as arrow  30 ) in the evaporator  18 . The waste heat  24  medium is returned to the prime mover  12  via inlet  27 . The working fluid  30  can be any known working fluid, including but not limited to, water, refrigerants, light hydrocarbons, and the like. The working fluid must be compatible with the power compounder system. Examples of refrigerants include but are not limited to, R-124, R-134a, R-245fa, and the like. The working fluid  30  is transformed in an evaporator  18  located in the system cabinet  22 . The evaporator  18  transfers the thermal energy  28  from the waste heat  24  from the prime mover  12  to the working fluid  30 . 
     The evaporator  18  exchanges the thermal energy  28  from the waste heat  24  to the working fluid  30 . The evaporator  18  can be any variety of heat exchangers and fashioned to operate with the waste heat, including, but not limited to, plate, tube and shell, tube and fin, and the like. For example, if the waste heat is in the form of an internal combustion engine exhaust, the heat exchanger can comprise a gas heat exchanger. Intermediate heat exchangers (not shown) can be employed to separate the waste heat medium from the evaporator. 
     The working fluid  30  is heated in the evaporator  18  and changes phase from a liquid phase to a vapor (or gas) phase. The working fluid  30  having gained the thermal energy  28  and having reached a higher energy state (i.e., vapor or gas phase), flows from the evaporator  18  through piping  32  to the expander  14 , and expands through the expander  14  transferring the higher thermal energy into mechanical energy. The working fluid  30  is compressed (i.e., under pressure) having potential energy as it enters the expander  14  through the inlet  46 . After proceeding through the expander  14 , the working fluid exits through the outlet  48  having transferred the potential energy to the shaft  16  creating kinetic energy. 
     In a preferred embodiment, the shaft  16  of the expander  14  can be coupled directly to a drive shaft of the prime mover  12  through a generator (see  FIG. 5 ) or coupled with belts  34  and/or gears or pulleys  36 ,  38  to the crankshaft  40  (or drive shaft or any other appropriate location) of the prime mover  12  (see  FIGS. 3 and 4 ). The shaft  16  of the expander  14  can also be connected via a pulley and idler arrangement (or directly in the case of the engine&#39;s power take-off (PTO) shaft) (not shown) to the output shaft of the prime mover  12  itself. 
     The preferred expander  14  is a double (or twin) screw expander  32 .  FIG. 6  illustrates a bottom view of an interior of a double screw expander  32 . The double screw expander  32  uses the working fluid  30  to create mechanical rotation. The working fluid  30  expands through the double screw expander  32  causing the two rotors (or screws)  34 ,  36  to turn (or rotate), thus creating mechanical energy. The mechanical energy is transferred into shaft power. Referring now to  FIG. 7 , a front view of a double screw expander  32  is illustrated. The working fluid  30  flows into the double screw expander  32  via inlet  46  and exits via outlet  48 . As the working fluid  30  expands through the double screw expander  32 , mechanical energy is created. The mechanical energy is then transferred into shaft power. 
     A double screw expander  32  has two meshing helical rotors  34 ,  36  that are contained within a casing  42 , which surrounds the rotors  34 ,  36  with a very small clearance. The spaces between the rotors  34 ,  36  and the casing  42  create working chambers  44 . The working fluid  30  enters the double screw expander  32  through inlet  46  and expands through the working chambers  44  in the direction of rotation until it is expelled through outlet  48 . Power is transferred between the working fluid  30  and the shaft  16  from torque created by the forces on the rotor  34 ,  36  surfaces due to the pressure of the working fluid  30 , which changes with the volume of the working fluid  30 . 
     In order to achieve a high flow rate and efficiency, the profile of the rotor  34 ,  36  is important. A conventional profile is illustrated in  FIG. 8 , in which a symmetric profile of the rotors  34 ,  36  is provided. The preferred embodiment for the double screw expander  32  profile is illustrated in  FIG. 9 . A rack generated “N” profile utilized as a rotor profile increases the rotational speed of the double screw expander  32 . 
     Referring again to  FIGS. 2 and 3 , upon exiting the expander  14  through the outlet  48  to piping  50 , the working fluid  30  is now a low pressure gas (or vapor) that flows to a condenser  20 , where the working fluid  30  undergoes a phase change again from vapor (or gas) to liquid. In a preferred embodiment, the condenser  20  comprises at least one of shells, tubes, and fins. The use of a refrigerant, cooling water, or cooling air can enhance the cooling capabilities of the condenser  20 . 
     In still yet another embodiment, referring to  FIG. 10  and  FIG. 11 , the shaft  62  of the expander  32  (such as a double screw expander) is coupled to the shaft  64  of another device, such as the prime mover  12  or a pump  12 B (see  FIG. 11 ) via a clutch device  60 , such as a mechanical clutch, an electrical clutch and/or a Sprag clutch (non-reversible and/or reversible), wherein the clutch device  60  can be used to disengage the shaft  62  of the expander  32  from the shaft  64  of the prime mover  12  to lower the revolutions per minute (RPM) of the expander  32 . Simply put, a clutch is a device that can be engaged or disengaged to transmit/remove rotational forces of a rotating shaft and is particularly useful in mechanisms that include two or more rotating shafts where it is desirable to selectively transmit the motion of one shaft to another shaft. As is known, there are many different types of clutches. One type of clutch, for example, is the “Sprag” clutch which is a one-way overrunning (or freewheel) clutch that can be used to disengage a driveshaft from a driven shaft as desired. A Sprag clutch typically includes a cylindrical inner race surrounded by a cylindrical outer race with an annular space therebetween and is particularly useful when two or more motors can be used to drive the same mechanism or when the disengagement of one motor is desired. The use of a Sprag clutch is advantageous in different situations where it is desirable to lower the revolutions per minute (RPM) of the shaft of the expander  32 . For example, when the prime mover  12  (or pump  12 B) is sitting idle or when the prime mover  12  is not generating enough heat, it may desirable to lower the RPM&#39;s of the shaft  62  of the expander  32  to prevent the expander  32  from being damaged (i.e. burning out). This may be accomplished by engaging the clutch device  60  to allow the shaft  62  of the expander  32  to slow its rotation. When the prime mover  12  is generating a sufficient amount of waste heat, the clutch device  60  may be disengaged to allow the rotation of the shaft  62  of the expander  32  to increase. 
     It should be appreciated that the clutch device  60  may be controlled via any device and/or method suitable to the desired end purpose, such as an electrical switch, a mechanical switch and/or an electromechanical switch. It is contemplated that a sensing device and a controller device may be included in the power compounder system  10 , wherein the sensing device and a controller device are communicated with each other and the power compounder system  10  to monitor various desired parameters of the power compounder system  10 , such as the expander  32  and/or prime mover  12  (and/or pump  12 B). The sensing device may monitor various parameters of the power compounder system  10  as desired, such as the waste heat from the prime mover  12  and/or the rotation speed of the shaft  62  of the expander  32  and/or the shaft  64  of the prime mover  12  and communicate these parameters to the controller device. The controller device may then control the clutch device  60  to engage and/or disengage the shaft  62  of the expander  32  from the rest of the system (i.e. prime mover  12 ) responsive to the parameters received from the sensing device. It is also contemplated that the controller may send instructions to the sensing device to configure which parameters the sensing device will sense. It is further contemplated that the sensing device and/or the controller may be communicated with a computing device (a local device and/or a remote device) to allow a third party to monitor the power compounder system  10  and/or control the clutch device  60  as desired. It is further contemplated that all communications may be accomplished via wired and/or wireless communications. 
     It should be appreciated that as used herein, working fluids include any type of working fluid suitable to the desired end purpose, such as water, steam and/or organics (including, but not limited to refrigerants and/or hydrocarbons). 
     The liquid working fluid  30  then flows by gravity to a receiver tank  52  configured to contain the liquid working fluid  30  (i.e., preferably a tank that is about 30 gallons to about 100 gallons). A feed pump  54  controls the flow rate of the working fluid  30  to the evaporator  18 . A cooling medium, such as liquid or air, can be utilized to further condense the gaseous working fluid into a liquid working fluid. As illustrated in  FIG. 2 , a cooling tower  56  (or cooling fan, and the like) can be utilized to supply the cooling medium. 
     The admission of wet vapor to the expander  14  can be used to improve the performance of the power compounder  10  by simplifying and reducing the cost of expander  14  lubrication by dissolving or otherwise dispersing about 5% oil by mass in the working fluid  30 . 
     The above system is a closed loop Rankine Cycle, employing water as the working fluid, or an Organic Rankine Cycle, using refrigerants or light hydrocarbons as the working fluid, or some combination thereof, in order to produce rotational mechanical power from thermal energy sources. This use of a power compounder results in an increase of net power to the host prime mover of about 5% to about 15% net power, with about 10% net power preferred. 
     The present disclosure includes a simple and reliable cost efficient power compounder system, either a Rankine Cycle or an Organic Rankine Cycle, using a double screw expander to produce rotational power. This rotational mechanical energy can be used to increase power output by as much as about 10% net increase to many prime movers, such as engines, pumps and mechanical power outputs for hundred of applications. Since the rotational speed of the expander of the power compounder is operated at similar rotational speeds as the prime mover, there is no need for any high speed reduction gear reducer or electronics. The rotational mechanical energy of the expander can be synchronized to the rotation of the prime mover. 
     While the disclosure has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure.