Abstract:
The disclosure provides a system including a Rankine power cycle cooling subsystem providing emissions-critical charge cooling of an input charge flow, which includes at least one of an exhaust gas recirculation (EGR) source and a charge air source, upstream of an intake internal combustion engine. The system includes a boiler fluidly coupled to the input charge flow and adapted to transfer heat from the input charge to a working fluid of the Rankine power cycle subsystem and vaporize the working fluid, an energy conversion device fluidly coupled to the boiler and adapted to receive vaporized working fluid and convert the energy of the transferred heat, a condenser fluidly coupled to the energy conversion device and adapted to receive the working fluid from which the energy was converted, a pump having an inlet fluidly coupled to an outlet of the condenser and an outlet fluidly coupled to an inlet of the boiler, said pump adapted to move fluid from the condenser to the boiler, an adjuster that adjusts at least one parameter of the Rankine power cycle subsystem to change a temperature of the input charge exiting the boiler, and a sensor adapted to sense a temperature characteristic of the vaporized input charge. The system includes a controller that can determine a target temperature of the input charge sufficient to meet or exceed predetermined target emissions and cause the adjuster to adjust at least one parameter of the Rankine power cycle to achieve the predetermined target emissions.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation-in-Part (CIP) of U.S. application Ser. No. 12/058,810 filed on Mar. 31, 2008, and claims benefit of priority to Provisional Patent Application No. 61/371,162, filed on Aug. 5, 2010, the entire contents of which are hereby incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    This invention was made with government support under “Exhaust Energy Recovery,” contract number DE-FC26-05NT42419 awarded by the Department of Energy (DOE). The government has certain rights in the invention. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The invention relates to energy conversion from waste heat, and more particularly, to a waste heat recovery system utilizing a Rankine cycle (RC) system that provides emissions-critical charge cooling. 
       BACKGROUND 
       [0004]    A Rankine cycle (RC), such as an organic Rankine Cycle (ORC) can capture a portion of heat energy that normally would be wasted (“waste heat”) and convert a portion of that captured heat energy into energy that can perform useful work. Systems utilizing an RC are sometimes called waste heat recovery (WHR) systems. For example, heat from an internal combustion engine system such as exhaust gas heat energy and other engine heat sources (e.g., engine oil, exhaust gas, charge gas, water jackets) can be captured and converted to useful energy (e.g., electrical or mechanical energy). In this way, a portion of the waste heat energy can be recovered to increase the efficiency of a system including one or more waste heat sources. 
       SUMMARY 
       [0005]    In one aspect of the disclosure, a system includes a Rankine power cycle subsystem providing emissions-critical charge cooling of an input charge flow, which includes at least one of an exhaust gas recirculation (EGR) source and a charge air source, upstream of an intake internal combustion engine. The system includes a boiler fluidly coupled to the input charge flow and adapted to transfer heat from the input charge flow to a working fluid of the Rankine power cycle subsystem and vaporize the working fluid, an energy conversion device fluidly coupled to the boiler and adapted to receive vaporized working fluid and convert the energy of the transferred heat, a condenser fluidly coupled to the energy conversion device and adapted to receive the working fluid from which the energy was converted, a pump having an inlet fluidly coupled to an outlet of the condenser and an outlet fluidly coupled to an inlet of the boiler, said pump adapted to move fluid from the condenser to the boiler, a mechanism for adjusting at least one parameter of the Rankine power cycle subsystem to change a temperature of the input charge flow exiting the boiler, a sensor adapted to sense a temperature characteristic of the input charge flow, and a controller. The controller is adapted to determine a target temperature of the input charge flow that is sufficient to meet or exceed predetermined target emissions and to cause the adjusting mechanism to adjust at least one parameter of the Rankine power cycle to achieve the predetermined target emissions. 
         [0006]    In another aspect of the disclosure, an internal combustion engine includes a Rankine power cycle cooling subsystem that provides emissions-critical charge cooling of an input charge flow, which includes at least one of an exhaust gas recirculation (EGR) source and a charge air source, upstream of an intake of the internal combustion engine. The Rankine subsystem includes a boiler fluidly coupled to the input charge flow and adapted to transfer heat from the input charge to a working fluid of the Rankine power cycle subsystem and vaporize the working fluid, an energy conversion device fluidly coupled to the boiler and adapted to receive vaporized working fluid and convert the energy of the transferred heat, a condenser fluidly coupled to the energy conversion device and adapted to receive the working fluid from which the energy was converted, a pump having an inlet fluidly coupled to an outlet of the condenser and an outlet fluidly coupled to an inlet of the boiler, said pump adapted to move fluid from the condenser to the boiler, an adjuster adapted to adjust at least one parameter of the Rankine power cycle subsystem to change a temperature of the input charge flow exiting the boiler, a sensor adapted to sense a temperature characteristic of the input charge flow, and a controller adapted to determine a threshold temperature of the input charge flow, below which is sufficient to meet or exceed a predetermined target emissions and to cause said adjuster to adjust at least one parameter of the Rankine power cycle to maintain the sensed temperature within the determined threshold temperature. 
         [0007]    In yet another aspect of the invention, a method of cooling input charge flow, which includes at least one of an exhaust gas recirculation (EGR) source and a charge air source, upstream of an intake internal combustion engine, includes providing the input charge flow to a boiler a Rankine power cycle subsystem to transfer heat from the input charge to a working fluid of the Rankine power cycle subsystem and vaporize the working fluid, converting the energy of the transferred heat, condensing the working fluid from which the energy was converted, pumping the condensed working fluid to move the working fluid though the Rankine power cycle, determining a target temperature of the input charge sufficient to meet or exceed predetermined target emissions, sensing the temperature of the input charge flow exiting the boiler; and controlling at least one parameter of the Rankine power cycle to maintain temperature of the input charge at or below the target temperature. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a diagram of a generalized waste recovery system including a Rankine cycle according to an exemplary embodiment. 
           [0009]      FIG. 2  is a diagram of a waste recovery system including a Rankine cycle and recuperator bypass according to an exemplary embodiment. 
           [0010]      FIG. 3  is a diagram of a waste recovery system including a Rankine cycle for cooling at least EGR gas according to an exemplary embodiment. 
           [0011]      FIG. 4  is a diagram of a waste recovery system including a Rankine cycle for cooling an EGR gas and charge air mixture according to an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Various aspects are described hereafter in connection with exemplary embodiments. However, the disclosure should not be construed as being limited to these embodiments. Rather, these embodiments are provided so that the disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Descriptions of well-known functions and constructions may not be described for clarity and conciseness. Further, embodiments other than those described herein can include any alterations and further modifications and further applications of the disclosed principles, which would normally occur to one skilled in the art to which the disclosure relates. 
         [0013]    Embodiments disclosed herein use an ORC to perform at least a portion of the emissions-critical cooling for charge gases, which can include the fresh charge air and/or EGR gases. In order to meet current emission levels, the charge gases must be cooled to some target temperature value in order to obtain a favorable NOx/particulate matter tradeoff. 
         [0014]      FIG. 1  depicts an exemplary embodiment of a system  10  which combines an organic Rankine cycle with an engine (e.g., a diesel engine) to recover waste heat from the engine and convert the heat energy into motive work or to apply or transfer the energy in some other manner. The system  10  generally includes a boiler (or super-heater)  12 , an energy conversion device (e.g., an expander such as a turbine, heat exchanger, etc.)  14  that may be connected to a load (e.g., a generator), a condenser  16 , a pump  18 , a recuperator  22 , and a controller  63 , which collectively constitute an RC subsystem. 
         [0015]    As is further described below, a working fluid (such as Genetron™ R-245fa from Honeywell, Therminol™, Dowtherm J from the Dow Chemical Co., Fluorinol, Toluene, dodecane, isododecane, methylundecane, neopentane, neopentane, octane, water/methanol mixtures, or steam, for example) is passed through system  10  through a series of conduits. Conduit  24  is connected between an outlet  26  of condenser  16  and an inlet  28  of pump  18 . Conduit  30  is connected between an outlet  32  of pump  18  and an inlet  36  of recuperator  22 . Conduit  38  is connected between an outlet  40  of recuperator  22  and an inlet  44  of boiler  12 . Conduit  46  is connected between an outlet  48  of boiler  12  and an inlet  50  of the energy conversion device  14 . Conduit  52  is connected between a waste heat source  54  and an inlet  56  of boiler  12 . Waste heat source  54  may be any acceptable source of waste heat such as EGR gas, charge air, engine coolant, or engine exhaust. Conduit  58  is connected between an outlet  60  of boiler  12 . Depending upon the nature of waste heat source  54 , the waste heat exiting boiler  12  through conduit  58  may be delivered, for example, to the engine&#39;s EGR loop, the vehicle exhaust system, the charge air loop, or the engine coolant loop. 
         [0016]    Conduit  62  is connected between a outlet  64  of energy conversion device  14  (e.g., a diffuser outlet) and an inlet  66  of recuperator  22 . Conduit  68  is connected between an outlet  70  of recuperator  22  and an inlet  72  of condenser  16 . Conduit  74  is connected between a low temperature source  76  and an inlet  78  of condenser  16 . Low temperature source  76  may be, for example, engine coolant, a low temperature coolant loop, and/or ambient air. Finally, conduit  80  is connected between an outlet  82  of condenser  16  and, depending upon the application, the engine cooling loop, a radiator, or the atmosphere. 
         [0017]    In system  10 , boiler  12  is provided to use heat from waste heat source  54  which is passed through boiler  12  to increase the temperature of a working fluid provided to boiler  12  at high pressure. As is further described below, under certain operating conditions, the working fluid is provided to boiler  12  at inlet  44  from recuperator  22  through conduit  38 . When the working fluid leaves boiler  12  at outlet  48 , it is in a gaseous state, at high pressure and high temperature as a result of the heat transferred to the working fluid from waste heat source  54  passed through boiler  12 . This gas is passed through conduit  46  to energy conversion device  14  where the energy from the gas can be used to produce work using techniques that are well understood in the art. For example, energy conversion device  14  can be a turbine that causes rotation of a shaft (not shown) to drive a generator (not shown) for creating electrical power or to drive some other mechanical element to produce mechanical and/or electric power. The additional converted energy can be transferred to the engine crankshaft mechanically or electrically, or used to power parasitics and/or storage batteries. Alternatively, the energy conversion device can be used to transfer energy from system  10  to another system (e.g., to transfer heat energy from system  10  to a fluid for a heating system). 
         [0018]    The energy conversion device  14  does not convert all of the heat energy from the working fluid into work. Thus, the working fluid discharged from energy conversion device  14  at outlet  64  remains in a high temperature, gaseous state (for some working fluids). As is further described below, the working fluid is passed through conduit  62  to recuperator  22  where, under certain operating conditions, it is used to transfer heat to the working fluid discharged from the condenser  16 . The working fluid then passes through conduit  68  to condenser  16 , where it is cooled by low temperature source  76  coupled to condenser  16 . The working fluid discharged from condenser  16  though conduit  24  is in a low temperature, low pressure liquid state. As should be understood by those skilled in the art, condenser  16  is used to decrease the temperature of the working fluid for at least two reasons. First, although high temperature working fluid is desirable to obtain maximum work from energy conversion device  14  (i.e., to obtain maximum efficiency of the Rankine cycle), the primary requirement of system  10  is to maintain the desired heat rejection from waste heat source  54  passed through boiler  12 . Accordingly, a low temperature working fluid should be provided to boiler  12 . Second, increasing the pressure of the working fluid in its liquid state takes substantially less energy than increasing its pressure when in the gaseous state. As such, pump  18 , which provides this pressure increase, may be less robust and less expensive than would otherwise be required for a gas pump. 
         [0019]    The working fluid at outlet  32  of pump  18  is provided through conduit  30  to inlet  36  of recuperator  22  and inlet  34  of bypass valve  20 . As will be further described below, under high load engine operating conditions, bypass valve  20 , which is controlled by controller  63 , is moved to an opened position, passing at least some of the low temperature working fluid directly to boiler  12 . Under partial load engine operating conditions, which constitute the normal engine operating conditions, bypass valve  20  is moved to a closed position, thereby permitting the low temperature working fluid to flow through conduit  30  to recuperator  22 . As described above, recuperator  22  provides heat transfer from the high temperature discharge gas from turbine  14  to the low temperature liquid provided by pump  18 . This heat transfer increases the temperature of the working fluid (which remains in a liquid state) provided to boiler  12 . Of course, higher temperature working fluid does not cool the waste heat streams passing through boiler  12  as effectively as cooler working fluid, but under most operating conditions, the heat rejection provided by the higher temperature working fluid is satisfactory. Moreover, because the working fluid enters boiler  12  at an elevated temperature, the working fluid provided from boiler  12  to turbine  14  (in a gaseous state) is at a higher energy state than it would otherwise be had recuperator  22  not been used. This provides greater energy to turbine  14 , which consequently can generate a greater work output. 
         [0020]    As indicated above, system  10  should be designed to operate over a wide range of conditions. For purposes of system  10 , the operating conditions are primarily reflected by the temperature and pressure of waste heat provided to boiler  12 . When waste heat source  54  is part of an EGR loop, the waste heat discharge  58  must not be permitted to exceed a maximum threshold temperature. In some applications, the outlet temperature of the waste heat flowing through conduit  58  from boiler  12  must be low enough to enable the engine to meet emission requirements imposed on the engine. If the required engine waste heat stream cooling is not met (if it is charge air, engine coolant or EGR gases) the engine will be non-compliant with emission regulations. If the waste heat stream is exhaust gas, this is not an issue because exhaust gas that is expelled out the exhaust stack is not required to be cooled. 
         [0021]    Further, the inventors have recognized that at least a portion of the required charge cooling to meet a target emissions value, for example, a government mandated value, can be accomplished using the system  10 . This is accomplished by transferring heat from the charge air and/or EGR to a high pressure working fluid in the RC subsystem in accordance with a control scheme carried out by the controller  63 . The controller  63  can be an engine control module (ECM), also called an engine control unit (ECU), or another controller separate from the ECU, or one or more distributed control devices communicating with an ECM/ECU. The controller can include software and/or hardware for determining a maximum threshold temperature waste heat of EGR and/or charge air flowing through the conduit  58  to the intake manifold of the engine (not shown), and include other modules for controlling at least one parameter of the operation of system  10  to ensure the engine is operating within a required maximum emission level. 
         [0022]    For example,  FIG. 1  shows plural controller signal lines  90 - 98 , each of which can carry sensing and/or control signals. In an embodiment, the controller can receive a signal provided by a sensor provided at conduits  52  and/or  58 . The sensor can be a temperature (T) sensor or a combination of a T sensor and a pressure (P) sensor thereof (e.g., delta T or P sensors) to create a signal on lines  90  and/or  92  indicative of the temperature and/or temperature/pressure combination of waste heat flowing in these conduits, and the controller receives this information from signal lines  90  and/or  92  and determines which parameter(s) of the Rankine subsystem to adjust to bring the temperature of the waste heat flow, for example, the temperature of the input charge (EGR gas and/or charge air) exiting the boiler/superheater  12  below a maximum threshold temperature needed to maintain emissions at or below a required or desired maximum level. Determination of a maximum temperature (and/or pressure) for maintaining emissions at or below a required or desired emission level can involve using an algorithm, accessing a look-up table, a map or some other known way of determining a maximum input charge temperature value. Additionally, the maximum threshold temperature for waste heat of EGR and/or charge air can vary based on the current operation mode or a predicted operation mode of the engine. The controller can provide adjustments to the operation of the system  10 , such causing a portion of all of the waste heat to bypass one or more of the components of the system  10 . For example, as described below in detail, a signal line  98  can provide a control signal to the recuperator  22  or system elements (not shown in  FIG. 1 ) that are associated waste heat flow through the recuperator. Additional controls can include controlling a parameter of the Rankine cycle subsystem to control an amount or rate of cooling performed by the low temperature source  76  via controller signal line  94  and controlling pump  18  via controller signal line  96 , for example, via modulating the pump speed or restricting fluid flow at the pump  18  or at another point along the RC cycle loop. Also, the controller signal lines  90 - 98  can provide the controller  63  with information (e.g., in real-time) related to the health of the various system components. 
         [0023]    Under ordinary engine load conditions, the low temperature working fluid from condenser  16  provides more than enough cooling to the waste heat passed through boiler  12 . Accordingly, under normal load conditions, the working fluid is passed through recuperator  22 , which both reduces the temperature of the working fluid provided to condenser  16  and increases the temperature of the working fluid provided to boiler  12 . More specifically, as gaseous working fluid passes through a first flow path of recuperator  22  from inlet  66  to outlet  70 , it transfers heat to the lower temperature liquid working fluid passing though a second flow path from inlet  36  to outlet  40 . As a result, the gaseous working fluid provided to condenser  16  is cooler, and easier for condenser  16  to condense to liquid. Also, the liquid working fluid provided to boiler  12  is at a higher temperature. Consequently, the gaseous working fluid provided to energy conversion device  14  after heating in boiler  12  is at a higher energy state than it would otherwise be if recuperator  22  were not in the cycle. While less heat is removed from the waste heat, under normal load conditions, the waste heat temperature can be maintained below a maximum threshold for meeting the required emissions. Thus, system  10  can accommodate the added heat provided by recuperator  22  and realize greater efficiency because the added heat permits the energy conversion device  14  to create more useful work or to transfer greater amount of energy. 
         [0024]    As an engine load increases (e.g., during acceleration, uphill driving, when pulling a heavy load, etc.), more, higher temperature waste heat is provided to boiler  12 . As described above, in engine systems where waste heat source  54  is in an EGR loop and/or a charge air loop, for example, boiler  12  must extract enough heat from the waste heat to ensure that it remains below the maximum threshold temperature to ensure operation at or below predetermined emissions target value. As such, system  10  is designed to sense the increased load conditions and correspondingly activate controls to adjust the waste heat flow temperature via the controller  26 . As described above, controls can be activated based on a target temperature that corresponds to a target emissions level, and the target temperature can have a value that is different for different operating modes and/or loads. 
         [0025]      FIG. 2  is a diagram of a system  100  according to an exemplary embodiment in which charge air and/or EGR is cooled to meet a target emission level using a working fluid of an RC (e.g., an ORC), and the working fluid is controlled to bypass the recuperator under various engine load conditions. In this embodiment, the energy conversion device includes a combination of an expander (turbine)  140  and generator  142 . Description of elements of  FIG. 2 , and in  FIGS. 3 and 4  described hereafter, having the same reference numbers as in  FIG. 1  is given above. 
         [0026]    As shown in  FIG. 2 , conduit  30  is connected between an outlet  32  of pump  18 , an inlet  34  of bypass valve  20 , and an inlet  36  of recuperator  22 . Conduit  38  is connected between an outlet  40  of recuperator  22 , an outlet  42  of bypass valve  20 , and an inlet  44  of boiler  12 . A temperature sensor  61  is coupled to conduit  58  to detect the temperature of the waste heat exiting boiler  12 , and provide an output signal on signal line  90  to controller  63  which provides a signal on signal line  98  that controls the position of bypass valve  20 . 
         [0027]    With an increase in engine load, a higher temperature waste heat is provided to boiler/superheater  12 . As described above, in engine systems where waste heat source  54  is in an EGR loop and/or a charge air loop, for example, boiler  12  must extract enough heat from the waste heat to ensure that it remains below a maximum threshold temperature for that load such that operation at or below predetermined emissions target value is ensured. System  100  senses the increased load conditions and correspondingly activates bypass valve  20 , if required, to direct working fluid directly from condenser  16  (though pump  18 ) to boiler  12 . In the depicted embodiment of  FIG. 2 , sensor  61  senses the waste heat temperature flowing though conduit  58 . In an embodiment, sensor  61  can provide an output signal indicative of the temperature of this waste heat to controller  63 . Controller  63  includes electronics (not shown) which can interpret the output signals from sensor  61  to determine the engine load level. When the load level reaches a predetermined level, as indicated by sensor  61 , controller  63  causes bypass valve  20  to open partially, thereby directing some of the cooler working fluid flowing though conduit  30  directly from pump  18  to boiler  12 . As the engine load increases, controller  63  can further open bypass valve  20  to direct more cooler working fluid directly to boiler  12  (i.e., bypassing recuperator  22 ). The system  100  can be designed such that when bypass valve  20  is fully opened, enough cooler working fluid is provided to boiler  12  to prevent the waste heat exiting boiler  12  from exceeding a predetermined maximum temperature. 
         [0028]    It is to be understood that other control systems may be employed to sense or determine engine load and correspondingly control bypass valve  20 . For example, one skilled in the art can readily envision a predictive control system wherein engine load is monitored more directly, and bypass valve  20  is adjusted based on the expected temperature of the waste heat stream exiting boiler  12 . In this configuration, the system anticipates the thermal lag experienced in the heat exchangers resulting from changes in engine operating conditions. 
         [0029]    As a result of the bypassing described above, under increasing load conditions at least a portion of the working fluid is not passed through recuperator  22  where its temperature would be elevated prior to entering boiler  12 . The working fluid flow rate is reduced compared to what the flowrate would have been without the recuperator bypass valve in the system under these conditions because the heat input from recuperator  22  is removed. Higher temperature gases discharged from turbine  140  are then cooled by condenser  16 . This results in higher pressure at condenser  16 , a lower pressure ratio at turbine  140 , and a correspondingly lower power output of turbine  140 . In other words, the efficiency of system  100  is reduced because the condenser  16  must cool the working fluid discharged from turbine  140  without the benefit of recuperator  22  cooling the working fluid, and because the working fluid provided turbine  140  from boiler  12  is not pre-heated by recuperator  22 . As the high load conditions occur for only a relatively small percentage of the engine&#39;s operating time (e.g., five to ten percent), this loss in efficiency can be acceptable. 
         [0030]    As should be apparent from the foregoing, system  10  may be designed for efficient operation at the most common operating point (i.e., normal engine load conditions) as the recuperator  22  bypass feature permits system  10  to accommodate the peak heat rejection requirements that occur under high load conditions. As such, a lower power turbine  140  may be selected. More specifically, if bypass valve  20  were not included in system  10 , turbine  14  would be required to withstand the high load operating conditions described above, even though those high load conditions occur relatively infrequently. This would require a more robust, more expensive turbine  140  (e.g., a maximum output of 35 KW), which would be essentially under-utilized most of the time (i.e., under normal load conditions). By implementing the bypass feature described above, a less robust, less expensive turbine  140  may be used (e.g., a maximum output of 25 KW). 
         [0031]    Additionally, by placing bypass valve  20  at the output of pump  18  rather than on the high temperature side of system  100 , bypass valve  20  may be designed for operation with a lower temperature liquid rather than a high temperature gas. Accordingly, bypass valve  20  may be more compact, simpler, and less expensive than would otherwise be required. Moreover, the flow rate and power of pump  18  may be lower than would otherwise be required. 
         [0032]      FIG. 3  shows an exemplary ORC cooling system  200  according to an embodiment in which only EGR gases are cooled using an ORC subsystem system A, where charge cooling by subsystem A is required to meet a target emission level, which can be a predetermined current allowable or a desired engine emission level. 
         [0033]    As shown in  FIG. 3 , ORC subsystem A transfers thermal energy of the EGR gases exiting the exhaust manifold  210  of an engine  211  to the working fluid of subsystem A. More specifically, the ORC subsystem A includes a feed pump  18  that moves high pressure liquid working fluid to an inlet of a boiler of a boiler/superheater  12 , where heat from EGR charge gases is transferred to the ORC working fluid. In the boiler/superheater  12 , the working fluid boils off and produces a high pressure vapor that exits the boiler/superheater  14  at the superheater and enters an inlet of a high pressure expander (turbine)  140 . 
         [0034]    The ORC cooling system  200  is capable of producing additional work output from the high pressure turbine  140 . For example, the additional work can be fed into the engine&#39;s driveline either mechanically or electrically, or it can be used to power electrical devices, parasitics or a storage battery. In the embodiment shown in  FIG. 3 , the expanding vapor turns the turbine  140 , which turns an electrical generator  142 . The power generated by the generator  142  can be feed into a driveline motor generator (DMG)  220  via power electronics  222 . The expanded gases exit the outlet of the turbine  16  and are then cooled and condensed via a condenser  16 , which can be cooled by a LTS, which in this case is a liquid loop including a condenser cooler  226  having RAM airflow and condenser cooler pump  228 , although other condenser cooling schemes can be employed such as a direct air-cooled heat exchanger. The condensed working fluid exits the outlet of the condenser  16  and is supplied to the feed pump  18  to complete the cycle and increase the working fluid pressure. Although not shown, a boost pump also can be provided to prevent feed pump  18  from cavitating. 
         [0035]      FIG. 3  shows that the ORC subsystem A includes a recuperator  22  in the working fluid path from the turbine  140  to the condenser  16  and in the path from the feed pump  18  to the boiler of the boiler/superheater  12  to increase thermal efficiency of the RC. As described above, the recuperator  22  is a heat exchanger in which includes two paths. The working fluid moves along a first of these paths after exiting the outlet (not shown) of the turbine  140  before proceeding to the condenser  16 . While in the first path, the recuperator  22  reduces the temperature of the working fluid before the fluid enters condenser  16 . After traversing the condenser  16 , the working fluid is moved by the feed pump  18  in a second path through the recuperator  22 . Along the second path, heat is transferred back from the recuperator  22  into the now lower temperature working fluid before being provided to the boiler/superheater  12 . Although not shown in  FIG. 3 , EGR gases leaving the ORC subsystem A can require additional cooling using traditional cooling systems, for example, using a low temperature liquid cooling loop or direct cooling with air. 
         [0036]    The EGR charge can be combined with charge air that has been compressed by a compressor  234  coupled to and driven by a turbine  236  powered by exhaust gases exiting the exhaust manifold  210 . The charge air is heated when compressed by the compressor  234 . The heated charge air is provided to a charge air cooler (CAC)  238 , where it is cooled before being combined with the cooled EGR gas at a mixer  240 . The combined charge mixture including the cooled EGR gas and the cooled and compressed charge air is provided to the intake manifold  242  of the engine  211 . The amount of EGR charge gas flow can be controlled by an EGR valve  232 . 
         [0037]    The system  200  also includes a sensor  261  coupled to the EGR gas flow upstream from the boiler/superheater  12  for sensing the temperature of the EGR gas, as described above with respect to  FIG. 1 . While sensor  261  is shown positioned upstream of the EGR valve  232 , sensor  261  can be provided anywhere upstream of the boiler. Also, while not shown in  FIG. 3 , the recuperator  22  can include a bypass valve  20  as shown in the system  10  of  FIG. 2 . Another temperature controlling mechanism shown in system  200  is a flow restrictor  262  that is controllable by controller  63  to regulate a rate of flow of the working fluid in the ORC subsystem A. The system  200  can include only one control or plural controls for adjusting the temperature of waste heat flow (EGR) exiting the ORC subsystem A. When employing plural control mechanisms, each may be used alone at times, or in conjunction with any combination of other control mechanisms at other times to achieve a desired cooling speed and volume of gas for cooling. 
         [0038]      FIG. 4  shows an ORC charge cooling system  300  according to an embodiment in which the ORC subsystem A cools both the EGR gases and charge air in a combined charge cooler. Items having the same reference number as items in any of systems  10 ,  100  and  200 , are described above. 
         [0039]    As shown in  FIG. 4 , the air charge discharged from the compressor  234  is mixed at a mixer  340  with the EGR gases from the EGR valve  232  and the charge mixture is passed through the ORC heat exchanger (i.e., the boiler/superheater  12 ) for heat transfer to the ORC. The cooled gas mixture is provided to an inlet of the charge cooler  338  (e.g., CCAC) to be further cooled, and the cooled mixture exiting the outlet of the charge cooler  338  is provided to the intake manifold  242  of the engine  211 . 
         [0040]    Other embodiments can include variations of heat input from charge gases. These include the use of a charge air only heat input system. Another variation is the use of charge air and EGR cooling where the gases remain unmixed, the charge air and EGR heat inputs to the ORC could be in a parallel or series heat input configuration. Also, the charge cooler can be excluded entirely or a bypass valve provided therein to allow for additional temperature control. 
         [0041]    Additionally, other heat sources related to engine cooling can be included in an embodiment of a charge cooling system utilizing an RC and energy conversion device to increase the power recovery, including jacket water, oil cooling or exhaust gas cooling. 
         [0042]    Although a limited number of embodiments is described herein, one of ordinary skill in the art will readily recognize that there could be variations to any of these embodiments and those variations would be within the scope of the disclosure.