Patent Publication Number: US-9845711-B2

Title: Waste heat recovery system

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under contract number DE-EE0003403-Recovery Act-System Level Demonstration of Highly Efficient and Clean, Diesel Powered Class 8 Trucks (SUPERTRUCK) awarded by the Department of Energy (DOE). The government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     The technical field relates to waste heat recovery systems utilizing a Rankine cycle circuit coupled to a gear assembly, and more particularly, to returning oil present in the working fluid of the Rankine cycle circuit to the gear assembly. 
     BACKGROUND 
     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 the 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 or other engine waste heat sources (e.g., engine oil, charge gas, engine block cooling jackets) can be captured and converted to useful energy (e.g., electrical and/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 
     The present disclosure relates to a waste heat recovery (WHR) system including Rankine cycle (RC) circuit coupled to a gear assembly, and to returning oil that has migrated into the RC circuit from the gear assembly back to the gear assembly. 
     In an aspect of the disclosure, a WHR system includes an RC circuit having a boiler fluidly connected to a pump downstream of the pump, an energy converter fluidly connected to the boiler downstream of the boiler, a condenser fluidly connected to the energy converter downstream of the energy converter and fluidly connected to the pump upstream of the pump, each fluid connection between the boiler, pump, energy converter and condenser comprising a conduit. A gear assembly is mechanically coupled to the energy converter of the RC circuit and includes a capacity for oil. An interface is positioned between the RC circuit and the gearbox assembly and is configured to partially restrict movement of oil present in the gear assembly into the RC circuit and to partially restrict movement of working fluid vapor present in the RC circuit into the gear assembly. An oil return line is fluidly connected to at least one of the conduits and is operable to return to the gear assembly oil that has moved across the interface from the gear assembly to the RC circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a waste heat recovery system including an oil scraper positioned after an outlet of an energy converter according to an exemplary embodiment. 
         FIG. 2A  is a diagram showing a section of a working fluid conduit including a bend and an oil scraper;  FIG. 2B  is a diagram of a cross section taken across section B-B of the working fluid conduit shown in  FIG. 2A ; and  FIG. 2C  is a diagram showing an enlarged view of a trapping channel of the oil scraper shown in  FIGS. 2A and 2B . 
         FIG. 3  is a diagram of a waste heat recovery system including an oil scraper positioned before an inlet of an energy converter according to an exemplary embodiment. 
         FIG. 4  is a diagram of a waste heat recovery system including controllably diverting amounts of working fluid/oil mixture output from a pump to gearbox oil according to an exemplary embodiment. 
         FIG. 5  is a diagram of a control system according to an exemplary embodiment. 
         FIG. 6  is a diagram of an internal combustion engine coupled to a waste heat recovery system according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides a waste heat recovery (WHR) system including a Rankine cycle circuit, gearbox assembly, and lubrication oil/working fluid separation system that separates and collects oil accumulated in the working fluid of the organic Rankine cycle and prevents excessive amount of oil from accumulating in the working fluid and returns the separated oil to the gearbox assembly. Exemplary embodiments of the WHR system will be described herein. Identical or similar elements, parts or components are provided with the same reference number in all drawings. However, the disclosure should not be construed as being limited to these embodiments. Rather, these embodiments are provided as examples so that the disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Descriptions of well-known functions and constructions may not be provided for clarity and conciseness. 
       FIG. 1  is a diagram of a WHR system  1  utilizing a lubrication oil/working fluid separation system according to an exemplary embodiment. The WHR system  1  includes a Rankine cycle, which can increase the thermal efficiency of an internal combustion engine, for example, of a gasoline or diesel engine system, by utilizing internal combustion exhaust gas heat energy and/or heat energy generated by an exhaust aftertreatment system. More specifically, WHR system  1  includes a pump  10  (e.g., a feed or liquid pump) configured to move working fluid through a circuit including a boiler  12 , an energy converter  16 , which can be a high pressure expander (e.g., a turbine), and a condenser  18 . Pump  10 , boiler  12 , energy converter  16 , and condenser  18  are fluidly connected via conduits  20   a - 20   d  to form a Rankine cycle circuit using conduits shown as solid black arrows in  FIG. 1  except for conduit  20   c  fluidly connecting energy converter  16  to condenser  18 . Conduit  20   c  is depicted in cross sectional view and includes an oil scraper  22 , which is described later in detail. 
     Boiler  12  includes one or more working fluid passageways (not shown) between boiler inlet  24  and outlet  25 . Each working fluid passageway is in thermal communication with heated fluid  26  of a waste heat source (WHS)  27  (e.g., exhaust gas) flowing through one or more coolant passageways (not shown) fluidly separate from any working fluid passageway, between an inlet  28  and an outlet  30  of boiler  12 . In boiler  12 , heat from heated fluid  26  is transferred to the working fluid, which causes the working fluid to boil off and produce a high pressure vapor. 
     Energy converter  16  is capable of producing additional work or transferring energy to another device or system. For example, energy converter  16  may be a turbine, piston, scroll, screw, vane, swash plate, or other type of gas expander that moves, e.g., rotates, as a result of expanding working fluid vapor to provide additional work. The additional work can be fed into the engine&#39;s driveline to supplement the engine&#39;s power either mechanically, hydraulically or electrically (e.g., by turning a generator), or it can be used to drive a generator and power electrical devices, parasitics or a storage battery (not shown). Alternatively, energy converter  16  can be used to transfer energy from one system to another system (e.g., to transfer heat energy from the waste heat recovery system to another engine system requiring shaft work such as a compressor, alternator, A/C compressor, etc. or to a fluid for a heating system). 
     Energy converter  16  operates by receiving the high pressure vapor of the working fluid from boiler  12  and converting the energy of the high pressure vapor into another useful form of energy to provide the additional work. The working fluid exiting the outlet of energy converter  16  is an expanding gas vapor that flows through conduit  20   c  to an inlet  34  of condenser  18 . After entering the condenser inlet  34 , the working fluid flows through one or more passageways (not shown) of the condenser  18  that are in thermal communication with a cooling medium such as coolant or air  37  flowing from a low temperature source (LTS)  38  into one or more passageways (not shown) between inlet  40  and outlet  42  of condenser  18 . Heat is transferred in condenser  18  from the working fluid vapor to the cooling medium, which cools and condenses the working fluid vapor to liquid form before exiting the condenser at an outlet  43 . LTS  38  can be, for example, part of a liquid cooling loop including a condenser cooler (not shown) and a condenser cooler pump (not shown), a glycol cooling loop, and/or a system in which working fluid is directly cooled with an air-cooled heat exchanger (e.g., ram air). The condensed and cooled working fluid is provided at a lower pressure to pump  10 , which increases the working fluid pressure to repeat the Rankine cycle. 
     The working fluid can be an organic 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, or water/methanol mixtures, or steam in a non-organic RC embodiment), for example. In the boiler  12 , the working fluid boils off and produces a high pressure vapor that exits the boiler outlet  16  and flows to an inlet of an energy converter  22 , 
     While not shown, the WHR system  1  or any other embodiment consistent with the present disclosure can include other components, for example, a superheater provided with boiler  12 , a recuperator that transfers heat from working fluid from the outlet of energy converter  16  to cooled working fluid between pump  10  and boiler  12 , one or more receivers, and/or one or more other components. Additionally, a WHR system consistent with the present disclosure can include pressure, temperature, fluid flow and/or speed sensors (not shown), for example, pressure and/or temperature sensors can be positioned at or near the inlet and/or outlet of each of the pump  10 , boiler  12 , energy converter  16 , and condenser  18  to monitor the status and performance of various aspects of the system. Signals provided by these sensors can be received by a controller device, such as an engine control module (ECM), which can control one or more components of the WHR system or an engine system based on the received signals. 
     Power produced by energy converter  16  is capable of producing additional work or transferring energy to another device or system. In WHR system  1 , power of the energy converter  16  is mechanically coupled to a gear assembly  44 , which in turn is mechanically fed to a driveline (not shown) to supplement engine power and improve fuel economy. The power output of the energy converter  16  also can be used to perform other mechanical or electrical work, for example, turning a generator, power electrical devices, parasitics, charge a storage battery (not shown), or transfer energy from system to another system (e.g., to transfer heat energy from WHR system  1  to a fluid for a heating system). 
     Gear assembly  44  includes a gearbox  45  that houses gears  47  and  49  respectively attached to an input shaft  46  and an output shaft  48 , associated bearing assemblies (not shown), and an oil reservoir  50  that is in fluid communication with the gearbox  45 . While the oil reservoir  50  is shown in the exemplary embodiments as laterally adjacent the gearbox assembly  44 , oil reservoir  50  can be located in another position. For example, oil reservoir  50  can be located below the gearbox  45  so oil can fall down to it. As shown in the exemplary configuration of  FIG. 1 , a weir  51  is provided across the lower portion of the gearbox  45  to hold the oil on the oil tank side and prevent the gear from constantly sloshing through liquid oil. There also can be provided collectors/scrapers on the walls of the gearbox  45  (not shown) that direct the oil that collects due to the spinning vapor inside the gearbox  45  toward weir  51  and over it to the oil reservoir side to reduce how much the oil interacts with the spinning gear. 
     In an embodiment, a rotational speed of output shaft  48  is reduced relative to the rotational speed of input shaft  46  and a torque at output shaft  48  is increased relative to a torque at the input shaft  46  in a manner corresponding to a reduction ratio of the gearbox  45 . It is to be understood that gearbox  45  can include a different number of gears than what is depicted in the figures herein and an output to input ratio corresponding to a particular application of the converted power. 
     Gearbox  45  includes an input shaft seal  52  and an output shaft seal  54 . Input shaft seal  52  forms an interface that operates more as a flow restriction device that partially restricts movement of oil present in gear assembly  44  into the RC circuit and partially restricts movement of working fluid present in the RC circuit into gear assembly  44 . That is, input shaft seal  52  it is not a perfect seal. In an embodiment where gearbox  45  has a reduction ratio between input shaft  46  and output shaft  48 , input shaft seal  52  is a high speed input shaft/energy converter interface and output shaft seal  54  is a low speed and a more perfect seal. The imperfect seal  52  allows for lubricating any of the moving parts in the system such as the pump  10 , the valves etc. The less than perfect input shaft seal  52  allows oil from gearbox  45  to cross the interface of high speed input shaft seal  52  from gearbox  45  to energy converter  16 , and working fluid vapor in energy converter  16  to cross the interface of high speed input shaft seal  52  from energy converter  16  to gearbox  45  during various engine operating conditions. For instance, low-side pressure at the energy converter  16  can fluctuate rapidly during engine transients and cause pressure gradients where oil can escape the gearbox  45  and enter the Rankine cycle circuit through input shaft seal  52 . 
     A vapor vent  55  is also provided to vent the gear assembly  44  at times where the gearbox pressure is higher than the pressure at outlet of energy converter  16  to return working fluid vapor in gear assembly  44  to the Rankine cycle circuit when the gear assembly  44  is at a higher pressure compared with pressure in conduit  20   c  at the discharge from energy converter  16 . A return line  56  including a check valve  57  to prevent back flow of working fluid vapor into the gearbox when the energy converter outlet is at a higher pressure. Vapor vent  55 , return line  56  and check valve  57  allow for a “clean vapor” vent location from the oil tank rather than pushing oil and working fluid vapor out the input shaft seal  52 . This can occur during a considerable amount of operating points, for example, due to the pumping action of a turbine wheel that creates a lower pressure inside the gearbox  45  compared with the pressure at the turbine outlet. If working fluid vapor were allowed to vent into gearbox  45 , there would be a continuous flow of oil/working fluid vapor out the input shaft seal  52 . 
     In addition to crossing the boundary of the high speed input shaft seal  52  from gearbox  45  to energy converter  16 , oil in the form of oil mist can leave gear assembly  44  via vent  55  and vent line  56  along with the working fluid vapor returning to the Rankine circuit. As a result, oil can accumulate in the working fluid and decrease the system performance. For example, an oil film can form on components of the Rankine cycle circuit and reduce heat transfer in the heat exchangers, i.e., boiler  12  and condenser  18 . Additionally, excessive loss of oil in the gearbox  45  can lead to insufficient lubrication of gearbox moving parts. Further, in embodiments using a turbine as an energy converter  16 , oil can reduce the turbine work due to momentum transfer of the liquid oil droplets onto turbine blades (not shown). Oil droplets can also cause damage to turbine blades over sustained periods of time. 
     In the present embodiment, WHR system  1  includes an oil scraper type oil return system that separates gearbox oil from the working fluid to keep an excessive amount of gearbox oil from accumulating in the working fluid of the Rankine cycle circuit and returns the oil to the gear assembly  44 . The oil return system in the present embodiment utilizes oil scraper  22  provided on the conduit  20   c  leading from the outlet of energy converter  16  to condenser  18 . Oil scraper  22  includes an oil collector  58  and at least one channeling structure  60 , such as a gutter, groove or obstruction that collects oil impacting the wall of the conduit  21  and provides a channel or path to direct the collected oil to an opening  62  on oil collector  58 . The opening  62  can be, for example, at least one slit pointed into the direction of working fluid vapor flow. Each channeling structure  60  preferably leads to the opening such that it substantially lines up with a component of the vapor flow direction in conduit  20   c . Oil that has traveled to the outlet of energy converter  16  tends to impact the wall of conduit  20   c  due to rotation of the turbine wheel/refrigerant vapor. 
     The oil collector  58  of oil scraper  22  has a positive pressure gradient because conduit  20   c  is often at a greater total pressure, i.e., static plus dynamic pressure, compared with the static pressure of gear assembly  44 . Oil that impacts the wall of conduit  20   c  and is collected by channeling structure  60  and oil collector  58  is drained back to the gear assembly  44  via an oil return line  64  and check valve  65  provided between collector  58  and oil reservoir  50 . While the embodiment shown in  FIG. 1  returns oil collected by oil scraper  22  to the oil reservoir  50  or gearbox  45  in a passive manner. There is always some flow of refrigerant vapor back to the oil reservoir and that is acceptable because the vapor vent  55  allows that refrigerant vapor to travel back to the refrigerant circuit. The oil return line is of sufficiently small diameter because the return oil rate of flow is not appreciably high, and thus restricts how much refrigerant vapor travels back to the gearbox assembly  44  since there is fairly low dP to drive the vapor that direction along with a small diameter return line. 
     Oil that gets past oil scraper  22  travels on to condenser  18  where it mixes with the liquid working fluid. A POE oil (Polyolester oil) that is miscible with the working fluid can be used as the gearbox lubricant, although other miscible oils could be used. While it is possible to use non-miscible oils in some embodiments, miscible oils provide the advantage not separating out in locations of the system where it provides advantageous effects. Any oil in the working fluid is pumped through the Rankine circuit and is eventually separated from the working fluid as the working fluid boils/vaporizes in the boiler  12 . The liquid oil remaining tends to wet the walls of the conduit where the working fluid vapor is present and is eventually carried through to the outlet of energy converter  16  (e.g., an outlet of a turbine). Oil also can arrive at the outlet of energy converter  16  due to pressure gradients across the input shaft seal  52  during engine transients. Additionally, with a turbine as energy converter  16 , during operation at light to moderate load where the pumping action of the turbine wheel is greater than the flow dynamics at the face of the turbine wheel. Any oil that comes out the input shaft seal  52  ends up at the conduit  20   c.    
     To further enhance impact of the oil onto the wall of conduit  20   c , oil scraper  22  can be positioned at or near a bend in conduit  20   c .  FIGS. 2A and 2B  show a portion of conduit  20   c  including a bend portion  68  and oil scraper  22  according to an exemplary modification of the embodiment shown in  FIG. 1 . 
     In bend portion  68 , working fluid downstream of boiler  12  (see  FIG. 1 ) flows into end shown in cross section facing in a direction normal to the drawing sheet. Arrow  66  indicates direction of flow of the working fluid in conduit  20   c  as the working fluid flows from one end  70  to the other end  71  of bend portion  68 . In an embodiment in which energy converter  16  includes a turbine, the flow direction  66  can include both rotational and tangential components as can be seen in  FIGS. 2A and 2B . Embodiments may not include a turbine and/or rotational movement as depicted in  FIGS. 2A and 2B  at the output of the energy converter. For instance, even the turbine expander when running ideally can have little or no flowing vapor rotation at the outlet. In any event, the oil scraper  22  can work in such a scenario because the oil will coalesce even due to gravity or will impact the wall as flowing vapor changes direction going around the bend in the conduit  20   c.    
     As the working fluid vapor advances through the bend portion  68 , liquid oil in the flow tends to wet the inner wall of conduit  20   c  from the rotational flow of the working fluid vapor and the bend portion  68  causes oil to impact the wall of conduit  20   c . However, wall wetting would occur in other situations, for example, if conduit  20   c  is a straight section, due to gravity settling out the oil mist/droplets, or from the natural turbulence of the vapor as it moves down the pipe. Once the oil impacts the wall anywhere, it would tend to stay in contact with the wall due to surface tension of the oil. Also, the oil would tend to move toward the lowest point in the tube due to gravity and the oil&#39;s higher density than the working fluid vapor. Also, in a curve or other geometry change, the oil would tend to impact the wall and coalesce. In bend portion  68 , channel structure  60  includes plural channels  60   a  and  60   b  provided on the inner wall of conduit  20   c . Each channel  60   a ,  60   b  has one end distal to collector  58 , another end proximate collector  58 , and extends along a path in conduit  20   c  that intersects a tangential path of the working fluid vapor traversing the section of the conduit the channel. The channels  60   a ,  60   b  collect and guide oil on the inner wall of conduit  20   c  through opening  62  of oil collector  58  and into a storage volume of collector  58  where it is stored until being returned to gear assembly  44  via oil return line  64 . Although  FIGS. 2A and 2B  show a channel structure  60  including two channels  60   a ,  60   b , conduit  20   c  can include only one channel or more than two channels. 
       FIG. 2C  shows a cross section of a portion of conduit  20   c  in the vicinity of an exemplary channel structure  60  in a more detailed and enlarged view. Arrow  66  in  FIG. 2C  represents the rotational and translational flow components of the working fluid vapor shown in  FIGS. 2A and 2B . Liquid oil in the working fluid vapor generally follows the directional path of the vapor, and that oil is collected by the channel (gutter) when a section of the channel forms an acute angle to zero angle with the direction of vapor flow (at that channel section). In addition, even without a gutter or channel feature, oil will tend to collect preferentially at the bottom of the tube. However, the angle of the channel can run in a way that the refrigerant vapor flow will cause it to efficiently collect in a single location for return back to the oil tank. Channel structure  60  includes a gutter  72  formed in the wall of conduit  20   c , for example, by a stamping, cutting or casting method. In other embodiments, channel  60  can be formed as at least one slot, groove or other recess in the inner wall of conduit  20   c , or as a protruding mesa or berm-like structure on the inner wall of conduit  20   c.    
       FIG. 3  is a diagram of a waste heat recovery system  2  according to an exemplary embodiment in which an oil scraper  122  is provided in conduit  20   b  on the inlet side, or upstream of energy converter  16 . Channel structure  60  collects oil that wets the inner wall of conduit  20   b  from the working fluid vapor flowing from boiler  12  and guides the collected oil to opening  62  of collector  58 . The present embodiment includes a bend  76  portion in conduit  20   b  such as the turn  68  shown in  FIGS. 2A to 2C , but the direction of working fluid flow though the turn would include substantially less rotational flow components compared with flow direction  66 , an end of bend portion  76  downstream from the collector  58  fluidly connects to energy converter  16 , and the other end of bend portion  76  upstream from collector  58  fluidly connects to boiler  12 . In the present embodiment, there would be no significant rotational components in the working fluid where the oil scraper is positioned before the energy converter (i.e., between boiler  12  and energy converter  16 ). To increase collection efficiency, a channel (or channels) to collect oil can be oriented in a conduit relative to a position of the collector inlet, for example, one or more channels in the shape of an inverted “V” with the collector at the apex/vertex or a lip or scraper toward the bottom side of the inner surface of conduit  20   b  to capture oil that has coalesced and is toward the bottom of the tube due to gravity. In other embodiments, collector  58  can be provided in at the bottom inner surface of a horizontal section of conduit  20   b  (not shown). An oil scraper drain line  78  is fluidly connected at one end thereof to collector  58  and at another end thereof to oil reservoir  50 . Oil flow to the reservoir  50  is controlled via a flow control device  80  positioned in oil scraper drain line  78 . 
     Flow control device  80  can be provided with an actuator (not shown in  FIG. 3 ) to control the opening of flow control device  80  to allow oil in collector  58  to flow to oil reservoir  50 . For example, flow control device  80  can be operated based on a signal of a pressure and/or temperature sensor at the inlet of energy converter  16 , temperature of oil as measured by a temperature sensor at the oil reservoir or gearbox  45 , or with detecting the presence of oil in collector  58  or detecting whether an oil level in collector  58  reached or exceeds a predetermined threshold, for example, by an optical or mechanical detector at the collector  58 . Flow control device  80  can be operated at a predetermined interval, for example, based on time spent at a particular engine operating conditions. Flow control device  80  may also simply be an orifice to restrict the flow rate while still providing a return path for oil. When the oil concentration is low in the working fluid, there would be a small flow rate of vapor into the gearbox assembly  44 , but this is acceptable due to gearbox assembly vent line  56  being substantially larger than the flow restriction orifice. If the oil temperature in the gearbox  45  is above a certain threshold, the valve  80  can be controlled not to open because the turbine inlet working fluid temperature would be high. If oil is returned during this point, the oil temperature in the oil tank could exceed a high temperature threshold set for the oil. 
       FIG. 4  is a diagram of a waste heat recovery system according to an exemplary embodiment, where amounts of working fluid/oil mixture output from a pump are controllably diverted to the gear assembly  44  via return line  82  and flow control device  84 . The present embodiment allows oil in the gearbox to be cooled while also performing the function of oil return to the gear assembly  44 . Oil separation occurs because the return of mixed oil and working fluid from line  82  enters the oil tank as a mixture, and then the working fluid boils off to a vapor while the oil stays in liquid form. The vaporized working fluid returns to the working fluid loop via the vapor vent  55  at the top of oil reservoir  50 . The present embodiment allows oil in gear assembly  44  to be cooled while also performing the function of oil return to the gear assembly  44 . As such, a need can be eliminated for a separate oil cooler that is cooled by engine coolant or another coolant. Flow control device  84  can be controlled based on oil temperature in oil reservoir, or it can be a restriction orifice in an application utilizing passive control. 
       FIG. 5  is a diagram of a control system  4  in accordance with an exemplary embodiment that can be implemented to provide a control function with embodiments according to the present disclosure. For example, control system  4  can be utilized to implement the control functions of flow control devices  80  and  84  described above. 
     Control system  4  includes a controller  90 , which is operable to perform one or more sequences of actions by elements of controller  90 , which can be a computer system or other hardware capable of executing programmed instructions, for example, a general purpose computer, special purpose computer, workstation, or other programmable data processing apparatus. Controller  90  is in communication with memory  92 , which can store code related to the programmed instructions carried out by controller  90 . In some embodiments, controller  90  and memory  92  can be an ECM of an engine system or another controller capable communication with an ECM. 
     Controller  90  is configured to receive analog or digital signals from at least one sensor  94 . As described above, for example, a WHR system according to the present disclosure can include one or more temperature, pressure, oil presence, and/or oil level sensors, which are collectively represented in  FIG. 5  as sensor  94 . Based on at least one received signal from sensor  94 , controller  90  determines a control signal and provides the control signal to an actuator  96 , which can be, for example, an actuator associated with flow device  80  or flow device  84  to control an amount the fluid flow through the device. For example, an embodiment a module can monitor engine operation over various power ranges and measure an amount of time the engine is operated within each range. Using this information, controller  90  can use, for example, a look up table to determine whether to open or close flow control device  80  or  84 . 
     It will be recognized that in each of the embodiments, the various control actions could be performed by specialized circuits (e.g., discrete logic gates interconnected to perform a specialized function), by program instructions (software), such as logical blocks, program modules etc. being executed by one or more processors (e.g., one or more microprocessor, a central processing unit (CPU), and/or application specific integrated circuit), or by a combination of both. For example, embodiments of controller  90  can be implemented in hardware, software, firmware, middleware, microcode, or any combination thereof. 
     Programmed instructions can be program code or code segments that perform necessary tasks and can be stored in memory  92 , which is a non-transitory machine-readable medium such as a storage medium or other storage(s). A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. 
     Memory  92  can be considered to be embodied within any tangible form of computer readable carrier, such as solid-state memory, magnetic disk, and optical disk containing an appropriate set of computer instructions, such as program modules, and data structures that would cause a processor to carry out the techniques described herein. A machine-readable medium may include the following: an electrical connection having one or more wires, magnetic disk storage, magnetic cassettes, magnetic tape or other magnetic storage devices, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (e.g., EPROM, EEPROM, or Flash memory), or any other tangible medium capable of storing information. 
     It should be noted that the system of the present disclosure is illustrated and discussed herein as having a controller  90  that performs one or more particular functions. It should be understood that this controller is merely schematically illustrated based on its function for clarity purposes, and does not necessarily represent specific hardware or software. In this regard, these modules, units and other components may be hardware and/or software implemented to substantially perform their particular functions explained herein. The various functions of the different components can be combined or segregated as hardware and/or software modules in any manner, and can be useful separately or in combination. Input/output or I/O devices or user interfaces including but not limited to keyboards, displays, pointing devices, and the like can be coupled to the system either directly or through intervening I/O controllers. Thus, the various aspects of the disclosure may be embodied in many different forms, and all such forms are contemplated to be within the scope of the disclosure. 
     The embodiments described herein can be used in any combination or all combined into one combination to reduce oil concentration in the working fluid to a desired level in a WHR system. For example, while not shown in  FIG. 3 , conduit  20   c  also can include an oil scraper  22  as described above with respect to the embodiment shown in  FIG. 1 . Further, as shown in  FIG. 6 , any of the above embodiments or combinations thereof, represented by WHR system  98  can be coupled with a component of an internal combustion engine  100 , for example, a driveline component such as a crankshaft of engine  100  to supplement the engine&#39;s power. While not shown in  FIG. 6 , additional components can be included in embodiments consistent with the present disclosure, for example, there can be additional gears to provide the power to the driveline of the engine  100 , or a belt drive. In another embodiment, WHR system  98  can be coupled with a component of an internal combustion engine  100  electrically, for example, with an alternator and motor. 
     Although a limited number of exemplary embodiments are described herein, those skilled in the art will readily recognize that there could be variations, changes and modifications to any of these embodiments, or combinations of these embodiments, and those variations would be within the scope of this disclosure. For example, while the embodiments shown in  FIGS. 3 and 4  are described as having actively controlled flow control devices, these embodiments can also be implemented using a passive control configuration and method. For example, flow control can be achieved using thermostats based on temperature of oil or working fluid, or based on a predetermined pressure difference opening a spring loaded valve, or simply by using a restrictive orifice.