Patent Publication Number: US-2009229649-A1

Title: Thermal management for improved engine operation

Description:
This is application claims the benefit of U.S. Provisional Application Ser. No. 61/036,679 filed Mar. 14, 2008. 
    
    
     One or more inventions set forth herein was made under Government Contract No. DE-FC27-04NT42278. The government may have certain rights in one or more inventions described herein. 
    
    
     TECHNICAL FIELD 
     The field to which the disclosure generally relates includes thermal management of engine operations and vehicle systems including thermal management components. 
     BACKGROUND 
     It has been discovered that an engine operates with better efficiency and lower emissions if the engine, coolant, oil, and transmission fluid temperatures each are in an optimum range. Engine coolant heat is typically used to warm the engine oil and transmission fluid and these methods are not covered in this embodiment. 
     SUMMARY OF EXEMPLARY EMBODIMENTS OF THE INVENTION 
     One exemplary embodiment may include a method comprising flowing engine combustion exhaust through a thermoelectric device and flowing engine coolant through the thermoelectric device. 
     Another exemplary embodiment may include a system comprising an engine plumbed to flow combustion exhaust from the engine through a thermoelectric device, and the engine plumbed to flow coolant through the thermoelectric device. 
     Another exemplary embodiment may include a method comprising starting up a combustion engine, determining whether coolant flowing through the combustion engine is above a minimum threshold, and if not, flowing engine coolant from the engine to a thermoelectric device so that heat is exchanged from exhaust gas from the engine flowing through the thermoelectric device to the coolant flowing through the thermoelectric device, and if the coolant flowing through the engine is above a minimum temperature threshold, stopping the flow of coolant through the thermoelectric device and flowing the coolant through a radiator to cool the coolant. 
     Another exemplary embodiment may include a method comprising determining if an engine coolant in a vehicle is below an optimum temperature, and if so, routing the coolant from the engine to the cold side of a thermoelectric generator connected to the exhaust system of the engine to exchange heat from the exhaust gases in the exhaust system to heat the engine coolant, and thereafter returning the coolant to the engine to warm the engine. 
     Other exemplary embodiments of the invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while disclosing exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  illustrates a vehicle system including a thermoelectric device connected to the exhaust system of a combustion engine according to one exemplary embodiment. 
         FIG. 2  is a schematic diagram of a vehicle system for thermal management of engine coolant according to one exemplary embodiment. 
         FIG. 3  is a flowchart illustrating a method of controlling the flow of engine coolant in a vehicle according to one exemplary embodiment. 
         FIG. 4  is a schematic illustration of a system for controlling the flow of engine coolant according to another exemplary embodiment of the invention. 
         FIG. 5  is a schematic illustration of a thermoelectric device operating as an electrical generator according to one exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following description of the embodiment(s) is merely exemplary (illustrative) in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring now to  FIG. 1 , one exemplary embodiment includes a vehicle  10  having an engine  12  and an engine breathing system including an air intake conduit  14  connected to the engine and an exhaust conduit  16  connected to the engine and having an open end to discharge combustion gases to the atmosphere after treatment. The vehicle may also include a thermoelectric device  18 , which may be connected to the exhaust conduit  16 . The thermoelectric device  18  may also be plumbed to a radiator  24  and the engine  12  to flow coolant or cooling fluid selectively to and from the engine  12  and radiator  24 . The thermoelectric device  18  may be constructed and arranged to function as a generator to produce electricity to be used by a load  20 , which may include but is not limited to vehicle lights, fans, pumps, energy storage device, such as, but not limited to, a battery and/or propulsion motor(s) in the case of a hybrid vehicle. The vehicle  10  may also include a power source  22  such as a battery to supply a current to the thermoelectric device  18  allowing the same to be utilized as a heat pump. 
     Referring now to  FIG. 2 , one exemplary embodiment of the invention includes a system including an engine  12  and a first pump  28  connected to the engine  12  to flow coolant through the engine  12  to cool the same. The pump  28  may have a pump inlet  30  associated therewith. A head outlet  33  may be connected to the engine  12  and constructed and arranged to deliver coolant through line  32  to a heater core  34 , which may be used to heat the passenger compartment of the vehicle  10 . Coolant line  36  may be provided from the heater core  34  to the pump inlet  30 . Coolant may also flow through line  38  to the hot side of the radiator  24  and through the radiator  24  where at least one fan  40  is positioned to cool the cooling fluid traveling through the radiator. Cooling fluid may also flow from the head outlet  33  through line  42  to a first valve  44 . If the first valve  44  is open, coolant may flow through the first valve  44  and through line  46  into a second pump  48 . Coolant may flow from the second pump  48  through line  50  to a thermoelectric device  18 , which may be a generator. The coolant may flow over the cold side of the thermoelectric device  18  acting as a heat sink for heat transferred from the exhaust conduit  16  to warm the coolant. The warm coolant may flow through line  52 , through a second valve  54  and either through line  56  back into the engine  12  by way of the pump inlet  30  and pump  28 , or through line  58  into the radiator  24 . Coolant exiting the radiator  24  may travel through line  60  to the first valve  44  and/or through line  62  into the engine  12  by way of a third valve  64 , and the pump inlet  30  and pump  12 . Coolant may also flow from the header outlet  33  through line  66  and into the engine  12  by way of a fourth valve  68 , pump inlet  30  and pump  28 . 
     Optionally a fifth valve  70  may be provided in line  38  to prevent coolant from flowing from the engine  12  back to the radiator  24  as desired. Temperature sensors  72  may be provided throughout the system  26  including, but not limited to, in lines  62 ,  56  and/or  52  to determine whether the coolant is within an optimum temperature range associated with an optimum operating temperature range for the engine  12 , engine oil, and transmission oil, or determine if the coolant is above a minimum threshold temperature as desired. 
     Upon engine startup, coolant flows from the radiator  24  through line  62  and into the engine block  12 . A sensor, for example sensor  72  in line  62  may be utilized to determine whether the coolant is within a predetermined optimum temperature range or above a minimum threshold temperature. If the coolant is within an optimum temperature range or above a minimum threshold, the third valve  64  remains open and the first valve  44  is positioned to allow coolant to flow from the radiator through the second pump  48  and the thermoelectric device  18 . However, if the temperature of the coolant is outside of an optimum temperature range or below a minimum temperature threshold, the third valve  64  may be closed to prevent cold coolant from flowing into the engine. The first valve  44  may be positioned (opened) to allow coolant to flow from the engine through the second pump  48  and across the cold side of the thermoelectric device  18  so that heat is transferred from the engine exhaust to the coolant by way of the thermoelectric device. The warmed coolant then exits the thermoelectric device  18  and flows through line  52  and through the second valve  54 , which may be positioned (opened) to allow coolant to flow through line  56  back into the engine  12  to heat up the engine. If the fifth valve  70  is present, the fifth valve  70  may be closed to prevent coolant from flowing from the header outlet  33  back into the radiator  24 . The fourth valve  68  may be opened, closed, or partially opened to control the amount of coolant flowing from the header outlet  33  back into the engine block  12  and/or through line  42  into the first valve  44  and then back through the second pump  48  and the thermoelectric device  18  to be further heated by the exhaust gases. The sensor  72  in line  56  or at another appropriate location may be monitored to determine when the coolant temperature has reached an optimum temperature range for operation of the engine or when the coolant is above a minimum threshold value. If the coolant reaches a minimum threshold value or is within an optimum temperature range, the first valve  44  may be positioned to allow coolant from the radiator to flow through line  46  to the pump  48 , and the fifth valve  70 , if present, may be opened to cause the coolant to travel through line  38  back into the radiator  24  to be cooled as desired. The third valve  64  may be opened to allow the coolant exiting the cool side of the radiator  24  to return to the engine block  12 . The fourth valve  64  may be closed, opened or partially opened as desired. 
       FIG. 3  is a flowchart illustrating a method according to one exemplary embodiment. As illustrated in  FIG. 3 , a determination may be made as to whether the engine coolant temperature T E  is greater than or equal to an optimum engine coolant temperature T EO  at step  76 . If yes, the thermoelectric generator  18  is operated using a traditional coolant flow path wherein the coolant flows from the radiator, into the engine and then back into the radiator  24  and so that the first valve  44  and second valve  54  in  FIG. 2  are closed (ie., positioned to allow coolant to flow from the radiator through pump  48  to the thermoelectric generator  18  and back to the radiator through valve  54 ). However, if T E  is not greater than or equal to T EO , a determination is made as to whether the thermoelectric generator  18  cold side coolant temperature is less than T E , engine coolant temperature plus a temperature delta, which may typically be 5° C., step  78 . If yes, control the coolant flow rate with pump  48  such that the coolant has more time to be heated by exhaust heat through the thermoelectric generator  18 , (alternately, variable flow valves may be used and controlled to reduce the coolant flow rate through the thermoelectric generator  18 ), step  80 . This increase in T GC  results in a reduced efficiency of the thermoelectric generator during warm-up, but increases the efficiency of the total system by warming the engine faster. If no, a determination may be made as to whether an initial delay time has been exceeded, step  82 . The use of a delay time determination is optional. The delay time may be utilized to avoid pumping a relatively small amount of cold coolant contained in line  52  into the engine  12  while the thermoelectric generator  18  is still warming up. The coolant in line  52  will initially contain cold (ambient temperature) coolant. A delay time for opening the first and second valves  44  and  54  allows for a small volume of coolant to flow into the radiator  24  instead of the engine  12 . Then when warm coolant arrives at the second valve  54 , as may be determined by 1) sensor  72  in line  52  or 2) a computed time delay based on pump  48  flow rate and line  52  volume, the second valve  54  may be operated to allow coolant to flow through line  56  into pump inlet  30 . If the initial delay time has not been exceeded, the thermoelectric generator coolant flow rate is increased while keeping T GC  greater than T E  plus a temperature delta as shown in step  84 . If the initial delay time has been exceeded, the thermoelectric generator coolant flow rate is controlled to achieve T GC  equal to T EO  plus a temperature delta as indicated in step  86 . This flow is maintained until T E  is equal to or greater then T EO , then Valves  44  and  54  are again positioned to flow coolant from the radiator, through the Pump  48  and the thermoelectric generator and returned to the radiator. 
       FIG. 4  illustrates another exemplary embodiment of the invention. The system  26  illustrated in  FIG. 4  is similar to the system of  FIG. 3 . However, in  FIG. 4 , lines  60 ,  42 , the first valve  44 , line  46 , the second pump  48 , and line  50  may be eliminated. This embodiment has the effect of reducing the efficiency of the thermoelectric generator because it increases the temperature of coolant on the cold side of the generator but it does reduce the cost and complexity of the system. Alternatively, line  90  may be provided from the first pump  28  to the thermoelectric device  18 . The second pump  48  may be a variable flow pump to vary the amount of coolant flowing through the thermoelectric device  18  in both designs of  FIGS. 3-4 . 
     The system illustrated in  FIG. 4  may be utilized to warm up the engine  12  at startup by flowing engine coolant through the thermoelectric generator  18  to exchange heat with the exhaust gas and flow the warmed coolant through the second valve  54  back into the engine  12 . When the coolant has reached a predetermined minimum threshold, the second valve  54  may be adjusted to allow the coolant to flow through line  58  into the hot side of the radiator  24  and then back into the engine block by way of line  62 , pump inlet  30  and the first pump  28 . 
     The above description of embodiments of the invention is merely exemplary in nature and, thus, variations thereof are not to be regarded as a departure from the spirit and scope of the invention.