Abstract:
A system for cooling a traction battery includes a battery inlet housing having first and second inlets. A first duct is coupled to the first inlet, and a second duct is coupled to the second inlet. A flow guide vane is disposed within the battery inlet housing adjacent to the first inlet. The flow guide vane is positioned to redirect flow from the first duct to mix with flow from the second duct.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to an inlet plenum for a high voltage battery cooling system. 
       BACKGROUND 
       [0002]    Battery electric vehicles make use of an electric drive motor for propulsion, and hybrid electric vehicles make use of an electric drive motor in conjunction with a conventional internal combustion engine for propulsion. Such vehicles include a battery pack including one or more cells electrically connected together. These cells store energy that may be used to supply electric power to the drive motor. The battery pack may also be referred to as a traction battery or a high voltage battery. The traction battery and associated components may generate substantial amounts of heat. This heat may interfere with proper functioning of the battery pack if not dissipated, and so a cooling system is desirable to maintain satisfactory battery operating temperatures. Such a cooling system must satisfy a variety of design considerations including cooling effectiveness and compact packaging, and minimally affect the performance of other vehicle systems. 
       SUMMARY 
       [0003]    A system for cooling a traction battery includes a battery inlet housing having first and second inlets. A first duct is coupled to the first inlet, and a second duct is coupled to the second inlet. A flow guide vane is disposed within the battery inlet housing adjacent to the first inlet. The flow guide vane is positioned to redirect flow from the first duct to mix with flow from the second duct. 
         [0004]    An embodiment of the traction battery cooling system includes a second flow guide vane disposed adjacent the first flow guide and similarly positioned to redirect flow from the first duct. The flows from the first and second ducts may be asymmetric. In some embodiments, the height of the flow guide vane is less than the height of the battery inlet housing. In an exemplary embodiment, the ratio of flow guide vane height to battery inlet housing height is approximately 3:4. 
         [0005]    An embodiment of the traction battery system further includes a battery pack housing in fluid communication with the battery inlet housing. In some embodiments, a battery pack may be retained within the battery housing. In some such embodiments, the battery pack comprises a plurality of cooling passages to direct air flow through the battery pack. In such embodiments, the flow guide vane is positioned to redirect the flow from the first duct to mix with the flow from the second duct to direct a substantially consistent flow volume among the plurality of cooling passages. In some embodiments, the fraction battery cooling system further includes an exhaust duct in fluid communication with the battery pack housing and an induction fan disposed within the exhaust duct. In some embodiments, the traction battery cooling system further includes a fan control system disposed within the battery pack housing. 
         [0006]    In some embodiments, the first duct opens to a first vehicle C pillar and the second duct opens to a second vehicle C pillar. In other embodiments, the first duct joins the second duct to form a combined duct. The combined duct may open to a duct inlet at a central location aft of a vehicle rear seat. 
         [0007]    An embodiment of a hybrid electric vehicle according to the present disclosure includes a vehicle frame. The vehicle frame has first and second support pillars at an aft cabin position. The hybrid electric vehicle further includes a battery housing assembly with first and second housing inlets and a flow guide vane positioned within the housing assembly proximate the first housing inlet. The hybrid electric vehicle further includes a first duct coupled to the first housing inlet and a second duct coupled to the second housing inlet. The first duct extends through a portion of the first pillar and has a first duct inlet in the first pillar, and the second duct extends through a portion of the second pillar and has a second duct inlet in the second pillar. 
         [0008]    In some embodiments, the flow guide vane is positioned to direct the flow from the first housing inlet to mix smoothly with the flow from the second housing inlet. In some such embodiments, the flow from the first housing inlet is less than the flow from the second housing inlet. In some embodiments, the hybrid electric vehicle further includes a battery pack retained within the battery housing assembly. In such embodiments, the battery pack has a plurality of cooling passages, and the flow guide vane is positioned to direct the flows to mix and direct a balanced flow volume among the plurality of cooling passages. In some embodiments, the vehicle further includes an induction fan in fluid communication with the battery housing assembly to draw flow through the first and second ducts. 
         [0009]    A method for cooling a traction battery of a vehicle includes directing air from a vehicle cabin through first and second inlets of a traction battery housing. The air is directed past at least one guide vane positioned to direct air from the first inlet to mix with air from the second inlet. The amount of air directed through the first inlet may differ from the amount of air directed through the second inlet. The method may additionally include drawing the mixed air across a plurality of traction battery passages. The amount of air drawn across each passage is substantially equal. 
         [0010]    Embodiments according to the present disclosure provide a number of advantages. For example, the present disclosure provides a system for cooling a traction battery in which cabin air is drawn through two inlets and mixed smoothly to ensure cooling flow across all battery cells. In addition, systems and methods according to the present disclosure yield smooth air mixing in a battery housing, thereby reducing noise, vibration, and harshness. The present disclosure provides a system wherein cooling air is drawn from an aft region in a vehicle cabin, such that climate controlled cabin air may be used for cooling without negatively impacting occupant satisfaction with the climate control. 
         [0011]    The above advantages and other advantages and features of the present disclosure will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a diagrammatic representation of a traction battery cooling system. 
           [0013]      FIG. 2  is a diagrammatic representation of a battery pack housing of a traction battery cooling system. 
           [0014]      FIGS. 3 and 4  are schematic representations of traction battery cooling systems including the housing of  FIG. 2 . 
           [0015]      FIG. 5  is a diagrammatic representation of a vehicle including the traction battery cooling system of  FIG. 3 . 
           [0016]      FIG. 6  is a flowchart of a method for cooling a traction battery. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    As those of ordinary skill in the art will understand, various features of the present invention as illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce embodiments of the present disclosure that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. 
         [0018]    Uniform cooling of cells within an automotive battery system may improve battery performance and reduce cooling fan power requirements. As the number of cells in an array increases, however, providing uniform air flow throughout the stack becomes increasingly difficult. This may be especially true when vehicle packaging requirements limit inlet plenum volume, which can promote noticeable pressure differences therein. Such pressure differences may result in significant variations in air velocities around cells at different locations in the stack. Reduced air flow around some cells may result in lower current densities, degraded performance, etc. 
         [0019]    To maintain a consistent cooling effect across a range of operating conditions, it may be undesirable to draw air from the exterior of the vehicle for battery cooling purposes. Temperature variations between cold and hot days across a variety of climates may lead to ambient air having unpredictable and inconsistent cooling capabilities. Consequently, it may be preferable to draw cooling air from the vehicle cabin instead. Cabin climate control systems maintain a more consistent internal temperature, and thus this air may be used as a more predictable coolant. However, if cabin air is to be used for cooling, it should be drawn into the cooler in such a way as to have a minimal effect on the cabin climate control system. A battery cooling system design must thus consider both the cooling effect on the battery and any noticeable effects on the climate control inside the vehicle cabin, in addition to being packaged efficiently within the vehicle. 
         [0020]    Referring now to  FIG. 1 , a diagrammatic view of a housing  10  for a high voltage battery pack including a plurality of battery cells  12  is shown. The battery cells  12  are arrayed in two rows, the cells of each row being equally spaced apart. The battery cells  12  are separated by passages  14  of generally equal size. The housing includes an inlet plenum  16  and an outlet plenum  18 . Inlet plenum  16  includes a first inlet  20  and a second inlet  22 , each inlet in fluid communication with a source of air. Outlet plenum  18  includes an outlet  24 . Outlet plenum  18  tapers from a narrow end to a broad end proximate outlet  24  to develop a more even air flow and pressure profile across the passages  14 . 
         [0021]    Air, represented by the dotted arrows, generally enters inlet plenum  16  through first inlet  20  and second inlet  22 . The air may be propelled or impelled, for example, by a fan or blower [not illustrated]. The air flows through passages  14  and draws heat away from battery cells  12 . The air then exits passages  14  into outlet plenum  18  and is drawn through outlet  24 . A bypass passage [not illustrated] may be provided from the inlet plenum  16  around the first row of battery cells  12  to ensure that the second row of battery cells  12  receives a quantity of non-preheated air. 
         [0022]    This configuration, including a first inlet  20  and a second inlet  22 , generally promotes a more even air flow velocity among the passages  14  relative to a single inlet configuration. However, uneven air flow may still develop if the air flow from inlet  22  does not mix smoothly with air flow from inlet  20 . In such regions, illustrated at numeral  26 , the air velocity may decrease. A passage  28  that is proximate such a low air velocity region may receive insufficient cooling flow to adequately draw heat away from the associated battery cells  12 . This may lead to a buildup of heat in the affected battery cells  12 , which may negatively impact performance. Furthermore, the turbulent flow from the unsmooth mixing may cause noise, vibration, and harshness. 
         [0023]    To ensure adequate cooling among all passages  14 , a speed of the fan or blower may be increased to account for the reduced cooling experienced by the cells  12  proximate low velocity region  26 . Increases in power consumption by a fan associated with increased speed may be undesirable, however. 
         [0024]    Referring now to  FIG. 2 , a diagrammatic representation of housing  30  for a traction battery pack including a plurality of battery cells  32  is shown. The battery cells  32  are separated by passages  34 . The housing includes an inlet plenum  36  and an outlet plenum  38 . Inlet plenum  36  includes a first inlet  40  and a second inlet  42 . Outlet plenum  38  includes an outlet  44 . 
         [0025]    Inlet plenum  36  additionally includes at least one guide vane  46 . In an exemplary embodiment, inlet plenum  36  includes two guide vanes  46 . Inlet plenum  36  has a height a [not illustrated] and guide vane  46  has a height b [not illustrated]. Guide vane height b may be less than or equal to height a. In an exemplary embodiment, the ratio of guide vane height b to inlet plenum height a is approximately 3:4. Such a configuration ensures that air flow may be redirected without incurring a substantial reduction in flow capacity or increase in pressure. As an example, one such configuration increases pressure less than  1  Pascal and decreases airflow less than 0.5 cubic feet per minute. In other embodiments, a different ratio may be preferable for optimum flow characteristics, as may be determined by computational fluid dynamics (CFD) or other design tools. 
         [0026]    Air, represented by the dotted arrows, enters inlet plenum  36  through first inlet  40  and second inlet  42 . The air may be propelled or impelled, for example, by a fan [not illustrated]. The air flows through passages  34  and draws heat away from battery cells  32 . The air then exits passages  34  into outlet plenum  38  and is drawn through outlet  44 . A bypass passage [not illustrated] may be provided from the inlet plenum  36  around the first row of battery cells  32  to ensure that the second row of battery cells  32  receives cooler air. 
         [0027]    Guide vanes  46  are configured to direct air from inlet  42  to smoothly mix with air from inlet  40 . Consequently low velocity regions are reduced or eliminated, and the flow among passages  34  is substantially even. Thus heat is drawn away from battery cells  32  evenly, improving battery performance. In addition, the reduction in turbulence of the mixed flows leads to a reduction in noise, vibration, and harshness. 
         [0028]    The volume rate of air flow from inlet  42  may differ substantially from the volume rate of air flow from inlet  40 . Guide vanes  46  are designed to accommodate such asymmetric flows and ensure smooth flow mixing across a range of operating conditions. 
         [0029]    Referring now to  FIG. 3 , a schematic representation of an embodiment of a traction battery cooling system  48  is shown. High voltage battery cooling system  48  includes a battery housing  50  that is substantially the same as battery housing  30  shown in  FIG. 2 . Battery housing  50  includes a battery array  52 , inlet plenum  54 , outlet plenum  56 , and at least one guide vane  58 . Battery  52  may include a plurality of battery cells [not illustrated] as shown in  FIG. 2 . 
         [0030]    High voltage battery cooling system  48  includes a first duct  60 , a second duct  62 , and a third duct  64 . First duct  60  has a first duct inlet  66 , and connects to a control module housing  68  and to inlet plenum  54 . Second duct  62  has a second duct inlet  70  and connects to inlet plenum  54 . First duct inlet  66  and second duct inlet  70  are in fluid communication with a source of air. Third duct  64  connects to outlet plenum  56  and to an induction fan  72 . 
         [0031]    Control module housing  68  includes battery control system  74 . Battery control system  74  includes components and controllers that monitor and control the battery system. Battery control system  74  may further include components that perform other functions, including but not limited to voltage converters and controls for induction fan  72  and the rest of battery cooling system  48 . Battery control system  74  generates waste heat, which may be drawn away to avoid a negative impact on performance. Control module housing  68  may also include various other heat components, including a battery voltage converter [not illustrated]. These other components may also produce heat which may adversely affect performance. 
         [0032]    Air, represented by the dotted arrows, is drawn by induction fan  72  into first duct  60  through first duct inlet  66  and into second duct  62  through second duct inlet  70 . A portion of the air in duct  60  is diverted into control module housing  68 , and the remainder of the cooling flow in duct  60  is drawn into inlet plenum  54 . In an exemplary embodiment, approximately 60% of the air in duct  60  is diverted into control module housing  68  and 40% of the air in duct  60  is drawn into inlet plenum  54 . Consequently, a greater volume of air may enter inlet plenum  54  from second duct  62  than from first duct  60 . Guide vanes  58  are therefore designed to accommodate and ensure smooth mixing of asymmetric flow volumes from first duct  60  and second duct  62 . 
         [0033]    The air that is drawn into control module housing  68  draws heat away from battery control system  74  and other components retained within battery control module housing  68 . The air is then drawn into third duct  64  and into induction fan  72 . Induction fan  72  is in fluid communication with an air exhaust region, such as an exterior of a vehicle. 
         [0034]    The air that is drawn from first duct  60  into inlet plenum  54  is directed by guide vanes  58  to mix with the air drawn from second duct  62 , in substantially the same fashion as illustrated in  FIG. 2 . The air flows through and draws heat away from battery  52 . The air is then drawn through outlet plenum  56  into third duct  64  and into induction fan  72 . 
         [0035]    Referring now to  FIG. 4 , a schematic representation of an alternative embodiment of a high voltage battery cooling system  76  is shown. In this embodiment, a single duct inlet  78  leads to first duct  60 ′ and second duct  62 ′. Duct inlet  78  may draw air from, for example, a central location behind a rear seat. In one embodiment, duct inlet  78  opens to the cabin side of a dividing panel or package tray separating the vehicle cabin and vehicle trunk. First duct  60 ′ and second duct  62 ′ are in fluid communication with control module housing  68 ′ and/or battery housing  50 ′ in substantially the same manner as described in conjunction with  FIG. 3 . 
         [0036]    Referring now to  FIG. 5 , a diagrammatic representation of a vehicle  80  according to an embodiment of the present disclosure is shown. Vehicle  80  includes a high voltage battery cooling system substantially as illustrated in  FIG. 3 , including first duct  60 ″, first duct inlet  66 ″, and battery housing  50 ″ in fluid communication with duct  60 ″. The high voltage battery cooling system further includes a second duct and second duct inlet not illustrated in this view. Vehicle  80  also includes a vehicle roof [not numbered] and a plurality of pillars supporting the vehicle roof According to convention, the pillars are labeled alphabetically from the front to rear of the vehicle. The A pillar  82  is at the fore of the passenger cabin, the B pillar  84  is mid-cabin, and the C pillar  86  is at the aft of the passenger cabin. 
         [0037]    First duct inlet  66 ″ is located in the passenger cabin proximate C pillar  86 . The second duct inlet is similarly located proximate the C pillar on the opposite side of the vehicle [not shown in this view]. In this fashion, the air flowing into the battery cooling system is cabin air, which is generally maintained at more consistent temperatures than ambient air. In addition, by drawing air from the aft of the cabin, climate control is left generally unaffected, increasing customer satisfaction. Battery housing  50 ″ may be stored beneath the vehicle trunk. 
         [0038]    Referring now to  FIG. 6 , a flowchart of a method is illustrated. Air is drawn through first and second inlets in a vehicle cabin, as illustrated in block  90 . The air volume through the first and second inlets may be unequal, as illustrated in block  92 . Air is then directed from the first inlet past at least one guide vane to mix with air from the second inlet, as illustrated in block  94 . The mixed air is then drawn across the battery passages such that the amount of air through each passage is substantially equal, as illustrated in block  96 . 
         [0039]    As can be seen from the various embodiments, the present disclosure provides a system for cooling a high voltage battery in which cabin air is drawn through two inlets and mixed smoothly to ensure cooling flow across all battery cells. In addition, systems and methods according to the present disclosure yield smooth air mixing in a battery housing—reducing noise, vibration, and harshness. The present disclosure provides a system wherein cooling air is drawn from an aft region in a vehicle cabin, such that climate controlled cabin air may be used for cooling without negatively impacting occupant satisfaction with the climate control. 
         [0040]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.