Abstract:
An engine is disclosed. The engine has an engine block and a cylinder within the engine block. The engine also has a cylinder head associated with a portion of the engine block and the cylinder. The engine further has a plurality of coolant passages formed within the engine block and the cylinder head, wherein a portion of the plurality of coolant passages is filled with a metal foam.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to an engine cooling system and, more particularly, to an engine coolant system having metal foam. 
       BACKGROUND 
       [0002]    Machines such as, for example, passenger vehicles and generators, include engine components that are exposed to high temperatures during operation. These high temperatures may cause excessive thermal stresses within engine components, which may lead to structural failure of the components. Engine systems utilize heat transfer to reduce engine temperature, helping to prevent this type of failure. For example, engine blocks typically contain internal coolant passages capable of passing coolant throughout the engine structure. As the coolant flows through the engine block, the coolant absorbs heat from the engine components. The heated coolant flows out of the engine and into a heat exchanger (e.g., a radiator), where heat transfers from the coolant to ambient air. The cooled coolant then passes back into the coolant passages of the engine, allowing the cycle of heat transfer to continue. 
         [0003]    This scheme of heat transfer may adversely affect the structural integrity of the engine block. Since the coolant passages create unsupported voids within the engine block, the structural capacity of the engine is reduced. In addition, uneven distribution of temperatures may occur adjacent to coolant passages when an engine is operating. Certain parts of an engine tend to become hotter than other parts. Coolant flowing through hollow passages may not change this uneven distribution of heat into a uniform temperature across the engine. 
         [0004]    U.S. Pat. No. 6,223,702 (the &#39;702 patent) issued to Achenbach et al. on May 1, 2001, discloses a system for cooling an engine. The system described by the &#39;702 patent includes an engine block having open coolant passages. The &#39;702 patent also describes a coolant jacket consisting of a metal foam, having a lower specific weight than that of typical casting materials. 
         [0005]    Although the system of the &#39;702 patent may provide a lightweight coolant jacket composed of metal foam, it fails to provide a technique for increasing the structural integrity of the engine at unsupported voids caused by coolant passages. Also, the system of the &#39;702 patent fails to change the uneven distribution of temperatures in an operating engine into a uniform distribution of temperatures. 
         [0006]    The present disclosure is directed to improvements in the existing technology. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    In accordance with one aspect, the present disclosure is directed toward an engine. The engine includes an engine block and a cylinder within the engine block. The engine also includes a cylinder head associated with a portion of the engine block and the cylinder. The engine further includes a plurality of coolant passages formed within the engine block and the cylinder head, wherein a portion of the plurality of coolant passages is filled with a metal foam. 
         [0008]    According to another aspect, the present disclosure is directed toward a method for cooling an engine. The method includes providing coolant passages through the engine and filling a portion of the coolant passages with a metal foam. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a diagrammatic illustration of an exemplary disclosed engine; and 
           [0010]      FIG. 2  is a cross-section of the engine of  FIG. 1 , taken along line A-A. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]      FIG. 1  illustrates an exemplary disclosed engine  12  that may produce a mechanical power output. Engine  12  may be an internal combustion engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine, or any other type of engine apparent to one skilled in the art. Engine  12  may include an engine block  34  that at least partially defines a plurality of cylinders  21  (only one shown in  FIG. 2 ). Engine  12  may also include a piston  25  (shown in  FIG. 2 ) slidably disposed within each cylinder  21 , and a crankshaft (not shown) that is rotatably supported within engine block  34  by way of a plurality of journal bearings (not shown). A connecting rod (not shown) may connect each piston  25  to the crankshaft so that a sliding motion of pistons  25  within each respective cylinder  21  results in a rotation of the crankshaft. A cylinder head  36  may be attached to a top of engine block  34 , so that a combustion chamber  23  (shown in  FIG. 2 ) may be formed between a bottom of cylinder head  36 , interior walls of cylinder  21 , and a top or crown of piston  25 . Cylinder head  36  may house additional engine components such as, for example, one or more intake valves  35  and one or more exhaust valves  37  (one of each shown in  FIG. 2 ). 
         [0012]    During its operation, engine  12  may produce heat from the combustion of fuel and air within cylinder  21 . To dissipate this heat, engine  12  may include a cooling system  10 . Cooling system  10  may help absorb the heat from engine  12  by directing a coolant through engine  12 , and then dissipating this heat to the surrounding environment via a heat exchanger or radiator  16 . Radiator  16  may include a top tank  18 , a core  22 , and a bottom tank  24 . Top tank  18  may serve to receive the coolant, which may be any suitable coolant known in the art such as, for example, a mixture of water and ethylene glycol (i.e., antifreeze). Top tank  18  may include a filling neck  30  that may provide an opening for coolant to be added to cooling system  10 . Filling neck  30  may include a cap. 
         [0013]    Top tank  18  may be fluidly connected to core  22 . Core  22  may operate to expel heat from cooling system  10  as coolant flows through core  22 . Core  22  may be made from any suitable material known in the art, including aluminum or copper. Core  22  may include numerous flattened tubes (not shown) configured in a parallel arrangement, through which coolant may flow. As the coolant comes into contact with the interior surface of the tubes, heat may be released from the coolant into the tubes and, subsequently, to ambient air or another heat-transferring medium. Each tube may include obstructions that make the coolant flow turbulent, causing more volume of the coolant to touch the interior surface of the tubes and increase the rate of heat transfer. Core  22  may work in conjunction with a fan  38 , which may be driven directly or indirectly by engine  12 . In one embodiment, fan  38  may blow or draw ambient air across core  22 , which may further increase the rate of heat transfer from the coolant flowing through the tubes to the ambient air. 
         [0014]    Core  22  may be fluidly connected to bottom tank  24 . Bottom tank  24  may be fluidly connected to a pump  26  by way of a pipe or hose  28 . Pump  26  may be mounted to engine  12  and driven by engine  12  via a fan belt  32 . Pump  26  may be an impeller type pump including a shaft (not shown) that is rotated by fan belt  32 . The shaft may be connected to an impeller, where fan belt  32  causes both the shaft and impeller to rotate within a housing. The impeller may include curved blades that pressurize and push fluid as the impeller rotates, thereby pumping coolant through cooling system  10 . Cooling system  10  may additionally include a coolant filter  27 , which may be fluidly connected between hose  28  and pump  26 . Coolant filter  27  may include a filter medium, serving to filter out rust and other debris from coolant flow and helping to prevent clogging of the coolant flow through cooling system  10 . 
         [0015]    As shown in  FIG. 2 , cooling system  10  may also include a storage passage  42 , which may fluidly connect pump  26  to coolant passages  39  and may serve to store coolant prior to entering coolant passages  39 . Coolant passages  39  may be located within engine block  34 , adjacent to cylinders  21 , and may serve to allow coolant flow to dissipate heat from cylinders  21 . Cooling system  10  may also include coolant passages  44  that may serve to fluidly connect coolant passage  39  to coolant passages  41 . Coolant passages  41  may be located within cylinder head  36  and may serve to allow coolant flow to dissipate heat from cylinder head  36 . 
         [0016]    Coolant passages  39 ,  41 , and  44 , as well as other coolant passages (not shown) in engine  12 , may contain metal foam  46  (shown in  FIG. 2 ). Metal foam  46  may embody a network of connected ligatures composed of a metal such as, for example, copper, aluminum, silver, gold, nickel, or any other suitable metal known in the art. Metal foam  46  may be formed with an open cell structure or a combination of an open cell and closed cell structure. The percentage of void space in metal foam  46  (i.e., the percentage of space not occupied by metal material) may be modified to adjust properties such as porosity for controlling flow rate and/or metal foam surface area for influencing heat transfer rate. For example, if greater flow rate is desired, the percentage of void space in metal foam  46  may be increased, effectively increasing the porosity of metal foam  46 . As an additional example, if greater heat transfer is desired, the surface area of ligatures may be increased, effectively increasing the rate of heat transfer from metal foam  46  to the passing coolant. In addition to influencing heat transfer qualities and porosity, the metal ligatures of metal foam  46  may also serve as structural members within coolant passages  39 ,  41 , and  44 , increasing the overall structural capacity of engine  12 . 
         [0017]    Metal foam  46  may be formed with a uniform percentage of void space (void space being dependent on the number and size of metal ligatures per unit volume) or alternatively with a gradient of void space. For example, metal foam  46  may be formed with a lower percentage of void space at a radially inner location (i.e., near the centers of coolant passages  39 ,  41 , and  44 ) and/or at a radially outer location (i.e., near the walls of coolant passages  39 ,  41 , and  44 ). Varying void space may effectively control the flow of coolant through passages  39 ,  41 , and  44 . 
         [0018]    Metal foam  46  may be cast within coolant passages  39 ,  41 , and  44  during the manufacturing of engine  12 . It is contemplated that metal foam  46  may be bonded to the walls of coolant passages  39 ,  41 , and  44  using a brazing process and a brazing material. The brazing material may be composed of, for example, silver, copper, tin, magnesium, aluminum-silicon, and/or other suitable materials known in the art. 
         [0019]    Metal foam  46  may be cast either in all or only select locations of coolant passages  39 ,  41 , and  44 , based on the requirements of engine  12 . For example, the heat transfer qualities of metal foam  46  may be concentrated at locations within engine  12  that are susceptible to high temperatures and thermal stresses (i.e. providing metal foam  46  with greater surface area). By increasing heat transfer within coolant passages near parts of engine  12  that are particularly susceptible to heat, metal foam  46  may serve to create a uniform temperature within engine  12 , which may be beneficial to the operation of engine  12 . As another example, the structural capacity of metal foam  46  may be increased at locations within engine  12  that are susceptible to structural failure. By providing metal foam  46  with a greater concentration of ligatures at certain locations, the capacity of structurally vulnerable areas of engine  12  may be selectively reinforced. 
         [0020]    Coolant passages  41  may be fluidly connected to a thermostat assembly  14 , located adjacent to cylinder head  36 . Thermostat assembly  14  may include a thermally sensitive element (not shown) configured to restrict and allow coolant flow based on a temperature of coolant. Thermostat assembly  14  may serve to selectively block the flow of coolant from engine block  34  and cylinder head  36  to or from top tank  18  when the temperature of the engine is too low, and to allow the flow of coolant when the temperature of the engine exceeds a given threshold. Thermostat assembly  14  may be fluidly connected to a hose  20 , allowing coolant from coolant passages  39  to flow to or from top tank  18 . 
       INDUSTRIAL APPLICABILITY 
       [0021]    The disclosed cooling system may help to provide a technique for increasing the structural integrity of the engine at unsupported voids caused by coolant passages. Also, the disclosed cooling system may change the uneven distribution of temperatures in an operating engine into a uniform distribution of temperatures, which may be favorable for engine operation. 
         [0022]    An operator may start engine  12 , actuating fan belt  32  and causing pump  26  and fan  38  to begin operation. Pump  26  may pressurize a flow of chilled coolant into storage passage  42 . Coolant may flow from storage passage  42  into coolant passages  39 ,  41 , and  44  within engine  12 . Engine components, such as cylinder  21  and cylinder head  36 , may be heated by the combustion process of engine  12 . Heat may be dissipated from these engine components to the chilled coolant located in coolant passages  39 ,  41 , and  44 . The rate of heat transfer may be higher within areas of coolant passages  39 ,  41 , and  44  containing metal foam  46 . Additionally, the rate of flow of coolant through metal foam  46  may be altered due to the arrangement of ligatures of metal foam  46 . 
         [0023]    Once the coolant within engine  12  becomes heated, thermostat assembly  14  may open to coolant flow. The heated coolant may then flow into hose  20 . Pump  26  may pump the heated coolant through top tank  18  and into core  22  of radiator  16 . Fan  38  may blow or draw ambient air across core  22 , causing heat to be dissipated from the coolant to the air and effectively reducing the temperature of the coolant. 
         [0024]    Pump  26  may force the cooled coolant into bottom tank  24  and through hose  28 . The chilled coolant may be drawn from hose  28  and into coolant filter  27 , where debris located in the coolant flow may be removed. The chilled coolant may be drawn into pump  26 , completing a loop of flow through cooling system  10 . Pump  26  may again pressurize the chilled coolant into passages  39 ,  41 ,  42 , and  44  to dissipate heat from engine  12 , allowing the cycle of cooling system  10  to continue. 
         [0025]    Metal foam  46  of cooling system  10  may help to provide a technique for increasing the structural integrity of engine  12  at unsupported voids caused by coolant passages  39 ,  41 , and  44 . The ligatures of metal foam  46  may act as structural members within the voids, improving the overall structural integrity of engine  12 . Also, metal foam  46  may be concentrated in areas of engine  12  susceptible to high temperatures, increasing the rate of heat transfer at these locations, which may contribute to an overall uniform temperature distribution within engine  12  that may be favorable for engine operation. 
         [0026]    It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed cooling system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed method and apparatus. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims.