Abstract:
A heat exchanger is provided for dissipating heat from a dual turbocharged engine. The heat exchanger has a jacket water cooler, and first and second charge air coolers. The three coolers are arranged in parallel enabling each to operate with a maximum temperature differential, and have fronts that lie in parallel planes. Charge air from a first turbocharger is directly piped to the first charge air cooler, and charge air from the second turbocharger is directly piped to the second charge air cooler. A first baffle is between and upstream of the first charge air cooler and the jacket water cooler. A second baffle is between and upstream of the second charge air cooler and the jacket water cooler. The baffles can direct selected amounts of air to each of the three coolers and prevent radial convective scrubbing. A fuel oil cooler can also be provided.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a split heat exchanger, and particularly to a radiator with maximized entering temperature differentials for both at least one charge air cooler and a jacket water cooler. 
   2. Description of the Related Art 
   It is well known that heat energy contained in one fluid is capable of being transferred to another fluid. Such heat transfer is described in the classical heat transfer equation: Q=UAdT. In this equation, Q represents the heat transfer, U represents a coefficient of heat transfer, A represents the surface area through which the heat can be transferred, and dT represents the change in temperatures between the two mediums. Heat exchangers, and radiators in particular, are designed for a relative high level of transfer of heat energy from one medium to another. One common example is an automobile radiator, in which a coolant fluid passes through an engine to absorb heat energy from the engine. The coolant fluid then is routed through the radiator, where heat is transferred from the coolant fluid to the environment (ambient air). 
   Engineers and designers have incorporated many strategies to increase the amount of heat that a heat exchanger is capable of transferring. One strategy is to attempt to increase the coefficient of heat transfer. Design components, such as the incorporation of louvers, dimples, waves, ridges and other alterations to the fin profiles have been effectively used. While these improvements are quantifiable and generally useful, there are limitations (both practical and theoretical) as to how much the coefficient of heat transfer can be improved. For example, the increased tooling costs may overshadow any savings associated with the increased coefficient. Accordingly, it may take a long time to recapture those costs through efficiency savings, if it is even possible at all. 
   Others have had success in increasing the heat transferring capability of the heat exchanger by increasing the surface area between the two mediums (i.e. increasing the size of the heat exchanger). The increases in surface area can come from a combination of increases in height, width, depth and density of the heat exchanger. Often times, the size requirements for shipping and use dictate maximum dimensions in the height and width dimensions. In such situations, the only remaining variable is the depth of the unit. Accordingly, designers have increased the depth of the heat exchanger in order to increase the surface area. 
   Some heat exchangers are designed for use with engines having turbochargers. It is standard practice to stack two or more radiators in series to cool both a jacket water coolant from the engine and charge air compressed by one or more turbochargers. One configuration has a charge air cooler first, and ajacket water cooler second. Put another way, the charge air cooler is upstream of the jacket water cooler in some configurations, such that air first passes through the charge air cooler and second through the jacket water cooler. There are several drawbacks associated with such standard arrangements. 
   First, having a series stacked heat exchanger has a depth that is equal to the depth of both the jacket water cooler and the charge air cooler. Such a design has a depth that is often greater than that of a single radiator. Any additional depth can increase the system resistance, which is caused when pressure develops between the fan or air mover and the rear side (down stream side) of the jacket water cooler. Pressure can develop by expansion of the air as it gains energy from the heat exchanger, and also by overcoming obstructions to the free flow of the air. The fan therefore needs to have greater horsepower capacity (i.e. higher initial cost plus increased energy consumption during operation) in order to move the intended amount of air through the heat exchanger to overcome the increase in system pressure. 
   A further drawback of such an arrangement is that the ambient air first passes through the charge air cooler, and then passes through the jacket water cooler. The air enters the charge air cooler at ambient temperature (the maximum temperature differential). Heat energy is transferred from the charge air to the environmental air, such that the environmental air leaving the charge air cooler is warmer than the air entering the heat exchanger. The environmental air at an elevated temperature then enters the jacket water cooler where it again receives energy, this time transferred from the engine coolant. Yet, the air entering the jacket water cooler has a temperature above the ambient air temperature. Accordingly, the temperature differential between the coolant and the air is less than maximum, and the energy transfer is less than maximum. Such a design is disadvantageously engineered to be less than optimally efficient. 
   A still further drawback of the stacked system is that for dual turbocharged engines, a manifold is required to route the charge air through the charge air cooler. Several drawbacks can be associated with the use of a manifold. First, it would be undesirable if the return manifold did not evenly distribute the cooled charge air back to both sides of the engine. Second, the charge air can suffer from a pressure loss as it passes through the torturous paths of the manifold and other required piping. Pressure loss of the charge air during routing to and from the charge air cooler reduces the net effect of the turbochargers. Third, the piping and plumbing can add to the overall complexity of the design and manufacturing of the heat exchanger, and the piping and plumbing can be inconvenient to access. 
   It is well know that axial fans have a “dead” spot where the hub rotates due to the lack of air being driven. Non-uniform air flow rates in an axial direction are caused by the “dead” spots. The standard stacked arrangement prohibits mechanical compensation for different air flow rates across the front face of the heat exchanger due to the dead spot. Accordingly, some portions of the heat exchanger are capable at operating at higher efficiency relative the other portions making the overall heat transfer efficiency less than ideal. The zone of the dead spot and associated inefficiency is more profound downstream of the first heat exchanger where stacked arrangements are used. 
   Thus there exists a need for a heat exchanger that solves these and other problems. 
   SUMMARY OF THE INVENTION 
   The present invention is directed toward overcoming one or more of the disadvantages set forth above. The present invention relates to a heat exchanger, and particularly to a radiator with maximized entering temperature differentials for both at least one charge air cooler and a jacket water cooler. 
   According to one aspect of the present invention, a heat exchanger is provided for dissipating heat from a dual turbocharged engine. The heat exchanger can advantageously have a jacket water cooler, a first charge air cooler and a second charge air cooler. The three coolers can be arranged in parallel rather than in series (i.e. stacked arrangement), and each can have a front surface that lie, respectively, in parallel planes. The two charge air coolers are preferably located on opposite sides of the centrally located jacket water cooler. Charge air from the first turbocharger is piped to the first charge air cooler, and charge air from the second turbocharger is piped to the second charge air cooler. A first baffle is at least partially between the first charge air cooler and the jacket water cooler, and extends upstream there from. A second baffle is at least partially between the second charge air cooler and the jacket water cooler, and extends upstream there from. The baffles can direct selected amounts of air to each of the three coolers. The baffles also segregate the coolers to prevent radial convective scrubbing. A fuel oil cooler can also be provided. 
   According to one aspect of the present invention, a maximum entering temperature differential is provided for each cooler. This is accomplished by utilizing the relatively cool ambient air to enter each of the coolers, as opposed to having air first pass through a charge air cooler and then through a jacket water cooler. 
   According to another aspect of the present invention, the overall depth of the heat exchanger is decreased. Advantageously, the system resistance is decreased as a result of the side-by-side geometry of the jacket water cooler and the charge air coolers. Lowering the system resistance and pressure decreases parasitic energy loss via the fan or other components, and increases the efficiency of the heat exchanger. Accordingly, a fan with relatively less horsepower is required to move the necessary amount of air through the heat exchanger. 
   According to a further advantage, the plumbing to each of the charge air coolers is relatively uncomplicated, and comprises distinct cooling circuits. Pressure loss in the charge air circuits is advantageously decreased. All pressure loss in the charge air circuit decreases the net effect of the turbocharger. There is accordingly an incentive to minimize pressure losses in the charge air circuits. Also, the plumbing is more convenient to facilitate ease of assembly and service. 
   According to a still further advantage, selected amounts of axially moving air pushed from the fan can be directed to the jacket water cooler and each of the charge air coolers. This is accomplished with baffles that direct some of the ambient air to the area that conventionally is referred to as the “dead” spot. The baffles accordingly ensure proper flow through each of the coolers. 
   According to a still further advantage yet, the baffles segregate the coolers from each other. One component of the air flow of axial fans moves radially from the fan (the other component is the axially linear movement) and generally parallel to the front of the coolers. The baffles prevent the radial motion of the air from sweeping between coolers and transferring heat between the coolers and passing through the heat exchanger at the point of least resistance. 
   Other advantages, benefits, and features of the present invention will become apparent to those skilled in the art upon reading the detailed description of the invention and studying the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic top view showing external air flow through the heat exchanger of the present invention. 
       FIG. 2  is a schematic top view showing the independent internal cooling circuits of the present invention. 
       FIG. 3  is an exploded front view of the jacket water cooler and the two charge air coolers of a preferred embodiment of the present invention. 
       FIG. 3A  is a front view of the jacket water cooler and the charge air coolers of the present invention showing the side-by-side parallel arrangement. 
       FIG. 4  is an exploded perspective view of a preferred embodiment of the present invention. 
       FIG. 5  is a perspective view of a preferred embodiment of the present invention. 
       FIG. 6  is a rear view of a baffle of the present invention. 
       FIG. 7  is a perspective view of an alternative baffle of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   While the invention will be described in connection with several preferred embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
   The present invention is intended for use with an engine  10  designed for use with two turbochargers  20  and  25 , respectively. Preferably, the engine  10  is a stationary engine. Yet, it is understood that the principals of the present invention could be applied to mobile engines. It is further understood that in a forced convection application, the mechanical air mover or fan may be unnecessary. The engine  10  has a coolant inlet  11  and a coolant outlet  12 . The engine  10  further has a first charge air inlet  13  and a second charge air inlet  14 . The charge air inlets  13  and  14  are preferably on opposed sides of the engine  10 . A fuel inlet  15  is further provided, as well as an excess fuel outlet  16 . 
   Two turbochargers  20  and  25  are used with the engine  10 . Turbocharges  20  and  25  each comprise two chambers. The chambers house a turbine and a compressor, respectively. It is typical for a common shaft to connect the turbine blades and the compressor blades. Exhaust from the engine flowing out of exhaust enters the turbine and expands through the turbine blades. The expansion through the turbine blades cause the blades and shaft to rotate at a high rate of speed. The rotation of the shaft causes the blades in the compressor to likewise rotate. The compressor blades pull ambient air into the compressor to compress the air to relatively high temperature and pressure. 
   An air mover is provided. One preferred air mover is a fan  30 . The fan  30  has a hub  31  and blades  32 . The fan  30  has a central axial axis. The blades  32  can be formed with a selected pitch to achieve an intended linear axial flow of ambient air at the ambient air temperature. A schematic diagram of the air flow is shown in  FIG. 1 . A second component of the air flow from the fan is radial flow. The radial flow is caused by the rotation of the blades and is due to the pitch of the blades. The radial flow typically moves generally perpendicular to the axial flow. The illustrated embodiment utilizes a pusher fan. However, it is understood that a puller fan or any other type of mechanical air convection apparatus such as a blower could alternatively be used without departing from the broad aspects of the present invention. 
   A heat exchanger  35  is provided for dissipating heat from the engine  10 , and cooling the charged air from the turbochargers  20  and  25 . The heat exchanger  35  has a frame  36 . Some other primary components include a jacket water cooler  40 , a first charge air cooler  60 , a second charge air cooler  80 , a fuel oil cooler  100 , a first baffle  120  and a second baffle  130 . A detailed description of each of these components follows. The heat exchanger has a first side bracket  140  with a face  141 , and a second side bracket  150  with face  151 . The first and second brackets  140  and  150  define the outside side walls of the heat exchanger. The front of the heat exchanger  35  is upstream, and the rear of the heat exchanger is downstream. 
   Looking now at  FIGS. 1-5 , it is shown that a jacket water cooler  40  is provided for dissipating heat from the engine coolant fluid. This cooler  40  is preferably a liquid to air heat exchanger. It can be constructed of metal oval tubes and metal flat fins. The tubes can be aligned in a staggered pattern and can be multiple rows deeps. Coolant can flow into and out of the cooler  40  through metal or steel nozzles. It is understood that while the description heretofore represents preferred construction, other embodiments can be used without departing from the broad aspects of the present invention. The jacket water cooler  40  is preferably held in place by the frame  36  of the heat exchanger  35 . The jacket water cooler  40  has a top  41 , a bottom  42 , a first side  43 , a second side  44  and a front  45 . The front  45  of the jacket water cooler  40  preferably is planar and lies in plane  46 . The front  45  is preferably upstream of a back  47 . 
   A coolant inlet  50  is provided, as is a coolant outlet  51 . The inlet is preferably located at or near the top  45  of the jacket water cooler  40 . The outlet  51  is preferably located at or near the bottom of the jacket water cooler  40 . An inlet line  52  is provided. The inlet line  52  has a first end connected to the coolant outlet  12  of the engine, and a second end connected to the coolant inlet  50  of the jacket water cooler. An outlet line  53  is also provided. The outlet line  53  has a first end connected to the coolant inlet  11  of the engine  10 , and a second end connected to the coolant outlet  51  of the jacket water cooler  40 . It is appreciated that, as shown in  FIG. 2 , the jacket water cooler  40 , the inlet line  52  and the outlet line  53  comprise a jacket water cooling circuit. The jacket water cooling circuit  54  is a distinct and independent internal cooling circuit. 
   A first charge air cooler  60  is provided for dissipating heat from the charge air from the first turbocharger  20 . This cooler  60  is preferably an air to air heat exchanger. It can be constructed of metal oval tubes and metal serpentine fins. The tubes can be aligned in a parallel pattern and can be multiple rows deeps. Air can flow into and out of the cooler  60  through aluminum nozzles. It is understood that while the description heretofore represents preferred construction, other embodiments can be used without departing from the broad aspects of the present invention. The first charge air cooler  60  is preferably held in place by the frame  36  of the heat exchanger  35 . The first charge air cooler  60  has a top  61 , a bottom  62 , a first side  63 , a second side  64  and a front  65 . The front  65  of the first charge air cooler  60  preferably is planar and lies in plane  66 . The front  65  is preferably upstream of a back  67 . 
   A charge air inlet  70  is provided, as is a charge air outlet  71 . The inlet is preferably located at or near the top  61  of the first charge air cooler  60 . The outlet  71  is preferably located at or near the bottom of the first charge air cooler  60 . An inlet line  72  is provided. The inlet line  72  has a first end connected to the first turbocharger  20  for receiving charge air, and a second end connected to the charge air inlet  70  of the first charge air cooler. An outlet line  73  is also provided. The outlet line  73  has a first end connected to the first charge air inlet  13  of the engine  10 , and a second end connected to the charge air outlet  71  of the first charge air cooler  60 . It is appreciated that, as shown in  FIG. 2 , first charge air cooler  60 , the inlet line  72  and the outlet line  73  comprise a first charge air cooling circuit  74 . The first charge air cooling circuit  74  is a distinct and independent internal cooling circuit. 
   The first charge air cooler  60  is preferably located near the jacket water cooler  40  in a parallel arrangement. Stated another way, the first charge air cooler  60  and the jacket water cooler  40  are neither upstream nor downstream of each other. This is accomplished as side  64  of the first charge air cooler  60  is near the side  43  of the jacket water cooler  40 . The front surface  45  of the jacket water cooler  40  is also preferably parallel to the front surface  65  of the first charge air cooler  60 , such that both are preferably perpendicular to the axial flow of ambient air driven by the fan. 
   A second charge air cooler  80  is provided for dissipating heat from the charge air from the second turbocharger  25 . This cooler  80  is preferably an air to air heat exchanger. It can be constructed of metal oval tubes and metal serpentine fins. The tubes can be aligned in a parallel pattern and can be multiple rows deeps. Air can flow into and out of the cooler  80  through aluminum nozzles. It is understood that while the description heretofore represents preferred construction, other embodiments can be used without departing from the broad aspects of the present invention. The second charge air cooler  80  is preferably held in place by the frame  36  of the heat exchanger  35 . The second charge air cooler  80  has a top  81 , a bottom  82 , a first side  83 , a second side  84  and a front  85 . The front  85  of the second charge air cooler  80  preferably is planar and lies in plane  86 . The front  85  is preferably upstream of a back  87 . 
   A charge air inlet  90  is provided, as is a charge air outlet  91 . The inlet is preferably located at or near the top  81  of the second charge air cooler  80 . The outlet  91  is preferably located at or near the bottom of the second charge air cooler  80 . An inlet line  92  is provided. The inlet line  92  has a first end connected to the second turbocharger  25  for receiving charge air, and a second end connected to the charge air inlet  90  of the second charge air cooler. An outlet line  93  is also provided. The outlet line  93  has a first end connected to the second charge air inlet  14  of the engine  10 , and a second end connected to the charge air outlet  91  of the second charge air cooler  80 . It is appreciated that, as shown in  FIG. 2 , second charge air cooler  80 , the inlet line  92  and the outlet line  93  comprise a second charge air cooling circuit  94 . The second charge air cooling circuit  94  is a distinct and independent internal cooling circuit. 
   The second charge air cooler  80  is preferably located near the jacket water cooler  40  in a parallel arrangement. The second charge air cooler  80  is preferably on an opposed side of the jacket water cooler  40  from the first charge air cooler  60 . The first charge air cooler  60 , the second charge air cooler  80  and the jacket water cooler  40  are neither upstream nor downstream of each other. This is accomplished as side  83  of the second charge air cooler  80  is near the side  44  of the jacket water cooler  40 . The front surface  45  of the jacket water cooler  40  is also preferably parallel to the front surface  85  of the second charge air cooler  80 , such that both are preferably perpendicular to the axial flow of ambient air driven by the fan. 
   A fuel oil cooler  100  is provided for dissipating heat from the excess fuel from the engine  10 . This cooler  100  is preferably a liquid to air heat exchanger. It can be constructed of metal round tubes and metal flat fins. Fuel can flow into and out of the cooler  100  through metal nozzles. It is understood that while the description heretofore represents preferred construction, other embodiments can be used without departing from the broad aspects of the present invention. The fuel oil cooler  100  is preferably held in place by brackets that are supported by the frame  36  of the heat exchanger  35 , as best shown in  FIG. 3 . The fuel oil cooler  100  has a top  101 , a bottom  102 , a first side  103 , a second side  104  and a front  105 . The front  105  of the fuel oil cooler  100  preferably is planar and lies in plane  106 . The front  105  is preferably upstream of a back  107 . 
   An inlet  110  is provided by the fuel oil cooler  100 , as is an outlet  111 . An inlet line  112  is provided. The inlet line  112  has a first end connected to the excess fuel outlet  16  of the engine  10 , and a second end connected to the fuel oil cooler inlet  110 . An outlet line  113  is also provided. The outlet line  113  has a first end connected to a fuel reservoir, and a second end connected to the outlet  111  of the fuel oil cooler  100 . It is appreciated that, as shown in  FIG. 2 , fuel oil cooler  100 , the inlet line  112  and the outlet line  113  comprise a fuel oil cooler circuit  114 . 
   In the illustrated embodiment, the fuel oil cooler  100  is stacked upstream of the second charge air cooler  80 . The surface area of the front  105  of the fuel oil cooler is much smaller that the surface area of the second charge air cooler  80 , as shown in FIG.  3 A. The front  105  of the fuel oil cooler is preferably parallel to the front  85  of the second charge air cooler  80 . 
   Turning attention now to  FIGS. 1 ,  3 ,  3 A and  6 , a first baffle  120  is illustrated. Baffle  120  is preferably made of metal. The baffle  120  has a top  121  and a bottom  122 . The baffle comprises a first segment, or partition  123 , and a second segment, or face  124 . The face  124  has a leading edge  125 . The leading edge is preferably concave and has an arch  126  or curve. The baffle partition segment  123  and face segment  124  can be rigidly connected or adjustably connected. It is understood that alternative shapes could be used without departing from the broad aspects of the present invention. 
   The partition  123  can be partially between the first charge air cooler  60  and the jacket water cooler  40 . The face  124  extends upstream from between the coolers  60  and  40 . The face  124  is preferably angled towards the bracket  140  and the outside of the heat exchanger such that it is upstream of the first charge air cooler. The face  124  divides the ambient air driven by the fan and directs selected amounts of air to pass through each of the jacket water cooler  40  and the first charge air cooler  60 . In this regard, the air entering at the ambient air temperature independently passes through the jacket water cooler  40  and the fist charge air cooler  60 . The face  124  also prevents radial convective scrubbing, or air that is swept radially from scrubbing across one of the coolers  60  or  40  and heating the other cooler, such as from cooler  60  to cooler  40 . 
   A second baffle  130  is also provided according to the present invention. Baffle  130  is preferably made of metal. The baffle  130  has a top  131  and a bottom  132 . The baffle comprises a first segment, or partition  133 , and a second segment, or face  134 . The face  134  has a leading edge  135 . The leading edge is concave and has an arch  136  or curve. The baffle partition segment  133  and face segment  134  can be rigidly connected or adjustably connected. It is understood that other shapes could be used without departing from the broad aspects of the present invention. 
   The partition  133  is at least partially between the second charge air cooler  80  and the jacket water cooler  40 . The face  134  extends upstream from between the coolers  80  and  40 . The face  134  is preferably angled towards the bracket  150  and the outside of the heat exchanger such that it is upstream of the second charge air cooler. The face  134  divides the ambient air driven by the fan and directs selected amounts of air to pass through each of the jacket water cooler  40  and the second charge air cooler  80 . In this regard, the air entering at the ambient air temperature independently passes through the jacket water cooler  40  and the second charge air cooler  80 . It is understood that a portion of the air passes through the fuel oil cooler  100  before passing through the second charge air cooler  80 . The face  134  also prevents radial convective scrubbing, or air that is swept radially from scrubbing across one of the coolers  80  or  40  and heating the other cooler, such as cooler  80  to cooler  40 . 
   Turning attention now to  FIG. 7 , an alternative baffle  220  is illustrated. Baffle  220  is preferably made of metal. The baffle  220  has a top  221  and a bottom  222 . The baffle comprises a first segment, or partition  223 , and a second segment, or face  224 . The face  224  can be split into a plurality of tabs. In one embodiment, four tabs  225 ,  230 ,  235  and  240  are provided. Tab  225  has a first end  226  and a second end  227 . Tab  230  has a first end  231  and a second end  232 . Tab  235  has a first end  236  and a second end  237 . Tab  240  has a first end  241  and a second end  242 . One or more of the tabs can be selectably moved to any desired angle with respect to the partition  223 . The baffle partition segment  223  and face segment  224  can be rigidly connected or adjustably connected. 
   The partition  223  can be partially between the first charge air cooler and the jacket water cooler. The face  224  extends upstream from between the jacket water cooler and the first charge air cooler. The face  224  is preferably angled towards the bracket and the outside of the heat exchanger such that it is upstream of the first charge air cooler. The face  224  divides the ambient air driven by the fan and directs selected amounts of air to pass through each of the jacket water cooler and the first charge air cooler. In this regard, the fan causes air entering at the ambient air temperature to independently pass through the jacket water cooler and the fist charge air cooler. The face  224  also prevents radial convective scrubbing, or air that is swept radially from scrubbing across one of the coolers and heating the other cooler. 
   It is understood that a second similar shaped baffle (not shown) could be used between and upstream of the second charge air cooler and the jacket water cooler. 
   Looking now at  FIGS. 1 and 2 , it is seen that each of the jacket water cooling circuit  54 , the first charge air circuit  74  and the second charge air circuit  94  take advantage of ambient air at non-elevated ambient air temperature. The baffles  120  and  130  ensure that a desired amount of air pass through each of these coolers, and in particular direct air to the traditional “dead” spot in front of the hub  31  of the fan  30 . The baffles  120  and  130  thermally segregate the coolers by preventing swept air from passing through more than one cooler. In this regard, each molecule of air passes though only one of the jacket water cooler  40 , the first charge air cooler  60  and the second charge air cooler  80  (the external air cooling circuits). 
   The system resistance normally associated with fully stacked systems is decreased by the present invention, as the air passes through only one cooler. Accordingly, the driving potential of the air mover is increased. Further, the baffles ensure that selected amounts of air pass through each cooler and prevent all the driven air from passing through the cooler with the least resistance. 
   It is noteworthy that the first charge air circuit  74  is direct to the first charge air cooler  60  and then to the first engine intake  13 , and the second charge air circuit  94  is direct to the second charge air cooler  80  and to the second engine intake  14 . The separate internal cooling circuits allows for the heat exchanger to operate without complex installation and manifolding. 
   Thus it is apparent that there has been provided, in accordance with the invention, a radiator that fully satisfies the objects, aims and advantages as set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.