Abstract:
Improved efficiency is obtained in a rotary machine having a rotary shaft ( 18 ) mounting a compressor wheel ( 20 ) that discharges into a heat exchanger ( 36 ) having a core ( 82 ) with a central opening ( 42 ) in surrounding relation to the shaft ( 18 ). The heat exchanger ( 36 ) includes a coolant tank ( 90 ) on one side of the core ( 82 ) and in fluid communication with the same which serves as one boundary of radially extending space ( 68 ) through which a gas is discharged by a compressor wheel ( 20 ). A deswirling vane structure ( 80 ) causes gas discharged by the compressor wheel ( 22 ) to move radially outward within the space ( 68 ) and is formed of a material of good thermal conductivity and thermally bridged to the tank ( 90 ) to conduct heat thereto to be rejected to coolant in the tank.

Description:
FIELD OF THE INVENTION 
     This invention relates to a heat exchanger used as an inter-cooler in a rotary compressor machine such as a turbocharger or a super-charger for engines. 
     BACKGROUND OF THE INVENTION 
     Combustion air chargers, such as turbochargers or super-chargers, have been employed with engines, particularly internal combustion engines, for many years. In a turbocharger, at least one rotary compressor wheel is driven by the exhaust of the engine. In the case of a supercharger, at least one rotary compressor wheel is driven mechanically, usually by the rotary output of the engine. In either case, a compressor wheel is employed to compress ambient air prior to its admission to the engine to support combustion therein. Because the air is compressed, a given volume thereof will have a greater mole content of oxygen than an otherwise equal of volume of air at ambient pressure. As a consequence, the additional oxygen permits the combustion of a greater quantity of fuel so that for a power plant of a given size, a greater power output may be derived as a result of the charging of the combustion air. 
     Over the years, it has been determined that the efficiency of such combustion air charging devices can be improved through the use of a so-called intercooling system. Because the air is heated as it is compressed, part of the efficiency derived by employing the combustion air charging device in the first place, i.e., the densification of the combustion air charged to the engine, is lost because a volume of hot compressed air will contain less oxygen than an equal volume of cooler compressed air when both are at the same pressure. Thus, for a given pressure, upon admission to an engine for combustion, a cooler combustion air charge will allow the development of more power within the engine than the same charge at the same pressure if at a higher temperature. 
     Consequently, intercoolers as mentioned previously have been employed to cool the air after it exits the combustion air charger (or a stage thereof) and prior to its admission to the engine so as to provide, for any given pressure, a maximum mole content of oxygen. 
     In many cases, the intercooler will be employed as a conventional, rectangular-shaped heat exchanger and is mounted side-by-side or to the front or rear of the usual heat exchanger employed for cooling engine coolant. While this sort of an arrangement adequately handles the cooling of the pressurized combustion air, it may have certain constraints in terms of size and the volume available in an engine compartment as, for example, in a vehicle, that houses both the engine and the various heat exchangers employed for cooling. It also may require extensive hose connections between the turbocharger, the intercooler and the engine combustion air inlet which necessarily require relatively large diameter hoses because of the low density of the combustion air and the consequent large volume thereof. 
     It has therefore been proposed to incorporate the intercooler within the combustion air charger itself to provide a more compact combustion air charging and intercooling system as well as to avoid large, bulky hose connections to the extent possible. The goal here is to incorporate the intercooling heat exchanger within the combustion air charger in such a way that it may be easily serviced, requires a minimum of plumbing connections and does not unduly increase the bulk of the combustion air charger while at the same time maximizing the cooling of the combustion air after compression thereof. 
     The present invention is directed toward the provision of advantageous solutions to these problems in an intercooling heat exchanger that is intended to be located internally within a rotary compressor machine. 
     SUMMARY OF THE INVENTION 
     It is the principal object of the invention to provide a new and improved rotary compressor machine with intercooling for use in cooled, compressed air. More specifically, it is the object of the invention to provide an improved rotary compressor machine with an internal inter-cooler that is more compact than known such systems, that is easily serviced, and/or which requires a minimum of plumbing connections and which maximizes the efficiency of the air cooling process. 
     According to one facet of the invention, an exemplary embodiment thereof achieves one or more of the above objects in a rotary machine that includes a rotatable shaft having at least one compressor wheel thereon and a housing containing the compressor wheel and having an inlet to the compressor wheel and an outlet. A heat exchanger is disposed in the housing and is located between the compressor wheel and the outlet. The heat exchanger includes a core having a gas flow path with a substantial radial extent and a gas inlet in fluid communication with the compressor wheel and a gas outlet in fluid communication with the housing outlet. A coolant flow path is provided in the heat exchanger in heat exchange relation with the gas flow path and has a substantial axial extent. The heat exchanger has a donut-shaped core containing the flow paths, the core being substantially concentric with the shaft. The core is flanked by axially spaced, donut-shaped tanks with one such tank serving as a boundary for compressed air being discharged by the compressor wheel as it moves in a radially outward direction. The invention contemplates that the tank be thermally conductive and that the usual deswirling vanes mounted in this area near the outlet of the compressor wheel be thermally bridged to such tank so that, in addition to providing the usual deswirling function, the vanes further act as fins to which heat of the compressed air may be rejected to ultimately be conducted through the tank to coolant therein to thereby increase the transfer of heat from the compressed gas to the coolant. 
     In a preferred embodiment, the vanes are part of a metallic vane structure which is metallurgically bonded to the tank. 
     In a highly preferred embodiment, the rotary machine is a turbocharger or a supercharger and the heat exchanger serves as an inter-cooler for combustion air. 
     In one embodiment of the invention, the vane structure comprises a plurality of circumferentially spaced vanes bonded to the tank. 
     The invention contemplates that the heat exchanger has a radially outer periphery spaced inwardly of the housing and the core has a gas inlet at the radially outer periphery to receive the discharged gas after the same has passed through the vane structure. 
    
    
     Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings. 
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a somewhat schematic, sectional view of a rotary machine, specifically a turbocharger, made according to the invention; 
     FIG. 2 is an exploded view of a segment of the heat exchanger made according to the invention; 
     FIG. 3 is an exploded view similar to FIG. 2 showing an additional embodiment of the invention; and 
     FIG. 4 is an exploded view similar to FIGS. 2 and 3 showing still a further embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The exemplary embodiments of the invention described herein are specifically disclosed as combustion air chargers such as a turbo-charger in the form of a two stage turbocharger. However, it is to be understood that this description is for exemplification purposes and no restriction to combustion air chargers or to turbochargers or to a number of stages as intended except insofar as stated in the appended claims. For example, the invention may be employed with efficacy in any type of rotary machine having a rotary compressor wheel wherein it is desired to cool the compressed air discharged by the compressor wheel before being employed in some other operation. The invention may be employed with efficacy in single stage turbochargers as well as multiple stage turbochargers and may be employed in single or multiple stage superchargers as well. 
     With the exception of the use of deswirling vanes in connection with a compressor wheel which are thermally bridged to a tank for a heat exchanger, no limitation to a particular type of heat exchanger is intended. However, for details of a heat exchanger construction intended for use in a rotary machine employed as a turbocharger or a supercharger, reference may be had to the copending, commonly assigned application of Meshenky et al, entitled “Internally Mounted Radial Flow Intercooler for a Combustion Air Charger”, filed Sep. 20, 2002, Ser. No. 10/251,537, the entire disclosure of which is herein incorporated by reference. With the foregoing in mind, attention is directed to FIG. 1 wherein the rotary machine of the invention is illustrated as a two stage turbocharger for the purposes of illustrating an exemplary embodiment of the invention. 
     The illustrated embodiment of the invention is seen to include a housing, generally designated  10 , formed of at least two separable sections,  12  and  14  respectively. Journalled within the housing  10  by suitable bearings (not shown) is a rotary shaft  18 . In the illustrated embodiment, the rotary shaft mounts a first compressor wheel  20 , a second compressor wheel  22  and turbine wheel  24  which, in turn, will be located within a housing (not shown). As indicated by an arrow  26 , the turbine wheel  24  is driven by the exhaust from an internal combustion engine to drive the shaft  18 . Spent exhaust is outletted from the turbine wheel  24  as indicated by arrow  28 . 
     The housing  12  includes an ambient air inlet  30  while the housing  14  includes a compressed air outlet, schematically indicated by an arrow  32 . The inlet  30  is to the inlet side of the compressor wheel  20  while the outlet  32  is from a volute, schematically illustrated at  34 , on the outlet side of the compressor wheel  22 . 
     A heat exchanger made according to the invention, generally designated  36 , is contained within the housings  12 ,  14  where the two are joined together as indicated schematically by removable fasteners  38 . The heat exchanger  36  is donut-shaped or ring-shaped and includes a radially outer cylindrical surface  40  which defines an air inlet for the passage of air through the heat exchanger  36 . A radially inner cylindrical surface  42  forms an air outlet for the heat exchanger  36 . 
     The sides of the heat exchanger are provided with a first inlet/outlet header and tank, generally designated  44  on the side of the heat exchanger  36  located within the housing  14  and a redirecting header and tank, generally designated  46 , on the side of the heat exchanger  36  within the housing  12 . A coolant manifold  48  is located within the housing  14  to one side of the volute  34  and radially inward of the radially outer part of the volute  34 . The manifold  48  is divided by an internal web or baffle  50  into a radially inner manifold section  52  and a radially outer manifold section  54 . The system is provided with a coolant inlet schematically illustrated by an arrow  56  which extends to radially inner manifold section  52  and a coolant outlet schematically illustrated by an arrow  58  which extends to the radially outer manifold section  54 . By a construction to be described in greater detail hereinafter, a coolant, such as coolant for the internal combustion engine, enters the turbocharger through the inlet  56  and is passed to the radially inner manifold section from which it flows into the inlet/outlet header and tank  44  at a radially inner part thereof to flow axially through the heat exchanger  36  to the reentrant header and tank  46  where its direction is reversed to flow through the radially outer part of the heat exchanger  36  back to the inlet/outlet header and tank  44 . From the header and tank  44 , the coolant is discharged into the radially outer manifold section  54  to the coolant outlet  58 . This flow of coolant is indicated by a series of arrows  60 ,  62  and  64 . A baffle  65  in the inlet/outlet header and tank  44  maintain separation of the incoming and outgoing coolant flow. 
     Air flow through the turbocharger is as follows. Ambient air enters in the inlet  30  and passes to the inlet side of the compressor wheel  20 . As the compressor wheel  20  is driven by the turbine wheel  24 , the air is compressed and discharged at an elevated pressure on the radially outer periphery of the compressor wheel  20  as indicated by arrows  66 . The compressed air continues to flow radially outwardly through an annular space  68  between the housing  12  and the heat exchanger  36  which is in part defined by the reentrant header and tank  46 , a radial baffle  70  extending radially inwardly from the reentrant header and tank  46  and an axial baffle  72  which extends from the baffle  70  at its radially innermost part to mount on a part of the housing  12  (not shown) in adjacency to the turbine wheel  20 . 
     The radially outer side or periphery  40  of the heat exchanger  36  is spaced radially inwardly from the housings  12  and  14  allowing the air compressed by the turbine wheel  20  to be redirected as indicated by arrows  74  to enter the heat exchanger  36  at the radially outer periphery  40  thereof. The air then passes through the heat exchanger  36  in a radially inward direction and is cooled by the coolant that flows axially through the heat exchanger  36  as mentioned earlier. The cooled, compressed air is then discharged from the heat exchanger  36  as indicated by arrows  76  to the inlet side of the compressor wheel  22  whereat it is further compressed and then discharged into the volute  34  as indicated by arrows  78 . This compressed air is then discharged as compressed combustion air to the internal engine to support combustion therein. If desired, additional cooling stages could be included between the compressor wheel  22  and the engine. Alternatively, as mentioned previously, in a single stage turbocharger, the compressor wheel  22  can be omitted in which case the air being discharged from the radially inner side of periphery  42  of the heat exchanger  36  could be discharged directly into the volute  34 . 
     It will be appreciated that much of the plumbing for both air and coolant is contained within the turbocharger itself, providing a compact assembly and minimizing piping losses. For example, large diameter, external hoses connecting the compressor to an external heat exchanger are completely avoided. 
     As is well known, deswirling vanes are frequently located in an annular array within the space  68  whereat the gas discharged by the compressor wheel  20  is moving generally radially outwardly. Because of the rotary motion of the compressing wheel  20 , a swirling motion is also imparted to the compressed gas and in many applications, it is desirable that the swirling motion be minimized or eliminated and deswirling vanes  80  are provided for this purpose. Turning now to FIGS. 2 and 3, and with specific reference to FIG. 2, the heat exchanger  36  is seen to include a core  82  made up of a plurality of fins  84  through which a plurality of tubes  86  extend to be received in tube slots (not shown) in spaced header plates  88 , only one of which is shown. 
     One header plate  88  forms part of the reentrant header and tank assembly  46  and has a metallic tank  90  sealed thereto about a periphery of the header plate  88  to provide a coolant receiving compartment. A tank  92 , forming part of the inlet/outlet header and tank  44  is abutted and sealed to the other header plate  88  on the side of the core  82  opposite from that shown. The baffle  65  is located on the header plate  88  associated with the inlet/outlet header and tank  44  and is intended to abut the latter to separate two ports  96  and  98  to opposite sides of the manifold  48 . 
     The deswirling vane structure  80  includes a plurality of generally radially extending vanes  102  in closely spaced relation and is thermally bridged to the tank  90 , typically by brazing the vane assembly  80  to the same. The configuration of the vanes  102  may be in any desired form so as to provide the desired flow characteristics and flow path at the radially outer extremity  104  of the vanes  102 . 
     In FIG. 2, the heat exchanger  36  is shown only as a single segment, there being two additional such segments to form the cylindrical heat exchanger. However, the same may be made in one piece if desired as, for example, as shown in the previously identified application of Meshenky et al. 
     FIG. 3 is a view similar to FIG.  2  and common components will not be redescribed and the tubes are not shown for simplicity. 
     In FIG. 3, another construction of the vane assembly  80  is shown. The vane assembly  80  may be in the shape of a convoluted fan  112 , formed by stamping or the like and is likewise thermally bridged to the tank  90  as by brazing or the like. 
     The fan  112  thus defines a plurality of interconnected vanes  113 . 
     In some instances, the vane structure  80  is made up of separate vanes  116  having desired aerodynamic shapes to provide the desired flow pattern. These are shown in the lower portion of FIG.  4  and the individual vanes  116  are in spaced relation and again in thermally bridged to the tank  90 . 
     Specifically, as seen in FIG. 4, the vanes  116  are mounted on or integral with a plate  118  which, in turn is thermally bridged to the tank as by brazing. However, it would also be possible to braze the vanes  116  directly to the tank  90  or even machine the vanes out of the wall  120  of the tank  90  opposite the header plate  88  (not shown in FIG.  4 ). 
     In all cases, the vane assembly  80  are preferably formed of metal for good thermal conductivity and to assure that they may be bonded to the tank  90  so that when the heat exchanger is installed in the rotary machine, the vanes will occupy the space  68  to provide the desired deswirling action. 
     Finally, in multiple stage machines, compressor vanes for a stage subsequent to the first stage may be mounted on the inlet/outlet header and tank  44  if desired, simply by reconfiguring the manifold  48 . 
     Those skilled in the art will appreciate from the foregoing description that heat exchange is enhanced according to the invention in that coolant will be present within the tank  90  during operation of the machine while the vane assembly  80  will be located within the space  68  (FIG. 1) to have the gas flow radially outwardly therethrough and be deswirled thereby. In addition, because of the good thermal conductivity of the metal tank  90  as well as the thermal conductivity of vane assembly  80 , heat from the compressed gas being discharged from the compressor wheel  20  (FIG. 1) will be rejected to the vane assembly  80  to be conducted to the tank  90  and thus to the coolant contained therein. Thus, the vane assembly acts as fins to increase the surface area on the gas side of the heat exchanger  36  to supplement the cooling that occurs within the core  82 . As a result, the compressed gas is cooled to a lower temperature than would otherwise be the case and is more dense when it passes out of the heat exchanger  36  at the radially inner periphery  42  thereof. In the case of a combustion air charger, this means that a given volume of combustion air will contain more oxygen, and thereby provide more oxygen to support combustion within an engine with which the machine is associated. This provides for improved power output of such an engine. In other rotary machines, the increased densification of the gas can reduce pressure losses within the heat exchanger  36  to improve overall cycle efficiency. 
     Thus, through the simple expedient of employing the vane assembly  80  for both deswirling and thermal cooling purposes, improved efficiency is obtained.