Abstract:
An exhaust manifold cooling jacket has internal passages for the circulation of liquid coolant and encloses an exhaust manifold such that a gap is created between the exhaust manifold and cooling jacket. Flowing coolant through the jacket regulates outer jacket temperature while enabling high intra-manifold exhaust gas temperatures for thorough intra-manifold combustion and improved emissions. A liquid-cooled exhaust system includes a turbocharger disposed between manifold and elbow, with liquid coolant flowing from manifold to elbow through the turbocharger. Another liquid-cooled exhaust manifold contains an internal exhaust combustion catalyst wrapped in an insulating blanket. In some marine applications, seawater or fresh water coolant is discharged into the exhaust gas stream at an attached exhaust elbow.

Description:
TECHNICAL FIELD 
       [0001]    This application is a continuation (and claims the benefit of priority under 35 USC 120) of U.S. application Ser. No. 13/751,891, filed Jan. 28, 2013; which is a continuation of U.S. application Ser. No. 12/791,691, filed Jun. 1, 2010, now U.S. Pat. No. 8,359,843; which is a continuation of U.S. application Ser. No. 11/557,431, filed Nov. 7, 2006, now U.S. Pat. No. 7,726,120; which is a continuation of U.S. application Ser. No. 09/862,973, filed May 22, 2001, now U.S. Pat. No. 7,311,066; which claims priority from U.S. provisional application Ser. No. 60/206,050, filed May 22, 2000. The disclosures of the prior applications are considered part of (and incorporated in) the disclosure of this application. 
         [0002]    This invention relates to cooling engine exhaust manifolds and related components, and more particularly to controlling the temperature of engine exhaust components and the exhaust gasses flowing through them. 
     
    
     BACKGROUND 
       [0003]    The exhaust gasses flowing through an exhaust gas manifold of an internal combustion engine are typically very hot, and the exhaust manifold itself may reach very high surface temperatures. To keep the outer surface temperature of the exhaust manifold down for safety reasons, some exhaust manifolds are water cooled, meaning that they contain inner passages through which cooling water flows during engine operation or that they are placed within jackets with cooling water flowing directly across the outer surface of the manifold. Indeed, there are some regulations requiring that exhaust manifolds be provided with cooling jackets for particular applications, such as for marine vessel inspections. 
       SUMMARY 
       [0004]    In one aspect, the invention features a cooling jacket having internal passages for flowing water or other coolant through the jacket to moderate jacket temperature. The jacket attaches to the engine cylinder head to enclose and cool the exhaust manifold of the engine, thereby moderating the temperature of the exhaust gas flowing through the manifold and blocking the outer surface of the manifold from unwanted contact with nearby objects or personnel. As the coolant flows through internal passages in the manifold rather than through or across the exhaust manifold, the coolant never comes into contact with the manifold itself. Manifold cooling is achieved via radiant and convective heat transfer to the jacket when an air gap is provided between the outer surfaces of the manifold and the inner surfaces of the cooling jacket, or by conduction through an insulating material placed between the manifold and jacket. Among the various aspects of the invention are the cooling jacket so described, engines equipped with such cooling jackets, and methods of cooling engine exhaust manifolds by incorporating such jackets. 
         [0005]    In some embodiments the cooling jacket defines a coolant inlet and a coolant outlet that are both separate from the exhaust stream. In some other cases, particularly applicable to marine engines, for example, coolant enters the jacket through a separate inlet but then joins the exhaust flow as the exhaust leaves the manifold, thereby further reducing exhaust gas temperature. 
         [0006]    In another aspect, the invention features a liquid-cooled turbocharger disposed between a liquid-cooled exhaust manifold and a liquid-cooled exhaust elbow, such that manifold cooling fluid flowing to the elbow flows through and cools the housing containing the turbocharger. Preferably, for marine applications, for instance, the cooling fluid is injected into the exhaust stream downstream of the turbocharger, such as in the elbow. In some cases, the manifold cooling fluid flows through the exhaust manifold itself. In some other cases, the fluid cools the manifold by flowing through a channel within a jacket that surrounds the manifold, as discussed above. 
         [0007]    In some embodiments, the manifold houses an exhaust conversion catalyst. The exhaust conversion catalyst is arranged within the exhaust stream, such that the exhaust flows through the catalyst, and is isolated from the liquid coolant, which flows around the catalyst. Preferably, the flow of liquid coolant joins the flow of exhaust downstream of the catalyst. In some embodiments, an insulating blanket is placed between the catalyst and the manifold housing to help to insulate the hot catalyst from the surrounding housing, thereby promoting exhaust conversion and avoiding excessive external surface temperatures. The blanket can, in some cases, also help to protect fragile catalysts from shock damage. 
         [0008]    In another aspect of the invention, a liquid-cooled exhaust manifold houses an exhaust conversion catalyst arranged within the exhaust stream, such that the exhaust flows through the catalyst, and is isolated from the liquid coolant, which flows around the catalyst. The manifold is adapted to receive and join separate flows of exhaust gas and direct them through the catalyst. The manifold comprises a one-piece housing, preferably of cast metal, forming the internal exhaust flow passages and cavity for receiving the catalyst. 
         [0009]    Some aspects of the invention can provide for the ready modification of engines to comply with exhaust manifold cooling requirements, without having to modify the exhaust manifold to either provide for internal cooling or withstand prolonged surface contact with a desired coolant. Furthermore, the temperature of the exhaust gas within the manifold can be maintained at a higher temperature than with normally cooled manifolds, given a maximum allowable exposed surface temperature, enabling more complete intra-manifold combustion and improving overall emissions. Among other advantages, some aspects of the invention help to maintain high exhaust temperatures, such as to promote exhaust catalytic conversion, for example, without producing undesirably high external surface temperatures. 
         [0010]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0011]      FIGS. 1A and 1B  are front and back perspective views, respectively, of an exhaust manifold cooling jacket. 
           [0012]      FIG. 2  is a side view of the cooling jacket, viewed from the side adjacent the engine. 
           [0013]      FIG. 3  is an end view of the cooling jacket. 
           [0014]      FIGS. 4 and 5  are cross-sectional views, taken along lines  4 - 4  and  5 - 5 , respectively, in  FIG. 2 . 
           [0015]      FIG. 6  is a cross-sectional view, taken along line  6 - 6  in  FIG. 3 . 
           [0016]      FIG. 7  is a perspective view of a mounting plate for the cooling jacket. 
           [0017]      FIGS. 8A and 8B  are front and back perspective views, respectively, of an exhaust elbow. 
           [0018]      FIG. 9  is an end view of the exhaust elbow, as looking toward the cooling jacket. 
           [0019]      FIG. 10  is a side view of the exhaust elbow. 
           [0020]      FIGS. 11 and 12  are cross-sectional views, taken along lines  11 - 11  and  12 - 12 , respectively, in  FIG. 9 . 
           [0021]      FIG. 13  is a cross-sectional view, taken along line  13 - 13  in  FIG. 10 . 
           [0022]      FIG. 14  is a perspective view of a liquid-cooled exhaust manifold sized to house a catalytic conversion element. 
           [0023]      FIGS. 15 and 16  are end and side views, respectively, of the manifold of  FIG. 14 . 
           [0024]      FIGS. 17 and 18  are cross-sectional views, taken along lines  17 - 17  and  18 - 18 , respectively, in  FIG. 16 . 
           [0025]      FIG. 19  is a cross-sectional view, taken along line  19 - 19  in  FIG. 18 . 
           [0026]      FIG. 20  is a top view of a liquid-cooled exhaust system including a manifold, turbocharger, and injection elbow. 
           [0027]      FIG. 21  is an exploded perspective view of the exhaust system of  FIG. 20 . 
       
    
    
       [0028]    Like reference symbols in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0029]    Referring first to  FIGS. 1A and 1B , cooling jacket  20  is sand or investment cast in a shape designed to form an interior cavity  22  sized to fit about an engine exhaust manifold (not shown) when the cooling jacket is mounted against the engine head. In this embodiment, the jacket includes a mounting boss  24  and associated exhaust port  26  through which exhaust gas flows from the manifold to a downstream exhaust elbow (shown in FIGS. 
         [0030]      8 A through  13 ). Accordingly, boss  24  features mounting holes  28  through which fasteners from the exhaust elbow extend into threaded bosses on the exhaust manifold, sandwiching the cooling jacket  20  between the manifold and elbow and sealing the exhaust passage. If desired, the cooling jacket may also be mounted securely to the engine cylinder head by appropriate lugs and fasteners (not shown). 
         [0031]    Referring also to  FIGS. 2-6 , cooling jacket  20  is cast to define an internal cooling passage or cavity  30  in hydraulic communication with a coolant inlet  32 , which is attached to a pressurized coolant source (not shown) for circulating coolant through the cooling jacket. From passage  30 , the coolant exits the cooling jacket through ports  34  in boss  24  and flows into the exhaust elbow, where it is blended with the exhaust gas. Alternatively, a separate coolant exit port (not shown) may be provided for returning the coolant to its source. 
         [0032]    As shown in  FIG. 3 , in this embodiment an air gap  31  is formed between the inner surface of the cooling jacket and the outer surface  33  of the exhaust manifold (shown in dashed outline). Alternatively, an appropriate insulating material, such as glass fiber (not shown), may be packed into this gap and provide insulation against heat conduction between the exhaust manifold and cooling jacket. 
         [0033]    Cooling jacket  20  may be cast of any material suitable to the intended environment. For marine applications employing salt water as coolant, a salt resistant aluminum alloy is appropriate. If the cooling jacket is to be mounted directly against a cast iron engine head, or if very high temperatures are anticipated, cast iron may be more appropriate. If aluminum is used and exiting exhaust gas temperatures are high or the exhaust gas is particularly corrosive to aluminum, an iron sleeve may be provided through exhaust port  26 . 
         [0034]    To completely enclose the exhaust manifold, a backing plate  36  may be employed as shown in  FIG. 3 , and illustrated in  FIG. 7 . The backing plate is made of flat metal stock, with appropriate exhaust ports placed to align with the exhaust ports of the engine cylinder head. Backing plate  36  is positioned as if it were an exhaust manifold gasket, between the cylinder head and manifold, with the manifold fasteners securing the backing plate in place. The outer edges of the backing plate engage the rim of the cooling jacket, such that there is no appreciable convective air flow through the cooling jacket. 
         [0035]    Referring now to  FIGS. 8A and 8B , exhaust elbow  38  is adapted to mount on boss  24  of cooling jacket  20  (see  FIG. 1A ) via an appropriate mounting flange  40 . Exhaust inlet  42  aligns with exhaust port  26  of the cooling jacket ( FIG. 1A ), and appropriately positioned coolant inlets  44  align with the coolant outlet ports  34  of the cooling jacket ( FIG. 1A ), such that both the exhaust gasses and coolant enters exhaust elbow  38  separately. At its downstream end  46 , the exhaust elbow is coupled to the remainder of the exhaust system (not shown) in typical fashion. 
         [0036]    Referring to  FIGS. 9-13 , from mounting flange  40  and inlet  42  the exhaust gas flows straight through the exhaust elbow along a central exhaust passage  49  to an exhaust outlet  48 . The coolant flows through coolant passage  50  to the downstream end  46  of the exhaust elbow, where it exits the exhaust elbow at outlets  52  and joins the flow of exhaust gas. Coolant passage  50  is not completely annular at either end of the exhaust tube, due to the structural ribs required between the inner and outer portions of the exhaust elbow. 
         [0037]    Referring next to  FIGS. 14-16 , liquid-cooled manifold  54  is produced as a one-piece casting and is designed to merge the exhaust flows from three separate combustion cylinders (not shown) entering the manifold through three respective inlets  56 . The merged exhaust flows exit the manifold through exit  58 , after having passed through a catalytic conversion element contained within the manifold (discussed further below). Cooling liquid (e.g., fresh water or sea water) enters the manifold through port  60  and exits through port  62 . 
         [0038]    As shown in  FIGS. 17-19 , the manifold housing defines coolant passages  64  extending about the internal exhaust cavity  66 , for circulating liquid coolant through the manifold to control manifold housing surface temperature. Shown disposed within the housing just upstream of exhaust exit  58  in  FIG. 17  is a catalytic conversion element  68  surrounded by an insulator  70 . Element  68  is a cylindrical, porous material designed to promote combustion of combustible exhaust gasses. Such materials are well known in the art of exhaust system design, and a suitable material is available from Allied Signal as their part number 38972. Element  68  has a reasonable porosity and size, at 600 cells per square inch, 3.0 inches in diameter and 2.6 inches in length, to perform its intended function without creating excessive exhaust back pressure. Insulator  70  is a rolled sheet of vermiculite, having a nominal uncrushed thickness of about 5 millimeters. Together, catalytic conversion element  68  and insulator  70  completely span exhaust exit  58 , such that all exhaust gas entering manifold  54  is forced to flow through element  68  before exiting the manifold. By disposing the conversion catalyst within the manifold itself, relatively close to the exhaust source, the high temperatures developed by secondary combustion are safely contained within a liquid-cooled housing so as to not present any exposed high temperature surfaces. As shown in  FIG. 17 , a major length of catalytic element  68  is substantially surrounded by coolant passage  64 . 
         [0039]    Although not specifically illustrated, it should be understood from the above disclosure that another advantageous arrangement is to house an appropriately sized catalytic conversion element, such as element  68 , within a manifold not adapted to circulate cooling fluid, and then surrounding the manifold with a secondary cooling jacket such as that shown in  FIGS. 1-6 . It should also be understood that manifold  54  may be modified to provide the coolant exit coaxially with the exhaust exit, such that the exiting coolant flows directly into an injection elbow or other downstream exhaust component. 
         [0040]    Referring now to  FIGS. 20 and 21 , liquid-cooled exhaust system  72  includes a liquid-cooled exhaust manifold  74 , a liquid-cooled turbocharger  76 , and a coolant injection elbow  78 . The individual exhaust system components are shown separated in  FIG. 21 . Manifold  74  is configured to receive the exhaust from a bank of six combustion cylinders through exhaust inlets  80 , and a flow of coolant through coolant inlet  82 . From manifold  74 , both the combined exhaust stream and the liquid coolant pass directly into the housing of turbocharger  76  through ports  84  and  86 , respectively. The passed coolant helps to control the surface temperature of turbocharger  76 , which uses kinetic flow energy from the exhaust gas to boost the pressure of intake air for combustion in the associated engine. Turbocharger  76  accepts atmospheric air through intake  88  and supplies pressurized air to the engine via air outlet  90 . From turbocharger  76 , both the exhaust stream and the liquid coolant flow directly into injection elbow  78 , through ports  92  and  94 , respectively. In elbow  78  the coolant is injected into the stream of exhaust to further cool the exhaust. The placement of turbocharger  76  immediately downstream of manifold  74 , before the exhaust stream has experienced substantial flow losses, promotes turbocharging efficiency. In addition, flowing the coolant through the turbocharger helps to maintain desirable external turbocharger housing surface temperatures in systems employing downstream water injection, such as for marine applications. It should be understood from the above disclosure that any of the three components shown in  FIG. 21  may be equipped with an internal catalytic conversion element, such as element  68  of  FIG. 17 , and that manifold  74  may be replaced with a standard manifold without internal coolant channels but rather surrounded by a cooled jacket such as the one shown in  FIGS. 1-6 . 
         [0041]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, a single manifold/jacket assembly may replace the standard exhaust manifold and contain both internal exhaust passages and internal coolant passages, with an internal air space between the coolant passages and exhaust passages such that many of the benefits of the invention are achieved. Because of direct exposure to high temperature exhaust gasses, however, such a combination version would be limited to particular materials, such as cast iron or steel. Accordingly, other embodiments are within the scope of the following claims.