Abstract:
The invention concerns an exhaust gas cooler employed with a tailpipe of a vehicle exhaust system and a method of cooling exhaust gasses before being emitted from the exhaust system into the atmosphere. The exhaust gas cooler may include a cooler housing having a substantially cylindrical shape with an open forward edge, an open rearward edge, and an internal diameter that is larger than the external diameter of the tailpipe, and a cooler support attached to and supporting the cooler housing such that the rearward edge of the tailpipe is located within the cooler housing between the forward and rearward edges of the cooler housing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to a vehicle exhaust system, and more particularly to a system and method for cooling exhaust gasses before exiting the vehicle exhaust system. 
         [0002]    Recent emissions regulations for vehicles employing diesel engines limit the amount of soot that the vehicles may emit. The soot is produced as a by-product of the combustion of the diesel fuel and is carried out with the vehicle exhaust. Diesel particulate filters (also called traps) added to the exhaust system limit the soot emissions sufficiently to meet the regulations. 
         [0003]    Diesel particulate filters work by collecting the soot while allowing the exhaust gasses to pass through. As the vehicle operates, then, the soot builds up in the filter. This soot needs to be periodically eliminated from the filter in order to assure that the filter does not become clogged. A clogged filter can potentially cause damage to itself or the engine. The soot that builds up in the filter can be removed through a process called regeneration. 
         [0004]    Regeneration is performed by heating the diesel particulate filter to a high temperature so the soot will burn away, thus cleaning out the filter. However, during regeneration, the heat used to cause the regeneration process causes the exhaust gasses to be expelled out of the tailpipe at higher temperatures than is desirable. Thus, it is desirable to cool the high temperature exhaust gasses—especially those that occur during regeneration—before they are expelled from the exhaust system. 
       SUMMARY OF THE INVENTION 
       [0005]    An embodiment contemplates an exhaust gas cooler for use with a tailpipe of a vehicle exhaust system. The exhaust gas cooler comprises a cooler housing having a substantially cylindrical shape with an open forward edge, an open rearward edge, and an inner diameter that is adapted to be larger than an exterior diameter of the tailpipe; and a cooler support attached to the cooler housing and adapted to support the cooler housing such that a rearward edge of the tailpipe is located within the cooler housing between the forward and rearward edges of the cooler housing. 
         [0006]    An embodiment contemplates an exhaust system for a vehicle having an engine. The exhaust system may include a tailpipe having an outlet at a rearward edge and having an external diameter adjacent to the rearward edge; and an exhaust gas cooler including a cooler housing having a substantially cylindrical shape with an open forward edge, an open rearward edge, and an internal diameter that is larger than the external diameter of the tailpipe, and a cooler support attached to and supporting the cooler housing such that the rearward edge of the tailpipe is located within the cooler housing between the forward and rearward edges of the cooler housing. 
         [0007]    An embodiment contemplates a method of cooling exhaust gasses produced by a vehicle engine before the exhaust gasses are discharged from a vehicle exhaust system, the method comprising the steps of: providing an exhaust gas cooler around a rearward edge of a tailpipe such that the exhaust gas cooler includes a cooler housing having a rearward edge and a forward edge, with the rearward edge of the tailpipe being located between the rearward and forward edges of the cooler housing; operating the engine, causing the exhaust gasses to flow from an outlet on the rearward edge of the tailpipe; drawing ambient air into the exhaust gas cooler; mixing the exhaust gasses and the ambient air; and expelling an exhaust gas/ambient air mixture out of the rearward edge of the cooler housing. 
         [0008]    An advantage of an embodiment is that the exhaust gas cooler mixes hot exhaust gasses with cooler air, thus lowering the temperature of the exhaust gasses before they are expelled from the exhaust system. This is particularly advantageous for vehicles having a diesel particulate filter that needs to be regenerated from time to time. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic illustration of a vehicle with a diesel engine, and a portion of an exhaust system for the vehicle. 
           [0010]      FIG. 2  is a schematic side view of an exhaust gas cooler and a portion of a tailpipe, without cooler supports shown. 
           [0011]      FIG. 3  is a schematic end view of the exhaust gas cooler and tailpipe, without cooler supports shown. 
           [0012]      FIG. 4  is a section cut, on an enlarged scale, taken along line  4 - 4  in  FIG. 3 . 
           [0013]      FIG. 5  is a schematic end view of the exhaust gas cooler and tailpipe, without the cross vane assembly shown. 
           [0014]      FIG. 6  is a schematic end view of the cross vane assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  illustrates a vehicle  10  having an engine, which may be a diesel engine  14 , mounted therein. The diesel engine  14  drives a transmission  16 , which, in turn, drives a vehicle driveline  18 , and, ultimately, vehicle wheels. 
         [0016]    An exhaust system  24  receives exhaust gasses  22  from the diesel engine  14 , treats the exhaust gasses  22 , and directs them into the atmosphere away from the vehicle  10 . More specifically, an exhaust pipe  28  connects at an upstream end to conventional exhaust system hardware (not shown), such as, for example, a turbocharger (not shown), that receives exhaust from exhaust manifolds (not shown) on the engine  14 . The exhaust pipe  28  directs the exhaust gases  22  into a diesel oxidation converter  30  (also known as a diesel oxidation catalyst). The diesel oxidation converter  30  treats the exhaust gases  22  in order to reduce the amounts of certain constituents that will be emitted into the atmosphere. Such constituents may be, for example, carbon monoxide (CO) and unburned hydrocarbons (HC). 
         [0017]    A first intermediate pipe  32  connects to the downstream end of the diesel oxidation converter  30  and directs the exhaust gasses  22  into a diesel particulate filter  34  (also called a diesel particulate trap). The diesel particulate filter  34  is basically a filter for collecting (i.e., trapping) soot (also called diesel particulate matter) from the exhaust in order to minimize the amount of soot in the exhaust gasses  22 . Downstream of the diesel particulate filter  34  is a second intermediate pipe  36 . The second intermediate pipe  36  directs the exhaust gasses  22  into a muffler  38 . Alternatively, the exhaust system  24  has no muffler or second intermediate pipe and the diesel particulate filter  34  directs the exhaust gasses  22  directly into a tailpipe (discussed below). The vehicle and its components discussed above are known to those skilled in the art and so will not be discussed or shown in more detail herein. 
         [0018]    The muffler  38  directs the exhaust flow into an inlet  42  of a tailpipe  40 . The tailpipe  40  includes an outlet  44 . Near the outlet  44 , the tailpipe  40  connects to and supports an exhaust gas cooler  50 . The exhaust gas cooler  50  includes an open rearward edge  52 , which extends rearward past the tailpipe  40 . The open rearward edge  52  is where an exhaust gas/ambient air mixture  26  are emitted into the atmosphere away from the vehicle  10 . 
         [0019]      FIGS. 2-6  illustrate the exhaust gas cooler  50 , and its attachment to the tailpipe  40  in more detail. The exhaust gas cooler  50  includes a generally cylindrical cooler housing  54  having an open forward edge  56  and the open rearward edge  52 . The cooler housing  54  has an internal diameter  55  that is substantially larger than an external diameter  48  of the tailpipe  40 . For example, the internal diameter  55  of the cooler housing  54  may be about one-and-one-half to two-and-one-half times the external diameter  48  of the tailpipe  40 . Because of this difference in diameters, there is an opening  64  on the forward edge  56  all of the way around the tailpipe  40 . 
         [0020]    The tailpipe  40  is coaxial with the cooler housing  54 , and has a tailpipe rearward edge  46  that extends past the cooler housing forward edge  56  in order to create some axial overlap. For example, the rearward edge  46  may extend between about one-quarter and one-half of the way into the cooler housing  54  toward the housing rearward edge  52 . 
         [0021]    The cooler housing  54  may be mounted on and aligned with the tailpipe  40  with cooler supports, which are illustrated in this embodiment as threaded fasteners  60  and corresponding nuts  62 . A first set of nuts  62  may be used to press against the tailpipe  40 , while a second and third set of nuts  62  are adjusted on the fasteners  60  to align and support the cooler housing  54  relative to the tailpipe  40 . Alternatively, the cooler supports may be one or more brackets (not shown) attached between the cooler housing  54  and tailpipe  40  to align and support the exhaust gas cooler  50  relative to the tailpipe. The brackets may be secured between the components by welding, with adhesive, or with fasteners. As another alternative, although not considered as desirable for alignment purposes, the exhaust gas cooler  50  may have cooler supports (not shown) mounted to vehicle structure (not shown) to hold the cooler housing  54  at the proper location and orientation relative to the tailpipe  40 . 
         [0022]    The exhaust gas cooler  50  may also include a cross vane assembly  66  that mounts inside the cooler housing  54  adjacent to the rearward edge  46  of the tailpipe  40 . The cross vane assembly  66  may include four vanes  68 . Each vane  68  may have an angled vane blade portion  70  for redirecting flow (discussed below), and an attachment flange  72  for mounting the cross vane assembly  66  to the inside of the cooler housing  54 . The attachment flanges  72  may be secured to the cooler housing  54  by welding. Alternatively, the attachment flanges may be secured by adhesive, interference fit, fasteners (not shown), or other suitable means. 
         [0023]    The operation of the exhaust gas cooler  50 , in view of  FIGS. 1-6 , will now be discussed. When the vehicle engine  14  is running, the exhaust gasses  22  produced by the engine  14  flow through the exhaust pipe  28 , diesel oxidation converter  30 , first intermediate pipe  32 , diesel particulate filer  34  (where particulates are trapped), second intermediate pipe  36 , and muffler  38 . From the muffler  38 , the exhaust gasses  22  flow through the tailpipe  40  and the exhaust gas cooler  50  and out into the atmosphere. 
         [0024]    As the exhaust gasses  22  flow out through the outlet  44  on the rearward edge  46  of the tailpipe  40  and into the cooler  50 , they create a vacuum around the rearward edge  46 . This vacuum causes ambient air  23  to be drawn in through the opening  64  (around the tailpipe  40 ) at the forward edge  56  of the cooler  50 . This ambient air  23 , then, moves through the cooler  50  with the exhaust gasses  22  and exits the cooler  50  at its open rearward edge  52  as the exhaust/air mixture  26 . The ambient air  23  absorbs some of the heat energy of the exhaust gasses  22  as they are mixed, thereby lowering the energy level of the exhaust gasses  22  and raising the energy level of the ambient air  23 . The overall temperature of the exhaust/ambient air mixture  26  exiting the exhaust gas cooler  50 , then, is lower than the exhaust gasses  22  as they exit the tailpipe  40 . The end result is a lower overall temperature of the mixture  26  exiting the vehicle  10  to the atmosphere, distributed through the larger diameter opening of the cooler  50 . 
         [0025]    In addition, the exhaust gas cooler  50  may also contain the cross vane assembly  66 . The cross vane assembly  66  will create somewhat of a swirl flow pattern, which helps to better mix the exhaust gasses  22  with the lower temperature ambient air  23  as they flow through the exhaust gas cooler  50 . This may allow the ambient air  23  to more thoroughly absorb heat energy from the exhaust gasses  22  since they are better mixed, thereby more evenly lowering the temperature of the exhaust gasses  22  and raising the temperature of the ambient air  23 . The effective result is a lower temperature mixture  26  more evenly distributed through the larger diameter opening at the rearward edge  52  of the cooler  50 . 
         [0026]    The exhaust gas cooler  50  is particularly advantageous for the vehicle  10  having the diesel engine  14  and the exhaust system  24  that employs the diesel particulate filter  34 . The regeneration process for the filter  34  can cause the temperature of the exhaust gas  22  to rise significantly over normal operating conditions. Accordingly, the exhaust gas cooler  50 , by mixing the very hot exhaust gasses  22  with the ambient air  23 , will help lower these very high temperatures before exiting the exhaust system  24  of the vehicle  10 . Although the exhaust gas cooler  50  may be most advantageous when employed with a vehicle having a diesel engine, the exhaust gas cooler can be employed with vehicles having different types of engines. 
         [0027]    While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.