Abstract:
The present invention is an exhaust gas recirculation system for a motor vehicle, having a turbocharger unit ( 18 ) which has a turbine ( 20 ) and a compressor ( 36 ), the compressor ( 36 ) having a compressor wheel ( 42 ) which rotates on an axis ( 66 ). There is also a dispersion apparatus ( 56 ) operably associated with a condensation separation apparatus ( 58 ). The condensation separation apparatus ( 58 ) separates moisture from exhaust gas flowing from the turbine ( 20 ), and the dispersion apparatus ( 56 ) reintroduces the moisture into the compressor ( 36 ) in proximity to the compressor wheel axis ( 66 ), preventing erosion of the compressor wheel ( 42 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/762,623, filed Jan. 27, 2006. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to an exhaust gas recirculation (EGR) valve assembly used with a turbocharger unit. More particularly, the reintroduction of EGR condensate into recirculated exhaust gas such that the droplets cannot harm the compressor wheel of the turbocharger unit. 
       BACKGROUND OF THE INVENTION 
       [0003]    Turbocharging units are a commonly used way to increase the power of an engine, both with conventional internal combustion engines, and Diesel engines. Turbochargers are comprised of a turbine, and a compressor. The turbine receives exhaust gas from the exhaust manifold of the engine, and the turbine wheel located inside the turbine rotates, powering a compressor wheel inside the compressor. The compressor forces high-pressure air into the intake manifold of the engine, increasing power output. 
         [0004]    Due to increased environmental concerns, an emphasis has been placed on reducing the amount of exhaust gas emissions of both internal combustion engines and diesel engines. One method that has been used to reduce exhaust gas emissions has been to reintroduce the exhaust gas into the intake manifold of the engine, reducing the amount of exhaust gas released into the atmosphere. This is commonly achieved through the use of an EGR valve. 
         [0005]    Current and future emission requirements for diesel engines in Europe, the U.S., and most foreign markets require engine concepts capable of delivering high EGR-rates at very low vehicle loads/speeds. One way of providing these EGR-rates is by using low pressure EGR. However, exhaust gas can contain a high amount of water vapor, dependent on the humidity of the air and the fuel quantity burned in the combustion chamber of the engine. The path the exhaust gas flows through, also called the EGR path, is comprised of the turbocharger, a particulate filter, an exhaust pipe, an EGR path having an EGR valve, a low-pressure EGR path having a low pressure EGR valve, and a low pressure EGR cooler. While the water vapor passes through the EGR path, at certain driving conditions such as cold ambient temperature, or low engine loads and therefore low exhaust temperatures after a cold start, the water vapor cools down below its dew point temperature and droplets are formed. These droplets of different aerodynamic radii pass through the EGR path, the low-pressure EGR path, the low pressure EGR cooler, and into the intake pipe in front of the rotating compressor wheel, also called the mixing area. 
         [0006]    One major problem caused by the droplets coming into contact with the compressor wheel is that these droplets that are formed can lead to massive droplet erosion on the compressor wheel. One way to keep droplets from hitting the compressor wheel in a critical area is to have the droplets permanently removed from the flow of exhaust gas going into the compressor wheel under all driving conditions. It is very difficult to permanently remove the condensate from the intake side because of the negative pressure drop to atmosphere (pumping would be necessary). Also humidity in the intake air is a positively influencing parameter for in-cylinder NOx reduction. 
         [0007]    Another way to keep droplets from hitting the compressor wheel area is to temporarily separate the condensate from the gas flow, and then re-introduce the liquid condensate into the exhaust gas in an area to avoid corrosion of the blades on the compressor wheel. This is difficult because dispersion of liquid condensate can cause damage to the compressor wheel blades. 
         [0008]    Accordingly, an object of the present invention is to bring the water vapor or condensate from the exhaust gas of the engine into close contact with the compressor wheel in an area of low blade speed to prevent erosion of the compressor wheel. 
       SUMMARY OF THE INVENTION 
       [0009]    One of the ways to avoid erosion on the compressor wheel due to the droplets is to spread the droplets out over the whole cross-sectional area of the inlet pipe in the mixing area. Spreading the droplets is dependent upon the speed and load point, as well as the mass flow of the exhaust gas. The droplets move into the compressor wheel with a certain speed within the pipe. 
         [0010]    The droplets may also be driven to the outer perimeter of the pipe by swirl. The droplets can then hit the compressor wheel over the whole cross-sectional area. The impulse of the droplets in combination with the impulse of the compressor wheel (in which the impulse of the wheel increases with the speed of the wheel) can cause massive damage to the compressor wheel surface area. These problems are usually, but not only, seen in the areas of high impact speed near the outer tips of the compressor wheel blades, where the diameter of the compressor wheel is largest. 
         [0011]    The present invention is an EGR system for a motor vehicle, having a turbocharger unit which has a turbine and a compressor, the compressor having a compressor wheel which rotates on an axis. There is also a dispersion apparatus operably associated with a condensation separation apparatus. The condensation separation apparatus separates moisture from exhaust gas flowing from the turbine, and the dispersion apparatus reintroduces the moisture into the compressor in proximity to the compressor wheel axis, preventing erosion of the compressor wheel. 
         [0012]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0014]      FIG. 1  is a diagram of an engine having a turbocharging unit, according the present invention; 
           [0015]      FIG. 2  is a side view of an assembly according to a first embodiment of the present invention; 
           [0016]      FIG. 3  is a side view of the assembly according to a second embodiment of the present invention; 
           [0017]      FIG. 4  is a side view of the assembly according to a third embodiment of the present invention; 
           [0018]      FIG. 5  is a side view of the assembly according to a fourth embodiment of the present invention; and 
           [0019]      FIG. 6  is a perspective view of the dispersion apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0021]      FIG. 1  is a schematic view of a diesel engine breathing system incorporating the present invention, generally shown at  10 . As will be described herein, such a system has a low pressure EGR loop, generally shown at  12 . Exhaust gas is generated by an engine  14  and exits through an exhaust manifold  16 . The exhaust gas from the exhaust manifold  16  passes through the turbine  20  and is then introduced to a diesel particulate filter (DPF)  22  where the exhaust gas is cleaned of soot material. After going through the DPF  22 , the exhaust gas will then flow to an EGR valve module  24  where the exhaust gas is split between flowing into an exhaust pipe  26 , where the exhaust gas leaves the vehicle, or into a low-pressure EGR loop  12 , where the exhaust gas will be reintroduced back into the engine  14  for combustion. 
         [0022]    The exhaust gas that flows into the low-pressure EGR loop  12  will flow into an EGR path  28 , and will pass through a low pressure EGR cooler  32  that cools the temperature of the exhaust gas prior to re-combustion. The exhaust gas exits the low pressure EGR cooler  32 , passes through a first passageway or low pressure EGR tube  46 , mixes with air in a mixing area and is introduced to a compressor  36 , which pressurizes both exhaust gas and outside air for introduction to the engine  14 . The mixing area has a mixing apparatus  34  that removes condensation from the exhaust gas and reintroduces the condensation at a specific location at the compressor  38 . The mixed intake gas is then passed through a charge air cooler  38  into an intake manifold  40 , which then delivers the mixed intake gas to the engine  14 . 
         [0023]    In a first embodiment of the present invention, shown in  FIG. 2 , the mixing apparatus  34  is shown in greater detail. The mixing apparatus  34  includes, but is not limited to, a condensation separation apparatus  58 , a transporting pipe  52  and a dispersion apparatus  56 . The mixing apparatus  34  can have many configurations which will now be discussed. 
         [0024]    Disposed within the EGR tube  46  is the condensation separation apparatus  58 , which is connected to the second passageway, or transporting pipe  52 . The condensation separation apparatus  58  can be a ring catch, a separator, or a centrifugal groove. The EGR tube  46  is connected to a third passageway, or intake tube  44 , and is the same EGR tube  46  shown in  FIG. 1 . The intake tube  44  is connected to a compressor housing  68 ; inside the compressor housing  68  is a compressor wheel  42 , which is mounted for rotation on a compressor wheel shaft  66 , which forms a compressor wheel axis. The transporting pipe  52  is connected to the dispersion apparatus  56 , which is mounted in front of the compressor wheel  42 , and is connected to either the intake tube  44  or compressor housing  68 . 
         [0025]    In operation, the exhaust gas with droplets  54  flows through the EGR-tube  46  and through the condensation separation apparatus  58 . Air from the atmosphere flows through the intake tube  44  toward the compressor wheel  42 . The condensation separation apparatus  58  removes the droplets or liquid condensate  50  from the exhaust gas with droplets  54 , forming an exhaust gas and air mixture, generally shown at  64 , in a mixing area, generally shown at  48 . The condensate  50  is transported from the condensation separation apparatus  58  through the transporting pipe  52  to the dispersion apparatus  56 . Once the condensate  50  reaches the dispersion apparatus  56 , the condensate  50  is dispersed in an area of low circumferential speed by the dispersion apparatus  56  aligned with the compressor wheel shaft  66 . 
         [0026]    The dispersion apparatus  56  has the purpose to move the condensate  50  onto the blades  70  in a way to prohibit large droplets from again being created in the mass flow of condensate  50 , and the exhaust gas and air mixture  64  onto the compressor wheel  42 . It should be noted that the condensate  50  could also flow through the transporting pipe  52  and drip pressureless onto the compressor wheel  42  in an area of low circumferential speed without the use of a dispersion apparatus  56 . 
         [0027]    Once the condensate  50  reaches the compressor wheel  42 , the condensate  50  is accelerated on the compressor wheel  42  and transformed into a liquid film  60 . 
         [0028]    Because the liquid film  60  is accelerated on the wheel  42 , droplet erosion is prevented because the impact of the condensate  50  hitting the wheel  42  is significantly reduced, if not eliminated. The transporting pipe  52  is designed aerodynamically to not disturb the flow in front of the compressor wheel  42 . Good alignment with the compressor wheel  42  makes a close coupled mounting of the transporting pipe  52  to the compressor wheel  42  necessary. This can be done by using fins  62  right in front of the compressor wheel  42  to connect the transporting pipe  52  to the intake tube  44  in front of the compressor wheel  48  or to the compressor housing  68  in front of the compressor wheel  42 . 
         [0029]    The dispersion apparatus  56  and the condensation separation apparatus  58  can also be mounted in other areas and have the same effect of dispersing the condensate  50  to the blades  70  while not allowing droplets to be reformed in the mass flow of the exhaust gas and air mixture  64  within the compressor wheel  42 . The condensation separation apparatus  58  can take the form of a ring catch, a separator, or a centrifuge. 
         [0030]    Another embodiment is shown in  FIG. 3 . In this embodiment, the condensation separation apparatus  58  is mounted in the intake tube  44 . The condensation separation apparatus  58  performs the same function of removing the condensate  50  from the mixture  64  going to the compressor wheel  42  when mounted in the intake tube  44 , or the EGR tube  46 , as previously disclosed. The condensation separation apparatus  58  can be positioned within the intake to collect condensate  50  from the inside of the tube  44 . In this embodiment, the dispersion apparatus  56  is still aligned with the compressor wheel shaft  66 , and works in the same manner as described in  FIG. 2 . 
         [0031]    Another embodiment of the present invention is shown in  FIG. 4 . In this embodiment, the condensation separation apparatus  58  is located in the intake tube  44 , and the dispersion apparatus  56  is mounted to the compressor housing  68 . The droplets can be kept from hitting the compressor wheel  42  in a critical area by using a dispersion apparatus  56  to bring the condensate  50  to the circumferential area of the compressor housing  68 . The principle of this type of reintroduction is to break down the condensate  50  and then mix the condensate  50  with the mixture  64  near the compressor wheel  42 , such that the condensate  50  does not hit the blades  70 , but becomes a thin wall film  72  that is pulled into the compressor wheel  42 . This principle can be used independently of the condensation separation apparatus  58 . 
         [0032]    Another embodiment of the present is shown in  FIG. 5 . In this embodiment, the condensation separation apparatus  58  is located in the intake tube  44 , and the dispersion apparatus  56  has been eliminated. The embodiment disclosed in  FIG. 5  shows how the condensate  50  is kept from hitting the compressor wheel  42  in a critical area is by using the transporting pipe  52  to bring the condensate  50  to a back plate area of the compressor wheel  42  by passing the condensate  50  around the compressor wheel  42  through the compressor housing  68 . There, the condensate  50  is introduced and cannot harm the blades  70 . 
         [0033]    The dispersion apparatus  56  can take the form of a threaded nut  72  shown in  FIG. 6 , or a threaded cone. The threaded nut  72  has a series of apertures  74  located on an extension  76  for distributing the condensate  50 . As the condensate  50  moves through the transport pipe  52  to the threaded nut  72 , pressure builds inside the threaded nut  72 , forcing the condensate  50  through each of the series of apertures  74 . The threaded nut  72  is rotatably connectable to the compressor wheel shaft  66 . The rotation of the threaded nut  72  contributes the flow of the condensate  50  out of the threaded nut  72 . The threaded nut  72  is just one example of how to disperse the condensate. Many other variations can be used. It is possible for the dispersion apparatus to be a rotating rough surface that the condensate comes into contact with. It is also possible for the dispersion apparatus described herein to be not connected with the compressor wheel. 
         [0034]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.