Abstract:
A method and apparatus for measuring effects of various conditions on deposit build up in an exhaust gas recirculation system. The apparatus includes a testing jig having a main branch, a test branch, and a control branch. The test and control branches are connected, at an inlet and outlet, to the main branch. Each branch includes a flow control valve so that fluid flow through the test branch can be equalized with fluid flow through the control branch. A parameter of interest, such as temperature, oil, or humidity, in the test branch is modified, and the jig is connected to an engine exhaust, and the flows are equalized. Pressures and temperatures at various points in the jig are monitored and, after a predetermined period of time or when a pressure drop is sensed, the test is complete and the deposits in the test branch are compared with those in the control branch to determine the effect of the altered parameter.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to exhaust system testing devices and methods and, more particularly, toward methods and devices for testing exhaust gas recirculation systems. 
     2. Description of Related Art 
     In low emission automobiles it is conventional to recirculate a portion of the exhaust back to the intake manifold to be mixed with the incoming air and subsequently returned to the combustion chamber. Such exhaust gas recirculation (EGR) systems work well in reducing some emissions by lowering engine&#39;s maximum combustion temperatures. 
     The prior art has focused on devices for making EGR systems more effective in delivering exhaust gases to the intake manifold, including provision of dedicated valves to control the flow of exhaust gases. Unfortunately, such EGR systems are susceptible to carbon build-up that, over time, reduces their effectiveness. While there exists some theories as to the causes for such carbon build-up, to date there is no effective device for testing different variables to see how they affect the carbon deposition problem. 
     U.S. Pat. No. 5,693,874 to De La Cruz et al. discloses a test apparatus for determining deposit formation characteristics of fuels. The testing method includes testing engine parts in a heated test chamber where different fuels are sprayed on the test parts to determine deposit characteristics. 
     U.S. Pat. No. 6,079,251 discloses a system and method for analyzing deposit formation or exhaust particulate content. U.S. Pat. No. 5,492,005 to Homan et al. teaches a related system and method. 
     Accordingly, there exists a need in the art for a method and system for testing EGR systems to determine the effects of variable conditions on the deposition of carbon. There further exists a need in the art for an EGR system experimental testing and measuring system and method. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward a method and system for determining the effects of variable conditions on the deposition of carbon in EGR systems. 
     In accordance with the present invention, a testing jig is adapted to receive exhaust gas from an engine, and includes a main branch and a plurality of side branches. The plurality of side branches includes at least one test branch and at least one control branch. Each of the plurality of side branches, as well as the main branch, include valves and sensors to permit the flow and conditions in each of the branches to be monitored and controlled. 
     In further accordance with the invention, the main branch extends generally longitudinally while the side branches are somewhat U-shaped. Each of the side branches is connected to the main branch at a first end and at a second end. Between the connections, the main branch includes a main valve that is used to create a restriction to flow. Similarly, each of the side branches includes a valve near its second end that is used to equalize flow through the side branches. 
     In accordance with the method of the present invention, the test branch is modified relative to the control branch to introduce one variable. The variable may be temperature, oil, water, fuel additives, oil and engine treatments, alcohol, other combustibles that may be used in place of or in conjunction with gasoline, a flow restriction, a flow enlargement, or any other desired physical parameter. The main branch is connected to the engine exhaust, and the flow rates through the control tube and the main tube are equalized, and the engine is operated at a predetermined rate. The test may be conducted for a predetermined time period or until a predetermined pressure drop is sensed in the control tube. Thereafter, the deposits or coatings in the test branch and the control branch are analyzed and compared to determine the effect of the variables introduced into the test branch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and further features of the invention will be apparent with reference to the following detailed description and drawings, wherein: 
     FIG. 1 schematically illustrates a testing system according to the present invention; 
     FIG. 2 schematically illustrates a first testing jig according to the present invention; 
     FIG. 3 schematically illustrates a second testing jig according to the present invention; 
     FIG. 4 schematically illustrates a third testing jig according to the present invention; and, 
     FIG. 5 is an end elevational view of the third testing jig shown in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, a testing system according to the present invention is shown. The testing system includes a testing jig  10  that is connected to an exhaust  12  of an automobile engine  14 . The engine exhaust  14  includes a catalytic converter  16  that preferably is disposed between the engine  14  and the testing jig  10 . However, it is noted that in some circumstances it may be desirable to remove the catalytic converter  16 . The testing jig  10  is connected to a downstream exhaust assembly  15  via an exhaust pipe  17 . The engine  14  and testing jig  10  are preferably disposed in an environmentally controlled room  18  and the engine  14  is mounted to a dynometer  20 , which is well known in the art. The environmentally controlled room  18  permits the engine  14  and testing jig  10  to be operated at a constant temperature in a consistent atmosphere, and will remove random variables from the testing procedure. 
     The testing jig  10  according to a first preferred embodiment is schematically shown in FIG.  2  and includes a main branch  22 , a test branch  24 , and a control branch  26 . The main branch  22  is preferably formed from a material that resists deposits from oxidation, such as 18 CrCb alloy steel, so as to provide a stable platform for several testing procedures. The main branch  22  extends generally longitudinally and defines an inlet section  22   a , an outlet section  22   b , and a main section  22   c . The inlet section  22   a  is connected to the main section  22   c  by a first fitting  28 , while the main section  22   c  is connected to the outlet section  22   b  by a second fitting  30 . The first and second fittings  28 ,  30  also serve to connect the main branch  22  to the test branch  24  and the control branch  26 , as will be described more fully hereinafter. 
     The inlet and outlet sections  22   a ,  22   b  include flange-type fittings  32 ,  34  to facilitate their securement to other portions of the system. For example, the flange-type fitting  32  at the inlet section  22   a  facilitates attachment to an outlet pipe of the catalytic converter  16 , while the flange-type fitting  34  at the outlet section  22   b  facilitates attachment to the downstream exhaust pipe  17 . Further, each of the inlet and outlet sections  22   a ,  22   b  includes one or more pressure sensors and temperature sensors to facilitate determination and monitoring of these parameters by a controller (not shown). 
     The main section  22   c  of the main branch  22  includes a first valve  36 , which is a relatively coarse flow control valve, to regulate fluid flow through the main branch  22 . Pressure and temperature sensors are also provided on each side of the first valve  36  in the main branch  22 , and permit monitoring of the pressure and temperature within the main section  22   c  of the main branch  22 . 
     The test branch  24  includes an inlet end  24   a , an outlet end  24   b , and a second valve  38  adjacent the outlet end  24   b . The inlet and outlet ends  24   a ,  24   b  include flange-type fittings  40 ,  42  to facilitate removable attachment to the first and second fittings  28 ,  30 . Pressure and temperature sensors are provided in the test branch  24  to monitor these parameters during a testing procedure. The second valve  38 , which is a relatively more precise valve than the first valve  36 , is provided to fine-tune flow through the test branch  24 , as will be apparent from the following discussion. 
     The control branch  26  includes an inlet end  26   a , an outlet end  26   b , and a third valve  44  adjacent the outlet end  26   b . The inlet and outlet ends  26   a ,  26   b  include flange-type fittings  46 ,  48  to facilitate removable attachment to the first and second fittings  28 ,  30 . The third valve  44  is essentially identical to the second valve  38  and is provided to fine-tune flow through the control branch  26 , as will be apparent from the following discussion. Pressure and temperature sensors are also provided in the control branch  26  to monitor these parameters during the testing procedure. 
     While the testing branch  24  as described hereinbefore is substantially identical to the control branch  26 , a physical condition or parameter of the test branch  24  is modified (or introduced) prior to the testing procedure to determine the effects the modified physical parameter has on deposition or build up within the test branch  24 . Such modified physical conditions or parameters may include temperature, oil or water, fuel additives, oil and engine treatments, alcohol, other combustibles that may be used in place of or in conjunction with gasoline, a flow restriction or enlargement, or any other physical variable of interest introduced into the test branch or applied to the test branch. 
     The testing jig  10  is attached to the engine  14  as shown in FIG. 1. A single parameter or variable, or a combination of plural variables, is altered or introduced into the test branch  24 , and then the engine  14  is started. Since the control branch  26  is geometrically and dimensionally identical to the test branch  24 , it may be considered apparent that the flow rate through the test branch  24  will be identical to the flow rate through the control branch  26 . Preferably, however, the first, second and third valves  36 ,  38 ,  44  are adjusted to assure that the flow rate through the control branch  26  is the same as the flow rate through the test branch  24 . 
     The first valve  36  is used to establish a restriction in the test jig  10  and a base flow rate through the test and control branches  24 ,  26 , while the second and third valves  38 ,  44  are used to fine tune the flows through the test and control branches  24 ,  26 . The flow rate may be detected by a suitable sensor or may be determined by other known methods, such as the pressure method, mass flow, or any other method that provides suitable results. 
     The testing procedure continues until a predetermined drop in flow rate is detected in the test branch  24  or the control branch  26 , or until a predetermined test time has elapsed. The predetermined test time may be, for example, one month of continuous operation. Following the testing procedure, the deposits in the test branch  24  and the control branch  26  are analyzed and compared to determine the effect the modified parameter had on the deposition or build up of coatings on the test branch as compared to the deposits formed in the control branch. 
     With reference to FIG. 3, a second embodiment of the testing jig  10 ′ is shown to include a main branch  50 , first, second, and third test branches  52 ,  54 ,  56 , and a control branch  58 . As in the first embodiment, the main branch  50  is preferably formed from a material that resists deposits from oxidation, such as 18 CrCb alloy steel, so as to provide a stable platform for several testing procedures. The main branch  50  includes flange-type fittings at each end to permit securing of the testing jig to the engine exhaust and a downstream exhaust pipe (FIG.  1 ). 
     Four inlet pipe sections  52   a ,  54   a ,  56   a ,  58   a  and four outlet pipe sections  52   b ,  54   b ,  56   b ,  58   b  are fluidly connected to the main branch  50 , while a first valve  60  is disposed in the main branch  50  relatively between the inlet pipe sections and outlet pipe sections, as illustrated. Each inlet and outlet pipe section includes a flange-type fitting to which flange-type fittings of an associated test section  52   c ,  54   c ,  56   c  or control section  58   c  is connected. Accordingly, each test and control branch  52 ,  54 ,  56 ,  58  includes an inlet pipe section  52   a ,  54   a ,  56   a ,  58   a , a test/control section  52   c ,  54   c ,  56   c ,  58   c , and an outlet pipe section  52   b ,  54   b ,  56   b ,  58   b . As will be appreciated, providing flange-type connections between the inlet pipe sections, outlet pipe sections, and test/control section permits interchangeability and compatibility, and facilitates rapid and simplified installation of test/control sections. The inlet and outlet pipe sections  52   a ,  54   a ,  56   a ,  58   a ;  52   b ,  54   b ,  56   b ,  58   b  also include temperature and pressure sensor fittings adjacent the flange-type fittings to permit determination of these conditions during the testing procedure. Each of the outlet pipe sections  52   b ,  54   b ,  56   b ,  58   b  has a fine flow control valve  52   d ,  54   d ,  56   d ,  58   d  disposed therein to regulate fluid flow through the associated test or control branch. 
     As in the first embodiment, the first valve  60  is a coarse flow control valve and is used to establish a flow restriction in the test jig  10 ′ and a base flow rate through the test branches  52 ,  54 ,  56  and the control branch  58 . The fine flow control valves  52   d ,  54   d ,  56   d ,  58   d  are used to fine-tune and match the flow through the test and control branches. 
     Accordingly, in the second embodiment, the test and control sections  52   c ,  54   c ,  56   c ,  58   c  may be manufactured without provision of any special sensor or valve arrangements, reducing the costs associated therewith. Moreover, at least some of the test sections  52   c ,  54   c ,  56   c  may be specially designed to accentuate the parameter being tested. For example, a test section designed to test the effects of temperature may include heating or cooling elements on its exterior surface, as described more fully hereinafter with reference to the third embodiment of the present invention. Moreover, a test section intended to test the effects of fluid substances (i.e., oil, water, fuel additives, oil and engine treatments, alcohol, other combustibles that may be used in place of or in conjunction with gasoline) may be pre-loaded with such substances, or may have metered amounts of such substances introduced therein via suitable ports (not shown) throughout the test procedure. Finally, providing multiple test branches permits several different parameters to be tested in one testing procedure, thereby speeding the collection of comparative data. 
     FIGS. 4 and 5 illustrate a third preferred embodiment of the testing jig  10 ″ according to the present invention. The third testing jig  10 ″ includes a main branch  70 , first, second, and third test branches  72 ,  74 ,  76 , and a control branch  78 . The main branch  70  is preferably formed from a material that resists deposits from oxidation, such as 18 CrCb alloy steel, so as to provide a stable platform for several testing procedures. The main branch  70  includes flange-type fittings at each end to permit securing of the testing jig  10 ″ to the engine exhaust and a downstream exhaust pipe (FIG.  1 ). Moreover, the main branch  70  includes a series of temperature sensors and pressure sensors to determine these parameters at multiple locations during each testing procedure. 
     Four inlet pipe sections  72   a ,  74   a ,  76   a ,  78   a  and four outlet pipe sections  72   b ,  74   b ,  76   b ,  78   b  are connected to the main branch  70 , while a first valve  80  is disposed in the main branch  70  relatively between the inlet pipe sections and outlet pipe sections, as illustrated. Each inlet and outlet pipe section  72   a ,  74   a ,  76   a ,  78   a ;  72   b ,  74   b ,  76   b ,  78   b  includes a flange-type fitting to which associated flange-type fittings of an associated inlet or outlet bend section  72   a ′,  74   a ′,  76   a ′,  78   a ′;  72   b ′,  74   b ′,  76   b ′,  78   b ′ are secured. A test section  72   c ,  74   c ,  76   c  or control section  78   c  is secured between an associated inlet and outlet bend section  72   a ′,  74   a ′,  76   a ′,  78   a ′;  72   b ′,  74   b ′,  76   b ′,  78   b ′, as illustrated. Accordingly, each test or control branch  72 ,  74 ,  76 ,  78  includes an inlet pipe section  72   a ,  74   a ,  76   a ,  78   a , an inlet bend section  72   a ′,  74   a ′,  76   a ′,  78   a ′, a test/control section  72   c ,  74   c ,  76   c ,  78   c , an outlet bend section  72   b ′,  74   b ′,  76   b ′,  78   b ′, and an outlet pipe section  72   b ,  74   b ,  76   b ,  78   b.    
     The flange-type connections between each section of the test and control branches permits interchangeability and compatibility, and facilitates rapid and simplified installation of the test and control sections. The inlet and outlet pipe sections  72   a ′,  74   a ′,  76   a ′,  78   a ′;  72   b ′,  74   b ′,  76   b ′,  78   b ′ also include temperature and pressure sensor fittings adjacent the flange-type fittings to permit determination of these conditions during the testing procedures. Moreover, each of the outlet pipe sections  72   b ′,  74   b ′,  76   b ′,  78   b ′ has a fine flow control valve  72   d ,  74   d ,  76   d ,  78   d  disposed therein to regulate fluid flow through the associated test or control branch  72 ,  74 ,  76 ,  78 . 
     As in the first and second embodiments, the first valve  80  is a coarse flow control valve and is used to establish a flow restriction in the test jig  10 ″ and a base flow rate through the test branches  72 ,  74 ,  76  and the control branch  78 . The fine flow control valves  72   d ,  74   d ,  76   d ,  78   d  are used to fine-tune and match the flow through the test and control branches. 
     The control pipe section  78   c  consists of a straight section of pipe interconnecting the associated inlet and outlet bend sections  78   a ′,  78   b ′. Each test pipe section  72   c ,  74   c ,  76   c  includes an inner pipe section  82 ,  84 ,  86 , essentially identical in length and diameter to the control pipe section  78   c , and a surrounding or outer pipe section  92 ,  94 ,  96 . The outer pipe section  92 ,  94 ,  96  surrounds the inner pipe section  82 ,  84 ,  86  and has a fluid inlet  92   a ,  94   a ,  96   a  at one end and a fluid outlet  92   b ,  94   b ,  96   b  at the opposite end. Cooling or heating fluid flows through the outer pipe section  92 ,  94 ,  96  from the inlet to the outlet and over the inner pipe section  82 ,  84 ,  86  and serves to cool or heat the inner pipe section. Accordingly, the outer pipe section serves as a heat exchanger to modify the temperature of the inner pipe section and the exhaust gases flowing therethrough. 
     A series of thermocouples  100 ,  102 ,  104  are provided to monitor the temperature at various locations in the inner pipe section  82 ,  84 ,  86 . A first thermocouple  100  is provided near the inlet to the inner pipe section  82 ,  84 ,  86  to measure the temperature of the exhaust gases entering the heat exchanger. A second thermocouple  102  extends through the outer pipe section  92 ,  94 ,  96  and is provided at a midpoint of the inner pipe section  82 ,  84 ,  86  to measure the temperature of the inner pipe section within the heat exchanger. Finally, a third thermocouple  14  is provided near an outlet of the inner pipe section  82 ,  84 ,  86  to measure temperature immediately downstream the heat exchanger. It is expected that the measurements from the thermocouples will illustrate a gradient of temperatures within each test pipe section  72   c ,  74   c ,  76   c  that can be correlated to deposit formation along the length of the inner test pipe  82 ,  84 ,  86 . 
     In addition to the affects of temperature, it is contemplated that the testing jig according to the third embodiment may be used to test the effects of other physical variables in combination with temperature. For example, a temperature modified test branch may further be used to test the effects of oil or water (humidity), fuel additives, oil and engine treatments, alcohol and/or other combustibles that may be used in place of or in conjunction with gasoline and, to that end, may be pre-loaded with such substances, or may have metered amounts of such substances introduced therein throughout the test procedure by means of appropriate injection ports (not shown). 
     Although the preferred embodiments of the present invention have been described herein with particularity, it is considered apparent that the invention is capable of numerous modifications, replacements, and modifications of parts without departing from the scope and spirit of the present invention. Accordingly, the present invention is not to be limited to the specific embodiments described herein, but rather is only to be defined by the claims appended hereto.