Abstract:
An exhaust after-treatment system including an exhaust passage having at least a first portion and a second portion. An exhaust treatment component may be positioned within the exhaust passage between the first and second portions, and an insulating blanket insulates each of the first portion, second portion, and the exhaust treatment component. Temperature sensors may be positioned at the first portion, the second portion, the exhaust treatment component, wherein each sensor monitors the temperature at its location. A controller may have access to temperature data associated with an insulated exhaust after-treatment system, and the controller compares the monitored temperatures to the temperature data to determine whether a difference exceeding a predetermined threshold exists. If the difference exceeds a predetermined threshold, the controller outputs an error signal identifying particular portions of the exhaust system that are no longer insulated.

Description:
FIELD 
       [0001]    The present disclosure relates to an exhaust after-treatment system including an insulating detection system. 
       BACKGROUND 
       [0002]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0003]    Aqueous urea exhaust treatment fluids are used to treat engine exhaust. Because the urea solution is aqueous, the urea solution is preferably atomized by dosing module when dosing into the exhaust stream to ensure conversion of the urea in the solution to ammonia and evaporation of the water. At lower temperatures, however, it can be difficult to maintain atomization of the urea solution such that the dosed urea solution may impinge on interior walls of exhaust passage. In these cases, reaction by-products may form solid deposits on interior wall of exhaust passage that can block exhaust passage. 
       SUMMARY 
       [0004]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0005]    The present disclosure provides an exhaust after-treatment system for treating an exhaust produced by an engine. The exhaust after-treatment system includes an exhaust passage that is operable to receive the exhaust produced by the engine. The exhaust passage may include at least a first portion and a second portion. An exhaust treatment component may be positioned within the exhaust passage between the first and second portions. An insulating blanket insulates each of the first portion, second portion, and the exhaust treatment component. A first temperature sensor may be positioned at the first portion, a second temperature sensor may be positioned at the second portion, and a third temperature sensor may be positioned at the exhaust treatment component, wherein each sensor outputs a signal indicative of the temperature at its location. A controller may be in receipt of the signals output by the temperature sensors, and may have access to temperature data associated with an insulated exhaust after-treatment system, wherein the controller compares the signals indicative of temperature to the temperature data and determines whether a difference exceeding a predetermined threshold exists. The controller may output an error signal identifying particular portions of the exhaust system that are no longer insulated based on the difference determination. 
         [0006]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0007]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0008]      FIG. 1  is a schematic representation of an exemplary exhaust system including features according to the present disclosure; 
           [0009]      FIG. 2  is a perspective cross-sectional view of a portion of an exhaust passage according to a principle of the present disclosure; 
           [0010]      FIG. 3  is a flow-chart exemplifying a control methodology according to a principle of the present disclosure; 
           [0011]      FIG. 4  is a flow-chart exemplifying another control methodology according to a principle of the present disclosure; and 
           [0012]      FIG. 5  is a perspective cross-sectional view of a portion of an exhaust passage according to another principle of the present disclosure. 
       
    
    
       [0013]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0014]    Example embodiments will now be described more fully with reference to the accompanying drawings. 
         [0015]      FIG. 1  schematically illustrates an exemplary exhaust system  10  according to the present disclosure. Exhaust system  10  can include at least an engine  12  in communication with a fuel source (not shown) that, once consumed, will produce exhaust gases that are discharged into an exhaust passage  14  having an exhaust after-treatment system  16 . Downstream from engine  12  can be disposed a pair of exhaust treatment components  18  and  20 , which can include catalyst-coated substrates or filters  22  and  24 . Catalyst-coated substrates or filters  22  and  24  can be any combination of a diesel particulate filter (DPF), a diesel oxidation catalyst (DOC), a selective catalytic reduction (SCR) component, a lean NOx catalyst, an ammonia slip catalyst, or any other type of exhaust treatment device known to one skilled in the art. If a DPF is used, it may be catalyst-coated. 
         [0016]    Although not required by the present disclosure, exhaust after-treatment system  16  can further include components such as a thermal enhancement device or burner  26  to increase a temperature of the exhaust gases passing through exhaust passage  14 . Increasing the temperature of the exhaust gas is favorable to achieve light-off of the catalyst in the exhaust treatment component  18  in cold-weather conditions and upon start-up of engine  12 , as well as initiate regeneration of the exhaust treatment component  18  when the exhaust treatment substrate  22  or  24  is a DPF. 
         [0017]    To assist in reduction of the emissions produced by engine  12 , exhaust after-treatment system  16  can include a dosing module  28  for periodically dosing an exhaust treatment fluid into the exhaust stream. As illustrated in  FIG. 1 , dosing module  28  can be located upstream of exhaust treatment component  18 , and is operable to inject an exhaust treatment fluid into the exhaust stream. In this regard, dosing module  28  is in fluid communication with a reagent tank  30  and a pump  32  by way of inlet line  34  to dose an exhaust treatment fluid such as diesel fuel or urea into the exhaust passage  14  upstream of exhaust treatment components  18  and  20 . Dosing module  28  can also be in communication with reagent tank  30  via return line  36 . Return line  36  allows for any exhaust treatment fluid not dosed into the exhaust stream to be returned to reagent tank  30 . Flow of the exhaust treatment fluid through inlet line  34 , dosing module  28 , and return line  36  also assists in cooling dosing module  28  so that dosing module  28  does not overheat. Although not illustrated in the drawings, dosing module  28  can be configured to include a cooling jacket that passes a coolant around dosing module  28  to cool it. 
         [0018]    The amount of exhaust treatment fluid required to effectively treat the exhaust stream may vary with load, engine speed, exhaust gas temperature, exhaust gas flow, engine fuel injection timing, desired NO x  reduction, barometric pressure, relative humidity, EGR rate and engine coolant temperature. To monitor these variables, exhaust system  10  can include, for example, a first temperature sensor  37  operable to output a signal indicative of an exhaust temperature. The signal output by first temperature sensor  37  can act as a baseline signal that allows controller  42  to begin dosing of the exhaust treatment fluid if the measured temperature is greater than a predetermined threshold (e.g., 150 C). If the baseline signal is not indicative of the minimum temperature allowed for dosing, controller  42  will not allow dosing module  28  to dose exhaust treatment fluid into the exhaust stream. 
         [0019]    Other exemplary sensors include a NO x  sensor or meter  38  that may be positioned downstream from exhaust treatment component  18 . NO x  sensor  38  is operable to output a signal indicative of the exhaust NO x  content to an engine control unit  40 . All or some of the engine operating parameters may be supplied from engine control unit  40  via the engine/vehicle databus to an exhaust after-treatment system controller  42 . Controller  42  could also be included as part of the engine control unit  40 . Exhaust gas temperature, exhaust gas flow and exhaust back pressure and other vehicle operating parameters may be measured by respective sensors, as indicated in  FIG. 1 . 
         [0020]    The amount of exhaust treatment fluid required to effectively treat the exhaust stream can also be dependent on the size of the engine  12 . In this regard, large-scale diesel engines used in locomotives, marine applications, and stationary applications can have exhaust flow rates that exceed the capacity of a single dosing module  28 . Accordingly, although only a single dosing module  28  is illustrated for dosing exhaust treatment fluid, it should be understood that multiple dosing modules  28  for reagent injection are contemplated by the present disclosure. 
         [0021]    Exhaust after-treatment system  16  may be wrapped in an insulating blanket  44 . Insulating blanket  44  may include a plurality of sections  44   a ,  44   b ,  44   c ,  44   d , and  44   e  that wrap various portions of exhaust after-treatment system  16 . For example, section  44   a  may be used to insulate exhaust passage  14  at a position located between engine  12  and first exhaust treatment component  18 ; section  44   b  may be used to insulate first exhaust treatment component  18 ; section  44   c  may be used to insulate exhaust passage  14  at a position located between first and second exhaust treatment components  18  and  20 ; section  44   d  may be used to insulate second exhaust treatment component  20 ; and section  44   e  may be used to insulate exhaust passage  14  at a position downstream from second exhaust treatment component  20 . Sections  44   a  to  44   e  may be integral. Alternatively, sections  44   a  to  44   e  may be removably coupled to each other using various fastening mechanisms including zippers, hooks and eyelets (not shown), or any other fastening mechanisms known to one skilled in the art. Removably coupling sections  44   a  to  44   e  to each other allows various portions of exhaust after-treatment system  16  to be serviced, without entirely removing insulating blank  44 . 
         [0022]    Insulating blanket  44  assists in preventing heat from escaping exhaust after-treatment system  16 . Insulating blanket  44 , therefore, may be formed of a heat-shielding or heat-reflecting material, or may be formed from a fiberglass or mat material. It should be understood that any type of insulating material may be used, without limitation. By preventing heat from escaping exhaust after-treatment system  16 , the catalysts of exhaust treatment components  18  and  20  can more effectively treat exhaust produced by engine  12  to remove various emissions from the exhaust stream. 
         [0023]    Further, preventing heat from escaping exhaust after-treatment system  16  also assists in maintaining atomization of the reagent exhaust treatment fluid after being dosed into the exhaust stream by dosing module  28 . By maintaining atomization of the reagent exhaust treatment fluid, the formation of deposits on interior walls of exhaust passage  14  can be prevented, or at least substantially minimized. 
         [0024]    Exhaust after-treatment system  16  may include a plurality of second temperature sensors  46 . Second temperature sensors  46  may be thermocouples, thermistors, or any other type of temperature sensor known to one skilled in the art. Second temperature sensors  46  may be located at various positions along exhaust after-treatment system  16 , and are used to monitor a temperature of the exhaust gases within exhaust after-treatment system  16 .  FIG. 2  illustrates a portion of exhaust passage  14  including a temperature sensor  46  in communication with an interior  48  of exhaust passage  14  for monitoring exhaust temperatures. 
         [0025]    As shown in  FIG. 1 , the “second” temperature sensors include a temperature sensor  46   a  that may be coupled to exhaust passage  14  at a location between engine  12  and first exhaust treatment component  18 ; a temperature sensor  46   b  that may be coupled to a housing  18   a  of first exhaust treatment component  18 ; a temperature sensor  46   c  that may be coupled to exhaust passage  14  at a location between first exhaust treatment component  18  and second exhaust treatment component  20 ; a temperature sensor  46   d  that may be coupled to a housing  20   a  of second exhaust treatment component  20 ; and a temperature sensor  46   e  may be coupled to exhaust passage  14  at a location downstream from second exhaust treatment component  20 . Each second temperature sensor  46   a  to  46   e  may communicate with controller  42  or ECU  40 . 
         [0026]    Although the use of second temperature sensors  46   a  to  46   e  is preferable, it should be understood that only exhaust treatment components  18  and  20  may include temperature sensors  46   b  and  46   d , respectively. Alternatively, the present disclosure contemplates that only second temperature sensors  46   a ,  46   c , and  46   e  may be used at positions upstream and downstream from the respective first and second exhaust treatment components  18  and  20  to monitor the exhaust temperature as the exhaust stream enters and exits each component. Another alternative is that only second temperature sensor  46   c  is utilized at a location proximate dosing module  28 . Regardless, it should be understood that any number of second temperature sensors  46  may be used without departing from the scope of the present disclosure. 
         [0027]    In addition to monitoring a temperature of the exhaust stream at various location of exhaust after-treatment system  16 , second temperature sensors  46   a  to  46   e  may be used to monitor whether insulating blanket  44 , or any section  44   a  to  44   e  thereof, has been removed from exhaust after-treatment system  16 .  FIG. 3  illustrates an exemplary control algorithm used to determine whether insulating blanket  44 , or any section  44   a - 44   e  thereof, has been removed. 
         [0028]    At control block  100 , controller  42  or ECU  40  requests second temperature sensors  46   a  to  46   e  to monitor a temperature of the exhaust stream. After receiving signals indicative of the temperatures from each temperature sensor  46   a  to  46   e , controller  42  or ECU  40  can compare the signals indicative of the measured temperatures to various temperatures that may be stored in a look-up-table in either controller  42  or ECU  40  (control block  102 ). The stored temperatures can be based on known exhaust temperatures at various engine loads for an insulated exhaust after-treatment system. If any of the measured temperatures in each section  44   a  to  44   e  are outside a predetermined range, controller  42  or ECU  40  can determine that an abnormality has occurred (control block  104 ). Alternatively, controller  42  or ECU  40  can compare the measured temperatures to a single stored temperature, and if a difference between these temperatures is greater than a predetermined threshold, controller  42  or ECU  40  can determine that an abnormality has occurred. In either case, controller  42  or ECU  40  can then infer that insulating blanket  44 , or a section  44   a  to  44   e  thereof, has been removed (control block  106 ). Table 1 (below) is an exemplary look-up-table stored in controller  42  or ECU  40 . 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 High Engine 
                 Moderate Engine 
                 Low Engine 
               
               
                   
                 Section 
                 Load 
                 Load 
                 Load 
               
               
                   
                   
               
             
             
               
                   
                 44a 
                 500-600 C. 
                 350-400 C. 
                 300-350 C. 
               
               
                   
                 44b 
                 450-500 C. 
                 300-325 C. 
                 250-300 C. 
               
               
                   
                 44c 
                 400-450 C. 
                 275-300 C. 
                 200-250 C. 
               
               
                   
                 44d 
                 350-400 C. 
                 250-275 C. 
                 175-200 C. 
               
               
                   
                 44e 
                 325-350 C. 
                 225-250 C. 
                 150-175 C. 
               
               
                   
                   
               
             
          
         
       
     
         [0029]    In this regard, if insulating blanket  44  or a section  44   a  to  44   e  thereof has been removed, the temperature measured by a particular temperature sensor  46   a - 46   e  will be lower due to the loss of heat from exhaust after-treatment system  16 . The loss of heat from a particular location could be the result of insulating blanket  44  degradation, or from the removal of a section  44   a  to  44   e  of insulating blanket  44  during a service procedure, which was not replaced after the procedure. Regardless, when a temperature abnormality is detected (block  104 ), controller  42  or ECU  40  may output an error signal that identifying the location that is no longer insulated, signal engine  12  to cease operation, or prevent dosing module  28  from dosing exhaust treatment fluid into the exhaust stream (control block  108 ). By signaling an error, ceasing operation of engine  12 , or by preventing dosing of exhaust treatment fluid into the exhaust stream, deposits within exhaust passage  14  or on exhaust treatment components  18  and  20  can be prevented, or at least substantially minimized. After insulating blanket  44  or sections  44   a  to  44   e  are repaired or replaced, operation of engine  12  can be re-started or dosing can be resumed. If no abnormality is detected, engine  12  and dosing module  28  may continue operation (control block  110 ). 
         [0030]    It should be understood that in large-scale engine applications such as marine, stationary, and locomotive applications, the amount of exhaust produced by engine  12  can be substantial, which can require a substantial amount of reagent exhaust treatment fluid to treat the exhaust. As such, if insulating blanket  44 , or a section  44   a  to  44   e  thereof, has been removed, the loss of heat from exhaust after-treatment system  16  at a particular location can be substantially greater than at other locations of the exhaust system. In these cases, the reagent exhaust treatment fluid may not remain properly atomized and may form deposits within exhaust treatment passage  14 . Because such a large amount of reagent exhaust treatment fluid is needed in large-scale engine applications, the build-up of these deposits can occur fairly quickly, which may result in the build-up of backpressure that prevents optimal operation of engine  12 . Further, the deposit build-up may necessitate a reduction in engine operating time due to the need to remove the deposits from the exhaust after-treatment system  16 . Accordingly, by monitoring the exhaust temperature to determine whether the exhaust after-treatment system  16  is properly insulated, the amount of time needed to service exhaust after-treatment system  16  can be reduced. 
         [0031]      FIG. 4  illustrates another exemplary control algorithm used to determine whether insulating blanket  44 , or any section  44   a - 44   e  thereof, has been removed. In the control algorithm of  FIG. 4 , it should be understood that each temperature sensor  46   a  to  46   e  does not monitor a temperature of the exhaust stream as shown in  FIG. 2 . Rather, each temperature sensor  46   a  to  46   e  is merely coupled to an exterior  50  of exhaust passage  14  or housings  18   a  and  20   a  of the exhaust treatment components  18  and  20 . Specifically, as shown in  FIG. 5 , each temperature sensor  46   a  to  46   e  may be disposed between insulating blanket  44  and the exterior  50  of exhaust passage  14  or housings  18   a  and  20   a.    
         [0032]    At control block  200 , controller  42  or ECU  40  requests each temperature sensor  46   a  and  46   e  to monitor a temperature at the particular location where each temperature sensor  46   a  to  46   e  is located. After receiving measured temperatures from each temperature sensor  46   a  to  46   e , controller  42  or ECU  40  can compare each of the measured temperatures to each other (control block  202 ). If any of the measured temperatures are outside a predetermined range (e.g., 25-50 degrees C. less than the other measured temperatures), controller  42  or ECU  40  can determine that an abnormality has occurred (control block  204 ). Controller  42  or ECU  40  can then infer that insulating blanket  44 , or a section  44   a  to  44   e  thereof, has been removed (control block  206 ). 
         [0033]    In this regard, if insulating blanket  44  or a section  44   a  to  44   e  thereof has been removed, the temperature measured by a particular temperature sensor  46   a - 46   e  will be lower due to the loss of heat from exhaust after-treatment system  16 . The loss of heat from a particular location could be the result of insulating blanket  44  degradation, or from the removal of a section  44   a  to  44   e  of insulating blanket  44  during a service procedure. Regardless, when a temperature abnormality is detected (control block  204 ), controller  42  or ECU  40  may signal engine  12  to cease operation, or preventing dosing of the reagent exhaust treatment fluid by dosing module  28  into the exhaust stream (control block  208 ). By ceasing operation of engine  12 , or by preventing dosing, the build-up of deposits within exhaust passage  14  or on exhaust treatment components  18  and  20  can be prevented, or at least substantially minimized. After insulating blanket  44  or sections  44   a  to  44   e  are repaired or replaced, operation of engine  12  can be re-started or engine load can be increased. If no abnormality is detected, engine  12  and dosing module  28  may continue operation (control block  210 ). 
         [0034]    It should be understood that even though first temperature sensor  37  may output a signal indicative of a temperature above the predetermined threshold allowed for dosing exhaust treatment fluid, the signals output by second temperature sensors  46   a  to  46   e  may still be used to prevent dosing of the exhaust treatment fluid. In this regard, even though the temperature sensed by first temperature sensor  37  is above the predetermined threshold for dosing, the exhaust temperature downstream from first temperature  37  can vary. Accordingly, if second temperature sensors  46   a  to  46   e  identify a temperature anomaly, controller  42  may shut down engine  12  or prevent dosing by dosing module  28  despite the temperature detected by first temperature sensor  37  being above the predetermined threshold. 
         [0035]    Alternatively, based on signals output by second temperatures sensors  46   a  to  46   e , controller  42  may instruct exhaust after-treatment system  16  to operate in a by-pass mode. More specifically, many marine exhaust after-treatment systems may be equipped with a by-pass passage (not shown) that allows for the engine exhaust to escape into the atmosphere without first passing through after-treatment system  16 . If an anomaly is detected by any of second temperature sensors  46   a  to  46   e , controller  42  can shut down after-treatment system  16  and control a valve (not shown) that allows the exhaust to enter the by-pass and exit into the atmosphere. 
         [0036]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.