Abstract:
This patent disclosure relates to monitoring the quality of a reducing agent used in an emission-control system. Because emission-control systems may be used in extreme temperatures, the reducing agent used in these systems may be exposed to extreme temperatures for prolonged periods. This exposure may cause premature degradation of the reducing agent, thereby reducing the effectiveness of the emission-control system. To monitor the quality of the reducing agent, the disclosed systems and methods measure a property of the reducing agent, determine whether the measured property is out of compliance with a predetermined range, and provide a warning signal when the measured property is out of compliance.

Description:
TECHNICAL FIELD 
       [0001]    This patent disclosure relates generally monitoring the quality of a reducing agent and, more particularly to monitoring the quality of a reducing agent used in an emission-control system. 
       BACKGROUND 
       [0002]    To reduce the amount of nitrogen oxides (NO x ) emitted from compression engines, manufacturers often employ emission-control systems, such as selective catalytic reduction (SCR) systems. In a conventional SCR system, a pump may inject, by way of a nozzle, a reducing agent, such as an aqueous urea solution, into an after-treatment catalytic converter, where the urea solution mixes with engine exhaust. This mixing coverts the oxides of nitrogen, which are formed during combustion, to elementary nitrogen and water, thereby removing NOx from the exhaust. 
         [0003]    Because compression engines may be used, in extreme temperatures, the urea solution used in the SCR systems of these engines may be exposed to extreme temperatures for prolonged periods. This exposure may reduce the quality of the urea solution. For example, such exposure may change the concentration level of the urea solution, but effective operation of the SCR system may depend, in part, on the concentration level of the urea solution. For example, in some SCR systems, the specified concentration level of the urea solution is 32.5±0.5%. If the concentration level deviates from this specified range, the SCR system may perform inefficiently, causing the engine to emit unacceptable amounts of NOx and violate applicable emission standards. Additionally, operating the SCR system with poor quality urea may reduce the useful life of the aftertreatment catalytic converter and other components of the SCR system and the engine. Further, maintaining the proper concentration level may prevent the urea solution from freezing, which is important because, if urea freezes, it may expand and possibly damage components of the engine and/or SCR system. An aqueous urea solution having a concentration level of 32.5%±0.5% has a freezing point at approximately −11° F.; other concentration levels may have higher freezing points, which may be disadvantageous. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0004]    The disclosure describes, in one aspect, a method for monitoring the quality of a reducing agent used in an emission-control system. The method includes measuring the refractive index of the reducing agent and determining whether the measured refractive index of the reducing agent is out of compliance with a predetermined range. The method further includes providing a signal when the measured refractive index is out of compliance with such predetermined range. 
         [0005]    The disclosure describes, in another aspect, a method for determining whether a product warranty applies to cover the cost of replacing a failed component of an emission-control system. The method includes measuring a property of a reducing agent used in the emission-control system and determining whether the measured property of the reducing agent is out of compliance with a predetermined range. The method further includes providing an out-of-compliance warning signal when the measured property of the reducing agent is out of compliance with the predetermined range and determining a usage value representative of a usage of the system while the measured property of the reducing agent is out of compliance with the predetermined range. 
         [0006]    The disclosure describes, in yet another aspect, an emission-control system capable of monitoring the quality of a reducing agent used therein. The emission-control system includes a sensor for determining the refractive index of the reducing agent and a controller in communication with the sensor. The sensor is configured to provide a refractive-index measurement and the controller is configured to receive the refractive-index measurement, determine whether the refractive-index measurement is out of compliance with a predetermined range, and provide a warning signal when the refractive-index measurement is out of compliance with the predetermined range. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic representation of an emission-control system, according to an embodiment of the present disclosure; and 
           [0008]      FIG. 2  is a flowchart of a program employed in connection with an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    The systems and methods described herein monitor the quality of a reducing agent used in an emission-control system and provide a warning signal in the event the quality drops below a predetermined standard. As noted above, operating with a poor quality reducing agent may cause system inefficiency, harmful emissions, and premature failure of system components. To determine whether a product warranty applies for paying the cost of replacing a failed component of the emission-control system, the disclosed systems and methods may also determine whether, and the extent that, an operator used the emission-control system while the warning signal was being generated. 
         [0010]    Referring now to the drawings,  FIG. 1  illustrates an exemplary emission-control system  100  in which features consistent with embodiments disclosed herein may be implemented. The system  100  may include a tank  110 , a pump  120 , a controller  130 , a dosing control  140 , a nozzle  150 , and an exhaust system  160 . The tank  110  may be a reservoir used to hold gaseous solutions, solid-based solutions, or aqueous solutions used as a reducing agent in SCR systems. For illustrative convenience, the systems and methods disclosed herein will be described with reference to an aqueous urea solution stored in the tank  110  and used as the reducing agent in the system  100 . However, it will be appreciated that other reducing agents such as an ammonia solution may be used in the system  100 . The tank  110  may include a heating and cooling system to regulate the temperature of the stored urea solution. For example, the tank  110  may maintain the solution between −11° C. and 50° C. 
         [0011]    The pump  120  may be a device that is hardware or software controlled that extracts the urea solution from the tank  110  and directs it to the dosing control  140 . The dosing control  140  may be a hardware or software controlled device that controls the amount of urea solution to be added to the exhaust. The nozzle  150  receives controlled amounts of the urea solution from the dosing control  140 , and injects the received solution into the exhaust system  160 . In an embodiment, a SCR catalyst  170  may be used to allow the NOx molecules within the exhaust gas mixture to react with ammonia molecules to produce molecular nitrogen. Alternatively, the exhaust system  160  may operate without the SCR catalyst  170 . 
         [0012]    The system  100  may include a sensor  180  for determining a property of the urea solution stored in the tank  110 . In an embodiment, the sensor  180  is a refractometer with an integrated in temperature sensor for determining the refractive index of the urea solution. The refractometer  180  is configured to compensate for temperature when measuring the refractive index of the urea solution, and to transmit the measured refractive index to the controller  130 . In the illustrated embodiment, the sensor  180  is located in the tank  110 . It will be appreciated, however, that the sensor  180  may be located anywhere in the system  100  between the tank  110  and the nozzle  150  where an adequate measurement can be taken. 
         [0013]    Because a correlation exists between the refractive index and the concentration level, the controller  130 , based on the measured refractive index, may, according to an embodiment, determine the concentration level of the urea. For example, the controller  130  may be provided with conversion equations or tables for calculating the concentration level of the urea solution based on the measured refraction index. 
         [0014]    The controller  130  may be a processing system that monitors and controls operations of the system  100 . The controller  130  may be configured to collect information from the sensor  180  and other various sensors operating within the system  100  and the host system and to provide control signals that affect the operations of the system  100  and/or the host system. In an embodiment, the controller  130  may be part of an engine control module (ECM) that monitors and controls the operation of an engine associated with the system  100 . For example, the controller may be a module that is programmed or hardwired within an ECM that performs functions dedicated to certain embodiments disclosed herein. In an embodiment, the controller may include software that is stored as instructions and data within a memory device of an ECM and which is executed by a processor operating within the ECM. Alternatively, the controller  130  may be a module that is separate from other components of a host system. 
         [0015]      FIG. 1  shows an exemplary controller  130  configured as a separate module dedicated to the system  100  consistent with certain features relating to an embodiment of the disclosure. The controller  130  may include a processor  136 , memory  137 , and an interface  138 . The processor  136  may be a processing device, such as a microcontroller, that may exchange data with memory  137  and the interface  138  to perform certain processes consistent with features related to the present disclosure. Although a single processor is shown in  FIG. 1 , it will be appreciated that the controller  130  may include a plurality of processors that operate collectively to perform functions consistent with certain embodiments of the present disclosure. 
         [0016]    Memory  137  may be any type of storage device that is configured to store information used by the processor  136 . For example, memory  137  may include magnetic semiconductors, tape, and/or optical type storage devices that may be volatile or non-volatile in nature. Moreover, memory  137  may include one or more storage devices configured in various architectures, such as redundant configurations for fault tolerant operations. It will be appreciated that the type, configuration, and architecture of memory  137  may vary without departing from the spirit and scope of the present disclosure. 
         [0017]    The interface  138  may be an input/output interface device that receives data from the processor  136  and from entities external to the controller  130 . In an embodiment, the interface  138  may by be accessible, and provide visual and audible signals, to an operator of the host system. For example, the host system may be a land vehicle and the interface  138  may be located in an operator compartment of the vehicle. Further, the interface  138  may also provide data to the processor  136  and the external entities. The interface  138  may be a module that is based on hardware, software, or a combination thereof. It will be appreciated that the configuration of the interface  138  may vary without departing from the scope of the present disclosure. For example, the interface  138  may include separate communication ports dedicated for receiving and sending data, respectively. Alternatively, the interface  138  may be integrated within the processor  136  to provide and/or send data to and/or from one or more processing elements operating within the processor  136 . 
         [0018]    To monitor the quality of the urea solution used in the system  100 , the controller  130  may be provided with a program  200 . The program  200  may direct the controller  130  to analyze information received from the sensor  180  and, based on that information, determine whether the quality of the urea solution is acceptable. For example, a property of the urea solution, such as refractive index, may be indicative of the overall quality of the urea solution, and the program  200  may direct the controller  130  to monitor information related to that property and thereby monitor the quality of the urea solution. Also, for example, the program  200  may instruct the controller  130  to calculate the concentration level, based on the measured refractive index, and make quality assessments of the urea solution based on the calculated concentration level. If the quality of the urea solution is below a predetermined range, the program  200  may instruct the controller  130  to monitor usage of the system  100  until the quality is restored. Further, the program  200  may instruct the controller to calculate, and provide to service personnel, a value that reflects the extent of such usage. 
         [0019]    With reference to  FIG. 2 , the program  200 , according to an embodiment, will be described. The program  200  begins at a step  210  in which the program  200  starts or begins. In step  220 , the controller  130  reads the sensor  180  to obtain the refractive index measurement of the urea solution. In step  230 , the controller compares the measured refractive index with a predetermined range of acceptable refractive index measurements to determine whether the sensor reading is within the predetermined range. The predetermined range of acceptable refractive index measurements may be provided on memory  137  and accessed by the processor  136  when executing the program  200 . In an embodiment, the predetermined range is from 1.3817 A.U. to 1.3840 at 20° C. in accordance with DIN V 70070. This predetermined range corresponds to a concentration level between 32% and 33%, which is the ideal concentration level for efficient operation of the system  100 . It will be appreciated that other predetermined ranges may also be acceptable. 
         [0020]    If the sensor reading is within the predetermined range, the controller  130  proceeds to step  295  in which the controller  130  returns to step  210 . If, however, the sensor reading is outside of the predetermined range, the controller  130  continues to step  240 . In step  240 , the controller  130  initiates an operator warning by transmitting an out-of-compliance signal to the output device  138 , which generates a warning signal. The warning signal may be visually and/or audibly observed by the operator. 
         [0021]    The program  200  then proceeds to step  250  in which the controller records an out-of-compliance event in memory  137 . The controller  130  can associate a time stamp and/or a usage stamp with the out-of-compliance event. The time stamp can be the time and date of the out-of-compliance event and the usage stamp can be, for example, miles or hours. For example, if the host system is a land vehicle, the controller  130  may record the mileage of the engine of the vehicle when the out-of-compliance event occurred. Also for example, if the host system is a marine vehicle, an aircraft, a generator set, or a machine operating within a manufacturing plant, the controller  130  can record how many hours were on the engine of the host system when the out-of-compliance event occurred. 
         [0022]    Next, in step  260 , the controller rereads the sensor  180  and then, in step  270 , determines whether the out-of-compliance event has been corrected. This determination is based on whether the sensor reading is within the predetermined range. If the sensor reading is outside of the predetermined range, then out-of-compliance event has not been corrected and the controller  130  returns to step  260 . However, if the sensor reading is within the predetermined range, then the out-of-compliance event has been corrected and the controller  130  proceeds to step  275 . 
         [0023]    In step  275 , the controller  130  records the correction event in a fashion similar to recording the out-of-compliance event and later, in step  280 , deactivates the operator warning. Next, in step  285 , the controller  130  determines an out-of-compliance usage value. This value represents the extent the system  100  and/or host system was used with poor quality urea solution. In an embodiment, the out-of-compliance usage value is equal to the difference between the time, number of hours, or mileage, associated with the out-of-compliance event and the correction event. Accordingly, the out-of-compliance usage value can be a time value or a distance value. The controller  130  then, in step  290  records the out-of-compliance usage value, and proceeds to step  295  in which the controller  130  returns to step  210 . 
         [0024]    Should a component of the system  100  or host system fail or malfunction during the relevant product warranty period, service personnel, when determining whether that warranty applies for paying the costs of replacing the component, may access, by way of the interface  138 , the out-of-compliance usage value. For example, if the relevant product warranty is voidable due to out-of-compliance use, service personnel may access the out-of-compliance usage value, via the interface  138 , and determine whether the warranty has been voided by out-of-compliance use. 
       INDUSTRIAL APPLICABILITY 
       [0025]    The industrial applicability of the system  100  described herein will be readily appreciated from the foregoing discussion. A technique is described for monitoring the quality of a reducing agent used in an emission-control system and providing a warning signal in the event the quality drops below a predetermined standard. The warning received from the disclosed systems and methods enables an operator to discontinue operation of the host system until the quality is restored to an acceptable level. This prevents, among other things, inefficient operation, harmful emissions, and premature failure of system components. The present disclosure further provides a technique for determining whether, and the extent, an operator used the emission-control system while the warning signal was being generated, i.e., while the quality of the urea solution was below the predetermined standard. This can assist service personnel in determining, for example, whether a product warranty should apply for replacing any failed component of the emission-control system. 
         [0026]    The system  100  of the present disclosure may be associated with any type of machine engine, such as internal combustion type engines, that operate in various types of host systems. For example, the system  100  may be affiliated with an engine associated with a host system such as a marine vehicle, a land vehicle, and/or an aircraft. Further, the system  100  may be associated with an engine operating in a non-vehicle based host system, such as machines operating within a manufacturing plant or generator sets. Moreover, while the system  100  is shown for illustrative purposes in a SCR system, the system  100  has potential use in other emission-control applications. Accordingly, it will be appreciated that the system  100  may be associated with any type of host system that includes various types of engines that may operate in different environments with different emission-control systems and standards. 
         [0027]    It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
         [0028]    Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 
         [0029]    Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure and claims unless otherwise indicated herein or otherwise clearly contradicted by context.