US20160201535A1

US20160201535A1 - Method of calibrating an after-treatment system retrofitted to an engine

Info

Publication number: US20160201535A1
Application number: US15/075,213
Authority: US
Inventors: Shikha Pokharel; James Harris Mutti, JR.; Matthew Jay Segebart
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2016-03-21
Filing date: 2016-03-21
Publication date: 2016-07-14

Abstract

A method is provided for calibrating an after-treatment system retrofitted onto an engine, the after-treatment system including a Selective Catalytic Reduction (SCR) device therein. The method is implemented using a controller having a memory pre-fed with an Engine-out NOx map, a SCR conversion map, a maximum SCR capability map, and a NOx dosing map corresponding to bench-run conditions for the given engine and the after-treatment system configurations. The method includes updating the Engine-out NOx map, the SCR conversion map, the maximum SCR capability map, and the NOx dosing map by the controller on the basis of actual sensed parameters of an exhaust stream associated with operation of the given engine and after-treatment system. The method further includes directing the controller to vary a feed-forward reductant dosing quantity at the SCR device during a subsequent operation of the engine based on the updated NOx dosing map stored at the controller.

Description

TECHNICAL FIELD

The present disclosure relates to an exhaust after-treatment system retrofitted to an engine. More particularly, the present disclosure relates to a control system for calibrating an exhaust after-treatment system that is retrofitted to a given configuration of an engine.

BACKGROUND

Exhaust after-treatment systems have been typically retrofitted onto internal combustion engines for reducing an amount of undesired emissions in the exhaust stream exiting the engine. For example, a Selective Catalytic Reduction (SCR) system may be utilized to convert NO_xemissions into Nitrogen and water. Such systems may require calibration prior to commencement of operation with a given engine.
U.S. Pat. No. 6,914,746 relates to retrofitting of diesel truck engines with a SCR system to reduce NOx emissions. The SCR system is installed with a controller, a reagent tank, and an injection system on a vehicle. Also, a NOx detector is temporarily installed on the vehicle. The vehicle is operated to collect various engine operating parameters along with measurement of NOx emissions under varying operating conditions. Thereafter, a reagent injection strategy is prepared and installed at the controller. Reagent injection is carried out on the basis of operating conditions as well as the reagent injection strategy to reduce NOx emissions at various operating conditions.
U.S. Pat. No. 8,834,820 (hereinafter referred to as the '820 patent) discloses an adaptive control system for a Selective Catalytic Reduction (SCR) device. The adaptive control system determines a target emission gas conversion ratio of the SCR device based on the monitored operating conditions which is used to vat the amount of reductant being supplied in the SCR device. However, the '820 patent does not disclose a verification and testing procedure for retrofitting of an exhaust after-treatment system.
Also, it has been observed that after-treatment systems have been calibrated on the basis of their operation on a test bench or other experimental setups containing an engine with associated system hardware coupled to an after-treatment system. In order to meet the demands of emission requirements in specific operating environments such as for e.g. different countries where the legislation of emission standards is different, it may be required to carry out various calibration procedures on an after-treatment system retrofitted to an existing engine to achieve optimum performance of the after-treatment system under varying operating conditions of the engine.
Hence, there is a need for a method and a system that can be used to, easily and effectively, calibrate an after-treatment system retrofitted onto a given configuration of engine.

SUMMARY OF THE DISCLOSURE

In an aspect of present disclosure, a method is provided for calibrating an after-treatment system retrofitted onto an engine. The method includes updating, by a controller, an Engine-out NO_xmap pre-fed at a memory associated with the controller on the basis of an input obtained from a NOx sensor disposed upstream of the SCR device for a given operating condition of the engine.
The method further includes determining, using the controller, a conversion factor of a Selective Catalytic Reduction (SCR) device by performing adaptive calibration of the SCR device. The adaptive calibration performed on the SCR device includes a comparison of a NOx conversion desired from the SCR device with an actual NOx conversion of the SCR device measured from inputs from the NOx sensor disposed upstream of the SCR device and a NOx sensor disposed downstream of the SCR device for the given operating condition of the engine. The method then includes updating, by the controller, a SCR conversion map for the given SCR device pre-fed at the memory on the basis of the determined conversion factor for the SCR device.
The method further includes determining, by the controller, a maximum conversion capability of the SCR device for a given configuration of the engine and the retrofitted after-treatment system based on inputs from an ammonia (NH₃) sensor and a NO_xsensor disposed downstream of the SCR device for the given operating condition of the engine. The method also includes obtaining, by the controller, a pre-determined reductant dosing quantity corresponding to the given operating condition of the engine from a maximum SCR capability map pre-fed at the memory. The method then includes updating the pre-fed maximum SCR capability map by the controller on the basis of the determined maximum conversion capability of the SCR device.
The method further includes determining, by the controller, a dosing offset value from comparison between a current reductant dosing quantity at the SCR device with a pre-determined dosing quantity of the reductant required at the SCR device corresponding to the NOx conversion desired from the SCR device and minimal NH₃slip for the given configuration and operating condition of the engine. The method then includes updating, by the controller, a NOx dosing map for the SCR device at the memory, on the basis of the determined dosing offset value for the SCR device.
The method further includes storing the updated Engine-out NO map, the updated SCR conversion map, the maximum SCR capability map, and the NOx dosing map at the memory; and varying, with the help of the controller, a feed-forward reductant dosing quantity at the SCR device during a subsequent operation of the engine based on the updated NOx dosing map stored at the controller.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an engine retrofitted with an after-treatment system showing an emissions control system for calibrating the retrofitted after-treatment system, in accordance with embodiments of the present disclosure;

FIG. 2 is a diagrammatic representation of calibrating an Engine-out NO_xmap pre-fed at a memory associated with the controller of FIG. 1, in accordance with an embodiment of the present disclosure;

FIG. 3 is a diagrammatic representation of calibrating a SCR conversion map pre-fed at the memory of FIG. 1, in accordance with an embodiment of the present disclosure;

FIG. 4 is a diagrammatic representation of calibrating a maximum SCR capability map pre-fed at the memory of FIG. 1, in accordance with an embodiment of the present disclosure;

FIG. 5 is a diagrammatic representation of calibrating a NOx dosing map pre-fed at the memory of FIG. 1, in accordance with an embodiment of the present disclosure;

FIG. 6 is a flow chart showing a low-level implementation of an exemplary process for calibrating the exhaust after-treatment system retrofitted to the engine, in accordance with an embodiment of the present disclosure; and

FIG. 7 is a flow-chart depicting a method of calibrating the after-treatment system, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughout the drawings to refer to same or like parts. Moreover, references to various elements described herein are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be construed to relate to the plural and vice-versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claims.
The disclosure sets forth a control system and a method for commissioning operation of an after-treatment system retrofitted onto an engine. More particularly, the present disclosure relates to a control system and a method for calibrating the after-treatment system retrofitted onto the engine so as to optimize an operation of the retrofit after-treatment system under varying operating conditions of the given engine and the after-treatment system configurations.
FIG. 1 is a diagrammatic illustration of an exemplary engine system 100 according to embodiments of this disclosure. The engine system 100 includes a power source 112, and an after-treatment system 110 fluidly coupled to the power source 112, and an emissions control system 114. The power source 112 disclosed herein, may include an internal combustion engine, such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine (e.g., a natural gas engine), or any other type of combustion engine known to one skilled in the art. Although an internal combustion engine is disclosed herein, in other embodiments, it is also contemplated that the power source 112 may alternatively embody a furnace or a similar non-engine device.
As shown in the illustrated embodiment of FIG. 1, the power source 112 embodies an internal combustion engine. For sake of simplicity in the present disclosure, reference to the power source 112 will hereinafter be made as ‘the engine’ and denoted using identical numeral ‘112’. The engine 112 disclosed herein may include one or more combustion chambers 120 that convert potential chemical energy (usually in the form of a combustible fluid) into useful mechanical work. The engine 112 may receive air via, an induction valve 115 located along an inlet passageway 116 located upstream of the engine 112 and may output an exhaust flow via a downstream passageway 118.
The after-treatment system 110 may be configured to reduce particulate matter and harmful gases emitted from the engine 112 after a combustion process. The after-treatment system 110 disclosed herein may include a particulate filtering device 124, a reductant dosing injector 126, and a Selective Catalytic Reduction (SCR) device 128.
The particulate filtering device 124 disclosed herein may filter particulate matter, soot, and/or chemicals from the exhaust flow before the flow is released into the atmosphere via an exhaust passageway 150 disposed downstream of the SCR device 128. As the exhaust flow interacts with a catalyst at the particulate filtering device 124, hydrocarbons and/or other chemicals in the exhaust flow may be oxidized. The catalyst material in the particulate filtering device 124 may also increase the amount of exhaust gases, such as nitrogen dioxide (NO₂), in the exhaust flow to improve a passive regeneration capacity and a reduction efficiency of other gases, such as NOx.
The SCR device 128 may be a flow-through device configured to catalyze a reaction between exhaust gases, such as NOx, and a reduction agent e.g., anhydrous ammonia, aqueous ammonia, urea. The reductant dosing injector 126 may inject a reduction agent to dose a surface of the SCR device 128. The reductant dosing injector 126 may be located at or upstream of the SCR device 128 and may embody any type of fluid injector known in the art. The reductant dosing injector 126 may fluidly communicate with a reduction agent supply tank (not shown) to provide for repeated injections of the reduction agent.
The emissions control system 114 disclosed herein may include a controller 130 communicably coupled to the engine 112. The emissions control system 114 also includes a plurality of sensors 132, 138 and a sensor package 135 including at least one sensor 134 therein. As shown in the illustrated embodiment of FIG. 1, the sensor package 135 could include an additional sensor 136 explanation to which will be made later herein. Each of the sensors 132, 134, 136, 138 is disposed in communication with the controller 130 and may be configured to measure changes in at least one specific parameter associated with an exhaust flow through the after-treatment system 110. The sensor 132 is embodied in the form of a first NOx sensor 132 and located upstream of the SCR device 128 as shown in FIG. 1. The first NOx sensor 132 is configured to measure the amount of NOx in an exhaust stream upstream of the SCR device 128.
Similarly, the sensor 134 disclosed herein is embodied in the form of a second NOx sensor 134 and located downstream of the SCR device 128. The second NOx sensor 134 disclosed herein is configured to measure the amount of NOx in an exhaust stream downstream of the SCR device 128 i.e., the exhaust stream exiting the SCR device 128 via the exhaust passageway 150. Likewise, the sensor 136 disclosed herein could be embodied in the form of an ammonia (NH₃) sensor 136 and located downstream of the SCR device 128. For example, as shown in FIG. 2, the NH₃sensor 136 is located at an outlet of the SCR device 128. The NH₃sensor 136 is configured to measure the amount of NH₃slip in the exhaust stream downstream of the SCR device 128 i.e., the exhaust stream exiting the SCR device 128 via the exhaust passageway 150.
Moreover, the sensor 138 disclosed herein is embodied in the form of a reductant dosing sensor 138 and located downstream of the reductant dosing injector 126. For example, as shown in FIG. 1, the reductant dosing sensor 138 may be located at an outlet of the reductant dosing injector 126. The reductant dosing sensor 138 is configured to measure the amount of reductant agent for e.g., anhydrous ammonia, aqueous ammonia, urea injected in the exhaust stream flowing through the SCR device 128.
Although the second NOx sensor 134 and the NH₃sensor 136 are disclosed herein, it may be noted that a scope of the terms “sensor package” is not limited to the second NOx sensor 134 and the NH₃sensor 136 alone. In another embodiment, it can also be contemplated to deduce the amount of NH₃slip downstream of the SCR device 128 by co-relating other sensed parameters including, but not limited to, the amount of NOx downstream of the SCR device 128 i.e., by using the second NOx sensor 134 and the amount of reductant dosed by the reductant dosing injector 126 i.e., by using the reductant dosing sensor 138 as it is envisioned that an amount of NOx downstream of the SCR device 128 and hence, an amount of NH₃slip downstream of the SCR device 128 may be a function of the amount of reductant dosed by the reductant dosing injector 126.
In a particular configuration of the sensor package 135 where the sensor package includes only the second NOx sensor 134, it may be assumed for computation purposes that the amount of NH₃slip could be inversely proportional to the amount of reductant dosed at the SCR device 128 by the reductant dosing injector 126. Accordingly, it is to be noted that the scope of the terms “sensor package” disclosed herein is not limiting of this disclosure, rather the scope of the terms “sensor package” can extend to include fewer or more number of sensors that are configured to perform the functionality of determining an amount of NOx and also an amount of NH₃downstream of the SCR device 128, or merely determining an amount of NOx downstream of the SCR device 128 and thereafter deducing the amount of NH3 slip from the amount of NOx downstream of the SCR device 128, both configuration being capable of contemplation by persons skilled in the art without deviating from the spirit of the present disclosure.
The controller 130 disclosed herein may embody a single microprocessor or multiple microprocessors that include means for controlling an amount of reduction agent injected by the reductant dosing injector 126. Numerous commercially available microprocessors may be configured to perform the functions of the controller 130. The controller 130 disclosed herein may communicate with the engine 112 via a communication line 140, the first NOx sensor 132 via a communication line 141, the reductant dosing injector 126 via a communication line 142, the second NOx sensor 134 via a communication line 143, the reductant dosing sensor 138 via a communication line 144, and the NH₃sensor 136 via a communication line 146. It is contemplated that the controller 130 may communicate with other machine sensor (not shown), such as gas sensors, mass flow rate sensors, and/or any other fluid system sensors that may provide information related to one or more operational characteristics of the after-treatment system 110.
The controller 130 disclosed herein may be configured to utilize one or more multi-dimensional maps 148 pre-fed at a memory 152 associated with the controller 130. Inputs used to form the multi-dimensional maps 148 could include various parameters of the engine 112 and the SCR device 128 determined during bench-run, factory-set, or other experimental test conditions for the given configurations of the engine 112 and the SCR device 128. Such parameters may include, but is not limited to, fuel supplied to engine, engine air mass flow rate, inlet A/F ratio, inlet NO₂over NOx ratio, inlet pressure of air, inlet temperature of the SCR device 128, ambient temperature, a total fuel quantity and/or engine speed. It is contemplated that parameters disclosed by the multi-dimensional maps 148 may also be implemented with various formulations e.g., weighting and may include pre-determined models such as, but not limited to, an SCR temperature model, a space velocity model, and/or engine compression ratio model.
It is envisioned that operating conditions bench-run, factory-set, or other experimental test conditions for the engine 112 and the SCR device 128 may be different from actual operating conditions of the engine 112 and the SCR device 128. For example, a gas conversion efficiency, such as NOx conversion efficiency, of the SCR device 128 for a given configuration and actual operating condition of the engine 112 and the SCR device 128 may be different from a NOx conversion efficiency of the SCR device 128 obtained during a corresponding bench-run condition of the SCR device 128 and the engine 112. Thus, the controller 130 may be programmed to optimize the gas conversion efficiency of the SCR device 128, thereby ensuring that emissions, such as NOx emissions, treated by the SCR device 128 conform to the actual operating conditions of the engine 112 and the SCR device 128. Such conformance to actual operating conditions of the engine 112 and the SCR device 128 may be performed by the controller 130 e.g., to meet legislative or other emission requirements as will be described later herein.
FIG. 2 is a diagrammatic representation of calibrating an Engine-out NOx map 148 a that is pre-fed to the memory 152 of the controller 130, in accordance with an embodiment of the present disclosure. It should be noted that in various embodiments of this disclosure, the Engine-out NOx map 148 a and numerous other maps disclosed later herein form part of the pre-fed multi-dimensional maps 148 pre-fed at the memory 152 of the controller 130. The pre-fed Engine-out NOx map 148 a may be based off the amounts of NOx that would ideally exit the engine 112 under varying operational conditions of the engine 112. It is hereby also contemplated that the pre-fed Engine-out NOx map 148 a is, at least in part, a function of the fueling and speed of the engine 112 during bench-run, factory-set, or other experimental test conditions of the engine 112 and the SCR device 128.
In embodiments of the present disclosure, it is also contemplated to determine an actual amount of NOx contained in the exhaust stream exiting the engine 112 based on inputs from the first NOx sensor 132 disposed upstream of the SCR device 128 for the given configuration and operating condition of the engine 112. This input values obtained from the first NOx sensor 132 may be compared with corresponding values from the pre-fed Engine-out NOx map 148 a relating to the given configuration and operating condition of the engine 112 for determining a trim factor. Such determined trim factor may then be incorporated into the pre-fed Engine-out NOx map 148 a for updating the pre-fed Engine-out NOx map 148 a for e.g., by using a first multiplier 205 associated with the controller 130 as shown in FIG. 2, or an adder module (not shown) associated with the controller 130. Also, an updated Engine-out NOx map 148 b may be stored at the controller 130 for controlling an operation of the after-treatment system 110 and more specifically, for optimizing a performance of the SCR device 128 for the given configuration and operating condition of the engine 112. It should be noted that many such trim factor may be beneficially obtained on the basis of multiple inputs received from the first NOx sensor 132, such multiple inputs corresponding to different operating conditions of the engine 112 and being used to update the pre-fed Engine-out NOx map 148 a and obtain the updated Engine-out NOx map 148 b by the controller 130.
Referring to FIG. 3, in another embodiment of this disclosure, the controller 130 is also configured to determine a conversion factor of the SCR device 128 by performing adaptive calibration of the SCR device 128. The adaptive calibration being performed on the SCR device 128 includes a comparison of a NOx conversion desired from the SCR device 128 with an actual NOx conversion of the SCR device 128 measured from inputs from the first and second NOx sensors 132, 134 upstream and downstream of the SCR device 128 for the given operating condition of the engine 112. The desired NOx conversion may be received in the form of a user-input at the controller 130. However, other parameters such as, but not limited to, legislations associated with emission standards may also be used as inputs for the desired NOx conversion required from the SCR device 128. According to embodiments disclosed herein, conversion factor of the SCR device 128 may be mathematically represented by eq. 1 as follows:
Conversion factor=fn(desired NOx conversion, actual NOx conversion by the SCR device 128, pre-fed SCR conversion map 148c); eq. 1; wherein

- Desired NOx conversion is obtained by way of a user input provided to the controller 130;
- and

Actual NOx conversion by the SCR device=(NOx measured in the exhaust stream by the first NOx sensor 132−NOx measured in the exhaust stream by the second NOx sensor 134).
The memory 152 of the controller 130 also includes a pre-fed SCR conversion map 148 c for the given configuration and operating condition of the engine 112 and the SCR device 128. Upon determination of a conversion factor for the SCR device 128 by the controller 130, the controller 130 can incorporate such determined conversion factor of the SCR device 128 into the pre-fed SCR conversion map 148 c for updating the pre-fed SCR conversion map 148 c for e.g., by using a second multiplier 305 associated with the controller 130 as shown in FIG. 3, or an adder module (not shown) associated with the controller 130. Also, an updated SCR conversion map 148 d may be stored at the memory 152 by the controller 130 for implementation in controlling a subsequent operation of the after-treatment system 110 and more specifically, for optimizing a performance of the SCR device 128 and/or the reductant dosing injector 126 for the given configuration and operating condition of the engine 112. It should be noted that many such conversion factors may be beneficially obtained on the basis of multiple inputs received from the first and second NOx sensors 132 and 134; such inputs beneficially corresponding to different operating conditions of the engine 112 to update the pre-fed SCR conversion map 148 c to the updated SCR conversion map 148 d by the controller 130.
It can also be contemplated to provide a user input that is indicative of a relatively high value of desired NOx conversion to the controller 130. The controller 130 can determine the amount of NH₃slip from the NH₃sensor 134. Alternatively, as disclosed earlier herein, the controller 130 can determine the amount of NH₃slip by co-relating the amount of NOx downstream of the SCR device 128 obtained from the second NOx sensor 136 with the amount of reductant injected at the SCR device 128 obtained from the reductant dosing sensor 138. In either case, the amount of NH₃slip determined, directly or indirectly, by the controller 130 can be used by the controller 130 to normalize the relatively high value of desired NOx conversion provided by the user input at the controller 130. Specifically, in an embodiment, based on the amount of NH₃slip determined by the controller 130, the controller 130 can normalize the relatively high value of desired NOx conversion to a pre-determined value such that the pre-determined value beneficially corresponds with little or no NH3 slip downstream of the SCR device 128. The controller 130 may save such pre-determined value corresponding to little or no NH3 slip downstream of the SCR device 128 at the memory 152 for setting an upper or maximum limit to the amount of desired NOx conversion that can be requested at the controller 130 via user inputs.
Moreover, it is also envisioned that with implementation of the pre-determined value corresponding to little or no NH3 slip downstream of the SCR device 128, the controller 130 can optimize performance of the reductant dosing injector 126 to beneficially correspond with a maximum conversion factor of the SCR device 128 so as to cause little or no wastage of the reductant being injected at the SCR device 128. Furthermore, upon determination of the maximum conversion factor for the SCR device 128 by the controller 130, the controller 130 can incorporate such determined conversion factor of the SCR device 128 into the pre-fed SCR conversion map 148 c for updating the pre-fed. SCR conversion map 148 c for e.g., by using the second multiplier 305 associated with the controller 130 as shown in FIG. 3, or an adder module (not shown) associated with the controller 130. Also, the updated SCR conversion map 148 d may be stored at the memory 152 by the controller 130 for implementation in controlling a subsequent operation of the after-treatment system 110 and more specifically, for optimizing a performance of the SCR device 128 and/or the reductant dosing injector 126 for the given configuration and operating condition of the engine 112.
In another embodiment of this disclosure as shown in FIG. 3, the controller 130 is also configured to determine a maximum conversion capability of the SCR device 128 for a given configuration of the engine 112 and the retrofitted after-treatment system 110 based on inputs from the second NOx sensor 134 and the NH₃sensor 136 disposed downstream of the SCR device 128. Determination of such maximum conversion capability of the SCR device 128 may be performed by the controller 130 for the given operating condition of the engine 112 and a pre-determined reductant dosing quantity corresponding to the given operating condition of the engine 112. As such, the pre-fed maximum SCR conversion capability maps 148 e could provide conversion capability data pertaining to the maximum SCR conversion capability of the SCR device 128 under varying operating conditions of the given engine 112, and such pre-fed maximum SCR conversion capability maps 148 e may therefore dictate various pre-determined reductant dosing quantities to would need to be injected at the SCR device 128 by the reductant dosing injector 126 corresponding to the given operating conditions of the engine 112. For example, the pre-fed SCR maximum conversion capability map 148 e may dictate that a 0.1 gm/hr/hp dosing quantity or rate of injection of the reductant would be needed from the reductant dosing injector 126 for injection at the SCR device 128 for a given operating condition of the engine 112.
It should be noted that such pre-fed SCR maximum conversion capability map 148 e may be beneficially configured to provide the pre-determined reductant dosing quantities such that, little or no. NOx slip and a negligible or minimal NH₃slip would occur downstream of the SCR device 128 for the respective operating conditions of the engine 112. However, such SCR maximum conversion capability maps 148 e pre-fed to the controller 130 correspond to standardized, factory-setup, or bench-run conditions of the engine 112 and the after-treatment system 110.
Upon determining the maximum conversion capability of the SCR device 128 for the given configuration and operating conditions of the engine 112 and the after-treatment system 110 based on inputs from the sensors 134 and 136 i.e., the second NOx sensor 134 and the NH₃sensor 136 disposed downstream of the SCR device 128, the controller 130 can incorporate a maximum SCR conversion capability factor (deduced from the maximum SCR conversion capability determined for the SCR device 128 from inputs of the second NOx sensor 134 and the NH₃sensor 136 together with appropriate constants) into the pre-fed maximum SCR conversion capability map 148 e for updating the pre-fed map maximum SCR conversion capability map 148 e by for e.g., using a third multiplier 405 associated with the controller 130 as shown in FIG. 4, or an adder module (not shown) associated with the controller 130. Also, an updated maximum SCR conversion capability map 148 f may be stored at the memory 152 of the controller 130 for controlling an operation of the after-treatment system 110 and more specifically, for optimizing a performance of the SCR device 128 for the given configuration and operating condition of the engine 112. It should be noted that such maximum SCR conversion capability factor may be obtained on the basis of multiple inputs received from the second NOx sensor 134 and the NH₃sensor 136; such multiple inputs beneficially corresponding to different operating conditions of the engine 112 and the SCR device 128 and being used by the controller 130 to update the pre-fed maximum SCR conversion capability map 148 e to the updated maximum SCR conversion capability map 148 f.
In another embodiment of this disclosure, the controller 130 is also configured to determine a dosing offset value from comparison between a current reductant dosing quantity at the SCR device 128 with a pre-determined dosing quantity of the reductant required at the SCR device 128, such pre-determined quantity of the reductant corresponding to the NOx conversion desired from the SCR device 128 while also aiming to achieve minimal NH₃slip in the exhaust stream downstream of the SCR device 128 for the given configuration and operating condition of the engine 112. The current reductant dosing quantity may, however, be provided by a pre-fed NOx dosing map 148 g stored at the memory 152 (See FIG. 5). It should be noted that such pre-fed NOx dosing map 148 g may also be configured to beneficially provide pre-determined reductant dosing quantities such that, little or no, NOx slip and a negligible or minimal NH₃slip would occur downstream of the SCR device 128 for the given configuration and operating conditions of the engine 112 and the SCR device 128. However, such pre-fed NOx dosing map 148 g corresponds to standardized i.e., factory-set, or bench-run conditions of the engine 112 and the after-treatment system 110.
Upon determination of the dosing offset value, the controller 130 can incorporate such dosing offset value for updating the pre-fed NOx dosing map 148 g by for e.g., using a fourth multiplier 505 associated with the controller 130 as shown in FIG. 5, or an adder module (not shown) associated with the controller 130. Also, an updated NOx dosing map 148 h may be stored at the memory 152 by the controller 130 for implementing a control in subsequent operation of the after-treatment system 110 and more specifically, for optimizing a subsequent performance of the SCR device 128 based on the given configuration and operating condition of the engine 112. It should be noted that such dosing offset value may be beneficially obtained on the basis of multiple inputs received from the reductant dosing sensor 138; such multiple inputs beneficially corresponding to different operating conditions of the engine 112 and the SCR device 128 for updating the pre-fed NOx dosing map 148 g to the updated NOx dosing map 148 h.
FIG. 6 shows a low-level implementation of an exemplary process 600 for calibrating an after-treatment system e.g., the after-treatment system 110 retrofitted to the engine 112, in accordance with an embodiment of the present disclosure. The process 600 initiates at step 602. In an aspect of the present disclosure as shown at step 604 a, the process 600 may optionally include verifying, using the controller 130, whether one or more sensors 132-138 i.e., the first NOx sensor 132, the second NOx sensor 134, the NH₃sensor 136, and the reductant dosing sensor 138 associated with the after-treatment system 110 are operational. More specifically, the controller 130 may verify if any of the sensors 132-138 are faulty or are operating as intended. As shown at step 604 b, the process 604 includes verifying, by the controller 130, if a dosing system i.e., the reductant dosing injector 126 is faulty or not. If any of the sensors 132-138, or the dosing system i.e., reductant dosing injector 126 is faulty; the process 600 is aborted at step 606. Moreover, as process 600 is being aborted at step 606, the process 600 could also include issuing, by the controller 130 at a display device (not shown), an appropriate error code or signal depending on the type or location of fault i.e., with the sensors 132-138 or the reductant dosing injector 126. If the controller 130 verifies that the sensors 132-138 and the reductant dosing injector 126 are working properly, then the process 600 is continued to steps 608 and 610, wherein steps 608 and 610 may be carried out simultaneously, tandemly, or in any other manner known to persons skilled in the art.
At step 608, the process 600 includes determining, by the controller 130, whether the pre-fed Engine-out NOx map 148 a is calibrated using sensed parameters i.e., inputs from the first NOx sensor 132 as shown in FIG. 1. If so, the process 600 continues to step 612 where the pre-fed Engine-out NOx map 148 a is updated and an updated Engine-out NOx map 148 b is saved at the controller 130. If not, the process 600 continues to step 614 to calibrate the pre-fed Engine-out NOx map 148 a using the sensed parameters i.e., inputs from the first NOx sensor 132 as shown in FIG. 1. The process 600 may iterate in a closed loop fashion between steps 608 and 614 until the controller 130 determines that the pre-fed Engine-out NOx map 148 a at the controller 130 is updated using the sensed parameters i.e., inputs from the first NOx sensor 132 as shown in FIG. 1 and that the Engine-out NOx map currently stored at the controller 130 is indeed the updated Engine-out NOx map 148 b.
At step 610, the process 600 includes determining, by the controller 130, whether the SCR device 128 has been calibrated with a conversion factor for the SCR device 128 using sensed parameters i.e., input from sensors 132 and 134 shown in FIGS. 1 and 3; and is based at least in part, on the desired NOx conversion required from the SCR device 128. If no calibration has been done on the SCR device 128 to that effect, the process 600 proceeds to step 616, wherein the process 600 includes directing the controller 130 to verify if a SCR conversion factor has been determined for the SCR device 128. If so, then the process 600 includes directing the controller 130 at step 618 to incorporate such determined SCR conversion factor into an adaptive calibration process, where such determined SCR conversion factor is used to update the SCR conversion map 148 c pre-fed to the controller 130 and for storing such updated SCR conversion map 148 d at the controller 130. If it is verified by the controller 130 at step 616 that no SCR conversion factor has been determined for the given configuration and the operating condition of the engine 112, then the process 600 includes directing the controller 130 to determine a SCR conversion factor at step 616 itself and incorporate such determined SCR conversion factor at step 618 into the adaptive calibration process for obtaining the updated SCR conversion map 148 d. The process 600 may iterate in a closed loop fashion between steps 610-618 i.e., through step 616 until the controller 130 determines that the SCR conversion map 148 c pre-fed to the controller 130 has been updated using the sensed parameters i.e., inputs from sensors 132, 134 as shown in FIGS. 1 and 3; and that the SCR conversion map currently stored at the controller 130 is indeed the updated SCR conversion map 148 d.
It is also contemplated that in a particular embodiment of this disclosure, the controller 130 could also be configured to initiate step 610 upon completion of step 612 such that the steps 608 and 610 are carried out by the controller 130 in a tandem manner. Moreover, if at step 616, the controller 130, for reasons beyond the scope of this disclosure, is unable to determine a SCR conversion factor for the SCR device 128, then the process 600 may be aborted at step 620. Moreover, as process 600 is being aborted at step 620, the process 600 may further include issuing, by the controller 130 at a display device (not shown), an appropriate error code or signal depending on the type or location of an issue associated with the after-treatment system 110.
Further, if at step 610, the controller 130 determines that SCR conversion map stored therein is indeed the updated SCR conversion map 148 d, then the process 600 proceeds to step 622 where the process 600 includes directing the controller 130 to verify if a dosing offset value for the SCR device 128 and/or the reductant dosing injector 126 has been determined for incorporating such determined dosing offset value into the pre-fed NOx dosing map 148 g at the controller 130, for updating such pre-fed NOx dosing map 148 g, and for obtaining the updated NOx dosing map 148 h at the controller 130.
If at step 622, the controller 130 verifies that a dosing offset value for the SCR device 128 and/or the reductant dosing injector 126 has not yet been determined, then the process 600 directs the controller 130 at step 630 to run the NOx dosing calibration for determining a dosing offset value for the SCR device 128 and/or the reductant dosing injector 126 and for subsequently incorporating such determined dosing offset value into the pre-fed NOx dosing map 148 g at the controller 130, for updating such pre-fed NOx dosing map 148 g, and for obtaining the updated NOx dosing map 148 h at the controller 130.
However, if at step 622, the controller 130 verifies that a dosing offset value for the SCR device 128 and/or the reductant dosing injector 126 has been determined, then the process 600 proceeds from step 622 to step 624 where the process 600 includes directing the controller 130 if any additional test points are to be executed on the given configurations and operating conditions of the engine 112 and the after-treatment system 110. If so, then at step 624 itself, the process 600 directs the controller 130 to execute validation of the additional test points for the given configurations and operating conditions of the engine 112 and the after-treatment system 110.
Thereafter, the process 600 may direct the controller 130 at step 626 to save the updated Engine-out NOx map 148 b, the updated SCR conversion map 148 d, the updated maximum SCR capability map 148 f, and the updated NOx dosing map 148 h therein for controlling an operation of the after-treatment system 110, specifically—the SCR device 128 and the reductant dosing injector 126 of the after-treatment system 110 on the basis of the updated Engine-out NOx map 148 b, the updated SCR conversion map 148 d, the updated maximum SCR capability map 148 f, and the updated NOx dosing map 148 k More particularly, the process 600 includes directing the controller 130 to save the updated NOx dosing map 148 h for controlling an operation of the SCR device 128 and the reductant dosing injector 126 of the after-treatment system 110 on the basis of at least the updated NOx dosing map 148 h. Upon completion of step 626, the process 600 terminates at step 628.
The present disclosure (i.e., the emissions control system 114, method 700, any part(s) or function(s) thereof) may be implemented using hardware, software or a combination thereof, and may be implemented in one or more computer systems or other processing systems. However, the manipulations performed by the present disclosure were often referred to in terms such as monitoring, detecting, determining, comparing, verifying, or checking, which are commonly associated with mental operations performed by a human operator. No such capability of a human operator is necessary, or desirable in most cases, in any of the operations described herein, which form a part of the present disclosure. Rather, the operations are machine operations. Useful machines for performing the operations in the present disclosure may include general-purpose digital computers, specific application digital computers, or other similar devices known to persons skilled in the art.
FIG. 7 illustrates a method for calibrating an after-treatment system for e.g., after-treatment system 110 retrofitted onto a power source for e.g., the engine 112 disclosed herein. At step 702, the method 700 includes updating the Engine-out NOx map 148 a pre-fed to the controller 130 on the basis of an input obtained from the NOx sensor 132 disposed upstream of the SCR device 128 for a given configuration and operating condition of the engine 112. Additionally or optionally, prior to step 702, the method 700 could include verifying, by the controller 130, whether one or more sensors for e.g., sensors 132-138 associated with the after-treatment system 110 are operational. Further, prior to step 702, the method 700 could also include verifying, by the controller 130, whether a dosing system i.e., the reductant dosing injector 126 associated with the after-treatment system 110 is faulty or operating as intended.
At step 704, the method 700 further includes determining, using the controller 130, the conversion factor of the SCR device 128 by performing adaptive calibration of the SCR device 128. As disclosed earlier herein, the adaptive calibration performed on the SCR device 128 includes a comparison of a NOx conversion desired from the SCR device 128 with an actual NOx conversion of the SCR device 128 measured from inputs from the NOx sensors 132, 134 upstream and downstream of the SCR device 128 for the given operating condition of the engine 112.
At step 706, the method 700 includes updating, by the controller 130, a pre-fed SCR conversion map 148 d for the given SCR device 128 at the memory 152 on the basis of the determined conversion factor for the SCR device 128.
At step 708, the method 700 further includes determining, by the controller 130, a maximum conversion capability of the SCR device 128 for a given configurations and operating conditions of the engine 112 and the retrofitted after-treatment system 110 based on inputs from sensors 134 and 136 i.e., the second NOx sensor 134 and the NH₃sensor 136 for the given operating condition of the engine 112 and a pre-determined reductant dosing quantity corresponding to the given operating condition of the engine 112. As disclosed earlier herein, the pre-determined reductant dosing quantity for the given operating condition of the engine 112 is obtained from the pre-fed maximum SCR capability map 148 e stored at the controller 130. Thereafter, at step 710, the method 700 then includes updating the pre-fed maximum SCR capability map 148 e at the memory 152 by the controller 130 on the basis of the determined maximum conversion capability of the SCR device 128.
At step 712, the method 700 further includes determining, by the controller 130, a dosing offset value from comparison of the current reductant dosing quantity at the SCR device 128 with the pre-determined dosing quantity of the reductant required at the SCR device 128. Although such pre-determined dosing quantity corresponds to the NOx conversion and minimal NH₃slip desired from the SCR device 128 for the given configuration and operating condition of the engine 128, the pre-determined dosing quantity is obtained from the pre-fed NOx dosing map 148 g which is derived from operation of the engine 112 and the after-treatment system 110 under standardized, factory-set, or bench-running operating conditions.
At step 714, the method 700 then includes updating the pre-fed NOx dosing map 148 g for the SCR device 128 at the controller 130 on the basis of the determined dosing offset value for the SCR device 128 to obtain the updated NOx dosing map 148 h at the controller 130. Thereafter, at step 716, the method 700 further includes varying, with the help of the controller 130, a feed-forward reductant dosing quantity with the help of the reductant dosing injector 126 at the SCR device 128 during a subsequent operation of the engine 112 based on the updated NOx dosing map 148 h stored at the controller 130. Additionally or optionally, prior to step 716, the method 700 may further include storing the updated Engine-out NOx map 148 b, the updated SCR conversion map 148 d, the updated maximum SCR capability map 148 f, and the updated NOx dosing map 148 h by the controller 130 at the memory 152 associated with the controller 130.
Various embodiments disclosed herein are to be taken in the illustrative and explanatory sense, and should in no way be construed as limiting of the present disclosure. All joinder references (e.g., attached, affixed, coupled, connected, and the like) are only used to aid the reader's understanding of the present disclosure, and may not create limitations, particularly as to the position, orientation, or use of the systems and/or methods disclosed herein. Therefore, joinder references, if any, are to be construed broadly. Moreover, such joinder references do not necessarily infer that two elements are directly connected to each other.
Additionally, all numerical terms, such as, but not limited to, “first”. “second”, “third”, “primary”, “secondary” or any other ordinary and/or numerical terms, should also be taken only as identifiers, to assist the reader's understanding of the various elements, embodiments, variations and/or modifications of the present disclosure, and may not create any limitations, particularly as to the order, or preference, of any element, embodiment, variation and/or modification relative to, or over, another element, embodiment, variation and/or modification.
It is to be understood that individual features shown or described for one embodiment may be combined with individual features shown or described for another embodiment. The above described implementation does not in any way limit the scope of the present disclosure. Therefore, it is to be understood although some features are shown or described to illustrate the use of the present disclosure in the context of functional segments, such features may be omitted from the scope of the present disclosure without departing from the spirit of the present disclosure as defined in the appended claims.

INDUSTRIAL APPLICABILITY

The disclosure sets forth a control system and a method for commissioning operation of an after-treatment system retrofitted onto an engine. More particularly, the present disclosure relates to a control system and a method for calibrating the after-treatment system retrofitted onto the engine so as to optimize an operation of the retrofit after-treatment system wider varying operating conditions of the given engine and the after-treatment system configurations.
With use of embodiments disclosed herein, manufacturers of retrofit after-treatment systems can produce after-treatment systems that are configured to synchronize operation of the after-treatment system for a given configuration and operating conditions of the power source. Moreover, with implementation of embodiments disclosed herein, users of engines retro-fit with after-treatment systems can synergistically reduce undesirable emissions such as NOx emitted in the exhaust streams of the engines.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems, methods and processes without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.

Claims

What is claimed is:

1. A method of calibrating an after-treatment system retrofitted onto an engine, the method including:

updating an Engine-out NO_xmap pre-fed at a memory of a controller on the basis of an input obtained from a NOx sensor disposed upstream of a Selective Catalytic Reduction (SCR) device for a given configuration and operating condition of the engine;

determining, using the controller, a conversion factor of the SCR device by performing adaptive calibration of the SCR device, wherein the adaptive calibration includes a comparison of a NOx conversion desired from the SCR device with an actual NOx conversion of the SCR device measured from inputs from the NOx sensor upstream and a NOx sensor downstream of the SCR device for the given operating condition of the engine;

updating a SCR conversion map for the given SCR device at the memory of the controller on the basis of the determined conversion factor for the SCR device;

determining, by the controller, a maximum conversion capability of the SCR device for the given configurations of the engine and the retrofitted after-treatment system based on inputs from a sensor package including at least the NO_xsensor disposed downstream of the SCR device, the sensor package being configured to output at least an amount of Ammonia (NH₃) slip downstream of the SCR device;

obtaining, by the controller, a pre-determined reductant dosing quantity for the given operating condition of the engine from a maximum SCR capability map pre-fed at the memory of the controller;

updating the maximum SCR capability map at the memory of the controller on the basis of the determined maximum conversion capability of the SCR device;

determining, by the controller, an adjustment factor on the basis of a dosing offset value obtained from comparison between a current reductant dosing quantity at the SCR device with a pre-determined dosing quantity of the reductant required at the SCR device corresponding to the NOx conversion desired from the SCR device and minimal NH₃slip for the given configuration and operating condition of the engine;

updating a NOx dosing map for the SCR device at the memory by the controller based on the determined adjustment factor, the adjustment factor being obtained from the dosing offset value for the SCR device;

storing the updated Engine-out NO_xmap, the updated SCR conversion map, the maximum SCR capability map, and the NOx dosing map at the memory of the controller; and

varying, by the controller, a feed-forward reductant dosing quantity at the SCR device during a subsequent operation of the engine based on at least the updated NOx dosing map stored at the memory.