CN111219234B

CN111219234B - NOx level determination using reductant mass sensor

Info

Publication number: CN111219234B
Application number: CN202010098689.1A
Authority: CN
Inventors: 普里亚·奈克; 沙朗·S·索纳瓦尼; 纳西姆·卡勒德; 约瑟夫·A·哈德森
Original assignee: Cummins Emission Solutions Inc
Current assignee: Cummins Emission Solutions Inc
Priority date: 2016-03-09
Filing date: 2016-03-09
Publication date: 2022-12-02
Anticipated expiration: 2036-03-09
Also published as: CN111219234A; CN107178407B; CN107178407A

Abstract

The invention relates to NOx level determination using a reductant mass sensor. The aftertreatment system includes an SCR system, a reductant storage tank, a reductant introduction assembly fluidly coupled to the reductant storage tank and the SCR system and configured to introduce reductant into the SCR system. The aftertreatment system also includes a reductant mass sensor. The controller is communicatively coupled to the reductant mass sensor. The controller is configured to interpret an output signal from the reductant mass sensor. The output signal indicates reductant mass. The controller uses the reductant mass to determine an outlet NOx amount in the exhaust downstream of the SCR system. The controller also determines whether the outlet NOx amount exceeds a predetermined threshold. In response to the outlet NOx amount exceeding the predetermined threshold, the controller indicates to the user that the outlet NOx amount exceeds the predetermined threshold.

Description

NOx level determination using reductant mass sensor

The present application is a divisional application filed on 2016, 3, 9, under the application number 201610131327.1 entitled "NOx level determination using a reductant mass sensor".

Technical Field

The present disclosure relates generally to aftertreatment systems for Internal Combustion (IC) engines.

Background

Exhaust aftertreatment systems are used to receive and treat exhaust gas produced by an engine, such as an IC engine. Conventional exhaust aftertreatment systems include any of several different components that reduce the level of harmful exhaust emissions present in the exhaust gas. For example, certain exhaust aftertreatment systems for diesel-powered IC engines include a Selective Catalytic Reduction (SCR) system, which includes a catalyst that is activated by hydrogenFormulated to be in ammonia (NH) ₃ ) In the presence of NOx (with a certain proportion of NO and NO) ₂ ) Conversion to harmless nitrogen (N) ₂ ) And water vapor (H) ₂ O). The reductant is often introduced into an exhaust conduit that delivers the exhaust gas to the SCR system and/or other components of the aftertreatment system.

Emission standards continue to become more stringent for limiting the amount of NOx gases included in the exhaust emitted from the aftertreatment system. This is especially true in emerging markets such as india and china. For example, the Bharat stage IV (BS 4) emissions regulations based on European standards are becoming increasingly more stringent in the amount of NOx emissions that may be included in the exhaust gas emitted from an aftertreatment system. Therefore, stringent monitoring of the amount of NOx emitted in exhaust gases, such as exhaust gases from gasoline and/or diesel engines, is desirable.

Disclosure of Invention

Embodiments described herein generally relate to systems and methods for determining an outlet NOx amount at an outlet of an aftertreatment system without using a physical NOx sensor at the outlet. Various embodiments described herein relate to determining an outlet NOx amount using a reductant mass sensor located within a reductant storage tank and/or integrated into a reductant introduction assembly such that the aftertreatment system does not include a physical NOx sensor at an outlet of the aftertreatment system.

In a first set of embodiments, the following is provided:

1) An aftertreatment system includes an SCR system including a catalyst configured to decompose a component of an exhaust gas flowing therethrough. The aftertreatment system also includes a reductant storage tank. The reductant introduction assembly is fluidly coupled to the reductant storage tank and the SCR system and is configured to introduce reductant into the SCR system. The aftertreatment system also includes a reductant mass sensor. The controller is communicatively coupled to the reductant mass sensor. The controller is configured to interpret an output signal from the reductant mass sensor. The output signal is indicative of reductant mass. The controller uses the reductant mass to determine an outlet NOx amount in the exhaust downstream of the SCR system. The controller also determines whether the outlet NOx amount exceeds a predetermined threshold. In response to the outlet NOx amount exceeding the predetermined threshold, the controller indicates to the user that the outlet NOx amount exceeds the predetermined threshold.

2) The aftertreatment system of clause 1), wherein the reductant mass sensor is operatively coupled to the reductant storage tank such that the output signal is indicative of a mass of reductant contained within the reductant storage tank.

3) The aftertreatment system of clause 1), wherein the reductant mass sensor is located downstream of the reductant introduction assembly and upstream of the selective catalytic reduction system such that the output signal is indicative of a mass of the reductant when the reductant is introduced into the selective catalytic reduction system.

4) The aftertreatment system of item 1), further comprising: a NOx sensor located upstream of the selective catalytic reduction system.

5) The aftertreatment system of item 1), wherein the controller is further configured to: interpreting a NOx output signal from the NOx sensor, the NOx output signal indicating an amount of inlet NOx upstream of the selective catalytic reduction system; and determining the outlet NOx amount using the reductant mass and the inlet NOx amount.

6) The aftertreatment system of clause 1), wherein the aftertreatment system does not include an outlet NOx sensor downstream of the selective catalytic reduction system.

7) The aftertreatment system of item 1), further comprising: a differential pressure sensor positioned across the selective catalytic reduction system.

8) The aftertreatment system of item 1), further comprising: at least one of an oxidation catalyst and a filter located upstream of the selective catalytic reduction system.

9) The aftertreatment system of item 1), further comprising: a NOx absorber catalyst located upstream of the selective catalytic reduction system.

10 The aftertreatment system of item 1), wherein the controller is further configured to: in response to the outlet NOx amount exceeding the predetermined threshold, determining that the reductant is diluted above a predetermined dilution threshold, and indicating to a user to change the reductant.

In another set of embodiments, the following is provided:

11 An apparatus for determining an amount of outlet NOx in exhaust gas downstream of an SCR system included in an aftertreatment system includes a reductant mass sensor operatively coupled to the aftertreatment system, the aftertreatment system further including a reductant storage tank and a reductant introduction assembly for introducing reductant into the SCR system. The controller is communicatively coupled to the reductant mass sensor. The controller is configured to interpret an output signal from the reductant mass sensor. The output signal is indicative of reductant mass. The controller uses the reductant mass to determine an outlet NOx amount in the exhaust downstream of the SCR system. The controller also determines whether the outlet NOx amount exceeds a predetermined threshold. In response to the outlet NOx amount exceeding the predetermined threshold, the controller indicates to the user that the outlet NOx amount exceeds the predetermined threshold.

12 The device of clause 11), wherein the reductant mass sensor is configured to be operatively coupled to the reductant storage tank such that the output signal is indicative of a mass of the reductant contained within the reductant storage tank.

13 The apparatus of clause 11), wherein the reductant mass sensor is configured to be located downstream of the reductant introduction assembly and upstream of the selective catalytic reduction system such that the output signal is indicative of a mass of the reductant when the reductant is introduced into the selective catalytic reduction system.

14 The apparatus of clause 12) or 13), further comprising: a NOx sensor configured to be located upstream of the selective catalytic reduction system to measure an initial amount of NOx upstream of the selective catalytic reduction system.

15 The apparatus of clause 14), wherein the controller is further configured to: interpreting a NOx output signal from the NOx sensor, the NOx output signal indicating an amount of inlet NOx upstream of the selective catalytic reduction system; and determining the outlet NOx amount using the reductant mass and the inlet NOx amount.

16 The apparatus of item 15), further comprising: a differential pressure sensor configured to be positioned across the selective catalytic reduction system to determine a differential pressure across the selective catalytic reduction system, wherein the controller is further configured to: determining the outlet NOx amount using the reductant mass and the differential pressure.

17 The apparatus of item 16), further comprising: a first temperature sensor configured to be located upstream of the selective catalytic reduction system to determine a first temperature of the exhaust gas entering the selective catalytic reduction system, and a second temperature sensor configured to be located downstream of the selective catalytic reduction system to determine a second temperature of the exhaust gas exiting the selective catalytic reduction system, wherein the controller is further configured to: determining the outlet NOx amount using the reductant mass and at least one of the first and second temperatures of exhaust gas.

18 The apparatus of clause 17), wherein the controller is further configured to: in response to the outlet NOx amount exceeding the predetermined threshold, determining that the reductant is diluted above a predetermined dilution threshold, and indicating to a user to change the reductant.

In yet another set of embodiments, the following is provided:

19 A control circuit including a controller configured to communicatively couple to a reductant mass sensor of an aftertreatment system including an SCR system for reducing a constituent of an exhaust gas, a reductant storage tank, a reductant introduction assembly, and the reductant mass sensor. The controller includes a reductant quality determination circuit configured to interpret an output signal from a reductant quality sensor. The output signal indicates reductant mass. The controller also includes an outlet NOx determination circuit configured to determine an outlet NOx amount in the exhaust gas downstream of the SCR system using the reductant mass. The outlet NOx determination circuit determines whether the outlet NOx amount exceeds a predetermined threshold. In response to the outlet NOx amount exceeding the predetermined threshold, the outlet NOx determination circuit indicates to a user that the outlet NOx amount exceeds the predetermined threshold.

20 The control circuit of clause 19), wherein the reductant mass sensor is coupled to the reductant storage tank such that the output signal is indicative of a mass of the reductant contained within the reductant storage tank.

21 The control circuit of clause 19), wherein the reductant mass sensor is located downstream of the reductant introduction assembly and upstream of the selective catalytic reduction system such that the output signal is indicative of a mass of the reductant when the reductant is introduced into the selective catalytic reduction system.

22 The control circuit of item 19), further comprising: an inlet NOx amount determination circuit configured to interpret a NOx output signal from a NOx sensor located upstream of the selective catalytic reduction system, the NOx output signal indicative of an inlet NOx amount upstream of the selective catalytic reduction system, and wherein the outlet NOx amount determination circuit is further configured to determine the outlet NOx amount using the reductant mass and the inlet NOx amount.

23 The control circuit of item 19), further comprising: pressure determination circuitry configured to interpret an output pressure signal from a differential pressure sensor positioned across the selective catalytic reduction system to determine a differential pressure across the selective catalytic reduction system, and wherein the outlet NOx amount determination circuitry is further configured to determine the outlet NOx amount using the reductant mass and the differential pressure.

24 The control circuit of item 19), further comprising: a temperature determination circuit configured to interpret a first temperature signal from a first temperature sensor located upstream of the selective catalytic reduction system to determine a first temperature of exhaust gas entering the selective catalytic reduction system, and wherein the outlet NOx amount determination circuit is further configured to determine the outlet NOx amount using the reductant mass and the first temperature of exhaust gas.

25 The control circuit of clause 24), wherein the temperature determination circuit is further configured to interpret a second temperature signal from a second temperature sensor located downstream of the selective catalytic reduction system to determine a second temperature of the exhaust gas exiting the selective catalytic reduction system, and wherein the outlet NOx amount determination circuit is further configured to determine the outlet NOx amount using the second temperature of the exhaust gas.

It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (assuming such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

Drawings

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several implementations in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

FIG. 1 is a schematic diagram of an aftertreatment system, according to an embodiment.

FIG. 2 is a schematic block diagram of example control circuitry that may be included in the aftertreatment system of FIG. 1.

FIG. 3 is a schematic view of another embodiment of an aftertreatment system.

FIG. 4 is a schematic view of yet another embodiment of an aftertreatment system.

FIG. 5 is a schematic view of yet another embodiment of an aftertreatment system.

FIG. 6 is a schematic flow chart diagram of an embodiment of a method for determining an outlet NOx amount using a reductant mass determined by a reductant mass sensor.

FIG. 7 is a schematic block diagram of another embodiment of a computing device that may be used as the controller of FIG. 1 and/or FIG. 2.

Throughout the following detailed description, reference is made to the accompanying drawings. In the drawings, like reference numerals generally identify like parts, unless context dictates otherwise. The illustrative implementations described in the detailed description, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Detailed Description

Emission standards continue to become more stringent for limiting the amount of NOx gases included in the exhaust emitted from the aftertreatment system. Therefore, stringent monitoring of the amount of NOx emitted in exhaust gases, such as exhaust gases from gasoline and/or diesel engines, is desirable.

Many conventional aftertreatment systems typically include a physical NOx sensor located at the outlet or tailpipe of the aftertreatment system. The output from such a physical NOx sensor corresponds to the amount of NOx in the exhaust gas (e.g., diesel exhaust gas) emitted from the aftertreatment system into the environment and is typically used to determine the performance of the aftertreatment system (e.g., the catalytic conversion efficiency of an SCR system included in the aftertreatment system). However, such physical NOx sensors are expensive and prone to failure, which increases maintenance costs. In particular, in developing countries, installation and maintenance costs of physical NOx sensors can significantly impact the overall cost burden on consumers, such as vehicle owners.

Moreover, aftertreatment systems associated with diesel engines typically include a reductant introduction assembly configured to introduce a liquid reductant into the aftertreatment system. The reductant promotes decomposition of components (e.g., NOx gases included in the exhaust gas) by an SCR system included in the aftertreatment system. In some examples, the reducing agent solution may not have the recommended concentration, e.g., the reducing agent solution may be too dilute. Such non-standard reductant solutions will also result in a decrease in the efficiency of the SCR system, resulting in an increase in NOx emissions. This is particularly true in developing countries where cost reductions and the availability of counterfeit reductant solutions can lead to increased NOx emissions.

Various embodiments of the systems and methods described herein for determining whether an amount of outlet NOx included in exhaust emitted from an aftertreatment system is within a predetermined threshold may provide benefits, such as: (1) Determining whether the outlet NOx amount exceeds a predetermined threshold, which may correspond to an emission standard using a reductant determined by a reductant mass sensor; (2) Allowing removal of the physical NOx sensor from the outlet of the aftertreatment system; (3) Preventing unnecessary maintenance of the aftertreatment system by diagnosing the presence of an improperly diluted reductant in the aftertreatment system; and (4) significantly reduce the assembly and maintenance costs of the aftertreatment system by allowing the elimination of the physical NOx sensor from the aftertreatment outlet.

Fig. 1 is a schematic diagram of an aftertreatment system 100, according to an embodiment. The aftertreatment system 100 may be fluidly coupled to an engine and configured to decompose a component (e.g., NOx gases) included in an exhaust gas produced by the engine. The engine may include an IC engine operable on diesel, gasoline, natural gas, biodiesel, ethanol, liquefied Petroleum Gas (LPG), or any other fuel source. The aftertreatment system 100 includes an SCR system 150, a reductant storage tank 110, a first reductant mass sensor 112, an optional second reductant mass sensor 124, a reductant introduction assembly 120, a dosing valve 122, and a controller 170.

The aftertreatment system 100 includes an inlet duct 102 configured to receive exhaust gas from the SCR system 150 and an outlet duct 104 that discharges treated exhaust gas into the environment. The first temperature sensor 148 is located upstream of the SCR system 150, while the second temperature sensor 152 is located downstream of the SCR system 150. The first and

second temperature sensors

148, 152 are configured to determine a first temperature of the exhaust gas entering the SCR system 150 and a second temperature of the exhaust gas after passing through the SCR system 150, respectively.

The NOx sensor 103 is located upstream of the SCR system 150 near the inlet of the inlet conduit 102 and is configured to determine an inlet NOx amount of NOx gases included in the exhaust gas entering the aftertreatment system 100. The SCR system 150 is located between the inlet duct 102 and the outlet duct 104 (e.g., within a housing of the aftertreatment system).

In some embodiments, the NOx sensor 103 may comprise a physical NOx sensor. In other embodiments, the NOx sensor 103 may include a virtual NOx sensor configured to determine the amount of inlet NOx based on one or more operating parameters of the engine generating the exhaust gas (e.g., air/fuel ratio, compression ratio, combustion temperature, exhaust gas pressure, etc.). For example, controller 170 may include a model, look-up table, algorithm, and/or equation configured to determine the amount of inlet NOx using one or more operating parameters of the engine that produces exhaust.

The SCR system 150 includes one or more catalysts formulated to selectively decompose components of the exhaust gas. Any suitable catalyst may be used, such as a catalyst based on platinum, palladium, rhodium, cerium, iron, manganese, copper, vanadium, any other suitable catalyst, or a combination thereof. The catalyst may be disposed on a suitable substrate such as a ceramic (cordierite) or metallic (e.g., chrome aluminum cobalt refractory steel) monolithic core that may, for example, define a honeycomb structure. The coating can also be used as a support material for the catalyst. For example, such coating materials may include alumina, titania, silica, any other suitable coating material, or combinations thereof. Exhaust gas (e.g., diesel exhaust) may flow over and around the catalyst such that any NOx gases included in the exhaust gas are further reduced to produce an exhaust gas that is substantially free of carbon monoxide and NOx gases.

The reductant storage tank 110 (also referred to herein as "tank 110") is configured to store a reductant. The reductant is formulated to promote decomposition of a component of the exhaust gas (e.g., NOx gases included in the exhaust gas). Any suitable reducing agent may be used. In some embodiments, the exhaust gas may comprise diesel exhaust gas, and the reductant may comprise diesel exhaust fluid (diesel exhaust fluid). The diesel exhaust fluid may include urea, an aqueous solution of urea, or include ammonia, byproducts, or any other diesel exhaust fluid as is known in the art (e.g., under the name

Diesel exhaust treatment fluids sold below).

For example, the reductant may include an aqueous urea solution having a particular ratio of urea to water. In a particular embodiment, the reductant may include an aqueous urea solution including 32.5% urea by volume and 67.5% deionized water by volume. Higher concentrations of water in the reducing agent (e.g., greater than 67.5%) may over-dilute the reducing agent, resulting in an under-calibrated reducing agent solution. This results in a decrease in the catalytic conversion efficiency of the SCR system 150, which may increase the outlet NOx amount of the exhaust gas after passing through the SCR system 150.

The reductant introduction assembly 120 is fluidly coupled to the tank 110. The reductant introduction assembly 120 is configured to selectively inject or otherwise introduce reductant into the SCR system 150 or a mixer (not shown) upstream thereof (e.g., into the inlet conduit 102) or upstream of the SCR system 150. For example, the reductant introduction assembly 120 may include a pump, valve, conduit, etc. configured to deliver reductant from the tank 110 to the SCR system 150.

In various implementations, the reductant introduction assembly 120 may also include a dosing valve 122 located within a reductant delivery line for delivering reductant from the reductant introduction assembly 120 to the SCR system 150. The dosing valve 122 may include any suitable valve, such as a butterfly valve, a gate valve, a check valve (e.g., a swashplate check valve, a wobble check valve, a shaft check valve, etc.), a ball valve, a spring valve, an air-assisted injector, a solenoid valve, or any other suitable valve. The dosing valve 122 may be selectively opened to introduce a predetermined amount of reductant into or upstream of the SCR system 150 during a predetermined time.

A reductant quality sensor 112 is operatively coupled to the tank 110 and is configured to determine a quality of reductant contained within the tank 110. Reductant mass sensor 112 may include, for example, an ultrasonic sensor (e.g., an ultrasonic sensor) or any other suitable reductant mass sensor. The reductant quality sensor 112 generates an output signal indicative of a quality of the reductant contained within the tank 110.

The output signal may indicate a dilution ratio of the reducing agent to the dilution solution (e.g., a ratio of urea to water in the aqueous reducing agent). The reductant mass sensor 112 may include a quantitative sensor such that the output signal is indicative of a ratio of reductant to diluent solution (e.g., a quantitative ratio of urea to water). In other implementations, reductant quality sensor 112 may include a qualitative sensor such that the output signal indicates whether the reductant quality is below a quality threshold (e.g., the reductant is too lean).

In some embodiments, the aftertreatment system 100 may optionally include a second reductant mass sensor 124 located downstream of the reductant introduction assembly 120 (e.g., downstream of the valve 122) and upstream of the SCR system 150 (e.g., operatively coupled to a reductant delivery line configured to introduce reductant into the SCR system 150). The second reductant mass sensor 124 is configured to determine a mass of reductant prior to introduction to the SCR system 150. The second reductant mass sensor 124 may be substantially similar to the first reductant mass sensor 112. In some embodiments, aftertreatment system 100 may include only second reductant mass sensor 124, such that first reductant mass sensor 112 is not included.

Although shown as including the SCR system 150, the aftertreatment system 100 may also include other components, such as one or more flow mixers, particulate filters, oxidation catalysts (e.g., diesel oxidation catalysts or ammonia oxidation catalysts), oxygen sensors, ammonia sensors, and/or other components.

Controller 170 is communicatively coupled to reductant mass sensor 112 and/or second reductant mass sensor 124. Controller 170 may include any suitable controller, for example, a computing device 630 as described in detail herein. Controller 170 is configured to interpret output signals from first reductant mass sensor 112 and/or second reductant mass sensor 124. As previously described, the output signal is indicative of reductant quality. The controller 170 uses the reductant mass to determine an outlet NOx amount in the exhaust downstream of the SCR system 150.

Controller 170 may include an algorithm, look-up table, or equation configured to correlate reductant mass with the determined outlet NOx amount. Controller 170 may determine an absolute value of the outlet NOx amount. In some embodiments, controller 170 may determine from the reductant mass that the outlet NOx amount is within an expected range. Controller 170 determines whether the outlet NOx amount exceeds a predetermined threshold. In response to the outlet NOx amount exceeding the predetermined threshold, controller 170 indicates to the user that the outlet NOx amount exceeds the predetermined threshold.

In some embodiments, controller 170 determines that the reductant is diluted above a predetermined dilution threshold in response to the outlet NOx amount exceeding a predetermined threshold. The controller 170 thus instructs the user to change the reductant. For example, a diluted reductant solution having a higher percentage of water to reductant than a predetermined dilution threshold will reduce the catalytic efficiency of the SCR system 150. This may cause an increase in the amount of outlet NOx included in the exhaust gas discharged from the aftertreatment system 100 via the outlet. The increase in the amount of outlet NOx may cause the amount of outlet NOx to exceed a predetermined threshold.

The predetermined threshold may, for example, correspond to a maximum allowable amount of NOx that may be emitted by the aftertreatment system during operation (e.g., corresponding to NOx emission standards). Controller 170 may thus determine an absolute value or expected range of outlet NOx amounts and determine whether the outlet NOx amount or otherwise the range of outlet NOx amounts exceeds a predetermined threshold. If the outlet NOx amount exceeds the predetermined threshold, controller 170 indicates to the user that the outlet NOx amount exceeds the predetermined threshold. Accordingly, a user may be alerted to the presence of an under-standard reductant within tank 110 (or introduced into SCR system 150). In this manner, the outlet NOx amount is determined via the output signal from the reductant mass sensor such that the aftertreatment system 100 does not include an outlet NOx sensor downstream of the SCR system 150 for determining the outlet NOx amount. This can provide significant cost savings as well as reduced maintenance costs, as described herein.

In particular embodiments, controller 170 may be included in the control circuitry. For example, fig. 2 is a schematic block diagram of a control circuit 171 including a controller 170 according to an embodiment. The controller 170 includes a processor 172, a memory 174 or other computer readable medium, a transceiver 178, and optionally a sensor 176. It should be understood that the controller 170 illustrates only one embodiment of the controller 170, and that any other controller capable of performing the operations described herein may be used.

Processor 172 may include a microprocessor, a Programmable Logic Controller (PLC) chip, an ASIC chip, or any other suitable processor. The processor 172 is in communication with the memory 174 and is configured to execute instructions, algorithms, commands, or other programs stored in the memory 174.

Memory 174 includes any memory and/or storage components discussed herein. For example, memory 174 may include RAM and/or cache memory for processor 172. Memory 174 may also include one or more storage devices (e.g., hard drives, flash memory, computer-readable media, etc.) local or remote to device controller 170. The memory 174 is configured to store a look-up table, algorithm, or instructions. For example, the memory 174 includes a reductant mass determination circuit 174a. Reductant quality determination circuit 174a may be configured to receive output signals from reductant quality sensor 112 and/or reductant quality sensor 124 (e.g., via sensor 176). The reductant mass determination circuit 174a interprets the output signal from the reductant mass sensor 112 and/or the second reductant mass sensor 124 (indicated as the reductant mass signal in fig. 2) indicative of reductant mass and determines reductant mass therefrom.

The memory 174 also includes an outlet NOx amount determination circuit 174b configured to receive information regarding the reductant mass from the reductant mass determination module 174a and determine an outlet NOx amount in the exhaust downstream of the SCR system 150 using the reductant mass. The outlet NOx amount determination circuit 174b determines whether the outlet NOx amount exceeds a predetermined threshold, for example, a maximum allowable limit value of the outlet NOx amount. In response to the outlet NOx amount exceeding the predetermined threshold, the outlet NOx amount determination circuit 174b indicates to the user that the outlet NOx amount exceeds the predetermined threshold.

In some embodiments, memory 174 also includes an inlet NOx amount determination circuit 174c. The inlet NOx amount determination circuit 174c is configured to interpret a NOx output signal from the NOx sensor 103 located upstream of the SCR system 150 (e.g., received via the sensor 150). The NOx output signal indicates an amount of inlet NOx upstream of the SCR system 150. In such embodiments, the outlet NOx amount determination circuit 174b may be further configured to determine the outlet NOx amount using the reductant mass signal and the inlet NOx amount.

In other embodiments, the memory 174 may also include a pressure determination circuit 174d. The pressure determination circuitry 174d is configured to interpret a pressure signal (e.g., received via sensor 150) from a differential pressure sensor, or any other pressure sensor, that may be located across the SCR system (e.g., differential pressure sensor 248 included in the aftertreatment system 200 of fig. 3). The pressure signal indicates a differential pressure or pressure drop across the SCR system 150. The pressure determination circuit 174d determines a differential pressure using the pressure signal. In some embodiments, the outlet NOx amount determination circuit 174b may also be configured to determine the outlet NOx amount using the reductant mass and the differential pressure.

In still other embodiments, the memory 174 further includes a temperature determination circuit 174e configured to interpret a first temperature signal (e.g., received via the sensor 150) from a first temperature sensor 148 located upstream of the SCR system 150. The first temperature signal is indicative of a first temperature of the exhaust gas upstream of the SCR system 150. The temperature determination circuit 174e determines a first temperature of the exhaust gas entering the SCR system 150 using the first temperature signal. The outlet NOx amount determination circuit 174b is further configured to determine an outlet NOx amount using the reductant mass and the first temperature.

In some embodiments, the temperature determination circuit 174e is further configured to interpret a second temperature signal from a second temperature sensor 152 located downstream of the SCR system 150. The second temperature is indicative of a second temperature of the exhaust gas downstream of the SCR system. In such embodiments, the outlet NOx amount determination circuit 174b may also be configured to determine the outlet NOx amount using the second temperature.

The controller 170 also includes a transceiver 178 configured to generate an indicator signal (e.g., current or voltage) configured to indicate to a user that the outlet NOx amount exceeds a predetermined threshold. For example, the indicator signal may generate a fault code or illuminate a fault indicator light (MIL), such as located in a dashboard or system of a vehicle that includes the aftertreatment system 100.

FIG. 3 is a schematic diagram of an aftertreatment system 200 according to another embodiment. The aftertreatment system 200 includes an SCR system 205 located between the inlet duct 202 and the outlet duct 204. The SCR system 250 may be substantially similar to the SCR system 150 and, therefore, is not described in greater detail herein. A NOx sensor 203 is operatively coupled to inlet conduit 202 to measure an amount of inlet NOx included in the exhaust gas entering inlet conduit 202. However, the aftertreatment system does not include an outlet NOx sensor located on the outlet conduit 204.

The aftertreatment system 200 also includes a reductant storage tank 210, a reductant introduction assembly 220 for introducing reductant into the inlet 202 upstream of the SCR system 250 or otherwise into the SCR system 250, and a valve 222. The reductant storage tank 210, the reductant introduction assembly 220, and the valve 222 may be substantially similar in structure and function to the reductant storage tank 110, the reductant introduction assembly 120, and the valve 122, respectively, and therefore will not be described in greater detail herein.

A first reductant mass sensor 212 is operatively coupled to the reductant storage tank 210 to determine a mass of reductant contained therein. In addition to or in lieu of first reductant mass sensor 212, second reductant mass sensor 224 may also be located within a reductant delivery line fluidly coupling valve 222 to inlet 202. First reductant mass sensor 212 and second reductant mass sensor 224 are substantially similar to first reductant mass sensor 112 and second reductant mass sensor 124, and therefore are not described in greater detail herein.

A differential pressure sensor 248 is positioned across the SCR system 250. The differential pressure sensor 248 is configured to measure a differential pressure across the SCR system 250. The differential pressure may indicate an amount of "plugging" of the SCR system 250 due to particulate matter accumulating therein. Because clogging can also affect the performance of the SCR system 250, the differential pressure sensor may provide some indication of the amount of outlet NOx.

Controller 270 is communicatively coupled to NOx sensor 203, first reductant mass sensor 212, optionally second reductant mass sensor 224, and differential pressure sensor 248. Controller 270 may be substantially similar to controller 170. Controller 270 is configured to interpret output signals from first reductant mass sensor 212 and/or second reductant mass sensor 224 indicative of reductant mass. Further, the controller 270 is configured to interpret an output pressure signal from the differential pressure sensor 248 indicative of a differential pressure across the SCR system 250.

Controller 270 uses the reductant mass and differential pressure to determine an outlet NOx amount in the exhaust downstream of SCR system 250. Controller 270 determines whether the outlet NOx amount exceeds a predetermined threshold, such as a maximum allowable amount of NOx. If the outlet NOx amount exceeds the predetermined threshold, controller 270 indicates to the user that the outlet NOx amount exceeds the predetermined threshold.

FIG. 4 is a schematic diagram of an aftertreatment system 300a according to yet another embodiment. The aftertreatment system 300a includes an SCR system 350 located downstream of the inlet duct 302 and upstream of the outlet duct 304 of the aftertreatment system 300 a. The SCR system 350 may be substantially similar to the SCR system 150, and thus, is not described in greater detail herein. A NOx sensor 303 is operatively coupled to inlet conduit 302 to measure an amount of inlet NOx included in the exhaust gas entering inlet conduit 302. However, aftertreatment system 300a does not include an outlet NOx sensor located on outlet conduit 304.

An oxidation catalyst 330 is located downstream of the inlet duct 302 and upstream of the SCR system 350. The oxidation catalyst 330 may include, for example, a diesel oxidation catalyst configured to decompose carbon monoxide (CO) or unburned hydrocarbons included in exhaust gas (e.g., diesel gas) passing therethrough. In some embodiments, the oxidation catalyst 330 may include a regenerated oxidation catalyst configured to be regenerated via the introduction of fuel (e.g., diesel) therein.

The filter 340 is located downstream of the oxidation catalyst 330 and upstream of the SCR system 350. Filter 340 is configured to filter particulate matter (e.g., carbon particles, soot, dust, etc.) that is discharged into the environment. The filter 340 may have any suitable pore size, such as about 10 microns, about 5 microns, or about 1 micron. In some embodiments, filter 340 may be catalyzed. In particular embodiments, filter 340 may include a partial filter.

In various embodiments, a nox absorber catalyst 360 may be located upstream of the SCR system 350 in addition to or in place of the oxidation catalyst 330 and the filter 340. For example, FIG. 5 is a schematic diagram of an aftertreatment system 300b according to another embodiment. Aftertreatment system 300b is the same as aftertreatment system 300a of fig. 4, except that a NOx absorber catalyst 360 is located upstream of the SCR system 350 instead of the oxidation catalyst 330 and the filter 340.

The NOx absorber catalyst 360 is configured to reduce the amount of NOx included in the exhaust gas emitted from the engine (e.g., a lean-burn diesel engine). In some embodiments, the NOx absorber catalyst 360 may include a catalyst configured to absorb NO or NO included in the exhaust gas ₂ The zeolite catalyst of (1). Once the NOx absorber catalyst 360 absorbs NO and/or NO ₂ Hydrocarbons (e.g., diesel) may be introduced into the NOx absorber catalyst 360 to regenerate the NOx absorber catalyst 360.

The aftertreatment system 300a/b also includes a reductant storage tank 310, a reductant introduction assembly 320 for introducing reductant upstream of the SCR system 350 or otherwise within the SCR system 350, and a valve 322. The reductant storage tank 310, the reductant introduction assembly 320, and the valve 322 may be substantially similar in structure and function to the reductant storage tank 110, the reductant introduction assembly 120, and the valve 122, respectively, and therefore will not be described in further detail herein.

The first reductant mass sensor 312 is operatively coupled to the reductant storage tank 310 to determine a mass of reductant contained therein. In addition to or in lieu of the first reductant mass sensor 312, a second reductant mass sensor 324 may also be located within the reductant delivery line fluidly coupling the valve 322 to the inlet 302. First reductant mass sensor 312 and second reductant mass sensor 324 are substantially similar to first reductant mass sensor 112 and second reductant mass sensor 124, and therefore are not described in greater detail herein.

The first temperature sensor 348 is located upstream of the SCR system 350 and is configured to measure a first temperature of the exhaust gas upstream of the SCR system 350. The second temperature sensor 352 is located downstream of the SCR system 350 and is configured to measure a second temperature of the exhaust gas downstream of the SCR system 350.

Controller 370 is communicatively coupled to NOx sensor 303, first reductant mass sensor 312, optionally second reductant mass sensor 324, first temperature sensor 348, and second temperature sensor 352. Controller 370 may be substantially similar to controller 170. Controller 370 is configured to interpret output signals from first reductant mass sensor 312 and/or second reductant mass sensor 324 indicative of reductant mass. Further, the controller 370 may be configured to interpret a first temperature signal from the first temperature sensor 348 indicative of a first temperature of the exhaust gas. The controller 370 may also be configured to interpret a second temperature signal from the second temperature sensor 352 indicative of a second temperature of the exhaust gas.

Controller 370 uses the reductant mass, the first temperature, and/or the second temperature to determine an outlet NOx amount in the exhaust downstream of SCR system 350. Controller 370 determines whether the outlet NOx amount exceeds a predetermined threshold, such as a maximum allowable amount of NOx. If the outlet NOx amount exceeds the predetermined threshold, controller 370 indicates to the user that the outlet NOx amount exceeds the predetermined threshold.

FIG. 6 is a schematic flow chart of a method 500 for determining an amount of outlet NOx included in exhaust gas flowing through an aftertreatment system (e.g., aftertreatment system 100/200/300 a/b). The aftertreatment system includes at least an SCR system (e.g., SCR system 150/250/350), a reductant introduction assembly (e.g., reductant introduction assembly 120/220/320), a reductant storage tank (e.g., tank 110/210/310) containing reductant, and a reductant quality sensor (e.g., first reductant quality sensor 112/212/312 and/or second reductant quality sensor 124/224/324).

The method 500 includes flowing exhaust through an aftertreatment system at 502. For example, diesel exhaust produced by a diesel engine is introduced into the inlet conduit 102/202/302 of the aftertreatment system 100/200/300a/b such that the exhaust flows therethrough. The reductant is introduced into the SCR system 504. For example, the reductant introduction assembly 120/220/320 introduces reductant from the reductant storage tank 110/210/310 into the SCR system 150/250/350.

At 506, reductant mass is determined. For example, first reductant mass sensor 112/212/312 and/or second reductant mass sensor 124/224/324 generate output signals that are interpreted by controller 170/270/370 to determine reductant mass. At 508, an outlet NOx amount in the exhaust gas downstream of the SCR system is determined using the reductant mass. For example, the controller 170/270/370 uses the reductant mass to determine the outlet NOx amount. In various implementations, the outlet NOx amount may be determined using the reductant mass and at least one of a differential pressure across the SCR system, a first temperature upstream of the SCR system (e.g., SCR system 150/250/350), and a second temperature downstream of the SCR system.

At 510 it is determined whether the outlet NOx amount exceeds a predetermined threshold. For example, controller 170/270/370 then compares the outlet NOx amount to a predetermined threshold (e.g., a maximum amount of NOx allowable in exhaust gas emitted from aftertreatment system 100/200/300 a/b). If operation 510 is false, the method 500 returns to operation 506. However, if operation 510 is true, i.e., the outlet NOx amount exceeds the predetermined threshold, then the user is indicated that the outlet NOx amount exceeds the predetermined threshold. For example, the controller 170/270/370 may generate a fault code or brighten the MILs.

In some embodiments, the controller 170/270/370, the control circuit 171, or any controller or control circuit described herein may include a system computer that includes a device or system (e.g., a wheel, an engine, or a generator set, etc.) of the aftertreatment system 100. For example, fig. 7 is a block diagram of a computing device 630 in accordance with an illustrative implementation. Computing device 630 may be used to perform any of the methods or processes described herein, such as method 500. In some implementations, the controller 170 can include a computing device 630. Computing device 630 includes a bus 632 or other communication means for communicating information. Computing device 630 may also include one or more processors 634 or processing circuits coupled to bus 632 for processing information.

Computing device 630 also includes a main memory 636, such as a Random Access Memory (RAM) or other dynamic storage device, coupled to bus 632 for storing information and instructions to be executed by processor 634. Main memory 636 also may be used for storing location information, temporary variables, or other intermediate information during execution of instructions by processor 634. Computing device 630 may also include a ROM 638 or other static storage device coupled to bus 632 for storing static information and instructions for processor 634. A storage device 640, such as a solid state device, magnetic disk or optical disk, is coupled to bus 632 for persistently storing information and instructions. For example, instructions for determining an initial flow rate and comparing the initial flow rate to a predetermined threshold and increasing or decreasing the cross-sectional area of the exhaust conduit corresponding thereto may be stored on the storage device 640.

The computing device 630 may be coupled via the bus 632 to a display 644, such as a liquid crystal display or active matrix display, for displaying information to a user. An input device 642, such as a keyboard or alphanumeric keypad, may be coupled to bus 632 for communicating information and command selections to processor 634. In another implementation, the input device 642 has a touch screen display 644.

According to various implementations, the processes and methods described herein may be implemented by the computing device 630 in response to the processor 634 executing an arrangement of instructions contained in main memory 636 (e.g., the operations of method 700). Such instructions may be read into main memory 636 from another non-transitory computer-readable medium, such as storage device 640. Execution of the arrangement of instructions contained in main memory 636 causes the computing device 630 to perform the illustrative processes described herein. One or more processors in a multi-processing arrangement may also be employed to execute the instructions contained in memory 636. In alternative implementations, hard-wired circuitry may be used in place of or in combination with software instructions to implement the illustrative implementations. Thus, implementations are not limited to any specific combination of hardware and software.

Although an example computing device is described in FIG. 7, the implementations described in this specification can be implemented in other types of digital electronic devices, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their equivalents, or in combinations of one or more of them.

The implementations described in this specification can be implemented in digital electronic equipment, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their equivalents, or in combinations of one or more of them. The implementations described in this specification can be implemented as one or more computer programs, i.e., one or more circuits of computer program instructions, encoded on one or more computer storage media for execution by, or to control the operation of, data processing apparatus. Alternatively or in addition, the program instructions may be encoded on an artificially generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. The computer storage medium can be or be included in a computer-readable storage device, a computer-readable storage substrate, a random or sequential access memory array or device, or a combination of one or more of them. Moreover, although a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium may also be or be included in one or more separate components or media (e.g., multiple CDs, disks, or other storage devices). Accordingly, computer storage media are tangible and non-transitory.

The operations described in this specification may be performed by data processing apparatus on data stored on one or more computer-readable storage devices or received from other sources. The term "data processing apparatus" or "computing device" includes all types of apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, a system on a chip, or a plurality or combination of the foregoing. An apparatus may comprise special purpose logic, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more of them. The apparatus and execution environment may implement a variety of different computing model infrastructures, such as web services, distributed computing and grid computing infrastructures.

A computer program (also known as a program, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be used in any form, including as a stand-alone program or as a circuit, component, subroutine, object, or other unit suitable for use in a computing environment. A computer program may, but need not, correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more circuits, sub-programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for performing actions in accordance with the instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. However, a computer need not have such a device. Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; a magneto-optical disk; and CD-ROM and DVD-ROM disks. The processor and the memory may be implemented by or incorporated in special purpose logic.

It should be noted that the term "example" as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such term is not intended to imply that such embodiments must be extraordinary or best examples).

The term "coupled" and the like as used herein means that two members are directly or indirectly connected to each other. Such a connection may be stationary (e.g., permanent) or movable (e.g., removable or releasable). Such a connection may be made using two members or two members and any additional intermediate members that are integrally formed as a single unitary body with one another or using two members or two members and any additional intermediate members that are attached to one another.

It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited herein. Furthermore, it is to be understood that features from one embodiment disclosed herein may be combined with features of other embodiments disclosed herein, as will be understood by one of ordinary skill in the art. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present inventions.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular inventions. Certain features that are described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Claims

1. A method for determining an outlet NOx amount in exhaust gas flowing through an aftertreatment system including a selective catalytic reduction, SCR, system and not including an outlet NOx sensor downstream of the SCR system, the method comprising:

flowing exhaust gas through the aftertreatment system;

introducing a reductant into the exhaust gas using a reductant introduction assembly;

determining a reductant mass of the reductant based on information received from a reductant mass sensor, wherein the reductant mass sensor is configured to measure reductant mass at a location downstream of the reductant introduction assembly and upstream of the SCR system;

determining an outlet NOx amount in the exhaust gas downstream of the SCR system based on the reductant mass;

determining whether the outlet NOx amount exceeds a predetermined threshold; and

in response to the outlet NOx amount exceeding the predetermined threshold, providing an indication to a user that the outlet NOx amount exceeds the predetermined threshold.

2. The method of claim 1, further comprising:

determining an inlet NOx amount of NOx gases in the exhaust gas upstream of the SCR system based on information received from an inlet NOx sensor,

wherein the outlet NOx amount is determined based on the reductant mass and the inlet NOx amount.

3. The method of claim 1, further comprising:

in response to the outlet NOx amount exceeding the predetermined threshold, determining that the reductant is diluted above a predetermined dilution threshold; and

providing an indication to a user that the reductant should be changed.

4. The method of claim 1, further comprising:

determining a differential pressure across the SCR system using a differential pressure sensor positioned across the SCR system;

wherein the outlet NOx amount is determined based on the reductant mass and the differential pressure.

5. The method of claim 1, further comprising:

determining a first temperature of exhaust gas entering the SCR system based on information received from a first temperature sensor located upstream of the SCR system; and

wherein the outlet NOx amount is determined using the reductant mass and the first temperature of the exhaust gas.

6. The method of claim 5, further comprising:

determining a second temperature of the exhaust gas downstream of the SCR system based on information received from a second temperature sensor located downstream of the SCR system,

wherein the outlet NOx amount is determined using the reductant mass, the first temperature of the exhaust gas, and the second temperature of the exhaust gas.