US20160108786A1

US20160108786A1 - System and method to calculate concentration of diesel exhaust fluid (def)

Info

Publication number: US20160108786A1
Application number: US14/979,810
Authority: US
Inventors: Krishnamurthy Narayanan
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2015-12-28
Filing date: 2015-12-28
Publication date: 2016-04-21

Abstract

A system to calculate concentration of diesel exhaust fluid (DEF) in an exhaust of an engine is disclosed. The system includes a selective catalytic reduction (SCR) module, a diesel exhaust fluid (DEF) module, a first NOx sensor, a second NOx sensor, and a control module. The SCR module is adapted to receive exhaust gas. The diesel exhaust fluid (DEF) module introduces the diesel exhaust fluid (DEF) into the exhaust and is upstream of the SCR module. The first NOx sensor is in fluid communication with exhaust to detect a first NOx value of the exhaust gas at a location upstream of the SCR module. The second NOx sensor is in fluid communication with exhaust to detect a second NOx value of the exhaust gas at a location downstream of the SCR module. The control module is in communication with the first NOx sensor, the SCR module, and the second NOx sensor to calculate a numeric value of the concentration of the diesel exhaust fluid (DEF) based on a conversion ratio. The conversion ratio is calculated according to a NOx differential between the first NOx sensor and the second NOx sensor relative to a predicted NOx differential for a given amount of DEF injected.

Description

TECHNICAL FIELD

The present disclosure relates to exhaust gas treatment systems, and more specifically, to a system to calculate a numeric value of concentration of diesel exhaust fluid (DEF) in an exhaust of an engine.

BACKGROUND

Currently, there are stringent emission norms to reduce nitrogen oxides (NOx) and other particulates from an exhaust of combustion engines. One of a technique for reducing NOx is based on selective catalytic reduction (SCR). A diesel exhaust fluid (DEF) is supplied into an SCR system to lower the concentration of the NOx. The concentration of the DEF plays a critical role in lowering NOx emissions. If DEF is either not present, or DEF of a lower quality is present, then the SCR system would be unable to efficiently reduce the NOx into other elements, such as nitrogen, and water.
Conventional sensorless systems are able to measure concentration of diesel exhaust fluid (DEF) only as a high quality and/or a low quality. In other words, the conventional sensorless systems are unable to measure analog values for DEF concentration. An aftertreatment system may also automatically trigger due to poor quality of the DEF and leads to unexpected shut-down. As a result, an operator is unable to take corrective measures prior to the unexpected shut-down. Therefore, the conventional sensorless systems suffer from operational efficiency and reliability issues.
U.S. Pat. No. 8,863,499, hereinafter referred to as '499 reference, discloses a system for indicating quality of a diesel exhaust fluid (DEF). The '499 reference discloses an exhaust gas treatment system for an internal combustion engine. The exhaust gas treatment system includes an exhaust gas conduit, a diesel exhaust fluid (DEF) source, a selective catalytic reduction (SCR) device, a NOx sensor, and a control module. The DEF source supplies a DEF having a quality factor. The NOx sensor is in fluid communication with the exhaust gas conduit. The NOx sensor is located downstream of the SCR device for detecting a NOx concentration value. The control module is in communication with the DEF source and the NOx sensor. The control module stores a diagnostic adaptation factor and an expected NOx value. The control module includes a dosing module for determining a control adaptation factor that is based on a deviation between the NOx concentration value and the expected NOx value. The diagnostic adaptation factor is selectively updated with the controls adaptation factor. However, the '499 reference is unable to calculate analog values of concentration quality of the diesel exhaust fluid (DEF). Therefore, there is a need for a system to calculate a numeric value of the concentration for the diesel exhaust fluid (DEF).

SUMMARY OF THE INVENTION

In one aspect of the present disclosure, a system to calculate concentration of diesel exhaust fluid (DEF) in an exhaust of an engine is provided. The system includes a selective catalytic reduction (SCR) module, a diesel exhaust fluid (DEF) module, a first NOx sensor, a second NOx sensor, and a control module. The SCR module is adapted to receive exhaust gas. The diesel exhaust fluid (DEF) module introduces the diesel exhaust fluid (DEF) into the exhaust and is upstream of the SCR module. The first NOx sensor is in fluid communication with exhaust to detect a first NOx value of the exhaust gas at a location upstream of the SCR module. The second NOx sensor is in fluid communication with exhaust to detect a second NOx value of the exhaust gas at a location downstream of the SCR module. The control module is in communication with the first NOx sensor, the SCR module, and the second NOx sensor to calculate a numeric value of the concentration of the diesel exhaust fluid (DEF) based on a conversion ratio. The conversion ratio is calculated according to a NOx differential between the first NOx sensor and the second NOx sensor relative to a predicted NOx differential for a given amount of DEF injected.
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 illustrates an exemplary machine utilizing the proposed system, in accordance with the concepts of the present disclosure;

FIG. 2 illustrates a block diagram of a system for calculating a numeric value of the concentration of diesel exhaust fluid (DEF), in accordance with the concepts of the present disclosure; and

FIG. 3 illustrates a flow diagram of a method for calculating the numeric value of the concentration of the diesel exhaust fluid (DEF), in accordance with the concepts of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary machine 10 utilizing proposed system to calculate concentration of diesel exhaust fluid (DEF) in an aftertreatment system of the machine 10, in accordance with the concepts of the present disclosure. The machine 10 may refer to any kind of stationary or moveable machine that performs a variety of operations associated with a particular industry. Examples of the machine 10 include, but are not limited to, commercial vehicles, off-highway vehicles, cars, trucks, vans, boats, ships, power generators, stationary gas compressors, etc.
The machine 10 includes an engine 12, a diesel oxidation catalyst (DOC) 14, a diesel particulate filter (DPF) 16, a selective catalytic reduction (SCR) module 18, a diesel exhaust fluid (DEF) module 20 and an exhaust stack 22. The machine 10 may also include other components (not shown) to satisfy the emission requirements without departing from the meaning and scope of the disclosure.
FIG. 2 illustrates a block diagram of a system 24 for calculating a numeric value of concentration of diesel exhaust fluid (DEF), in accordance with the concepts of the present disclosure. The system 24 may be implemented in an exhaust after-treatment system in various machines under various regulation norms. Examples of the regulation norms include, but are not limited to, Tier IV final, EU97/68 Stage 3b, etc. The system 24 also includes a first NOx sensor 26, a second NOx sensor 30, and a control module 28
During operation, the engine 12 generates an exhaust gas that is transmitted to the SCR module 18 at a position P1. In an embodiment, the exhaust gas from the engine 12 is routed through the diesel oxidation catalyst (DOC) 14, and the diesel particulate filter (DPF) 16 before reaching the SCR module 18. The diesel oxidation catalyst (DOC) 14 is adapted to oxidize carbon monoxide, gas phase hydrocarbons, and the soluble organic fraction (SOF) fraction of diesel particulate matter of the exhaust gas from the engine 12 into Carbon Dioxid_e(CO₂) and Wat_er (H₂O). The diesel particulate filter (DPF) 16 is adapted to receive the exhaust gas from the DOC 14 to filter particulates or unwanted substances from the exhaust gas prior to the SCR module 18. In an embodiment, removing the particulates from the exhaust gas prior to use of NOx sensors, i.e. the first NOx sensor 26, the second NOX sensor 30 may increase the efficiency and life of the NOx sensors.
The DEF module 20 is adapted to introduce the diesel exhaust fluid (DEF) or reductant materials or mixture thereof into the exhaust gas for reducing NOx emissions. Examples of the diesel exhaust fluid (DEF) or the reductant materials include, but are not limited to, anhydrous ammonia, aqueous ammonia, urea, AdBlue (commercial name) etc. In an embodiment, the reductant materials or the DEF may have a chemical composition of about 67.5% de-ionized water and 32.5% urea and the DEF may have a melting point of about 12 F.
In an embodiment, the diesel exhaust fluid (DEF) module 20 is located upstream of the SCR module 18 to supply the DEF into a mixer placed upstream of the SCR module 18. The diesel exhaust fluid (DEF) module 20 may be situated at any other location within or outside of the system 24 to reduce the exhaust NOx. The DEF module 20 may also include other components (not shown), such as an urea reservoir, a pump, sensors, switches, injection modules for injecting the DEF or the reductant materials or combination thereof into the SCR module 18 without departing from the meaning and scope of the disclosure.
The selective catalytic reduction (SCR) module 18 is adapted to receive the exhaust gas from the DPF 16 and DEF from the DEF module 20. The SCR module 18 and the DEF module 20 are in communication with each other. The exhaust from the DPF 16 is uniformly mixed with a spray of DEF in a mixture (not shown). In the presence of a catalyst and at desired temperature, the SCR module 18 reduces the NOx to Nitrogen (N₂) and other harmless components. The output gas from the SCR module 18 is escaped into environment via the exhaust stack 22.
The system 24 further includes the first NOx sensor 26 and the second NOx sensor 30 in communication with the control module 28. The first NOx sensor 26 is in fluid communication with exhaust to detect a first NOx value (also called NOx emission value) of the exhaust gas. The first NOx value of the exhaust gas is detected at a location L1 that is upstream of the SCR module 18. Similarly, the second NOx sensor 30 is in fluid communication with exhaust to detect a second NOx value (also called NOx emission value) of the exhaust gas. The second NOx value of the exhaust gas is detected at a location L2 that is downstream of the SCR module 18. The second NOx sensor 30 may be a virtual NOx sensor generated by the control module 28 based on variables, such as those provided by the other sensors. The system 24 may use other types of devices, components and/or techniques for measuring the NOx values at the upstream, i.e. the location L1 and the downstream, i.e. the location L2 of the SCR module 18.
In an embodiment, the control module 28 is in communication with the first NOx sensor 26, the second NOx sensor 30, the SCR module 18, and the DEF module 20 to calculate a numeric value of the concentration (i.e. quality) of the diesel exhaust fluid (DEF) (or reductant materials) based on a conversion ratio. In an embodiment, the control module 28 determines virtual concentration of DEF as the numeric value. For example, the operator may receive the numeric value of DEF quality on a display and if the calculated quality is not within a specified range then a corrective action may be taken by the operator for efficient NOx conversion. In an embodiment, the system 24 is based on sensorless technology for calculating the numeric value of the concentration (i.e. quality) of the diesel exhaust fluid (DEF).
The control module 28 calculates the conversion ratio according to a NOx differential between the first NOx sensor 26 and the second NOx sensor 30 relative to a predicted NOx differential for a given amount of DEF injected. In an embodiment of the present disclosure, the control module 28 determines the convention ratio that is a deviation of actual NOx values from the anticipated NOx values (also called expected NOx values). For example, if the actual NOx value is smaller than the expected NOx values, then the system 24 has good concentration of the DEF or vice-versa.
The operator may take corrective action to enhance the DEF concentration/quality and make the system 24 efficient in reducing the NOx emissions. The control module 28 may be further configured to generate a signal when the quality of the DEF is not within an acceptance level (e.g., a predefined tolerance level). For example, the control module 28 may be configured to trigger a warning light or an alarm to the operator on the display in a control room or on a network or on a service diagnostic tool. For instance, if the NOx reduction is less than expected, the control module 28 may generate the signal to enhance the quality of DEF to be supplied to the SCR module 18.
The control module 28 may include a processor (e.g., a microprocessor, microcontroller, ASIC, DSP, etc.), a memory (e.g., flash, ROM, RAM, EEPROM, etc.), and an interface. The processor may be a processing device, such as a microcontroller, that may exchange data with the memory and the interface to perform certain processes consistent with features described herein. The control module 28 may include a plurality of processors that may operate collectively to perform various functions consistent with certain embodiments presented herein. In an embodiment, the control module 28 is configured to receive information from various physical sensors (e.g., exhaust and/or reductant flow rate sensors, NOx sensors, engine sensors, ambient condition sensors, etc.), or may generate or utilize preconfigured virtual sensors (e.g., a virtual NOx sensor, a virtual urea sensor, etc.) at various points within the system 24. The control module 28 may be a module programmed or hardwired within an engine control module (ECM) that performs functions dedicated to embodiments described herein. For example, the control module 28 may be implemented in software that is stored as instructions and data within a memory device of the ECM and is executed by a processor operating within the ECM. Alternatively, the control module 28 may be a module that is separate from other components of the system 24, and may be in electronic communication with other components of the system 24.
FIG. 3 illustrates a flow diagram of a method 32 for calculating the numeric value of the concentration of the diesel exhaust fluid (DEF), in accordance with the concepts of the present disclosure. The method 32 is described in conjunction with FIG. 1, and FIG. 2.
At step 34, a first NOx value of exhaust gas at a location upstream of the SCR module 18 is detected. In an embodiment, the first NOx sensor 26 is in fluid communication with exhaust to detect the first NOx value of the exhaust gas. The first NOx value of the exhaust gas is detected at a location L1 that is upstream of the SCR module 18.
At step 36, a second NOx value of the exhaust gas at a location downstream of the SCR module is detected. In an embodiment, the second NOx sensor 30 is in fluid communication with the exhaust to detect the second NOx value of the exhaust gas. The second NOx value of the exhaust gas is detected at a location L2 that is downstream of the SCR module 18.
At step 38, a conversion ratio is calculated. In an embodiment, the control module 28 calculates the conversion ratio according to the NOx differential between the first NOx sensor 26 and the second NOx sensor 30 relative to a predicted NOx differential for a given amount of DEF injected.
At step 40, a numeric value of the concentration of the diesel exhaust fluid (DEF) is calculated based on the conversion ratio. In an embodiment, the control module 28 is configured to calculate the numeric value of the concentration of the diesel exhaust fluid (DEF) on the basis of the conversion ratio. In an embodiment, the numeric values are analog values depicting quality of DEF in terms of percentages and/or graphs. The numeric value is an analog value showing DEF quality between 0%-100%. For example, if the concentration of DEF is below 50%, then the operator may take corrective action to improve the quality of DEF.
At step 42, the numeric value of the concentration of the diesel exhaust fluid (DEF) is shown to an operator. The control module 28 calculates the numeric value of the concentration of the DEF and shows the numeric value to the operator on the display. If the calculated quality is below a threshold then a corrective action may be taken by the operator for efficient NOx conversion.
The above description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Further, any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to DEF or Urea based fluids or any mixtures thereof and it is understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

INDUSTRIAL APPLICABILITY

The present disclosure provides the system 24 to calculate the numeric value of the concentration for the diesel exhaust fluid (DEF). The system 24 includes the engine 12, the DOC 14, the DPF 16, the SCR module 18, the diesel exhaust fluid (DEF) module 20, the first NOx sensor 26, the second NOx sensor 30, and the control module 28. The SCR module 18 is adapted to receive exhaust gas. The diesel exhaust fluid (DEF) module 20 introduces the diesel exhaust fluid (DEF) into the exhaust and is upstream of the SCR module 18. The first NOx sensor 26 is in fluid communication with exhaust to detect a first NOx value of the exhaust gas and is at the location L2 upstream of the SCR module. The second NOx sensor 30 is in fluid communication with exhaust to detect a second NOx value of the exhaust gas at a location downstream of the SCR module 18. The control module 28 is in communication with the first NOx sensor 26, the SCR module 18, and the second NOx sensor 30 to calculate the numeric value of the concentration of the diesel exhaust fluid (DEF) based on the conversion ratio. The control module 28 calculates the conversion ratio according to the NOx differential between the first NOx sensor 26 and the second NOx sensor 30 relative to a predicted NOx differential for a given amount of DEF injected.
The disclosed system 24 may be implemented in an exhaust after-treatment system in various machines. The system 24 provides enhanced reliability of NOx reduction by calculating numeric values (i.e. analog values) of DEF quality. The numeric values of the DEF concentration is shown to the operator so that a corrective action is taken for proper operation of the system 24. The proposed disclosure provides a low cost solution, enhances productivity, improves life of the aftertreatment system, etc.
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 and methods 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 system to calculate concentration of diesel exhaust fluid (DEF) in an exhaust of an engine, the system comprising:

a selective catalytic reduction (SCR) module adapted to receive exhaust gas;

a diesel exhaust fluid (DEF) module for introducing the diesel exhaust fluid (DEF) into the exhaust, upstream of the SCR module;

a first NOx sensor in fluid communication with exhaust to detect a first NOx value of the exhaust gas at a location upstream of the SCR module;

a second NOx sensor in fluid communication with exhaust to detect a second NOx value of the exhaust gas at a location downstream of the SCR module; and

a control module in communication with the first NOx sensor, the SCR module, and the second NOx sensor, the control module calculates a numeric value of the concentration of the diesel exhaust fluid (DEF) based on a conversion ratio;

wherein the conversion ratio is calculated according to a NOx differential between the first NOx sensor and the second NOx sensor relative to a predicted NOx differential for a given amount of DEF injected.