A diesel exhaust fluid dosing system for a vehicle exhaust after-treatment system and method thereof

Abstract

A diesel exhaust fluid dosing system for a vehicle exhaust after-treatment system and method thereof [0044] The invention relates to a diesel exhaust fluid dosing system for optimizing vehicle exhaust after-treatment. The system (100) comprises a pressure sensor (101) positioned downstream of a Diesel Particulate Filter (DPF) (102) to detect exhaust gas pressure variations, and a dosing unit (103) to inject DEF into the exhaust stream (109) upstream of a Selective Catalytic Reduction (SCR) catalyst (104). A control unit (105) receives real-time pressure data, calculates exhaust gas turbulence, and generates control signals to adjust the DEF dosing rate accordingly. Additionally, a urea tank (106) and a pump (107) supply DEF, while a mixer (108) enhances uniform distribution in the exhaust flow. The method (200) improves NOx emission reduction efficiency, prevents localized crystallization on the SCR catalyst, and optimizes overall exhaust after-treatment performance, ensuring compliance with environmental regulations.

Specification

Description:Preamble to the Description

[0001] The following specification particularly describes the invention and the manner in which it is to be performed:
DESCRIPTION OF THE INVENTION
Technical field of the invention
[0002] The present invention pertains to exhaust after-treatment systems for diesel engines, particularly a diesel exhaust fluid dosing system designed to reduce nitrogen oxide (NOx) emissions. The dosing system employs Selective Catalytic Reduction (SCR) technology, where a urea solution is injected into the exhaust stream to facilitate the conversion of NOx into nitrogen and water vapour. The dosing system of the present invention results in optimized exhaust fluid injection rates based on real-time exhaust pressure and turbulence data, enhancing mixing of Diesel Exhaust Fluid (DEF) with exhaust gases thereby enhancing NOx reduction efficiency and preventing crystallization within the SCR catalyst.
Background of the invention
[0003] In diesel engines, exhaust after-treatment systems are commonly used to reduce harmful emissions, particularly nitrogen oxides (NOx), which contribute significantly to environmental pollution. One widely adopted technology is Selective Catalytic Reduction (SCR), where an aqueous urea solution, known as Diesel Exhaust Fluid (DEF), is injected into the exhaust stream. The DEF undergoes a chemical reaction with NOx in the presence of a catalyst, converting it into harmless nitrogen and water vapor. However, existing SCR systems face multiple limitations that impact their overall effectiveness and reliability.
[0004] Many current systems inject the DEF based on NOx concentration and ammonia level on the catalyst, which does not account for variations in exhaust gas flow and turbulence. In conditions where exhaust turbulence fluctuates, the fixed-rate dosing often leads to incomplete mixing of the fluid with exhaust gases, reducing NOx conversion efficiency and increasing the risk of unreacted DEF passing through the system.
[0005] Further, inadequate mixing and dosing control can lead to localized crystallization of the DEF on the SCR catalyst. This crystallization not only reduces the catalyst's surface area available for reaction but also clogs the system, increasing maintenance requirements and operational downtime.
[0006] Conventional systems typically lack adaptive controls to modify dosing based on real-time exhaust conditions. The absence of such feedback mechanisms results in suboptimal NOx reduction, especially during transient engine operations when exhaust flow and temperature vary significantly. Further, during high engine loads, excessive DEF injection leads to ammonia slip, where unreacted ammonia is released into the environment. This undermines the emission reduction goals and leads to regulatory compliance issues. Furthermore, current systems often fail to adjust dosing appropriately during periods of high exhaust turbulence. Without adaptive control, DEF dosing remains suboptimal, impacting SCR catalyst efficiency and leading to increased NOx emissions.
[0007] Several attempts have been made to address these issues in SCR systems. For instance the Patent Application No. DE102009049521A1 titled "An apparatus for controlling the quantity of aqueous urea solution injection and injection control system for an aqueous urea solution" discloses a relationship between nitrogen monoxide (NO) and nitrogen dioxide (NO) flowing into the NOx reduction catalyst is estimated based on a nitrogen dioxide conversion ratio, according to which nitrogen monoxide (NO) is oxidized to nitrogen dioxide (NO) in the oxidation catalyst, and a nitrogen monoxide conversion ratio oxidation of the carbon by the nitrogen dioxide (NO) in the filter, the nitrogen dioxide (NO) is converted to nitric oxide (NO). The amount of aqueous urea solution injected through the injector is controlled based on the ratio between the nitrogen monoxide (NO) and nitrogen dioxide (NO).
[0008] The Patent Application No. IN201941021660A titled "A system for on-board variable AdBlue concentration solution in an after treatment system" discloses a system for on-board variable AdBlue concentration solution in an aftertreatment system of an internal combustion engine comprising an AdBlue tank for storing the AdBlue solution and an AdBlue dosing control for regulating the quantity of AdBlue solution released from the AdBlue tank. The system also comprises an engine exhaust for carrying the internal combustion engine emissions, wherein the emissions are mixed with the ad blue solution released by the ad blue dosing control. Further, the system comprises a Selective Catalytic Reduction (SCR) filter for reducing the content of nitrogen oxide (NOx) in internal combustion engine emissions and a catalytic converter for converting the harmful emissions downstream of SCR filter (104) into harmless water and nitrogen.
[0009] The Patent Application No. EP4330523A1 titled "Exhaust gas aftertreatment system and method" discloses an exhaust gas aftertreatment (EAT) system for receiving exhaust gases from an internal combustion engine has a diesel oxidation catalyst (DOC) upstream and in close proximity to a diesel particulate filter (DPF). A pressure differential sensor is configured to measure a pressure differential across the DOC and the DPF between a first measurement position upstream of the DOC and a second measurement position downstream of the DPF. A method of operating the EAT system is also disclosed which includes using a mathematical model to determine a pressure drop occurring in the system between the first and second measurement positions outside of the DPF. The modelled pressure drop is used together with a measured pressure drop to derive a value for the pressure drop across the DPF itself for use in a model to determine the soot loading of the DPF.
[0010] The Patent Application No. CN216714515U titled "Device for reducing emission of particulate matters and nitrogen oxides of engineering machinery" discloses a device for reducing the emission of engineering machinery particles and nitric oxides, wherein a shell of the device is of a cylindrical structure, and an exhaust inlet joint and a tail gas outlet joint are respectively arranged at two ends of the shell; an oxidation type catalytic converter, a partial flow type particulate matter trap, a selective catalytic reduction device and an ammonia escape catalytic converter are sequentially arranged in the cylindrical shell from the inlet end to the outlet end; an auxiliary heating device and a urea nozzle are arranged on the inner wall of the shell between the partial flow type particulate matter catcher and the selective catalytic reduction device.
[0011] As a result, there is a need for a system that dynamically adjust the DEF dosing rate in real time, effectively responding to variations in exhaust gas turbulence, optimizing the uniformity of DEF mixing in the exhaust stream, preventing issues including localized crystallization on the SCR catalyst, and enhancing the overall efficiency of NOx reduction, thereby overcoming limitations in existing dosing systems by leveraging real-time exhaust pressure data, allowing for precise modulation of the DEF injection rate to accommodate changing exhaust conditions
Summary of the invention
[0012] The present invention addresses the limitations of the prior art by introducing a DEF dosing system for vehicle exhaust after-treatment systems. The dosing system comprises a pressure sensor positioned downstream of the Diesel Particulate Filter (DPF). The pressure sensor continuously monitors exhaust gas pressure variations, providing essential data to calculate turbulence levels within the exhaust stream. The system further comprises a dosing unit positioned upstream of a Selective Catalytic Reduction (SCR) catalyst, to inject DEF directly into the exhaust stream.
[0013] Further, the system comprises a control unit operatively connected to the pressure sensor and the dosing unit. The control unit receives real-time pressure data from the sensor, calculating exhaust gas turbulence and generating multiple control signals to adapt the DEF injection rate accordingly. Furthermore, by modulating the injection rate to align with the exhaust gas turbulence, the system enhances the uniformity of DEF distribution within the exhaust stream, thereby optimizing the SCR catalyst's efficiency and reducing ammonia slip. This adaptive dosing improves the overall performance of NOx reduction and also mitigates issues of localized DEF crystallization on the SCR catalyst.
[0014] Additionally, the system comprises a mixer positioned upstream of the SCR catalyst, that intensifies the turbulence and aids in achieving a homogeneous blend of DEF and exhaust gases. The dosing rate is adjusted through a Pulse-Width Modulation (PWM) mechanism, that delivers the DEF in pulsed increments, further promoting uniform mixing and reducing the risk of crystallization on the catalyst.
[0015] The present invention addresses the critical need for a Diesel Exhaust Fluid (DEF) dosing system within vehicle exhaust after-treatment systems to effectively reduce nitrogen oxide (NOx) emissions generated by diesel engines. The DEF dosing system, as disclosed, is an essential component of the Selective Catalytic Reduction (SCR) technology, facilitating the conversion of harmful NOx gases into benign nitrogen and water vapor. The system ensures compliance with regulatory standards and also enhances engine efficiency and longevity by optimizing the exhaust treatment process. Consequently, the invention significantly contributes to achieving sustainable diesel engine performance.
Brief Description of drawings
[0016] Figure 1 illustrates a diesel exhaust fluid dosing system for a vehicle exhaust after-treatment system, in accordance with one embodiment of the invention.
[0017] Figure 2 illustrates a flowchart of a method for optimizing diesel exhaust fluid dosing in a vehicle exhaust after-treatment system, in accordance with one embodiment of the present invention.
Detailed description of the invention
[0018] In order to more clearly and concisely describe and point out the subject matter of the claimed invention, the following definitions are provided for specific terms, which are used in the following written description.
[0019] The term "Diesel Exhaust Fluid (DEF)" refers to a solution comprising 32.5% to 37% ± 1.5% urea and 67.5% deionized water, specifically designed for use in diesel engines equipped with Selective Catalytic Reduction (SCR) systems. DEF is injected into the exhaust stream, where it chemically reacts with nitrogen oxide (NOx) emissions, converting them into harmless nitrogen and water vapor.
[0020] The term "Pressure Sensor" refers to a device positioned downstream of a Diesel Particulate Filter (DPF), used to detect exhaust gas pressure variations. The sensor provides real-time data essential for calculating the turbulence levels in the exhaust stream, enabling adaptive control of the DEF injection rate.
[0021] The term "Selective Catalytic Reduction (SCR) catalyst" refers to a catalytic component in the exhaust after-treatment system that facilitates the conversion of NOx into harmless nitrogen (N2) and water (H2O) by reacting with the injected DEF solution under controlled conditions.
[0022] The term "Pulse-Width Modulation (PWM)" refers to a control technique used to modulate the DEF dosing rate by varying the pulse duration of DEF injections, preventing crystallization on the SCR catalyst and enhancing uniform distribution within the exhaust flow.
[0023] The term "Exhaust gas turbulence" refers to the fluctuations in the exhaust gas flow caused by pressure variations downstream of the DPF. These fluctuations affect the distribution of DEF in the exhaust stream and, when measured accurately, allow for adaptive control of DEF dosing.
[0024] The term "Ammonia Slip" refers to the unreacted ammonia that may escape the SCR catalyst due to incomplete reactions between DEF and NOx. The present invention minimizes ammonia slip by controlling the DEF injection in response to real-time turbulence and exhaust conditions.
[0025] The present invention discloses a Diesel Exhaust Fluid (DEF) dosing system for the vehicle exhaust after-treatment that enhances the efficiency of NOx reduction in Selective Catalytic Reduction (SCR) systems. The system comprises a pressure sensor positioned downstream of a Diesel Particulate Filter (DPF) to monitor exhaust gas pressure variations. Further, the system comprises a dosing unit to inject the DEF into the exhaust stream upstream of the SCR catalyst, and a control unit operatively connected to both the pressure sensor and the dosing unit. The control unit calculates exhaust gas turbulence based on real-time pressure data and adjusts the DEF dosing rate accordingly. This dynamic modulation improves the DEF mixing and reduces the risk of ammonia slip and DEF crystallization, thereby optimizing SCR catalyst efficiency. Additionally, the system incorporates a mixer upstream of the SCR catalyst to further enhance the DEF and exhaust gas distribution.
[0026] Further, the present invention discloses a method for optimizing DEF dosing in a vehicle's exhaust after-treatment system. The method comprises calculating exhaust gas turbulence downstream of the Diesel Particulate Filter (DPF) to adaptively control the DEF injection rate. Further, by analyzing real-time exhaust pressure data, modulates the DEF dosing frequency to achieve uniform distribution within the exhaust flow. This approach enhances the mixing of DEF with exhaust gases, effectively reducing ammonia slip, preventing SCR catalyst crystallization, and improving NOx reduction efficiency.
[0027] FIGURE 1 illustrates a diesel exhaust fluid dosing system for a vehicle exhaust after-treatment system, in accordance with an embodiment of the present invention. The system (100) effectively integrates various components to optimize the dosing of DEF into the exhaust stream. The system (100) comprises a pressure sensor (101) positioned downstream of a Diesel Particulate Filter (DPF) (102). The pressure sensor (101) continuously monitors exhaust gas pressure and detect variations therein. Further, the system (100) comprises a dosing unit (103) operatively connected to the pressure sensor (101) and is positioned upstream of a Selective Catalytic Reduction (SCR) catalyst (104). The dosing unit (103) injects the DEF into an exhaust stream (109) at precise intervals and quantities to facilitate effective NOx reduction as the exhaust gases pass through the SCR catalyst (104). In an embodiment of the invention, the DEF comprises 32.5% to 37% ± 1.5% urea, ensuring optimal performance.
[0028] Further, the system (100) comprises a control unit (105) to receive real-time exhaust pressure data from the pressure sensor (101) and calculate exhaust gas turbulence based on the pressure variations detected by the pressure sensor (101). Utilizing this turbulence data, the control unit (105) generates multiple control signals to adjust the DEF dosing rate dynamically, thereby optimizing the injection of DEF based on real-time exhaust conditions.
[0029] Further, the system (100) comprises a urea tank (106) and a pump (107), that work in conjunction to supply DEF to the dosing unit (103). The control unit (105) regulates the operation of the pump (107) to increase or decrease the DEF flow in response to the exhaust gas turbulence at the SCR catalyst (104). This regulation enhances the efficiency of the SCR catalyst (104) during operation.
[0030] Additionally, a mixer (108) is located upstream of the SCR catalyst (104). The mixer (108) enhances the uniform distribution of DEF within the exhaust stream (109), thereby increasing the turbulence of the exhaust gas flow. This enhanced mixing contributes to the overall effectiveness of the NOx reduction process.
[0031] In an embodiment of the present invention, the control unit (105) modulates the DEF dosing rate with a variable frequency corresponding to the detected exhaust gas turbulence in real time. This modulation enhances the uniform mixing of DEF in the exhaust flow, thereby optimizing the effectiveness of the Selective Catalytic Reduction (SCR) catalyst (104). Further, the control unit (105) modulates the dosing unit (103) using Pulse-Width Modulation (PWM) to achieve a pulsed injection rate. This pulsed injection strategy effectively prevents localized DEF crystallization on the SCR catalyst (104), that impairs the performance and longevity of the exhaust system.
[0032] Further, the control unit (105) continually adjusts the dosing rate based on thresholds for pressure variations detected by the pressure sensor (101). This adaptive control mechanism ensures that the system (100) remains responsive to changing conditions, optimizing performance and emissions reduction.
[0033] Furthermore, by maintaining an optimal dosing rate and promoting thorough mixing of DEF, the system (100) prevents localized DEF crystallization on the SCR catalyst (104), thereby ensuring its longevity and performance. This innovative approach of monitoring, calculating, and dynamically adjusting the DEF dosing rate enhances the performance of the vehicle's exhaust after-treatment system and also significantly contributes to the reduction of harmful emissions, representing a notable advancement in the field of vehicle emissions control.
[0034] FIGURE 2 illustrates a flowchart of a method for optimizing diesel exhaust fluid dosing in a vehicle exhaust after-treatment system, in accordance with an embodiment of the present invention. The method (200) comprises the steps of measuring the exhaust gas pressure at a designated point downstream of the Diesel Particulate Filter (DPF) using a pressure sensor in step (201). In step (202), the exhaust gas turbulence is calculated based on the measured pressure data. The exhaust gas turbulence is determined by the pressure at downstream of the Diesel Particulate Filter.
[0035] In step (203) the DEF dosing rate is modulated by adjusting the injection frequency according to the calculated exhaust gas turbulence. Further, in step (104), the DEF is injected into the exhaust stream upstream of the SCR catalyst in response to real-time pressure data.
[0036] In an embodiment of the present invention, the DEF dosing rate is increased during periods of high exhaust gas turbulence. This adjustment enhances mixing and reduces the risk of ammonia slip, which occurs when excess ammonia escapes unreacted from the exhaust system.
[0037] Having generally described this invention, a further understanding can be obtained by reference to a specific example, which is provided herein for the purpose of illustration only and is not intended to be limiting unless otherwise specified.
Example 1: Demonstrative Illustration of Usage of Proposed Invention
[0038] In a practical application of the present invention, a DEF dosing system (100) is integrated into a heavy-duty diesel vehicle equipped with a Diesel Particulate Filter (DPF) (102) and a Selective Catalytic Reduction (SCR) catalyst (104). The pressure sensor (101) is strategically positioned downstream of the DPF to continuously monitor exhaust gas pressure. As the vehicle operates, the pressure sensor (101) detects variations in exhaust gas pressure that indicate changes in engine load and exhaust flow dynamics.
[0039] Upon detecting a significant pressure variation, the control unit (105) receives real-time data from the pressure sensor (101) and calculates the corresponding exhaust gas turbulence. Based on this calculation, the control unit (105) generates control signals to modulate the dosing unit (103). For instance, if the pressure data indicates a high level of turbulence, the control unit (105) increases the dosing rate of DEF to enhance mixing with the exhaust stream (109), thus optimizing the reduction of nitrogen oxides (NOx) emissions.
[0040] The DEF is drawn from the urea tank (106) through the pump (107) and injected into the exhaust stream (109) upstream of the SCR catalyst (104). The dosing unit (103) employs Pulse-Width Modulation (PWM) to achieve precise pulsed injection of DEF, preventing localized crystallization on the SCR catalyst. As the exhaust gas, now enriched with DEF, passes through the mixer (108) located upstream of the SCR catalyst (104), the exhaust gas experiences increased turbulence, that facilitates uniform distribution and enhances the efficiency of the SCR process.
[0041] As the exhaust gases enter the SCR catalyst (104), the ammonia present from the DEF reacts with the nitrogen oxides (NOx) in the exhaust, converting them into harmless nitrogen and water vapor. This process significantly reduces harmful emissions, ensuring the vehicle complies with stringent environmental regulations. Throughout this operation, the system (100) continuously monitors the pressure data to make real-time adjustments to the DEF dosing rate. This dynamic control improves emission performance and also prevents ammonia slip, contributing to a cleaner exhaust output.
[0042] The present invention offers several key advantages that enhance its functionality and performance in reducing harmful emissions. The system (100) optimizes the dosing of DEF based on real-time exhaust gas pressure and turbulence measurements, ensuring efficient conversion of nitrogen oxides (NOx) into harmless nitrogen and water vapor. This targeted approach significantly reduces harmful emissions, contributing to compliance with stringent environmental regulations. By modulating the DEF dosing rate in response to exhaust gas turbulence, the system (100) ensures more uniform mixing of DEF and exhaust gases, enhancing the effectiveness of the Selective Catalytic Reduction (SCR) process and leading to better emission reduction performance.
[0043] Moreover, the control unit (105) allows to adjust the DEF dosing rate based on pressure thresholds, ensuring that dosing is optimized for varying driving conditions and improving overall system performance. Additionally, increasing the DEF dosing rate during periods of high exhaust gas turbulence helps minimize ammonia slip, which occurs when excess ammonia escapes unreacted, thus enhancing emission control and preventing potential regulatory penalties associated with ammonia emissions. The combination of real-time pressure monitoring, turbulence calculations, and adaptive dosing strategies results in increased efficiency of the exhaust after-treatment system, reducing operational costs for the vehicle. Moreover, the proactive management of DEF dosing and prevention of crystallization contribute to simplified maintenance procedures, extending maintenance intervals and ensuring reliable operation over time.

Reference numbers:
Components Reference Numbers
Dosing System 100
Pressure Sensor 101
Diesel Particulate Filter (DPF) 102
Dosing unit 103
Selective Catalytic Reduction (SCR) catalyst 104
Control unit 105
Urea tank 106
Pump 107
Mixer 108
Exhaust stream 109
, Claims:1. A Diesel Exhaust Fluid (DEF) dosing system for a vehicle exhaust after-treatment system, the system (100) comprising:
a. a pressure sensor (101) positioned downstream of a Diesel Particulate Filter (DPF) (102), to detect variation in exhaust gas pressure;
b. a dosing unit (103) to inject DEF into an exhaust stream (109) upstream of a Selective Catalytic Reduction (SCR) catalyst (104);
c. a control unit (105) operatively connected to the pressure sensor (101) and the dosing unit (103), configured to:
i. receive real-time exhaust pressure data from the pressure sensor (101);
ii. calculate exhaust gas turbulence based on the pressure variations detected by the pressure sensor (101); and
iii. generate one or more control signals to adjust the DEF dosing rate based on the calculated exhaust gas turbulence.

2. The system (100) as claimed in claim 1, wherein the control unit (105) further modulate the DEF dosing rate with a variable frequency corresponding to the detected exhaust gas turbulence in real time, enhancing uniform mixing of DEF in the exhaust flow.

3. The system (100) as claimed in claim 1, further comprises:
i. a urea tank (106) and a pump (107) to supply DEF to the dosing unit (103), wherein the control unit (105) regulates the pump (107) to increase or decrease the DEF flow based on the exhaust gas turbulence at the SCR catalyst, thereby optimizing SCR catalyst efficiency.
4. The system (100) as claimed in claim 1, wherein the control unit (105) modulates the dosing unit (103) using Pulse-Width Modulation (PWM) to achieve a pulsed injection rate, thereby preventing localized DEF crystallization on the SCR catalyst.

5. The system (100) as claimed in claim 1, further comprising a mixer (108) located upstream of the SCR catalyst, wherein the mixer (108) enhances the uniform distribution of DEF by increasing the exhaust gas turbulence.

6. A method for optimizing Diesel Exhaust Fluid (DEF) dosing in a vehicle exhaust after-treatment system, the method (200) comprises the steps of:
a. measuring exhaust gas pressure at a point downstream of a DPF using a pressure sensor;
b. calculating exhaust gas turbulence based on the measured pressure;
c. modulating the DEF dosing rate by adjusting the injection frequency based on the calculated exhaust gas turbulence; and
d. injecting DEF into the exhaust stream upstream of the SCR catalyst in response to real-time pressure data.

7. The method (200) as claimed in claim 6, wherein the DEF dosing rate is increased during periods of high exhaust gas turbulence to enhance mixing and reduce ammonia slip.

8. The method (200) as claimed in claim 6, wherein the exhaust gas turbulence is determined by the pressure downstream of the Diesel Particulate Filter.

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