Intelligent urea crystallization removal control method and system for SCR system based on waste heat recycling

Abstract

The present application relates to the technical field of engine exhaust aftertreatment, and particularly relates to a urea crystallization intelligent removal control method and system based on waste heat recovery for an SCR system. The control method comprises: determining a basic urea injection amount; monitoring the exhaust temperature at the inlet end of the waste heat recovery device in real time, controlling the on-off state of the waste heat recovery pipeline according to the temperature zoning, and correcting the basic urea injection amount; determining the urea crystallization state based on the SCR conversion efficiency and the SCR inlet and outlet differential pressure, triggering the crystallization removal program; setting a crystallization removal target temperature, dynamically adjusting the HC injection amount according to the temperature difference, and raising the SCR inlet end temperature to the target removal interval; monitoring the SCR conversion efficiency during the removal process, and terminating the removal program when the exit condition is met, thereby reducing the active regeneration fuel consumption through waste heat recovery, inhibiting crystallization generation through zoning adaptive control, improving the crystallization identification accuracy through double-parameter determination, and realizing the synergistic optimization of energy saving, crystallization inhibition and efficient removal.

Description

Technical Field

[0001] This invention relates to the field of engine exhaust aftertreatment technology, specifically to a method and system for intelligent removal and control of urea crystals in an SCR system based on waste heat recovery. Background Technology

[0002] With the full implementation of the China VI B emission standards and Real-Road Driving (RDE) regulations, the nitrogen oxides (NOx) emissions from heavy-duty diesel vehicles have increased. x With significantly stricter emission limits, the reliability of the Selective Catalytic Reduction (SCR) system, a core aftertreatment device for ensuring emission compliance, is crucial. However, in practical applications, urea crystallization has become one of the main failure modes in SCR system operation. This phenomenon mainly stems from uneven mixing of urea solution and exhaust gas, as well as insufficient pyrolysis and hydrolysis of urea under low-temperature conditions. Especially when the engine is running at low load, the exhaust temperature is low, significantly increasing the risk of urea crystallization; conversely, as the exhaust temperature gradually increases, the crystals that have already formed may partially or slowly decompose. If not removed in time, deposits caused by low temperature or insufficient pyrolysis will lead to pipe blockage and coverage of catalyst active sites, thereby exacerbating emission deterioration and increased fuel consumption. Therefore, there is an urgent need to develop a technical solution that can accurately identify the crystallization state and employ effective removal methods to restore SCR system performance and engine economy.

[0003] To address the aforementioned issues, several solutions have been proposed in the prior art. Typical examples include: Patent No. CN202111274875.7 discloses an automatic urea crystallization identification and cleaning device and its control method. Its core lies in directly identifying the crystallization state inside the SCR mixer through machine vision, and triggering solvent injection or adjusting the injection strategy accordingly to increase exhaust temperature, achieving high-temperature pyrolysis removal; Patent No. CN202210834079.2 proposes an SCR catalyst urea crystallization amount calculation and crystallization removal system and method, which estimates the crystallization amount by establishing a real-time model and classifying it, then utilizes the engine's post-injection strategy to increase temperature and achieve pyrolysis removal; Patent No. CN202210415122.1 discloses a urea crystallization removal method and device, which indirectly calculates the crystallization amount based on the difference between the urea injection mass and the actual consumption mass. When the crystallization amount exceeds the limit, it adjusts combustion parameters to increase exhaust temperature, forming a closed-loop control.

[0004] As seen from the aforementioned patents, existing urea crystal removal technologies generally rely on adjusting engine injection strategies (such as delayed intake, delayed ignition, and post-injection fuel) to increase exhaust temperature, thereby achieving crystallization pyrolysis. Post-injection fuel (i.e., additional injection of hydrocarbon fuel) is widely used due to its significant temperature-raising effect. However, this method has significant shortcomings in practical applications: improper fuel injection quantity control can easily lead to persistently high exhaust temperatures, and injection accuracy directly affects fuel utilization efficiency; excessive injection will cause unnecessary fuel consumption, impairing overall engine fuel economy. Furthermore, in existing aftertreatment systems, the exhaust gas at the diesel particulate filter (DPF) outlet typically has a high temperature level, but the remaining heat resources have not been effectively recovered and utilized.

[0005] Therefore, in order to overcome the problems of high fuel consumption and low energy utilization caused by the existing technology of actively heating the fuel after injection to remove urea crystals, it is urgent to develop an intelligent control method and system for removing urea crystals in SCR systems based on waste heat recovery, so as to achieve the dual goals of energy saving and efficient removal. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method and system for intelligent urea crystal removal control in an SCR system based on waste heat recovery. The purpose is to utilize the exhaust temperature of the DPF through a recovery device to reduce the risk of urea crystallization, while simultaneously reducing fuel consumption and improving fuel efficiency by adjusting the HC injection quantity during the urea crystal removal process.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: a smart urea crystallization removal and control method for SCR systems based on waste heat recovery, comprising the following steps:

[0008] S1. Determination of basic urea injection quantity: Obtain the current operating parameters of the engine and determine the basic urea injection quantity based on the preset SCR basic control strategy.

[0009] S2. Injection correction and path switching based on temperature zone: Real-time monitoring of the exhaust temperature at the inlet of the regenerating device, dividing different temperature working ranges according to the comparison result between the exhaust temperature and the first preset temperature threshold, controlling the on / off state of the waste heat regenerating pipe under different temperature working ranges, and adaptively correcting the basic urea injection amount to obtain the actual urea injection amount.

[0010] S3. Crystallization Removal Program Judgment and Activation: Based on the SCR conversion efficiency and the differential pressure between the SCR inlet and outlet, combined with preset conditions, determine whether urea crystals are present; when urea crystals are detected and the preset activation conditions are met, the crystallization removal program is triggered.

[0011] S4. Crystallization removal program execution: Set the crystallization removal target temperature, and dynamically adjust the HC injection volume according to the difference between the current temperature and the target temperature to raise the SCR inlet temperature to the target removal temperature range.

[0012] S5. Determination of Removal Effectiveness: Monitor SCR conversion efficiency during the removal process. ,when The crystallization removal procedure will terminate when the preset exit conditions are met.

[0013] Furthermore, the current engine operating parameters in step S1 include one or more of the following: nitrogen oxide generation, SCR target conversion efficiency, and urea nitrogen content; the basic urea injection quantity is calculated using the following formula:

[0014] ;

[0015] In the formula, m NOx This refers to the real-time estimated amount of nitrogen oxides generated by the engine; η is the nitrogen mass fraction of urea (using industry standard 32.5% automotive urea, its nitrogen mass fraction η=0.466 is an inherent property and requires no additional calibration); M... urea The molar mass of urea is 60 g / mol (an inherent chemical property); the M... N The molar mass of nitrogen atoms (14 g / mol, an inherent chemical property); the η SCR Target conversion efficiency for SCR (manually preset).

[0016] Furthermore, step S2, injection correction and path switching based on temperature zones, includes:

[0017] S201. When the DPF outlet temperature is less than the first preset temperature threshold, the control switching valve switches to the bypass pipe and does not connect to the regenerative pipe; the actual urea injection volume is adjusted according to the following formula: ;

[0018] In the formula, This represents the actual amount of urea injected. This is a low-temperature correction factor, and it has a positive linear relationship with the outlet temperature of the DPF.

[0019] S202. When the DPF outlet temperature is ≥ the first preset temperature threshold, the control switching valve switches to the regenerative pipeline, and the actual urea injection quantity is expressed by the following formula: ;

[0020] In the formula, It has a positive linear relationship with the temperature at the outlet of the regenerative pipe, and when the temperature at the outlet of the regenerative pipe is ≥ the second preset temperature threshold, Take the maximum value.

[0021] Furthermore, step S3, the determination and initiation of the crystallization removal procedure, specifically includes:

[0022] S301. Preset start-up basic conditions, the basic conditions include engine running time not less than a first preset duration, no SCR catalyst aging or deactivation fault codes, and DPF carbon load lower than a preset safety threshold.

[0023] S302. Real-time monitoring of SCR conversion efficiency R and the pressure difference ΔP between the SCR inlet and outlet ends, wherein the SCR conversion efficiency R is calculated using the following formula:

[0024] ;

[0025] In the formula, NO xup NO at the SCR intake end x Concentration, NO xdown NO at the SCR outlet x concentration;

[0026] S303. When R < first preset efficiency threshold and ΔP ≥ first preset pressure threshold, and this state continues for a second preset duration, it is determined to be urea crystallization.

[0027] S304. When the basic conditions are met and it is determined that urea crystals are formed, further determine whether the SCR inlet temperature is greater than the third preset temperature threshold. If so, trigger the crystal removal procedure.

[0028] Furthermore, it also includes a fault differentiation step: when R < first preset efficiency threshold and ΔP < first preset pressure threshold, it is determined to be catalyst aging or deactivation based on the historical health baseline of the SCR catalyst.

[0029] When ΔP ≥ the first preset pressure threshold and R ≥ the first preset efficiency threshold, it is determined that the DPF is blocked or the exhaust pipe is faulty, and the urea crystal removal procedure is not started.

[0030] Furthermore, step S4, the crystal removal procedure, specifically includes:

[0031] S401, Set the target temperature for crystal removal. The The preset value is 500-700℃; the temperature at the outlet of the regenerating pipe is monitored in real time, and the temperature difference ΔT between it and the target temperature is calculated.

[0032] S402, Determine the HC injection correction coefficient dynamically based on the aforementioned ΔT. The It has a positive linear relationship with ΔT, and the injection volume of the HC nozzle is adjusted according to the following formula:

[0033] ;

[0034] In the formula, This represents the actual HC injection volume. The base HC injection quantity is preset based on the target temperature and exhaust heat capacity.

[0035] Furthermore, step S5, the determination of the clearing effect, specifically includes:

[0036] S501. During the crystallization removal process, the SCR conversion efficiency is calculated every third preset time interval. The Calculate using the following formula:

[0037] ;

[0038] S502, when If the crystallization removal effect is determined to be satisfactory when the crystallization removal effect is greater than or equal to the second preset efficiency threshold and the state continues for the fourth preset duration, the crystallization removal process will exit.

[0039] The exit and clearing procedure includes: controlling the three-way electric butterfly valve to switch to the bypass pipeline and following the formula. Calculate the urea injection rate, wherein, the This is a heat storage correction factor, and it is related to the temperature collected by the third temperature sensor. (That is, the temperature at the outlet of the regenerative pipe) shows a positive linear relationship. If the temperature exceeds the second preset temperature threshold, the maximum value will be applied, and a transition period of 5-10 minutes will be allowed until the ECU detects the temperature from the first temperature sensor. When the temperature drops back to between the first and second preset temperature thresholds, control the three-way electric butterfly valve to switch back to the wave-shaped regenerative pipeline channel; if HC injection continues for 40 minutes... If the efficiency is less than the first preset threshold, it is determined that the SCR catalyst is aging or deactivated, the cleaning process is stopped and a fault prompt is triggered.

[0040] Preferably, in the urea crystal removal method, the first temperature threshold is the typical exhaust temperature of the engine operating under medium load; the second temperature threshold is the typical exhaust temperature of the engine operating under high load; the third preset temperature threshold is the temperature value that ensures the SCR urea crystal removal system's regenerative system is in full working condition; the first preset efficiency threshold is the critical benchmark for determining a significant decrease in SCR conversion efficiency; and the second preset efficiency threshold is the critical value used to determine that the urea crystal removal procedure has achieved the expected effect and the SCR system performance has recovered to a healthy level.

[0041] The waste heat recovery-based SCR system urea crystallization intelligent removal control system includes: an electronic control unit (ECU), which can obtain NO through two methods. x Quality-related parameters: First, the real-time nitrogen oxide generation mass of the engine is estimated by combining pre-stored MAP maps. Second, based on NO x The concentration collected by the sensor and the exhaust mass flow rate are calculated according to the formula. Calculate NO x Instantaneous mass, where n is NO x The concentration collected by the sensor, m is the exhaust mass flow rate, and the operation of each actuator is controlled based on the operating data and sensor signals;

[0042] The exhaust treatment unit includes the engine, DOC, DPF, SCR and ASC connected in sequence by the exhaust path;

[0043] A heat recovery device is installed in the gas path between the DPF and the SCR to recover the waste heat at the outlet of the DPF.

[0044] A switching valve is installed at the air inlet of the regenerating device to control whether exhaust gas enters the regenerating device or bypasses the regenerating device.

[0045] An HC nozzle, located in the air passage between the engine and the DOC, is used to inject hydrocarbon fuel into the exhaust to raise its temperature;

[0046] A urea nozzle is installed in the gas path between the regenerative device and the SCR, and is used to spray urea solution into the exhaust gas.

[0047] The sensor array includes at least a plurality of sensors disposed at the inlet and outlet of the regenerator and the inlet and outlet of the SCR, for monitoring exhaust temperature and NO. x At least one parameter of concentration and pressure;

[0048] The input terminal of the electronic control unit is electrically connected to the sensor group and the engine to obtain operating condition data, and the output terminal is electrically connected to the switching valve, the HC nozzle and the urea nozzle to output control commands;

[0049] The electronic control unit is configured to execute the above-described waste heat recovery-based SCR urea crystal removal control method.

[0050] Furthermore, the regenerative device includes: a corrugated regenerative pipe, which is filled with a porous high-temperature resistant ceramic heat storage medium and covered with an insulation layer.

[0051] A bypass pipe is provided in parallel with the corrugated regenerative pipe;

[0052] The switching valve is a three-way electric butterfly valve, with its inlet end connected to the outlet end of the DPF, and its two outlet ends connected to the inlet end of the corrugated regenerative pipeline and the inlet end of the bypass pipeline, respectively.

[0053] Specifically, the regenerative device is an integrated heat storage and heat exchange unit. The diameter of the regenerative pipe needs to be the same as the diameter of the other exhaust pipes. The corrugated design of the regenerative pipe can increase the heat exchange area with the exhaust. The two ends of the regenerative pipe are sealed to the manifold through flanges to achieve sealed flow of exhaust and detachable maintenance of the regenerative pipe.

[0054] Preferably, the corrugated regenerative pipe is provided with a high-temperature resistant heat storage medium inside. The heat storage medium is a high-temperature resistant ceramic material selected from one or more of cordierite, alumina, zirconium oxide toughened alumina, silicon carbide, mullite, and aluminum titanate, and is manufactured in the form of honeycomb, porous foam, granules or regular blocks and placed in the pipe.

[0055] More preferably, the regenerating pipe includes a corrugated pipe shell and a built-in honeycomb ceramic heat storage body. The honeycomb ceramic heat storage body is composed of multiple segments spliced ​​together. The segments of the honeycomb ceramic heat storage body are positioned by a positioning structure. The positioning structure consists of a series of convex keys set on the inner wall of the pipe and corresponding grooves set on the honeycomb ceramic heat storage body. Through the cooperation of the convex keys and grooves, the axial positioning of the honeycomb ceramic heat storage body is achieved and the circumferential rotation of the honeycomb ceramic heat storage body is prevented.

[0056] Furthermore, the sensor group includes a first temperature sensor, which is disposed at the air inlet of the SCR;

[0057] The second temperature sensor is located downstream of the DPF and upstream of the switching valve;

[0058] The third temperature sensor is located at the outlet end of the corrugated regenerative pipe;

[0059] No. 1 x The sensor and the first pressure sensor are disposed between the SCR and the urea nozzle;

[0060] Second NO x A sensor and a second pressure sensor are disposed between the SCR and the ASC;

[0061] No. 1 x The distance between the sensor and the urea nozzle is ≥300mm; and the first NO x The sensor probe has a heating function, and the heating temperature is ≥180℃.

[0062] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0063] 1. This application utilizes temperature-zone-based injection correction and pathway switching to monitor the exhaust temperature at the inlet of the regenerator in real time and compare it with a first preset threshold, thereby differentially controlling the on / off state of the waste heat regeneration pipeline. When the exhaust temperature reaches the threshold, waste heat from the DPF is introduced, significantly reducing the fuel consumption required for active regeneration during crystal removal and improving the overall vehicle fuel economy. Simultaneously, the basic urea injection quantity is adaptively corrected according to different temperature operating ranges, suppressing urea crystal formation at the source while ensuring the catalytic efficiency of the SCR system, achieving the dual technical effects of energy saving and crystal suppression.

[0064] 2. This application uses a crystallization removal procedure for determination and initiation, employing both SCR conversion efficiency and system inlet / outlet differential pressure as dual parameters to collaboratively determine the urea crystallization state. This effectively distinguishes urea crystallization from different fault types such as SCR catalyst aging and DPF blockage. Compared to existing determination schemes that rely on a single parameter, this method significantly improves the accuracy of crystallization identification, ensures precise triggering of the crystallization removal procedure, avoids unnecessary energy consumption and component wear due to misjudgment, and provides a reliable decision-making basis for the subsequent execution of the removal procedure.

[0065] 3. This application employs a crystallization removal mode. During the crystallization removal stage, the HC injection quantity is dynamically adjusted based on the difference between the current temperature and the target temperature, achieving precise control of the SCR inlet temperature. This control strategy ensures that the SCR inlet temperature is effectively raised to the target removal range for complete crystal decomposition, while avoiding localized overheating that could damage the SCR catalyst. This extends the catalyst's lifespan while guaranteeing the removal effect. Furthermore, the determination of the removal effect further ensures the integrity and reliability of the removal process, forming a complete control closed loop.

[0066] 4. This application achieves tiered utilization of waste heat resources through differentiated control logic across different temperature operating ranges. In the low-temperature range, waste heat recovery is shut off and urea injection is reduced to effectively avoid the risk of low-temperature crystallization; in the medium- and high-temperature ranges, waste heat recovery is activated and injection is adaptively adjusted to fully utilize waste heat and improve system efficiency. This zone-adaptive control strategy enables the SCR system to maintain optimal operating conditions across the entire operating range, achieving synergistic optimization of emission compliance, crystallization inhibition, and fuel economy.

[0067] 5. The regenerative device in this application adopts a corrugated regenerative pipeline design, with its inner diameter consistent with the system's exhaust pipeline. This structural design, on the one hand, extends the heat exchange process within a limited space through the corrugated channel, increasing the heat exchange area and thus improving the heat exchange efficiency between the heat storage medium and the exhaust. On the other hand, maintaining a consistent pipe diameter avoids local back pressure surges, effectively controlling exhaust back pressure and reducing adverse effects on engine power and fuel economy. Furthermore, the pipeline ends are connected with flanged seals, ensuring structural reliability and facilitating disassembly and assembly, providing convenience for subsequent inspection, replacement, and system maintenance of the corrugated regenerative pipeline. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the intelligent urea crystal removal control system of the SCR system based on waste heat recovery in a preferred embodiment of the present invention;

[0069] Figure 2 This is a flowchart of a preferred embodiment of the intelligent urea crystal removal control method for an SCR system based on waste heat recovery according to the present invention;

[0070] Figure 3 A flowchart of injection correction and path switching based on temperature zoning, which is a preferred embodiment of the present invention;

[0071] Figure 4 This is a flowchart illustrating the crystallization removal procedure determination and initiation in a preferred embodiment of the present invention;

[0072] Figure 5 A flowchart illustrating the urea crystal removal process in a preferred embodiment of the present invention;

[0073] Figure 6 The flowchart illustrates the urea crystal removal method for determining its removal effect in a specific embodiment of the present invention.

[0074] Reference numerals: 1. ECU; 2. Engine; 3. DOC; 4. DPF; 5. Regenerative device; 6. First temperature sensor; 7. First No. x Sensors; 8. First pressure sensor; 9. SCR; 10. Second pressure sensor; 11. Second No. x Sensor; 12, ASC; 13, HC nozzle; 14, urea nozzle; 15, second temperature sensor; 16, regenerating pipe; 17, third temperature sensor; 18, switching valve; 19, heat storage medium; 20, insulation layer. Detailed Implementation

[0075] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0076] Reference Figure 1 As shown, a preferred embodiment of the present invention, an intelligent urea crystallization removal control system based on waste heat recovery SCR system, includes: an electronic control unit, wherein the electronic control unit is ECU1, which can obtain NO through two methods. x Quality-related parameters: First, the real-time nitrogen oxide generation mass of the engine is estimated by combining pre-stored MAP maps. Second, based on NO x The concentration collected by the sensor and the exhaust mass flow rate are calculated according to the formula. Calculate NO x Instantaneous mass, where n is NO x The concentration collected by the sensor, m is the exhaust mass flow rate, and the operation of each actuator is controlled based on the operating data and sensor signals;

[0077] The exhaust treatment unit includes an engine 2, a DOC (diesel oxidation catalyst) 3, a DPF (diesel particulate filter) 4, an SCR (selective catalytic reduction system) 9, and an ASC (ammonia escape filter) 12 connected in sequence via air passages.

[0078] The heat recovery device 5 is installed in the gas path between the DPF4 and the SCR9 to recover the waste heat at the outlet of the DPF4.

[0079] A switching valve 18 is provided at the air inlet of the regenerating device 5 and is used to control the exhaust gas to enter the regenerating device 5 or bypass the regenerating device 5.

[0080] HC nozzle 13 is disposed in the air passage between the engine 2 and the DOC3, and is used to inject hydrocarbon fuel into the exhaust to raise the temperature;

[0081] Urea nozzle 14 is disposed in the gas path between the regenerator 5 and the SCR9, and is used to spray urea solution into the exhaust gas.

[0082] The sensor array includes at least a plurality of sensors disposed at the inlet and outlet of the regenerator 5 and the inlet and outlet of the SCR9, for monitoring exhaust temperature and NO. x At least one parameter of concentration and pressure;

[0083] The input terminal of the electronic control unit is electrically connected to the sensor group and the engine 2 to obtain operating condition data, and the output terminal is electrically connected to the switching valve 18, the HC nozzle 13 and the urea nozzle 14 to output control commands.

[0084] The electronic control unit is configured to execute the above-described waste heat recovery-based SCR urea crystal removal control method.

[0085] In this embodiment, the sensor group includes a first temperature sensor 6, which is disposed at the air inlet of the SCR9;

[0086] The second temperature sensor 15 is located downstream of the DPF and upstream of the switching valve;

[0087] The third temperature sensor 17 is located at the outlet end of the corrugated regenerative pipe;

[0088] No. 1 x Sensor 7 and first pressure sensor 8 are disposed between the SCR9 and the urea nozzle 14; the first NO x Sensor 7 is used to collect NO upstream of the SCR. x The concentration is collected and transmitted back to the ECU; the first pressure sensor 8 is used to collect the pressure upstream of the SCR and transmit it back to the ECU.

[0089] Second NO x Sensor 11 and second pressure sensor 9 are disposed between the SCR and the ASC. x Sensor 11 is used to collect NO downstream of SCR. x The concentration is collected and transmitted back to the ECU; the second pressure sensor 9 is used to collect the pressure downstream of the SCR and transmit it back to the ECU.

[0090] In a preferred embodiment of the present invention, the signal input terminal of ECU1 is connected to the engine 2, the first temperature sensor 6, the second temperature sensor 15, the third temperature sensor 17 of the regeneration device 5, and the first NO x Sensor 7, Second NO x Sensor 11 is electrically connected to acquire engine operating condition data, SCR operating condition data, DPF carbon load, exhaust real-time temperature data, and heat storage and heat exchange temperature data. x Concentration data; the signal output terminal of the ECU1 is electrically connected to the three-way electric butterfly valve, HC nozzle 13, and urea nozzle 14 of the regenerating device 5.

[0091] It should be noted that the urea injector 14 is part of the vehicle's exhaust gas purification system. Under the control of ECU1, it injects the corresponding amount of urea according to the current urea injection requirements of the engine. The HC injector 13 is part of the DPF active regeneration system. Under the control of ECU1, it injects the corresponding amount of fuel. After a fixed amount of fuel is injected into the exhaust pipe in front of the DOC, the fuel will react with the DOC to produce NO2 and heat, thereby increasing the exhaust temperature and reacting with the carbon particles in the DPF to complete the active regeneration of the DPF. In this invention, when the crystal removal program is activated, the HC injector will inject a certain amount of fuel according to the current operating conditions and target temperature to increase the exhaust temperature, thereby burning off the urea crystals attached to the SCR catalyst.

[0092] In this embodiment, the heat recovery device 5 includes: a corrugated heat recovery pipe 16, which is filled with a porous high-temperature resistant ceramic heat storage medium 19 and covered with an insulation layer 20.

[0093] A bypass pipe is connected in parallel with the corrugated regenerative pipe 16;

[0094] The switching valve 18 is a three-way electric butterfly valve, with its inlet end connected to the outlet end of the DPF, and its two outlet ends connected to the inlet end of the corrugated regenerative pipe and the inlet end of the bypass pipe, respectively.

[0095] Specifically, the regenerative device is an integrated heat storage and heat exchange unit. The diameter of the regenerative pipe 16 needs to be the same as the diameter of the other exhaust pipes. The corrugated or S-shaped design of the regenerative pipe 16 can increase the heat exchange area with the exhaust. The two ends of the regenerative pipe 16 are sealed to the manifold through flanges to achieve sealed flow of exhaust and detachable maintenance of the regenerative pipe.

[0096] It should be noted that, in another optional embodiment, to achieve lower flow resistance, the inner diameter of the corrugated regenerative pipe 16 can be designed to be larger than the inner diameter of the system piping. In this case, the outer diameter of the honeycomb ceramic heat storage body should be increased to maintain a high fill rate, and interface contact should be ensured by installing a thermally conductive gasket. This method is suitable for applications with extreme requirements for exhaust back pressure.

[0097] In this embodiment, the corrugated regenerative pipe 16 is provided with a high-temperature heat storage medium. The heat storage medium 19 is a high-temperature resistant ceramic material selected from one or more of cordierite, alumina, zirconium oxide toughened alumina, silicon carbide, mullite, and aluminum titanate, and is manufactured in the form of honeycomb, porous foam, granules, or regular blocks and placed in the pipe.

[0098] In this embodiment, the regenerative pipe includes a corrugated pipe shell and a built-in honeycomb ceramic heat storage body. The honeycomb ceramic heat storage body is composed of multiple segments spliced ​​together. The segments of the honeycomb ceramic heat storage body are positioned by a positioning structure. The positioning structure consists of a series of convex keys set on the inner wall of the pipe and corresponding grooves set on the honeycomb ceramic heat storage body. Through the cooperation of the convex keys and grooves, the axial positioning of the honeycomb ceramic heat storage body is achieved and the circumferential rotation of the honeycomb ceramic heat storage body is prevented.

[0099] It should be noted that, in this embodiment, the processing and assembly method of the corrugated regenerative pipe 16 is as follows: the honeycomb ceramic body is decomposed into several short straight honeycomb ceramic cores, with a single segment length of 100-200mm. During installation, care should be taken to ensure that the exhaust can flow normally. In order to ensure that the exhaust can flow normally, some pipes can be installed at intervals. High-temperature resistant ceramic fiber felt is wrapped around the outer wall of the short straight honeycomb ceramic body to fill the gap with the inner wall of the continuous corrugated regenerative pipe.

[0100] In another alternative implementation, the honeycomb ceramic body can be customized into multiple corrugated honeycomb ceramic bodies and short straight honeycomb ceramic bodies for installation.

[0101] In this embodiment, the first NO x The distance between the sensor and the urea nozzle is ≥300mm; and the first NO x The sensor probe has a heating function, with a heating temperature ≥180℃. It should be noted that, in order to ensure NO... x The sensor can operate stably, and it is the first NO upstream of the SCR. x The sensor 7 and the urea nozzle 14 need to be installed at a certain distance, and a certain operating temperature is required to prevent the probe from being corroded by condensation and acidic gases.

[0102] Reference Figures 2-6 As shown, a preferred embodiment of the present invention, a smart urea crystallization removal control method for SCR systems based on waste heat recovery, includes the following steps:

[0103] It should be noted that, in a preferred embodiment of the present invention, all correction coefficients are obtained through bench tests, and the specific calibration process is as follows:

[0104] 1. Low temperature correction factor and heat storage correction coefficient Simulate different exhaust temperatures on an engine test bench. The urea pyrolysis efficiency was tested at various temperature points to ensure the actual urea injection volume. The corresponding pyrolysis product NH3 can meet the target conversion efficiency of SCR while minimizing crystal formation, thus ultimately determining... The value can be [0.1, 0.6]. The value is [0.6, 1.0].

[0105] 2. HC injection correction coefficient Simulate different temperature differences on an engine test bench The relationship between HC injection quantity and exhaust gas temperature rise rate was tested to ensure that the target temperature rise effect was achieved with the lowest HC consumption. The final calibration yielded... The value range is [0.1, 1.0].

[0106] S1. Determination of basic urea injection quantity: Obtain the current operating parameters of the engine and determine the basic urea injection quantity based on the preset SCR basic control strategy.

[0107] Specifically, the current operating parameters of the engine include nitrogen oxide generation, SCR target conversion efficiency, and urea nitrogen content; the basic urea injection quantity is calculated using the following formula:

[0108] ;

[0109] In the formula, m NOx This refers to the real-time estimated amount of nitrogen oxides generated by the engine; η is the nitrogen mass fraction of urea (using industry standard 32.5% automotive urea, its nitrogen mass fraction η=0.466 is an inherent property and requires no additional calibration); M... urea The molar mass of urea is 60 g / mol (an inherent chemical property); the M... N The molar mass of nitrogen atoms (14 g / mol, an inherent chemical property); the η SCR Set the SCR target conversion efficiency (manually preset to 90%).

[0110] S2. Injection correction and path switching based on temperature zone: Real-time monitoring of the exhaust temperature at the inlet of the regenerating device, dividing different temperature working ranges according to the comparison result between the exhaust temperature and the first preset temperature threshold, controlling the on / off state of the waste heat regenerating pipe under different temperature working ranges, and adaptively correcting the basic urea injection amount to obtain the actual urea injection amount.

[0111] It should be noted that, in a preferred embodiment of the present invention, the first preset temperature threshold is set to 250°C; the second preset temperature threshold is set to 450°C; the third preset temperature threshold is set to 250°C; the first preset pressure threshold is set to 5 kPa; the first preset efficiency threshold is set to 80%; and the second preset efficiency threshold is set to 90%.

[0112] This step specifically includes:

[0113] S201, when T 15At temperatures below 250℃, the three-way electric butterfly valve is switched to the bypass pipeline and not connected to the regenerative pipeline; this T 15 The actual urea injection volume is adjusted according to the following formula, based on the temperature collected by the first temperature sensor 15: ;

[0114] In the formula, This represents the actual amount of urea injected. This is the low-temperature correction factor, with values ​​ranging from [0.1, 0.6], and it is related to T. 15 It is a positive linear relationship;

[0115] S202, when T 15 At ≥250℃, the three-way electric butterfly valve is switched to the regenerative pipeline, and the actual urea injection volume is expressed by the following formula: ;

[0116] In the formula, The heat storage correction factor has a value of [0.6 1.0] and is related to the temperature T collected by the third temperature sensor. 17 It is a positive linear relationship, T 17 At ≥450℃, Take the maximum value of 1.0.

[0117] It should be noted that due to the high risk of urea crystallization during cold starts of automobiles, especially when the exhaust is cold, the waste heat utilization efficiency is low, which may also lead to slow exhaust temperature rise and exacerbate urea crystallization. Therefore, temperature zone adaptive control is adopted to avoid the exacerbation of urea crystallization due to heat absorption by the regeneration device during cold starts.

[0118] It should be further noted that, in a preferred embodiment, ECU1 reads T with a control cycle of approximately 100ms. 15 With T 17 Based on the current temperature, the system performs corresponding control actions while calculating the actual urea injection volume and then fine-tunes the urea injection volume accordingly.

[0119] S3. Crystallization Removal Program Judgment and Activation: Based on the SCR conversion efficiency and the differential pressure between the SCR inlet and outlet, combined with preset conditions, determine whether urea crystals are present; when urea crystals are detected and the preset activation conditions are met, the crystallization removal program is triggered.

[0120] This step specifically includes:

[0121] S301. Preset start-up basic conditions, including engine running time ≥10min, no SCR catalyst aging or deactivation fault codes, and DPF carbon load below a preset safety threshold.

[0122] It should be noted that because the target temperature for crystallization removal (600℃-700℃) is higher than the target temperature for DPF regeneration (500℃), the amount of fuel injected for crystallization removal will be higher than that for DPF regeneration. To avoid the high-temperature buildup during crystallization removal causing rapid combustion of carbon deposits in the DPF and resulting in DPF burnout, the carbon load of the DPF must be kept below the crystallization removal carbon load threshold when starting the urea crystallization removal process.

[0123] S302. Conversion Efficiency Monitoring: The ECU calculates the SCR conversion efficiency every 2 seconds using the following formula, and collects data continuously for 30 seconds, taking the average value. ;

[0124] The Calculate using the following formula:

[0125] ;

[0126] In the formula, NO xup NO at the SCR intake end x Concentration, NO xdown NO at the SCR outlet x concentration;

[0127] S303, ECU continuous monitoring and the differential pressure between the SCR inlet and outlet , like <80%, ΔP≥5kPa, and lasting for 30 seconds, is determined to be urea crystallization; if only <80% but Based on the historical health baseline of the SCR catalyst, it is determined to be either aging or deactivated; if only ≥5kPa but If the problem is determined to be DPF blockage or exhaust pipe malfunction, the urea crystal removal procedure will not be initiated.

[0128] S304. Startup Confirmation: If the T6 collected by the first temperature sensor is ≥250℃ and is determined to be crystallization, start the urea crystal removal program.

[0129] S4. Crystallization removal program execution: Set the crystallization removal target temperature, and dynamically adjust the HC injection volume according to the difference between the current temperature and the target temperature to raise the SCR inlet temperature to the target removal temperature range.

[0130] This step specifically includes:

[0131] S401, Set the target temperature for crystal removal. The The preset value is 500-700℃; the current temperature T is collected by the third temperature sensor 17. 17 Calculate the temperature difference ;

[0132] S402, Determine the HC injection correction coefficient dynamically based on the aforementioned ΔT. The value range is [0.1, 1.0]; and the stated It has a positive linear relationship with ΔT, and the injection volume of the HC nozzle is adjusted according to the following formula:

[0133] ;

[0134] In the formula, This represents the actual HC injection volume. The base HC injection quantity is preset based on the target temperature and exhaust heat capacity.

[0135] It should be noted that, in a preferred embodiment, to achieve optimal temperature control accuracy and response speed, the ECU reads T with a control cycle of approximately 100ms. 17 The deviation ΔT between the value and the target value is calculated, and the urea injection volume is finely adjusted accordingly.

[0136] S5. Determination of Removal Effectiveness: Monitor SCR conversion efficiency during the removal process. ,when The crystallization removal procedure will terminate when the preset exit conditions are met.

[0137] This step specifically includes:

[0138] S501. During the crystallization removal process, the SCR conversion efficiency is calculated every 3 minutes. The Calculate using the following formula:

[0139] ;

[0140] S502, when If the crystallization rate is ≥90% and this state lasts for 30 seconds, the crystallization removal effect is considered to be up to standard, and the crystallization removal procedure is exited.

[0141] It should be noted that the exit and clearing procedure includes: controlling the three-way electric butterfly valve to switch to the bypass pipeline and following the formula. Calculate the urea injection rate, wherein, the The heat storage correction coefficient has a value of [0.6, 1.0]; and is related to the temperature T collected by the third temperature sensor 17. 17 (That is, the temperature at the outlet of the regenerator pipe) has a positive linear relationship, T 17 For temperatures ≥450℃, take the maximum value of 1.0, transition for 5-10 minutes, and wait until the ECU detects that the temperature T6 of the first temperature sensor has dropped back to between 250-450℃. Then, control the three-way electric butterfly valve to switch back to the wave-shaped regenerative pipeline channel. If HC injection continues for 40 minutes... If the SCR catalyst aging or deactivation rate is less than 80%, the cleaning process will be stopped and a fault message will be triggered.

[0142] It should be further explained that the reason for setting up the above-mentioned exit cleaning procedure is that the SCR catalyst has an optimal operating temperature window, which is significantly lower than the temperature required for effective removal of urea crystals. If the high-temperature exhaust continues to flow through the regenerator after the cleaning procedure is completed, the SCR catalyst temperature will become too high, and its catalytic efficiency will decrease. Therefore, the system needs to first switch to the bypass pipe to moderately reduce the exhaust temperature before reconnecting to the corrugated regenerator pipe 16, thereby stabilizing the SCR catalyst temperature within the high-efficiency operating range.

[0143] Preferably, in the urea crystal removal method, the first temperature threshold is the typical exhaust temperature of the engine operating under medium load; the second temperature threshold is the typical exhaust temperature of the engine operating under high load; the third preset temperature threshold is the temperature value that ensures the SCR urea crystal removal system's regenerative system is in full working condition; the first preset efficiency threshold is the critical benchmark for determining a significant decrease in SCR conversion efficiency; and the second preset efficiency threshold is the critical value used to determine that the urea crystal removal procedure has achieved the expected effect and the SCR system performance has recovered to a healthy level.

[0144] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0145] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for intelligent removal and control of urea crystallization in an SCR system based on waste heat recovery, characterized in that, Includes the following steps: S1. Determination of basic urea injection quantity: Obtain the current operating parameters of the engine and determine the basic urea injection quantity based on the preset SCR basic control strategy. S2. Injection correction and path switching based on temperature zone: Real-time monitoring of the exhaust temperature at the inlet of the regenerator, dividing different temperature working ranges according to the comparison result between the exhaust temperature and the first preset temperature threshold, controlling the on / off state of the regenerator in different temperature working ranges, and adaptively correcting the basic urea injection quantity to obtain the actual urea injection quantity. S3. Crystallization removal procedure determination and start-up: Based on the SCR conversion efficiency and the differential pressure between the SCR inlet and outlet, combined with preset conditions, determine whether urea crystals are present. When urea crystals are detected and the preset activation conditions are met, the crystal removal procedure is triggered. S4. Crystallization removal program execution: Set the crystallization removal target temperature, and dynamically adjust the HC injection volume according to the difference between the current temperature and the target temperature to raise the SCR inlet temperature to the target removal temperature range. S5. Determination of Removal Effectiveness: Monitor SCR conversion efficiency during the removal process. ,when The crystallization removal procedure will exit when the preset exit conditions are met.

2. The intelligent urea crystallization removal control method for SCR systems based on waste heat recovery according to claim 1, characterized in that: The current engine operating parameters in step S1 include one or more of the following: nitrogen oxide generation, SCR target conversion efficiency, and urea nitrogen content; the basic urea injection quantity is calculated using the following formula: ； In the formula, m NOx The real-time estimated amount of nitrogen oxides generated by the engine; η is the nitrogen mass fraction of urea; M urea M is the molar mass of urea; N The molar mass of nitrogen atoms; the η SCR The target conversion efficiency for SCR.

3. The intelligent urea crystallization removal control method for SCR systems based on waste heat recovery according to claim 1, characterized in that: Step S2, injection correction and path switching based on temperature zones, includes: S201. When the DPF outlet temperature is less than the first preset temperature threshold, the control switching valve switches to the bypass pipe and does not connect to the regenerative pipe; the actual urea injection volume is adjusted according to the following formula: ; In the formula, This represents the actual amount of urea injected. This is a low-temperature correction factor, and it has a positive linear relationship with the outlet temperature of the DPF. S202. When the DPF outlet temperature is ≥ the first preset temperature threshold, the control switching valve switches to the regenerative pipeline, and the actual urea injection quantity is expressed by the following formula: ; In the formula, It has a positive linear relationship with the temperature at the outlet of the regenerative pipe, and when the temperature at the outlet of the regenerative pipe is ≥ the second preset temperature threshold, Take the maximum value.

4. The intelligent urea crystallization removal control method for SCR systems based on waste heat recovery according to claim 1, characterized in that: The specific steps of determining and initiating the crystallization removal procedure in step S3 include: S301. Preset start-up basic conditions, the basic conditions include engine running time not less than a first preset duration, no SCR catalyst aging or deactivation fault codes, and DPF carbon load lower than a preset safety threshold. S302. Real-time monitoring of SCR conversion efficiency R and the pressure difference ΔP between the SCR inlet and outlet ends, wherein the SCR conversion efficiency R is calculated using the following formula: ； In the formula, NO xup NO at the SCR intake end x Concentration, NO xdown NO at the SCR outlet x concentration; S303. When R < first preset efficiency threshold and ΔP ≥ first preset pressure threshold, and this state continues for a second preset duration, it is determined to be urea crystallization. S304. When the basic conditions are met and it is determined that urea crystals are formed, further determine whether the SCR inlet temperature is greater than the third preset temperature threshold. If so, trigger the crystal removal procedure.

5. The intelligent urea crystallization removal control method for SCR systems based on waste heat recovery according to claim 4, characterized in that: It also includes a fault differentiation step: when R < first preset efficiency threshold and ΔP < first preset pressure threshold, it is determined to be catalyst aging or deactivation based on the historical health baseline of the SCR catalyst. When ΔP ≥ the first preset pressure threshold and R ≥ the first preset efficiency threshold, it is determined that the DPF is blocked or the exhaust pipe is faulty, and the urea crystal removal procedure is not started.

6. The intelligent urea crystallization removal control method for SCR systems based on waste heat recovery according to claim 1, characterized in that: The specific steps of the crystal removal procedure in step S4 include: S401, Set the target temperature for crystal removal. The The preset value is 500-700℃; the temperature at the outlet of the regenerating pipe is monitored in real time, and the temperature difference ΔT between it and the target temperature is calculated. S402, Determine the HC injection correction coefficient dynamically based on the aforementioned ΔT. The It has a positive linear relationship with ΔT, and the injection volume of the HC nozzle is adjusted according to the following formula: ； In the formula, This represents the actual HC injection volume. The base HC injection quantity is preset based on the target temperature and exhaust heat capacity.

7. The intelligent urea crystallization removal control method for SCR systems based on waste heat recovery according to claim 1, characterized in that: The specific steps of determining the removal effect in step S5 include: S501. During the crystallization removal process, the SCR conversion efficiency is calculated every third preset time interval. The Calculate using the following formula: ； S502, when If the crystallization removal process is terminated when the crystallization effect is determined to be satisfactory, and the state is maintained for a fourth preset duration, the crystallization removal process is terminated.

8. A smart urea crystallization removal control system for SCR systems based on waste heat recovery, characterized in that, include: Electronic control unit; The exhaust treatment unit includes the engine, DOC, DPF, SCR and ASC connected in sequence by the exhaust path; A heat recovery device is installed in the gas path between the DPF and the SCR to recover the waste heat at the outlet of the DPF. A switching valve is installed at the air inlet of the regenerating device to control whether exhaust gas enters the regenerating device or bypasses the regenerating device. An HC nozzle, located in the air passage between the engine and the DOC, is used to inject hydrocarbon fuel into the exhaust to raise its temperature; A urea nozzle is installed in the gas path between the regenerative device and the SCR, and is used to spray urea solution into the exhaust gas. The sensor array includes at least a plurality of sensors disposed at the inlet and outlet of the regenerator and the inlet and outlet of the SCR, for monitoring exhaust temperature and NO. x At least one parameter of concentration and pressure; The input terminal of the electronic control unit is electrically connected to the sensor group and the engine to obtain operating condition data, and the output terminal is electrically connected to the switching valve, the HC nozzle and the urea nozzle to output control commands; The electronic control unit is configured to perform the SCR urea crystallization removal control method based on waste heat recovery as described in any one of claims 1-6.

9. The intelligent urea crystallization removal control system for SCR system based on waste heat recovery as described in claim 8, characterized in that: The regenerative device includes: a corrugated regenerative pipe, which is filled with a porous high-temperature resistant ceramic heat storage medium and covered with an insulation layer. A bypass pipe is provided in parallel with the corrugated regenerative pipe; The switching valve is a three-way electric butterfly valve, with its inlet end connected to the outlet end of the DPF, and its two outlet ends connected to the inlet end of the corrugated regenerative pipeline and the inlet end of the bypass pipeline, respectively.

10. The intelligent urea crystallization removal control system for SCR systems based on waste heat recovery as described in claim 8, characterized in that: The sensor group includes a first temperature sensor, which is disposed at the air inlet of the SCR; The second temperature sensor is located downstream of the DPF and upstream of the switching valve; The third temperature sensor is located at the outlet end of the corrugated regenerative pipe; No. 1 x The sensor and the first pressure sensor are disposed between the SCR and the urea nozzle; Second NO x A sensor and a second pressure sensor are disposed between the SCR and the ASC; The first NO x The distance between the sensor and the urea nozzle is ≥300mm; and the first NO x The sensor probe has a heating function, and the heating temperature is ≥180℃.

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