A method for solving high-temperature crystallization blockage of a urea nozzle of a range extender vehicle

Abstract

The application discloses a method for solving high-temperature crystallization blockage of a urea nozzle of a range extender vehicle, and relates to the technical field of engines.The method comprises the following steps: when preset function release conditions are met, the exhaust temperature and the exhaust flow at the engine shutdown time are obtained, the expected temperature of the urea nozzle after shutdown is calculated from a pre-marked nozzle temperature rise Map1, the required temperature drop At is calculated according to the expected temperature and a preset target temperature, the urea injection amount and the injection frequency are interpolated from a pre-marked nozzle temperature drop Map2, and the urea is continuously injected according to the urea injection amount and the injection frequency, so that the heat accumulated in the nozzle is removed.The application can effectively reduce the temperature of the urea nozzle after the engine is shutdown, avoid high-temperature crystallization blockage and hardware damage of the nozzle, prevent emission from exceeding the standard and the vehicle from being limited in speed and torque, reduce the maintenance cost, and guarantee normal operation of the vehicle.

Description

Technical Field

[0001] This invention relates to the technical field of automobiles and engines, and in particular to a solution for high-temperature crystallization blockage of urea nozzles in range extender vehicles, especially to the treatment of high-temperature crystallization of urea nozzles in engine aftertreatment systems. Background Technology

[0002] With increasingly stringent emission regulations, selective catalytic reduction (SCR) technology has been widely applied in diesel engine aftertreatment systems. The SCR system injects urea solution into the exhaust pipe through a urea nozzle. The urea solution is hydrolyzed to generate ammonia, which then reacts with nitrogen oxides in the exhaust gas, thereby reducing nitrogen oxide emissions.

[0003] In existing technologies, urea nozzles primarily rely on engine coolant and urea solution for cooling to prevent overheating and damage in the high-temperature exhaust environment. However, after the engine stops, the coolant ceases circulation, and urea injection also stops. At this time, the heat accumulated in the aftertreatment device continues to be transferred to the urea nozzle through heat conduction and radiation, causing the nozzle temperature to rise further. The urea solution remaining in the nozzle is prone to crystallization at high temperatures, leading to nozzle blockage or even damage.

[0004] Especially in recent years, with the increasing popularity of range extender vehicles, the engines of these vehicles need to be frequently started and stopped according to the vehicle's battery level and operating conditions. Frequent engine shutdowns at high temperatures exacerbate the problem of high-temperature crystallization and clogging of the urea injectors. This clogging not only leads to excessive emissions and environmental pollution but may also activate the vehicle's speed and torque limiting functions, affecting normal vehicle operation. Currently, there are no effective measures to reduce the urea injector temperature after the engine stops. Frequent high-temperature start-stop cycles pose a high risk of urea injector damage, requiring replacement only after high-temperature crystallization and damage, resulting in high maintenance costs.

[0005] Therefore, how to provide a method to effectively reduce the temperature of the urea nozzle and avoid high-temperature crystallization and blockage of the urea nozzle after the engine is shut down has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a solution for high-temperature crystallization blockage of urea nozzles in range extender vehicles. This addresses the problem that after frequent engine start-stop cycles and high-temperature shutdowns in range extender vehicles, heat from the aftertreatment system is conducted and radiated, leading to high-temperature crystallization blockage of the urea nozzles, which in turn causes excessive emissions and affects vehicle speed and torque limits. The method of this invention effectively reduces the temperature of the urea nozzles after the engine is stopped, preventing high-temperature crystallization damage and thus avoiding excessive engine emissions, ensuring that the driver's normal production and work are not affected.

[0007] To achieve the above objectives, the technical solution of the present invention provides a solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles, comprising the following steps:

[0008] When the preset function release conditions are met, obtain the exhaust temperature and exhaust flow rate at the moment the engine stops; Based on the exhaust temperature and exhaust flow rate at the time of engine shutdown, the expected temperature of the urea nozzle after engine shutdown is calculated from the pre-calibrated urea nozzle temperature rise Map1. The required temperature drop Δt is calculated based on the expected temperature and the preset target temperature. Based on the required temperature drop Δt, the corresponding urea injection quantity and injection frequency are interpolated from the pre-calibrated urea nozzle temperature drop Map2; Urea is continuously injected into the urea nozzle according to the interpolated urea injection volume and injection frequency. The urea solution carries away the heat accumulated in the urea nozzle, thereby reducing the urea nozzle temperature and preventing high-temperature crystallization and blockage of the urea nozzle.

[0009] Preferably, when a fault is detected in the urea injection system, the process of troubleshooting and resolving the fault is initiated and terminated after the fault is resolved, without executing the shutdown and cooling injection.

[0010] Preferably, the pre-calibration step of urea nozzle temperature rise Map1 is as follows: using a urea temperature measuring nozzle, under different exhaust flow rates and different exhaust temperature combinations, test the highest temperature that the urea nozzle can reach after the engine stops, and pre-calibrate the highest temperature in urea nozzle temperature rise Map1 to establish the correspondence between exhaust temperature and exhaust flow rate at the time of shutdown and the expected highest temperature of urea nozzle after shutdown.

[0011] Preferably, the pre-calibration step of urea nozzle temperature drop Map2 is as follows: at different initial temperatures of urea nozzles, urea is injected with a preset injection volume and a preset frequency, the temperature drop of urea nozzle after urea injection is tested, and the temperature drop data is pre-calibrated in urea nozzle temperature drop Map2 to establish the correspondence between nozzle temperature, cooling requirements and required urea injection volume and injection frequency.

[0012] Preferably, the exhaust flow rate at the time of shutdown is estimated by an exhaust flow rate estimation model, that is, based on the operating parameters of the engine before shutdown, the exhaust flow rate at the time of shutdown is estimated by a pre-established exhaust flow rate estimation model.

[0013] Preferably, the preset target temperature is 115°C, which is lower than the crystallization risk threshold temperature of 120°C for urea nozzles, in order to allow for error margin.

[0014] Preferably, the urea injection cooling process is an open-loop control, that is, the injection is performed directly based on the urea injection quantity and injection frequency calculated by interpolation of urea nozzle temperature rise Map1 and urea nozzle temperature drop Map2, without real-time monitoring and feedback correction of nozzle temperature.

[0015] Preferably, when the expected temperature of the urea nozzle calculated according to the urea nozzle temperature rise Map1 does not exceed the preset target temperature, it is determined that there is no risk of crystallization, and the injection system back-drawing operation is performed to draw back the urea solution in the injection pipeline and end the process.

[0016] Preferably, the preset function release conditions include: engine speed less than 200 rpm; exhaust temperature before SCR aftertreatment greater than 200°C; urea pump pressure within 8500 hpa to 9500 hpa; and no faults in the urea injection system and related hardware.

[0017] Preferably, the process is only executed after the engine is shut down; urea injection is controlled by closed-loop logic during normal engine operation.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides a solution for high-temperature crystallization blockage of urea nozzles in range extender vehicles. After the engine is shut down, the heat accumulated in the urea nozzle is carried away by predicting the nozzle temperature rise and continuously spraying urea solution at a low frequency. This avoids high-temperature crystallization in the urea nozzle, prevents prolonged crystallization from causing hardware damage to the urea nozzle, and reduces maintenance costs. At the same time, it avoids excessive emissions and environmental pollution caused by nozzle damage, and avoids activating vehicle speed limiting and torque limiting functions, ensuring that the driver's normal production operations are not affected. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating a solution to high-temperature crystallization blockage of urea nozzles in range extender vehicles according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention discloses a solution to the high-temperature crystallization clogging of urea nozzles in range-extender vehicles. This method is applicable to diesel commercial vehicles equipped with range extenders. During operation, the engine of a range-extender vehicle needs to be frequently started and stopped according to the vehicle's battery level and operating conditions. After the engine is shut down at high temperatures, the coolant stops circulating, and urea injection is also interrupted. The large amount of heat accumulated in the aftertreatment device will be continuously transferred to the urea nozzle through heat conduction and heat radiation, further increasing the nozzle temperature. As a result, the residual urea solution in the nozzle crystallizes at high temperatures, leading to nozzle clogging or even damage.

[0022] The basic principle of the method provided in this embodiment is as follows: After the engine stops, the amount of nozzle temperature rise caused by heat conduction and radiation from the aftertreatment system is predicted. Then, through continuous low-frequency urea injection, the urea solution carries away the heat accumulated in the urea nozzle, thereby preventing high-temperature crystallization and blockage of the urea nozzle. It should be noted that this method is only executed after the engine is shut down. When the engine is running normally and starting up, urea injection is still controlled according to the original closed-loop logic, that is, normal urea injection is performed according to the nitrogen oxide emission requirements. The two do not affect each other and each performs its own function to jointly ensure the reliable operation of the aftertreatment system under all operating conditions.

[0023] The solution to the high-temperature crystallization blockage of the urea nozzle first includes the steps of determining the release conditions through functional testing. For example... Figure 1 As shown, after the system starts, it needs to collect and determine whether the following conditions are met: 1. Collect engine speed data. The engine speed must be less than 200 rpm to determine whether the engine is about to stop or has already stopped. 2. Collect the exhaust temperature before the SCR in post-processing. The exhaust temperature must be greater than 200℃ to determine whether there is enough heat accumulated in the post-processing device to cause the nozzle temperature to rise and crystallize. If the exhaust temperature is lower than this value, there is no need to activate the cooling protection. 3. Collect the urea pump pressure. The urea pump pressure should be within 8500 hpa to 9500 hpa to ensure that the urea solution has a normal and stable injection pressure during the subsequent cooling injection process. Here, hpa is hectopascals, and 1 hpa equals 100 Pa. 4. It is necessary to confirm that the urea injection system or other related hardware is fault-free. If there is a fault in the injection system, the process will proceed to the branch process of troubleshooting and resolving the fault. The process will end after the fault is resolved to avoid secondary damage or misjudgment caused by performing cooling injection under system fault conditions.

[0024] Only after all the above release conditions are met will the system be allowed to enter the subsequent shutdown and cooling control logic.

[0025] The method also includes a urea nozzle temperature map pre-calibration step, which is completed in advance through testing during the vehicle or engine development phase: 1. A specially designed urea temperature measuring nozzle is used to measure the temperature rise of the urea nozzle after the engine is stopped and the temperature drop after urea injection. 2. Under different exhaust flow rates and different exhaust temperatures, such as an exhaust flow rate of 1000 kg / h and an exhaust temperature of 50℃, test the highest temperature that the urea nozzle can reach after the engine is shut down, and pre-calibrate this temperature into the urea nozzle temperature rise Map1. Map1 establishes the correspondence between the exhaust temperature and exhaust flow rate at the time of shutdown and the expected highest temperature of the nozzle after shutdown. 3. At different initial temperatures of urea nozzles, urea is injected at a certain frequency, such as once every 15 seconds with a urea injection volume of 100mg. The temperature drop of the nozzle after urea injection is tested, and the temperature drop data is pre-calibrated in the urea nozzle temperature drop Map2. Map2 thus establishes the correspondence between nozzle temperature, cooling requirements and required urea injection volume and injection frequency.

[0026] It should be noted that the calibration of Map1 and Map2 did not take into account the influence of ambient temperature. This is because the increase in urea nozzle temperature is mainly caused by heat conduction and heat radiation from the aftertreatment device. The aftertreatment temperature is generally in the range of 200℃ to 650℃. In comparison, the influence of ambient temperature is very small and can be ignored. Therefore, there is no need to introduce an ambient temperature correction factor during the calibration process.

[0027] After the engine is shut down, the method enters the urea injection cooling control step to prevent nozzle blockage due to high-temperature crystallization: 1. When the engine is determined to be stopped and its speed is 0, the system calculates the expected temperature of the urea nozzle from the pre-calibrated Map1 based on the exhaust temperature and flow rate at the time of engine shutdown. It should be noted that the exhaust gas flow sensor usually cannot accurately measure the exhaust flow rate after the engine is stopped. Therefore, the exhaust flow rate in this embodiment is obtained through model estimation. That is, based on the operating parameters before the engine is stopped, the exhaust flow rate value at the time of shutdown is estimated through a pre-established exhaust flow rate estimation model, and then substituted into Map1 to calculate the expected nozzle temperature. 2. According to industry experience, there is no risk of crystallization when the urea nozzle temperature is below 120℃, and the risk of crystallization increases with increasing temperature when the temperature is above 120℃. 3. The target temperature of the nozzle is controlled to be less than 115℃, that is, a certain error margin is reserved on the basis of the safety threshold of 120℃; the system calculates the required temperature drop Δt based on the expected temperature of the nozzle obtained from the temperature rise Map1, that is, the difference between the expected temperature of the nozzle and the target temperature. 4. Based on the calculated Δt, interpolate the corresponding urea injection quantity and injection frequency from the temperature drop Map2, and continuously inject urea according to the interpolated urea injection quantity and injection frequency to cool down the urea nozzle.

[0028] 5. If the urea nozzle temperature calculated by Map1 does not exceed 115℃, it indicates that there is no risk of crystallization. The system determines that the engine is shut down normally and performs a reverse pumping operation of the injection system to pump back the urea solution in the injection pipeline to prevent residual urea from crystallizing in the pipeline.

[0029] It should be further explained that the above-mentioned cooling injection process is an open-loop control, meaning that the system does not monitor the nozzle temperature in real time for feedback correction during the injection process. Instead, it directly executes the injection based on the injection volume and injection frequency calculated by interpolation of Map1 and Map2. To prevent over-injection or insufficient cooling due to Map calibration deviation, this embodiment sets the preset target temperature to 115℃ to allow for an error margin. Since temperatures below 120℃ are considered safe, even if there is a certain deviation in Map calibration, the actual nozzle temperature remains within a safe range without the risk of crystallization, thus balancing sufficient cooling with economical urea consumption. In addition, to avoid the risk of unlimited injection or urea depletion in extreme situations such as long-term parking in high-temperature environments, this embodiment sets a maximum time limit for the injection cooling process, which is 5 minutes. That is, regardless of whether the cooling target is achieved, the injection cooling process will terminate after a maximum of 5 minutes, thereby achieving a balance between protecting the nozzle and controlling urea consumption.

[0030] The method concludes with the step of outputting the results: 1. During the cooling injection process, if the cooling has not been completed, the system will output the prompt message "Urea nozzle is cooling down, do not turn off the main power" to remind the driver or operator to keep the vehicle powered to ensure that the urea pump and injection system can continue to complete the cooling operation. 2. If cooling is complete, the system will output the message "Urea nozzle has cooled down and power can be cut off", informing the driver or operator that it is safe to disconnect the vehicle's main power supply at this time, and then the process will end.

[0031] The above status output can effectively prevent users from accidentally disconnecting the power during the cooling process, which could lead to cooling interruption or nozzle crystallization damage.

[0032] This embodiment, through prediction of nozzle temperature rise after engine shutdown, open-loop cooling injection based on pre-calibrated map, safety margin design for target temperature, maximum injection time limit, and clear operation status prompts, can proactively and effectively reduce the urea nozzle temperature after the engine is shut down at high temperature. This avoids high-temperature crystallization and blockage of the urea nozzle, as well as the resulting nozzle hardware damage, excessive emissions, and vehicle speed and torque limitation issues, thereby reducing maintenance and service costs and ensuring the normal operation of range extender vehicles.

[0033] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solution to high-temperature crystallization blockage of urea nozzles in range extender vehicles, characterized in that, Includes the following steps: When the preset function release conditions are met, obtain the exhaust temperature and exhaust flow rate at the moment the engine stops; Based on the exhaust temperature and exhaust flow rate at the time of engine shutdown, the expected temperature of the urea nozzle after engine shutdown is calculated from the pre-calibrated urea nozzle temperature rise Map1. The required temperature drop Δt is calculated based on the expected temperature and the preset target temperature. Based on the required temperature drop Δt, the corresponding urea injection quantity and injection frequency are interpolated from the pre-calibrated urea nozzle temperature drop Map2; Urea is continuously injected into the urea nozzle according to the interpolated urea injection volume and injection frequency. The urea solution carries away the heat accumulated in the urea nozzle, thereby reducing the urea nozzle temperature and preventing high-temperature crystallization and blockage of the urea nozzle.

2. The solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, When a fault is detected in the urea injection system, the process of troubleshooting and resolving the fault is initiated. The process ends after the fault is resolved, and the shutdown and cooling injection is not performed.

3. The solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, The pre-calibration steps for urea nozzle temperature rise Map1 are as follows: Using a urea temperature measuring nozzle, under different exhaust flow rates and different exhaust temperature combinations, test the highest temperature that the urea nozzle can reach after the engine stops, and pre-calibrate the highest temperature in urea nozzle temperature rise Map1 to establish the correspondence between exhaust temperature and exhaust flow rate at the time of shutdown and the expected highest temperature of urea nozzle after shutdown.

4. The solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, The pre-calibration steps for urea nozzle temperature drop Map2 are as follows: at different initial temperatures of urea nozzles, urea is injected with a preset injection volume and a preset frequency. The temperature drop of the urea nozzle after urea injection is tested, and the temperature drop data is pre-calibrated in urea nozzle temperature drop Map2 to establish the correspondence between nozzle temperature, cooling requirements and required urea injection volume and injection frequency.

5. The solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, The exhaust flow rate at the moment of shutdown is estimated by an exhaust flow rate estimation model, which is based on the engine's operating parameters before shutdown and uses a pre-established exhaust flow rate estimation model to calculate the exhaust flow rate at the moment of shutdown.

6. The solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, The preset target temperature is 115℃, which is lower than the crystallization risk threshold temperature of 120℃ for urea nozzles, in order to allow for error margin.

7. The solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, The urea injection cooling process is an open-loop control, which means that the injection quantity and injection frequency are directly calculated based on the interpolation of urea nozzle temperature rise Map1 and urea nozzle temperature drop Map2, without real-time monitoring and feedback correction of nozzle temperature.

8. The solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, When the expected temperature of the urea nozzle calculated based on the urea nozzle temperature rise Map1 does not exceed the preset target temperature, it is determined that there is no risk of crystallization. The injection system is then reversed, and the urea solution in the injection pipeline is drawn back to end the process.

9. The solution to the high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, The preset conditions for releasing the function include: engine speed less than 200 rpm; exhaust temperature before SCR aftertreatment greater than 200℃; urea pump pressure within 8500 hpa to 9500 hpa; and no faults in the urea injection system and related hardware.

10. The solution to high-temperature crystallization blockage of urea nozzles in range extender vehicles according to claim 1, characterized in that, It is only executed after the engine is shut down; urea injection is controlled by closed-loop logic when the engine is running normally.

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