Urea injection amount calculation method, dual scr system, engine, and electronic device

Abstract

This invention belongs to the technical field of diesel engine aftertreatment systems, and particularly relates to a method for calculating urea injection quantity, a dual-SCR system, an engine, and electronic equipment. The calculation method includes: calculating the conversion efficiency of the pre-stage SCR system based on the first urea injection quantity and the first nitrogen oxide content; obtaining an aging correction coefficient based on a first temperature; calculating the first nitrogen dioxide content after passing through DOC based on the pre-stage SCR conversion efficiency and the aging correction coefficient; calculating the second nitrogen dioxide content after passing through DPF based on the first nitrogen dioxide content; calculating the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content; and calculating the second urea injection quantity before the post-stage SCR system based on the ratio. According to the method for calculating the urea injection quantity before the post-stage SCR system of this invention, the second urea injection quantity can be precisely controlled, ensuring emission performance, avoiding ammonia leakage, reducing urea consumption, and improving economic efficiency.

Description

Technical Field

[0001] This invention belongs to the technical field of diesel engine aftertreatment systems, and particularly relates to a method for calculating urea injection quantity, a dual SCR system, an engine, and electronic equipment. Background Technology

[0002] In existing dual SCR (Selective Catalytic Reduction) systems, nitrogen oxide sensors are not installed before or after the DOC (diesel oxidation catalyst), and the reaction efficiency of the upstream SCR system is uncertain. This makes it impossible to accurately measure the nitrogen dioxide content after passing through the DOC, and consequently, it is impossible to accurately control the urea injection amount of the urea nozzle before the downstream SCR, resulting in ammonia leakage, increased urea consumption, and increased costs. Summary of the Invention

[0003] The objective of this invention is to at least solve the problem of how to precisely control the urea injection volume of the urea nozzle before the downstream SCR system. This objective is achieved through the following technical solution:

[0004] The first aspect of the present invention provides a method for calculating urea injection volume, comprising:

[0005] The first urea injection rate and the first nitrogen oxide content before the upstream SCR system, as well as the first temperature before DOC, are obtained.

[0006] The conversion efficiency of the pre-stage SCR system is calculated based on the first urea injection volume and the first nitrogen oxide content.

[0007] The current aging factor of DOC is obtained by querying the aging factor curve table based on the first temperature.

[0008] The aging factor is calculated by integration over a first preset time period to obtain the aging correction coefficient;

[0009] The first nitrogen dioxide content after DOC is calculated based on the conversion efficiency of the pre-stage SCR and the aging correction coefficient.

[0010] Calculate the second nitrogen dioxide content after passing through the DPF (Diesel Particulate Filter) based on the first nitrogen dioxide content;

[0011] The second nitrogen oxide content is obtained before the subsequent SCR system;

[0012] Calculate the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content based on the second nitrogen oxide content and the second nitrogen dioxide content;

[0013] The second urea injection volume before the subsequent SCR system is calculated based on the stated ratio.

[0014] According to the urea injection rate calculation method of the present invention, the first nitrogen dioxide content entering the DPF is accurately calculated by obtaining the conversion efficiency of the preceding SCR and the current aging correction factor of DOC. The second nitrogen dioxide content exiting the DPF can be accurately determined by calculating the difference between the amount of nitrogen dioxide captured by carbon in the DPF and the first nitrogen dioxide content. Furthermore, the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content can be accurately determined using the second nitrogen oxide content and the second nitrogen dioxide content. The second urea injection rate before the subsequent SCR system is controlled based on this ratio. Accurately knowing the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content provides accurate numerical input for ammonia storage calculation and urea injection in the subsequent SCR, thereby precisely controlling the second urea injection rate, ensuring emission performance, preventing ammonia leakage, reducing urea consumption, and improving economic efficiency.

[0015] In addition, the urea injection quantity calculation method according to the present invention may also have the following additional technical features:

[0016] In some embodiments of the present invention, the step of calculating the second nitrogen dioxide content includes:

[0017] The second temperature before the DPF is detected;

[0018] Based on the fact that the second temperature is greater than the passive regeneration temperature, calculate the content of the third nitrogen dioxide that reacts with carbon in the DPF;

[0019] The difference between the first nitrogen dioxide content and the third nitrogen dioxide content is calculated to obtain the second nitrogen dioxide content.

[0020] In some embodiments of the present invention, the step of calculating the second nitrogen dioxide content further includes:

[0021] The first nitrogen dioxide content is taken as the second nitrogen dioxide content based on the fact that the second temperature is less than the passive regeneration temperature.

[0022] In some embodiments of the present invention, the calculation method further includes correcting the first nitrogen oxide content and the second nitrogen oxide content, the correction step including:

[0023] Calculate the consistency deviation value between the first nitrogen oxide content and the second nitrogen oxide content based on the first nitrogen oxide content, the second nitrogen oxide content, and the first urea injection amount;

[0024] If the consistency deviation value is greater than the preset deviation value, the upstream SCR system is controlled to stop injecting urea and continue for a second preset time.

[0025] The content of the third nitrogen oxides before the front-stage SCR system and the content of the fourth nitrogen oxides before the rear-stage SCR system are obtained respectively within the second preset time period;

[0026] Based on the first nitrogen oxide content, the second nitrogen oxide content, the third nitrogen oxide content, the fourth nitrogen oxide content, and the first urea injection amount, calculate the first deviation correction coefficient for the first nitrogen oxide content and the second deviation correction coefficient for the second nitrogen oxide content;

[0027] The first nitrogen oxide content is corrected according to the first deviation correction factor, and the second nitrogen oxide content is corrected according to the second deviation correction factor.

[0028] In some embodiments of the present invention, the method for calculating the first nitrogen dioxide content is as follows:

[0029] The nitrogen dioxide content in the primary exhaust and the nitric oxide content before DOC are calculated based on the content of the first nitrogen oxide compound and the conversion efficiency of the preceding SCR.

[0030] Find the oxidation efficiency of DOC by referring to the table;

[0031] The content of nitrogen dioxide is calculated using the following formula:

[0032] The first nitrogen dioxide content = [(1 - the conversion efficiency of the pre-stage SCR) × the original nitrogen dioxide content + the oxidation efficiency × the aging correction coefficient × the nitric oxide content] × the first deviation correction coefficient.

[0033] In some embodiments of the present invention, the formula for calculating the conversion efficiency of the pre-stage SCR is as follows:

[0034]

[0035] In some embodiments of the present invention, the method for calculating the second nitrogen dioxide content is as follows:

[0036] The carbon load of the current model is calculated based on the first nitrogen dioxide content (carbon load refers to the carbon particles accumulated by the vehicle's exhaust through the DPF during operation).

[0037] The temperature coefficient is obtained based on the second temperature;

[0038] Airspeed coefficient before obtaining DPF;

[0039] The second nitrogen dioxide content is calculated according to the following formula;

[0040] The second nitrogen dioxide content = the first nitrogen dioxide content × the temperature coefficient × the space velocity coefficient × the current carbon loading coefficient.

[0041] The second aspect of the present invention provides a dual SCR system for implementing the above-described urea injection quantity calculation method, wherein a first nitrogen oxide sensor, a first urea injector, a first temperature measuring device, a pre-stage SCR system, a DOC, a second temperature measuring device, a DPF, a second nitrogen oxide sensor, a second urea injector, and a post-stage SCR system are arranged sequentially along the direction of exhaust gas emission.

[0042] The first nitrogen oxide sensor is used to detect the content of a first nitrogen oxide compound and the content of a third nitrogen oxide compound;

[0043] The first temperature measuring device is used to detect the first temperature;

[0044] The second temperature measuring device is used to detect the second temperature;

[0045] The second nitrogen oxide sensor is used to detect the content of the second nitrogen oxide compound and the fourth nitrogen oxide compound.

[0046] A third aspect of the invention provides an engine comprising the dual SCR system as described above.

[0047] A fourth aspect of the present invention provides an electronic device comprising a processor and a memory;

[0048] The memory is used to store computer programs and to transfer the computer programs to the processor;

[0049] The processor is used to execute the above-described urea injection quantity calculation method according to the instructions in the computer program.

[0050] According to the dual SCR system of this application, the above-mentioned urea injection quantity calculation method can be implemented. The dual SCR system can provide accurate numerical input for the ammonia storage calculation and urea injection in the subsequent SCR, thereby accurately controlling the second urea injection quantity, ensuring emission effect, avoiding ammonia leakage, reducing urea consumption, and improving economic efficiency. Attached Figure Description

[0051] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0052] Figure 1This is a flowchart illustrating a method for calculating urea injection volume according to an embodiment of the present invention.

[0053] Figure 2 This is a schematic diagram illustrating the specific process for calculating the second nitrogen dioxide content according to an embodiment of the present invention;

[0054] Figure 3 This is a schematic diagram of the process for correcting the content of the first nitrogen oxide compound and the content of the second nitrogen oxide compound according to an embodiment of the present invention;

[0055] Figure 4 A schematic diagram of a dual SCR system according to an embodiment of the present invention is shown.

[0056] Figure 5 A graph showing the first temperature change data measured by the first temperature measuring device;

[0057] Figure 6 A graph showing the second temperature change data measured by the second temperature measuring device;

[0058] Figure 7 A graph showing the third temperature change data measured by the third temperature measuring device;

[0059] Figure 8 Table of DOC aging factor curves corresponding to the first temperature;

[0060] Figure 9 This is a graph showing the relationship between the conversion efficiency of the pre-stage SCR and the conversion efficiency of DOC.

[0061] The attached figures are labeled as follows:

[0062] 100. Dual SCR system;

[0063] 10. Piping; 20. Pre-stage SCR system; 30. DOC; 40. DPF; 50. Post-stage SCR system;

[0064] 60. First nitrogen-oxygen sensor; 61. Second nitrogen-oxygen sensor; 62. Third nitrogen-oxygen sensor;

[0065] 70. First urea injector; 71. Second urea injector;

[0066] 80. First temperature measuring device; 81. Second temperature measuring device; 82. Third temperature measuring device;

[0067] 90. Pressure measuring device;

[0068] 200. Electronic equipment. Detailed Implementation

[0069] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0070] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0071] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0072] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure is flipped, an element described as "below other elements or features" or "below other elements or features" would subsequently be oriented as "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0073] like Figure 1 As shown, according to an embodiment of the present invention, a method for calculating urea injection volume is proposed, comprising:

[0074] S10: Obtain the first urea injection quantity and the first nitrogen oxide content before the upstream SCR system 20, and the first temperature before DOC30.

[0075] S20: Calculate the pre-stage SCR conversion efficiency of the pre-stage SCR system 20 based on the first urea injection rate and the first nitrogen oxide content.

[0076] S30: Based on the first temperature, query the aging factor curve table to obtain the current aging factor of DOC30.

[0077] S40: Integrate and calculate the aging factor within the first preset time period to obtain the aging correction coefficient.

[0078] S50: Calculate the first nitrogen dioxide content after DOC30 based on the conversion efficiency of the preceding SCR and the aging correction factor.

[0079] S60: Calculate the second nitrogen dioxide content after DPF40 based on the first nitrogen dioxide content.

[0080] S70: The second nitrogen oxide content obtained 50 before the subsequent SCR system.

[0081] S80: Calculate the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content based on the second nitrogen oxide content and the second nitrogen dioxide content.

[0082] S90: Calculate the second urea injection amount before the SCR system 50 according to the ratio.

[0083] Understandably, the amount of second urea injected before the SCR system 50 is calculated by using the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content. Specifically, based on the chemical formulas 4NO + 4NH3 + O2 → 4N2 + 6H2O and 2NO2 + 4NH3 + O2 → 3N2 + 6H2O, we know that 4 moles of nitric oxide correspond to 4 moles of ammonia, and 2 moles of nitrogen dioxide correspond to 4 moles of ammonia. Now that the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content is known, the required amount of ammonia can be calculated, thus determining the required amount of second urea injected before the SCR system 50.

[0084] Combination Figure 5 As shown, it can be seen that the first temperature change is drastic, such as... Figure 6 As shown, the second temperature change is relatively gradual, such as Figure 7 As shown, the third temperature change is also relatively gradual, so it can be concluded that the change in the pre-stage SCR conversion efficiency of the pre-stage SCR system 20 is relatively large, which has a significant impact on the first nitrogen dioxide content and the DOC30 aging correction factor after calculating DOC30. Therefore, it is necessary to consider not only the impact of the current temperature on the DOC30 aging factor, but also the pre-stage SCR conversion efficiency of the pre-stage SCR system 20.

[0085] Specifically, in combination Figure 9 As shown, it can be seen that the conversion efficiency of the pre-stage SCR system 20 has a significant impact on the conversion efficiency of DOC30.

[0086] According to the urea injection rate calculation method of this embodiment, the first nitrogen dioxide content entering the DPF40 is accurately calculated by obtaining the pre-stage SCR conversion efficiency of the pre-stage SCR system 20 and the current aging correction coefficient of DOC30. The second nitrogen dioxide content exiting the DPF40 can be accurately determined by calculating the difference between the amount of nitrogen dioxide captured by carbon in the DPF40 and the first nitrogen dioxide content. Furthermore, the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content can be accurately determined using the second nitrogen oxide content and the second nitrogen dioxide content. The second urea injection rate before the downstream SCR system 50 is then controlled based on this ratio. This provides accurate numerical input for ammonia storage calculation and urea injection in the downstream SCR system 50, thereby precisely controlling the second urea injection rate, ensuring emission performance, preventing ammonia leakage, reducing urea consumption, and improving economic efficiency.

[0087] Combination Figure 8As shown, the risk of aging increases rapidly when the temperature of DOC30 exceeds 400℃. At this time, regeneration-related work is generally carried out. DOC30 oxidizes fuel and provides heat. The high catalyst activity will react with heavy metal ions such as sulfur in the fuel and occupy active sites, causing DOC30 to age. Therefore, the aging factor was calculated at different temperatures through experiments, and the corresponding aging factor curve table was obtained.

[0088] Specifically, the experiment calculating the aging factor at different temperatures uses the Arrenius model. In a given environment, when temperature becomes the absolute primary factor affecting product aging and lifespan, the Arrenius model, derived by solely considering the thermal acceleration factor effect, is used to describe the test expression as follows:

[0089] AF=exp{(Ea / K)·[(1 / Tu)-(1 / Tt)]}

[0090] In the formula:

[0091] AF is an aging factor;

[0092] Ea is the energy consumed in fault precipitation, also known as activation energy. The activation energy varies depending on the DOC30. Generally, the activation energy of a DOC ranges from 0.3 eV to 1.2 eV.

[0093] K is the Boltzmann constant, with a value of 8.617385 × 10^-5;

[0094] Tu represents the temperature under non-accelerated conditions. This temperature value is an absolute temperature, expressed in Kelvin (K).

[0095] Tt is the temperature value under accelerated conditions as tested. This temperature value is an absolute temperature value, expressed in Kelvin (K).

[0096] Combination Figure 2 As shown, it can be understood that the steps for calculating the second nitrogen dioxide content include:

[0097] The second temperature before DPF40 is measured;

[0098] Calculate the content of the third nitrogen dioxide that reacts with carbon in DPF40 based on the fact that the second temperature is greater than the passive regeneration temperature.

[0099] The difference between the first and third nitrogen dioxide contents is calculated to obtain the second nitrogen dioxide content.

[0100] Understandably, the steps for calculating the second nitrogen dioxide content also include:

[0101] Based on the fact that the second temperature is lower than the passive regeneration temperature, the first nitrogen dioxide content is taken as the second nitrogen dioxide content.

[0102] Specifically, the formula for carbon capture of nitrogen dioxide in the DPF40 is: C + 2NO2 = CO2 + 2NO. The passive regeneration temperature is 250-450℃. Therefore, the passive regeneration temperature in this embodiment is 250℃. When the second temperature is greater than 250℃, passive regeneration begins in the DPF40, where carbon captures nitrogen dioxide and adsorbs particulate matter in the exhaust gas, such as particulates, hydrocarbons, nitrogen oxides, and sulfur, preventing them from being released into the atmosphere and causing environmental pollution. Using the DPF40 can reduce soot emissions from diesel engines by more than 90%.

[0103] Combination Figure 3 As shown, it is understandable that the calculation method also includes correcting the first and second nitrogen oxide contents, and the correction steps include:

[0104] Calculate the consistency deviation value between the first nitrogen oxide content, the second nitrogen oxide content, and the first urea injection amount;

[0105] If the consistency deviation value is greater than the preset deviation value, the upstream SCR system 20 is controlled to stop injecting urea and continue for a second preset time.

[0106] The third nitrogen oxide content before the first stage SCR system 20 and the fourth nitrogen oxide content before the second stage SCR system 50 are obtained respectively within the second preset time period;

[0107] Based on the first nitrogen oxide content, the second nitrogen oxide content, the third nitrogen oxide content, the fourth nitrogen oxide content, and the first urea injection amount, calculate the first deviation correction coefficient for the first nitrogen oxide content and the second deviation correction coefficient for the second nitrogen oxide content;

[0108] The content of the first nitrogen oxide compound is corrected according to the first deviation correction factor, and the content of the second nitrogen oxide compound is corrected according to the second deviation correction factor.

[0109] In the prior art, there is a consistency deviation between the first nitrogen oxide sensor 60 and the second nitrogen oxide sensor 61, which affects the accuracy of measuring nitrogen oxide content. Therefore, in related technologies, to improve the reliability of the first nitrogen oxide sensor 60 and the second nitrogen oxide sensor 61, it is necessary to correct the consistency deviation of the first nitrogen oxide sensor 60 and the second nitrogen oxide sensor 61 during engine calibration before the engine leaves the factory. However, the above method cannot correct the consistency deviation of the first nitrogen oxide sensor 60 and the second nitrogen oxide sensor 61 that occurs during use due to factors such as durability degradation, resulting in poor accuracy in measuring nitrogen oxide content, thereby reducing the reliability of the first nitrogen oxide sensor 60 and the second nitrogen oxide sensor 61.

[0110] Specifically, to solve this problem, in this embodiment, after the exhaust temperature of the pre-stage SCR system 20 meets the preset temperature range, if the engine speed deviation, engine torque deviation, and ammonia-to-nitrogen ratio of the pre-stage SCR system 20 meet the preset stable operating conditions within the first time period, the nitrogen oxide measurement values ​​of the first nitrogen oxide sensor 60 and the second nitrogen oxide sensor 61 of the pre-stage SCR system 20 within the first time period are integrated to obtain the first nitrogen oxide content measured by the first nitrogen oxide sensor 60 and the second nitrogen oxide content measured by the second nitrogen oxide sensor 61.

[0111] The consistency deviation between the first nitrogen oxide sensor 60 and the second nitrogen oxide sensor 61 is calculated using the first nitrogen oxide content, the second nitrogen oxide content, and the first urea injection amount of the pre-stage SCR system 20.

[0112] When the consistency deviation value exceeds the preset deviation value, the upstream SCR system 20 is controlled to stop injecting urea and continue for a second time period. The nitrogen oxide measurement values ​​of the first nitrogen oxide sensor 60 and the second nitrogen oxide sensor 61 during the second time period are integrated to obtain the third nitrogen oxide content measured by the first nitrogen oxide sensor 60 and the fourth nitrogen oxide content measured by the second nitrogen oxide sensor 61.

[0113] The first deviation correction coefficient of the first nitrogen oxide sensor 60 and the second deviation correction coefficient of the second nitrogen oxide sensor 61 are calculated based on the first nitrogen oxide content, the second nitrogen oxide content, the third nitrogen oxide content, the fourth nitrogen oxide content, and the first urea injection amount.

[0114] The first nitrogen oxide sensor 60 is corrected using a first deviation correction coefficient, and the second nitrogen oxide sensor 61 is corrected using a second deviation correction coefficient. During the use of the first and second nitrogen oxide sensors 60 and 61, this method can detect in real time whether there is a consistency deviation between them, and automatically calculate correction coefficients to automatically correct the first and second nitrogen oxide sensors 60 and 61, thereby improving the accuracy of nitrogen oxide content measurement and thus enhancing the reliability of the first and second nitrogen oxide sensors 60 and 61.

[0115] It is understandable that the calculation method for the first nitrogen dioxide content is as follows:

[0116] Calculate the nitrogen dioxide content in the primary exhaust and the nitric oxide content before DOC30 based on the first nitrogen oxide content and the conversion efficiency of the preceding SCR.

[0117] Find the oxidation efficiency of DOC30 from the table;

[0118] The content of nitrogen dioxide is calculated using the following formula:

[0119] First nitrogen dioxide content = [(1 - pre-stage SCR conversion efficiency) × original exhaust nitrogen dioxide content + oxidation efficiency × aging correction coefficient × nitric oxide content] × first deviation correction coefficient.

[0120] Specifically, the first deviation correction coefficient can correct the first nitrogen oxide content, further improving the accuracy of the first nitrogen dioxide content.

[0121] Understandably, the formula for calculating the conversion efficiency of the pre-stage SCR is:

[0122]

[0123] Understandably, the calculation method for the second nitrogen dioxide content is as follows:

[0124] Calculate the carbon loading of the current model based on the nitrogen dioxide content;

[0125] The temperature coefficient is obtained based on the second temperature.

[0126] Airspeed coefficient before obtaining DPF40;

[0127] Calculate the second nitrogen dioxide content using the following formula;

[0128] Second nitrogen dioxide content = First nitrogen dioxide content × Temperature coefficient × Space velocity coefficient × Current carbon loading coefficient.

[0129] Combination Figure 4 As shown, the present invention also proposes a dual SCR system 100, which is used to implement the above-mentioned urea injection quantity calculation method. The dual SCR system 100 is provided with a first nitrogen-oxygen sensor 60, a first urea injector 70, a first temperature measuring device 80, a pre-stage SCR system 20, a DOC 30, a second temperature measuring device 81, a DPF 40, a second nitrogen-oxygen sensor 61, a second urea injector 71, and a post-stage SCR system 50 in sequence along the direction of exhaust gas emission.

[0130] The first nitrogen oxide sensor 60 is used to detect the content of a first nitrogen oxide compound and the content of a third nitrogen oxide compound;

[0131] The first temperature measuring device 80 is used to detect the first temperature;

[0132] The second temperature measuring device 81 is used to detect the second temperature;

[0133] The second nitrogen oxide sensor 61 is used to detect the content of the second nitrogen oxide compound and the content of the fourth nitrogen oxide compound.

[0134] Understandably, the dual SCR system 100 also includes a third temperature measuring device 82, a third nitrogen oxide sensor 62, and a pressure measuring device 90. The third temperature measuring device 82 is located between the downstream SCR system 50 and the DPF 40, and is used to measure the third temperature before the downstream SCR system 50. The third nitrogen oxide sensor 62 is located after the downstream SCR system 50, and is used to measure whether the exhaust gas emissions meet the standards. The pressure measuring device 90 is connected to the DPF 40, and is used to measure the pressure within the DPF 40.

[0135] In a specific embodiment, the dual SCR system 100, arranged sequentially along the direction of exhaust gas emission, includes a first nitrogen oxide sensor 60, a first urea injector 70, a first temperature measuring device 80, a pre-stage SCR system 20, a DOC 30, a second temperature measuring device 81, a DPF 40, a second nitrogen oxide sensor 61, a third temperature measuring device 82, a second urea injector 71, a post-stage SCR system 50, and a third nitrogen oxide sensor 62. All of the above devices are connected via pipeline 10. A pressure measuring device 90 is connected to the DPF 40.

[0136] The present invention also proposes an engine comprising the aforementioned dual SCR system 100.

[0137] The present invention also proposes an electronic device 200, which includes a processor and a memory;

[0138] The memory is used to store computer programs and transfer them to the processor;

[0139] The processor is used to execute the above-mentioned urea injection quantity calculation method according to the instructions in the computer program.

[0140] The present invention also proposes a computer-readable storage medium for storing a computer program for implementing the above-described method for calculating urea injection volume.

[0141] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for calculating urea injection volume, characterized in that, Applied to a dual SCR system, the dual SCR system is provided with a first nitrogen oxide sensor, a first urea injector, a first temperature measuring device, a pre-stage SCR system, a DOC, a second temperature measuring device, a DPF, a second nitrogen oxide sensor, a second urea injector, and a post-stage SCR system arranged sequentially along the direction of exhaust gas emission. The first nitrogen oxide sensor is used to detect the content of a first nitrogen oxide compound and the content of a third nitrogen oxide compound; The first temperature measuring device is used to detect the first temperature; The second temperature measuring device is used to detect the second temperature; The second nitrogen oxide sensor is used to detect the content of a second nitrogen oxide compound and a fourth nitrogen oxide compound. The method for calculating the urea injection volume includes: The first urea injection rate and the first nitrogen oxide content before the pre-stage SCR system and the first temperature before DOC are obtained; The conversion efficiency of the pre-stage SCR system is calculated based on the first urea injection volume and the first nitrogen oxide content. The current aging factor of DOC is obtained by querying the aging factor curve table based on the first temperature. The aging factor is calculated by integration over a first preset time period to obtain the aging correction coefficient; The first nitrogen dioxide content after DOC is calculated based on the conversion efficiency of the pre-stage SCR and the aging correction coefficient. Calculate the second nitrogen dioxide content after DPF treatment based on the first nitrogen dioxide content; The content of the second nitrogen oxides before the subsequent SCR system is obtained; Calculate the ratio of nitric oxide to nitrogen dioxide in the second nitrogen oxide content based on the second nitrogen oxide content and the second nitrogen dioxide content; The second urea injection volume before the subsequent SCR system is calculated based on the stated ratio.

2. The method for calculating urea injection volume according to claim 1, characterized in that, The steps for calculating the second nitrogen dioxide content include: The second temperature before the DPF is detected; Based on the fact that the second temperature is greater than the passive regeneration temperature, calculate the content of the third nitrogen dioxide that reacts with carbon in the DPF; The difference between the first nitrogen dioxide content and the third nitrogen dioxide content is calculated to obtain the second nitrogen dioxide content.

3. The method for calculating urea injection volume according to claim 2, characterized in that, The steps for calculating the second nitrogen dioxide content also include: The first nitrogen dioxide content is taken as the second nitrogen dioxide content based on the fact that the second temperature is less than the passive regeneration temperature.

4. The method for calculating urea injection volume according to any one of claims 1 to 3, characterized in that, It also includes correcting the content of the first nitrogen oxide and the content of the second nitrogen oxide, the correction step including: Calculate the consistency deviation value between the first nitrogen oxide content and the second nitrogen oxide content based on the first nitrogen oxide content, the second nitrogen oxide content, and the first urea injection amount; If the consistency deviation value is greater than the preset deviation value, the upstream SCR system is controlled to stop injecting urea and continue for a second preset time. The contents of the third nitrogen oxides before the front-stage SCR system and the contents of the fourth nitrogen oxides before the rear-stage SCR system are obtained respectively within the second preset time period; Based on the first nitrogen oxide content, the second nitrogen oxide content, the third nitrogen oxide content, the fourth nitrogen oxide content, and the first urea injection amount, calculate the first deviation correction coefficient for the first nitrogen oxide content and the second deviation correction coefficient for the second nitrogen oxide content; The first nitrogen oxide content is corrected according to the first deviation correction factor, and the second nitrogen oxide content is corrected according to the second deviation correction factor.

5. The method for calculating urea injection volume according to claim 4, characterized in that, The calculation method for the first nitrogen dioxide content is as follows: Calculate the nitrogen dioxide content in the primary exhaust and the nitric oxide content before DOC based on the first nitrogen oxide content and the conversion efficiency of the pre-stage SCR. Find the oxidation efficiency of DOC by referring to the table; The content of the first nitrogen dioxide is calculated according to the following formula: The first nitrogen dioxide content = [(1 - the conversion efficiency of the pre-stage SCR) × the original nitrogen dioxide content + the oxidation efficiency × the aging correction coefficient × the nitric oxide content] × the first deviation correction coefficient.

6. The method for calculating urea injection volume according to claim 1, characterized in that, The formula for calculating the conversion efficiency of the pre-stage SCR is as follows: 。 7. The method for calculating urea injection volume according to claim 2, characterized in that, The second method for calculating the nitrogen dioxide content is as follows: Calculate the carbon loading of the current model based on the first nitrogen dioxide content; The temperature coefficient is obtained based on the second temperature; Airspeed coefficient before obtaining DPF; The second nitrogen dioxide content is calculated according to the following formula; The second nitrogen dioxide content = the first nitrogen dioxide content × the temperature coefficient × the space velocity coefficient × the current carbon loading coefficient.

8. A dual SCR system, characterized in that, For implementing the urea injection quantity calculation method as described in any one of claims 1-7, a first nitrogen-oxygen sensor, a first urea injector, a first temperature measuring device, a pre-stage SCR system, a DOC, a second temperature measuring device, a DPF, a second nitrogen-oxygen sensor, a second urea injector, and a post-stage SCR system are sequentially arranged along the direction of exhaust gas emission. The first nitrogen oxide sensor is used to detect the content of a first nitrogen oxide compound and the content of a third nitrogen oxide compound; The first temperature measuring device is used to detect the first temperature; The second temperature measuring device is used to detect the second temperature; The second nitrogen oxide sensor is used to detect the content of the second nitrogen oxide compound and the content of the fourth nitrogen oxide compound.

9. An engine comprising a dual SCR system, characterized in that, The dual SCR system is the dual SCR system as described in claim 8.

10. An electronic device, characterized in that, The electronic device includes a processor and a memory; The memory is used to store computer programs and to transfer the computer programs to the processor; The processor is configured to execute the urea injection quantity calculation method according to any one of claims 1-7 according to instructions in the computer program.

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