A modified scr efficiency model and a method for modifying, vehicle

Abstract

The application belongs to the technical field of tail gas aftertreatment, and particularly relates to a modified SCR efficiency model and a modification method and a vehicle. The modification method comprises: calculating the actual efficiency of the SCR model and the conversion efficiency of different measuring points of the cross section; classifying the measuring points according to the deviation of the conversion efficiency and the actual efficiency of each point to obtain a plurality of branch models, and sequentially calculating the area proportion and the efficiency correction coefficient of each branch model; correcting the efficiency coefficient of each branch model based on the temperature and the air speed to form an efficiency correction coefficient map; calculating the flow of NOx and ammonia flowing into each branch model and the conversion efficiency based on the area proportion and the efficiency correction coefficient, and calculating the efficiency of the modified SCR efficiency model based on the conversion efficiency of each branch model. The SCR model can be modified by the above method, so that the ammonia storage of the model is uniform and consistent with the actual ammonia storage, thereby improving the model precision and the model calibration efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tail gas aftertreatment, and particularly relates to a modified SCR efficiency model and a modification method and a vehicle. BACKGROUND

[0002] The urea selective catalytic reduction (SCR) technology has the advantages of high NOx conversion efficiency, strong sulfur resistance and low fuel consumption, and is one of the effective technical measures for China's medium and heavy-duty diesel vehicles to meet the national IV and above emission regulations. At present, the urea SCR technology has been widely used in medium and heavy-duty diesel vehicles. However, with the continuous upgrading of national emission regulations, the state has more stringent regulatory requirements for the conversion efficiency of the SCR system. When the current SCR efficiency model calibration is carried out, it is generally believed that the input is uniform, that is, the NH3 entering the SCR after mixing is uniform, but in actual use, the NH3 entering the SCR is often not uniform, which leads to uneven ammonia storage in the SCR carrier, and thus:

[0003] 1. In the actual process, the downstream NOx appears a step during the recovery process after urea injection is stopped, and the model does not have it;

[0004] 2. In the actual process, the NOx recovery corner after urea injection is stopped is not synchronized with the model NOx recovery corner.

[0005] The above two points will cause a large deviation between the calculated value and the actual value of the SCR efficiency model, and thus bring difficulties to the calibration work. SUMMARY

[0006] The purpose of the present application is to provide a modified SCR efficiency model and a modification method and a vehicle to solve the problem that the SCR model result is not synchronized with the actual situation due to uneven ammonia storage in the SCR carrier in the prior art.

[0007] The first aspect of the present application provides a modification method of an SCR efficiency model, comprising the following steps:

[0008] Calculate the actual efficiency of the SCR model and the conversion efficiency of different measuring points in the cross section;

[0009] Classify the measuring points according to the deviation of the conversion efficiency and the actual efficiency of each point to obtain a plurality of branch models, and calculate the area ratio and the efficiency correction coefficient of each branch model in turn;

[0010] Correct the efficiency coefficient of each branch model based on the temperature and the space velocity to form an efficiency correction coefficient map;

[0011] The flow of NOx and ammonia and conversion efficiency of each branch model are calculated based on the area ratio and the efficiency correction coefficient, and the corrected SCR efficiency model efficiency is calculated based on the conversion efficiency of each branch model.

[0012] The method for correcting the SCR efficiency model provided by the application can further have the following additional technical features:

[0013] In one embodiment of the application, the actual efficiency of the SCR model and the conversion efficiency of different measuring points in the cross section are calculated by:

[0014] A plurality of test points are uniformly arranged in the longitudinal cross section of the SCR treatment unit, urea injection is performed at a set ammonia nitrogen ratio less than 1, and the actual efficiency of the SCR model and the conversion efficiency of different measuring points are obtained.

[0015] In one embodiment of the application, the measuring points are classified according to the deviation of the conversion efficiency and the actual efficiency of each point to obtain a plurality of branch models, and the area ratio and the efficiency correction coefficient of each branch model are calculated in turn by:

[0016] A plurality of numerical ranges are divided based on the preset gradient and the actual efficiency, the measuring points falling into the same numerical range are classified into the same category, the ratio of the average efficiency of the measuring points in the same category to the actual efficiency is the efficiency correction coefficient of the branch model, and the ratio of the number of the measuring points in the same category to the total number of the measuring points is the area ratio of the branch model.

[0017] In one embodiment of the application, the number of the branch models is at least 3.

[0018] In one embodiment of the application, the efficiency coefficient of each branch model is corrected based on the temperature and the space velocity to form the efficiency correction coefficient map by:

[0019] Urea injection is repeatedly performed at different temperatures and space velocities to obtain the efficiency correction coefficient at different temperatures and space velocities, and a plurality of efficiency correction coefficients are combined to obtain the efficiency correction coefficient map.

[0020] In one embodiment of the application, the flow of NOx and ammonia flowing into each branch model is calculated based on the area ratio and the efficiency correction coefficient by:

[0021] The flow of NOx input into each branch model is proportional to the area ratio of the branch model;

[0022] The flow of ammonia input into each branch model is proportional to the area ratio and the efficiency correction coefficient of the branch model, and the efficiency correction coefficient is obtained based on the efficiency correction coefficient map.

[0023] The second aspect of the application provides a corrected SCR efficiency model applied to an SCR injection system, comprising:

[0024] a data collection unit configured to collect temperature, space velocity, NOx flow and ammonia flow data;

[0025] a data processing unit configured to find an efficiency correction coefficient map based on the temperature and space velocity data to obtain a corresponding efficiency correction coefficient, and calculate the NOx flow and ammonia flow data of each branch model based on the efficiency correction coefficient;

[0026] a branch model configured to calculate the conversion efficiency of each branch model based on the NOx flow and ammonia flow data of the branch model;

[0027] a summary unit configured to calculate the total conversion efficiency based on the conversion efficiency of each branch model.

[0028] In one specific embodiment of the present application, a correction module is further included, and the correction module comprises:

[0029] a conversion efficiency confirmation module configured to obtain the actual conversion efficiency of the close-coupled SCR and the conversion efficiency of different measuring points;

[0030] a data analysis module configured to classify the measuring points according to the deviation of the conversion efficiency of each point from the actual efficiency to obtain a plurality of branch models, and sequentially calculate the area proportion and efficiency correction coefficient of each branch model; and further configured to correct the efficiency coefficient of each branch model based on the temperature and space velocity to form an efficiency correction coefficient map.

[0031] In one specific embodiment of the present application, the data analysis module comprises:

[0032] a data classification module configured to divide a plurality of numerical ranges by taking the actual efficiency as a benchmark using a preset gradient, and classify the measuring points falling into the same numerical range into a category to form a branch model;

[0033] a data calculation module configured to calculate the efficiency average of the measuring points in the same category, and calculate the ratio of the efficiency average to the actual efficiency as the efficiency correction coefficient of the branch model; and further configured to calculate the number of the measuring points in the same category, and calculate the ratio of the number of the measuring points in the same category to the total number of the measuring points as the area proportion of the branch model.

[0034] The third aspect of the present application further provides a vehicle comprising the corrected SCR efficiency model as described above.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] The correction method of the corrected SCR efficiency model provided by the application is based on the non-uniformity of the actual ammonia storage in the SCR carrier, the deviation of the actual ammonia nitrogen ratio from the set ammonia nitrogen ratio is measured, the SCE end face is divided into several parts, the ammonia correction coefficient of each part is calculated respectively, the influence of temperature and air speed on uniformity is introduced, and the efficiency correction coefficient map is formed, so that the model ammonia storage is consistent with the actual ammonia storage uniformity, thereby improving the model precision and the model calibration efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0038] Figure 1 The flow chart of the correction method of the corrected SCR efficiency model provided by the application;

[0039] Figure 2 The SCR carrier cross section and the measurement point distribution map provided by the application;

[0040] Figure 3 The module diagram of the corrected SCR efficiency model in the application. DETAILED DESCRIPTION

[0041] Exemplary embodiments of the application will be described herein below with reference to the accompanying drawings. Although the exemplary embodiments of the application are shown in the drawings, it should be understood that the application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided so that the application can be more thoroughly understood and the scope of the application can be fully conveyed to those skilled in the art.

[0042] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises", "comprising", "includes", "including" and "has" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be interpreted as necessarily requiring their performance in the specific order described or illustrated, unless explicitly stated otherwise. It should also be understood that additional or alternative steps can be employed.

[0043] Although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first", "second", and other numerical terms when used herein do not connote an order or sequence unless specifically stated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

[0044] For ease of description, spatial relative terms can be used herein to describe the relationship of one element or feature to another element or feature as shown in the figures, such as "inner", "outer", "inward", "outward", "lower", "below", "upper", "above", etc. Such spatial relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0045] As shown in FIG. 1, a modified method for modifying an SCR efficiency model according to an embodiment of the present application includes the following steps: Figures 1-2 First, the actual efficiency of the SCR model and the conversion efficiency of different measuring points in the cross section are calculated.

[0046] First, the actual efficiency of the SCR model and the conversion efficiency of different measuring points in the cross section are calculated.

[0047] Specifically, the method further includes the following steps before the above steps: a plurality of measuring points are uniformly arranged in the longitudinal cross section of the SCR carrier, urea injection is performed at a set ammonia nitrogen ratio less than 1, and the actual efficiency of the SCR model and the conversion efficiency of different measuring points are obtained.

[0048] The conversion efficiency can be measured by NOx sensors arranged upstream and downstream of the SCR carrier. Specifically, the NOx sensors arranged upstream and downstream of the SCR carrier respectively measure the NOx concentrations upstream and downstream thereof, and the actual efficiency is determined based on the upstream and downstream NOx concentrations. The conversion efficiency of different measuring points in the cross section of the SCR carrier is measured in the same way.

[0049] Secondly, the measurement points are classified according to the deviation between the conversion efficiency of each point and the actual efficiency to obtain multiple branch models, and the area proportion and efficiency correction coefficient of each branch model are calculated in turn.

[0050] Specifically, the above steps include:

[0051] A preset gradient is used to divide the actual efficiency into multiple numerical ranges. The measuring points whose actual efficiency falls into the same numerical range are classified into the same category. The ratio of the efficiency mean of the same category of measuring points to the actual efficiency is the efficiency correction coefficient of the branch model. The ratio of the number of the same category of measuring points to the total number of measuring points is the area ratio of the branch model.

[0052] Preferably, the number of the branch models is at least 3. The number of branch models is positively correlated with the correction accuracy, and the more branch models there are, the higher the accuracy.

[0053] Thirdly, the efficiency coefficient of each branch model is corrected based on temperature and airspeed to form an efficiency correction coefficient map.

[0054] Specifically, this step includes at least:

[0055] Repeated urea injection at different temperatures and airspeed ratios yields efficiency correction coefficients at different temperatures and airspeeds. Multiple efficiency correction coefficients are combined to form an efficiency correction coefficient map. The efficiency correction coefficient map in this application is derived from multiple tests.

[0056] Finally, the flow rates of NOx and ammonia flowing into each branch model and the conversion efficiency are calculated based on the area ratio and the efficiency correction coefficient, and the efficiency of the corrected SCR efficiency model is calculated based on the conversion efficiency of each branch model.

[0057] Specifically, the flow rates of NOx and ammonia flowing into each branch model are calculated based on the area ratio and efficiency correction coefficient:

[0058] The flow rate of NOx input to each branch model is proportional to the area ratio of the branch model;

[0059] The ammonia flow rate input to each branch model is proportional to the area ratio and efficiency correction coefficient of the branch model. The efficiency correction coefficient is obtained based on the efficiency correction coefficient map.

[0060] In one embodiment, the urea injection is performed by setting the ammonia nitrogen ratio to be less than 1 (e.g., 0.7 ammonia nitrogen ratio), and then the actual efficiency of the SCR is calculated to be x, and then the urea injection is performed according to the ammonia nitrogen ratio. Figure 2 The measurement points arranged in the (the total number of measurement points is m) are used to measure the conversion efficiency x of each point i .

[0061] Taking the 3-branch model as an example, compare x iIf (x-2%)≤xi≤(x+2%), the corresponding measuring point is divided into a class to form a branch model, wherein the ammonia correction coefficient a of the branch model is 1, the total number of measuring points meeting the condition is denoted as m1, and the area S1 of the same class of measuring points is (m1 / m)*S (S is the area of the SCR end surface); if xi>(x+2%), the corresponding measuring point is divided into a class to form a branch model, the total number of measuring points meeting the condition is denoted as m2, the average efficiency xm2 of this part is calculated, and then the ammonia correction coefficient a of the branch model is xm2 / x, and the area S2 of the same class of measuring points is (m2 / m)*S; if xi<(x-2%), the corresponding measuring point is divided into a class to form a branch model, the total number of measuring points meeting the condition is denoted as m3, the average efficiency xm3 of this part is calculated, and then the ammonia correction coefficient a of the branch model is xm3 / x, and the area S3 of the same class of measuring points is (m3 / m)*S.

[0062] The urea injection is repeatedly performed at different temperatures and space velocities, and then the ammonia correction coefficients of the three branch models at different temperatures and space velocities are calculated, and the efficiency correction coefficient map is formed.

[0063] Subsequently, the NOx mass flow, the SCR carrier inlet temperature, the ammonia mass flow at the SCR carrier inlet, and the space velocity of the SCR carrier are input into the corrected SCR model, the SCR model looks up the efficiency correction coefficient map based on the input SCR carrier inlet temperature and the space velocity of the SCR carrier to obtain the efficiency correction coefficients of the three branch models, then the ammonia storage of the corresponding branch model is obtained based on the area proportion of each branch model and the efficiency correction coefficient, the NOx mass flow of the corresponding branch model is obtained based on the area proportion of each branch model, and the ammonia consumption and the NOx consumption are calculated based on the ammonia storage and the NOx mass flow of each model, and the final result is obtained by comprehensively processing the above data.

[0064] As shown in Figure 3 , the embodiment of the application further provides a corrected SCR efficiency model applied to an SCR injection system, which comprises:

[0065] a data collection unit configured to collect temperature, space velocity, NOx flow, and ammonia flow data;

[0066] a data processing unit configured to look up an efficiency correction coefficient map based on the temperature and space velocity data to obtain the corresponding efficiency correction coefficient, and calculate the NOx flow and ammonia flow data of each branch model based on the efficiency correction coefficient;

[0067] a branch model configured to calculate the conversion efficiency of each branch model based on the NOx flow and ammonia flow data of the branch model;

[0068] a summary unit configured to calculate the total conversion efficiency based on the conversion efficiency of each branch model.

[0069] In one specific embodiment of the present application, the modified SCR efficiency model further comprises a modification module, which comprises:

[0070] a conversion efficiency confirmation module, configured to obtain actual conversion efficiency of the close-coupled SCR and conversion efficiency of different measuring points;

[0071] a data analysis module, configured to classify the measuring points according to deviation of conversion efficiency of each point from actual efficiency to obtain a plurality of branch models, and sequentially calculate area proportion and efficiency correction coefficient of each branch model; and further configured to correct the efficiency coefficient of each branch model based on temperature and space velocity to form an efficiency correction coefficient map.

[0072] In one specific embodiment of the present application, the data analysis module comprises:

[0073] a data classification module, configured to divide a plurality of numerical ranges by taking actual efficiency as a benchmark using a preset gradient, and classify the measuring points falling into the same numerical range into one category to form a branch model;

[0074] a data calculation module, configured to calculate the average efficiency of the measuring points of the same category, and calculate the ratio of the average efficiency to the actual efficiency as the efficiency correction coefficient of the branch model; and further configured to calculate the number of the measuring points of the same category, and calculate the ratio of the number of the measuring points of the same category to the total number of the measuring points as the area proportion of the branch model.

[0075] The SCR efficiency model modification method of the embodiment of the present application is obtained by performing multiple tests under different temperature and space velocity conditions, and calculating the efficiency correction coefficient map and a plurality of branch models according to the required precision, wherein the calculation logic of the branch models is the same as that of the original SCR model. Then, the NH3 entering each branch model during injection is corrected based on the efficiency correction coefficient map, so as to reduce the deviation between the calculation result and the actual situation. In addition, the calculation logic of the branch model is the same as that of the original SCR model, so that the modified SCR efficiency model can be stacked by a plurality of original SCR efficiency models, or only one original SCR efficiency model can be used for multiple calculations.

[0076] The embodiment of the present application further provides a vehicle comprising the above-mentioned SCR efficiency model modification device.

[0077] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of correcting a corrected SCR efficiency model, characterized by, The method comprises the following steps: calculating the actual conversion efficiency of the SCR model and the conversion efficiency of different measuring points in the cross section of the SCR carrier; classifying the measuring points according to the deviation of the conversion efficiency of each measuring point from the actual conversion efficiency to obtain a plurality of branch models, and sequentially calculating the area proportion and the efficiency correction coefficient of each branch model; correcting the efficiency coefficient of each branch model based on the temperature and the space velocity to form an efficiency correction coefficient map; calculating the flow rates of NOx and ammonia flowing into each branch model and the conversion efficiency based on the area and the efficiency correction coefficient, and calculating the corrected SCR efficiency model efficiency based on the conversion efficiency of each branch model; the classification of the measuring points according to the deviation of the conversion efficiency of each point from the actual efficiency to obtain a plurality of branch models, and the sequential calculation of the area proportion and the efficiency correction coefficient of each branch model comprise: dividing a plurality of numerical ranges with the actual efficiency as the benchmark by using a preset gradient, and classifying the measuring points falling into the same numerical range as the same type to form a branch model, the ratio of the average efficiency of the same type measuring points to the actual efficiency being the efficiency correction coefficient of the branch model, and the ratio of the number of the same type measuring points to the total number of measuring points being the area proportion of the branch model; the correction of the efficiency coefficient of each branch model based on the temperature and the space velocity to form an efficiency correction coefficient map comprises: repeating the urea injection at different temperatures and space velocities to obtain the efficiency correction coefficients at different temperatures and space velocities, and combining a plurality of efficiency correction coefficients to obtain the efficiency correction coefficient map.

2. The method of claim 1, wherein, the calculation of the actual efficiency of the SCR model and the conversion efficiency of different measuring points in the cross section comprises: arranging a plurality of test points uniformly in the longitudinal cross section of the SCR carrier, injecting urea at a set ammonia nitrogen ratio less than 1 to obtain the actual conversion efficiency of the SCR model and the conversion efficiency of different measuring points.

3. The method of claim 1, wherein, The number of branch models is at least 3.

4. The method of claim 1, wherein, the calculation of the flow rates of NOx and ammonia flowing into each branch model based on the area proportion and the efficiency correction coefficient comprises: the flow rate of NOx input into each branch model is proportional to the area proportion of the branch model; the ammonia flow rate input into each branch model is proportional to the area proportion and the efficiency correction coefficient of the branch model, and the efficiency correction coefficient is obtained based on the efficiency correction coefficient map.

5. A modified SCR efficiency model characterized by, The method is applied to an SCR injection system, which comprises: a data collection unit for collecting temperature, space velocity, NOx flow rate and ammonia flow rate data; a data processing unit for searching the efficiency correction coefficient map based on the temperature and space velocity data to obtain the corresponding efficiency correction coefficient, and calculating the NOx flow rate and ammonia flow rate data of each branch model based on the efficiency correction coefficient; a branch model for calculating the conversion efficiency of each branch model based on the NOx flow rate and ammonia flow rate data of the branch model; a summary unit for calculating the total conversion efficiency based on the conversion efficiency of each branch model; and further comprising a correction module, which comprises: a conversion efficiency confirmation module for obtaining the actual conversion efficiency of the close-coupled SCR and the conversion efficiency of different measuring points. The data analysis module is configured to classify the measuring points according to the deviation between the conversion efficiency and the actual efficiency to obtain a plurality of branch models, and sequentially calculate the area proportion and the efficiency correction coefficient of each branch model; and is further configured to correct the efficiency coefficient of each branch model based on the temperature and the space velocity to form an efficiency correction coefficient map. The data analysis module comprises: The data classification module is configured to divide a plurality of numerical ranges by taking the actual efficiency as a benchmark using a preset gradient, and classify the measuring points with the actual efficiency falling into the same numerical range into one category to form a branch model; The data calculation module is configured to calculate the average efficiency of the measuring points in the same category, and calculate the ratio between the average efficiency and the actual efficiency as the efficiency correction coefficient of the branch model; and is further configured to calculate the number of the measuring points in the same category, and calculate the ratio between the number of the measuring points in the same category and the total number of the measuring points as the area proportion of the branch model.

6. A vehicle characterized by comprising: The corrected SCR efficiency model of claim 5 is included.

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