Method and apparatus for determining maximum performance of scr

Abstract

This invention discloses a method and apparatus for determining the maximum performance of a split-phase catalytic converter (SCR). In this method, for the i-th second within the injection duration, the urea injection rate at the i-th second and the upstream NO concentration at the i-th second are considered. X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in second i is calculated based on the mass flow rate and SCR conversion factor, and the upstream NO in second i is used as a reference. X The concentration of NO in the downstream region at the i-th second X The concentration is used to calculate the SCR conversion efficiency in the i-th second, where i is a positive integer. The maximum ammonia storage capacity of the SCR at the current temperature is calculated by integrating the total ammonia storage capacity over the injection duration. The highest conversion efficiency among the conversion efficiencies in each second within the injection duration is taken as the highest conversion efficiency of the SCR at the current temperature. Using the method of this invention, the maximum ammonia storage capacity and the highest conversion efficiency of the SCR can be measured quickly and accurately.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of SCR technology, in particular to a method and device for judging the maximum performance of SCR. BACKGROUND

[0002] Currently, in order to meet the requirements of regulations, it is necessary to reduce the NOx emission pollutants in exhaust gas, and the key point of reducing NOx emission pollutants mainly lies in the ammonia storage amount of SCR and the conversion efficiency of SCR.

[0003] The ammonia storage amount of SCR and the conversion efficiency of SCR are mainly affected by the exhaust gas temperature and the exhaust gas flow. In the test phase, the maximum ammonia storage amount of SCR is usually measured by spraying urea, and when ammonia leakage is detected downstream of the SCR system, it is considered that the ammonia storage amount at this time is the maximum ammonia storage amount under the current exhaust gas temperature and exhaust gas flow. The maximum efficiency of reducing NOx during urea injection is the maximum conversion efficiency of SCR under the current exhaust gas temperature and exhaust gas flow. The efficiency of reducing NOx calculated under different ammonia storage amounts during the test is the conversion efficiency of SCR under the current ammonia storage amount of SCR.

[0004] Since the ammonia storage amount of SCR decreases as the temperature increases, the ammonia storage amount of SCR at low temperature is the maximum. For example: the SCR matched with a 10L diesel engine, the exhaust temperature is below 200℃, and the maximum ammonia storage amount of SCR is generally about 40g, while the exhaust temperature is greater than 300℃, and the maximum ammonia storage amount of SCR is less than 5g. In the existing method, the urea injection amount does not match the current temperature of the SCR, which results in a long test time for ammonia leakage to occur during low temperature testing. Since the test time is long, measurement deviation will occur, making it impossible to quickly and accurately measure the maximum ammonia storage amount of SCR and the highest conversion efficiency of SCR. SUMMARY

[0005] The present application provides a method and device for judging the maximum performance of SCR, which achieves the purpose of quickly and accurately measuring the maximum ammonia storage amount of SCR and the highest conversion efficiency of SCR. The specific technical solutions are as follows.

[0006] In a first aspect, the present application provides a method for judging the maximum performance of SCR, which comprises:

[0007] The urea injection amount is closed by a vector switch, the target engine is controlled to run to a rated operating point for selective catalytic reduction (SCR) emptying, and when the emptying is completed, the target engine is switched from the rated operating point to a target operating point;

[0008] When the unit temperature change amount of the SCR is less than a preset temperature change amount threshold, the current temperature of the SCR and the upstream NOX The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at the target urea injection rate. When the ammonia leakage concentration downstream of the SCR is detected to reach a preset concentration threshold, the urea pump is controlled to stop injecting urea. The current temperature is lower than the preset temperature.

[0009] Determine the injection time from the start of urea injection to the stop of urea injection, and calculate the total mass of urea by integrating the amount of urea injected during the injection time;

[0010] For the upstream NO corresponding to the injection duration X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass is calculated by integrating the ammonia leakage mass flow rate corresponding to the injection duration. The upstream NO is then calculated. X Total mass and the downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass is used to calculate the SCR conversion coefficient, where the SCR conversion NO X The total mass is the NO converted by the SCR during the injection duration. X Total mass;

[0011] For the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO at the i-th second... X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in the i-th second is calculated based on the mass flow rate and the SCR conversion coefficient, and the upstream NO in the i-th second is used as a reference. X The concentration of NO in the downstream region at the i-th second X The concentration is used to calculate the conversion efficiency of the SCR in the i-th second, where i is a positive integer;

[0012] The maximum ammonia storage capacity of the SCR at the current temperature is obtained by integrating all ammonia storage capacity within the injection duration. The highest conversion efficiency among the conversion efficiencies of each second within the injection duration is taken as the highest conversion efficiency of the SCR at the current temperature.

[0013] Optionally, the step is based on the current temperature of the SCR and the upstream NO of the SCR. X The steps for determining the target urea injection quantity using mass flow rate include:

[0014] When the current temperature of the SCR is no greater than 200 degrees Celsius, the target urea injection rate is determined to be 8 times the upstream NO. X Mass flow rate;

[0015] When the current temperature of the SCR is greater than 200 degrees Celsius but not greater than 400 degrees Celsius, the target urea injection rate is determined to be 6 times the upstream NO. X Mass flow rate;

[0016] When the current temperature of the SCR is greater than 400 degrees Celsius but not greater than 600 degrees Celsius, the target urea injection rate is determined to be 4 times the upstream NO. X Mass flow rate.

[0017] Optionally, the step involves adjusting the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The steps for calculating the SCR conversion factor based on total mass include:

[0018] Calculate the first quotient between the total mass of urea and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia;

[0019] Calculate the first difference between the first quotient and the total mass of the ammonia leak;

[0020] Calculate the first difference and the SCR conversion NO. X The ratio of total mass yields the SCR conversion factor.

[0021] Optionally, the step of determining the urea injection rate at the i-th second and the upstream NO at the i-th second... X Mass flow rate, downstream NO in the i-th second X The step of calculating the ammonia storage capacity of the SCR in the i-th second using the mass flow rate and the SCR conversion coefficient includes:

[0022] Calculate the second quotient between the urea injection rate at the i-th second and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia;

[0023] Calculate the upstream NO in the i-th second. X The mass flow rate and the downstream NO at the i-th second X The second difference between the mass flow rates;

[0024] Calculate the first product between the second difference and the SCR conversion coefficient;

[0025] The third difference between the second quotient and the first product is used to obtain the ammonia storage amount of the SCR in the i-th second.

[0026] Optionally, the upstream NO based on the i-th second XThe concentration of NO in the downstream region at the i-th second X The step of calculating the SCR conversion efficiency in the i-th second by the concentration includes:

[0027] Calculate the upstream NO in the i-th second. X The concentration of NO in the downstream region at the i-th second X The fourth difference between concentrations;

[0028] Calculate the fourth difference and the upstream NO in the i-th second. X The conversion efficiency of the SCR in the i-th second is obtained by the ratio of the concentrations.

[0029] Optionally, after the step of taking the highest conversion efficiency among the conversion efficiencies in each second within the injection duration as the highest conversion efficiency of the SCR at the current temperature, the above method for determining the maximum performance of the SCR further includes:

[0030] The conversion efficiency in the i-th second is taken as the conversion efficiency corresponding to the total ammonia storage of the SCR in the first i seconds at the current temperature.

[0031] Secondly, the present invention provides an apparatus for determining the maximum performance of an SCR, the apparatus comprising:

[0032] The purging module is used to shut off the urea injection quantity through a vector switch, control the target engine to run to the rated operating point to purge the selective catalytic reduction (SCR), and switch the target engine from the rated operating point to the target operating point when the purging is complete.

[0033] The urea injection module is used to, when the unit temperature change of the SCR is less than a preset temperature change threshold, determine the urea injection method based on the current temperature of the SCR and the upstream NO of the SCR. X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at the target urea injection rate. When the ammonia leakage concentration downstream of the SCR is detected to reach a preset concentration threshold, the urea pump is controlled to stop injecting urea. The current temperature is lower than the preset temperature.

[0034] The total urea mass calculation module is used to determine the injection time from the start of urea injection to the stop of urea injection, and to calculate the total urea mass by integrating the amount of urea injected during the injection time.

[0035] The conversion coefficient calculation module is used to calculate the upstream NO corresponding to the injection duration. X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. XThe total mass is calculated by integrating the ammonia leakage mass flow rate corresponding to the injection duration. The upstream NO is then calculated. X Total mass and the downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass is used to calculate the SCR conversion coefficient, where the SCR conversion NO X The total mass is the NO converted by the SCR during the injection duration. X Total mass;

[0036] The first conversion efficiency calculation module is used to calculate the urea injection rate and the upstream NO concentration for the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO concentration at the i-th second. X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in the i-th second is calculated based on the mass flow rate and the SCR conversion coefficient, and the upstream NO in the i-th second is used as a reference. X The concentration of NO in the downstream region at the i-th second X The concentration is used to calculate the conversion efficiency of the SCR in the i-th second, where i is a positive integer;

[0037] The determination module integrates all ammonia storage amounts within the injection duration to obtain the maximum ammonia storage amount of the SCR at the current temperature, and takes the highest conversion efficiency among the conversion efficiencies of each second within the injection duration as the highest conversion efficiency of the SCR at the current temperature.

[0038] Optionally, the urea injection module is specifically used for:

[0039] When the current temperature of the SCR is no greater than 200 degrees Celsius, the target urea injection rate is determined to be 8 times the upstream NO. X Mass flow rate;

[0040] When the current temperature of the SCR is greater than 200 degrees Celsius but not greater than 400 degrees Celsius, the target urea injection rate is determined to be 6 times the upstream NO. X Mass flow rate;

[0041] When the current temperature of the SCR is greater than 400 degrees Celsius but not greater than 600 degrees Celsius, the target urea injection rate is determined to be 4 times the upstream NO. X Mass flow rate.

[0042] Optionally, the conversion coefficient calculation module includes:

[0043] The first quotient calculation submodule is used to calculate the first quotient between the total mass of urea and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia;

[0044] The first difference calculation submodule is used to calculate the first difference between the first quotient and the total mass of the ammonia leak;

[0045] The SCR conversion coefficient calculation submodule is used to calculate the first difference and the SCR conversion NO. X The ratio of total mass yields the SCR conversion factor.

[0046] Optionally, the first conversion efficiency calculation module includes:

[0047] The second quotient calculation submodule is used to calculate the second quotient between the urea injection amount at the i-th second and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia.

[0048] The second difference calculation submodule is used to calculate the upstream NO at the i-th second. X The mass flow rate and the downstream NO at the i-th second X The second difference between the mass flow rates;

[0049] The first product calculation submodule is used to calculate the first product between the second difference and the SCR conversion coefficient;

[0050] The ammonia storage calculation submodule is used to calculate the third difference between the second quotient and the first product to obtain the ammonia storage of the SCR in the i-th second.

[0051] Optionally, the first conversion efficiency calculation module includes:

[0052] The fourth difference calculation submodule is used to calculate the upstream NO in the i-th second. X The concentration of NO in the downstream region at the i-th second X The fourth difference between concentrations;

[0053] The conversion efficiency calculation submodule is used to calculate the fourth difference and the upstream NO in the i-th second. X The conversion efficiency of the SCR in the i-th second is obtained by the ratio of the concentrations.

[0054] Optionally, the above-mentioned device for determining the maximum performance of the SCR also includes:

[0055] The second conversion efficiency calculation module is used to take the conversion efficiency of the i-th second as the conversion efficiency corresponding to the total ammonia storage of the SCR in the first i seconds at the current temperature, after taking the maximum conversion efficiency among the conversion efficiencies of each second within the injection duration as the highest conversion efficiency of the SCR at the current temperature.

[0056] As described above, the method and apparatus for determining the maximum performance of a selective catalytic converter (SCR) provided in this embodiment of the invention can shut off the urea injection quantity via a vector switch, control the target engine to operate at its rated operating point for SCR purging, and when purging is complete, switch the target engine from its rated operating point to its target operating point. When the unit temperature change of the SCR is less than a preset temperature change threshold, the method determines the maximum performance based on the current temperature of the SCR and the upstream NO content of the SCR. X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at this target rate. When the downstream ammonia leakage concentration of the SCR reaches a preset concentration threshold, the urea pump stops injecting urea. The current temperature is lower than a preset temperature. The injection time from the start to the stop of urea injection is determined. The total urea mass is calculated by integrating the urea injection rate over this time. The upstream NO content corresponding to the injection time is then calculated. X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass of the ammonia leak is calculated by integrating the mass flow rate of the ammonia leak corresponding to the injection time. The upstream NO₂ is then calculated. X Total mass and downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass calculation yields the SCR conversion factor, where SCR conversion NO X The total mass is the NO converted by SCR during the injection time. X Total mass, for the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO at the i-th second. X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in second i is calculated based on the mass flow rate and SCR conversion factor, and the upstream NO in second i is used as a reference. X The concentration of NO in the downstream region at the i-th second X The SCR conversion efficiency at the i-th second is calculated by the concentration of nitrogen, where i is a positive integer. The maximum ammonia storage capacity of the SCR at the current temperature is calculated by integrating all ammonia storage capacities within the injection duration. The highest conversion efficiency among the conversion efficiencies of each second within the injection duration is taken as the highest conversion efficiency of the SCR at the current temperature. Therefore, in this invention, when the current temperature is lower than a preset temperature, the conversion efficiency is determined based on the current temperature of the SCR and the upstream NO concentration. XThe mass flow rate determines the target urea injection quantity, ensuring that the target urea injection quantity matches the current temperature of the SCR, neither too high nor too low. This allows ammonia leakage to occur within a short time, reducing the test time for ammonia leakage during low-temperature tests and minimizing measurement deviations caused by long test times. The maximum ammonia storage capacity of the SCR at the current temperature is calculated by integrating all ammonia storage amounts within the injection time. The highest conversion efficiency among the conversion efficiencies in each second within the injection time is taken as the highest conversion efficiency of the SCR at the current temperature, achieving the goal of quickly and accurately measuring the maximum ammonia storage capacity and the highest conversion efficiency of the SCR. Of course, implementing any product or method of this invention does not necessarily require achieving all of the above advantages simultaneously.

[0057] The innovative aspects of this invention include:

[0058] 1. When the current temperature is lower than the preset temperature, based on the current temperature of the SCR and the upstream NO of the SCR... X The mass flow rate determines the target urea injection quantity, ensuring that the target urea injection quantity matches the current temperature of the SCR, neither too high nor too low. This allows ammonia leakage to occur in a shorter time, reducing the test time for ammonia leakage during low-temperature tests and minimizing measurement deviations caused by long test times. By integrating all ammonia storage quantities within the injection time, the maximum ammonia storage quantity of the SCR at the current temperature is obtained. The highest conversion efficiency among the conversion efficiencies in each second within the injection time is taken as the highest conversion efficiency of the SCR at the current temperature, achieving the goal of quickly and accurately measuring the maximum ammonia storage quantity and the highest conversion efficiency of the SCR.

[0059] 2. By taking the conversion efficiency of the i-th second as the conversion efficiency corresponding to the total ammonia storage of the SCR in the first i seconds at the current temperature, it is convenient to calibrate the conversion efficiency of the SCR under different total ammonia storage.

[0060] 3. This embodiment of the invention provides a method based on the current temperature of the SCR and the upstream NO of the SCR. X The method of determining the target urea injection rate using mass flow rate ensures that the target urea injection rate is matched with the current temperature of the SCR. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0062] Figure 1A flowchart illustrating a method for determining the maximum performance of an SCR according to an embodiment of the present invention;

[0063] Figure 2 This is a schematic diagram of a device for determining the maximum performance of an SCR according to an embodiment of the present invention. Detailed Implementation

[0064] 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 a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0065] It should be noted that the terms "comprising" and "having," and any variations thereof, in the embodiments and drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0066] This invention discloses a method and apparatus for determining the maximum performance of an SCR (Selective Catalytic Reduction) system, which can quickly and accurately measure the maximum ammonia storage capacity and the highest conversion efficiency of the SCR. The embodiments of this invention are described in detail below.

[0067] Figure 1 This is a flowchart illustrating a method for determining the maximum performance of a Spark Regulator (SCR) according to an embodiment of the present invention. The method is applied to electronic devices. Specifically, the method includes the following steps.

[0068] S110: By shutting off the urea injection quantity through the vector switch, the target engine is controlled to run to the rated operating point to purge the selective catalytic reduction (SCR). Once purging is complete, the target engine is switched from the rated operating point to the target operating point.

[0069] To measure the maximum ammonia storage capacity of the SCR, the ammonia storage capacity inside the SCR needs to be consumed first. Therefore, the SCR needs to be emptied. Specifically, the urea injection quantity is turned off by a vector switch, and the target engine is controlled to run at the rated operating point to empty the selective catalytic reduction SCR. The target engine is the engine whose maximum ammonia storage capacity and highest conversion efficiency of the SCR need to be measured. The rated operating point is the calibrated operating point of the target engine, that is, the engine's maximum output power and the engine's maximum torque at the speed corresponding to the rated power.

[0070] Once the emptying is complete, it means that the ammonia storage inside the SCR has been consumed. At this point, the target engine can be switched from the rated operating point to the target operating point, which is the operating point at which the maximum ammonia storage and highest conversion efficiency of the SCR need to be measured.

[0071] Specifically, the method to determine if the clearing is complete can be: when the upstream NO of SCR... X Concentration and downstream NO X The concentration difference is less than the preset NO X Concentration threshold, confirming the cleanup is complete, where NO is preset. X The concentration threshold can be 20 ppm, and NOx is a nitrogen oxide compound.

[0072] S120: When the unit temperature change of the SCR is less than the preset temperature change threshold, based on the current temperature of the SCR and the upstream NO of the SCR... X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at the target urea injection rate. When the ammonia leakage concentration downstream of the SCR is detected to reach the preset concentration threshold, the urea pump is controlled to stop injecting urea. The current temperature is lower than the preset temperature.

[0073] After switching the target engine from its rated operating point to its target operating point, an SCR filling test, which involves re-injecting urea, is required to measure the maximum ammonia storage capacity and highest conversion efficiency of the SCR.

[0074] Specifically, when the SCR temperature stabilizes, i.e., the unit temperature change of the SCR is less than a preset temperature change threshold, the current temperature of the SCR and the upstream NO of the SCR are used as the basis for determining the SCR temperature. X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at the target urea injection rate. When the downstream ammonia leakage concentration of the SCR is detected to reach the preset concentration threshold, the urea pump is controlled to stop injecting urea. At this time, the SCR filling test ends. The test data obtained from the SCR filling test can be recorded and saved at a sampling frequency of 1 second.

[0075] The current temperature of the SCR can be measured by a temperature sensor and is lower than a preset temperature. The ammonia leakage concentration downstream of the SCR can be measured by an ammonia analyzer. The unit temperature change is the temperature change per unit time. For example, the unit time can be 1 minute, the preset temperature change threshold can be 2 degrees Celsius, the preset temperature can be 200 degrees Celsius, and the preset concentration threshold can be 10 ppm.

[0076] The above is based on the current temperature of the SCR and the upstream NO of the SCR. X Determining the target urea injection quantity based on mass flow rate can include:

[0077] When the current temperature of the SCR is no greater than 200 degrees Celsius, the target urea injection rate is determined to be 8 times the upstream NO. X Mass flow rate;

[0078] When the current temperature of the SCR is greater than 200 degrees Celsius but not greater than 400 degrees Celsius, the target urea injection rate is determined to be 6 times the upstream NO. X Mass flow rate;

[0079] When the current temperature of the SCR is greater than 400 degrees Celsius but not greater than 600 degrees Celsius, the target urea injection rate is determined to be 4 times the upstream NO. X Mass flow rate.

[0080] Among them, the upstream NO of SCR X Mass flow can be achieved through NO X Measured by a mass flow sensor.

[0081] The target urea injection volume can be determined using the following table:

[0082]

[0083]

[0084] Since the embodiment of this invention involves a low-temperature test, i.e., SCRT ≤ 200°C, it can be determined that the target urea injection rate is 8 times the upstream NO. X Mass flow rate.

[0085] Therefore, embodiments of the present invention provide a method based on the current temperature of the SCR and the upstream NO of the SCR. X The method of determining the target urea injection rate using mass flow rate ensures that the target urea injection rate is matched with the current temperature of the SCR.

[0086] S130: Determine the injection time from the start to the stop of urea injection, and calculate the total mass of urea by integrating the amount of urea injected during the injection time.

[0087] After the SCR filling test is completed, the maximum ammonia storage capacity and the highest conversion efficiency of the SCR during the SCR filling test can be calculated. That is, the maximum ammonia storage capacity and the highest conversion efficiency of the SCR during the period from the start of urea injection to the stop of urea injection are calculated.

[0088] First, it is necessary to calculate the total mass of urea during this process. Specifically, determine the injection time from the start of urea injection to the stop of urea injection, and calculate the total mass of urea by integrating the amount of urea injected during the injection time.

[0089] S140: For the upstream NO corresponding to the injection duration X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass of the ammonia leak is calculated by integrating the mass flow rate of the ammonia leak corresponding to the injection time. The upstream NO₂ is then calculated. X Total mass and downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass calculation yields the SCR conversion factor, where SCR conversion NO X The total mass is the NO converted by SCR during the injection time. X Total mass.

[0090] After calculating the total mass of urea, calculate the total mass of ammonia leakage and the SCR conversion coefficient during this process.

[0091] The total mass of ammonia leakage during this process can be calculated as follows:

[0092] For the upstream NO corresponding to the injection duration X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass is calculated by integrating the mass flow rate of the ammonia leak corresponding to the injection duration.

[0093] The SCR conversion factor during this process can be calculated as follows:

[0094] Calculate upstream NO X Total mass and downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass calculation yields the SCR conversion factor, where SCR conversion NO X The total mass is the NO converted by SCR during the injection time. X Total mass.

[0095] The SCR conversion NO is calculated according to the following formula. X Total mass:

[0096] mNOxCnv=mNOxUs-mNOxDs

[0097] Where mNOxCnv is the SCR conversion of NO X Total mass, mNOxUs is the upstream NO X Total mass, mNOxDs represents downstream NO X Total mass.

[0098] The above is based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass calculation yields the SCR conversion factor, which can include:

[0099] Calculate the first quotient between the total mass of urea and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia;

[0100] Calculate the first difference between the first quotient and the total mass of the ammonia leak;

[0101] Calculate the first difference and SCR conversion NO X The ratio of total mass yields the SCR conversion factor.

[0102] Specifically, the SCR conversion factor can be calculated using the following formula:

[0103] fac=(mUDC / 5.425-mNH3) / mNOxCnv

[0104] Where fac is the SCR conversion coefficient, mUDC is the total mass of urea, 5.425 is the preset ratio coefficient for the conversion of urea aqueous solution into ammonia, mNH3 is the total mass of ammonia leakage, and mNOxCnv is the SCR conversion of NO X Total mass.

[0105] S150: For the i-th second within the injection duration, based on the urea injection volume at the i-th second and the upstream NO at the i-th second... X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in second i is calculated based on the mass flow rate and SCR conversion factor, and the upstream NO in second i is used as a reference. X The concentration of NO in the downstream region at the i-th second X The concentration is used to calculate the conversion efficiency of SCR in the i-th second, where i is a positive integer.

[0106] After calculating the total mass of ammonia leakage and the SCR conversion coefficient during this process, the ammonia storage capacity and conversion efficiency of the SCR are calculated for each second during this process, that is, the ammonia storage capacity and conversion efficiency of the SCR in the i-th second are calculated.

[0107] The method for calculating the ammonia storage capacity of the SCR in the i-th second can be as follows:

[0108] For the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO at the i-th second... X Mass flow rate, downstream NO in the i-th second X The mass flow rate and SCR conversion coefficient are used to calculate the ammonia storage capacity of the SCR in the i-th second, where i is a positive integer.

[0109] The above is based on the urea injection rate at second i and the upstream NO at second i. X Mass flow rate, downstream NO in the i-th second X The amount of ammonia stored in the SCR at second i can be calculated from the mass flow rate and SCR conversion factor, and may include:

[0110] Calculate the second quotient between the urea injection rate at the i-th second and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia;

[0111] Calculate the upstream NO at second i. X The mass flow rate and the downstream NO at the i-th second X The second difference between the mass flow rates;

[0112] Calculate the first product between the second difference and the SCR conversion factor;

[0113] The third difference between the second quotient and the first product is used to obtain the amount of ammonia stored in the SCR at the i-th second.

[0114] Specifically, the ammonia storage capacity of the SCR in the i-th second can be calculated using the following formula:

[0115] dmNH3Load[i]=UDC_dm[i] / 5.425-(NOxUs_dm[i]-NOxDs_dm[i])*fac

[0116] Where dmNH3Load[i] is the ammonia storage amount of the SCR in the i-th second, UDC_dm[i] is the urea injection rate in the i-th second, 5.425 is the preset ratio coefficient for the conversion of urea aqueous solution into ammonia, and NOxUs_dm[i] is the upstream NO in the i-th second. X The mass flow rate, NOxDs_dm[i] is the downstream NO at the i-th second. X The mass flow rate is given by fac, where fac is the SCR conversion factor.

[0117] The conversion efficiency of SCR in the i-th second can be calculated as follows:

[0118] For the i-th second within the jet duration, based on the upstream NO of the i-th second... X The concentration of NO in the downstream region at the i-th second X The concentration is used to calculate the conversion efficiency of SCR in the i-th second, where i is a positive integer.

[0119] The above is based on the upstream NO at the i-th second. X The concentration of NO in the downstream region at the i-th second X The concentration calculation yields the SCR conversion efficiency in the i-th second, which can include:

[0120] Calculate the upstream NO at second i. X The concentration of NO in the downstream region at the i-th second X The fourth difference between concentrations;

[0121] Calculate the fourth difference and the upstream NO at the i-th second. X The concentration ratio is used to obtain the conversion efficiency of SCR in the i-th second.

[0122] Specifically, the conversion efficiency of the SCR in the i-th second can be calculated using the following formula:

[0123] SCREta[i]=(NOxUs_ppm[i]-NOxDs_ppm[i]) / NOxUs_ppm[i]

[0124] Where SCREta[i] is the conversion efficiency of SCR in the i-th second, and NOxUs_ppm[i] is the upstream NO concentration in the i-th second. X The concentration of NOxDs_ppm[i] is the downstream NO concentration at the i-th second. X The concentration.

[0125] S160: The maximum ammonia storage capacity of the SCR at the current temperature is obtained by integrating all ammonia storage capacity within the injection time. The highest conversion efficiency among the conversion efficiencies of each second within the injection time is taken as the highest conversion efficiency of the SCR at the current temperature.

[0126] After calculating the ammonia storage capacity and conversion efficiency of the SCR for each second in this process, that is, after calculating the ammonia storage capacity and conversion efficiency of the SCR in the i-th second, the maximum ammonia storage capacity of the SCR at the current temperature can be obtained by integrating all the ammonia storage capacity within the injection time. The maximum conversion efficiency among the conversion efficiencies in each second within the injection time is taken as the highest conversion efficiency of the SCR at the current temperature.

[0127] Specifically, the maximum ammonia storage capacity of the SCR at the current temperature is calculated using the following formula:

[0128]

[0129] Where mNH3Load[j] is the maximum ammonia storage capacity of the SCR at the current temperature, dmNH3Load[j] is the ammonia storage capacity of the SCR at the j-th second, k is the start time of urea injection, and j is the stop time of urea injection.

[0130] Similarly, the total ammonia stored by the SCR in the first i seconds at the current temperature can be calculated using the following formula:

[0131]

[0132] Where mNH3Load[i] is the total amount of ammonia stored by the SCR in the first i seconds at the current temperature, and dmNH3Load[i] is the amount of ammonia stored by the SCR in the i-th second.

[0133] In summary, when the engine is running at the target operating point, the maximum ammonia storage capacity and the highest conversion efficiency of the SCR at the current temperature are measured. When it is necessary to measure other target operating points, the method for determining the maximum performance of the SCR provided in this embodiment of the invention can be repeated.

[0134] As described above, this embodiment can shut off the urea injection quantity via a vector switch, controlling the target engine to operate at its rated operating point for selective catalytic reduction (SCR) purging. Once purging is complete, the target engine is switched from its rated operating point to its target operating point. When the unit temperature change of the SCR is less than a preset temperature change threshold, the current temperature of the SCR and the upstream NO content of the SCR are used to determine the appropriate operating conditions. X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at this target rate. When the downstream ammonia leakage concentration of the SCR reaches a preset concentration threshold, the urea pump stops injecting urea. The current temperature is lower than a preset temperature. The injection time from the start to the stop of urea injection is determined. The total urea mass is calculated by integrating the urea injection rate over this time. The upstream NO content corresponding to the injection time is then calculated. X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass of the ammonia leak is calculated by integrating the mass flow rate of the ammonia leak corresponding to the injection time. The upstream NO₂ is then calculated. X Total mass and downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass calculation yields the SCR conversion factor, where SCR conversion NO X The total mass is the NO converted by SCR during the injection time. X Total mass, for the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO at the i-th second. X Mass flow rate, downstream NO in the i-th second XThe ammonia storage capacity of the SCR in second i is calculated based on the mass flow rate and SCR conversion factor, and the upstream NO in second i is used as a reference. X The concentration of NO in the downstream region at the i-th second X The SCR conversion efficiency at the i-th second is calculated by the concentration of nitrogen, where i is a positive integer. The maximum ammonia storage capacity of the SCR at the current temperature is calculated by integrating all ammonia storage capacities within the injection duration. The highest conversion efficiency among the conversion efficiencies of each second within the injection duration is taken as the highest conversion efficiency of the SCR at the current temperature. Therefore, in this invention, when the current temperature is lower than a preset temperature, the conversion efficiency is determined based on the current temperature of the SCR and the upstream NO concentration. X The mass flow rate determines the target urea injection quantity, ensuring that the target urea injection quantity matches the current temperature of the SCR, neither too high nor too low. This allows ammonia leakage to occur in a shorter time, reducing the test time for ammonia leakage during low-temperature tests and minimizing measurement deviations caused by long test times. By integrating all ammonia storage quantities within the injection time, the maximum ammonia storage quantity of the SCR at the current temperature is obtained. The highest conversion efficiency among the conversion efficiencies in each second within the injection time is taken as the highest conversion efficiency of the SCR at the current temperature, achieving the goal of quickly and accurately measuring the maximum ammonia storage quantity and the highest conversion efficiency of the SCR.

[0135] After step S160, the method for determining the maximum performance of the SCR may further include:

[0136] The conversion efficiency at the i-th second is taken as the conversion efficiency corresponding to the total ammonia storage of the SCR in the first i seconds at the current temperature.

[0137] Since the amount of ammonia stored in the SCR increases over time, the conversion efficiency in the i-th second is the conversion efficiency corresponding to the total amount of ammonia stored in the SCR in the previous i seconds at the current temperature.

[0138] Therefore, by taking the conversion efficiency of the i-th second as the conversion efficiency corresponding to the total ammonia storage of the SCR in the previous i seconds at the current temperature, it is convenient to subsequently calibrate the conversion efficiency of the SCR under different total ammonia storage.

[0139] Figure 2 An apparatus for determining the maximum performance of an SCR is provided in an embodiment of the present invention. See also: Figure 2 The device includes:

[0140] The purging module 210 is used to shut off the urea injection quantity through a vector switch, control the target engine to run to the rated operating point to purge the selective catalytic reduction (SCR), and when the purging is completed, switch the target engine from the rated operating point to the target operating point.

[0141] The urea injection module 220 is used to, when the unit temperature change of the SCR is less than a preset temperature change threshold, determine the urea injection method based on the current temperature of the SCR and the upstream NO of the SCR. X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at the target urea injection rate. When the ammonia leakage concentration downstream of the SCR is detected to reach a preset concentration threshold, the urea pump is controlled to stop injecting urea. The current temperature is lower than the preset temperature.

[0142] The total urea mass calculation module 230 is used to determine the injection time from the start of urea injection to the stop of urea injection, and to calculate the total urea mass by integrating the amount of urea injected during the injection time.

[0143] The conversion coefficient calculation module 240 is used to calculate the upstream NO corresponding to the injection duration. X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass is calculated by integrating the ammonia leakage mass flow rate corresponding to the injection duration. The upstream NO is then calculated. X Total mass and the downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass is used to calculate the SCR conversion coefficient, where the SCR conversion NO X The total mass is the NO converted by the SCR during the injection duration. X Total mass;

[0144] The first conversion efficiency calculation module 250 is used to calculate the urea injection rate and the upstream NO concentration for the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO concentration at the i-th second. X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in the i-th second is calculated based on the mass flow rate and the SCR conversion coefficient, and the upstream NO in the i-th second is used as a reference. X The concentration of NO in the downstream region at the i-th second X The concentration is used to calculate the conversion efficiency of the SCR in the i-th second, where i is a positive integer;

[0145] The determination module 260 performs an integral calculation on all ammonia storage amounts within the injection duration to obtain the maximum ammonia storage amount of the SCR at the current temperature, and takes the highest conversion efficiency among the conversion efficiencies of each second within the injection duration as the highest conversion efficiency of the SCR at the current temperature.

[0146] The device provided in this embodiment of the invention can shut off the urea injection quantity via a vector switch, control the target engine to operate at its rated operating point for selective catalytic reduction (SCR) purging, and once purging is complete, switch the target engine from its rated operating point to its target operating point. When the unit temperature change of the SCR is less than a preset temperature change threshold, based on the current temperature of the SCR and the upstream NO of the SCR... X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at this target rate. When the downstream ammonia leakage concentration of the SCR reaches a preset concentration threshold, the urea pump stops injecting urea. The current temperature is lower than a preset temperature. The injection time from the start to the stop of urea injection is determined. The total urea mass is calculated by integrating the urea injection rate over this time. The upstream NO content corresponding to the injection time is then calculated. X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass of the ammonia leak is calculated by integrating the mass flow rate of the ammonia leak corresponding to the injection time. The upstream NO₂ is then calculated. X Total mass and downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass calculation yields the SCR conversion factor, where SCR conversion NO X The total mass is the NO converted by SCR during the injection time. X Total mass, for the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO at the i-th second. X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in second i is calculated based on the mass flow rate and SCR conversion factor, and the upstream NO in second i is used as a reference. X The concentration of NO in the downstream region at the i-th second XThe SCR conversion efficiency at the i-th second is calculated by the concentration of nitrogen, where i is a positive integer. The maximum ammonia storage capacity of the SCR at the current temperature is calculated by integrating all ammonia storage capacities within the injection duration. The highest conversion efficiency among the conversion efficiencies of each second within the injection duration is taken as the highest conversion efficiency of the SCR at the current temperature. Therefore, in this invention, when the current temperature is lower than a preset temperature, the conversion efficiency is determined based on the current temperature of the SCR and the upstream NO concentration. X The mass flow rate determines the target urea injection quantity, ensuring that the target urea injection quantity matches the current temperature of the SCR, neither too high nor too low. This allows ammonia leakage to occur in a shorter time, reducing the test time for ammonia leakage during low-temperature tests and minimizing measurement deviations caused by long test times. By integrating all ammonia storage quantities within the injection time, the maximum ammonia storage quantity of the SCR at the current temperature is obtained. The highest conversion efficiency among the conversion efficiencies in each second within the injection time is taken as the highest conversion efficiency of the SCR at the current temperature, achieving the goal of quickly and accurately measuring the maximum ammonia storage quantity and the highest conversion efficiency of the SCR.

[0147] In one implementation, the urea injection module 220 can be specifically used for:

[0148] When the current temperature of the SCR is no greater than 200 degrees Celsius, the target urea injection rate is determined to be 8 times the upstream NO. X Mass flow rate;

[0149] When the current temperature of the SCR is greater than 200 degrees Celsius but not greater than 400 degrees Celsius, the target urea injection rate is determined to be 6 times the upstream NO. X Mass flow rate;

[0150] When the current temperature of the SCR is greater than 400 degrees Celsius but not greater than 600 degrees Celsius, the target urea injection rate is determined to be 4 times the upstream NO. X Mass flow rate.

[0151] Optionally, the conversion coefficient calculation module 240 may include:

[0152] The first quotient calculation submodule is used to calculate the first quotient between the total mass of urea and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia;

[0153] The first difference calculation submodule is used to calculate the first difference between the first quotient and the total mass of the ammonia leak;

[0154] The SCR conversion coefficient calculation submodule is used to calculate the first difference and the SCR conversion NO. X The ratio of total mass yields the SCR conversion factor.

[0155] Optionally, the first conversion efficiency calculation module 250 may include:

[0156] The second quotient calculation submodule is used to calculate the second quotient between the urea injection amount at the i-th second and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia.

[0157] The second difference calculation submodule is used to calculate the upstream NO at the i-th second. X The mass flow rate and the downstream NO at the i-th second X The second difference between the mass flow rates;

[0158] The first product calculation submodule is used to calculate the first product between the second difference and the SCR conversion coefficient;

[0159] The ammonia storage calculation submodule is used to calculate the third difference between the second quotient and the first product to obtain the ammonia storage of the SCR in the i-th second.

[0160] Optionally, the first conversion efficiency calculation module 250 may include:

[0161] The fourth difference calculation submodule is used to calculate the upstream NO in the i-th second. X The concentration of NO in the downstream region at the i-th second X The fourth difference between concentrations;

[0162] The conversion efficiency calculation submodule is used to calculate the fourth difference and the upstream NO in the i-th second. X The conversion efficiency of the SCR in the i-th second is obtained by the ratio of the concentrations.

[0163] Optionally, the above-mentioned device for determining the maximum performance of the SCR also includes:

[0164] The second conversion efficiency calculation module is used to take the conversion efficiency of the i-th second as the conversion efficiency corresponding to the total ammonia storage of the SCR in the first i seconds at the current temperature, after taking the maximum conversion efficiency among the conversion efficiencies of each second within the injection duration as the highest conversion efficiency of the SCR at the current temperature.

[0165] The above-described apparatus embodiments correspond to the method embodiments and have the same technical effects. For detailed explanations, please refer to the method embodiments. The apparatus embodiments are derived from the method embodiments; detailed explanations can be found in the method embodiments section, and will not be repeated here.

[0166] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0167] Those skilled in the art will understand that the modules in the apparatus of the embodiments can be distributed in the apparatus of the embodiments as described in the embodiments, or they can be located in one or more devices different from this embodiment with corresponding changes. The modules of the above embodiments can be combined into one module, or they can be further divided into multiple sub-modules.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the maximum performance of an SCR, characterized in that, The method includes: By shutting off the urea injection quantity through a vector switch, the target engine is controlled to run to the rated operating point to purge the selective catalytic reduction (SCR). Once purging is complete, the target engine is switched from the rated operating point to the target operating point. When the unit temperature change of the SCR is less than a preset temperature change threshold, the current temperature of the SCR and the upstream NO of the SCR are used to determine the appropriate parameters. X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at the target urea injection rate. When the ammonia leakage concentration downstream of the SCR is detected to reach a preset concentration threshold, the urea pump is controlled to stop injecting urea. The current temperature is lower than the preset temperature. Determine the injection time from the start of urea injection to the stop of urea injection, and calculate the total mass of urea by integrating the amount of urea injected during the injection time; For the upstream NO corresponding to the injection duration X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass is calculated by integrating the ammonia leakage mass flow rate corresponding to the injection duration. The upstream NO is then calculated. X Total mass and the downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass is used to calculate the SCR conversion coefficient, where the SCR conversion NO X The total mass is the NO converted by the SCR during the injection duration. X Total mass; For the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO at the i-th second... X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in the i-th second is calculated based on the mass flow rate and the SCR conversion coefficient, and the upstream NO in the i-th second is used as a reference. X The concentration of NO in the downstream region at the i-th second X The concentration is used to calculate the conversion efficiency of the SCR in the i-th second, where i is a positive integer; The maximum ammonia storage capacity of the SCR at the current temperature is obtained by integrating all ammonia storage capacity within the injection duration. The highest conversion efficiency among the conversion efficiencies of each second within the injection duration is taken as the highest conversion efficiency of the SCR at the current temperature.

2. The method as described in claim 1, characterized in that, The current temperature of the SCR and the upstream NO of the SCR are used as the basis for this. X The steps for determining the target urea injection quantity using mass flow rate include: When the current temperature of the SCR is no greater than 200 degrees Celsius, the target urea injection rate is determined to be 8 times the upstream NO. X Mass flow rate; When the current temperature of the SCR is greater than 200 degrees Celsius but not greater than 400 degrees Celsius, the target urea injection rate is determined to be 6 times the upstream NO. X Mass flow rate; When the current temperature of the SCR is greater than 400 degrees Celsius but not greater than 600 degrees Celsius, the target urea injection rate is determined to be 4 times the upstream NO. X Mass flow rate.

3. The method as described in claim 1, characterized in that, The total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO are used as the basis. X The steps for calculating the SCR conversion factor based on total mass include: Calculate the first quotient between the total mass of urea and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia; Calculate the first difference between the first quotient and the total mass of the ammonia leak; Calculate the first difference and the SCR conversion NO. X The ratio of total mass yields the SCR conversion factor.

4. The method as described in claim 1, characterized in that, The urea injection rate at the i-th second and the upstream NO at the i-th second are used as the basis for the calculation. X Mass flow rate, downstream NO in the i-th second X The step of calculating the ammonia storage capacity of the SCR in the i-th second using the mass flow rate and the SCR conversion coefficient includes: Calculate the second quotient between the urea injection rate at the i-th second and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia; Calculate the upstream NO in the i-th second. X The mass flow rate and the downstream NO at the i-th second X The second difference between the mass flow rates; Calculate the first product between the second difference and the SCR conversion coefficient; The third difference between the second quotient and the first product is used to obtain the ammonia storage amount of the SCR in the i-th second.

5. The method as described in claim 1, characterized in that, The upstream NO based on the i-th second X The concentration of NO in the downstream region at the i-th second X The step of calculating the SCR conversion efficiency in the i-th second by the concentration includes: Calculate the upstream NO in the i-th second. X The concentration of NO in the downstream region at the i-th second X The fourth difference between concentrations; Calculate the fourth difference and the upstream NO in the i-th second. X The conversion efficiency of the SCR in the i-th second is obtained by the ratio of the concentrations.

6. The method as described in claim 1, characterized in that, After the step of taking the highest conversion efficiency among the conversion efficiencies of each second within the injection duration as the highest conversion efficiency of the SCR at the current temperature, the method further includes: The conversion efficiency in the i-th second is taken as the conversion efficiency corresponding to the total ammonia storage of the SCR in the first i seconds at the current temperature.

7. A device for determining the maximum performance of an SCR, characterized in that, The device includes: The purging module is used to shut off the urea injection quantity through a vector switch, control the target engine to run to the rated operating point to purge the selective catalytic reduction (SCR), and switch the target engine from the rated operating point to the target operating point when the purging is complete. The urea injection module is used to, when the unit temperature change of the SCR is less than a preset temperature change threshold, determine the urea injection method based on the current temperature of the SCR and the upstream NO of the SCR. X The mass flow rate determines the target urea injection rate, and the urea pump is controlled to inject urea at the target urea injection rate. When the ammonia leakage concentration downstream of the SCR is detected to reach a preset concentration threshold, the urea pump is controlled to stop injecting urea. The current temperature is lower than the preset temperature. The total urea mass calculation module is used to determine the injection time from the start of urea injection to the stop of urea injection, and to calculate the total urea mass by integrating the amount of urea injected during the injection time. The conversion coefficient calculation module is used to calculate the upstream NO corresponding to the injection duration. X The upstream NO is obtained by integrating the mass flow rate. X Total mass, for the downstream NO corresponding to the injection duration X The downstream NO is obtained by integrating the mass flow rate. X The total mass is calculated by integrating the ammonia leakage mass flow rate corresponding to the injection duration. The upstream NO is then calculated. X Total mass and the downstream NO X The difference in total mass is used as the SCR conversion NO X Total mass, based on the total mass of urea, the total mass of ammonia leakage, and the SCR conversion of NO. X The total mass is used to calculate the SCR conversion coefficient, where the SCR conversion NO X The total mass is the NO converted by the SCR during the injection duration. X Total mass; The first conversion efficiency calculation module is used to calculate the urea injection rate and the upstream NO concentration for the i-th second within the injection duration, based on the urea injection rate at the i-th second and the upstream NO concentration at the i-th second. X Mass flow rate, downstream NO in the i-th second X The ammonia storage capacity of the SCR in the i-th second is calculated based on the mass flow rate and the SCR conversion coefficient, and the upstream NO in the i-th second is used as a reference. X The concentration of NO in the downstream region at the i-th second X The concentration is used to calculate the conversion efficiency of the SCR in the i-th second, where i is a positive integer; The determination module integrates all ammonia storage amounts within the injection duration to obtain the maximum ammonia storage amount of the SCR at the current temperature, and takes the highest conversion efficiency among the conversion efficiencies of each second within the injection duration as the highest conversion efficiency of the SCR at the current temperature.

8. The apparatus as claimed in claim 7, characterized in that, The urea injection module is specifically used for: When the current temperature of the SCR is no greater than 200 degrees Celsius, the target urea injection rate is determined to be 8 times the upstream NO. X Mass flow rate; When the current temperature of the SCR is greater than 200 degrees Celsius but not greater than 400 degrees Celsius, the target urea injection rate is determined to be 6 times the upstream NO. X Mass flow rate; When the current temperature of the SCR is greater than 400 degrees Celsius but not greater than 600 degrees Celsius, the target urea injection rate is determined to be 4 times the upstream NO. X Mass flow rate.

9. The apparatus as claimed in claim 7, characterized in that, The conversion factor calculation module includes: The first quotient calculation submodule is used to calculate the first quotient between the total mass of urea and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia; The first difference calculation submodule is used to calculate the first difference between the first quotient and the total mass of the ammonia leak; The SCR conversion coefficient calculation submodule is used to calculate the first difference and the SCR conversion NO. X The ratio of total mass yields the SCR conversion factor.

10. The apparatus as claimed in claim 7, characterized in that, The first conversion efficiency calculation module includes: The second quotient calculation submodule is used to calculate the second quotient between the urea injection amount at the i-th second and the preset ratio coefficient for the conversion of urea aqueous solution into ammonia. The second difference calculation submodule is used to calculate the upstream NO at the i-th second. X The mass flow rate and the downstream NO at the i-th second X The second difference between the mass flow rates; The first product calculation submodule is used to calculate the first product between the second difference and the SCR conversion coefficient; The ammonia storage calculation submodule is used to calculate the third difference between the second quotient and the first product to obtain the ammonia storage of the SCR in the i-th second.

11. The apparatus as claimed in claim 7, characterized in that, The first conversion efficiency calculation module includes: The fourth difference calculation submodule is used to calculate the upstream NO in the i-th second. X The concentration of NO in the downstream region at the i-th second X The fourth difference between concentrations; The conversion efficiency calculation submodule is used to calculate the fourth difference and the upstream NO in the i-th second. X The conversion efficiency of the SCR in the i-th second is obtained by the ratio of the concentrations.

12. The apparatus as claimed in claim 7, characterized in that, The device further includes: The second conversion efficiency calculation module is used to take the conversion efficiency of the i-th second as the conversion efficiency corresponding to the total ammonia storage of the SCR in the first i seconds at the current temperature, after taking the maximum conversion efficiency among the conversion efficiencies of each second within the injection duration as the highest conversion efficiency of the SCR at the current temperature.

Images