CN117189329A - Fault diagnosis method of double SCR system, electronic equipment and storage medium - Google Patents
Fault diagnosis method of double SCR system, electronic equipment and storage medium Download PDFInfo
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- 239000003638 chemical reducing agent Substances 0.000 claims description 68
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 32
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Abstract
The application relates to the field of fault diagnosis of an exhaust aftertreatment system, and discloses a fault diagnosis method, electronic equipment and a storage medium of a double-SCR (selective catalytic reduction) system, wherein the diagnosis method is applied to a serial system consisting of a cc-SCR (selective catalytic reduction) unit and an integrated aftertreatment device connected in series with the output end of the cc-SCR; and then, acquiring a supply signal, introducing a failure factor, and determining the failure degree of the cc-SCR and the SCR. The disclosed electronic device is capable of executing the steps of a fault diagnosis method of a dual SCR system. The disclosed computer readable storage medium, program or instructions cause a computer to perform the steps of a fault diagnosis method for a dual SCR system.
Description
Technical Field
The application relates to the field of fault diagnosis of tail gas aftertreatment systems, in particular to a fault diagnosis method of a double-SCR system, electronic equipment and a storage medium.
Background
At present, the next stage emission standard pre-research of the diesel vehicle in China enters a second stage, the ultra-low emission or near-zero emission of the diesel vehicle becomes a future development direction, and in order to meet the emission regulations of the next stage, a close-coupled selective catalytic converter (cc-SCR) is connected in series with the original integrated post-treatment technical route, so that the diesel post-treatment technical route for forming double SCR becomes a research hotspot in the industry field gradually.
The aftertreatment device of the diesel vehicle is faced with the actual working environment of high temperature and high pressure for a long time, so that high aging failure risk exists, particularly, the cc-SCR part mounted at the original exhaust port of the diesel engine is expected to have high aging failure possibility, and in order to ensure the working stability and the service life of the double-SCR aftertreatment device, whether the working performance of the double-SCR aftertreatment device is normal or not needs to be judged in real time, so that diagnosis information is provided for fault-tolerant control after failure.
Therefore, there is a need for a fault diagnosis method for a dual SCR aftertreatment system that can accurately determine a failure piece (cc-SCR and/or SCR) and accurately determine the degree of failure if the failure is detected even if the dual SCR is capable of failure.
Disclosure of Invention
In order to solve the technical problems, the application provides a fault diagnosis method, an electronic device and a storage medium of a dual-SCR aftertreatment system, which can accurately judge a failure part (cc-SCR and/or SCR) and accurately judge the failure degree if the dual-SCR is failed.
The application provides a fault diagnosis method of a double-SCR aftertreatment system, which is applied to a series system consisting of a close-coupled selective catalytic reduction unit cc-SCR and an integrated aftertreatment device connected in series with the output end of the cc-SCR, wherein the integrated aftertreatment device consists of an oxidation catalytic converter DOC, a particle catcher DPF, a selective catalytic converter SCR and an ammonia slip converter ASC which are sequentially connected in series, and the input end of the cc-SCR is connected with an exhaust outlet of a diesel engine; the in-line system further includes a first reductant dosing system that performs reductant dosing at an input of the cc-SCR and a second reductant dosing system that performs reductant dosing at an input of the SCR; characterized in that the method comprises the following steps:
step S10, acquiring a first temperature of an input end of the cc-SCR and a second temperature of an input end of the DOC, determining a first bed temperature of the cc-SCR, interpolating to obtain a first theoretical NOx conversion efficiency of the cc-SCR, and determining a lower NOx conversion efficiency limit of the cc-SCR according to a first preset efficiency factor;
step S20, acquiring a first supply signal of the first reducing agent quantitative supply system, a first NOx concentration of an input end of the cc-SCR and a second NOx concentration of an input end of the DOC, determining the actual NOx conversion efficiency of the cc-SCR, and judging whether the actual NOx conversion efficiency of the cc-SCR is lower than the lower limit of the NOx conversion efficiency of the cc-SCR;
step S30, obtaining the exhaust mass flow of an exhaust outlet of the diesel engine, and determining the failure degree of the cc-SCR according to the exhaust mass flow, the first bed temperature, the first NOx concentration, the second NOx concentration and the first supply signal;
step S40, obtaining a third temperature of an input end of the SCR and a fourth temperature of an output end of the ASC, determining a second bed temperature of the SCR, interpolating to obtain a second theoretical NOx conversion efficiency of the SCR, and determining a lower limit of the NOx conversion efficiency of the SCR according to a second preset efficiency factor;
step S50, obtaining a second supply signal of the second reducing agent quantitative supply system and a third NOx concentration of the output end of the ASC, determining the actual NOx conversion efficiency of the SCR, and judging whether the actual NOx conversion efficiency of the SCR is lower than the lower limit of the NOx conversion efficiency of the SCR;
step S60, determining a failure degree of the SCR according to the exhaust gas mass flow, the second bed temperature, the second NOx concentration, the third NOx concentration, and the second supply signal.
Further, in the step S10, a first bed temperature=k 1 X first temperature +K 2 X second temperature, where K 1 K being the coefficient of influence of the first temperature on the cc-SCR 2 K being the coefficient of influence of the second temperature on the cc-SCR 1 +K 2 ＝1；
In step S40, the second bed temperature=k 3 X third temperature +K 4 X fourth temperature, where K 3 K is the influence coefficient of the third temperature on the SCR 4 K is the influence coefficient of the fourth temperature on the SCR 3 +K 4 ＝1。
Further, in the step S10, a first NOx conversion efficiency preset lower limit value=a first preset efficiency factor×a first theoretical NOx conversion efficiency, where the first preset efficiency factor is a ratio of the lowest conversion efficiency allowed when the cc-SCR works normally to the theoretical conversion efficiency;
in the step S40, a second NOx conversion efficiency preset lower limit value=a second preset efficiency factor×a second theoretical NOx conversion efficiency, where the second preset efficiency factor is a ratio of the minimum conversion efficiency allowed when the SCR is working normally to the theoretical conversion efficiency.
Further, whether the total amount of the first reducing agent entering the cc-SCR is sufficient or not can be judged through the first supply signal, if the first reducing agent is not supplied enough, the first supply signal is regulated, and whether the actual NOx conversion efficiency of the cc-SCR is lower than the lower NOx conversion efficiency limit of the cc-SCR or not is judged again;
and judging whether the total amount of the second reducing agent entering the SCR is sufficient or not through the second supply signal, if the second reducing agent is not sufficiently supplied, adjusting the second supply signal, and then judging whether the actual NOx conversion efficiency of the SCR is lower than the lower limit of the NOx conversion efficiency of the SCR again.
Further, the first reducing agent quantitative supply system comprises a first nozzle, the second reducing agent quantitative supply system comprises a second nozzle, and the first nozzle and the second nozzle are jointly provided with an Electronic Control Unit (ECU);
the first supply signal in the step S20 is sent by the ECU to the first nozzle, including a reducing agent injection timing, an opening degree, and a duration;
the second supply signal in the step S40 is sent by the ECU to the second nozzle, including a reducing agent injection timing, an opening/closing degree, and a duration.
Further, if the actual NOx conversion efficiency of the cc-SCR is less than the lower limit of the NOx conversion efficiency of the cc-SCR, calculating the actual NOx conversion efficiency of the cc-SCR for a plurality of times, and eliminating error interference;
if the actual NOx conversion efficiency of the SCR is smaller than the lower limit of the NOx conversion efficiency of the SCR, calculating the actual NOx conversion efficiency of the cc-SCR for a plurality of times, and eliminating error interference.
Further, if the actual NOx conversion efficiency of the cc-SCR is smaller than the lower limit of the NOx conversion efficiency of the cc-SCR after multiple times of calculation, outputting fault information of cc-SCR catalytic failure;
and if the actual NOx conversion efficiency of the SCR is smaller than the lower limit of the NOx conversion efficiency of the SCR after multiple times of calculation, outputting fault information of SCR catalytic failure.
Further, the step S30 includes: using the exhaust gas mass flow, the first bed temperature, the first NOx concentration, the second NOx concentration and the first supply signal as inputs and utilizing a state balance equation of the cc-SCR, outputting a first ammonia coverage estimation value and a first failure factor estimation value of the cc-SCR, and obtaining a third failure factor estimation value through iteration, wherein the third failure factor estimation value can represent the failure degree of the cc-SCR;
the step S60 includes: and taking the exhaust gas mass flow, the second bed temperature, the second NOx concentration, the third NOx concentration and the second supply signal as inputs, utilizing a state balance equation of the SCR, outputting a second ammonia coverage degree estimated value and a second failure factor estimated value of the SCR, and obtaining a fourth failure factor estimated value through iteration, wherein the fourth failure factor estimated value can represent the failure degree of the SCR.
The application also provides an electronic device, which comprises:
a processor and a memory;
the processor is used for executing the steps of the fault diagnosis method of the double-SCR system by calling the program or the instructions stored in the memory.
The present application also provides a computer-readable storage medium storing a program or instructions that cause a computer to execute the steps of the above-described fault diagnosis method of a dual SCR system.
The embodiment of the application has the following technical effects:
in the embodiment, the lower limit of the NOx conversion efficiency of the cc-SCR and the SCR is determined through monitoring the temperature of the cc-SCR and the SCR, and the actual NOx conversion efficiency of the cc-SCR and the SCR is determined through monitoring the NOx concentration of the cc-SCR and the SCR, so that whether the catalytic performance of the cc-SCR and the SCR is normal or not is judged; and then, acquiring a supply signal, introducing a failure factor, and determining the failure degree of the cc-SCR and the SCR.
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In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a series system of a close-coupled selective catalytic reduction unit cc-SCR and an integrated aftertreatment device coupled in series to the cc-SCR output, according to an embodiment of the present application;
FIG. 2 is a schematic flow chart of a fault diagnosis method for a dual SCR system according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a determination of whether or not a cc-SCR is failed and the degree of failure provided by an embodiment of the present application;
FIG. 4 is a schematic diagram of determining whether or not an SCR fails and the failure degree according to an embodiment of the present application;
fig. 5 is a schematic structural diagram of an electronic device according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the application, are within the scope of the application.
The embodiment provides a double-SCR aftertreatment system which consists of a close-coupled selective catalytic reduction unit cc-SCR and an integrated aftertreatment device connected in series with the cc-SCR output end, wherein the integrated aftertreatment device consists of an oxidation catalytic converter DOC, a particle catcher DPF, a selective catalytic converter SCR and an ammonia slip converter ASC which are sequentially connected in series; the input end of the cc-SCR is connected with an exhaust outlet of the diesel engine; the in-line system further includes a first reductant dosing system that performs reductant dosing at the input of the cc-SCR and a second reductant dosing system that performs reductant dosing at the input of the SCR.
Exemplary, a dual SCR aftertreatment system is shown in fig. 1, comprising: cc-SCR101 in contact with a raw exhaust ("raw exhaust" refers to the initial exhaust gas from the exhaust outlet of the diesel engine, "raw exhaust" enters the aftertreatment device from the most upstream of the aftertreatment route), and DOC102, DPF103, SCR104 and ASC105 connected to each other. In the dual SCR system, there are further included a first temperature sensor 111 and a first NOx sensor 121 for measuring the temperature and NOx concentration at the input of the cc-SCR101, and a first reductant dosing system 131 for performing reductant dosing at the front end of the cc-SCR101, a second temperature sensor 112 and a second NOx sensor 122 for measuring the temperature and NOx concentration at the input of the DOC102, a third temperature sensor 113 for measuring the temperature at the input of the SCR104, and a second reductant dosing system 132 for performing reductant dosing at the front end of the SCR104, a fourth temperature sensor 114 and a third NOx sensor 123 for measuring the temperature and NOx concentration at the output of the ASC105, and an electronic control unit ECU141 for providing a first supply signal to the first reductant dosing system 131 and a second supply signal to the second reductant dosing system 132.
Based on the dual SCR aftertreatment system shown in fig. 1, referring to a flow chart of a diagnostic method applied to the dual SCR aftertreatment system shown in fig. 2, the control method includes the steps of:
step S10, obtaining a first temperature of an input end of the cc-SCR and a second temperature of an input end of the DOC, determining a first bed temperature of the cc-SCR, interpolating to obtain a first theoretical NOx conversion efficiency of the cc-SCR, and determining a lower limit of the NOx conversion efficiency of the cc-SCR according to a first preset efficiency factor.
Alternatively, the first temperature is determined by acquiring a signal of the first temperature sensor 111, and the second temperature is determined by acquiring a signal of the second temperature sensor 112.
Specifically, the first bed temperature is determined as follows: the first temperature and the corresponding first influence coefficient K 1 Multiplying the second temperature by the corresponding second influence coefficient K 2 Multiplying, adding the two multiplication results to obtain a first bed temperature of cc-SCR, i.e. first bed temperature=k 1 X first temperature +K 2 X second temperature, where K 1 +K 2 =1. For example: first influence coefficient K 1 Is 0.5, a second influence coefficient K 2 0.5, then cc-SCR is currently insideTemperature=0.5×first temperature+0.5×second temperature. If the influence degree of the first temperature on the current temperature in the cc-SCR is smaller than that of the second temperature through experimental or simulation calculation and other modes, a first influence coefficient K can be set 1 Is 0.3, a second influence coefficient K 2 Is 0.7 or the first influence coefficient K 1 Is 0.4, a second influence coefficient K 2 0.6, etc.
More specifically, the cc-SCR has a MAP of bed temperatures and theoretical NOx conversion efficiencies, and after determining the first bed temperature, the first theoretical NOx conversion efficiency of the cc-SCR can be interpolated from the MAP. The first preset efficiency factor is a lower limit scale factor preset for the theoretical NOx conversion efficiency of cc-SCR at the current bed temperature, and in actual work, the value of the first preset efficiency factor is in the range of 0.9-1. Thus, multiplying the first preset efficiency factor by the first theoretical NOx conversion efficiency results in a lower NOx conversion efficiency limit for the cc-SCR.
Step S20, a first supply signal of the first reducing agent quantitative supply system, a first NOx concentration of an input end of the cc-SCR and a second NOx concentration of an input end of the DOC are obtained, the actual NOx conversion efficiency of the cc-SCR is determined, and whether the actual NOx conversion efficiency of the cc-SCR is lower than the lower limit of the NOx conversion efficiency of the cc-SCR is judged.
Alternatively, the first NOx concentration is determined by collecting the signal of the first NOx sensor 121, and the second NOx concentration is determined by collecting the signal of the second NOx sensor 122.
FIG. 3 is a schematic diagram of determining whether and to what extent cc-SCR is deactivated, specifically, subtracting a first NOx concentration from a second NOx concentration to obtain a concentration difference, and dividing the concentration difference by the first NOx concentration to obtain cc-SCR actual NOx conversion efficiency, i.e., cc-SCR actual NOx conversion efficiency= (first NOx concentration-second NOx concentration)/first NOx concentration.
Judging the actual NOx conversion efficiency of the cc-SCR and the NOx conversion efficiency lower limit of the cc-SCR:
if the actual NOx conversion efficiency of the cc-SCR is more than or equal to the lower limit of the NOx conversion efficiency of the cc-SCR, judging that the cc-SCR is catalyzed normally;
if the actual NOx conversion efficiency of the cc-SCR is less than the lower NOx conversion efficiency limit of the cc-SCR, the cc-SCR may be subject to catalytic failure and may be further determined by the first supply signal.
First, judging whether the ratio of the first reducing agent supply mass flow rate to the first NOx mass flow rate in the first supply signal accords with the stoichiometric ratio of reaction dynamics, wherein the first NOx mass flow rate is the product of the first NOx concentration and the original machine emission mass flow rate. If the first reducing agent is not sufficiently supplied, the first supply signal of the ECU is regulated, and if the actual NOx conversion efficiency of the regulated cc-SCR is more than or equal to the lower limit of the NOx conversion efficiency of the cc-SCR, the disturbance caused by the first reducing agent supply control strategy can be determined; if the first reducing agent is normally supplied, repeatedly carrying out continuous 5 sampling points to judge the relation between the actual NOx conversion efficiency of the cc-SCR and the lower limit of the NOx conversion efficiency of the cc-SCR, excluding the interference caused by accidental measurement errors, and judging that the cc-SCR is in catalytic failure when the actual NOx conversion efficiency of the cc-SCR at the continuous 5 sampling points is smaller than the lower limit of the NOx conversion efficiency of the cc-SCR.
The first reducing agent quantitative supply system comprises a first supply pump, a first supply pipeline and a first nozzle, wherein the first supply signal is a control signal sent by the electronic control unit ECU to the first reducing agent quantitative supply system, and the content of the signal comprises the moment, the opening and closing degree and the duration of the reducing agent injection executed by the first nozzle. For example, a first reductant dosing system receives a first supply signal, pumps the first reductant through a first supply pump, delivers the first reductant through a first supply line, and ultimately injects the first reductant into the aftertreatment exhaust flow through a first nozzle, based on which a mass flow rate and a total amount of the first reductant injected at the time the first reductant enters the cc-SCR may be determined. The first reductant includes urea.
Step S30, obtaining the exhaust mass flow of an exhaust outlet of the diesel engine, and determining the failure degree of the cc-SCR according to the exhaust mass flow, the first bed temperature, the first NOx concentration, the second NOx concentration and the first supply signal.
Specifically, using as inputs the state balance equation of the cc-SCR with the exhaust mass flow, the first bed temperature, the first NOx concentration, the second NOx concentration, and the first supply signal, a first ammonia coverage estimate and a first failure factor estimate of the cc-SCR are obtainedValues. Wherein the state balance equation of cc-SCR is NOx and NH constructed based on mass conservation and energy conservation 3 The state balance equation, a specific state balance equation, can be described as:
wherein,for cc-SCR downstream NH 3 Molar concentration, mol/m 3 ；/>For cc-SCR downstream NO x Molar concentration, mol/m 3 The method comprises the steps of carrying out a first treatment on the surface of the Theta is NH 3 Coverage; c (C) s Surface active atomic concentration per unit volume of gas, mol/m 3 ；n i,in Mol/s for the molar flow of gas i into the cc-SCR; m is m EG G/s, which is the exhaust gas mass flow; t is the bed temperature of cc-SCR, K; a, a i Is referred to as the pre-finger factor.
Whether hydrothermal aging, sulfur poisoning, alkali metal poisoning, mechanical abrasion and fouling, can lead to reduction of the reactive sites of the cc-SCR catalyst, further reduce the storage capacity of the catalyst for ammonia, and finally lead to removal of NO by the cc-SCR catalyst x Is reduced in performance. The cc-SCR catalyst failure factor is introduced to measure the degree to which the ammonia storage capacity after a cc-SCR catalyst failure is reduced compared to the ammonia storage capacity before failure, i.e., the cc-SCR failure degree. The failure factor of a cc-SCR is defined as the ratio of the number of active sites of the cc-SCR after failure to the number of active sites of fresh cc-SCR, described as:
the failure factor is introduced into the cc-SCR catalyst state equation to obtain the cc-SCR catalyst failure state equation:
from this, it can be seen that the introduction of the failure factor has NO effect on the ammonia storage mass balance equation, but NO x Mass balance equation and NH 3 The mass balance equation has an effect.
The cc-SCR catalyst failure factor state equation may be based on cc-SCR catalyst NO x The mass balance equation is rewritten as:
since the value corresponding to the time caused by the sensor test response has delay, the first ammonia coverage estimated value of cc-SCR is the ammonia coverage estimated value of the previous moment, and the first failure factor estimated value is the first failure factor estimated value of the previous moment, the real-time failure factor of cc-SCR is predicted by applying an unscented Kalman filter observer UKF, and the UKF is expressed as a nonlinear system consisting of a random variable X of Gaussian white noise W (k) and an observed variable Z of Gaussian white noise V (k):
the main and key processes of the UKF are Unscented (UT) transforms, from which 2n+1 sigma points and corresponding weights ω are calculated. Thus, the UKF basic steps for the random variable X in variable time k are as follows:
(1) Sigma Point set:
where P is the variance of the state vector X. X is X (i) Represents the ith Sigma point, defined as the following equation:
(2) One-step prediction of Sigma point set:
X (i) (k+1|k)＝f[k,X (i) (k|k)]i＝1～2n+1
(3) One-step prediction and covariance matrix of system state quantity:
wherein: ω represents the weight of the sampled sigma point and is defined as follows:
(4) New Sigma point set:
(5) Prediction of the observation equation:
Z (i) (k+1k)＝h[X (i) (k+1k)],i＝1,2,…,2n+1
(6) Mean and covariance of system predictions:
(7) Calculation of a Kalman gain matrix:
and taking the exhaust gas mass flow, the first bed temperature, the first NOx concentration, the second NOx concentration, the first supply signal, the first ammonia coverage estimation value and the first failure factor estimation value of the cc-SCR as inputs of an unscented Kalman filter observer UKF, and obtaining a third failure factor estimation value of the cc-SCR through iterative calculation to represent the real-time failure degree of the cc-SCR.
Whether the cc-SCR is in catalytic failure or not, the real-time failure degree of the cc-SCR can be represented by the third failure factor estimation value and used as one of the basis for confirming the occurrence time of the failure and the failure reason.
Step S40, obtaining the third temperature of the input end of the SCR and the fourth temperature of the output end of the ASC, determining the second bed temperature of the SCR, interpolating to obtain the second theoretical NOx conversion efficiency of the SCR, and determining the preset lower limit value of the second NOx conversion efficiency of the SCR according to the second preset efficiency factor.
Alternatively, the third temperature is determined by acquiring a signal of the third temperature sensor 113, and the fourth temperature is determined by acquiring a signal of the fourth temperature sensor 114.
FIG. 4 is a schematic diagram of determining whether and to what extent the SCR is deactivated, specifically, the second bed temperature is determined as follows: a third temperature and a corresponding third influence coefficient K 3 Multiplying the fourth temperature by the corresponding fourth influence coefficient K 4 Multiplying, adding the two multiplication results to obtain a second bed temperature of the SCR, i.e. second bed temperature=k 3 X third temperature +K 4 X fourth temperature, where K 3 +K 4 =1. For example: third influence coefficient K 3 Is 0.5, a fourth influence coefficient K 4 0.5, then the current temperature inside the scr=0.5×third temperature+0.5×thAnd four temperatures. If the influence degree of the third temperature on the current temperature in the SCR is smaller than that of the fourth temperature through experimental or simulation calculation and other modes, a third influence coefficient K can be set 3 Is 0.3, a fourth influence coefficient K 4 Is 0.7 or a third influence coefficient K 3 Is 0.4, a fourth influence coefficient K 4 0.6, etc.
More specifically, the SCR has a MAP of bed temperatures and theoretical NOx conversion efficiencies, and after determining the second bed temperature, the second theoretical NOx conversion efficiency of the SCR can be interpolated from the MAP. The second preset efficiency factor is a lower limit scale factor preset for the theoretical NOx conversion efficiency of the SCR at the current bed temperature, and in actual work, the value of the second preset efficiency factor is in the range of 0.9-1. Thus, multiplying the second preset efficiency factor by the second theoretical NOx conversion efficiency results in a lower NOx conversion efficiency limit for the SCR.
And S50, acquiring a second supply signal of the second reducing agent quantitative supply system and a third NOx concentration of an output end of the ASC, determining the actual NOx conversion efficiency of the SCR, and judging whether the actual NOx conversion efficiency of the SCR is lower than a lower limit of the NOx conversion efficiency of the SCR.
Optionally, the third NOx concentration is determined by collecting a signal of a third NOx sensor.
Specifically, the second NOx concentration is subtracted from the third NOx concentration to obtain a concentration difference, and the concentration difference is divided from the second NOx concentration to obtain the SCR actual NOx conversion efficiency, that is, SCR actual NOx conversion efficiency= (second NOx concentration-third NOx concentration)/second NOx concentration.
Judging the relation between the actual NOx conversion efficiency of the SCR and the lower limit of the NOx conversion efficiency of the SCR:
if the actual NOx conversion efficiency of the SCR is more than or equal to the lower limit of the NOx conversion efficiency of the SCR, judging that the SCR catalysis is normal;
if the actual NOx conversion efficiency of the SCR is less than the lower limit of the NOx conversion efficiency of the SCR, the SCR has the possibility of catalytic failure, and the SCR needs to be further judged through a second supply signal.
First, judging whether the ratio of the second reducing agent supply mass flow rate to the second NOx mass flow rate in the second supply signal accords with the stoichiometric ratio of the reaction dynamics, wherein the second NOx mass flow rate is the product of the second NOx concentration and the original machine emission mass flow rate. If the second reducing agent is not sufficiently supplied, a second supply signal of the ECU is regulated, and if the SCR actual NOx conversion efficiency of the regulated SCR is more than or equal to the NOx conversion efficiency lower limit of the SCR, the interference caused by a second reducing agent supply control strategy can be determined; if the second reducing agent is normally supplied, the relation between the actual NOx conversion efficiency of the SCR and the lower limit of the NOx conversion efficiency of the SCR is judged by repeatedly carrying out continuous 5 sampling points, the interference caused by accidental measurement errors is eliminated, and when the actual NOx conversion efficiency of the SCR at the continuous 5 sampling points is smaller than the lower limit of the NOx conversion efficiency of the SCR, the catalytic failure of the SCR is judged.
The second reducing agent dosing system includes a second supply pump, a second supply pipeline and a second nozzle, the second supply signal is a control signal sent by the electronic control unit ECU to the second reducing agent dosing system, and the signal content includes the time, the opening and closing degree and the duration of the reducing agent injection executed by the second nozzle. The second reductant dosing system may receive a second supply signal, pump the second reductant through a second supply line, deliver the second reductant through a second nozzle, and inject the second reductant into the aftertreatment exhaust flow through the second nozzle, and may determine a mass flow rate of the second reductant entering the SCR and a total amount of the second reductant injected based on the second supply signal. The second reductant includes urea.
Step S60, determining a failure degree of the SCR according to an exhaust gas mass flow, a second bed temperature, a second NOx concentration, a third NOx concentration, and the second supply signal.
Similarly, the determination of the SCR failure degree is the same as the method for determining the failure degree of cc-SCR described above, and will not be described in detail here.
And taking the exhaust gas mass flow, the second bed temperature, the second NOx concentration, the third NOx concentration, the second supply signal, the second ammonia coverage estimation value of the SCR and the second failure factor estimation value as inputs of an unscented Kalman filter observer UKF, and obtaining a fourth failure factor estimation value of the SCR through iterative calculation to represent the real-time failure degree of the SCR.
The embodiment of the application also provides a structural schematic diagram of the electronic equipment. As shown in fig. 5, the electronic device 200 includes one or more processors 201 and memory 202.
The processor 201 may be a Central Processing Unit (CPU) or other form of processing unit having data processing and/or instruction execution capabilities, and may control other components in the electronic device 200 to perform desired functions.
Memory 202 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and/or non-volatile memory. Volatile memory can include, for example, random Access Memory (RAM) and/or cache memory (cache) and the like. The non-volatile memory may include, for example, read Only Memory (ROM), hard disk, flash memory, and the like. One or more computer program instructions may be stored on a computer readable storage medium and the processor 201 may execute the program instructions to implement the fault diagnosis method and other desired functions of the dual SCR system of the embodiments of the present application described above. Various content such as initial arguments, thresholds, etc. may also be stored in the computer readable storage medium.
In one example, the electronic device 200 may further include: an input device 203 and an output device 204, which are interconnected by a bus system and/or other forms of connection mechanisms (not shown). The input device 203 may include, for example, a keyboard, a mouse, and the like. The output device 204 may output various information to the outside, including warning prompt information, braking force, etc. The output device 204 may include, for example, a display, speakers, a printer, and a communication network and remote output apparatus connected thereto, etc.
Of course, only some of the components of the electronic device 200 that are relevant to the present application are shown in fig. 5 for simplicity, components such as buses, input/output interfaces, etc. are omitted. In addition, the electronic device 200 may include any other suitable components depending on the particular application.
In addition to the methods and apparatus described above, embodiments of the application may also be a computer program product comprising computer program instructions which, when executed by a processor, cause the processor to perform the steps of the fault diagnosis method of the dual SCR system provided by any embodiment of the application.
The computer program product may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device, partly on a remote computing device, or entirely on the remote computing device or server.
In addition, the embodiment of the application also provides a computer readable storage medium, on which computer program instructions are stored, which when being executed by a processor, cause the processor to execute the steps of the fault diagnosis method of the dual SCR system provided by any embodiment of the application.
A computer readable storage medium may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium may include, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium would include the following: an electrical connection having one or more wires, a portable disk, a hard disk, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present application. As used in this specification, the terms "a," "an," "the," and/or "the" are not intended to be limiting, but rather are to be construed as covering the singular and the plural, unless the context clearly dictates otherwise. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method or apparatus comprising such elements.
It should also be noted that the positional or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the positional or positional relationship shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application. Unless specifically stated or limited otherwise, the terms "mounted," "connected," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present application.
Claims (10)
1. The fault diagnosis method of the double SCR system is applied to a series system consisting of a close-coupled selective catalytic reduction unit cc-SCR and an integrated aftertreatment device connected in series with the cc-SCR output end, wherein the integrated aftertreatment device consists of an oxidation catalytic converter DOC, a particle catcher DPF, a selective catalytic converter SCR and an ammonia slip converter ASC which are sequentially connected in series, and the input end of the cc-SCR is connected with an exhaust outlet of a diesel engine; the in-line system further includes a first reductant dosing system that performs reductant dosing at an input of the cc-SCR and a second reductant dosing system that performs reductant dosing at an input of the SCR; characterized in that the method comprises the following steps:
step S10, acquiring a first temperature of an input end of the cc-SCR and a second temperature of an input end of the DOC, determining a first bed temperature of the cc-SCR, interpolating to obtain a first theoretical NOx conversion efficiency of the cc-SCR, and determining a lower NOx conversion efficiency limit of the cc-SCR according to a first preset efficiency factor;
step S20, acquiring a first supply signal of the first reducing agent quantitative supply system, a first NOx concentration of an input end of the cc-SCR and a second NOx concentration of an input end of the DOC, determining the actual NOx conversion efficiency of the cc-SCR, and judging whether the actual NOx conversion efficiency of the cc-SCR is lower than the lower limit of the NOx conversion efficiency of the cc-SCR;
step S30, obtaining the exhaust mass flow of an exhaust outlet of the diesel engine, and determining the failure degree of the cc-SCR according to the exhaust mass flow, the first bed temperature, the first NOx concentration, the second NOx concentration and the first supply signal;
step S40, obtaining a third temperature of an input end of the SCR and a fourth temperature of an output end of the ASC, determining a second bed temperature of the SCR, interpolating to obtain a second theoretical NOx conversion efficiency of the SCR, and determining a lower limit of the NOx conversion efficiency of the SCR according to a second preset efficiency factor;
step S50, obtaining a second supply signal of the second reducing agent quantitative supply system and a third NOx concentration of the output end of the ASC, determining the actual NOx conversion efficiency of the SCR, and judging whether the actual NOx conversion efficiency of the SCR is lower than the lower limit of the NOx conversion efficiency of the SCR;
step S60, determining a failure degree of the SCR according to the exhaust gas mass flow, the second bed temperature, the second NOx concentration, the third NOx concentration, and the second supply signal.
2. The method according to claim 1, wherein in the step S10, the first bed temperature=k 1 X first temperature +K 2 X second temperature, where K 1 K being the coefficient of influence of the first temperature on the cc-SCR 2 K being the coefficient of influence of the second temperature on the cc-SCR 1 +K 2 ＝1；
In step S40, the second bed temperature=k 3 X third temperature +K 4 X fourth temperature, where K 3 K is the influence coefficient of the third temperature on the SCR 4 K is the influence coefficient of the fourth temperature on the SCR 3 +K 4 ＝1。
3. The method according to claim 1, wherein in the step S10, a first NOx conversion efficiency preset lower limit value=a first preset efficiency factor x a first theoretical NOx conversion efficiency, the first preset efficiency factor being a ratio of a lowest conversion efficiency allowed when the cc-SCR is operating normally to a theoretical conversion efficiency;
in the step S40, a second NOx conversion efficiency preset lower limit value=a second preset efficiency factor×a second theoretical NOx conversion efficiency, where the second preset efficiency factor is a ratio of the minimum conversion efficiency allowed when the SCR is working normally to the theoretical conversion efficiency.
4. The method of claim 1, wherein the first supply signal is used to determine whether the total amount of the first reductant entering the cc-SCR is sufficient, and if the first reductant is not sufficiently supplied, the first supply signal is adjusted to again determine whether the actual NOx conversion efficiency of the cc-SCR is less than the lower NOx conversion efficiency limit of the cc-SCR;
and judging whether the total amount of the second reducing agent entering the SCR is sufficient or not through the second supply signal, if the second reducing agent is not sufficiently supplied, adjusting the second supply signal, and then judging whether the actual NOx conversion efficiency of the SCR is lower than the lower limit of the NOx conversion efficiency of the SCR again.
5. The method according to claim 4, wherein the first reducing agent dosing system includes a first nozzle, the second reducing agent dosing system includes a second nozzle, and the first nozzle and the second nozzle are provided with an electronic control unit ECU;
the first supply signal in the step S20 is sent by the ECU to the first nozzle, including a reducing agent injection timing, an opening degree, and a duration;
the second supply signal in the step S40 is sent by the ECU to the second nozzle, including a reducing agent injection timing, an opening/closing degree, and a duration.
6. The method for diagnosing a fault in a dual SCR system as recited in claim 1, wherein if cc-SCR actual NOx conversion efficiency < cc-SCR lower NOx conversion efficiency limit, said cc-SCR actual NOx conversion efficiency is calculated a plurality of times, excluding error interference;
if the actual NOx conversion efficiency of the SCR is smaller than the lower limit of the NOx conversion efficiency of the SCR, calculating the actual NOx conversion efficiency of the cc-SCR for a plurality of times, and eliminating error interference.
7. The method for diagnosing a fault in a dual SCR system as defined in claim 6, wherein if cc-SCR actual NOx conversion efficiency is less than cc-SCR NOx conversion efficiency lower limit after a plurality of calculations, outputting fault information of cc-SCR catalytic failure;
and if the actual NOx conversion efficiency of the SCR is smaller than the lower limit of the NOx conversion efficiency of the SCR after multiple times of calculation, outputting fault information of SCR catalytic failure.
8. The method for diagnosing a fault in a dual SCR system as claimed in claim 1, wherein said step S30 comprises: using the exhaust gas mass flow, the first bed temperature, the first NOx concentration, the second NOx concentration and the first supply signal as inputs and utilizing a state balance equation of the cc-SCR, outputting a first ammonia coverage estimation value and a first failure factor estimation value of the cc-SCR, and obtaining a third failure factor estimation value through iteration, wherein the third failure factor estimation value can represent the failure degree of the cc-SCR;
the step S60 includes: and taking the exhaust gas mass flow, the second bed temperature, the second NOx concentration, the third NOx concentration and the second supply signal as inputs, utilizing a state balance equation of the SCR, outputting a second ammonia coverage degree estimated value and a second failure factor estimated value of the SCR, and obtaining a fourth failure factor estimated value through iteration, wherein the fourth failure factor estimated value can represent the failure degree of the SCR.
9. An electronic device, the electronic device comprising:
a processor and a memory;
the processor is configured to execute the steps of the fault diagnosis method of the dual SCR system according to any one of claims 1 to 8 by calling a program or instructions stored in the memory.
10. A computer-readable storage medium storing a program or instructions that cause a computer to execute the steps of the fault diagnosis method of the dual SCR system according to any one of claims 1 to 8.
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