Method for determining urea injection quantity, urea injection system and controller

Abstract

The application provides a method for determining urea injection amount, a urea injection system and a controller. The method comprises the following steps: obtaining a reaction temperature, the reaction temperature being a cavity temperature of a selective catalytic reduction device; determining a control mode of urea injection amount of the selective catalytic reduction device according to the reaction temperature, the control mode being a first control mode or a second control mode, the first control mode being a mode for determining the urea injection amount of a urea nozzle according to an ammonia concentration, the second control mode being a mode for determining the urea injection amount of the urea nozzle according to an ammonia adsorption amount in the selective catalytic reduction device, the ammonia concentration including an ammonia concentration downstream of the selective catalytic reduction device; and determining the urea injection amount of the urea nozzle according to the control mode. The method can more accurately determine the urea injection amount by adopting different control logics at different temperatures, and solves the problem that the prior art cannot completely prevent waste of a reducing agent or ammonia leakage to cause secondary pollution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of diesel engine exhaust treatment, in particular, relates to a method for determining urea injection amount, a urea injection system and a controller. BACKGROUND

[0002] During the operation of a diesel engine, nitrogen oxides are generated. In order to meet emission requirements, an SCR (Selective Catalystic Reduction) device is installed in the current diesel engine treatment system. By spraying urea solution to the catalyst installed in the exhaust management, the nitrogen oxides harmful to the environment are reduced to nitrogen, thereby reducing emissions and meeting emission requirements. However, in the existing technology, not only is there a problem of reductant waste, but also secondary pollution caused by ammonia leakage. SUMMARY

[0003] The main purpose of the present application is to provide a method for determining urea injection amount, a urea injection system and a controller, so as to solve the problem that the existing technology cannot completely prevent reductant waste or ammonia leakage causing secondary pollution.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a method for determining urea injection amount is provided. The method is applied to a controller in a urea injection system, the urea injection system further comprising a urea nozzle and a selective catalytic conversion device, the urea nozzle being upstream of the selective catalytic conversion device, the controller being in communication connection with the urea nozzle and the selective catalytic conversion device, the method comprising: obtaining a reaction temperature, the reaction temperature being a temperature in a cavity of the selective catalytic conversion device; determining a control mode of urea injection amount of the selective catalytic conversion device according to the reaction temperature, the control mode being a first control mode or a second control mode, the first control mode being a mode of determining urea injection amount of the urea nozzle according to ammonia concentration, the second control mode being a mode of determining urea injection amount of the urea nozzle according to ammonia adsorption amount in the selective catalytic conversion device, the ammonia concentration including ammonia concentration downstream of the selective catalytic conversion device; determining urea injection amount of the urea nozzle according to the control mode, wherein the urea injection amount includes first urea injection amount and second urea injection amount, the first urea injection amount being urea amount injected by the urea nozzle in a case that the urea nozzle is controlled by the first control mode, the second urea injection amount being urea amount injected by the urea nozzle in a case that the urea nozzle is controlled by the second control mode.

[0005] Optionally, the control mode of the urea injection amount of the selective catalytic reduction device is determined according to the reaction temperature, including: determining the control mode of the urea injection amount as the first control mode when the reaction temperature is greater than or equal to a preset temperature; determining the control mode of the urea injection amount as the second control mode when the reaction temperature is less than the preset temperature.

[0006] Optionally, the control mode is the first control mode, and the urea injection system further comprises a temperature sensor, a first nitrogen oxide sensor and an ammonia sensor, wherein the temperature sensor is located upstream of the urea nozzle, the first nitrogen oxide sensor is located upstream of the temperature sensor, and the ammonia sensor is located downstream of the selective catalytic reduction device; according to the control mode, the urea injection amount of the urea nozzle is determined, including: obtaining first related parameters, the first related parameters including: a first nitrogen oxide concentration, an exhaust gas flow, a first temperature, a first space velocity and a first ammonia concentration, wherein the first nitrogen oxide concentration is collected by the first nitrogen oxide sensor, the exhaust gas flow is the flow of generated exhaust gas, the first temperature is the temperature collected by the temperature sensor, the first space velocity is the space velocity of the selective catalytic reduction device, and the first ammonia concentration is collected by the ammonia sensor; and determining the urea injection amount of the urea nozzle according to the first related parameters.

[0007] Optionally, the urea injection amount of the urea nozzle is determined according to the first related parameters, including: determining a feedforward efficiency value according to the first space velocity and the first temperature, and correcting the feedforward efficiency value to obtain an actual efficiency value; determining the mass flow of ammonia according to the first nitrogen oxide concentration and the exhaust gas flow; and determining a first urea injection amount according to the mass flow of ammonia and the actual efficiency value, the first urea injection amount being the product of the mass flow of ammonia and the actual efficiency value.

[0008] Optionally, before the feedforward efficiency value is determined according to the first space velocity and the first temperature, and the actual efficiency value is corrected, the method further comprises: constructing a first model, the first model being used to represent the mapping relationship between the first space velocity, the first temperature, the ammonia concentration, the nitrogen oxide concentration and the feedforward efficiency value; determining a theoretical value of the ammonia concentration according to the first space velocity, the first temperature and the first model, the theoretical value of the ammonia concentration being the theoretical value of the ammonia concentration at the ammonia sensor; determining an ammonia concentration deviation value according to the theoretical value of the ammonia concentration and the first ammonia concentration, wherein the ammonia concentration deviation value is the difference between the theoretical value of the ammonia concentration and the first ammonia concentration; and correcting the ammonia concentration deviation value to obtain an efficiency correction value.

[0009] Optionally, the actual efficiency value is determined according to the first air speed and the first temperature, and the actual efficiency value is corrected from the feedforward efficiency value, including: determining the feedforward efficiency value according to the first air speed, the first temperature and the first model; determining the actual efficiency value according to the feedforward efficiency value and the efficiency correction value, wherein the actual efficiency value is the sum of the feedforward efficiency value and the efficiency correction value.

[0010] Optionally, the mass flow of the ammonia gas is determined according to the first nitrogen oxide concentration and the exhaust flow, including: determining a first mass flow of the nitrogen oxide according to the first nitrogen oxide concentration and the exhaust flow; obtaining a mass ratio of complete reaction of the nitrogen oxide and the ammonia gas; determining the mass flow of the ammonia gas required for complete reaction of the nitrogen oxide according to the first mass flow and the mass ratio.

[0011] Optionally, the control mode is the second control mode, and the urea injection system further comprises a temperature sensor, a second nitrogen oxide sensor and an ammonia sensor, wherein the temperature sensor is located upstream of the urea nozzle, the second nitrogen oxide sensor is located downstream of the selective catalytic reduction device, and the ammonia sensor is located between the selective catalytic reduction device and the second nitrogen oxide sensor; according to the control mode, the urea injection amount of the urea nozzle is determined, including: obtaining second related parameters, the second related parameters including: a second nitrogen oxide concentration, a second temperature, a second air speed and a second ammonia concentration, wherein the second nitrogen oxide concentration is collected by the second nitrogen oxide sensor, the second temperature is the temperature collected by the temperature sensor, the second air speed is the air speed of the selective catalytic reduction device, and the second ammonia concentration is collected by the ammonia sensor; determining the urea injection amount of the urea nozzle according to the second related parameters.

[0012] Optionally, in the process of determining the urea injection amount of the urea nozzle according to the second related parameters, the method further comprises: obtaining a current ammonia adsorption amount in the selective catalytic reduction device; constructing a second model, the second model being used to represent a mapping relationship between a second air speed, a second temperature, a theoretical value of nitrogen oxide and a predetermined ammonia adsorption amount of the selective catalytic reduction device, wherein the theoretical value of the nitrogen oxide is a theoretical value of the concentration of the nitrogen oxide at the second nitrogen oxide sensor; determining the predetermined ammonia adsorption amount according to the second air speed, the second temperature and the second model; determining an ammonia adsorption amount deviation value according to the predetermined ammonia adsorption amount and the current ammonia adsorption amount, wherein the ammonia adsorption amount deviation value is the difference between the predetermined ammonia adsorption amount and the current ammonia adsorption amount.

[0013] Optionally, in the process of determining the urea injection amount of the urea nozzle according to the second related parameters, the method further comprises: determining a theoretical value of the nitrogen oxide according to the second space velocity, the second temperature and the second model; and determining a nitrogen oxide concentration deviation value according to the theoretical value of the nitrogen oxide and the second nitrogen oxide concentration, wherein the nitrogen oxide concentration deviation value is a difference between the theoretical value of the nitrogen oxide and the second nitrogen oxide concentration.

[0014] Optionally, in the process of determining the urea injection amount of the urea nozzle according to the second related parameters, the method further comprises: obtaining a correlation coefficient of the nitrogen oxide and the ammonia sensor; determining a proportional adjustment coefficient of the predetermined ammonia adsorption amount and the current ammonia adsorption amount according to the nitrogen oxide concentration deviation value; and determining a model closed-loop correction efficiency value according to the nitrogen oxide concentration deviation value, the proportional adjustment coefficient and the correlation coefficient.

[0015] Optionally, in the process of determining the urea injection amount of the urea nozzle according to the second related parameters, the method further comprises: determining a correlation factor coefficient according to a correlation between the second ammonia concentration and the second nitrogen oxide concentration; determining a correction efficiency coefficient according to the correlation factor coefficient, the model closed-loop correction efficiency value and the ammonia adsorption amount deviation value, wherein the correction efficiency coefficient is a sum of a product of the correlation factor coefficient and the model closed-loop correction efficiency value and the ammonia adsorption amount deviation value; and determining a second urea injection amount according to the correction efficiency coefficient and a mass flow rate of the ammonia, wherein the mass flow rate of the ammonia is a mass flow rate of the ammonia required for complete reaction of the nitrogen oxide, and the second urea injection amount is a product of the correction efficiency coefficient and the mass flow rate of the ammonia.

[0016] According to another aspect of the present application, there is provided a urea injection system, comprising: a urea nozzle for injecting urea; a selective catalytic reduction device for catalytic reaction, the selective catalytic reduction device being located downstream of the urea nozzle; and a controller in communication with the urea nozzle and the selective catalytic reduction device, for executing any of the determination methods.

[0017] Optionally, the system further comprises: a temperature sensor located upstream of the urea nozzle; a first nitrogen oxide sensor located upstream of the temperature sensor; a second nitrogen oxide sensor located downstream of the selective catalytic reduction device; and an ammonia sensor located between the selective catalytic reduction device and the second nitrogen oxide sensor.

[0018] According to another aspect of the present application, a controller is provided, which is arranged in a urea injection system further comprising a urea nozzle upstream of a selective catalytic reduction device and the controller is communicatively connected with the urea nozzle and the selective catalytic reduction device, the controller comprising: an acquisition unit configured to acquire a reaction temperature, wherein the reaction temperature is a temperature in a cavity of the selective catalytic reduction device; a first determination unit configured to determine a control mode of a urea injection amount of the selective catalytic reduction device according to the reaction temperature, wherein the control mode is a first control mode or a second control mode, the first control mode is a mode of determining the urea injection amount of the urea nozzle according to an ammonia concentration, and the second control mode is a mode of determining the urea injection amount of the urea nozzle according to an ammonia adsorption amount in the selective catalytic reduction device, and the ammonia concentration includes an ammonia concentration downstream of the selective catalytic reduction device; and a second determination unit configured to determine the urea injection amount of the urea nozzle according to the control mode, wherein the urea injection amount includes a first urea injection amount and a second urea injection amount, the first urea injection amount is a urea amount injected by the urea nozzle in a case that the urea nozzle is controlled by the first control mode, and the second urea injection amount is a urea amount injected by the urea nozzle in a case that the urea nozzle is controlled by the second control mode.

[0019] The application discloses a method for determining urea injection quantity. BRIEF DESCRIPTION OF DRAWINGS

[0020] The drawings constituting a part of the specification of the application are used to provide further understanding of the application, the illustrative embodiments of the application and the description thereof are used to explain the application, and do not constitute improper limitation on the application. In the drawings:

[0021] Figure 1 A flowchart of a method for determining urea injection quantity according to an embodiment of the application is shown;

[0022] Figure 2 A structural schematic diagram of a urea injection system according to an embodiment of the application is shown;

[0023] Figure 3 A flowchart of a first control mode according to an embodiment of the application is shown;

[0024] Figure 4 A flowchart of a second control mode according to an embodiment of the application is shown;

[0025] Figure 5 A schematic diagram of a controller according to an embodiment of the application is shown.

[0026] wherein the above figures include the following reference signs:

[0027] 10: urea nozzle; 11: selective catalytic converter; 12: first nitrogen oxide sensor; 13: first temperature sensor; 14: ammonia sensor; 15: second nitrogen oxide sensor; 16: first agitator; 17: first ammonia slip catcher; 20: second urea nozzle; 21: second selective catalytic converter; 22: third nitrogen oxide sensor; 23: second agitator; 24: second temperature sensor; 25: second ammonia slip catcher; 26: oxidation catalyst; 27: third temperature sensor; 28: particulate matter catcher. DETAILED DESCRIPTION

[0028] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0029] In order to enable persons skilled in the art to better understand the scheme of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0030] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0031] It should be understood that when an element (such as a layer, film, region, or substrate) is described as "on" another element, it can be directly on the other element, or there can be an intermediate element. Also, in the specification and claims, when an element is described as "connected" to another element, it can be "directly connected" to the other element, or "connected" to the other element through a third element.

[0032] For the convenience of description, the following describes some nouns or terms related to the embodiments of the present application:

[0033] selective catalytic reduction device (equivalent to selective catalytic reduction device): post-SCR (abbreviation: posSCR), urea is injected after the second selective catalytic reduction device to reduce nitrogen oxides in exhaust emissions, and the second selective catalytic reduction device is located at a first distance from the turbine of the system;

[0034] second selective catalytic reduction device: pre-SCR (abbreviation: preSCR), urea is injected before the selective catalytic reduction device to reduce nitrogen oxides in exhaust emissions, and the selective catalytic reduction device is located at a second distance from the turbine of the system, and the first distance is greater than the second distance;

[0035] particulate filter (abbreviation: DPF), used for trapping particulate matter in exhaust gas, when the trapped particulate matter reaches a certain level, passive regeneration or active regeneration is required to restore the particulate trapping ability of the particulate filter, which mainly filters and traps the particulate matter in the engine exhaust through diffusion, deposition and impact mechanism. When the exhaust gas flows through the trap, the particulate matter is trapped in the filter core of the filter body, and the remaining relatively clean exhaust gas is discharged into the atmosphere. At present, the wall-flow honeycomb ceramic filter is more commonly used, which is mainly used for engineering machinery and city buses, and has the characteristics of simple operation and high filtration efficiency, but has the problems of filter regeneration and sensitivity to sulfur content in fuel;

[0036] oxidation catalyst (abbreviation: DOC), used for converting NO (nitric oxide) in exhaust gas to NO2 (nitrogen dioxide), while increasing the temperature of the exhaust gas to assist the normal operation of the particulate filter and the selective catalytic reduction device, which is a honeycomb ceramic carrier coated with noble metal catalyst (such as Pt, etc.), the purpose is to reduce the chemical reaction activation energy of HC, CO and SOF in engine exhaust, so that these substances can oxidize with oxygen in the exhaust gas at a lower temperature and eventually convert to CO2 and H2O. Oxidation catalyst does not require a regeneration system and control device, has the characteristics of simple structure and good reliability, and has been applied to some modern small engines;

[0037] ammonia slip catalyst (abbreviation: ASC), used for oxidizing excess ammonia gas;

[0038] The basic working principle of the particulate trap is that when the engine exhaust gas flows through the oxidation catalyst (DOC), CO and HC are first almost completely oxidized to CO2 and H2O, and NO is converted to NO2 at a temperature of 200-600°C. The exhaust gas from the DOC enters the particulate trap (DPF), where the particulate is trapped in the filter core, and the remaining relatively clean exhaust gas is discharged into the atmosphere. The trapping efficiency of the DPF can be over 90%.

[0039] NO2 has strong oxidizing ability for the trapped particulate, and the generated NO2 is used as an oxidizing agent to remove the particulate in the particulate trap and generate CO2, and the NO2 is reduced to NO, thereby achieving the purpose of removing the particulate.

[0040] Reaction principle in the DOC:

[0041] 2NO + O2 → 2NO2

[0042] 2CO + O2 → 2CO2

[0043] 2CH + O2 → CO2 + H2O

[0044] Reaction principle in the DPF:

[0045] C + 2NO2 → CO2 + 2NO

[0046] There are two methods for regenerating the filter: active regeneration and passive regeneration. Active regeneration refers to using external energy to increase the temperature in the trap to make the particulate ignite and burn. When the temperature in the filter reaches 550°C, the deposited particulate will oxidize and burn. If the temperature does not reach 550°C, excessive deposits will clog the filter, and an external energy source (such as an electric heater, a burner, or a change in engine operating conditions) is needed to increase the temperature in the DPF to make the particulate oxidize and burn. Passive regeneration refers to using fuel additives or catalysts to lower the ignition temperature of the particulate so that the particulate can ignite and burn at normal engine exhaust gas temperature. The additive (with cerium, iron, and strontium) is added to the fuel in a certain proportion. Adding too much additive has little effect, but adding too little additive will cause regeneration delay or increase the regeneration temperature.

[0047] The basic principle of SCR is to inject fuel or add reductant into exhaust gas, and use suitable catalyst to promote the reaction between reductant and NOx, while inhibiting the non-selective oxidation reaction between reductant and oxygen. Commonly used urea-SCR catalysts include V2O5 / W2O3 / TiO2 and metal oxide / zeolite. Vanadium-based catalysts have high selectivity to NOx and a wide high-efficiency temperature window, and have high sulfur resistance, but are prone to be poisoned by phosphorus components in lubricating oil and high-temperature failure; zeolite-type catalysts have strong adsorption capacity for NH3, but the adsorption capacity of zeolite for HC is also strong at low temperature, and the adsorption of HC will affect the low-temperature performance of the catalyst, and the hydrothermal stability and sulfur resistance of zeolite are poor, so its actual use is limited, and low-sulfur fuel is required.

[0048] Sulfur oxides form sulfates in copper-based SCR, reducing the active sites of the catalyst, plugging the small pores, and reducing the conversion efficiency of SCR for NOx, so when a certain amount of sulfur oxides is trapped in the SCR, it needs to be desulfurized. There are two mechanisms of sulfur poisoning: the formation of (NH4)SO4, etc., which reduces the active sites of the SCR catalyst and blocks the small pores, thereby reducing the conversion efficiency of NOx; SO2 and SO3 compete with NO x for adsorption, reducing the adsorption of NO x ;

[0049] Reaction principle of SCR technology:

[0050] Urea is hydrolyzed to ammonia: (urea injection system)

[0051] (NH2)2CO + H2O → 2NH3 + CO2

[0052] SCR aftertreatment reaction: (SCR catalytic converter)

[0053] NO + NO2 + 2NH3 → 2N2 + 3H2O

[0054] 4NO + O2 + 4NH3 → 4N2 + 6H2O

[0055] 2NO2 + O2 + 4NH3 → 3N2 + 6H2O

[0056] The actual reducing agent participating in the selective catalytic reduction reaction in SCR is ammonia (NH3), but due to the high corrosiveness of ammonia, liquid ammonia and ammonia water have difficulties in storage and transportation, and therefore cannot be directly used in vehicle-mounted SCR systems. Currently, urea aqueous solution is generally used as the reducing agent. Since compared with other concentrations of urea aqueous solution, urea aqueous solution with a concentration of 32.5% has the lowest freezing point of -11°C, 32.5% urea aqueous solution is universally used as the standard reducing agent for SCR, and is named AdBlue.

[0057] As introduced in the background, not only the problem of reducing agent waste exists in the prior art, but also secondary pollution caused by ammonia leakage, and the posSCR catalyst chemical reaction in the prior art varies obviously with temperature, at low temperature, the catalyst can adsorb a large amount of NH3, form adsorbed NH3, and be used for chemical reaction, the reaction rate is seriously affected by the adsorbed NH3, the NOx and NH3 emissions after posSCR are obviously related to the current ammonia adsorption amount, and are not obviously related to the upstream NOx concentration, and the change delay of upstream and downstream NOx and NH3 is large; at medium and high temperature, due to the enhancement of desorption reaction, the adsorption amount is greatly reduced, the reaction rate is obviously enhanced with the increase of temperature, the NOx and NH3 emissions after posSCR are obviously related to the upstream NOx and NH3 concentration, and the change delay of upstream and downstream NOx and NH3 is weakened. In order to solve the problem that the reducing agent waste or ammonia leakage caused secondary pollution cannot be completely prevented in the prior art, the embodiments of the present application provide a method for determining urea injection amount, a urea injection system and a controller.

[0058] According to the embodiments of the present application, a method for determining urea injection amount is provided, which is applied to a controller in a urea injection system, as shown in Figure 2 The urea injection system further comprises a urea nozzle 10 and a selective catalytic conversion device 11, the first urea nozzle 10 is upstream of the selective catalytic conversion device 11, and the controller is in communication connection with the urea nozzle 10 and the selective catalytic conversion device 11.

[0059] The selective catalytic conversion device of the present application is posSCR, in the prior art, the posSCR catalyst chemical reaction varies obviously with temperature, at low temperature, the catalyst can adsorb a large amount of NH3, form adsorbed NH3, and be used for chemical reaction, the reaction rate is seriously affected by the adsorbed NH3, the NOx (nitrogen oxide) and NH3 emissions after posSCR are obviously related to the current ammonia adsorption amount, and are not obviously related to the upstream NOx concentration, and the change delay of upstream and downstream NOx and NH3 is large; at medium and high temperature, due to the enhancement of desorption reaction, the adsorption amount is greatly reduced, the reaction rate is obviously enhanced with the increase of temperature, the NOx and NH3 emissions after posSCR are obviously related to the upstream NOx and NH3 concentration, and the change delay of upstream and downstream NOx and NH3 is weakened.

[0060] Figure 1 The flowchart of the method for determining urea injection amount according to the embodiments of the present application is shown in Figure 1 The method comprises the following steps:

[0061] In step S101, the reaction temperature is obtained, the reaction temperature is the temperature in the cavity of the selective catalytic conversion device;

[0062] Step S102, determining the control mode of the urea injection amount of the selective catalytic reduction device according to the reaction temperature, the control mode being a first control mode or a second control mode, the first control mode being a mode of determining the urea injection amount of the urea injector according to the ammonia concentration, the second control mode being a mode of determining the urea injection amount of the urea injector according to the ammonia adsorption amount in the selective catalytic reduction device, the ammonia concentration including the ammonia concentration downstream of the selective catalytic reduction device;

[0063] Since the SCR catalyst chemical reaction varies significantly with temperature, in order to avoid the influence of temperature on the catalytic reaction and NH3 emission, the step S102 further includes:

[0064] Step S1021, in the case that the reaction temperature is greater than or equal to a preset temperature, determining the control mode of the urea injection amount to be the first control mode;

[0065] Step S1022, in the case that the reaction temperature is less than the preset temperature, determining the control mode of the urea injection amount to be the second control mode.

[0066] Specifically, the preset temperature can be set at 300°C or above, which can be calibrated.

[0067] Step S103, determining the urea injection amount of the urea injector according to the control mode, wherein the urea injection amount includes a first urea injection amount and a second urea injection amount, the first urea injection amount being the urea amount injected by the urea injector in the case of controlling the urea injector by the first control mode, the second urea injection amount being the urea amount injected by the urea injector in the case of controlling the urea injector by the second control mode.

[0068] Wherein, the control mode is the first control mode, as shown in Figure 2 The urea injection system further includes a first temperature sensor 13 (temperature sensor), a first nitrogen oxygen sensor 12 and an ammonia sensor 14, wherein the first temperature sensor 13 is located upstream of the urea injector 10, the first nitrogen oxygen sensor 12 is located upstream of the first temperature sensor 13, and the ammonia sensor 14 is located downstream of the selective catalytic reduction device 11, and the step of determining the urea injection amount of the urea injector 10 according to the control mode is as follows:

[0069] Step S201, obtaining a first related parameter, the first related parameter including: a first nitrogen oxide concentration, an exhaust flow, a first temperature, a first space velocity and a first ammonia concentration, wherein the first nitrogen oxide concentration is collected by the first nitrogen oxide sensor, the exhaust flow is the flow of the generated exhaust gas, the first temperature is the temperature collected by the temperature sensor, the first space velocity is the space velocity of the selective catalytic reduction device, and the first ammonia concentration is collected by the ammonia sensor; specifically, the exhaust flow is the exhaust flow generated by the engine.

[0070] Step S202, determining the urea injection amount of the urea nozzle according to the first related parameter.

[0071] Since the reaction of the catalyst at medium and high temperatures only requires a small amount of ammonia adsorption, the ammonia sensor can be directly used for closed-loop control, the downstream NOx value is used for correction, there is no cross-sensitivity and the response is fast; the first control mode is actually a closed-loop control strategy based on NH3.

[0072] The specific implementation steps of step S202 are as follows:

[0073] Step S2021, determining a feedforward efficiency value according to the first space velocity and the first temperature, and correcting the feedforward efficiency value to obtain an actual efficiency value;

[0074] Step S2022, determining the mass flow of the ammonia according to the first nitrogen oxide concentration and the exhaust flow;

[0075] Step S2023, determining a first urea injection amount according to the mass flow of the ammonia and the actual efficiency value, the first urea injection amount being the product of the mass flow of the ammonia and the actual efficiency value.

[0076] Specifically, before determining the feedforward efficiency value according to the first space velocity and the first temperature, and correcting the feedforward efficiency value to obtain the actual efficiency value, the method further includes: constructing a first model, the first model being used to represent the mapping relationship between the first space velocity, the first temperature, the concentration of the ammonia and the concentration of the nitrogen oxide; determining a theoretical value of the ammonia concentration according to the first space velocity, the first temperature and the first model, the theoretical value of the ammonia concentration being the theoretical value of the concentration of the ammonia at the ammonia sensor; determining an ammonia concentration deviation value according to the theoretical value of the ammonia concentration and the first ammonia concentration, wherein the ammonia concentration deviation value is the difference between the theoretical value of the ammonia concentration and the first ammonia concentration; correcting the ammonia concentration deviation value to obtain an efficiency correction value.

[0077] The mapping relationship between the parameters in the first model can be obtained by searching the MAP, and the efficiency correction value is obtained by using a PI controller closed-loop regulation to correct the ammonia concentration deviation value.

[0078] To accurately obtain the actual efficiency value, the feedforward efficiency value is determined according to the first space velocity and the first temperature, and the actual efficiency value is obtained by correcting the feedforward efficiency value, including: determining the feedforward efficiency value according to the first space velocity, the first temperature and the first model; determining the actual efficiency value according to the feedforward efficiency value and the efficiency correction value, wherein the actual efficiency value is the sum of the feedforward efficiency value and the efficiency correction value.

[0079] Specifically, the mass flow rate of ammonia is determined according to the first nitrogen oxide concentration and the exhaust gas flow rate, including: determining the first mass flow rate of nitrogen oxide according to the first nitrogen oxide concentration and the exhaust gas flow rate; obtaining the mass ratio of complete reaction of the nitrogen oxide and the ammonia; determining the mass flow rate of ammonia required for complete reaction of the nitrogen oxide according to the first mass flow rate and the mass ratio. Wherein the mass ratio of complete reaction of the nitrogen oxide and the ammonia can be 0.37; the specific calculation method of calculating the first mass flow rate of nitrogen oxide according to the first nitrogen oxide concentration and the exhaust gas flow rate is shown in formula 1, and the specific calculation method of calculating the mass flow rate of ammonia required for complete reaction of the nitrogen oxide according to the first mass flow rate and the mass ratio is shown in formula 2:

[0080]

[0081] Q = Conc NOx × η × ANR × M Exh × C 常量 (Formula 2)

[0082] Wherein a is the first mass flow rate of nitrogen oxide, unit: kg / h; NO x is the first nitrogen oxide concentration, unit: ppm; dmEG is the exhaust gas flow rate, unit: kg / h. Q is the mass flow rate of ammonia required for complete reaction of the nitrogen oxide, η is the actual conversion rate, ANR is the theoretical volume ratio of nitrogen oxide completely converted (1:1), M Exh is the exhaust gas flow rate, C 常量 is set according to other coefficients of the above formula. Wherein dmEG and M Exh are both exhaust gas flow rates, and M Exh includes the first mass flow rate of nitrogen oxide, and M ExhThe first mass flow rate can also be used to calculate the ANR, which can be calculated from the mass ratio of the nitrogen oxide and the ammonia gas.

[0083] Specifically, the specific implementation of determining the urea injection amount of the urea nozzle according to the first control mode is as shown in the following formula (1) : Figure 3 As shown in the formula (1), the first space velocity and the first temperature are input into the first model to obtain an ammonia gas concentration theoretical value and a feedforward efficiency value, the first ammonia gas concentration is subtracted from the ammonia gas concentration theoretical value to obtain an ammonia gas concentration deviation value, the ammonia gas concentration deviation value is input into a PI controller to calculate an efficiency correction value, and the feedforward efficiency value and the efficiency correction value are added to obtain an actual efficiency value; the ammonia gas mass flow rate is obtained from the first nitrogen oxide concentration, the first mass flow rate, and the mass ratio of the nitrogen oxide and the ammonia gas, and the first urea injection amount is obtained by multiplying the ammonia gas mass flow rate and the actual efficiency value.

[0084] The control mode is the second control mode, as shown in the following formula (2) : Figure 2 As shown in the formula (2), the urea injection system further comprises a first temperature sensor 13, a second nitrogen oxide sensor 15, and an ammonia gas sensor 14, wherein the first temperature sensor 13 is located upstream of the urea nozzle 10, the second nitrogen oxide sensor 15 is located downstream of the selective catalytic reduction device 11, and the ammonia gas sensor 14 is located between the selective catalytic reduction device 11 and the second nitrogen oxide sensor 15; according to the control mode, the steps of determining the urea injection amount of the urea nozzle 10 are as follows:

[0085] In step 301, the second related parameters are obtained, and the second related parameters include a second nitrogen oxide concentration, a second temperature, a second space velocity, and a second ammonia gas concentration, wherein the second nitrogen oxide concentration is collected by the second nitrogen oxide sensor, the second temperature is collected by the temperature sensor, the second space velocity is the space velocity of the selective catalytic reduction device, and the second ammonia gas concentration is collected by the ammonia gas sensor.

[0086] In step 302, the urea injection amount of the urea nozzle is determined according to the second related parameters.

[0087] Since the catalyst has a large ammonia gas adsorption capacity at low temperature, the efficiency can be corrected using the correlation between the NH3 and NOx sensors based on the ammonia gas adsorption amount (ammonia storage) closed-loop control. The second control mode is actually a closed-loop control strategy based on ammonia storage.

[0088] The specific implementation steps of step 302 are as follows:

[0089] In step 3021, the current ammonia gas adsorption amount in the selective catalytic reduction device is obtained.

[0090] Step 3022, a second model is constructed to represent a mapping relationship between the second air speed, the second temperature, a theoretical value of the nitrogen oxide compound and a predetermined ammonia adsorption amount of the selective catalytic reduction device, wherein the theoretical value of the nitrogen oxide compound is a theoretical value of the concentration of the nitrogen oxide compound at the second nitrogen oxide sensor;

[0091] Step 3023, the predetermined ammonia adsorption amount is determined according to the second air speed, the second temperature and the second model; and an ammonia adsorption amount deviation value is determined according to the predetermined ammonia adsorption amount and the current ammonia adsorption amount, wherein the ammonia adsorption amount deviation value is a difference between the predetermined ammonia adsorption amount and the current ammonia adsorption amount.

[0092] The mapping relationship between the parameters in the second model can be obtained by looking up a MAP, the second air speed can be the same as the first air speed, and the second temperature can be the same as the first temperature.

[0093] Step 3024, the theoretical value of the nitrogen oxide compound is determined according to the second air speed, the second temperature and the second model; and a nitrogen oxide concentration deviation value is determined according to the theoretical value of the nitrogen oxide compound and the second nitrogen oxide concentration, wherein the nitrogen oxide concentration deviation value is a difference between the theoretical value of the nitrogen oxide compound and the second nitrogen oxide concentration. The nitrogen oxide concentration deviation value is used to calculate a proportional adjustment coefficient.

[0094] Step 3025, a correlation coefficient of the nitrogen oxide compound and the ammonia sensor is obtained; a proportional adjustment coefficient of the predetermined ammonia storage amount and the current ammonia storage amount is determined according to the ammonia storage amount deviation value; and a model closed-loop correction efficiency value is determined according to the ammonia storage amount deviation value, the proportional adjustment coefficient and the correlation coefficient. Specifically, the proportional adjustment coefficient of the current ammonia storage amount is calculated by PI control according to the ammonia storage amount deviation value, and the coefficient value of the model closed-loop correction efficiency value is determined by multiplying the ammonia storage amount deviation value and the proportional adjustment coefficient.

[0095] Step 3026: Based on the correlation between the second ammonia concentration and the second nitrogen oxide concentration, determine the correlation factor coefficient; based on the correlation factor coefficient, the model closed-loop correction efficiency value, and the ammonia storage deviation value, determine the correction efficiency coefficient, wherein the correction efficiency coefficient is the sum of the product of the correlation factor coefficient and the model closed-loop correction efficiency value and the ammonia storage deviation value; based on the correction efficiency coefficient and the ammonia mass flow rate, determine the second urea injection rate, wherein the ammonia mass flow rate is the mass flow rate of ammonia required to completely react with the nitrogen oxides, and the second urea injection rate is the product of the correction efficiency coefficient and the ammonia mass flow rate. Specifically, the correlation factor coefficient is used to determine whether the second nitrogen oxide sensor contains a correction factor for NH3 leakage, thereby controlling the direction and value of the model closed loop. For example, when the correlation factor is between 0.5 and 1, it indicates that the second nitrogen oxide sensor measurement contains NH3. As the correlation factor increases, the correlation factor coefficient control value decreases. When a certain value is reached, the correction value becomes negative. When the correlation factor is between 0 and 0.5, it indicates that the second nitrogen oxide sensor does not contain NH3. As the correlation factor decreases, the control value of the correlation factor coefficient can be increased. The specific analysis process for obtaining the correlation factor coefficient based on the correlation analysis of the second ammonia concentration and the second nitrogen oxide concentration is as follows: First, calculate the change in the ratio of the NH3 feedforward concentration to the actual injection concentration and the change in the upstream and downstream NOx ratio, and then calculate the correlation according to Formula 3.

[0096]

[0097] Where cov(X,Y) is the covariance of X and Y, and σ X Let σ be the standard deviation of X. Y Let X be the standard deviation of Y, X be the second ammonia concentration, and Y be the second nitrogen oxide concentration.

[0098] Specifically, the specific implementation method for determining the urea injection volume of the urea nozzle according to the second control mode is as follows: Figure 4 As shown, the second air velocity and the second temperature are input into the second model to obtain the predetermined ammonia adsorption amount. The difference between the current ammonia adsorption amount and the predetermined ammonia adsorption amount is used to obtain the ammonia adsorption deviation value. The correlation coefficient between the second ammonia concentration and the second nitrogen oxide concentration is calculated to obtain the correlation factor coefficient. The closed-loop correction efficiency value of the model is determined based on the proportional adjustment coefficient, the correlation coefficient, and the difference between the theoretical value of nitrogen oxides and the second nitrogen oxide concentration. The correction efficiency coefficient is obtained by summing the product of the correlation factor coefficient and the closed-loop correction efficiency value with the ammonia adsorption deviation value. Finally, the second urea injection amount is obtained by multiplying the ammonia mass flow rate and the correction efficiency coefficient.

[0099] The method for determining the urea injection amount of the present application is applied to a controller in a urea injection system, the urea injection system further comprising a urea nozzle upstream of a selective catalytic reduction device, the controller being communicatively connected to the urea nozzle and the selective catalytic reduction device, first obtaining a reaction temperature, the reaction temperature being the temperature in the cavity of the selective catalytic reduction device; then determining a control mode of the urea injection amount of the selective catalytic reduction device according to the reaction temperature, the control mode being a first control mode or a second control mode, the first control mode being a mode of determining the urea injection amount of the urea nozzle according to the ammonia concentration, the second control mode being a mode of determining the urea injection amount of the urea nozzle according to the ammonia adsorption amount in the selective catalytic reduction device, the ammonia concentration including the ammonia concentration downstream of the selective catalytic reduction device; and finally determining the urea injection amount of the urea nozzle according to the control mode, wherein the urea injection amount includes a first urea injection amount and a second urea injection amount, the first urea injection amount being the urea amount injected by the urea nozzle in the case of controlling the urea nozzle by the first control mode, and the second urea injection amount being the urea amount injected by the urea nozzle in the case of controlling the urea nozzle by the second control mode. The method considers different factors affecting the reaction rate at different temperatures by using different control logics at different temperatures, more accurately determines the urea injection amount, and solves the problem of not being able to completely prevent the waste of reducing agent or ammonia leakage to cause secondary pollution in the prior art.

[0100] Embodiments of the present application provide a urea injection system, as shown in Figure 2 including a urea nozzle 10 for injecting urea, a selective catalytic reduction device 11 for catalytic reaction, the selective catalytic reduction device 11 being downstream of the urea nozzle 10, and a controller communicatively connected to the urea nozzle 10 and the selective catalytic reduction device 11 for executing any of the above determination methods.

[0101] In one aspect, as shown in Figure 2 the system further comprises a first temperature sensor 13 upstream of the urea nozzle 10, a first nitrogen oxygen sensor 12 upstream of the first temperature sensor 13, a second nitrogen oxygen sensor 15 downstream of the selective catalytic reduction device 11, and an ammonia sensor 14 between the selective catalytic reduction device 11 and the second nitrogen oxygen sensor 15.

[0102] Exemplarily, as shown in Figure 2As shown, the urea injection system further comprises a third nitrogen oxygen sensor 22, a second urea nozzle 20, a second agitator 23, a second temperature sensor 24, a second selective catalytic reduction device 21, a second ammonia slip catcher 25, an oxidation catalyst 26, a third temperature sensor 27, and a particulate matter catcher 28 arranged in sequence from upstream to downstream. The second selective catalytic reduction device is a pre-SCR. The pre-SCR is controlled in an open loop mode. The NOx mass flow is calculated according to the NOx concentration measured by the third nitrogen oxygen sensor upstream and the exhaust gas flow. The NH3 mass flow required for the complete reaction of the upstream NOx is calculated according to the required NOx to NH3 mass ratio (e.g. 0.37) for the reaction. Meanwhile, the required efficiency under different working conditions is determined according to the space velocity and temperature of the pre-SCR by looking up a MAP, multiplied by the NH3 mass flow, to calculate the final NH3 injection amount, which is converted into the urea injection amount to drive the second urea nozzle control.

[0103] Specifically, as shown, Figure 2 The urea injection system further comprises a first agitator 16 and a first ammonia slip catcher 17. The first agitator is arranged between the urea nozzle 10 and the selective catalytic reduction device 11. The first ammonia slip catcher is arranged between the ammonia sensor 14 and the second nitrogen oxygen sensor 15.

[0104] The urea injection system of the present application comprises a urea nozzle for injecting urea; a selective catalytic conversion device for catalytic reaction, which is located downstream of the urea nozzle; and a controller, which is in communication with the urea nozzle and the selective catalytic conversion device, for performing any of the above methods by obtaining a reaction temperature, which is the temperature in the cavity of the selective catalytic conversion device; then determining a control mode of the urea injection amount of the selective catalytic conversion device according to the reaction temperature, wherein the control mode is a first control mode or a second control mode, the first control mode is a mode for determining the urea injection amount of the urea nozzle according to the ammonia concentration, and the second control mode is a mode for determining the urea injection amount of the urea nozzle according to the ammonia adsorption amount in the selective catalytic conversion device, wherein the ammonia concentration includes the ammonia concentration downstream of the selective catalytic conversion device; and finally determining the urea injection amount of the urea nozzle according to the control mode, wherein the urea injection amount includes a first urea injection amount and a second urea injection amount, the first urea injection amount is the urea amount injected by the urea nozzle when the urea nozzle is controlled by the first control mode, and the second urea injection amount is the urea amount injected by the urea nozzle when the urea nozzle is controlled by the second control mode. The system considers different factors that affect the reaction rate at different temperatures by using different control logics at different temperatures, and more accurately determines the urea injection amount, so as to solve the problem that the existing technology cannot completely prevent the waste of reducing agent or the leakage of ammonia to cause secondary pollution.

[0105] According to embodiments of the present application, a controller is provided, such as Figure 5As shown in the figure, the controller is arranged in a urea injection system, the urea injection system further comprises a urea nozzle and a selective catalytic reduction device, the urea nozzle is upstream of the selective catalytic reduction device, the controller is in communication connection with the urea nozzle and the selective catalytic reduction device, and the controller comprises: an acquisition unit 01 for acquiring a reaction temperature; wherein the reaction temperature is the temperature in the cavity of the selective catalytic reduction device; a first determination unit 02 for determining the control mode of the urea injection amount of the selective catalytic reduction device according to the reaction temperature; wherein the control mode is a first control mode or a second control mode, the first control mode is a mode for determining the urea injection amount of the urea nozzle according to the ammonia concentration, and the second control mode is a mode for determining the urea injection amount of the urea nozzle according to the ammonia adsorption amount in the selective catalytic reduction device, and the ammonia concentration includes the ammonia concentration downstream of the selective catalytic reduction device; a second determination unit 03 for determining the urea injection amount of the urea nozzle according to the control mode; wherein the urea injection amount includes a first urea injection amount and a second urea injection amount, the first urea injection amount is the urea amount injected by the urea nozzle in the case of controlling the urea nozzle by the first control mode, and the second urea injection amount is the urea amount injected by the urea nozzle in the case of controlling the urea nozzle by the second control mode.

[0106] Since the SCR catalyst chemical reaction varies significantly with temperature, in order to avoid the influence of temperature on the catalytic reaction and NH3 emission, the first determination unit further comprises a first determination module and a second determination module, the first determination module is used to determine that the control mode of the urea injection amount is the first control mode when the reaction temperature is greater than or equal to a preset temperature; and the second determination module is used to determine that the control mode of the urea injection amount is the second control mode when the reaction temperature is less than the preset temperature.

[0107] Since the catalyst reaction at medium-high temperature only needs a small amount of ammonia adsorption, the ammonia sensor can be directly used for closed-loop control, and the downstream NOx value is used for correction, which has no cross-sensitivity and fast response. The above control mode is the first control mode. The urea injection system further comprises a temperature sensor, a first nitrogen oxide sensor and an ammonia sensor. The temperature sensor is located upstream of the urea nozzle, the first nitrogen oxide sensor is located upstream of the temperature sensor, and the ammonia sensor is located downstream of the selective catalytic reduction device. The second determination unit comprises a first acquisition module and a third determination module: the first acquisition module is used to acquire first related parameters, and the first related parameters comprise: first nitrogen oxide concentration, exhaust gas flow, first temperature, first space velocity and first ammonia concentration. The first nitrogen oxide concentration is collected by the first nitrogen oxide sensor, the exhaust gas flow is the flow of the generated exhaust gas, the first temperature is the temperature collected by the temperature sensor, the first space velocity is the space velocity of the selective catalytic reduction device, and the first ammonia concentration is collected by the ammonia sensor. The third determination module is used to determine the urea injection amount of the urea nozzle according to the first related parameters.

[0108] Since the catalyst has a large ammonia adsorption capacity at low temperature, closed-loop control based on ammonia adsorption (ammonia storage) can use NH3 and NOx sensor correlation to correct efficiency. The above control mode is the second control mode. The urea injection system further comprises a temperature sensor, a second nitrogen oxide sensor and an ammonia sensor. The temperature sensor is located upstream of the urea nozzle, the second nitrogen oxide sensor is located downstream of the selective catalytic reduction device, and the ammonia sensor is located between the selective catalytic reduction device and the second nitrogen oxide sensor. The second determination unit further comprises a second acquisition module and a fourth determination module. The second acquisition module is used to acquire second related parameters, and the second related parameters comprise: second nitrogen oxide concentration, second temperature, second space velocity and second ammonia concentration. The second nitrogen oxide concentration is collected by the second nitrogen oxide sensor, the second temperature is the temperature collected by the temperature sensor, the second space velocity is the space velocity of the selective catalytic reduction device, and the second ammonia concentration is collected by the ammonia sensor. The fourth determination module is used to determine the urea injection amount of the urea nozzle according to the second related parameters.

[0109] In order to more accurately determine the first urea injection amount, the third determination module includes a first determination submodule, a second determination submodule and a third determination submodule, the first determination submodule is configured to determine a feedforward efficiency value according to the first space velocity and the first temperature, and correct the feedforward efficiency value to obtain an actual efficiency value; the second determination submodule is configured to determine the mass flow rate of the ammonia gas according to the first nitrogen oxide concentration and the exhaust gas flow rate; and the third determination submodule is configured to determine the first urea injection amount according to the mass flow rate of the ammonia gas and the actual efficiency value, the first urea injection amount being the product of the mass flow rate of the ammonia gas and the actual efficiency value.

[0110] In order to accurately obtain the efficiency correction value, the device further includes a first construction unit, a third determination unit, a fourth determination unit and a first correction unit, the first construction unit is configured to construct a first model, the first model being configured to represent a mapping relationship between the first space velocity, the first temperature, the concentration of the ammonia gas and the concentration of the nitrogen oxide; the third determination unit is configured to determine a theoretical value of the ammonia gas concentration according to the first space velocity, the first temperature and the first model, the theoretical value of the ammonia gas concentration being a theoretical value of the concentration of the ammonia gas at the ammonia gas sensor; the fourth determination unit is configured to determine an ammonia gas concentration deviation value according to the theoretical value of the ammonia gas concentration and the first ammonia gas concentration, wherein the ammonia gas concentration deviation value is the difference between the theoretical value of the ammonia gas concentration and the first ammonia gas concentration; and the first correction unit is configured to correct the ammonia gas concentration deviation value to obtain the efficiency correction value.

[0111] In order to accurately obtain the actual efficiency value, the first determination submodule includes a first determination subunit and a second determination subunit, the first determination subunit is configured to determine the feedforward efficiency value according to the first space velocity, the first temperature and the first model; and the second determination subunit is configured to determine the actual efficiency value according to the feedforward efficiency value and the efficiency correction value, wherein the actual efficiency value is the sum of the feedforward efficiency value and the efficiency correction value.

[0112] In one scheme, the second determination submodule includes a third determination subunit, a third acquisition module and a fourth determination subunit, the third determination subunit is configured to determine a first mass flow rate of the nitrogen oxide according to the first nitrogen oxide concentration and the exhaust gas flow rate; the third acquisition module is configured to acquire a mass ratio of the nitrogen oxide to the ammonia gas in complete reaction; and the fourth determination subunit is configured to determine the mass flow rate of the ammonia gas required for the complete reaction of the nitrogen oxide according to the first mass flow rate and the mass ratio. The mass flow rate of the ammonia gas required for the complete reaction of the nitrogen oxide can be accurately obtained.

[0113] Exemplarily, the fourth determining module comprises a fourth obtaining module, a second constructing unit, a fourth determining submodule and a fifth determining submodule. The fourth obtaining module is configured to obtain a current ammonia adsorption amount in the selective catalytic reduction device. The second constructing unit is configured to construct a second model, the second model being configured to represent a mapping relationship between a second space velocity, the second temperature, a theoretical value of nitrogen oxide and a predetermined ammonia adsorption amount of the selective catalytic reduction device, wherein the theoretical value of nitrogen oxide is a theoretical value of the concentration of nitrogen oxide at the second nitrogen oxide sensor. The fourth determining submodule is configured to determine the predetermined ammonia adsorption amount according to the second space velocity, the second temperature and the second model. The fifth determining submodule is configured to determine an ammonia adsorption amount deviation value according to the predetermined ammonia adsorption amount and the current ammonia adsorption amount, wherein the ammonia adsorption amount deviation value is a difference between the predetermined ammonia adsorption amount and the current ammonia adsorption amount.

[0114] To calculate the proportional adjustment coefficient, the fourth determining module further comprises a sixth determining submodule and a seventh determining submodule. The sixth determining submodule is configured to determine the theoretical value of nitrogen oxide according to the second space velocity, the second temperature and the second model. The seventh determining submodule is configured to determine a nitrogen oxide concentration deviation value according to the theoretical value of nitrogen oxide and the second nitrogen oxide concentration, wherein the nitrogen oxide concentration deviation value is a difference between the theoretical value of nitrogen oxide and the second nitrogen oxide concentration.

[0115] Exemplarily, the fourth determining module further comprises a fifth obtaining module, an eighth determining submodule and a ninth determining submodule. The fifth obtaining module is configured to obtain a correlation coefficient of nitrogen oxide and the ammonia sensor. The eighth determining submodule is configured to determine a proportional adjustment coefficient of the predetermined ammonia storage amount and the current ammonia storage amount according to the ammonia storage amount deviation value. The ninth determining submodule is configured to determine a model closed-loop correction efficiency value according to the ammonia storage amount deviation value, the proportional adjustment coefficient and the correlation coefficient.

[0116] In order to determine whether the correction factor of the NH3 leakage amount is contained in the second nitrogen oxide sensor, so as to control the direction and value of the model closed loop, the fourth determining module further comprises a fifth determining subunit, a sixth determining subunit and a seventh determining subunit. The fifth determining subunit is configured to determine a correlation factor coefficient according to the correlation between the second ammonia concentration and the second nitrogen oxide concentration. The sixth determining subunit is configured to determine a correction efficiency coefficient according to the correlation factor coefficient, the model closed loop correction efficiency value and the ammonia storage amount deviation value, wherein the correction efficiency coefficient is the product of the correlation factor coefficient and the model closed loop correction efficiency value and the sum of the ammonia storage amount deviation value. The seventh determining subunit is configured to determine the second urea injection amount according to the correction efficiency coefficient and the mass flow rate of ammonia, wherein the mass flow rate of ammonia is the mass flow rate of ammonia required for complete reaction of the nitrogen oxide, and the second urea injection amount is the product of the correction efficiency coefficient and the mass flow rate of ammonia.

[0117] The controller of the present application is applied to a urea injection system, wherein the urea injection system comprises a temperature sensor, a urea nozzle and a selective catalytic reduction device arranged in sequence from upstream to downstream, and the controller comprises: an acquisition unit configured to acquire a reaction temperature, wherein the reaction temperature is the temperature in the cavity of the selective catalytic reduction device; a first determining unit configured to determine a control mode of the urea injection amount of the selective catalytic reduction device according to the reaction temperature, wherein the control mode is a first control mode or a second control mode, the first control mode is a mode of determining the urea injection amount of the urea nozzle according to an ammonia concentration, and the second control mode is a mode of determining the urea injection amount of the urea nozzle according to the ammonia adsorption amount in the selective catalytic reduction device, and the ammonia concentration comprises the ammonia concentration downstream of the selective catalytic reduction device; and a second determining unit configured to determine the urea injection amount of the urea nozzle according to the control mode. The device considers different factors affecting the reaction rate at different temperatures by adopting different control logics at different temperatures, and more accurately determines the urea injection amount, so as to solve the problem that the prior art cannot completely prevent waste of reducing agent or ammonia leakage to cause secondary pollution.

[0118] Those skilled in the art will understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0119] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 means for functionally implementing the steps listed in the flowchart block or blocks.

[0120] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 means for functionally implementing the steps listed in the flowchart block or blocks.

[0121] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 means for functionally implementing the steps listed in the flowchart block or blocks.

[0122] In one typical configuration, the computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0123] The memory can include non-persistent memory and / or volatile memory, such as random access memory (RAM) and / or cache memory, for storing instructions and data used and / or generated by the computing device. The memory can also include non-volatile memory, such as read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, or other non-volatile memory.

[0124] Computer-readable media includes permanent and non-permanent, movable and non-movable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device. According to the definition herein, computer-readable media does not include transitory media such as modulated data signals and carriers.

[0125] It should also be noted that the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0126] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0127] 1) The method for determining the urea injection amount of the present application is applied to a controller in a urea injection system, the urea injection system further comprising a urea nozzle and a selective catalytic reduction device, the urea nozzle being upstream of the selective catalytic reduction device, the controller being in communication connection with the urea nozzle and the selective catalytic reduction device, first obtaining a reaction temperature, the reaction temperature being the temperature in the cavity of the selective catalytic reduction device; then determining the control mode of the urea injection amount of the selective catalytic reduction device according to the reaction temperature, the control mode being a first control mode or a second control mode, the first control mode being a mode for determining the urea injection amount of the urea nozzle according to the ammonia concentration, the second control mode being a mode for determining the urea injection amount of the urea nozzle according to the ammonia adsorption amount in the selective catalytic reduction device, the ammonia concentration including the ammonia concentration downstream of the selective catalytic reduction device; finally determining the urea injection amount of the urea nozzle according to the control mode, wherein the urea injection amount includes a first urea injection amount and a second urea injection amount, the first urea injection amount being the urea amount injected by the urea nozzle in the case of controlling the urea nozzle by the first control mode, the second urea injection amount being the urea amount injected by the urea nozzle in the case of controlling the urea nozzle by the second control mode. This method considers different factors that affect the reaction rate at different temperatures by using different control logics at different temperatures, more accurately determines the urea injection amount, and solves the problem of not being able to completely prevent the waste of reducing agent or ammonia leakage to cause secondary pollution in the prior art.

[0128] 2) The urea injection system of the present application comprises a urea nozzle for injecting urea; a selective catalytic conversion device for catalytic reaction, which is located downstream of the urea nozzle; a controller, which is in communication with the urea nozzle and the selective catalytic conversion device, for executing any of the above methods by obtaining a reaction temperature, which is the temperature in the cavity of the selective catalytic conversion device; then determining the control mode of the urea injection amount of the selective catalytic conversion device according to the reaction temperature, the control mode being the first control mode or the second control mode, the first control mode being the mode for determining the urea injection amount of the urea nozzle according to the ammonia concentration, the second control mode being the mode for determining the urea injection amount of the urea nozzle according to the ammonia adsorption amount in the selective catalytic conversion device, the ammonia concentration including the ammonia concentration downstream of the selective catalytic conversion device; and finally determining the urea injection amount of the urea nozzle according to the control mode, wherein the urea injection amount includes the first urea injection amount and the second urea injection amount, the first urea injection amount being the urea amount injected by the urea nozzle when the urea nozzle is controlled by the first control mode, and the second urea injection amount being the urea amount injected by the urea nozzle when the urea nozzle is controlled by the second control mode. The system considers different factors that affect the reaction rate at different temperatures by using different control logics at different temperatures, and more accurately determines the urea injection amount to solve the problem that the prior art cannot completely prevent the waste of reducing agent or the leakage of ammonia to cause secondary pollution.

[0129] 3) The controller of the application is arranged in a urea injection system, the urea injection system further comprises a urea nozzle and a selective catalytic reduction device, the urea nozzle is upstream of the selective catalytic reduction device, the controller is in communication connection with the urea nozzle and the selective catalytic reduction device, and the controller comprises: an acquisition unit configured to acquire a reaction temperature; wherein the reaction temperature is the temperature in the cavity of the selective catalytic reduction device; a first determination unit configured to determine a control mode of the urea injection amount of the selective catalytic reduction device according to the reaction temperature; wherein the control mode is a first control mode or a second control mode, the first control mode is a mode of determining the urea injection amount of the urea nozzle according to the ammonia concentration, and the second control mode is a mode of determining the urea injection amount of the urea nozzle according to the ammonia adsorption amount in the selective catalytic reduction device, and the ammonia concentration includes the ammonia concentration downstream of the selective catalytic reduction device; and a second determination unit configured to determine the urea injection amount of the urea nozzle according to the control mode; wherein the urea injection amount includes a first urea injection amount and a second urea injection amount, the first urea injection amount is the urea amount injected by the urea nozzle in the case of controlling the urea nozzle by using the first control mode, and the second urea injection amount is the urea amount injected by the urea nozzle in the case of controlling the urea nozzle by using the second control mode. The device considers different factors that affect the reaction rate at different temperatures by using different control logics at different temperatures, more accurately determines the urea injection amount, and solves the problem that the existing technology cannot completely prevent the waste of reducing agent or ammonia leakage to cause secondary pollution.

[0130] The above only describes the preferred embodiments of the application and is not intended to limit the application. Those skilled in the art can make various modifications and changes to the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method for determining the amount of urea injected, characterized in that, The determination method is applied to a controller in a urea injection system, the urea injection system further including a urea nozzle and a selective catalytic conversion device, the urea nozzle being upstream of the selective catalytic conversion device, and the controller being communicatively connected to the urea nozzle and the selective catalytic conversion device; the method includes: Obtain the reaction temperature; wherein, the reaction temperature is the internal temperature of the selective catalytic conversion device; Based on the reaction temperature, a control mode for the urea injection rate of the selective catalytic converter is determined; wherein, the control mode is a first control mode or a second control mode, the first control mode is a mode for determining the urea injection rate of the urea nozzle based on the ammonia concentration, and the second control mode is a mode for determining the urea injection rate of the urea nozzle based on the ammonia adsorption amount in the selective catalytic converter, wherein the ammonia concentration includes the ammonia concentration downstream of the selective catalytic converter; According to the control mode, the urea injection quantity of the urea nozzle is determined; wherein, the urea injection quantity includes a first urea injection quantity and a second urea injection quantity, the first urea injection quantity is the amount of urea injected by the urea nozzle when the urea nozzle is controlled using the first control mode, and the second urea injection quantity is the amount of urea injected by the urea nozzle when the urea nozzle is controlled using the second control mode.

2. The determination method according to claim 1, characterized in that, Based on the reaction temperature, the control mode for the urea injection quantity of the selective catalytic conversion device is determined, including: When the reaction temperature is greater than or equal to the preset temperature, the control mode for the urea injection volume is determined to be the first control mode. When the reaction temperature is lower than the preset temperature, the control mode for the urea injection volume is determined to be the second control mode.

3. The determination method according to claim 1, characterized in that, The control mode is the first control mode. The urea injection system further includes a temperature sensor, a first nitrogen-oxygen sensor, and an ammonia sensor. The temperature sensor is located upstream of the urea nozzle, the first nitrogen-oxygen sensor is located upstream of the temperature sensor, and the ammonia sensor is located downstream of the selective catalytic conversion device. Based on the control mode, the urea injection quantity of the urea nozzle is determined, including: The first relevant parameters are obtained, including: first nitrogen oxide concentration, exhaust gas flow rate, first temperature, first space velocity and first ammonia concentration, wherein the first nitrogen oxide concentration is collected by the first nitrogen oxide sensor, the exhaust gas flow rate is the flow rate of the generated exhaust gas, the first temperature is the temperature collected by the temperature sensor, the first space velocity is the space velocity of the selective catalytic conversion device, and the first ammonia concentration is collected by the ammonia sensor. The urea injection volume of the urea nozzle is determined based on the first relevant parameter.

4. The determination method according to claim 3, characterized in that, Determining the urea injection volume of the urea nozzle based on the first relevant parameter includes: Based on the first airspeed and the first temperature, a feedforward efficiency value is determined, and the feedforward efficiency value is corrected to obtain an actual efficiency value. The mass flow rate of ammonia is determined based on the concentration of the first nitrogen oxide compound and the flow rate of the exhaust gas. The first urea injection rate is determined based on the mass flow rate of ammonia and the actual efficiency value, wherein the first urea injection rate is the product of the mass flow rate of ammonia and the actual efficiency value.

5. The determination method according to claim 4, characterized in that, Before determining the feedforward efficiency value based on the first airspeed and the first temperature, and correcting the feedforward efficiency value to obtain the actual efficiency value, the method further includes: A first model is constructed to characterize the mapping relationship between the first air velocity, the first temperature, the concentration of ammonia, the concentration of nitrogen oxides, and the feedforward efficiency value. The theoretical value of the ammonia concentration is determined based on the first air velocity, the first temperature, and the first model. The theoretical value of the ammonia concentration is the theoretical value of the ammonia concentration at the ammonia sensor. Based on the theoretical value of the ammonia concentration and the first ammonia concentration, an ammonia concentration deviation value is determined, wherein the ammonia concentration deviation value is the difference between the theoretical value of the ammonia concentration and the first ammonia concentration; The ammonia concentration deviation value is corrected to obtain the efficiency correction value.

6. The determination method according to claim 5, characterized in that, Based on the first airspeed and the first temperature, a feedforward efficiency value is determined, and the feedforward efficiency value is corrected to obtain an actual efficiency value, including: The feedforward efficiency value is determined based on the first airspeed, the first temperature, and the first model. The actual efficiency value is determined based on the feedforward efficiency value and the efficiency correction value, wherein the actual efficiency value is the sum of the feedforward efficiency value and the efficiency correction value.

7. The determination method according to claim 4, characterized in that, Determining the mass flow rate of ammonia based on the concentration of the first nitrogen oxide compound and the flow rate of the waste gas includes: The first mass flow rate of the nitrogen oxide is determined based on the first nitrogen oxide concentration and the exhaust gas flow rate; Obtain the mass ratio of the nitrogen oxide compound to the ammonia gas after complete reaction; The mass flow rate of ammonia required for complete reaction of the nitrogen oxide compound is determined based on the first mass flow rate and the mass ratio.

8. The determination method according to claim 1, characterized in that, The control mode is the second control mode. The urea injection system further includes a temperature sensor, a second nitrogen-oxygen sensor, and an ammonia sensor. The temperature sensor is located upstream of the urea nozzle, the second nitrogen-oxygen sensor is located downstream of the selective catalytic conversion device, and the ammonia sensor is located between the selective catalytic conversion device and the second nitrogen-oxygen sensor. Determining the urea injection quantity from the urea nozzle according to the control mode includes: The second relevant parameters are obtained, including: second nitrogen oxide concentration, second temperature, second space velocity and second ammonia concentration, wherein the second nitrogen oxide concentration is collected by the second nitrogen oxide sensor, the second temperature is the temperature collected by the temperature sensor, the second space velocity is the space velocity of the selective catalytic conversion device, and the second ammonia concentration is collected by the ammonia sensor. The urea injection volume of the urea nozzle is determined based on the second relevant parameter.

9. The determining method according to claim 8, characterized in that, In determining the urea injection volume of the urea nozzle based on the second relevant parameter, the method further includes: Obtain the current ammonia adsorption amount in the selective catalytic conversion unit; A second model is constructed to characterize the mapping relationship between the second space velocity, the second temperature, the theoretical value of nitrogen oxides, and the predetermined ammonia adsorption amount of the selective catalytic conversion device, wherein the theoretical value of the nitrogen oxides is the theoretical value of the concentration of nitrogen oxides at the second nitrogen oxide sensor. The predetermined ammonia adsorption amount is determined based on the second air velocity, the second temperature, and the second model. Based on the predetermined ammonia adsorption amount and the current ammonia adsorption amount, a deviation value for ammonia adsorption amount is determined, wherein the deviation value for ammonia adsorption amount is the difference between the predetermined ammonia adsorption amount and the current ammonia adsorption amount.

10. The determination method according to claim 9, characterized in that, In determining the urea injection volume of the urea nozzle based on the second relevant parameter, the method further includes: The theoretical value of the nitrogen oxides is determined based on the second air velocity, the second temperature, and the second model; A nitrogen oxide concentration deviation value is determined based on the theoretical value of the nitrogen oxide and the concentration of the second nitrogen oxide, wherein the nitrogen oxide concentration deviation value is the difference between the theoretical value of the nitrogen oxide and the concentration of the second nitrogen oxide.

11. The determining method according to claim 10, characterized in that, In determining the urea injection volume of the urea nozzle based on the second relevant parameter, the method further includes: Obtain the correlation coefficient between the nitrogen oxides and the ammonia sensor; Based on the nitrogen oxide concentration deviation value, determine the ratio adjustment coefficient between the predetermined ammonia adsorption amount and the current ammonia adsorption amount; The closed-loop correction efficiency value of the model is determined based on the nitrogen oxide concentration deviation value, the proportional adjustment coefficient, and the correlation coefficient.

12. The determining method according to claim 11, characterized in that, In determining the urea injection volume of the urea nozzle based on the second relevant parameter, the method further includes: Based on the correlation between the second ammonia concentration and the second nitrogen oxide concentration, the correlation factor coefficient is determined; The correction efficiency coefficient is determined based on the relevant factor coefficients, the model closed-loop correction efficiency value, and the ammonia adsorption deviation value, wherein the correction efficiency coefficient is the sum of the product of the relevant factor coefficients and the model closed-loop correction efficiency value and the ammonia adsorption deviation value; The second urea injection rate is determined based on the corrected efficiency coefficient and the mass flow rate of ammonia, wherein the mass flow rate of ammonia is the mass flow rate of ammonia required for complete reaction of the nitrogen oxides, and the second urea injection rate is the product of the corrected efficiency coefficient and the mass flow rate of ammonia.

13. A urea injection system, characterized in that, include: Urea nozzle, used for spraying urea; A selective catalytic conversion device for conducting a catalytic reaction, the selective catalytic conversion device being located downstream of the urea nozzle; The controller, which is communicatively connected to the urea nozzle and the selective catalytic conversion device, is used to perform the determination method according to any one of claims 1 to 12.

14. The urea injection system according to claim 13, characterized in that, The system also includes: A temperature sensor is located upstream of the urea nozzle; A first nitrogen and oxygen sensor is located upstream of the temperature sensor; A second nitrogen and oxygen sensor is located downstream of the selective catalytic conversion device; An ammonia sensor is located between the selective catalytic conversion device and the second nitrogen and oxygen sensor.

15. A controller, characterized in that, The controller is disposed in the urea injection system, which further includes a urea nozzle and a selective catalytic conversion device. The urea nozzle is upstream of the selective catalytic conversion device. The controller is communicatively connected to the urea nozzle and the selective catalytic conversion device. The controller includes: An acquisition unit is used to acquire the reaction temperature; wherein the reaction temperature is the internal temperature of the selective catalytic conversion device; A first determining unit is configured to determine a control mode for the urea injection quantity of the selective catalytic converter based on the reaction temperature; wherein the control mode is a first control mode or a second control mode, the first control mode is a mode for determining the urea injection quantity of the urea nozzle based on the ammonia concentration, and the second control mode is a mode for determining the urea injection quantity of the urea nozzle based on the ammonia adsorption amount in the selective catalytic converter, wherein the ammonia concentration includes the ammonia concentration downstream of the selective catalytic converter; The second determining unit is configured to determine the urea injection quantity of the urea nozzle according to the control mode; wherein the urea injection quantity includes a first urea injection quantity and a second urea injection quantity, the first urea injection quantity being the amount of urea injected by the urea nozzle when the urea nozzle is controlled using the first control mode, and the second urea injection quantity being the amount of urea injected by the urea nozzle when the urea nozzle is controlled using the second control mode.

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