Urea injection method, device, readable storage medium and exhaust gas treatment system

Abstract

The application provides a urea injection method, device, readable storage medium and exhaust treatment system. The urea injection method comprises the following steps: in the case that the engine meets a cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow of the engine, an actual exhaust temperature, an ambient temperature before starting and an actual temperature before SCR, and controlling a urea injection mechanism to enter a cold start injection mode, wherein the cold start injection mode is a mode in which the urea injection mechanism sprays urea into a catalytic reaction container at the urea demand injection rate, and the actual temperature before SCR is an actual temperature at the inlet of the catalytic reaction container; and in the case that a urea injection termination condition is met, controlling the urea injection mechanism to stop spraying urea. The application at least solves the problem that the nitrogen and oxygen emission content is high during the cold start process of the engine in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tail gas treatment, in particular to a urea injection method and device, a computer readable storage medium and a tail gas treatment system. BACKGROUND

[0002] The diesel engine national six regulations have been implemented, and the next generation of emission regulations are more stringent in limiting emissions. Cold start emissions account for more than 70% of the entire WHTC (World Harmonized Transient Cycle) cold cycle emissions, and reducing cold start emissions is the key to next-generation emission control technology. Therefore, it is urgent to solve the problem of high nitrogen and oxygen emission content in the engine cold start process in the prior art. SUMMARY

[0003] The main purpose of the present application is to provide a urea injection method, device, computer readable storage medium and tail gas treatment system to at least solve the problem of high nitrogen and oxygen emission content in the engine cold start process in the prior art.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a urea injection method is provided, comprising: in the case that the engine meets the cold start condition, determining the urea demand injection rate according to the actual exhaust mass flow rate, the actual exhaust temperature, the pre-start ambient temperature and the actual SCR front temperature of the engine, and controlling the urea injection mechanism to enter the cold start injection mode, the cold start injection mode being the mode in which the urea injection mechanism sprays urea into the catalytic reaction container at the urea demand injection rate, and the actual SCR front temperature being the actual temperature at the inlet of the catalytic reaction container; in the case that the urea injection termination condition is met, controlling the urea injection mechanism to stop spraying urea.

[0005] Optionally, determining the urea demand injection rate according to the actual exhaust mass flow rate, the actual exhaust temperature, the pre-start ambient temperature and the actual SCR front temperature of the engine comprises: determining the exhaust heat coefficient according to the actual exhaust mass flow rate, the actual SCR front temperature and a preset relationship, the preset relationship being the corresponding relationship between the exhaust mass flow rate, the SCR front temperature and the coefficient; determining the exhaust heat of the engine according to the actual exhaust mass flow rate, the actual exhaust temperature, the pre-start ambient temperature and the preset specific heat capacity of exhaust gas; and determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase transition heat absorption amount, the phase transition heat absorption amount being determined according to the water heat absorption amount in different phases and the urea heat absorption amount in different phases in the urea hydrolysis process.

[0006] Optionally, determining the exhaust heat of the engine according to the actual exhaust mass flow rate, the actual exhaust temperature, the pre-starting ambient temperature and a preset specific heat capacity of exhaust gas comprises: determining a temperature variation as a difference between the actual exhaust temperature and the pre-starting ambient temperature according to the actual exhaust temperature and the pre-starting ambient temperature; determining the exhaust heat as a product of the actual exhaust mass flow rate, the temperature variation and the specific heat capacity of exhaust gas according to the actual exhaust mass flow rate, the temperature variation and the specific heat capacity of exhaust gas; determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase change endothermic quantity comprises: determining a urea hydrolysis endothermic quantity as a product of the exhaust heat and the exhaust heat coefficient according to the exhaust heat and the exhaust heat coefficient; determining the urea demand injection rate as a quotient of the urea hydrolysis endothermic quantity and the phase change endothermic quantity according to the urea hydrolysis endothermic quantity and the phase change endothermic quantity.

[0007] Optionally, the method further comprises: determining that the engine satisfies a cold start pre-ammonia storage condition when the coolant temperature of the engine is less than or equal to a first threshold value, the oil temperature of the engine is less than or equal to a second threshold value, the actual pre-SCR temperature is less than or equal to a third threshold value and the engine is powered on; determining that the engine satisfies the cold start condition when the engine satisfies the cold start pre-ammonia storage condition, the engine is started, the actual pre-SCR temperature is greater than or equal to a fourth threshold value and the engine speed is greater than or equal to a preset engine speed, the fourth threshold value being greater than the third threshold value.

[0008] Optionally, after controlling the urea injection mechanism to stop injecting urea, the method further comprises: controlling the urea injection mechanism to enter a normal injection mode when the actual pre-SCR temperature is greater than a fifth threshold value and the engine speed is greater than or equal to the preset engine speed, the normal injection mode being a mode in which the urea injection mechanism injects urea into the catalytic reaction container at a preset injection rate, the fifth threshold value being greater than the fourth threshold value.

[0009] Optionally, before controlling the urea injection mechanism to inject urea into the reaction container at the urea demand injection rate when the engine satisfies the cold start condition, the method further comprises: controlling the urea injection mechanism to operate to build up pressure of urea.

[0010] Optionally, after controlling the urea injection mechanism to enter the cold start injection mode, the method further comprises: obtaining a target parameter, the target parameter comprising at least one of: a cumulative urea injection amount, a cumulative urea injection time length; determining whether the target parameter reaches a preset threshold value; determining that the urea injection termination condition is satisfied when the target parameter reaches the preset threshold value.

[0011] According to another aspect of the present application, there is provided a urea injection device, comprising: a first determining unit configured to determine a urea required injection rate according to an actual exhaust mass flow, an actual exhaust temperature, a pre-start ambient temperature and an actual pre-SCR temperature of an engine, and control a urea injection mechanism to enter a cold start injection mode if the engine meets a cold start condition, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction vessel at the urea required injection rate, the actual pre-SCR temperature being an actual temperature at an inlet of the catalytic reaction vessel; and a first control unit configured to control the urea injection mechanism to stop injecting urea if a urea injection termination condition is met.

[0012] According to still another aspect of the present application, there is provided a computer-readable storage medium, the computer-readable storage medium including a stored program, wherein the computer-readable storage medium is caused to perform any of the methods described when the program is run.

[0013] According to yet another aspect of the present application, there is provided an exhaust treatment system, comprising: an exhaust treatment device comprising a catalytic reaction vessel and a urea injection mechanism, the urea injection mechanism being in communication with the catalytic reaction vessel; a diesel engine, an exhaust pipe of the diesel engine being in communication with the catalytic reaction vessel; a controller of the exhaust treatment device, one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods described.

[0014] The technical scheme of the application is applied to the case that the engine meets the cold start condition, first, the urea demand injection rate is determined according to the actual exhaust mass flow of the engine, the actual exhaust temperature, the ambient temperature before starting and the actual SCR front temperature, and the urea injection mechanism is controlled to enter the cold start injection mode, the urea is injected into the catalytic reaction container at the urea demand injection rate, and the tail gas in the catalytic reaction container is treated; then, the urea injection mechanism is controlled to stop injecting urea in the case that the urea injection termination condition is met. In the case of cold start of the engine, the urea demand injection rate is determined according to the ambient temperature before starting of the engine and the actual parameters of the engine, and the urea injection mechanism is controlled to inject urea at the rate, which realizes the advance injection of urea in the cold start environment. Since the ammonia storage demand of the SCR catalyst is large under the low temperature condition, the ammonia gas decomposed by the injected urea can be basically adsorbed by the SCR catalyst, which improves the ammonia storage of the SCR catalyst in the catalytic reaction container, so that the catalytic efficiency of the SCR catalyst is high, the conversion efficiency of nitrogen and oxygen in the tail gas under the low temperature starting environment of the engine is high, and the problem of high nitrogen and oxygen emission content in the cold start process of the engine is solved. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings, which form a part of the present description, illustrate the present application and together with the written description serve to explain the application. In the drawings:

[0016] Figure 1 A hardware structure block diagram of a mobile terminal for executing a urea injection method according to an embodiment of the present application is shown;

[0017] Figure 2 A flowchart of a urea injection method according to an embodiment of the present application is shown;

[0018] Figure 3 A flowchart of a specific urea injection method according to an embodiment of the present application is shown;

[0019] Figure 4 A flowchart of a cold start pre-ammonia storage enabling condition according to an embodiment of the present application is shown;

[0020] Figure 5 A flowchart of a cold start pressure building enabling condition according to an embodiment of the present application is shown;

[0021] Figure 6 A flowchart of a urea injection state according to an embodiment of the present application is shown;

[0022] Figure 7A flowchart of a urea demand injection rate calculation is shown according to an embodiment of the present application;

[0023] Figure 8 A graph of a correspondence between exhaust heat and urea demand injection rate during a cold start is shown according to an embodiment of the present application;

[0024] Figure 9 A flowchart of a judgment of a cold start urea injection enabling condition is shown according to an embodiment of the present application;

[0025] Figure 10 A flowchart of a judgment of a cold start urea injection termination condition is shown according to an embodiment of the present application;

[0026] Figure 11 A structural block diagram of a urea injection device is shown according to an embodiment of the present application.

[0027] Wherein, the accompanying drawings include the following reference signs:

[0028] 102, processor; 104, memory; 106, transmission device; 108, input and output device. DETAILED DESCRIPTION

[0029] 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 accompanying drawings and in combination with the embodiments.

[0030] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0031] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the accompanying drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological 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 including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0032] As introduced in the background technology, the prior art has the problem of high nitrogen oxide emission content during the engine cold start process. To solve this technical problem, the embodiments of the present application provide a urea injection method, device, computer-readable storage medium and exhaust gas treatment system.

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0034] The method embodiments provided in the embodiments of the present application can be executed in a mobile terminal, a computer terminal or a similar computing device. Taking running on a mobile terminal as an example, Figure 1 FIG. 1 is a hardware structure diagram of a mobile terminal for a urea injection method according to an embodiment of the present invention. Figure 1 As shown, the mobile terminal may include one or more ( Figure 1 Only one is shown) a processor 102 (the processor 102 may include but is not limited to a microprocessor MCU or a programmable logic device FPGA and other processing devices) and a memory 104 for storing data, wherein the mobile terminal may also include a transmission device 106 and an input and output device 108 for communication functions. It will be understood by those skilled in the art that Figure 1 The structure shown is only for illustration and does not limit the structure of the mobile terminal. Figure 1 More or fewer components than shown, or with Figure 1 Different configurations shown.

[0035] The memory 104 can be used to store computer programs, such as software programs of application software and modules, such as a computer program corresponding to the urea injection method in the embodiments of the present application. The processor 102 can execute various functional applications and data processing, i.e., implement the method, by running the computer program stored in the memory 104. The memory 104 can include a high-speed random access memory, and can further include a non-volatile memory, such as one or more magnetic storage devices, flash memories, or other non-volatile solid-state memories. In some examples, the memory 104 can further include memories disposed remotely with respect to the processor 102, which can be connected to the mobile terminal through a network. Examples of the network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof. The transmission device 106 is used to receive or send data via a network. The specific example of the network can include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 can be a radio frequency (RF) module, which is used to communicate with the Internet in a wireless manner.

[0036] In the embodiments, a urea injection method running on a mobile terminal, a computer terminal or a similar computing device is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown herein.

[0037] Figure 2 is a flowchart of the urea injection method according to the embodiments of the present application. As shown in Figure 2 , the method includes the following steps:

[0038] In step S201, when the engine meets the cold start condition, the urea demand injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and the actual temperature before SCR, and the urea injection mechanism is controlled to enter the cold start injection mode, which is a mode in which the urea injection mechanism sprays urea into the catalytic reaction container at the urea demand injection rate, and the actual temperature before SCR is the actual temperature at the inlet of the catalytic reaction container.

[0039] Specifically, in the case that the engine meets the cold start condition, the urea injection mechanism works in the cold start injection mode to inject urea. The urea injection mechanism can be a urea pump. The actual exhaust mass flow is the actual mass flow of the exhaust gas emitted by the engine; the actual exhaust temperature is the exhaust temperature after the turbocharger of the engine, which can also be understood as the exhaust temperature before the catalytic reduction reaction; the pre-start ambient temperature is the ambient temperature before the engine starts; the required urea injection rate is the amount of urea required to be injected per unit time; the catalytic reaction container is a container for selective catalytic reduction reaction, which has an SCR catalyst; the exhaust gas emitted by the engine enters the catalytic reaction container, and under the action of the catalyst, the urea reacts with the NOx in the exhaust gas to generate non-toxic and non-polluting nitrogen and water, achieving purification of the exhaust gas. X

[0040] Step S202, in the case that the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea.

[0041] Through the embodiment, in the case that the engine meets the cold start condition, first, the required urea injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and the actual pre-SCR temperature of the engine, and the urea injection mechanism is controlled to enter the cold start injection mode to inject urea into the catalytic reaction container at the required urea injection rate to process the exhaust gas in the catalytic reaction container; then in the case that the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea. In the case of cold start of the engine, the required urea injection rate is determined according to the pre-start ambient temperature and the actual parameters of the engine, and the urea injection mechanism is controlled to inject urea at the rate, which realizes the advance injection of urea in the cold start environment. Since the ammonia storage requirement of the SCR catalyst is large under low temperature conditions, the ammonia gas decomposed by the injected urea can be basically adsorbed by the SCR catalyst, which improves the ammonia storage of the SCR catalyst in the catalytic reaction container, so that the catalytic efficiency of the SCR catalyst is high, which ensures that the conversion efficiency of nitrogen and oxygen in the exhaust gas is high under the low temperature start environment of the engine, and solves the problem of high nitrogen and oxygen emission content in the cold start process of the engine.

[0042] ​In actual application process, the SCR catalyst has the characteristics of low-temperature ammonia storage and high-temperature ammonia storage, and the ammonia storage demand of the SCR catalyst is very large when the engine is cold started, while the urea spraying temperature is usually high, which causes the problem of insufficient ammonia storage of the SCR catalyst during cold start, so that the SCR efficiency is low. The application makes full use of the characteristics of high low-temperature ammonia storage of the SCR catalyst, and starts to spray urea during cold start, so as to ensure that the ammonia storage of the SCR catalyst during cold start is maintained at a preset level, and the problem of insufficient ammonia storage of the SCR caused by actual vehicle application is solved. The ammonia generated by the decomposition of the sprayed urea during cold start can be completely adsorbed by the SCR catalyst, so as to effectively catalyze and reduce the nitrogen oxide in the exhaust gas.

[0043] In order to further ensure that the urea demand injection rate meeting the engine cold start condition is accurately obtained, in an optional solution, the urea demand injection rate is determined according to the actual exhaust mass flow rate of the engine, the actual exhaust temperature, the ambient temperature before start and the actual temperature before SCR, including: determining the exhaust heat coefficient according to the actual exhaust mass flow rate, the actual temperature before SCR and a preset relationship, the preset relationship being a corresponding relationship between the exhaust mass flow rate, the temperature before SCR and the coefficient; determining the exhaust heat of the engine according to the actual exhaust mass flow rate, the actual exhaust temperature, the ambient temperature before start and the preset specific heat capacity of exhaust gas; determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and the preset phase change endothermic quantity, the phase change endothermic quantity being determined according to the water endothermic quantity of different phases and the urea endothermic quantity of different phases in the urea hydrolysis process. In this embodiment, according to the exhaust heat and the hydrolysis endothermic relationship in the urea hydrolysis process, the urea demand injection rate matching the current condition can be accurately calculated, so that the urea decomposition efficiency in the catalytic reaction container is high, the risk of urea crystallization is low, and the urea utilization rate is further ensured to be high.

[0044] The water endothermic quantity of different phases includes the heat absorbed by the conversion of liquid water into gaseous water, the heat absorbed by gaseous water and the heat absorbed by liquid water; the urea endothermic quantity of different phases includes the heat absorbed by the conversion of solid urea into liquid urea, the heat absorbed by solid urea and the heat absorbed by liquid urea. The phase change endothermic quantity is specifically equal to the water endothermic quantity of different phases*0.675+the urea endothermic quantity of different phases*0.325.

[0045] It should be noted that in the process of determining the urea demand injection rate, the determined urea demand injection rate is also changed in the case of changes in the actual exhaust mass flow, the actual exhaust temperature and the actual pre-SCR temperature, that is, the determined urea demand injection rate is not constant after the cold start of the engine, but changes with the actual temperature parameters and the actual exhaust parameters of the engine, which is beneficial to the conversion rate of NH3 generated by urea and the reduction of urea crystallization amount.

[0046] Specifically, the preset relationship can be stored in the form of a table or in other forms. In an exemplary embodiment, a relationship table representing the corresponding relationship between the exhaust mass flow, the pre-SCR temperature and the exhaust heat coefficient is shown in Table 1, where X represents the exhaust mass flow and Y represents the pre-SCR temperature.

[0047] Table 1

[0048]

[0049] According to the actual exhaust mass flow, the actual pre-SCR temperature and the preset relationship, the specific implementation mode of determining the exhaust heat coefficient can be: according to the actual exhaust mass flow and the actual pre-SCR temperature, searching for the same exhaust mass flow as the actual exhaust mass flow and the coefficient corresponding to the same pre-SCR temperature as the actual pre-SCR temperature in the preset relationship, which is the exhaust heat coefficient.

[0050] Since the pre-SCR temperature is a key factor affecting the generation of NH3 by urea, by looking up the table to determine the coefficient corresponding to the actual pre-SCR temperature, the problem of affecting the conversion of NH3 and the increase of crystallization caused by the determined urea demand injection rate being too large can be avoided.

[0051] Further, according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and the preset specific heat capacity of exhaust gas, the exhaust heat of the engine is determined, including: according to the actual exhaust temperature and the pre-start ambient temperature, determining a temperature change amount as the difference between the actual exhaust temperature and the pre-start ambient temperature; according to the actual exhaust mass flow, the temperature change amount and the specific heat capacity of the exhaust gas, determining the exhaust heat as the product of the actual exhaust mass flow, the temperature change amount and the specific heat capacity of the exhaust gas. The specific heat capacity of the exhaust gas is a fixed value. In the embodiment, the product of the actual exhaust mass flow, the temperature change amount and the specific heat capacity of the exhaust gas can be calculated to obtain the current exhaust heat efficiently and accurately.

[0052] Further, the urea demand injection rate is determined according to the exhaust heat, the exhaust heat coefficient and a preset phase change endothermic quantity, including: determining a urea hydrolysis absorption heat as a product of the exhaust heat and the exhaust heat coefficient according to the exhaust heat and the exhaust heat coefficient; determining the urea demand injection rate as a quotient of the urea hydrolysis absorption heat and the phase change endothermic quantity according to the urea hydrolysis absorption heat and the phase change endothermic quantity. In the embodiment, the exhaust heat is multiplied by the exhaust heat coefficient to obtain the urea hydrolysis absorption heat, and then the urea hydrosis absorption heat is divided by the phase change endothermic quantity to obtain the urea demand injection rate, so that the current urea demand injection rate can be efficiently and accurately obtained, and the urea decomposition rate is further ensured to be high and the urea crystallization amount is low.

[0053] Optionally, the method further includes: determining that the engine satisfies a cold start pre-ammonia storage condition when the coolant temperature of the engine is less than or equal to a first threshold value, the oil temperature of the engine is less than or equal to a second threshold value, the actual pre-SCR temperature is less than or equal to a third threshold value, and the engine is powered on; and determining that the engine satisfies the cold start condition when the engine satisfies the cold start pre-ammonia storage condition, the engine is started, the actual pre-SCR temperature is greater than or equal to a fourth threshold value, and the engine speed is greater than or equal to a preset engine speed, the fourth threshold value being greater than the third threshold value. Through the conditions, whether the engine satisfies the cold start condition, i.e., whether the engine is cold started, can be accurately determined.

[0054] The specific values of the first threshold value, the second threshold value, the third threshold value, the fourth threshold value and the preset engine speed can be flexibly set by a person skilled in the art according to actual conditions. In this application, the first threshold value, the second threshold value and the third threshold value are set to be 30℃ according to the provisions in GB17691. In addition, the fourth threshold value is set to be 50℃, and the preset engine speed is set to be 550rps.

[0055] In some optional embodiments of the present application, after the urea injection mechanism is controlled to stop injecting urea, the method further comprises: in the case that the actual SCR front temperature is greater than a fifth threshold value and the rotation speed is greater than or equal to the preset rotation speed, controlling the urea injection mechanism to enter a normal injection mode, the normal injection mode being a mode in which the urea injection mechanism injects urea into the catalytic reaction container at a preset injection rate, and the fifth threshold value being greater than the fourth threshold value. That is, the urea injection strategy in the cold start of the engine is independent of the urea injection strategy in the non-cold start (i.e., normal operation) of the engine, and the urea injection in the cold start does not affect the urea injection in the normal operation. In the cold start, the urea injection mechanism is controlled to enter the cold start injection mode, and in the normal operation, the urea injection mechanism is controlled to enter the normal injection mode, further ensuring that the engine exhaust purification effect is good whether in the cold start or in the normal operation, which is beneficial to control the consistency of nitrogen and oxygen emissions of the engine in the cold state and the non-cold state, and further achieves the effect that the nitrogen and oxygen emissions of the engine are low regardless of the state of operation.

[0056] The fifth threshold value and the specific value of the preset injection rate can be flexibly set by those skilled in the art according to actual needs. The preset injection rate can be fixed or variable, and the present application does not make specific limitations thereto.

[0057] In one embodiment, the fifth threshold value can be 185℃.

[0058] Exemplarily, in the case that the engine meets the cold start condition, before the urea injection mechanism is controlled to inject urea into the reaction container at the urea required injection rate, the method further comprises: controlling the urea injection mechanism to operate to build pressure of urea. By operating to build pressure of urea, the normal injection of the urea injection mechanism in the cold start injection mode is further ensured.

[0059] According to still some optional schemes of the present application, after the urea injection mechanism is controlled to enter the cold start injection mode, the method further comprises: acquiring a target parameter, the target parameter comprising at least one of: urea cumulative injection amount, urea cumulative injection time length; determining whether the target parameter reaches a preset threshold value; in the case that the target parameter reaches the preset threshold value, determining that the urea injection termination condition is met. In this embodiment, by controlling the exit timing of the cold start urea injection mode, the nitrogen and oxygen emission level of the engine exhaust during the cold start process is further ensured to be reduced, and the risk of urea crystallization is greatly reduced.

[0060] In an exemplary embodiment of the present application, the preset threshold of the cumulative injection duration can be set to 300s, and the preset threshold of the cumulative urea injection amount can be set to 100g. Of course, the two thresholds can be flexibly set according to different engine models, and are not limited to the parameter values.

[0061] In addition, the urea injection mechanism can be in a single injection mode to inject urea into the catalytic reaction container according to the urea demand injection rate, or in a multiple injection mode, such as double injection, to inject urea into the catalytic reaction container according to the urea demand injection rate. The injected urea can be in a solid state or in a liquid state.

[0062] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the implementation process of the urea injection method of the present application will be described in detail below in combination with specific embodiments.

[0063] The present embodiment relates to a specific urea injection method, as shown in Figure 3 which includes the following steps:

[0064] Step S1: The engine is powered on, and cold start pre-ammonia storage enablement is performed, and the specific process is as follows:

[0065] As shown in Figure 4 , the cold start pre-ammonia storage enablement conditions include: the engine is powered on, the coolant temperature of the engine ≤ 30℃, the oil temperature ≤ 30℃, and the temperature before the SCR ≤ 30℃; if the conditions are met, the engine cold start pre-ammonia storage enablement is performed.

[0066] Step S2: After the cold start pre-ammonia storage enablement is completed, cold start pressure building enablement is performed, and the specific process is as follows:

[0067] As shown in Figure 5 , the cold start pressure building enablement conditions include: the cold start pre-ammonia storage enablement, the temperature before the SCR ≥ 50℃, and the engine speed ≥ 550rps; if the conditions are met, the engine cold start pressure building enablement is performed.

[0068] Step S3: As shown in Figure 6 , after the cold start pressure building enablement is completed, the urea injection state becomes an injection preparation state; at the same time, the urea demand injection rate is calculated, as shown in Figure 7 , and the calculation process is as follows:

[0069] Cold start exhaust heat Q0*coefficient f = cold start urea hydrolysis absorption heat Q1(1);

[0070] Urea hydrolysis absorption heat Q1 = urea demand injection rate * (0.675 * different phase water heat absorption + 0.325 * different phase urea heat absorption)(2);

[0071] Cold start exhaust heat Q0 = exhaust specific heat capacity C * exhaust mass flow m * temperature change △t (3);

[0072] Wherein, f is obtained according to the actual exhaust mass flow and the actual SCR front temperature table 1;

[0073] According to formula (1), (2) and (3), the urea demand injection rate is calculated in real time, Figure 8 An exhaust heat and urea demand injection rate corresponding relationship diagram during cold start is exemplarily shown.

[0074] Step S4: after the urea injection amount calculation is completed, the cold start urea injection enablement is performed, and the specific process is as follows:

[0075] As shown in the figure, Figure 9 The cold start urea injection enablement conditions include: cold start condition enablement, cold start pressure building enablement, cold start urea injection mode enablement, and urea injection starts in the case of cold start urea injection enablement.

[0076] Step S5: after the cold start urea injection enablement is completed, the cold start urea injection termination condition is judged; if the condition is met, the cold start pre-ammonia storage is completed, and the specific condition is as follows: as shown in the figure, Figure 10 The urea injection amount demand value is set to 0 if the cold start urea injection time is accumulated for 300s or the cold start urea accumulation is greater than or equal to 100g. The cold start urea injection exit enablement is performed.

[0077] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown herein.

[0078] The urea injection device provided by the embodiment of the present application can be used to execute the urea injection method provided by the embodiment of the present application. The device for realizing the embodiment and the preferred embodiment has been described and will not be repeated. As used below, the term "module" can be a combination of software and / or hardware that realizes a predetermined function. Although the device described in the following embodiment is preferably realized in software, hardware or a combination of software and hardware is also possible and is conceived.

[0079] The urea injection device provided by the embodiment of the present application is introduced below.

[0080] Figure 11 is a schematic diagram of the urea injection device according to the embodiment of the present application. As shown in the figure, Figure 11 The device includes:

[0081] The first determining unit 10 is configured to determine a urea demand injection rate according to the actual exhaust mass flow, the actual exhaust temperature, the pre-starting ambient temperature and the actual pre-SCR temperature of the engine, and control the urea injection mechanism to enter a cold-start injection mode when the engine meets the cold-start condition, the cold-start injection mode being a mode in which the urea injection mechanism sprays urea into the catalytic reaction container at the urea demand injection rate, and the actual pre-SCR temperature being the actual temperature at the inlet of the catalytic reaction container.

[0082] Specifically, when the engine meets the cold-start condition, the urea injection mechanism works in the cold-start injection mode to spray urea. The urea injection mechanism can be a urea pump. The actual exhaust mass flow is the actual mass flow of exhaust emitted by the engine; the actual exhaust temperature is the turbocharger post-exhaust temperature of the engine, which can also be understood as the exhaust temperature before the catalytic reduction reaction; the pre-starting ambient temperature is the ambient temperature before the engine starts. The urea demand injection rate is the amount of urea needed to be injected per unit time. The catalytic reaction container is a container for selective catalytic reduction reaction, and has an SCR catalyst therein. The exhaust emitted by the engine is introduced into the catalytic reaction container, and under the action of the catalyst, the urea reacts with NOx in the exhaust to generate non-toxic and non-polluting nitrogen and water, thereby purifying the exhaust. X

[0083] The first control unit 20 is configured to control the urea injection mechanism to stop spraying urea when the urea injection termination condition is met.

[0084] ​According to the embodiment, when the engine meets the cold start condition, the first determination unit determines the urea demand injection rate according to the actual exhaust mass flow rate, the actual exhaust temperature, the ambient temperature before starting and the actual SCR front temperature of the engine, and controls the urea injection mechanism to enter the cold start injection mode to inject urea into the catalytic reaction container at the urea demand injection rate to process the exhaust gas in the catalytic reaction container; when the urea injection termination condition is met, the first control unit controls the urea injection mechanism to stop injecting urea. In the case of engine cold start, the urea demand injection rate is determined according to the ambient temperature before starting and the actual parameters of the engine, and the urea injection mechanism is controlled to inject urea at this rate, which realizes the advance injection of urea in the cold start environment. Since the ammonia storage demand of the SCR catalyst is large under low temperature conditions, the ammonia gas decomposed by the injected urea can be basically adsorbed by the SCR catalyst, which improves the ammonia storage of the SCR catalyst in the catalytic reaction container, so that the catalytic efficiency of the SCR catalyst is high, which ensures that the conversion efficiency of nitrogen and oxygen in the exhaust gas is high under the low temperature starting environment of the engine, and solves the problem of high nitrogen and oxygen emission content during the cold start process of the engine.

[0085] In actual application process, the SCR catalyst has the characteristics of low temperature ammonia storage and high temperature ammonia storage, and the ammonia storage demand of the SCR catalyst is very large when the engine is cold started, and the urea injection temperature is usually high, which causes the problem of insufficient ammonia storage of the SCR catalyst during cold start, which makes the SCR efficiency low. The application makes full use of the characteristics of high low temperature ammonia storage of the SCR catalyst, and starts to inject urea during cold start, which can ensure that the ammonia storage of the SCR catalyst during cold start is maintained at a preset level, and is not affected by the problem of insufficient ammonia storage of the SCR caused by actual vehicle application, which realizes the precise control of ammonia storage in the SCR catalyst during cold start. Although the injected urea during cold start cannot be completely decomposed to generate NH3, the generated NH3 can be completely adsorbed by the SCR catalyst, so as to effectively catalyze and reduce the nitrogen and oxygen in the exhaust gas, and reduce the nitrogen and oxygen emission content of the engine in cold state.

[0086] To further ensure that the urea demand injection rate conforming to the engine cold start condition is obtained more accurately, in an optional solution, the first determining unit comprises: a first determining module, configured to determine an exhaust heat coefficient according to the actual exhaust mass flow rate, the actual SCR front temperature and a preset relationship, the preset relationship being a corresponding relationship between the exhaust mass flow rate, the SCR front temperature and the coefficient; a second determining module, configured to determine the exhaust heat of the engine according to the actual exhaust mass flow rate, the actual exhaust temperature, the ambient temperature before start and a preset specific heat capacity of exhaust; and a third determining module, configured to determine the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase transition endothermic quantity, the phase transition endothermic quantity being determined according to the water endothermic quantity in different phases and the urea endothermic quantity in different phases in the urea hydrolysis process. In this embodiment, according to the exhaust heat and the hydrolysis endothermic relationship in the urea hydrolysis process, the urea demand injection rate matching the current condition can be accurately calculated, so that the urea decomposition efficiency in the catalytic reaction container is higher and the risk of urea crystallization is lower, further ensuring that the urea utilization rate is higher.

[0087] wherein the water endothermic quantity in different phases includes the heat absorbed by the conversion of liquid water into gaseous water, the heat absorbed by gaseous water and the heat absorbed by liquid water; and the urea endothermic quantity in different phases includes the heat absorbed by the conversion of solid urea into liquid urea, the heat absorbed by solid urea and the heat absorbed by liquid urea. The phase transition endothermic quantity is specifically equal to the water endothermic quantity in different phases * 0.675 + the urea endothermic quantity in different phases * 0.325.

[0088] It should be noted that in the process of determining the urea demand injection rate, the determined urea demand injection rate is also changed in the case of changes in the actual exhaust mass flow rate, the actual exhaust temperature and the actual SCR front temperature, that is, the determined urea demand injection rate is not constant after the engine is cold started, but changes with the actual temperature parameters and the actual exhaust parameters of the engine, which is conducive to the conversion rate of urea to produce NH3 and the reduction of urea crystallization amount.

[0089] Specifically, the preset relationship can be stored in the form of a table or in other forms. In an exemplary embodiment, a relationship table representing the corresponding relationship between the exhaust mass flow rate, the SCR front temperature and the exhaust heat coefficient is shown in Table 1, wherein X represents the exhaust mass flow rate and Y represents the SCR front temperature.

[0090] The first determining module can specifically include a searching submodule, configured to search, according to the actual exhaust mass flow and the actual SCR front temperature, the same exhaust mass flow as the actual exhaust mass flow and the same SCR front temperature as the actual SCR front temperature in the preset relationship, and the coefficient corresponding to the same exhaust mass flow and the same SCR front temperature is the exhaust heat coefficient.

[0091] Since the SCR front temperature is a key factor affecting the urea to generate NH3, by searching the table to determine the coefficient corresponding to the actual SCR front temperature, the determined urea demand injection rate can be prevented from being too large, and the problems of affecting the conversion of NH3 and the increase of crystallization can be avoided.

[0092] Further, the second determining module includes a first determining submodule, configured to determine a temperature change amount as a difference between the actual exhaust temperature and the pre-starting ambient temperature according to the actual exhaust temperature and the pre-starting ambient temperature; and a second determining submodule, configured to determine the exhaust heat as a product of the actual exhaust mass flow, the temperature change amount and the exhaust specific heat capacity according to the actual exhaust mass flow, the temperature change amount and the exhaust specific heat capacity. The exhaust specific heat capacity is a fixed value. In the embodiment, the current exhaust heat can be efficiently and accurately obtained by calculating the product of the actual exhaust mass flow, the temperature change amount and the exhaust specific heat capacity.

[0093] Further, the third determining module includes a third determining submodule, configured to determine a urea hydrolysis and absorption heat as a product of the exhaust heat and the exhaust heat coefficient according to the exhaust heat and the exhaust heat coefficient; and a fourth determining submodule, configured to determine the urea demand injection rate as a quotient of the urea hydrolysis and absorption heat and the phase transition endothermic heat according to the urea hydrolysis and absorption heat and the phase transition endothermic heat. In the embodiment, the urea hydrolysis and absorption heat is obtained by multiplying the exhaust heat and the exhaust heat coefficient, and the urea demand injection rate is obtained by dividing the urea hydroysis and absorption heat by the phase transition endothermic heat, so that the current urea demand injection rate can be efficiently and accurately obtained, and the urea decomposition rate is further ensured to be high and the urea crystallization amount is low.

[0094] Optionally, the device further comprises a second determining unit configured to determine that the engine satisfies a cold start pre-ammonia storage condition when the coolant temperature of the engine is less than or equal to a first threshold value, the oil temperature of the engine is less than or equal to a second threshold value, the actual pre-SCR temperature is less than or equal to a third threshold value, and the engine is powered on; and a third determining unit configured to determine that the engine satisfies the cold start condition when the engine satisfies the cold start pre-ammonia storage condition, the engine is started, the actual pre-SCR temperature is greater than or equal to a fourth threshold value, and the engine speed is greater than or equal to a preset engine speed, the fourth threshold value being greater than the third threshold value. By the conditions, it can be determined accurately whether the engine satisfies the cold start condition, i.e., whether the engine is cold started.

[0095] The first threshold value, the second threshold value, the third threshold value, the fourth threshold value, and the preset engine speed can be set flexibly by a person skilled in the art according to actual conditions. In this application, the first threshold value, the second threshold value, and the third threshold value are set to 30℃ according to the provisions in GB17691. In addition, the fourth threshold value is set to 50℃, and the preset engine speed is set to 550rps.

[0096] In another optional embodiment of the application, the device further comprises a second control unit configured to control the urea injection mechanism to enter a normal injection mode when the actual pre-SCR temperature is greater than a fifth threshold value and the engine speed is greater than or equal to the preset engine speed after the first control unit controls the urea injection mechanism to stop injecting urea, the normal injection mode being a mode in which the urea injection mechanism injects urea into the catalytic reaction container at a preset injection rate, the fifth threshold value being greater than the fourth threshold value. That is, the urea injection strategy in the engine cold start in this application is independent of the urea injection strategy in the engine non-cold start (i.e., normal operation), and the urea injection in the cold start does not affect the urea injection in the normal operation. In the cold start, the urea injection mechanism is controlled to enter the cold start injection mode, and in the normal operation, the urea injection mechanism is controlled to enter the normal injection mode, further ensuring that the engine exhaust purification effect is good whether in the cold start or in the normal operation, which is conducive to controlling the consistency of nitrogen and oxygen emissions of the engine in the cold state and the non-cold state, and further achieving the effect that the nitrogen and oxygen emissions of the engine are low regardless of the state of operation.

[0097] The urea injection device comprises a processor and a memory, the first determining unit and the first control unit are stored in the memory as program units, and the corresponding functions are realized by the processor executing the program units stored in the memory. The modules are located in the same processor; or the modules are located in different processors in any combination.

[0098] The processor comprises a core, and the core retrieves corresponding program units from the memory. The core can be one or more, and the problem of high nitrogen and oxygen emission content in the existing engine cold start process can be solved by adjusting the core parameters.

[0099] The memory can include non-permanent memory in a computer readable medium, random access memory (RAM) and / or non-volatile memory such as read-only memory (ROM) or flash memory (flash RAM), and the memory includes at least one memory chip.

[0100] The embodiment of the present application provides a computer readable storage medium, which comprises a stored program, wherein when the program runs, the device where the computer readable storage medium is located performs the urea injection method.

[0101] Specifically, the urea injection method comprises:

[0102] Step S201, in the case where the engine meets the cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow of the engine, an actual exhaust temperature, an ambient temperature before start and an actual temperature before SCR, and controlling a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction container at the urea demand injection rate, and the actual temperature before SCR being an actual temperature at the inlet of the catalytic reaction container.

[0103] Specifically, in the case where the engine meets the cold start condition, the urea injection mechanism works in the cold start injection mode to inject urea. The urea injection mechanism can be a urea pump. The actual exhaust mass flow is the actual mass flow of exhaust gas emitted by the engine; the actual exhaust temperature is the exhaust temperature after the turbocharger of the engine, and can also be understood as the exhaust temperature before the catalytic reduction reaction; the ambient temperature before start is the ambient temperature before the engine starts. The urea demand injection rate is the amount of urea needed to be injected per unit time. The catalytic reaction container is a container for selective catalytic reduction reaction, and has an SCR catalyst in the container. The exhaust gas emitted by the engine enters the catalytic reaction container, and under the action of the catalyst, the urea reacts with NOx in the exhaust gas to generate non-toxic and non-polluting nitrogen and water, so as to purify the exhaust gas. X

[0104] Step S202, in the case where the urea injection termination condition is met, controlling the urea injection mechanism to stop injecting urea.

[0105] ​Optionally, the determining the urea demand injection rate according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and the actual pre-SCR temperature comprises: determining an exhaust heat coefficient according to the actual exhaust mass flow, the actual pre-SCR temperature and a preset relationship, the preset relationship being a corresponding relationship between exhaust mass flow, pre-SCR temperature and the coefficient; determining an exhaust heat of the engine according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and a preset specific heat capacity of exhaust gas; and determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase transition heat absorption amount, the phase transition heat absorption amount being determined according to water heat absorption amounts in different phases and urea heat absorption amounts in different phases in a urea hydrolysis process.

[0106] Optionally, the determining the exhaust heat of the engine according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and the preset specific heat capacity of exhaust gas comprises: determining a temperature variation as a difference between the actual exhaust temperature and the pre-start ambient temperature according to the actual exhaust temperature and the pre-start ambient temperature; and determining the exhaust heat as a product of the actual exhaust mass flow, the temperature variation and the specific heat capacity of exhaust gas according to the actual exhaust mass flow, the temperature variation and the specific heat capacity of exhaust gas; and the determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and the preset phase transition heat absorption amount comprises: determining a urea hydrolysis absorption heat as a product of the exhaust heat and the exhaust heat coefficient according to the exhaust heat and the exhaust heat coefficient; and determining the urea demand injection rate as a quotient of the urea hydrolysis absorption heat and the phase transition heat absorption amount according to the urea hydrolysis absorption heat and the phase transition heat absorption amount.

[0107] Optionally, the method further comprises: determining that the engine satisfies a cold start pre-ammonia storage condition when a coolant temperature of the engine is less than or equal to a first threshold value, an engine oil temperature of the engine is less than or equal to a second threshold value, the actual pre-SCR temperature is less than or equal to a third threshold value and the engine is powered on; and determining that the engine satisfies the cold start condition when the engine satisfies the cold start pre-ammonia storage condition, the engine is started, the actual pre-SCR temperature is greater than or equal to a fourth threshold value and a rotational speed of the engine is greater than or equal to a preset rotational speed, the fourth threshold value being greater than the third threshold value.

[0108] Optionally, after controlling the urea injection mechanism to stop injecting urea, the method further comprises: in the case that the actual SCR front temperature is greater than a fifth threshold and the rotation speed is greater than or equal to the preset rotation speed, controlling the urea injection mechanism to enter a normal injection mode, the normal injection mode being a mode in which the urea injection mechanism injects urea into the catalytic reaction container at a preset injection rate, the fifth threshold being greater than the fourth threshold.

[0109] Optionally, in the case that the engine meets the cold start condition, before controlling the urea injection mechanism to inject urea into the reaction container at the urea demand injection rate, the method further comprises: controlling the urea injection mechanism to operate to build pressure of urea.

[0110] Optionally, after controlling the urea injection mechanism to enter the cold start injection mode, the method further comprises: obtaining a target parameter, the target parameter comprising at least one of: urea cumulative injection amount, urea cumulative injection time length; determining whether the target parameter reaches a preset threshold; in the case that the target parameter reaches the preset threshold, determining that the urea injection termination condition is met.

[0111] Embodiments of the present application provide a tail gas treatment system, comprising:

[0112] The tail gas treatment device comprises a catalytic reaction container and a urea injection mechanism, the urea injection mechanism being in communication with the catalytic reaction container; and a diesel engine, an exhaust pipe of the diesel engine being in communication with the catalytic reaction container.

[0113] The controller of the tail gas treatment device, one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs comprising a program for executing any one of the methods.

[0114] The controller herein can be a server, a PC, a PAD, a mobile phone, an ECU, etc.

[0115] Specifically, the urea injection method comprises:

[0116] Step S201, in the case that the engine meets the cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow rate, an actual exhaust temperature, a pre-start ambient temperature, and an actual SCR front temperature of the engine, and controlling a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into the catalytic reaction container at the urea demand injection rate, the actual SCR front temperature being an actual temperature at an inlet of the catalytic reaction container;

[0117] Specifically, in the case that the engine meets the cold start condition, the urea injection mechanism works in the cold start injection mode to inject urea. The urea injection mechanism can be a urea pump. The actual exhaust mass flow is the actual mass flow of the exhaust emitted by the engine; the actual exhaust temperature is the exhaust temperature after the turbocharger of the engine, which can also be understood as the exhaust temperature before the catalytic reduction reaction; the pre-start ambient temperature is the ambient temperature before the engine starts. The urea required injection rate is the amount of urea required to be injected per unit time. The catalytic reaction container is a container for selective catalytic reduction reaction, which has an SCR catalyst therein. The exhaust emitted by the engine enters the catalytic reaction container, and under the action of the catalyst, the urea reacts with NOx in the exhaust to generate non-toxic and non-polluting nitrogen and water, thereby purifying the exhaust. X

[0118] Step S202, in the case that the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea.

[0119] Optionally, the urea required injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature, and the actual pre-SCR temperature, comprising: determining an exhaust heat coefficient according to the actual exhaust mass flow, the actual pre-SCR temperature, and a preset relationship, the preset relationship being a corresponding relationship between the exhaust mass flow, the pre-SCR temperature, and the coefficient; determining the exhaust heat of the engine according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature, and a preset specific heat capacity of exhaust; and determining the urea required injection rate according to the exhaust heat, the exhaust heat coefficient, and a preset phase transition endothermic quantity, the phase transition endothermic quantity being determined according to the water endothermic quantity in different phases and the urea endothermic quantity in different phases in the urea hydrolysis process.

[0120] ​Optionally, determining the exhaust heat of the engine according to the actual exhaust mass flow rate, the actual exhaust temperature, the pre-starting ambient temperature and a preset specific heat capacity of exhaust gas comprises: determining a temperature variation as a difference between the actual exhaust temperature and the pre-starting ambient temperature according to the actual exhaust temperature and the pre-starting ambient temperature; determining the exhaust heat as a product of the actual exhaust mass flow rate, the temperature variation and the specific heat capacity of exhaust gas according to the actual exhaust mass flow rate, the temperature variation and the specific heat capacity of exhaust gas; determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase transition endothermic quantity comprises: determining a urea hydrolysis endothermic quantity as a product of the exhaust heat and the exhaust heat coefficient according to the exhaust heat and the exhaust heat coefficient; determining the urea demand injection rate as a quotient of the urea hydrolysis endothermic quantity and the phase transition endothermic quantity according to the urea hydrolysis endothermic quantity and the phase transition endothermic quantity.

[0121] Optionally, the method further comprises: determining that the engine satisfies a cold start pre-ammonia storage condition when the coolant temperature of the engine is less than or equal to a first threshold value, the oil temperature of the engine is less than or equal to a second threshold value, the actual pre-SCR temperature is less than or equal to a third threshold value and the engine is powered on; determining that the engine satisfies the cold start condition when the engine satisfies the cold start pre-ammonia storage condition, the engine is started, the actual pre-SCR temperature is greater than or equal to a fourth threshold value and the engine speed is greater than or equal to a preset engine speed, the fourth threshold value being greater than the third threshold value.

[0122] Optionally, after controlling the urea injection mechanism to stop injecting urea, the method further comprises: controlling the urea injection mechanism to enter a normal injection mode when the actual pre-SCR temperature is greater than a fifth threshold value and the engine speed is greater than or equal to the preset engine speed, the normal injection mode being a mode in which the urea injection mechanism injects urea into the catalytic reaction container at a preset injection rate, the fifth threshold value being greater than the fourth threshold value.

[0123] Optionally, before controlling the urea injection mechanism to inject urea into the reaction container at the urea demand injection rate when the engine satisfies the cold start condition, the method further comprises: controlling the urea injection mechanism to operate to build up pressure of urea.

[0124] Optionally, after controlling the urea injection mechanism to enter the cold start injection mode, the method further comprises: acquiring a target parameter, the target parameter comprising at least one of: a cumulative urea injection amount, a cumulative urea injection time length; determining whether the target parameter reaches a preset threshold value; determining that the urea injection termination condition is satisfied when the target parameter reaches the preset threshold value.

[0125] The application also provides a computer program product comprising computer instructions which, when executed by a processor, implement at least the following method steps:

[0126] In step S201, if the engine meets the cold start condition, the urea required injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and the actual SCR front temperature of the engine, and the urea injection mechanism is controlled to enter the cold start injection mode, which is a mode in which the urea injection mechanism injects urea into the catalytic reaction container at the urea required injection rate, and the actual SCR front temperature is the actual temperature at the inlet of the catalytic reaction container.

[0127] In step S202, if the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea.

[0128] Optionally, the urea required injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and the actual SCR front temperature of the engine, which includes: determining the exhaust heat coefficient according to the actual exhaust mass flow, the actual SCR front temperature and a preset relationship, the preset relationship being a corresponding relationship between the exhaust mass flow, the SCR front temperature and the coefficient; determining the exhaust heat of the engine according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and a preset specific heat capacity of exhaust gas; and determining the urea required injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase change endotherm, the phase change endotherm being determined according to the water endotherm and the urea endotherm in different phases in the urea hydrolysis process.

[0129] Optionally, the exhaust heat of the engine is determined according to the actual exhaust mass flow, the actual exhaust temperature, the pre-start ambient temperature and a preset specific heat capacity of exhaust gas, which includes: determining the temperature change amount as the difference between the actual exhaust temperature and the pre-start ambient temperature according to the actual exhaust temperature and the pre-start ambient temperature; and determining the exhaust heat as the product of the actual exhaust mass flow, the temperature change amount and the specific heat capacity of exhaust gas according to the actual exhaust mass flow, the temperature change amount and the specific heat capacity of exhaust gas. The urea required injection rate is determined according to the exhaust heat, the exhaust heat coefficient and a preset phase change endotherm, which includes: determining the urea hydrolysis absorption heat as the product of the exhaust heat and the exhaust heat coefficient according to the exhaust heat and the exhaust heat coefficient; and determining the urea required injection rate as the urea hydrolysis absorption heat divided by the phase change endotherm according to the urea hydrolysis absorption heat and the phase change endotherm.

[0130] Optionally, the method further comprises: determining that the engine satisfies a cold start pre-ammonia storage condition, in a case that the coolant temperature of the engine is less than or equal to a first threshold, the oil temperature of the engine is less than or equal to a second threshold, the actual pre-SCR temperature is less than or equal to a third threshold, and the engine is powered on; determining that the engine satisfies the cold start condition, in a case that the engine satisfies the cold start pre-ammonia storage condition, the engine is started, the actual pre-SCR temperature is greater than or equal to a fourth threshold, and the engine speed is greater than or equal to a preset speed, the fourth threshold being greater than the third threshold.

[0131] Optionally, after controlling the urea injection mechanism to stop injecting urea, the method further comprises: controlling the urea injection mechanism to enter a normal injection mode, in a case that the actual pre-SCR temperature is greater than a fifth threshold, and the engine speed is greater than or equal to the preset speed, the normal injection mode being a mode in which the urea injection mechanism injects urea into the catalytic reaction container at a preset injection rate, the fifth threshold being greater than the fourth threshold.

[0132] Optionally, before controlling the urea injection mechanism to inject urea into the reaction container at the urea demand injection rate, in a case that the engine satisfies the cold start condition, the method further comprises: controlling the urea injection mechanism to operate to build pressure of urea.

[0133] Optionally, after controlling the urea injection mechanism to enter the cold start injection mode, the method further comprises: obtaining a target parameter, the target parameter comprising at least one of: a cumulative urea injection amount, a cumulative urea injection time length; determining whether the target parameter reaches a preset threshold; determining that the urea injection termination condition is satisfied, in a case that the target parameter reaches the preset threshold.

[0134] Obviously, those skilled in the art should understand that the modules or steps of the present application can be realized by general computing devices, which can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, which can be realized by program codes executable by computing devices, so that they can be stored in storage devices and executed by computing devices, and in some cases, the steps shown or described can be executed in different order, or they can be respectively manufactured into individual integrated circuit modules, or multiple modules or steps among them can be manufactured into a single integrated circuit module. Thus, the present application is not limited to any specific combination of hardware and software.

[0135] Those skilled in the art will appreciate that embodiments of the application can be readily used as software, hardware, or a combination of software and hardware. In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0136] The present application is described in reference to the flowchart illustrations and / or block diagrams according to the embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing system, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0137] 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 functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0138] These 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 illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0139] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0140] The memory can include non-persistent memory, random access memory (RAM), and / or non-volatile memory, such as read only memory (ROM) or flash memory, among others. The memory is an example of computer-readable media.

[0141] 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 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.

[0142] 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.

[0143] From the above description, it can be seen that the embodiments described in the present application achieve the following technical effects:

[0144] The urea injection method of the application, in the case that the engine meets the cold start condition, first determines the urea required injection rate according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and the actual SCR front temperature, and controls the urea injection mechanism to enter the cold start injection mode, to inject urea into the catalytic reaction container at the urea required injection rate, to process the tail gas in the catalytic reaction container; then in the case that the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea. In the case of engine cold start, the urea required injection rate is determined according to the ambient temperature before starting and the actual parameters of the engine, and the urea injection mechanism is controlled to inject urea at this rate, which realizes the advance injection of urea under the cold start environment. Since the ammonia storage demand of the SCR catalyst is large under low temperature conditions, the ammonia gas decomposed by the injected urea can be basically adsorbed by the SCR catalyst, which improves the ammonia storage of the SCR catalyst in the catalytic reaction container, so that the catalytic efficiency of the SCR catalyst is high, which ensures that the conversion efficiency of nitrogen and oxygen in the tail gas under the low temperature starting environment of the engine is high, and solves the problem of high nitrogen and oxygen emission content in the engine cold start process.

[0145] 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 changes and modifications 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 urea injection method, characterized by, The method comprises: In the case that the engine meets a cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow rate, an actual exhaust temperature, an ambient temperature before start, and an actual temperature before SCR of the engine, and controlling a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction container at the urea demand injection rate, the actual temperature before SCR being an actual temperature at an inlet of the catalytic reaction container; In the case that a urea injection termination condition is met, controlling the urea injection mechanism to stop injecting urea, The method further comprises: In the case that the engine meets a cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow rate, an actual exhaust temperature, an ambient temperature before start, and an actual temperature before SCR of the engine, and controlling a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction container at the urea demand injection rate, the actual temperature before SCR being an actual temperature at an inlet of the catalytic reaction container; In the case that a urea injection termination condition is met, controlling the urea injection mechanism to stop injecting urea, The method further comprises: In the case that the engine meets a cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow rate, an actual exhaust temperature, an ambient temperature before start, and an actual temperature before SCR of the engine, and controlling a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction container at the urea demand injection rate, the actual temperature before SCR being an actual temperature at an inlet of the catalytic reaction container; 2. The method of claim 1, wherein The method further comprises: In the case that the engine meets a cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow rate, an actual exhaust temperature, an ambient temperature before start, and an actual temperature before SCR of the engine, and controlling a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction container at the urea demand injection rate, the actual temperature before SCR being an actual temperature at an inlet of the catalytic reaction container; In the case that a urea injection termination condition is met, controlling the urea injection mechanism to stop injecting urea, The method further comprises: In the case that the engine meets a cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow rate, an actual exhaust temperature, an ambient temperature before start, and an actual temperature before SCR of the engine, and controlling a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction container at the urea demand injection rate, the actual temperature before SCR being an actual temperature at an inlet of the catalytic reaction container; 3. The method of claim 1, wherein, In the case that the engine meets a cold start condition, determining a urea demand injection rate according to an actual exhaust mass flow rate, an actual exhaust temperature, an ambient temperature before start, and an actual temperature before SCR of the engine, and controlling a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction container at the urea demand injection rate, the actual temperature before SCR being an actual temperature at an inlet of the catalytic reaction container; ​ In a case that the engine meets the cold start pre-ammonia storage condition, the engine is started, the actual pre-SCR temperature is greater than or equal to a fourth threshold value, and the engine speed is greater than or equal to a preset speed, it is determined that the engine meets the cold start condition, and the fourth threshold value is greater than the third threshold value.

4. The method of claim 3, wherein, After the method controls the urea injection mechanism to stop injecting urea, the method further comprises: In a case that the actual pre-SCR temperature is greater than a fifth threshold value and the engine speed is greater than or equal to the preset speed, the method controls the urea injection mechanism to enter a normal injection mode, the normal injection mode is a mode in which the urea injection mechanism injects urea into the catalytic reaction container at a preset injection rate, and the fifth threshold value is greater than the fourth threshold value.

5. The method according to any one of claims 1 to 4, characterized in that, In a case that the engine meets the cold start condition, before the method controls the urea injection mechanism to inject urea into the reaction container at the urea demand injection rate, the method further comprises: The method controls the urea injection mechanism to operate to build pressure of urea.

6. The method according to any one of claims 1 to 4, characterized in that, After the method controls the urea injection mechanism to enter the cold start injection mode, the method further comprises: The method acquires a target parameter, and the target parameter comprises at least one of a urea cumulative injection amount and a urea cumulative injection time length; The method determines whether the target parameter reaches a preset threshold value; In a case that the target parameter reaches the preset threshold value, it is determined that the urea injection termination condition is met.

7. A urea injection device characterized by comprising: Comprise: The first determination unit is configured to, in a case that the engine meets the cold start condition, determine a urea demand injection rate according to an actual exhaust mass flow rate, an actual exhaust temperature, a pre-start ambient temperature, and an actual pre-SCR temperature of the engine, and control a urea injection mechanism to enter a cold start injection mode, the cold start injection mode being a mode in which the urea injection mechanism injects urea into a catalytic reaction container at the urea demand injection rate, and the actual pre-SCR temperature being an actual temperature at an inlet of the catalytic reaction container; The first control unit is configured to, in a case that the urea injection termination condition is met, control the urea injection mechanism to stop injecting urea, The first determination unit comprises: a first determination module configured to determine an exhaust heat coefficient according to the actual exhaust mass flow rate, the actual pre-SCR temperature, and a preset relationship, the preset relationship being a corresponding relationship between an exhaust mass flow rate, a pre-SCR temperature, and a coefficient; a second determination module configured to determine an exhaust heat of the engine according to the actual exhaust mass flow rate, the actual exhaust temperature, the pre-start ambient temperature, and a preset specific heat capacity of exhaust; and a third determination module configured to determine the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient, and a preset phase transition endothermic amount, the phase transition endothermic amount being determined according to water endothermic amounts in different phases in a urea hydrolysis process and urea endothermic amounts in different phases.

8. A computer-readable storage medium, characterized in that, The computer readable storage medium comprises a stored program, wherein the program controls a device in which the computer readable storage medium is located to perform the method of any one of claims 1 to 6 when the program is executed.

9. An off-gas treatment system characterized by, Comprise: An exhaust treatment device comprising a catalytic reaction vessel and a urea injection mechanism in communication with the catalytic reaction vessel; A diesel engine having an exhaust pipe in communication with a catalytic reaction vessel; A controller of the exhaust treatment device, one or more processors, memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including programs to perform any of the methods of claims 1-6.

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