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

Abstract

The invention provides a urea injection method and device, a readable storage medium and a tail gas treatment system.The urea injection method comprises the steps that under the condition that an 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 environment temperature before start and the actual temperature before SCR of the engine, and the urea required injection rate is determined; the urea injection mechanism is controlled to enter a cold start injection mode, the cold start injection mode is the mode that the urea injection mechanism injects urea into the catalytic reaction container at the urea required injection rate, and the actual temperature before SCR is the actual temperature of an inlet of the catalytic reaction container; and under the condition that the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea. The problem that in the prior art, the nitrogen and oxygen emission content is high in the cold start process of an engine is at least solved.

Description

Technical Field

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

[0002] The National VI regulations for diesel engines have been implemented, and the next generation of emission regulations has stricter restrictions on emissions. Cold start emissions account for more than 70% of the entire WHTC (World Harmonized Transient Cycle) cold cycle emissions. Reducing cold start emissions is the key to the next generation of emission control technology. Therefore, it is urgent to solve the problem of high nitrogen oxide emissions during the cold start process of the engine in the existing technology. Summary of the invention

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

[0004] To achieve the above-mentioned object, according to one aspect of the present application, a urea injection method is provided, comprising: when an engine meets a cold start condition, determining a required urea 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 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 injects urea into a catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is an actual inlet temperature of the catalytic reaction container; and when a urea injection termination condition is met, controlling the urea injection mechanism to stop injecting urea.

[0005] Optionally, the required urea injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and the actual pre-SCR temperature of the engine, including: determining the exhaust heat coefficient according to the actual exhaust mass flow, the actual pre-SCR temperature and a preset relationship, the preset relationship being a correspondence 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 ambient temperature before starting and a preset exhaust specific heat capacity; determining the required urea injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption, the phase conversion heat absorption being determined according to the heat absorption of water in different phases and the heat absorption of urea in different phases during urea hydrolysis.

[0006] Optionally, the exhaust heat of the engine is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and a preset exhaust specific heat capacity, including: determining the temperature change as the difference between the actual exhaust temperature and the ambient temperature before starting according to the actual exhaust temperature and the ambient temperature before starting; determining the exhaust heat as the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity according to the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity; determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption capacity, including: 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; determining the urea demand injection rate as the urea hydrolysis absorption heat divided by the phase conversion heat absorption heat according to the urea hydrolysis absorption heat and the phase conversion heat absorption capacity.

[0007] Optionally, the method also includes: determining that the engine satisfies the cold start pre-ammonia storage condition when 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; and determining that the engine satisfies the cold start condition, and the fourth threshold is greater than the third threshold, 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 and the engine speed is greater than or equal to a preset speed.

[0008] Optionally, after controlling the urea injection mechanism to stop injecting urea, the method further includes: when the actual pre-SCR temperature is greater than a fifth threshold and the speed is greater than or equal to the preset speed, controlling the urea injection mechanism to enter a normal injection mode, wherein 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 is greater than the fourth threshold.

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

[0010] Optionally, after controlling the urea injection mechanism to enter the cold start injection mode, the method further includes: acquiring a target parameter, the target parameter including at least one of the following: a cumulative urea injection amount, a cumulative urea injection duration; determining whether the target parameter reaches a preset threshold; and when the target parameter reaches the preset threshold, determining that the urea injection termination condition is satisfied.

[0011] According to another aspect of the present application, a urea injection device is provided, comprising: a first determination unit, for determining a required urea 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 when an engine satisfies a cold start condition, 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 injects urea into a catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is an actual inlet temperature of the catalytic reaction container; and a first control unit, for controlling the urea injection mechanism to stop injecting urea when a urea injection termination condition is satisfied.

[0012] According to another aspect of the present application, a computer-readable storage medium is provided, wherein the computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute any one of the methods described.

[0013] According to another aspect of the present application, an exhaust gas treatment system is provided, comprising: an exhaust gas treatment device, comprising a catalytic reaction vessel and a urea injection mechanism, the urea injection mechanism being connected to the catalytic reaction vessel; a diesel engine, the exhaust pipe of the diesel engine being connected to the catalytic reaction vessel; a controller of the exhaust 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 are configured to be executed by the one or more processors, and the one or more programs include methods for executing any one of the methods described.

[0014] Applying the technical solution of the present application, when the engine meets the cold start condition, firstly, according to the actual exhaust mass flow rate, actual exhaust temperature, pre-start ambient temperature and actual pre-SCR temperature of the engine, the urea demand injection rate is determined, and the urea injection mechanism is controlled to enter the cold start injection mode, and urea is injected into the catalytic reaction container at the urea demand injection rate to treat the tail gas in the catalytic reaction container; then, when 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 present application determines the urea demand injection rate according to the ambient temperature before the engine starts and the actual parameters of the engine, and controls the urea injection mechanism to inject urea at the rate, so as to realize the early 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 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, and the conversion efficiency of nitrogen and oxygen in the tail gas under the low temperature start environment of the engine is high, and the problem of high nitrogen and oxygen emission content during the cold start process of the engine is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

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

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

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

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

[0020] Figure 5 A flow chart for determining a cold start pressure buildup enabling condition according to an embodiment of the present application is shown;

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

[0022] Figure 7A schematic diagram of a flow chart of urea required injection rate calculation provided according to an embodiment of the present application is shown;

[0023] Figure 8 A corresponding relationship diagram between exhaust heat and urea required injection rate during cold start provided according to an embodiment of the present application is shown;

[0024] Fig. 9 A flow chart for determining a cold start urea injection enabling condition according to an embodiment of the present application is shown;

[0025] Fig.10 A flow chart for determining a cold start urea injection termination condition according to an embodiment of the present application is shown;

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

[0027] The drawings include the following reference numerals:

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

[0029] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. 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 clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the accompanying drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are 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 cold start process of the engine. 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 in conjunction with 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 block diagram of a mobile terminal of 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 in the figure) a processor 102 (the processor 102 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA) and a memory 104 for storing data, wherein the mobile terminal may also include a transmission device 106 and an input / output device 108 for communication functions. It can be understood by those skilled in the art that Figure 1 The structure shown is for illustration only and does not limit the structure of the mobile terminal. Figure 1 More or fewer components as shown, or with Figure 1 Different configurations are shown.

[0035] The memory 104 can be used to store computer programs, for example, software programs and modules of application software, such as the computer program corresponding to the urea injection method in the embodiment of the present invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, the described method is implemented. The memory 104 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory 104 may further include a memory remotely arranged relative to the processor 102, and these remote memories may be connected to the mobile terminal via 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 a combination thereof. The transmission device 106 is used to receive or send data via a network. The specific example of the network may include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, referred to as 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 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0036] In this embodiment, 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 here.

[0037] Figure 2 is a flow chart of a urea injection method according to an embodiment of the present application. Figure 2 As shown, the method comprises the following steps:

[0038] Step S201, when the engine meets the cold start condition, 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 a cold start injection mode, wherein the cold start injection mode is a mode in which the urea injection mechanism injects urea into the catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is the actual inlet temperature of the catalytic reaction container;

[0039] Specifically, when the engine meets the cold start conditions, the urea injection mechanism operates in a cold start injection mode to inject urea. The urea injection mechanism may specifically be a urea pump. The actual exhaust mass flow rate is the actual mass flow rate 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 is started. The required urea injection rate is the amount of urea that needs to be injected per unit time. The catalytic reaction container is a container for performing selective catalytic reduction reaction. The catalytic reaction container has an SCR catalyst. The exhaust gas emitted by the engine is passed into the catalytic reaction container. Under the action of the catalyst, urea is reacted with NO in the exhaust gas to form an SCR catalyst. X The reaction generates non-toxic and pollution-free nitrogen and water, thus purifying the tail gas.

[0040] Step S202: When the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea.

[0041] Through the embodiment, when the engine meets the cold start condition, firstly, according to the actual exhaust mass flow rate, actual exhaust temperature, pre-start ambient temperature and actual pre-SCR temperature of the engine, the urea demand injection rate is determined, and the urea injection mechanism is controlled to enter the cold start injection mode, and urea is injected into the catalytic reaction container at the urea demand injection rate to treat the tail gas in the catalytic reaction container; then, when 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 urea demand injection rate is determined according to the ambient temperature before the engine is started and the actual parameters of the engine, and the urea injection mechanism is controlled to inject urea at the rate, so that the early injection of urea in the cold start environment is realized. Since the ammonia storage demand of the SCR catalyst is large under low temperature conditions, the ammonia decomposed by the injected urea can be basically adsorbed by the SCR catalyst, which increases the ammonia storage of the SCR catalyst in the catalytic reaction container, so that the catalytic efficiency of the SCR catalyst is high, and the conversion efficiency of nitrogen and oxygen in the tail gas under the low temperature start environment of the engine is high, and the problem of high nitrogen and oxygen emission content during the cold start process of the engine is solved.

[0042] In actual application, the SCR catalyst has the characteristics of large low-temperature ammonia storage and small high-temperature ammonia storage. When the engine is cold-started, the temperature before the SCR is low, and the ammonia storage demand of the SCR catalyst is very large. Under normal circumstances, the starting temperature of urea is high, resulting in insufficient ammonia reserves of the SCR catalyst during cold start, making the SCR efficiency low. The present application makes full use of the high low-temperature ammonia storage of the SCR catalyst and starts to inject urea during cold start, which can ensure that the ammonia reserves of the SCR catalyst of the engine are maintained at a preset level during cold start, without being affected by the problem of insufficient SCR ammonia storage caused by actual vehicle application, and realizes precise control of the ammonia reserves in the SCR catalyst during cold start. Although the urea injected during the cold start process cannot be completely decomposed to generate NH3, the decomposed NH3 can be completely adsorbed by the SCR catalyst, thereby effectively catalyzing the reduction of nitrogen oxides in the exhaust gas and reducing the cold nitrogen oxides emission content of the engine.

[0043] In order to further ensure that the urea demand injection rate that meets the cold start condition of the engine is obtained more accurately, in an optional scheme, 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 of the engine, including: determining the exhaust heat coefficient according to the actual exhaust mass flow, the actual temperature before SCR and a preset relationship, the preset relationship is a corresponding relationship between the exhaust mass flow, the temperature before SCR and the coefficient; determining the exhaust heat of the engine according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and the preset exhaust specific heat capacity; determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and the preset phase conversion heat absorption, the phase conversion heat absorption is determined according to the heat absorption of water in different phases and the heat absorption of urea in different phases during the urea hydrolysis process. In this embodiment, according to the exhaust heat and the hydrolysis heat absorption relationship during the urea hydrolysis process, the urea demand injection rate that matches the current working condition can be accurately calculated, so that the urea decomposition efficiency in the catalytic reaction container is high and the risk of urea crystallization is low, further ensuring a high urea utilization rate.

[0044] The heat absorbed by water in different phases includes the heat absorbed by liquid water when converted to gaseous water, the heat absorbed by gaseous water and the heat absorbed by liquid water; the heat absorbed by urea in different phases includes the heat absorbed by solid urea when converted to liquid urea, the heat absorbed by solid urea and the heat absorbed by liquid urea. The heat absorbed by phase conversion is specifically equal to the heat absorbed by water in different phases*0.675+the heat absorbed by urea in different phases*0.325.

[0045] It should be noted that, in the process of determining the required urea injection rate, when the actual exhaust mass flow rate, the actual exhaust temperature and the actual pre-SCR temperature change, the determined required urea injection rate also changes, that is, after the engine is cold started, the determined required urea injection rate is not constant, but changes with the actual temperature parameters and the actual exhaust parameters of the engine, which is beneficial to the conversion rate of urea to NH3 and reducing the amount of urea crystals.

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

[0047] Table 1

[0048]

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

[0050] Since the pre-SCR temperature is a key factor affecting the production of NH3 by urea, by looking up the table to determine the coefficient corresponding to the actual pre-SCR temperature, it is possible to avoid the problem of the determined urea demand injection rate being too large, which affects the increase in NH3 conversion and crystallization.

[0051] Furthermore, 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 the preset exhaust specific heat capacity, including: determining the temperature change 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; determining the exhaust heat as the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity according to the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity. Wherein, the exhaust specific heat capacity is a fixed value. In the embodiment, the current exhaust heat can be obtained efficiently and accurately by calculating the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity.

[0052] Further, the urea required injection rate is determined according to the exhaust heat, the exhaust heat coefficient and the preset phase conversion heat absorption, including: 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; determining the urea required injection rate as the urea hydrolysis absorption heat divided by the phase conversion heat absorption according to the urea hydrolysis absorption heat and the phase conversion heat absorption. In the embodiment, the exhaust heat is first multiplied by the exhaust heat coefficient to obtain the urea hydrolysis absorption heat, and then the urea hydrolysis absorption heat is divided by the phase conversion heat absorption to obtain the urea required injection rate, so that the current urea required injection rate can be obtained efficiently and accurately, 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 meets the cold start pre-ammonia storage condition when the coolant temperature of the engine is less than or equal to the first threshold, the engine oil temperature of the engine is less than or equal to the second threshold, the actual pre-SCR temperature is less than or equal to the third threshold, and the engine is powered on; determining 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 the fourth threshold, and the engine speed is greater than or equal to the preset speed, and the fourth threshold is greater than the third threshold. Through the conditions, it can be accurately determined whether the engine meets the cold start condition, that is, whether it is cold started.

[0054] Those skilled in the art can flexibly set the specific values ​​of the first threshold, the second threshold, the third threshold, the fourth threshold and the preset speed according to actual conditions. This application refers to the provisions in GB17691 and sets the first threshold, the second threshold and the third threshold to 30°C respectively. In addition, the fourth threshold is set to 50°C and the preset speed is set to 550rps.

[0055] In some other optional embodiments of the present application, after the urea injection mechanism is controlled to stop injecting urea, the method further includes: when the actual pre-SCR temperature is greater than the fifth threshold value and the speed is greater than or equal to the preset speed, the urea injection mechanism is controlled 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. That is to say, the urea injection strategy during cold start of the engine in the present application is independent of the urea injection strategy during non-cold start (i.e., normal operation) of the engine, and the urea injection during cold start will not affect the urea injection during normal operation; during cold start, the urea injection mechanism is controlled to enter the cold start injection mode, and during normal operation, the urea injection mechanism is controlled to enter the normal injection mode, further ensuring that the engine exhaust purification effect is better whether it is cold start or normal operation, which is conducive to controlling the consistency of nitrogen oxide emissions of the engine in cold state and non-cold state, and further achieving the effect that the nitrogen oxide emissions of the engine are low regardless of the state in which the engine is running.

[0056] Those skilled in the art can flexibly set the fifth threshold and the specific values ​​of the preset injection rate according to actual needs. The preset injection rate can be fixed or variable, and this application does not impose any specific restrictions on this.

[0057] In one embodiment, the fifth threshold may be 185°C.

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

[0059] According to some other optional schemes of the present application, after controlling the urea injection mechanism to enter the cold start injection mode, the method further includes: obtaining a target parameter, the target parameter including at least one of the following: cumulative urea injection amount, cumulative urea injection duration; determining whether the target parameter reaches a preset threshold; and determining that the urea injection termination condition is satisfied when the target parameter reaches the preset threshold. In this embodiment, by controlling the exit timing of the cold start urea injection mode, while further ensuring the reduction of the nitrogen oxide emission level of the engine exhaust during the cold start process, the risk of urea crystallization is greatly reduced.

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

[0061] In addition, the urea injection mechanism can adopt a single injection mode to inject urea into the catalytic reaction container according to the urea required injection rate; the urea injection mechanism can also adopt a multi-injection mode, such as double injection, to inject urea into the catalytic reaction container according to the urea required injection rate. The injected urea can be in the form of solid urea or liquid urea.

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

[0063] This embodiment relates to a specific urea injection method, such as Figure 3 As shown, the following steps are included:

[0064] Step S1: Power on the engine and enable cold start pre-ammonia storage. The specific process is as follows:

[0065] like Figure 4 As shown, the cold start pre-ammonia storage enabling conditions include: the engine is powered on, the engine coolant temperature is ≤30°C, the engine oil temperature is ≤30°C, and the pre-SCR temperature is ≤30°C; if the conditions are met, the engine cold start pre-ammonia storage is enabled.

[0066] Step S2: After determining that the cold start pre-ammonia storage is enabled, the cold start pressure buildup is enabled. The specific process is as follows:

[0067] like Figure 5 As shown, the cold start pressure buildup enabling conditions include: cold start pre-ammonia storage enabling, pre-SCR temperature ≥ 50°C, and engine speed ≥ 550rps; if the conditions are met, the engine cold start pressure buildup is enabled.

[0068] Step S3: Figure 6 As shown in the figure, after the cold start pressure build-up is enabled, the urea injection state changes to the injection preparation state; at the same time, the urea demand injection rate is calculated, such as Figure 7 As shown, 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 required injection rate * (0.675 * different phase water absorption heat + 0.325 * different phase urea absorption heat) (2);

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

[0072] Wherein, f is obtained by referring to Table 1 according to the actual exhaust mass flow rate and the actual pre-SCR temperature;

[0073] According to formulas (1), (2) and (3), the urea injection rate required is calculated in real time. Figure 8 An exemplary relationship diagram between exhaust heat and urea injection rate requirement during cold start is shown.

[0074] Step S4: After the urea injection amount is calculated, the cold start urea injection is enabled. The specific process is as follows:

[0075] like Fig. 9 As shown, the cold start urea injection enabling conditions include: cold start condition enabling, cold start pressure building enabling, and cold start urea injection mode enabling. When the cold start urea injection is enabled, urea injection starts.

[0076] Step S5: After judging that the cold start urea injection is enabled, the cold start urea injection termination condition is judged; if the condition is met, the cold start pre-ammonia storage is completed. The specific conditions are as follows: Fig.10 As shown, if the following conditions are met: the cold start urea injection time is accumulated for 300s or the cold start urea accumulation is ≥ 100g, the urea injection quantity requirement value is set to 0. The cold start urea injection is disabled.

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

[0078] The embodiment of the present application also provides a urea injection device. It should be noted that the urea injection device of the embodiment of the present application can be used to execute the urea injection method provided in the embodiment of the present application. The device is used to implement the embodiments and preferred implementations, and the descriptions that have been made will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware for preset functions. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

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

[0080] Fig.11 Schematic diagram of a urea injection device according to an embodiment of the present application. Fig.11 As shown, the device comprises:

[0081] The first determination unit 10 is used to determine the required urea injection rate according to the actual exhaust mass flow rate, the actual exhaust temperature, the pre-start ambient temperature and the actual pre-SCR temperature of the engine when the engine meets the cold start condition, and control the urea injection mechanism to enter the cold start injection mode, wherein the cold start injection mode is a mode in which the urea injection mechanism injects urea into the catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is the actual inlet temperature of the catalytic reaction container;

[0082] Specifically, when the engine meets the cold start conditions, the urea injection mechanism operates in a cold start injection mode to inject urea. The urea injection mechanism may specifically be a urea pump. The actual exhaust mass flow rate is the actual mass flow rate 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 is started. The required urea injection rate is the amount of urea that needs to be injected per unit time. The catalytic reaction container is a container for performing selective catalytic reduction reaction. The catalytic reaction container has an SCR catalyst. The exhaust gas emitted by the engine is passed into the catalytic reaction container. Under the action of the catalyst, urea is reacted with NO in the exhaust gas to form an SCR catalyst. X The reaction generates non-toxic and pollution-free nitrogen and water, thus purifying the tail gas.

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

[0084] Through 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, actual exhaust temperature, pre-start ambient temperature and actual pre-SCR temperature of the engine, and controls the urea injection mechanism to enter the cold start injection mode, injects urea into the catalytic reaction container at the urea demand injection rate, and treats 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 cold start of the engine, the application determines the urea demand injection rate according to the ambient temperature before the engine starts and the actual parameters of the engine, and controls the urea injection mechanism to inject urea at the rate, so as to realize the early 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 decomposed by the injected urea can be basically adsorbed by the SCR catalyst, which increases the ammonia storage of the SCR catalyst in the catalytic reaction container, so that the catalytic efficiency of the SCR catalyst is high, and the conversion efficiency of nitrogen and oxygen in the exhaust gas under the low temperature start environment of the engine is high, and the problem of high nitrogen and oxygen emission content during the cold start process of the engine is solved.

[0085] In actual application, the SCR catalyst has the characteristics of large low-temperature ammonia storage and small high-temperature ammonia storage. When the engine is cold-started, the temperature before the SCR is low, and the ammonia storage demand of the SCR catalyst is very large. Under normal circumstances, the starting temperature of urea is high, resulting in insufficient ammonia reserves of the SCR catalyst during cold start, making the SCR efficiency low. The present application makes full use of the high low-temperature ammonia storage of the SCR catalyst and starts to inject urea during cold start, which can ensure that the ammonia reserves of the SCR catalyst of the engine are maintained at a preset level during cold start, without being affected by the problem of insufficient SCR ammonia storage caused by actual vehicle application, and realizes precise control of the ammonia reserves in the SCR catalyst during cold start. Although the urea injected during the cold start process cannot be completely decomposed to generate NH3, the decomposed NH3 can be completely adsorbed by the SCR catalyst, thereby effectively catalyzing the reduction of nitrogen oxides in the exhaust gas and reducing the cold nitrogen oxides emission content of the engine.

[0086] In order to further ensure that the urea demand injection rate that meets the cold start condition of the engine is obtained more accurately, in an optional solution, the first determination unit includes: a first determination module, which is used to determine the exhaust heat coefficient according to the actual exhaust mass flow, the actual pre-SCR temperature and a preset relationship, wherein the preset relationship is a corresponding relationship between the exhaust mass flow, the pre-SCR temperature and the coefficient; a second determination module, which is used to determine 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 exhaust specific heat capacity; a third determination module, which is used to determine the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and the preset phase conversion heat absorption, wherein the phase conversion heat absorption is determined according to the heat absorption of water in different phases and the heat absorption of urea in different phases during the urea hydrolysis process. In this embodiment, according to the exhaust heat and the hydrolysis heat absorption relationship during the urea hydrolysis process, the urea demand injection rate that matches the current working condition can be accurately calculated, so that the urea decomposition efficiency in the catalytic reaction container is high and the risk of urea crystallization is low, further ensuring a high urea utilization rate.

[0087] The heat absorbed by water in different phases includes the heat absorbed by liquid water when converted to gaseous water, the heat absorbed by gaseous water and the heat absorbed by liquid water; the heat absorbed by urea in different phases includes the heat absorbed by solid urea when converted to liquid urea, the heat absorbed by solid urea and the heat absorbed by liquid urea. The heat absorbed by phase conversion is specifically equal to the heat absorbed by water in different phases*0.675+the heat absorbed by urea in different phases*0.325.

[0088] It should be noted that, in the process of determining the required urea injection rate, when the actual exhaust mass flow rate, the actual exhaust temperature and the actual pre-SCR temperature change, the determined required urea injection rate also changes, that is, after the engine is cold started, the determined required urea injection rate is not constant, but changes with the actual temperature parameters and the actual exhaust parameters of the engine, which is beneficial to the conversion rate of urea to NH3 and reducing the amount of urea crystals.

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

[0090] The first determination module may specifically include: a search submodule, which is used to search the exhaust mass flow rate that is the same as the actual exhaust mass flow rate and the actual pre-SCR temperature in the preset relationship according to the actual exhaust mass flow rate and the actual pre-SCR temperature, and the coefficient corresponding to the pre-SCR temperature that is the same as the actual pre-SCR temperature is the exhaust heat coefficient.

[0091] Since the pre-SCR temperature is a key factor affecting the production of NH3 by urea, by looking up the table to determine the coefficient corresponding to the actual pre-SCR temperature, it is possible to avoid the problem of the determined urea demand injection rate being too large, which affects the increase in NH3 conversion and crystallization.

[0092] Furthermore, the second determination module includes: a first determination submodule, for determining the temperature change as the difference between the actual exhaust temperature and the ambient temperature before starting according to the actual exhaust temperature and the ambient temperature before starting; a second determination submodule, for determining the exhaust heat as the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat according to the actual exhaust mass flow, the temperature change and the exhaust specific heat. Wherein, the exhaust specific heat is a fixed value. In the embodiment, by calculating the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat, the current exhaust heat can be obtained efficiently and accurately.

[0093] Further, the third determination module includes: a third determination submodule, for determining, according to the exhaust heat and the exhaust heat coefficient, the urea hydrolysis absorption heat as the product of the exhaust heat and the exhaust heat coefficient; and a fourth determination submodule, for determining, according to the urea hydrolysis absorption heat and the phase conversion absorption heat, the urea required injection rate as the urea hydrolysis absorption heat divided by the phase conversion absorption heat. In the embodiment, the exhaust heat is first multiplied by the exhaust heat coefficient to obtain the urea hydrolysis absorption heat, and then the urea hydrolysis absorption heat is divided by the phase conversion absorption heat to obtain the urea required injection rate, so that the current urea required injection rate can be obtained efficiently and accurately, and the urea decomposition rate is further ensured to be high and the urea crystallization amount is low.

[0094] Optionally, the device further includes: a second determination unit, used to determine that the engine meets the cold start pre-ammonia storage condition when the coolant temperature of the engine is less than or equal to the first threshold, the engine oil temperature of the engine is less than or equal to the second threshold, the actual pre-SCR temperature is less than or equal to the third threshold, and the engine is powered on; a third determination unit, used to determine that the engine meets the cold start condition when 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 the fourth threshold, and the engine speed is greater than or equal to the preset speed, and the fourth threshold is greater than the third threshold. Through the conditions, it can be accurately determined whether the engine meets the cold start condition, that is, whether it is cold started.

[0095] Those skilled in the art can flexibly set the specific values ​​of the first threshold, the second threshold, the third threshold, the fourth threshold and the preset speed according to actual conditions. This application refers to the provisions in GB17691 and sets the first threshold, the second threshold and the third threshold to 30°C respectively. In addition, the fourth threshold is set to 50°C and the preset speed is set to 550rps.

[0096] In some other optional embodiments of the present application, the device further includes: a second control unit, which is used to control the urea injection mechanism to enter a normal injection mode after controlling the urea injection mechanism to stop injecting urea, when the actual pre-SCR temperature is greater than the fifth threshold value and the speed is greater than or equal to the preset speed, wherein 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. That is to say, the urea injection strategy during cold start of the engine in the present application is independent of the urea injection strategy during non-cold start (i.e., normal operation) of the engine, and the urea injection during cold start will not affect the urea injection during normal operation; during cold start, the urea injection mechanism is controlled to enter the cold start injection mode, and during normal operation, the urea injection mechanism is controlled to enter the normal injection mode, further ensuring that the engine exhaust purification effect is better whether it is cold start or normal operation, which is conducive to controlling the consistency of nitrogen oxide emissions of the engine in cold state and non-cold state, and further achieving the effect that the nitrogen oxide emissions of the engine are lower regardless of the state in which the engine is running.

[0097] The urea injection device includes a processor and a memory, the first determination unit and the first control unit are stored in the memory as program units, and the processor executes the program units stored in the memory to implement corresponding functions. The modules are all located in the same processor; or the modules are located in different processors in any combination.

[0098] The processor includes a kernel, which retrieves the corresponding program unit from the memory. One or more kernels can be provided, and the problem of high nitrogen and oxygen emission content during the cold start process of the engine in the prior art can be at least solved by adjusting kernel parameters.

[0099] The memory may 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 RAM, and the memory includes at least one memory chip.

[0100] An embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored program, wherein when the program is executed, a device where the computer-readable storage medium is located is controlled to execute the urea injection method.

[0101] Specifically, the urea injection method includes:

[0102] Step S201, when the engine meets the cold start condition, 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 a cold start injection mode, wherein the cold start injection mode is a mode in which the urea injection mechanism injects urea into the catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is the actual inlet temperature of the catalytic reaction container;

[0103] Specifically, when the engine meets the cold start conditions, the urea injection mechanism operates in a cold start injection mode to inject urea. The urea injection mechanism may specifically be a urea pump. The actual exhaust mass flow rate is the actual mass flow rate 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 is started. The required urea injection rate is the amount of urea that needs to be injected per unit time. The catalytic reaction container is a container for performing selective catalytic reduction reaction. The catalytic reaction container has an SCR catalyst. The exhaust gas emitted by the engine is passed into the catalytic reaction container. Under the action of the catalyst, urea is reacted with NO in the exhaust gas to form an SCR catalyst. X The reaction generates non-toxic and pollution-free nitrogen and water, thus purifying the tail gas.

[0104] Step S202: When the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea.

[0105] Optionally, the required urea injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and the actual pre-SCR temperature of the engine, including: determining the exhaust heat coefficient according to the actual exhaust mass flow, the actual pre-SCR temperature and a preset relationship, the preset relationship being a correspondence 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 ambient temperature before starting and a preset exhaust specific heat capacity; determining the required urea injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption, the phase conversion heat absorption being determined according to the heat absorption of water in different phases and the heat absorption of urea in different phases during urea hydrolysis.

[0106] Optionally, the exhaust heat of the engine is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and a preset exhaust specific heat capacity, including: determining the temperature change as the difference between the actual exhaust temperature and the ambient temperature before starting according to the actual exhaust temperature and the ambient temperature before starting; determining the exhaust heat as the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity according to the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity; determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption capacity, including: 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; determining the urea demand injection rate as the urea hydrolysis absorption heat divided by the phase conversion heat absorption heat according to the urea hydrolysis absorption heat and the phase conversion heat absorption capacity.

[0107] Optionally, the method also includes: determining that the engine satisfies the cold start pre-ammonia storage condition when 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; and determining that the engine satisfies the cold start condition, and the fourth threshold is greater than the third threshold, 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 and the engine speed is greater than or equal to a preset speed.

[0108] Optionally, after controlling the urea injection mechanism to stop injecting urea, the method further includes: when the actual pre-SCR temperature is greater than a fifth threshold and the speed is greater than or equal to the preset speed, controlling the urea injection mechanism to enter a normal injection mode, wherein 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 is greater than the fourth threshold.

[0109] Optionally, when the engine meets the cold start condition, before controlling the urea injection mechanism to inject urea into the reaction container at the required urea injection rate, the method further includes: controlling the urea injection mechanism to operate to build up urea pressure.

[0110] Optionally, after controlling the urea injection mechanism to enter the cold start injection mode, the method further includes: acquiring a target parameter, the target parameter including at least one of the following: a cumulative urea injection amount, a cumulative urea injection duration; determining whether the target parameter reaches a preset threshold; and when the target parameter reaches the preset threshold, determining that the urea injection termination condition is satisfied.

[0111] An embodiment of the present invention provides an exhaust gas treatment system, comprising:

[0112] An exhaust gas treatment device comprises a catalytic reaction container and a urea injection mechanism, wherein the urea injection mechanism is connected to the catalytic reaction container; a diesel engine, wherein an exhaust pipe of the diesel engine is connected to the catalytic reaction container;

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

[0114] The controller in this article can be a server, PC, PAD, mobile phone, ECU, etc.

[0115] Specifically, the urea injection method includes:

[0116] Step S201, when the engine meets the cold start condition, 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 a cold start injection mode, wherein the cold start injection mode is a mode in which the urea injection mechanism injects urea into the catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is the actual inlet temperature of the catalytic reaction container;

[0117] Specifically, when the engine meets the cold start conditions, the urea injection mechanism operates in a cold start injection mode to inject urea. The urea injection mechanism may specifically be a urea pump. The actual exhaust mass flow rate is the actual mass flow rate 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 is started. The required urea injection rate is the amount of urea that needs to be injected per unit time. The catalytic reaction container is a container for performing selective catalytic reduction reaction. The catalytic reaction container has an SCR catalyst. The exhaust gas emitted by the engine is passed into the catalytic reaction container. Under the action of the catalyst, urea is reacted with NO in the exhaust gas to form an SCR catalyst. X The reaction generates non-toxic and pollution-free nitrogen and water, thus purifying the tail gas.

[0118] Step S202: When the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea.

[0119] Optionally, the required urea injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and the actual pre-SCR temperature of the engine, including: determining the exhaust heat coefficient according to the actual exhaust mass flow, the actual pre-SCR temperature and a preset relationship, the preset relationship being a correspondence 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 ambient temperature before starting and a preset exhaust specific heat capacity; determining the required urea injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption, the phase conversion heat absorption being determined according to the heat absorption of water in different phases and the heat absorption of urea in different phases during urea hydrolysis.

[0120] Optionally, the exhaust heat of the engine is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and a preset exhaust specific heat capacity, including: determining the temperature change as the difference between the actual exhaust temperature and the ambient temperature before starting according to the actual exhaust temperature and the ambient temperature before starting; determining the exhaust heat as the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity according to the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity; determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption capacity, including: 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; determining the urea demand injection rate as the urea hydrolysis absorption heat divided by the phase conversion heat absorption heat according to the urea hydrolysis absorption heat and the phase conversion heat absorption capacity.

[0121] Optionally, the method also includes: determining that the engine satisfies the cold start pre-ammonia storage condition when 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; and determining that the engine satisfies the cold start condition, and the fourth threshold is greater than the third threshold, 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 and the engine speed is greater than or equal to a preset speed.

[0122] Optionally, after controlling the urea injection mechanism to stop injecting urea, the method further includes: when the actual pre-SCR temperature is greater than a fifth threshold and the speed is greater than or equal to the preset speed, controlling the urea injection mechanism to enter a normal injection mode, wherein 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 is greater than the fourth threshold.

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

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

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

[0126] Step S201, when the engine meets the cold start condition, 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 a cold start injection mode, wherein the cold start injection mode is a mode in which the urea injection mechanism injects urea into the catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is the actual inlet temperature of the catalytic reaction container;

[0127] Step S202: When the urea injection termination condition is met, the urea injection mechanism is controlled to stop injecting urea.

[0128] Optionally, the required urea injection rate is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and the actual pre-SCR temperature of the engine, including: determining the exhaust heat coefficient according to the actual exhaust mass flow, the actual pre-SCR temperature and a preset relationship, the preset relationship being a correspondence 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 ambient temperature before starting and a preset exhaust specific heat capacity; determining the required urea injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption, the phase conversion heat absorption being determined according to the heat absorption of water in different phases and the heat absorption of urea in different phases during urea hydrolysis.

[0129] Optionally, the exhaust heat of the engine is determined according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting and a preset exhaust specific heat capacity, including: determining the temperature change as the difference between the actual exhaust temperature and the ambient temperature before starting according to the actual exhaust temperature and the ambient temperature before starting; determining the exhaust heat as the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity according to the actual exhaust mass flow, the temperature change and the exhaust specific heat capacity; determining the urea demand injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption capacity, including: 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; determining the urea demand injection rate as the urea hydrolysis absorption heat divided by the phase conversion heat absorption heat according to the urea hydrolysis absorption heat and the phase conversion heat absorption capacity.

[0130] Optionally, the method also includes: determining that the engine satisfies the cold start pre-ammonia storage condition when 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; and determining that the engine satisfies the cold start condition, and the fourth threshold is greater than the third threshold, 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 and the engine speed is greater than or equal to a preset speed.

[0131] Optionally, after controlling the urea injection mechanism to stop injecting urea, the method further includes: when the actual pre-SCR temperature is greater than a fifth threshold and the speed is greater than or equal to the preset speed, controlling the urea injection mechanism to enter a normal injection mode, wherein 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 is greater than the fourth threshold.

[0132] Optionally, when the engine meets the cold start condition, before controlling the urea injection mechanism to inject urea into the reaction container at the required urea injection rate, the method further includes: controlling the urea injection mechanism to operate to build up urea pressure.

[0133] Optionally, after controlling the urea injection mechanism to enter the cold start injection mode, the method further includes: acquiring a target parameter, the target parameter including at least one of the following: a cumulative urea injection amount, a cumulative urea injection duration; determining whether the target parameter reaches a preset threshold; and when the target parameter reaches the preset threshold, determining that the urea injection termination condition is satisfied.

[0134] Obviously, those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than herein, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0135] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0136] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0137] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0138] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

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

[0140] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0141] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. 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 technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0142] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

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

[0144] The urea injection method of the present application, when the engine meets the cold start condition, firstly determines the urea demand injection rate according to the actual exhaust mass flow, actual exhaust temperature, pre-start ambient temperature and actual pre-SCR temperature of the engine, and controls the urea injection mechanism to enter the cold start injection mode, injects urea into the catalytic reaction container at the urea demand injection rate, and treats the tail gas in the catalytic reaction container; then, when the urea injection termination condition is met, controls the urea injection mechanism to stop injecting urea. In the case of cold start of the engine, the present application determines the urea demand injection rate according to the ambient temperature before the engine starts and the actual parameters of the engine, and controls the urea injection mechanism to inject urea at the rate, so as to realize the early 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 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, and the conversion efficiency of nitrogen and oxygen in the tail gas under the low temperature start environment of the engine is high, and the problem of high nitrogen and oxygen emission content during the cold start process of the engine is solved.

[0145] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A urea injection method, characterized in that: include: When the engine meets the cold start condition, 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 a cold start injection mode, wherein the cold start injection mode is a mode in which the urea injection mechanism injects urea into the catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is the actual inlet temperature of the catalytic reaction container; When the urea injection termination condition is satisfied, the urea injection mechanism is controlled to stop injecting urea.

2. The method according to claim 1, characterized in that Determining the required urea injection rate according to the actual exhaust mass flow, the actual exhaust temperature, the ambient temperature before starting, and the actual pre-SCR temperature of the engine includes: Determining an exhaust heat coefficient according to the actual exhaust mass flow, the actual pre-SCR temperature and a preset relationship, wherein the preset relationship is 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 ambient temperature before starting, and a preset exhaust specific heat capacity; The required urea injection rate is determined according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion endothermic heat, wherein the phase conversion endothermic heat is determined according to the endothermic heat of water in different phases and the endothermic heat of urea in different phases during urea hydrolysis.

3. The method according to claim 2, characterized in that 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 exhaust specific heat capacity includes: According to the actual exhaust temperature and the ambient temperature before starting, determining the temperature change as the difference between the actual exhaust temperature and the ambient temperature before starting; According to the actual exhaust mass flow, the temperature change and the exhaust specific heat, the exhaust heat is determined as the product of the actual exhaust mass flow, the temperature change and the exhaust specific heat. Determining the required urea injection rate according to the exhaust heat, the exhaust heat coefficient and a preset phase conversion heat absorption amount includes: According to the exhaust heat and the exhaust heat coefficient, determining the urea hydrolysis absorption heat as the product of the exhaust heat and the exhaust heat coefficient; According to the urea hydrolysis absorption heat and the phase conversion absorption heat, the required urea injection rate is determined as the urea hydrolysis absorption heat divided by the phase conversion absorption heat.

4. The method according to claim 1, characterized in that: The method further comprises: When the coolant temperature of the engine is less than or equal to a first threshold, the engine 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 meets the cold start pre-ammonia storage 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, and the engine speed is greater than or equal to a preset speed, it is determined that the engine satisfies the cold start condition and the fourth threshold is greater than the third threshold.

5. The method according to claim 4, characterized in that After controlling the urea injection mechanism to stop injecting urea, the method further includes: When the actual pre-SCR temperature is greater than a fifth threshold and the speed is greater than or equal to the preset speed, the urea injection mechanism is controlled to enter a normal injection mode, wherein 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 is greater than the fourth threshold.

6. The method according to any one of claims 1 to 5, characterized in that When the engine meets the cold start condition, before controlling the urea injection mechanism to inject urea into the reaction container at the required urea injection rate, the method further includes: The urea injection mechanism is controlled to operate so as to build up urea pressure.

7. The method according to any one of claims 1 to 5, characterized in that After controlling the urea injection mechanism to enter the cold start injection mode, the method further includes: Acquiring target parameters, wherein the target parameters include at least one of the following: cumulative urea injection amount and cumulative urea injection time; Determining whether the target parameter reaches a preset threshold; When the target parameter reaches the preset threshold, it is determined that the urea injection termination condition is met.

8. A urea injection device, characterized in that: include: a first determining unit, for determining a required urea 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 when the engine meets a cold start condition, 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 injects urea into a catalytic reaction container at the required urea injection rate, and the actual pre-SCR temperature is an actual inlet temperature of the catalytic reaction container; The first control unit is used to control the urea injection mechanism to stop injecting urea when a urea injection termination condition is met.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the method according to any one of claims 1 to 7.

10. An exhaust gas treatment system, characterized in that: include: An exhaust gas treatment device comprises a catalytic reaction container and a urea injection mechanism, wherein the urea injection mechanism is connected to the catalytic reaction container; A diesel engine, wherein an exhaust pipe of the diesel engine is in communication with the catalytic reaction vessel; The exhaust gas treatment device comprises a controller, one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include methods for executing any one of claims 1 to 7.

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