Control Method, Device and Storage Medium for Preventing Crystallization of Diesel Engine Aftertreatment Mixer

Abstract

The present invention provides a control method for preventing crystallization of a post-treatment mixer of a diesel engine, comprising the following steps: Step S1, calculating the airflow resistance passing through the mixer; Step S2, determining a first flow resistance value, a second flow resistance value, and a third flow resistance value corresponding to a slight crystallization amount, a medium crystallization amount, and a severe crystallization amount of the mixer; wherein the first flow resistance value < the second flow resistance value < the third flow resistance value; Step S3, judging the crystallization situation through the flow resistance of the mixer and taking corresponding control measures; when the first flow resistance value < the flow resistance < the second flow resistance value, the conversion efficiency of the SCR is also used to assist in judging whether measures need to be taken. The present invention can, during the normal operation of the engine, monitor the crystallization situation of the mixer in real time, and when the crystallization amount of the mixer increases, timely remove the mixed crystallization, thereby ensuring the normal operation of the SCR system.

Description

Technical Field

[0001] The present invention relates to the field of diesel engine exhaust aftertreatment, and in particular to a control method for preventing crystallization of a mixer in diesel engine aftertreatment. Background Art

[0002] At present, the mainstream technical solution for national VI aftertreatment is the DOC+DPF+SCR route. Among them, the SCR system is mainly used to remove NOx generated in diesel engine exhaust. The SCR system usually includes components such as a mixer, an SCR catalyst, a urea nozzle, and a urea pump. The main function of the SCR mixer is to fully mix the exhaust gas discharged from the diesel engine and NH3 formed by the hydrolysis of urea sprayed by the urea nozzle to form a relatively uniform mixed gas. When these uniformly mixed gases pass through the SCR catalyst, under the reduction action of the catalyst, NOx compounds can be reduced to N2 and H2O.

[0003] With the implementation of the national VI regulations, in order to further reduce the emission of NOx, the urea injection amount of most national VI diesel engine aftertreatment systems is over-injected, that is, urea is injected with an ammonia-nitrogen ratio greater than 1. After long-term operation like this, it may cause crystallization of the mixer. After serious crystallization of the mixer, it will affect the mixing effect of the mixer, thereby further affecting the conversion efficiency of the SCR system for NOx, and will also cause an increase in the back pressure of the engine, reduce the power of the engine, and increase the fuel consumption of the engine. Summary of the Invention

[0004] To solve at least one technical problem in the prior art, embodiments of the present invention provide a control method, device, and storage medium for preventing crystallization of a mixer in diesel engine aftertreatment. The purpose is to monitor the crystallization situation of the mixer in real time during the normal operation of the engine, and when the crystallization amount of the mixer increases, timely remove the mixed crystals, so as to ensure the normal operation of the SCR system. To achieve the above technical objectives, the technical solutions adopted in the embodiments of the present invention are as follows:

[0005] In a first aspect, embodiments of the present invention provide a control method for preventing crystallization of a mixer in diesel engine aftertreatment, including the following steps:

[0006] Step S1, calculate the airflow resistance passing through the mixer;

[0007] Step S2, determine the first flow resistance value, the second flow resistance value, and the third flow resistance value corresponding to the slight crystallization amount, medium crystallization amount, and severe crystallization amount of the mixer; where the first flow resistance value < the second flow resistance value < the third flow resistance value;

[0008] Step S3, judge the crystallization situation through the flow resistance of the mixer and take corresponding control measures.

[0009] Further, in step S1,

[0010] Air flow resistance through the mixer = Differential pressure measured by the differential pressure sensor / Exhaust gas volume flow rate through the mixer;

[0011] Exhaust gas volume flow rate through the mixer = Exhaust gas mass flow rate / Exhaust gas density.

[0012] Further, step S3 specifically includes:

[0013] Step S301, if the flow resistance ≤ the first flow resistance value, it is judged that the crystallization amount of the mixer is small and will not affect the normal operation of the SCR system, and the engine runs normally without taking any measures;

[0014] Step S302, if the first flow resistance value < flow resistance < the second flow resistance value, it is necessary to judge the conversion efficiency of the SCR;

[0015] If the SCR conversion efficiency ≥ 85%, no measures are taken;

[0016] If 70% < SCR conversion efficiency < 85%, treatment is required. At this time, the engine enters the first temperature increase mode to increase the engine temperature so that the temperature after the mixer > 400°C, and the crystallization is burned off by high temperature. The operation duration of the first temperature increase mode is controlled within 30 minutes. When the operation duration of the first temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance;

[0017] If the SCR conversion efficiency ≤ 70%, treatment is required. At this time, the engine enters the second temperature increase mode to increase the engine temperature so that the temperature after the mixer > 550°C, and the crystallization is burned off by high temperature. The operation duration of the second temperature increase mode is controlled within 30 minutes. When the operation duration of the second temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance;

[0018] Step S303, if the second flow resistance value < flow resistance < the third flow resistance value, treatment is required. At this time, the engine enters the second temperature increase mode to increase the engine temperature so that the temperature after the mixer > 550°C, and the crystallization is burned off by high temperature. The operation duration of the second temperature increase mode is controlled within 30 minutes. When the operation duration of the second temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance;

[0019] Step S304, if the flow resistance ≥ the third flow resistance value, treatment is required. At this time, the engine enters the third temperature increase mode to increase the engine temperature so that the temperature after the mixer > 600°C, and the crystallization is burned off by high temperature. The operation duration of the third temperature increase mode is controlled within 30 minutes. When the operation duration of the third temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance.

[0020] Second aspect, an embodiment of the present invention provides a control device for preventing crystallization of a post-treatment mixer of a diesel engine, including:

[0021] A memory storing a computer program;

[0022] A processor configured to run the computer program, and when the computer program runs, it executes the steps of the method described above.

[0023] Third aspect, an embodiment of the present invention provides a storage medium storing a computer program, and the computer program is configured to execute the steps of the method described above when running.

[0024] The beneficial effects brought by the technical solution provided by the embodiment of the present invention are:

[0025] 1. During the operation of the whole vehicle, the urea crystallization situation in the mixer can be judged in real time.

[0026] 2. To remove the crystallization, it is not necessary to remove the mixer, and the mixer crystallization can be removed during the operation of the whole vehicle.

[0027] 3. By monitoring the mixer crystallization situation in real time, when the mixer crystallization amount is not high, the crystallization can be removed at high temperature, avoiding problems such as a decrease in the efficiency of the SCR system, an increase in the engine back pressure, and an increase in fuel consumption caused by an increase in the mixer crystallization amount. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of the exhaust gas post-treatment system in the embodiment of the present invention.

[0029] Figure 2 It is a flowchart of the control method in the embodiment of the present invention. Detailed Embodiments

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] In the description of the embodiment of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0032] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two components. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] In the embodiments of the present invention, the engine refers to a diesel engine.

[0035] As Figure 1 shown, in this embodiment, an exhaust gas after-treatment system includes a DOC, a DPF, a mixer, and an SCR connected in sequence; the intake end of the pressure sensor 2 is connected to the intake end upstream of the mixer through the intake duct 1, and the exhaust end of the pressure sensor 2 is connected to the exhaust end downstream of the mixer through the exhaust duct 3; thus, the pressure sensor 2 can sense the pressure change at both ends of the mixer; a post-temperature sensor 4 is also provided downstream of the mixer, and the post-temperature sensor 4 can monitor the temperature change downstream of the mixer;

[0036] A control method for preventing crystallization of a diesel engine post-treatment mixer proposed in the embodiments of the present invention, as Figure 2 shown, includes the following steps:

[0037] Step S1, calculate the airflow resistance through the mixer;

[0038] The airflow resistance through the mixer = the pressure difference measured by the differential pressure sensor / the exhaust gas volume flow rate flowing through the mixer;

[0039] The exhaust gas volume flow rate flowing through the mixer = the exhaust gas mass flow rate / the exhaust gas density;

[0040] Step S2, determine the first flow resistance value, the second flow resistance value, and the third flow resistance value corresponding to the slight crystallization amount, the medium crystallization amount, and the severe crystallization amount of the mixer; where the first flow resistance value < the second flow resistance value < the third flow resistance value;

[0041] The crystallization amount in the mixer is different, and the flow resistance of the gas flow passing through the mixer is also different. When there is no crystallization in the mixer, the flow resistance value of the gas flow passing through the mixer is small. When serious crystallization occurs in the mixer, the flow resistance value of the gas flow passing through the mixer is large. In order to accurately measure the relationship curve between the crystallization amount and the flow resistance value of the mixer, it is necessary to measure the flow resistance values corresponding to different crystallization amounts of the mixer in advance. For example:

[0042]

[0043] In this embodiment, the slight crystallization amount, medium crystallization amount and serious crystallization amount are taken as 30g, 50g and 100g respectively. When the crystallization amount of the mixer > 100g, it is considered that the conversion efficiency of the SCR system will be affected;

[0044] Step S3, judge the crystallization situation according to the flow resistance of the mixer and take corresponding control measures;

[0045] Step S301, if the flow resistance ≤ the first flow resistance value, it is judged that the crystallization amount of the mixer is small and will not affect the normal operation of the SCR system. The engine runs normally and no measures are taken;

[0046] Step S302, if the first flow resistance value < the flow resistance < the second flow resistance value, it is necessary to judge the conversion efficiency of the SCR; the purpose of judging the conversion efficiency of the SCR is to see whether the crystallization of the mixer affects the performance of the SCR. If the SCR conversion efficiency is high at this time, it means that the crystallization has little effect on the performance of the SCR system and no treatment is required; if the SCR conversion efficiency is low at this time, it means that the crystallization has a great impact on the performance of the SCR system and treatment is required;

[0047] If the SCR conversion efficiency ≥ 85%, it is considered that the SCR conversion efficiency is high at this time, and it is considered that there is almost no crystallization in the mixer, indicating that the crystallization has little effect on the performance of the SCR system. Therefore, the engine runs normally and no measures are taken;

[0048] If 70% < the SCR conversion efficiency < 85%, it is considered that the SCR conversion efficiency is medium at this time, and it is considered that there is some crystallization in the mixer, which has a certain impact on the performance of the SCR system and treatment is required. At this time, the engine enters the first temperature raising mode to raise the engine temperature so that the temperature after the mixer > 400°C, and the crystallization is burned off by high temperature. The running time of the first temperature raising mode is controlled within 30 minutes. When the running time of the first temperature raising mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance;

[0049] If the SCR conversion efficiency ≤ 70%, it is considered that the SCR conversion efficiency is low at this time, and it is considered that there is more crystallization in the mixer, which has a more serious impact on the performance of the SCR system and needs to be processed. At this time, the engine enters the second temperature increase mode to increase the engine temperature so that the temperature after the mixer > 550°C, and the crystallization is burned off by high temperature. The operation duration of the second temperature increase mode is controlled within 30 minutes. When the operation duration of the second temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to perform the flow resistance judgment;

[0050] In some embodiments, NOx sensors can be respectively arranged upstream and downstream of the SCR to measure the NOx values upstream and downstream of the SCR, and then converted into the SCR conversion efficiency;

[0051] Step S303, if the second flow resistance value < flow resistance < the third flow resistance value, it is considered that there is more crystallization in the mixer, which has a more serious impact on the performance of the SCR system and needs to be processed. At this time, the engine enters the second temperature increase mode to increase the engine temperature so that the temperature after the mixer > 550°C, and the crystallization is burned off by high temperature. The operation duration of the second temperature increase mode is controlled within 30 minutes. When the operation duration of the second temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to perform the flow resistance judgment;

[0052] Step S304, if the flow resistance ≥ the third flow resistance value, it is considered that there is a large amount of crystallization in the post-mixer at this time, which has a serious impact on the performance of the SCR system and needs to be processed. At this time, the engine enters the third temperature increase mode to increase the engine temperature so that the temperature after the mixer > 600°C, and the crystallization is burned off by high temperature. The operation duration of the third temperature increase mode is controlled within 30 minutes. When the operation duration of the third temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to perform the flow resistance judgment.

[0053] An embodiment of the present invention also provides a control device for preventing crystallization of a diesel engine after-treatment mixer, including: a processor and a memory; the processor and the memory communicate with each other, for example, connected and communicate with each other through a communication bus; a computer program is stored in the memory; the processor is used to run the computer program, and when the computer program runs, it executes the steps of the method described above; the processor can be a CPU or other general-purpose processors, a digital signal processor (Digital Signal Processor, DSP), an application specific integrated circuit (Application Specific Integrated Circuit, ASIC), a field programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., or a combination of the above types of chips or circuits; the memory can include volatile memory, such as random access memory; the memory can also include non-volatile memory, such as flash memory, hard disk or solid state drive; the memory can also include a combination of the above types of memory;

[0054] An embodiment of the present invention also provides a storage medium, in which a computer program is stored, and the computer program is configured to execute the steps of the method described above when running; the storage medium can be a magnetic disk, an optical disc, a read-only memory (Read-Only Memory, ROM), a random access memory (Random Access Memory, RAM), a flash memory (Flash Memory), a hard disk (HardDisk Drive, abbreviation: HDD) or a solid state drive (Solid-StateDrive, SSD), etc.; the storage medium can also include a combination of the above types of memory.

[0055] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A control method for preventing crystallization of the post-treatment mixer of a diesel engine, characterized in that, It includes the following steps: Step S1, calculate the air flow resistance through the mixer; Step S2, determine the first flow resistance value, the second flow resistance value, and the third flow resistance value corresponding to the slight crystallization amount, medium crystallization amount, and severe crystallization amount of the mixer; where the first flow resistance value < the second flow resistance value < the third flow resistance value; Step S3, judge the crystallization situation based on the flow resistance through the mixer and take corresponding control measures; The air flow resistance through the mixer = the pressure difference measured by the pressure difference sensor / the exhaust gas volume flow rate flowing through the mixer; The exhaust gas volume flow rate flowing through the mixer = the exhaust gas mass flow rate / the exhaust gas density; Step S3 specifically includes: Step S301, if the flow resistance ≤ the first flow resistance value, it is judged that the crystallization amount of the mixer is small and will not affect the normal operation of the SCR system, the engine operates normally, and no measures are taken; Step S302, if the first flow resistance value < the flow resistance < the second flow resistance value, it is necessary to judge the conversion efficiency of the SCR; If the SCR conversion efficiency ≥ 85%, no measures are taken; If 70% < the SCR conversion efficiency < 85%, treatment is required. At this time, the engine enters the first temperature increase mode to increase the engine temperature so that the temperature after the mixer > 400°C, and the crystallization is burned off by high temperature. The operation duration of the first temperature increase mode is controlled within 30 minutes. When the operation duration of the first temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance; If the SCR conversion efficiency ≤ 70%, treatment is required. At this time, the engine enters the second temperature increase mode to increase the engine temperature so that the temperature after the mixer > 550°C, and the crystallization is burned off by high temperature. The operation duration of the second temperature increase mode is controlled within 30 minutes. When the operation duration of the second temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance; Step S303, if the second flow resistance value < the flow resistance < the third flow resistance value, treatment is required. At this time, the engine enters the second temperature increase mode to increase the engine temperature so that the temperature after the mixer > 550°C, and the crystallization is burned off by high temperature. The operation duration of the second temperature increase mode is controlled within 30 minutes. When the operation duration of the second temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance; Step S304, if the flow resistance ≥ the third flow resistance value, treatment is required. At this time, the engine enters the third temperature increase mode to increase the engine temperature so that the temperature after the mixer > 600°C, and the crystallization is burned off by high temperature. The operation duration of the third temperature increase mode is controlled within 30 minutes. When the operation duration of the third temperature increase mode exceeds 30 minutes, the engine automatically enters the normal mode of operation and continues to judge the flow resistance.

2. A control device for preventing crystallization of a post-treatment mixer of a diesel engine, characterized in that, It includes: A memory that stores a computer program; A processor for running the computer program, and when the computer program runs, it executes the steps of the method according to claim 1.

3. A storage medium, characterized in that The storage medium stores a computer program, and the computer program is configured to execute the steps of the method according to claim 1 when running.

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