Method for predicting dust deposition in flow channel of virtual impact separator based on numerical analysis

Abstract

The invention relates to a method for predicting dust deposition in a flow channel of a virtual impact separator based on numerical analysis, and belongs to the technical field of dust separation, and the method comprises the following steps: S1, collecting operation parameters of the virtual impact separator for continuous dust separation; s2, according to the physical characteristics of the particles and the runner characteristics of the virtual impact separator, establishing a PBE equation of movement and deposition of the particles in the runner; s3, calculating the deposition rate of the particles in the flow channel of the virtual impact separator; s4, the PBE equation is solved, and the particle deposition amount in the flow channel of the virtual impact separator is calculated; and S5, comparing the calculated particle deposition amount with the maximum allowable deposition amount of the virtual impact separator to obtain a cleaning and maintenance period.

Description

Technical Field

[0001] The invention belongs to the technical field of dust separation, and relates to a method for predicting dust deposition in a flow channel of a virtual impact separator based on numerical analysis. Background Art

[0002] The virtual impact separator is a common continuous particle separation device, which is widely used in the fields of chemical industry, pharmaceutical industry, food processing, atmospheric particle detection, mine respirable dust separation detection, etc. The virtual impact separator uses high-speed airflow to separate the particles and gas in the dust-laden airflow in a certain proportion, thereby realizing the classification and collection of particles. However, the problem of particle deposition in the flow channel has always been a key factor affecting the separation efficiency and the stability of equipment operation. Too frequent maintenance will cause the continuous separation advantage of the virtual impact separator to be lost. If the maintenance cycle is too long, particles will be deposited, which will cause the characteristic structure size of the flow channel to change, thereby affecting the separation efficiency. In severe cases, it may cause blockage of the flow channel and even damage to the equipment. Traditional particle deposition prediction methods mainly rely on experimental observation or empirical judgment, manually dismantling the virtual impact separator structural components regularly, observing the particle contamination deposition in the flow channel, and then determining whether to perform flow channel cleaning and maintenance based on experience. These methods have the following shortcomings:

[0003] 1) The operating conditions of the virtual impact separator are changeable. Changes in factors such as the concentration of the dust-laden airflow to be separated and the humidity of the airflow will bring uncertainty to the flow channel contamination and particle deposition of the virtual impact separator. It is difficult to accurately determine the maintenance time with traditional experience;

[0004] 2) During the disassembly and maintenance of the virtual impact separator, the separator must stop running. Inaccurate maintenance time is not conducive to the continuous separation advantage of the virtual impact separator;

[0005] 3) Manual regular disassembly results in high labor intensity, and repeated disassembly may cause the separation efficiency of the virtual impact separator to deviate or even be damaged. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for predicting dust deposition in the flow channel of a virtual impact separator based on numerical analysis, which can simply and conveniently predict the particle deposition situation in the flow channel according to the operating conditions of the separator, reduce the uncertainty caused by human experience, and provide accurate suggestions for the maintenance of the separator.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for predicting dust deposition in a virtual impact separator flow channel based on numerical analysis comprises the following steps:

[0009] S1: Collect the operating parameters of the virtual impact separator for continuous dust separation;

[0010] S2: According to the physical properties of the particles and the flow channel characteristics of the virtual impact separator, the PBE equation for the movement and deposition of particles in the flow channel is established;

[0011] S3: Calculate the deposition rate of particles in the virtual impact separator flow channel;

[0012] S4: solving the PBE equation to calculate the particle deposition amount in the virtual impact separator flow channel;

[0013] S5: Compare the calculated particle deposition amount with the maximum allowable deposition amount of the virtual impact separator to obtain a cleaning maintenance cycle.

[0014] Furthermore, the operation parameters in step S1 include flow channel characteristic parameters, particle characteristic parameters and airflow characteristic parameters;

[0015] The flow channel characteristic parameters are geometric structure parameters of the virtual impact separator, including characteristic diameter D and characteristic length L;

[0016] The particle characteristic parameters include particle concentration C, density ρ p ;

[0017] The airflow characteristic parameters include the working point flow rate Q of the virtual impact separator and the ambient humidity RH.

[0018] Further, the step S2 specifically includes the following steps:

[0019] S21: Define the diameter d of the particle and the number density function n(d, t, y) of the particle, where t is the time and y is the position along the flow channel. Calculate the flow velocity U(t, y) inside the virtual impact separator using formula (1):

[0020]

[0021] Where Q(t,y) is the flow rate at position y of the virtual impactor separator at time t, which is equal to the flow rate at the working point of the virtual impactor separator;

[0022] S22: Considering the generation, transport, fragmentation and deposition of particles, the PBE equation is established:

[0023]

[0024] Where n(d,t,y) is the number density of particles with diameter d at position y and time t; represents the change of particle number density of the virtual impact separator due to time change; U(t,y) is the fluid velocity; represents the transport of particles along the flow channel caused by fluid flow in the virtual impact separator; kd (d, D, U) is the particle deposition rate due to particle inertia effect and diffusion effect;

[0025] Assuming the particles are spherical, their number density

[0026]

[0027] Where C is the mass concentration of dust; ρ p is the particle density; d is the particle diameter.

[0028] Further, the step S3 specifically includes the following steps:

[0029] S31: Calculation of the sedimentation rate adjustment factor f for humidity effects h :

[0030] f h =1+α×RH (4)

[0031] Where α is the coefficient of change of deposition rate when humidity increases by 1%; RH is the current humidity test value;

[0032] S32: Establishing deposition rate calculation function k d (d,D,U,RH)

[0033]

[0034] Where k d (d, D, U, RH) is the particle deposition rate; d is the particle diameter; D is the flow channel diameter; U is the flow rate of the fluid; RH is the relative humidity; μ is the dynamic viscosity of the air; ρ is the particle density.

[0035] Further, the step S4 specifically includes the following steps:

[0036] S41: Create particle size and flow channel size grids, initialize particle number density matrix and deposition matrix;

[0037] S42: Use the finite difference method to discretize the time and space derivatives, use forward differences to represent the time derivatives, and use backward differences or central differences to represent the space derivatives, and obtain the discretized PBE equations;

[0038] S43: Starting from the initial conditions, the time step is iterated step by step, the particle number density n(d, t, y) is updated, and the real-time values ​​of the ambient dust concentration C and ambient humidity RH are obtained and updated. At each time step, the particle number density of the new time step is calculated according to the discretized PBE equation;

[0039] S44: Integrate the logarithmic density n(d, t, y) along the length of the flow channel to calculate the particle deposition amount D on the flow channel wallt .

[0040] Furthermore, in step S5, the maximum allowable deposition amount D a According to the test, when the structure size of the virtual impact separator and the flow rate at the working point are constant, this value is a constant; when D t ≥D a When , it is considered that the separation performance of the virtual impact separator deviates from the maximum allowable error and needs to be cleaned and maintained.

[0041] The beneficial effects of the present invention are as follows: the present invention realizes the calculation of the deposition amount of particles in the flow channel of the virtual impact separator in different time periods through a numerical calculation method. Thus, the cleaning and maintenance cycle is determined, and the accuracy and convenience of the prediction are improved compared with the traditional empirical method. The prediction period of the present invention does not affect the normal operation of the virtual impact separator, which saves time and effort compared with manual disassembly and inspection, and gives full play to the advantages of the virtual impact separator for continuous separation of particles, while reducing the probability of damage to the separator due to frequent disassembly. The prediction method can realize dynamic prediction of the deposition amount based on particle concentration and ambient humidity, two important factors that affect the deposition of particles in the flow channel of the virtual impact separator.

[0042] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0044] Figure 1 The flowchart of the dust deposition prediction method in the flow channel of the virtual impact separator based on numerical analysis;

[0045] Figure 2 The distribution diagram of the deposition amount at different continuous operation times under the working conditions in Table 1, where (a) is t=1h, (b) is t=24h, (c) is t=120h, (d) is t=240h, and (e) is t=480h. DETAILED DESCRIPTION

[0046] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0047] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0048] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0049] like Figure 1 As shown, the present invention provides a method for predicting dust deposition in a virtual impact separator flow channel based on numerical analysis, comprising the following steps:

[0050] S1: Collect the operating parameters of the virtual impact separator for continuous dust separation, including flow channel characteristic parameters, particle characteristic parameters and airflow characteristic parameters.

[0051] ① The flow channel characteristic parameters are the main geometric structural parameters of the virtual impact separator, including characteristic diameter D and characteristic length L. They are obtained through the product specification drawings of the virtual impact separator, or through physical measurement of the separator.

[0052] ② The particle characteristic parameters are mainly particle concentration C, density ρ p The concentration C can be measured by a dust concentration sensor; the density can be measured by a true density meter. When the particle composition is constant, the density is usually a constant.

[0053] ③ The airflow characteristic parameters include the working point flow rate Q of the virtual impact separator and the ambient humidity RH. The working point flow rate Q of the virtual impact separator is obtained through the separator nameplate or instruction manual; the ambient humidity RH is measured by an ambient humidity measuring instrument.

[0054] S2: According to the physical properties of the particles and the flow characteristics of the virtual impact separator, the PBE equation for the movement and deposition of particles in the flow channel is established. The specific steps are:

[0055] ① Define the particle size d. Take coal mine respirable dust as an example and take its cut particle size, i.e., aerodynamic diameter d = 5 μm; define the particle number density function n(d, t, y), where d is the particle diameter, m; t is the time, h; y is the position along the flow channel, m. Determine the flow velocity U(t, y) inside the virtual impact separator by formula (1):

[0056]

[0057] Where Q(t,y) is the flow rate at position y of the virtual impactor separator at time t, which is equal to the flow rate at the working point of the virtual impactor separator and is a constant.

[0058] ② Considering the generation, transport, crushing and deposition of particles, establish the PBE equation

[0059]

[0060] Where: n(d,t,y) is the number density of particles of size d at position y and time t; represents the change of particle number density of the virtual impact separator due to time change; U(t,y) is the fluid velocity; represents the transport of particles along the flow channel caused by fluid flow in the virtual impact separator; k d (d, D, U) is the particle deposition rate due to particle inertia effect and diffusion effect.

[0061] Assuming the particles are spherical, their number density

[0062]

[0063] Where: C is the mass concentration of dust, kg / m 3 ρ p is the particle density, kg / m 3 ; d is the particle diameter, m.

[0064] S3: Calculate the deposition rate of particles in the virtual impact separator flow channel. The specific steps are:

[0065] ① Calculate the sedimentation rate adjustment factor f affected by humidity h :

[0066] f h =1+α×RH (4)

[0067] Where: α is the coefficient of change of deposition rate when humidity increases by 1%; RH is the current humidity test value

[0068] ② Considering the influence of humidity, establish the deposition rate calculation function k d (d,D,U,RH)

[0069]

[0070] Where: k d (d, D, U, RH) is the particle deposition rate, 1 / s; d is the particle diameter, m; D is the flow channel diameter, m; U is the flow rate of the fluid, m / s; RH is the relative humidity, %; μ is the dynamic viscosity of the air, Pa·s; ρ is the particle density, kg / m 3 .

[0071] S4: Solve the PBE equation in step S2 based on Matlab, Python and other tools to calculate the particle deposition amount D in the virtual impact separator flow channel t The specific steps are:

[0072] ① Create particle size and flow channel size grids, and initialize the particle number density matrix and deposition matrix;

[0073] ② Use the finite difference method to discretize the time and space derivatives, use forward differences to represent the time derivatives, and use backward differences or central differences to represent the space derivatives to obtain the discretized PBE equation.

[0074] ③ Starting from the initial conditions, the time step is iterated step by step to update the particle number density n(d, t, y). At the same time, the real-time values ​​of ambient dust concentration C and ambient humidity RH are obtained and updated. At each time step, the particle number density of the new time step is calculated according to the discretized PBE equation.

[0075] ④Integrate the logarithmic density n(d, t, y) along the length of the flow channel to calculate the deposition amount of particles on the flow channel wall D t .

[0076] S5, the calculated particle deposition amount D t The maximum allowable deposition amount D of the virtual impact separator a For comparison. Maximum allowable deposition amount D a According to the test, when the structure size of the virtual impact separator and the flow rate at the working point are constant, this value is a constant. t ≥D a When , it is considered that the separation performance of the virtual impact separator deviates from the maximum allowable error and needs to be cleaned and maintained in time.

[0077] Assume that by collecting the operating parameters of the virtual impact separator, there are the following working conditions as shown in Table 1:

[0078] Table 1

[0079]

[0080] Through testing, the maximum allowable deposition amount D of the virtual impact separator a =0.003kg / m 2 .

[0081] like Figure 2 As shown in (a) to (e), the particle deposition amount D is calculated by Matlab programming t , and visualize the distribution of the deposition amount, and obtain the deposition amount distribution diagram of the virtual impactor under the working conditions in the table for different continuous operation times. Figure 2 It can be seen that when t = 240h, the particle deposition amount D t =0.0031943kg / m 2 , at this time D t >D a Therefore, the virtual impact separator needs to be cleaned and maintained after running continuously for 240 hours under the working conditions described in the table.

[0082] In the above embodiments, the description's reference to "this embodiment" indicates that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least some embodiments, but not necessarily all embodiments. Multiple occurrences of "this embodiment" do not necessarily all refer to the same embodiment.

[0083] In the above-described embodiments, although the invention has been described in conjunction with specific embodiments of the invention, many substitutions, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art based on the foregoing description. For example, other storage structures (e.g., dynamic RAM (DRAM)) may use the embodiments discussed. Embodiments of the invention are intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of the appended claims.

[0084] This embodiment further provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, any one of the methods in this embodiment is implemented.

[0085] This embodiment also provides an electronic terminal, including: a processor and a memory;

[0086] The memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory, so that the terminal executes any one of the methods in this embodiment.

[0087] The computer-readable storage medium in this embodiment can be understood by ordinary technicians in this field: all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to the computer program. The aforementioned computer program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other media that can store program codes.

[0088] The electronic terminal provided in this embodiment includes a processor, a memory, a transceiver and a communication interface. The memory and the communication interface are connected to the processor and the transceiver and complete communication with each other. The memory is used to store computer programs, the communication interface is used to communicate, and the processor and the transceiver are used to run computer programs so that the electronic terminal executes each step of the above method.

[0089] In this embodiment, the memory may include a random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0090] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0091] The present invention can be used in many general or special computing system environments or configurations, such as personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, and the like.

[0092] The present invention may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules may be located in local and remote computer storage media, including storage devices.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for predicting dust deposition in a virtual impact separator flow channel based on numerical analysis, characterized in that: The following steps are involved: S1: Collect the operating parameters of the virtual impact separator for continuous dust separation; S2: According to the physical properties of the particles and the flow channel characteristics of the virtual impact separator, the PBE equation for the movement and deposition of particles in the flow channel is established; S3: Calculate the deposition rate of particles in the virtual impact separator flow channel; S4: solving the PBE equation to calculate the particle deposition amount in the virtual impact separator flow channel; S5: Compare the calculated particle deposition amount with the maximum allowable deposition amount of the virtual impact separator to obtain a cleaning maintenance cycle.

2. The method for predicting dust deposition in a virtual impact separator flow channel based on numerical analysis according to claim 1 is characterized in that: The operation parameters in step S1 include flow channel characteristic parameters, particle characteristic parameters and airflow characteristic parameters; The flow channel characteristic parameters are geometric structure parameters of the virtual impact separator, including characteristic diameter D and characteristic length L; The particle characteristic parameters include particle concentration C, density ρ p ; The airflow characteristic parameters include the working point flow rate Q of the virtual impact separator and the ambient humidity RH.

3. The method for predicting dust deposition in a virtual impact separator flow channel based on numerical analysis according to claim 1 is characterized in that: The step S2 specifically includes the following steps: S21: Define the diameter d of the particle and the number density function n(d, t, y) of the particle, where t is the time and y is the position along the flow channel. Calculate the flow velocity U(t, y) inside the virtual impact separator using formula (1): Where Q(t,y) is the flow rate at position y of the virtual impactor separator at time t, which is equal to the flow rate at the working point of the virtual impactor separator; S22: Considering the generation, transport, fragmentation and deposition of particles, the PBE equation is established: Where n(d,t,y) is the number density of particles with diameter d at position y and time t; represents the change of particle number density of the virtual impact separator due to time change; U(t,y) is the fluid velocity; represents the transport of particles along the flow channel caused by fluid flow in the virtual impact separator; k d (d, D, U) is the particle deposition rate due to particle inertia effect and diffusion effect; Assuming the particles are spherical, their number density Where C is the mass concentration of dust; ρ p is the particle density; d is the particle diameter.

4. The method for predicting dust deposition in a virtual impact separator flow channel based on numerical analysis according to claim 1 is characterized in that: The step S3 specifically comprises the following steps: S31: Calculation of the sedimentation rate adjustment factor f for humidity effects h : f h =1+α×RH (4) Where α is the coefficient of change of deposition rate when humidity increases by 1%; RH is the current humidity test value; S32: Establishing deposition rate calculation function k d (d,D,U,RH) Where k d (d, D, U, RH) is the particle deposition rate; d is the particle diameter; D is the flow channel diameter; U is the flow rate of the fluid; RH is the relative humidity; μ is the dynamic viscosity of the air; ρ is the particle density.

5. The method for predicting dust deposition in a virtual impact separator flow channel based on numerical analysis according to claim 1, characterized in that: The step S4 specifically comprises the following steps: S41: Create particle size and flow channel size grids, initialize particle number density matrix and deposition matrix; S42: Use the finite difference method to discretize the time and space derivatives, use forward differences to represent the time derivatives, and use backward differences or central differences to represent the space derivatives, and obtain the discretized PBE equations; S43: Starting from the initial conditions, the time step is iterated step by step, the particle number density n(d, t, y) is updated, and the real-time values ​​of the ambient dust concentration C and ambient humidity RH are obtained and updated. At each time step, the particle number density of the new time step is calculated according to the discretized PBE equation; S44: Integrate the logarithmic density n(d, t, y) along the length of the flow channel to calculate the particle deposition amount D on the flow channel wall t .

6. The method for predicting dust deposition in a virtual impact separator flow channel based on numerical analysis according to claim 1, characterized in that: In step S5, the maximum allowable deposition amount D a According to the test, when the structure size of the virtual impact separator and the flow rate at the working point are constant, this value is a constant; when D t ≥D a When , it is considered that the separation performance of the virtual impact separator deviates from the maximum allowable error and needs to be cleaned and maintained.

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