A design method for high-precision particle cutter

Abstract

The present invention discloses a design method for a high-precision particle cutter, comprising the following steps: S1, clarifying the working flow of the cyclone particle cutter; S2, clarifying the 50% cutting particle diameter D of the cutter; 50 ; S3, specify the diameter D of the cylindrical section of the cyclone cutter s S4, according to the working flow Q of the cutter, by the inlet wind speed value V in Determine the inlet diameter D in S5. Clearly define the annular Reynolds number Re of the cyclone cutter ann , and according to Re ann Calculate the outlet diameter D e S6, given the initial cylindrical segment height H s and the cone height H c The specific values ​​of the two are determined by experiments; S7, the value of the cone bottom diameter B is determined by experiments; S8, the size of the cutter under other working flow rates is determined; The high-precision PM2.5 particle cutter designed in the present invention can improve the accuracy of air quality monitoring data and effectively evaluate its cutting performance.

Description

Technical Field

[0001] The present invention relates to the technical field of atmospheric environment particulate matter treatment, and in particular to a design method of a high-precision particulate matter cutter. Background Art

[0002] As the problem of air pollution becomes increasingly serious, air quality monitoring and forecasting has become one of the important means to control air pollution and protect public health.

[0003] The PM2.5 particle cutter is a device that separates particles according to their particle size and achieves a 50% cutoff size of 2.5μm, and is then used to measure the concentration of fine particulate matter in the atmosphere.

[0004] Since the performance of the PM2.5 particle cutter affects the accuracy of air quality monitoring, it is necessary to carefully design its structural dimensions and effectively evaluate its cutting performance in order to improve the product testing accuracy and the rationality of the design process.

[0005] Therefore, a design method of a high-precision particle cutter is proposed to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a design method for a high-precision particle cutter.

[0007] A design method for a high-precision particle cutter comprises the following steps:

[0008] S1. Clarify the structural parameters of the cyclone particle cutter, mainly the inlet diameter D in , outlet diameter D e , cylindrical section diameter D s , cylindrical section height H s , cone section height H c and the cone bottom diameter B;

[0009] S2. Clearly define the 50% cut particle size D of the cutter 50 ;

[0010] S3. Determine the diameter D of the cylindrical section of the cyclone cutter s The value of

[0011] S4, according to the working flow Q of the cutter, by the inlet wind speed value V in Determine the inlet diameter D in The value of

[0012] Working flow Q and inlet wind speed V in The relationship between V inThe value is between (5-7) m / s, and D is calculated using formula (1) in The distribution interval of

[0013]

[0014] In the formula,

[0015] V in ——Inlet wind speed of the cutter, m / s;

[0016] Q——working flow rate of the cutter, L / min;

[0017] D in ——inlet diameter of the cutter, mm;

[0018] S5. Determine the annular Reynolds number Re of the cyclone cutter ann , and according to Re ann Calculate the outlet diameter D e size;

[0019] Annular Reynolds number Re ann is the geometric standard deviation σ that affects cutting performance g The important parameter Re ann The value of is between 3600-4800, and the outlet diameter D is determined by formula (2): e range.

[0020]

[0021] In the formula,

[0022] ρ——density of air, 1.20kg / m at 20℃ 3 ;

[0023] V in ——Inlet wind speed of the cutter, m / s;

[0024] μ——aerodynamic viscosity, 1.83×10-5Pa·s at 20℃;

[0025] D s ——Diameter of the cylindrical section of the cyclone cutter, m;

[0026] D e ——Diameter of the cyclone cutter outlet section, m;

[0027] S6. Given an initial H s and H c The specific values ​​of the two are determined through experiments;

[0028] S7. Given the initial value of B, determine the specific value of the cone bottom diameter B through experiments to ensure that the performance index D of the final designed cutter 50 Can meet the requirement of (2.3-2.7)μm;

[0029] S8, determining the cutter size value under other working flow rates;

[0030] According to formula (3), determine the diameter D of the cylindrical section of the cyclone cutter at other working flow points. s size.

[0031] ln(D 50 )=a+bln(D s )-(b-1)ln(Q) (3)

[0032] In the formula,

[0033] D 50 ——Median particle size of the cutter, μm;

[0034] D s ——Diameter of the cylindrical section of the cyclone cutter, cm;

[0035] Q——working air volume of the cutter, L / min;

[0036] a, b – empirical coefficients fitted using the least squares method.

[0037] Preferably, D in S2 50 =2.5μm.

[0038] Preferably, the diameter D of the cylindrical section in S3 is s It is related to the working air volume Q. Common working point flow rates are 3L / min, 5L / min, 16.7L / min and 100L / min. Take the working flow of 16.7L / min as an example. s =29.4mm.

[0039] Preferably, H in S6 s The value range is (0.4-1.0)D s , H c The value range is (0.6-1.2)D s , B range selection (0.2-1.0) D s .

[0040] Preferably, a and b in S8 are empirical coefficients, and the determination method thereof is as follows:

[0041] (1) For a cyclone cutter with a working flow rate of Q, at D 50 Under clear premise (usually D 50=2.5μm), given the initial values ​​a=1.0, b=2.0 and using formula (3) to calculate D s The value of

[0042] (2) Determine other structural parameters according to the method of steps S4-S7, thereby designing a preliminary model A of the cutter, and test the preliminary model A at different flow rates Q by experimental means. 50 , find the changes that satisfy D 50 = =2.5μm corresponding to the flow rate Q', and substitute it into equation (3) and still calculate D' according to the initial values ​​a = 1.0, b = 2.0 s The value of

[0043] (3) Other structural dimensions are scaled based on the preliminary model in (2) with a scaling factor of D' s / D s And through experiments, the individual structural dimensions are fine-tuned to make the performance of the cutter meet the corresponding index range.

[0044] The beneficial effects of the present invention are:

[0045] The high-precision PM2.5 particle cutter designed in the present invention can improve the accuracy of air quality monitoring and effectively evaluate its cutting performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the size and structure of the cyclone cutter. DETAILED DESCRIPTION

[0047] The present invention will be further explained below in conjunction with specific embodiments.

[0048] The cyclone cutter is mainly composed of an inlet, an outlet and a column-cone section. When the airflow hits the inner surface of the column section from the inlet, it will make a spiral motion under the influence of the column-cone section structure. Since the gas and the particles in it make a spiral motion, they are affected by centrifugal force. Considering that the density of particles is usually much greater than that of gas, the particles with greater inertia will break away from the airflow, adhere to the inner surface of the cutter and slide down into the sand settling tank. On the contrary, the particles and gas with smaller inertia will be discharged from the downstream of the cutter.

[0049] In order to better understand the working principle of the cutter, the concept of cutting efficiency of the particle cutter is first defined. Particles of a certain size pass through the cutter and a particle counter is used to measure the number of particles entering and exiting. The number of particles exiting is divided by the number of particles entering the cutter to obtain the cutting efficiency corresponding to the particle size. The cutting efficiency of particles of different sizes is tested separately, and finally the equation is used for fitting to obtain the cutting performance curve of the cutter. The above are all existing technologies, which are methods for evaluating the cutting ability of the cutter. On this basis, a high-precision particle cutter is designed.

[0050] Combination Figure 1 , a design method of a high-precision particle cutter, comprising the following steps:

[0051] S1. Clarify the structural parameters of the cyclone particle cutter, mainly the inlet diameter D in , outlet diameter D e , cylindrical section diameter D s , cylindrical section height H s , cone section height H c The diameter of the cone bottom, B, will determine the main performance of the particle cutter. In the process of affecting the performance of the cutter, since these dimensions are coupled with each other, the design must be carried out in a certain order, and the quantification of each dimension must be assisted by experimental means;

[0052] S2. Clearly define the 50% cut particle size D of the cutter 50 , choose D 50 =2.5μm;

[0053] S3. Determine the diameter D of the cylindrical section of the cyclone cutter s The value of the cylindrical segment diameter D s It is related to the working air volume Q. Common working point flow rates are 3L / min, 5L / min, 16.7L / min and 100L / min. Take the working flow of 16.7L / min as an example. s =29.4mm; it should be noted that the diameter of the cylindrical section D s It is not unique and needs to be designed according to specific needs, such as space, cost, and air volume. It only needs to keep other structural dimensions proportional to each other.

[0054] S4, according to the working flow Q of the cutter, by the inlet wind speed value V in Determine the inlet diameter D in The value of

[0055] Working flow Q and inlet wind speed V in The relationship between V inThe value is between (5-7) m / s, and D is calculated using formula (1) in The distribution interval of

[0056]

[0057] In the formula,

[0058] V in ——Inlet wind speed of the cutter, m / s;

[0059] Q——working flow rate of the cutter, L / min;

[0060] D in ——inlet diameter of the cutter, mm;

[0061] S5. Determine the annular Reynolds number Re of the cyclone cutter ann , and according to Re ann Calculate the outlet diameter D e size;

[0062] Annular Reynolds number Re ann is the geometric standard deviation σ that affects cutting performance g The important parameter Re ann The value of is between 3600-4800, and the outlet diameter D is determined by formula (2): e range.

[0063]

[0064] In the formula,

[0065] ρ——density of air, 1.20kg / m at 20℃ 3 ;

[0066] V in ——Inlet wind speed of the cutter, m / s;

[0067] μ——aerodynamic viscosity, 1.83×10-5Pa·s at 20℃;

[0068] D s ——Diameter of the cylindrical section of the cyclone cutter, m;

[0069] D e ——Diameter of the cyclone cutter outlet section, m;

[0070] S6. Given an initial H s and H c The specific values ​​of H and H are determined through experiments. s The value range is (0.4-1.0)D s , H cThe value range is (0.6-1.2)D s ; When the two change within the corresponding value range, for the 50% cutter particle size D 50 and the geometric standard deviation σ g The change will not be too significant, but the best size value needs to be selected through experimental results to optimize the cutting performance;

[0071] S7. Determine the value of the cone bottom diameter B through experiments. Usually the range of B is (0.2-1.0)D s ; Generally speaking, when other structural dimensions remain unchanged, when the B value is increased, D 50 will become larger, while reducing the value of B will increase D 50 Will become smaller, relative to D 50 In terms of the change of cone bottom diameter B, g The influence of B is small; the specific value of B can be determined by experiment to ensure that the performance index D of the final designed cutter 50 Can meet the requirement of (2.3-2.7)μm;

[0072] S8, determining the cutter size value under other working flow rates;

[0073] According to formula (3), determine the diameter D of the cylindrical section of the cyclone cutter at other working flow points. s size.

[0074] ln(D 50 )=a+bln(D s )-(b-1)ln(Q) (3)

[0075] In the formula,

[0076] D 50 ——Median particle size of the cutter, μm;

[0077] D s ——Diameter of the cylindrical section of the cyclone cutter, cm;

[0078] Q——working air volume of the cutter, L / min;

[0079] a, b – empirical coefficients fitted using the least squares method.

[0080] a, b are empirical coefficients, and their determination method is as follows:

[0081] (1) For a cyclone cutter with a working flow rate of Q, at D 50 Under clear premise (usually D 50 =2.5μm), given the initial values ​​a=1.0, b=2.0 and using formula (3) to calculate D s The value of

[0082] (2) Determine other structural parameters according to the method of steps S4-S7, thereby designing a preliminary model A of the cutter, and test the preliminary model A at different flow rates Q by experimental means. 50 , find the changes that satisfy D 50 = =2.5μm corresponding to the flow rate Q', and substitute it into equation (3) and still calculate D' according to the initial values ​​a = 1.0, b = 2.0 s The value of

[0083] (3) Other structural dimensions are scaled based on the preliminary model in (2) with a scaling factor of D' s / D s , determine the optimized model structure B, and fine-tune the individual structural dimensions through experiments, so that the performance of the cutter meets the corresponding index range.

[0084] Therefore, the high-precision PM2.5 particle cutter designed in the present invention can improve the accuracy of air quality monitoring and effectively evaluate its cutting performance.

[0085] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A design method for a high-precision particle cutter, characterized in that: The following steps are involved: S1. Clarify the structural parameters of the cyclone particle cutter, mainly the inlet diameter D in , outlet diameter D e , cylindrical section diameter D s , cylindrical section height H s , cone section height H c and the cone bottom diameter B; S2. Clearly define the 50% cut particle size D of the cutter 50 ; S3. Determine the diameter D of the cylindrical section of the cyclone cutter s The value of S4, according to the working flow Q of the cutter, by the inlet wind speed value V in Determine the inlet diameter D in The value of Working flow Q and inlet wind speed V in The relationship between V in The value is between 5-7m / s, and the distribution range of Din is calculated using formula (1); In the formula, V in ——Inlet wind speed of the cutter, m / s; Q——working flow rate of the cutter, L / min; D in ——inlet diameter of the cutter, mm; S5. Determine the annular Reynolds number Re of the cyclone cutter ann , and according to Re ann Calculate the outlet diameter D in the range e size; Annular Reynolds number Re ann is the geometric standard deviation σ that affects cutting performance g The important parameter Re ann The value of is between 3600-4800, and the outlet diameter D is determined by formula (2): e scope; In the formula, ρ——density of air, 1.20kg / m at 20℃ 3 ; V in ——Inlet wind speed of the cutter, m / s; μ——aerodynamic viscosity, 1.83×10-5Pa·s at 20℃; D s ——Diameter of the cylindrical section of the cyclone cutter, m; D e ——Diameter of the cyclone cutter outlet section, m; S6. Given an initial H s and H c The specific values ​​of the two are determined through experiments; S7. Determine the value of the cone bottom diameter B through experiments to ensure the performance index D of the final designed cutter 50 Can meet the requirements of 2.3-2.7μm; S8, determining the cutter size value under other working flow rates; According to formula (3), the diameter Ds of the cylindrical section of the cyclone cutter at other working flow points is determined; ln(D 50 )=a+bln(D s )-(b-1)ln(Q) (3) In the formula, D 50 ——Median particle size of the cutter, μm; D s ——Diameter of the cylindrical section of the cyclone cutter, cm; Q——working air volume of the cutter, L / min; a, b——empirical coefficients fitted by the least squares method; Where a and b are empirical coefficients, which are determined as follows: (1) For a cyclone cutter with a working flow rate of Q, at D 50 Under the clear premise 50 = 2.5 μm, given the initial values ​​a = 1.0, b = 2.0 and using formula (3) to calculate D s The value of (2) Determine other structural parameters according to the method of steps S4-S7, thereby designing a preliminary model A of the cutter, and test the preliminary model A at different flow rates D by experimental means. 50 , find the changes that satisfy D 50 = =2.5μm corresponding to the flow rate Q', and substitute it into equation (3) and still calculate D' according to the initial values ​​a = 1.0, b = 2.0 s The value of (3) Other structural dimensions are scaled based on the preliminary model in (2) with a scaling factor of D' s / D s , determine the optimized model structure B, and fine-tune the individual structural dimensions through experiments, so that the performance of the cutter meets the corresponding index range.

2. The design method of a high-precision particle cutter according to claim 1, characterized in that: Select D in S2 50 =2.5μm.

3. The design method of a high-precision particle cutter according to claim 1, characterized in that: The diameter D of the cylindrical section in S3 s Related to the working air volume Q, the commonly used working point flow rates are 3L / min, 5L / min, 16.7L / min and 100L / min.

4. The design method of a high-precision particle cutter according to claim 1, characterized in that: The S6H s The value range is 0.4-1.0D s , H c The value range is 0.6-1.2D s .

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