A method for measuring the flow of tobacco in a wind force tobacco feeding pipe, a storage medium and a device

Abstract

The application discloses a kind of wind force sends tobacco flow measurement method, storage medium and device in pipe, the method is along the uniform distribution of multiple groups of capacitance tomography sensor in pipe cross section circumference, the capacitance tomography sensor is used to measure pipe tobacco flow;Including:1) the mass concentration β s Of pipe in conveying tobacco;2) establish conveying tobacco model;3) establish the relationship between capacitance tomography sensor voltage scalar and pipe cross section average mass concentration;4) establish the measurement equation of pipe tobacco instantaneous flow.The application realizes the tobacco flow in the process of conveying tobacco to be measured more accurately, measurement result is expressed in Kg / h, so that the conveying amount, consumption amount and the like of tobacco are counted and recorded, and the control ability of tobacco consumption is improved. Through the embodiment, it is shown that the tobacco flow error is in the range of 0-500kg / h, the error is less than 1.5%, the cumulative amount of tobacco conveying is less than 5kg per hour, i.e. the cumulative amount error is less than 1%.

Description

Technical Field

[0001] This invention relates to the measurement of tobacco flow rate in a pipe, specifically to a method, storage medium, and device for measuring tobacco flow rate in a pneumatically powered tobacco delivery pipe. Background Technology

[0002] Pneumatic (or air-powered) conveying is widely used in cigarette manufacturing, such as the process of conveying finished tobacco shreds to cigarette packs, the process of air-separating and conveying stems to flavoring, and the process of conveying tobacco powder or granules to dust removal.

[0003] Although pneumatic conveying technology has been used in the tobacco industry for a long time, research on its conveying process and principles is relatively limited compared to other industries, and designs often directly borrow data from general technical research. However, in order to solve the problems encountered in its application, more in-depth research has been conducted.

[0004] From an industrial application perspective, pneumatic conveying systems are widely used in cigarette production processes both domestically and internationally, serving as an indispensable and crucial device for continuous cigarette production. Practice has proven that pneumatic conveying systems offer advantages such as flexible layout, convenient management, and applicability to horizontal, vertical, and curved conveying over various distances. Furthermore, they can achieve process objectives such as loosening, impurity removal, dehydration, cooling, and dust removal during the conveying process. However, improper design or use can lead to problems such as stratification and breakage of tobacco shreds during intermittent conveying, increasing the risk of uneven tobacco shred distribution. Moreover, compared to other tobacco feeding methods, pneumatic conveying systems consume significantly more power.

[0005] From the perspective of applied basic research, as mentioned earlier, pneumatic conveying is a complex multiphase flow process. The movement of tobacco shreds in the conveying pipe involves various conditions such as the distribution of airflow velocity and friction between the tobacco shreds and the gas and pipe walls. The movement of tobacco shreds in the conveying pipe involves both rolling and suspension, and there is friction between tobacco shreds as well as friction or collision with the pipe walls. Considering all these issues is quite complex. For a long time, a lot of research has been done on pneumatic conveying systems for particles, but many problems have not been well solved. The pneumatic conveying process of tobacco shreds (tow system) has been studied even less. The problems of tobacco shred breakage and stratification generated in this process are even more difficult to solve. To alleviate this problem, the usual method is to reduce the velocity of the conveying airflow, but this can easily lead to flow instability and even blockage. In addition, the conveying efficiency of the system is also an important issue. The structure and physical properties of the conveyed tobacco shreds, their resistance to breakage, and the conditions of the conveying system itself are all factors that interact and jointly determine the efficiency of pneumatic conveying. Examining the conveying effect from a comprehensive perspective is very complex.

[0006] The gas-solid two-phase flow characteristics within a system directly affect its stable and efficient operation. Therefore, to optimize the design and operation of a pneumatic conveying system, it is essential to understand the flow characteristics and patterns of the gas-solid two-phase flow during operation, and to conduct in-depth research on the flow characteristics of tobacco shreds within the pipeline. Consequently, these issues have become a key focus of applied basic research.

[0007] However, measuring the flow and quality during the transportation process has always been a challenge in the tobacco manufacturing industry. Due to the lack of corresponding measurement methods, the tobacco shreds transported to the rolling and packaging workshop cannot be accurately weighed, which also makes it impossible to accurately control the consumption of tobacco shreds.

[0008] However, measuring the flow rate of pneumatic conveying is a difficult problem, especially in horizontal pipes. Different flow states arise, and the spatial and temporal distribution of the conveyed particles during transport, along with the corresponding velocity profiles, are quite complex.

[0009] The diversity of flow states is extending from dispersed to dense flow states, where distinct sub-layers and dense slugs may appear, filling the entire cross-section of the pipe. Therefore, detecting the appropriate speed in tobacco conveying is of great significance for reducing breakage, controlling material consumption, and improving transportation efficiency.

[0010] CN109580729A discloses a capacitance tomography sensor detection system that can be installed on the outside or inside of various pipes to detect the distribution of mixed fluids within the pipe. However, the tobacco transport process involves both gas and solid components, making the fluid detection and measurement objects in practice more complex.

[0011] The paper "Design of Instantaneous Flow Monitoring System for Tobacco Shreds in Belt Conveyor Based on Ultrasonic Sensor" (Zhou Aimin et al. [J]. Modern Information Technology, 2022, 6(03): 149-152. DOI: 10.19850 / j.cnki.2096-4706.2022.03.040.) proposed using ultrasonic sensors for tobacco shreds in a belt conveyor to measure the supply flow rate of tobacco shreds from the supply end, thereby indirectly detecting the flow rate of the material in pneumatic conveying. However, since the mass density of tobacco shreds changes significantly as it passes through the conveyor belt, feeder, and uniform feeder, the final flow rate estimate in the pneumatic conveying pipeline is not accurate.

[0012] The paper "Quantitative Detection and Motion Characteristics Analysis of Tobacco Velocity in Lifting Pipe" (Chen Ran et al. [J]. Tobacco Science and Technology, 2021, 54(08):71-79. DOI:10.16135 / j.issn1002-0861.2020.0504.) proposes a method for detecting the velocity of tobacco shreds in lifting pipe based on image registration algorithm. That is, a high-speed camera is used to continuously collect images of tobacco shreds in the lifting pipe. However, the diameter of the pneumatic conveying pipe is about 40 cm. Installing a camera will inevitably reduce the effective conveying diameter of the pipe, resulting in a decrease in conveying efficiency. Even if the pipe diameter is increased and a camera is installed, there is still a problem that the lack of optical fiber in the pipe will result in unclear camera images. Even if a light source is added and the pipe diameter is increased, there is still a defect that a larger air volume is required to convey the same amount of tobacco shreds, which is not energy-saving and environmentally friendly. Summary of the Invention

[0013] The problem this invention aims to solve is to accurately measure the tobacco flow rate during the tobacco conveying process, with the measurement result expressed in kg / h, thereby enabling the statistical recording of the amount of tobacco conveyed and consumed, improving the control of tobacco consumption, and thus creating economic value.

[0014] The technical solution of this invention is as follows:

[0015] A method for measuring the flow rate of tobacco shreds in a pneumatically powered tobacco delivery duct, comprising the following steps: Multiple sets of capacitance tomography sensors are uniformly arranged along the circumference of a cross-section of the duct, wherein the capacitance tomography sensors are used to measure the flow rate of tobacco shreds in the duct.

[0016] Step 1, the mass concentration β in the pipe conveying the tobacco shreds s

[0017] During pneumatic conveying, tobacco shreds may exhibit static and non-static flow patterns. Considering the cross-sectional representation of material distribution, different flow states can be summarized by the characteristics of two cross sections:

[0018] (1) The uniform mass concentration across the entire cross-section of the pipe corresponds to the dispersed and slug flow states;

[0019] (2) A dense lower phase with a certain height and a dispersed upper phase corresponding to the flow state of different material layers at the bottom.

[0020] In the first case described above, the random sample is obtained by using a constant random mass concentration β. s This situation rarely occurs when it is applied to the entire cross-section of the pipe.

[0021] In the second scenario described above, due to the influence of gravity, the tobacco shreds are propelled forward by the wind during lateral transport, and a certain amount of buoyancy counteracts gravity, resulting in a distribution that is sparser at the top and denser at the bottom. Therefore, the tobacco shred distribution can be parameterized, and statistical data can be generated using the following formula:

[0022]

[0023] Where: h(x) = a1 + a2x + a3x 2 , representing the height of the tobacco shreds at the cross-sectional boundary, the parameters a1a2, a3 can be obtained by polynomial fitting of experimental data, β s，1 and β s，u These represent the concentration differences above and below the boundary, respectively. It is clear that β... s，u ≤β s，1 Because the concentration in the upper layer is less than that in the lower layer; erf(·) is the Gaussian error function, and there is an additional scaling parameter γ used to adjust the mass concentration gradient dβ. s / dh, where x and y are the width and height coordinates of the pipe cross-section, respectively.

[0024] Step 2, feeding the tobacco shreds into the mold

[0025] The purpose of establishing a model for conveying tobacco shreds is to describe the relationship between the mass concentration of tobacco shreds and the relative permittivity of the gas during pneumatic conveying. Preferably, the Landau-Lishitz-Looyenga (LLL) equations are a suitable model for describing this relationship.

[0026]

[0027] Where: ε r The mixture has a relative permittivity, ε r，s and ε r，g ρ represents the relative permittivity of the solid material and the relative permittivity of the gas; these two parameters can be measured before the experiment begins. s Tobacco density, β s As given in step 1.

[0028] Step 3: Establish the relationship between the scalar potential (voltage scalar) of the capacitance chromatography sensor and the average mass concentration of the pipe cross-section.

[0029] The purpose of this sensor model is to describe the relationship between the dielectric material distribution within the sensor and the capacitance between the sensors' electrodes. An electrode N of a capacitive sensor... elec Provide M = (N) elec (N elec -1)) / 2 Independent measurable capacitance, the physical effects within the sensor are calculated using the Pythagorean equation of the electrostatic field formula, which can be derived from Maxwell's equations:

[0030]

[0031]

[0032] Where: V refers to the electrical scalar potential, that is, the voltage scalar, ε0 = 8.854 × 10 -12 Fm -1 ε is the dielectric constant of vacuum. r In formula (2), n represents the surface normal vector on the electrode surface. T ε is the excitation voltage of the measuring circuit, V is the calculated result of formula (2), C is the actual measured value, and C is the capacitance measured by the circuit. A set of differential operators representing the gradient.

[0033] Step 4, Calibration Process

[0034] To compensate for the discrepancy between the measurement system and the estimation model, a sensor calibration strategy is applied to the measurement data of the capacitance sensor. In this work, a linear calibration method is employed, applying offset / gain calibration to the original capacitance measurements. Calibration points are selected for an empty sensor and a sensor fully filled with defined tobacco with a known dielectric constant. This requires only linear calibration for both the empty and full tubes to determine the values ​​of offset b and gain k.

[0035] Step 5, Equation for measuring the instantaneous flow rate of tobacco in the pipe

[0036] m s =flow*t=β s *V 管

[0037] V 管 =r 2 πl (4)

[0038] Where: r is the radius of the measuring section of the pipeline, l is the length of the measuring section of the pipeline, and β s The mass concentration of tobacco in the pipe is calculated by formula (1). r and l are determined when the sensor is installed. π is the circumference ratio.

[0039] Furthermore, a noise addition step is included before step 4:

[0040] Noise is added to increase the measurement stability of the measurement system (i.e., the front-end circuitry and sensors), and it represents all possible random effects in the measurement system. Preferably, Gaussian noise is added.

[0041] The present invention also provides a computer-readable storage medium having a computer program stored thereon, the computer program being executable by a processor to implement the steps of the method for measuring the flow rate of tobacco shreds in a wind-powered tobacco feeding duct according to the present invention.

[0042] The present invention also provides a device for measuring the flow rate of tobacco shreds in a wind-powered tobacco delivery pipe, comprising a capacitance tomography sensor, a sensor measurement circuit, a data acquisition unit and a computer. The data acquisition unit is used to acquire the electroscalar potential V output by the sensor measurement circuit, and the computer has a built-in computer-readable storage medium as described in the present invention.

[0043] Multiple sets of capacitance tomography sensors are evenly distributed along the circumference of a cross-section of the pipe. The capacitance tomography sensors are used to measure the flow rate of tobacco in the pipe. Each set of capacitance tomography sensors includes two electrodes, which are arranged on the circumference of a non-conductive pipe section.

[0044] The sensor measurement circuit includes capacitors Cs1 and Cs2, respectively connected to the two electrodes of the capacitance tomography sensor Cx. One end of capacitor Cs1 is connected to a signal generator Vc, and the other end is grounded. One end of capacitor Cs2 is connected to the negative input terminal of a first operational amplifier, and the other end is grounded. The positive input terminal of the first operational amplifier is grounded, and its output is connected to the negative input terminal of a second operational amplifier after passing through a resistor. The positive input terminal of the second operational amplifier is grounded, and its output scalar potential V is processed to obtain the tobacco flow in the pipe. Vc is a sine wave signal generator.

[0045] Furthermore, capacitors and resistors for filtering are connected in parallel directly at the negative input terminals and the output terminals of the first and second operational amplifiers.

[0046] Furthermore, the electrodes of the capacitance tomography sensor are surrounded by a grounded shield to avoid external influences, and a guard ring is used to reduce edge effects.

[0047] In a sensor measurement circuit, as long as the output impedance of the voltage source (such as an output amplifier) ​​is small enough, then for C... x The influence of measurements from (a set of capacitive sensors) can be ignored. This is because the feedback point of the operating amplifier remains on virtual ground and there is no potential difference, C s1 C s2 Also for measuring C x There is no impact; therefore, this capacitance measurement circuit is inherently spurious-immune. Nevertheless, C s1 C s2 Ideally, the value should be within 10 pF.

[0048] Furthermore, the signal generator Vc has the following characteristics:

[0049] (1) Wide frequency range, up to 2MHz;

[0050] (2) Stable frequency, 1×10 -5 Hz;

[0051] (3) The amplitude of the stable sine wave is less than 0.01%;

[0052] (4) Adjustable sine wave amplitude;

[0053] (5) Less signal distortion.

[0054] The beneficial effects of this invention are:

[0055] This invention enables relatively accurate measurement of tobacco flow rate during the tobacco conveying process, with the measurement result expressed in kg / h. This allows for the statistical recording of tobacco conveying volume and consumption, improving the control of tobacco consumption and thus creating economic value. Examples show that the tobacco flow rate error is less than 1.5% within the range of 0-500 kg / h, and the cumulative tobacco conveying volume is less than 5 kg per hour, meaning the cumulative volume error is less than 1%. Attached Figure Description

[0056] Figure 1 : Flowchart of the measurement method of the present invention.

[0057] Figure 2 Schematic diagram of two cross-sectional characteristics of tobacco shreds in wind-powered transportation.

[0058] Figure 3 A schematic diagram of the average boundary curve obtained from multiple measurements.

[0059] Figure 4 : Schematic diagram of linear calibration method.

[0060] Figure 5 : Schematic diagram of the installation location of the capacitance tomography sensor in the pipeline.

[0061] Figure 6 Schematic diagram of the capacitive tomography sensor arranged circumferentially along the cross-section of the pipe.

[0062] Figure 7 Schematic diagram of sensor measurement circuit.

[0063] Figure 8 : Schematic diagram of measurement results. Detailed Implementation

[0064] like Figure 1 As shown, a method for measuring the flow rate of tobacco shreds in a wind-powered tobacco delivery duct includes the following steps:

[0065] 1. Statistical process modeling to obtain the mass concentration β in the pipe transporting tobacco. s

[0066] like Figure 2 As shown, during pneumatic conveying, tobacco may exhibit static and non-static flow modes. Considering the cross-sectional representation of material distribution, different flow states can be summarized by the characteristics of two cross sections:

[0067] (1) The uniform mass concentration across the entire cross-section of the pipe corresponds to the dispersed and slug flow states;

[0068] (2) A dense lower phase with a certain height and a dispersed upper phase corresponding to the flow state of different material layers at the bottom.

[0069] In the first case described above, the random sample is obtained by using a constant random mass concentration β. s This situation rarely occurs when it is applied to the entire cross-section of the pipe.

[0070] In the second scenario described above, due to the influence of gravity, the tobacco shreds are propelled forward by the wind during lateral transport, and a certain amount of buoyancy counteracts gravity, resulting in a distribution that is sparser at the top and denser at the bottom. Therefore, the tobacco shred distribution can be parameterized, and statistical data can be generated using the following formula:

[0071]

[0072] Where: h(x) = a1 + a2x + a3x 2 , representing the height of the tobacco shreds at the cross-sectional boundary, the parameters a1a2, a3 can be obtained by polynomial fitting of experimental data, β s，1 and β s，u These represent the concentration differences above and below the boundary, respectively. It is clear that β... s，u ≤β s，1 Because the concentration in the upper layer is less than that in the lower layer; erf(·) is the Gaussian error function, and there is an additional scaling parameter γ used to adjust the mass concentration gradient dβ. s / dh, where x and y are the width and height coordinates of the pipe cross-section, respectively.

[0073] For example, in this embodiment, a measuring section of plastic tube r = 100 mm and length l = 400 mm is installed. The weight of the tobacco is measured using a balance with a resolution of 0.01 g. The measurement is taken and the scale is marked on the outside of the plastic tube, thus allowing for a direct measurement of the material's height h inside the tube. A capacitive sensor and its measuring circuit, as described in this invention, are installed on the outside of the plastic tube. Through multiple measurements, an average boundary curve is obtained (see...). Figure 3 As shown), that is, h(x) in formula (1).

[0074] In multiple measurements, point 1 is (30, 40), point 2 is (60, 70), and point 3 is (90, 50). Therefore, the undetermined coefficients a1 are -10, a2 is 13 / 6, and a3 is -1 / 60. The boundary curve is...

[0075] Then, substituting into formula (1), based on multiple experiments, a value of 0.3 for γ in formula (1) is suitable for this parameter pipeline, thus obtaining the average distribution β of tobacco leaves in the measurement section. s (x, y).

[0076] 2. Tobacco conveying model

[0077] The purpose of establishing a model for conveying tobacco is to describe the relationship between the mass concentration of tobacco and the relative permittivity of the gas during pneumatic conveying. Preferably, the Landau-Lishitz-Looyenga (LLL) equations are suitable for describing this relationship:

[0078]

[0079] Where, ε r The mixture has a relative permittivity, ε r，s and ε r，g ρ represents the relative permittivity of the solid material and the relative permittivity of the gas; these two parameters can be measured before the experiment begins. s Tobacco density, β s As given in step 1.

[0080] For example, ε r，s The relative permittivity of tobacco shreds is generally 1.6-1.7, and we take 1.65ε. r，g The relative permittivity of the gas is taken as the conventional value of air, 1.ρ. s The tobacco density was taken as 1.1 g*cm³, based on the "National Standard for Flue-cured Tobacco (Grade 40): Research on Leaf Thickness, Leaf Weight and Leaf Density of Henan Tobacco Leaves". -3 Substituting into formula (2), for example, at a certain moment, the ε inside the tube at (30, 40) is... r The mixture has a relative permittivity of Substituting the value, we get ε at (30, 40). r The value is 1.18827. Since the pipe radius is 100, x and y are taken as 0-200.

[0081] 3. Capacitive tomography sensor

[0082] The purpose of this sensor model is to describe the relationship between the dielectric material distribution within the sensor and the capacitance between the sensors' electrodes. An electrode N of a capacitive sensor... elec Provide M = (N) elec (N elec-1)) / 2 Independent measurable capacitance.

[0083] The physical effects within the sensor are calculated using Laplace's equation, the formula for the electrostatic field, which can be derived from Maxwell's equations.

[0084]

[0085]

[0086] Where: V refers to the electrical scalar potential, that is, the voltage scalar, ε0 = 8.854 × 10 -12 Fm -1 ε is the dielectric constant of vacuum. r In formula (2), n represents the surface normal vector on the electrode surface. VT is the excitation voltage of the measuring circuit, ε is the calculation result of formula (2), V is the actual measured value, and C is the capacitance measured by the circuit. A set of differential operators representing the gradient. The equation for measuring the instantaneous flow rate of tobacco in a pipe.

[0087] m s =flow*t=β s *V 管

[0088] V 管 =r 2 πl (4)

[0089] Where: r is the radius of the measuring section of the pipeline, l is the length of the measuring section of the pipeline, and β s The mass concentration of tobacco in the pipeline calculated by formula (1) is given by r and l, which are determined during sensor installation. π is pi, and t is the time it takes for the tobacco to pass through the measurement section. For example, at a certain moment, the capacitance tomography sensor measures the total capacitance value to be 0.1770 pF, which is C in formula (3). Therefore, the dielectric constant of the tobacco in the pipeline at that moment in formula (3) is ε = 1.23024. Formula (2) is then modified. Where ε r ε is 1.23024, measured at this moment. r，s The relative permittivity of tobacco shreds is generally 1.6-1.7, and we take 1.65ε. r，g The relative permittivity of the gas is taken as the conventional value of air, 1.ρ. s The tobacco shred density is taken as 1.1 g*cm-3 according to the "National Standard for Flue-cured Tobacco (Grade 40) Research on Leaf Thickness, Leaf Weight and Leaf Density of Henan Tobacco Leaves". Substituting this into the numerical calculation, β can be obtained. s The value is 5.2381; the measuring pipe length is r = 0.1m, l = 0.4m, therefore V_pipe = 0.01256m. 3t is the time it takes for the tobacco to pass through the measurement segment. In this embodiment, it is taken as 1 second. The tobacco flow rate at this moment is flow = 5.2381 * 0.01256 = 0.0658 kg / s, which is equivalent to 237 kg / h. The weight of the tobacco measured at this moment is 0.0658 kg.

[0090] 4. Noise addition

[0091] Noise is added to increase the measurement stability of the measurement system (i.e., the front-end circuit and the sensor), representing all possible random effects in the measurement system. Gaussian noise is preferred. The purpose of adding noise is that the distribution of tobacco flow rate in the pipe is complex, and experiments alone cannot fully cover all situations. Therefore, in formula (3), random noise with a mean of 0.0001 and a standard deviation of 0.00001 pf is added to directly interfere with the measurement result C to a certain extent.

[0092] 5. Calibration process

[0093] To compensate for the discrepancy between the measurement system and the estimation model, a sensor calibration strategy is applied to the measurement data of the capacitance sensor. In this work, offset / gain calibration is applied to the raw capacitance measurement, which requires two calibration points.

[0094] Preferably, the calibration point is selected as an empty sensor and a sensor completely filled with defined tobacco shreds having a known dielectric constant.

[0095] As a preferred option, a point-by-point calibration method can be further adopted to gradually calibrate the flow rate of tobacco in the pipeline using a measurement value of 0.001pf.

[0096] Calibration methods such as Figure 4 As shown.

[0097] like Figure 5 As shown, a device for measuring the flow rate of tobacco shreds in a wind-powered tobacco delivery duct includes a capacitance tomography sensor, a sensor measurement circuit, a data acquisition unit, and a computer. The data acquisition unit is used to acquire the electroscalar potential V output by the sensor measurement circuit, and the computer has a built-in computer-readable storage medium as described in this invention.

[0098] like Figure 6 As shown, due to the different flow states of pneumatically transported tobacco, the capacitance measurement may vary even with the same cross-sectional average mass concentration, making it impossible to distinguish between gas and solid using a single electrode pair. This inherent uncertainty is a known characteristic of capacitive sensors and can be used in distributed capacitive sensors with a small number of electrodes.

[0099] The sensor is provided by two or more electrodes arranged on the circumference of a non-conductive pipe section. The electrodes are surrounded by a grounded shield to avoid external influences and a guard ring is used to reduce edge effects.

[0100] The dielectric properties of the transported tobacco and the characteristics of the flow process, i.e. the flow state, will affect the capacitance between the electrodes of the sensor, thereby affecting the capacitance sensing signal.

[0101] The measurement circuit for a certain group of capacitance sensors is as follows: Figure 7 As shown.

[0102] In a circuit, as long as the output impedance of the voltage source (such as an output amplifier) ​​is small enough, then for C... x The influence of measurements from (a set of capacitive sensors) can be ignored. This is because the feedback point of the operating amplifier remains on virtual ground and there is no potential difference, C s1 C S2 Also for measuring C x There is no impact; therefore, this capacitance measurement circuit is inherently stray-immune.

[0103] Despite this, C s1 C s2 Ideally, the value should be within 10 pF.

[0104] Vc is a signal generator with the following characteristics:

[0105] (1) Wide bandwidth, up to 2MHz;

[0106] (2) Stable frequency, 1×10 -5 Hz;

[0107] (3) The amplitude of the stable sine wave is less than 0.01%;

[0108] (4) Adjustable sine wave amplitude;

[0109] (5) Less signal distortion.

[0110] like Figure 8 As shown, the experimental results are as follows:

[0111] SUMMARY OUTPUT

[0112]

[0113] The linear calibration method is used here. The tobacco flow rate error is within the range of 0-500 kg / h, with an error of less than 1.5%. The cumulative tobacco conveying amount is less than 5 kg per hour, that is, the cumulative amount error is less than 1%.

Claims

1. A method for measuring the flow rate of tobacco shreds in a pneumatically powered tobacco delivery duct, characterized in that, The method involves uniformly distributing multiple sets of capacitance tomography sensors along the circumference of a cross-section of the pipe. These sensors are used to measure the flow rate of tobacco shreds within the pipe. The method includes the following steps: Step 1, the mass concentration β in the pipe conveying the tobacco shreds s Where: h(x) = a1 + a2x + a3x 2 h(x) represents the height of the tobacco shreds at the cross-sectional boundary. Parameters a1, a2, and a3 can be obtained by polynomial fitting of experimental data. β s，1 and β s，u These represent the concentration differences above and below the boundary, and β s，u ≤β s，1 ;erf(·) is the Gaussian error function; γ is an additional scaling parameter used to adjust the mass concentration gradient dβ. s / dh; x and y are the width and height coordinates of the pipe cross-section, respectively; Step 2, feeding the tobacco shreds into the mold The purpose of establishing the tobacco conveying model is to describe the relationship between the mass concentration of tobacco and the relative permittivity of the gas during pneumatic conveying: Where: ε r The mixture has a relative permittivity, ε r，s and ε r，g ρ represents the relative permittivity of the solid material and the relative permittivity of the gas; these two parameters can be measured before the experiment begins. s Tobacco density, β s As given in formula (1); Step 3: Establish the relationship between the voltage scalar of the capacitance chromatography sensor and the average mass concentration of the pipe cross-section. An electrode N of a capacitive sensor elec Provide M = (N) elec (N elec -1)) / 2 Independent measurable capacitance, the physical effects within the sensor are calculated using Laplace's equation for the electrostatic field, which can be derived from Maxwell's equations: Where: V refers to the voltage scalar, ε0 = 8.854 × 10 -12 Fm -1 ε is the dielectric constant of vacuum. T In formula (2), n represents the surface normal vector on the electrode surface; V T ε is the excitation voltage of the measuring circuit, V is the calculated result of formula (2), C is the actual measured value, and C is the capacitance measured by the circuit. A set of differential operators represents the gradient; Step 4, instantaneous flow rate of tobacco in the pipe (m) s Measurement equation m s =flow*t=β s *V 管 (4) V 管 ＝r 2 πl Where: r is the radius of the measuring section of the pipeline, l is the length of the measuring section of the pipeline, and β s The mass concentration of tobacco in the pipe is calculated by formula (1). r and l are determined when the sensor is installed. π is the circumference ratio.

2. The method for measuring the flow rate of tobacco shreds in a pneumatically powered tobacco feeding duct according to claim 1, characterized in that: Before step 4, a random noise with a mean of 0.0001 and a standard deviation of 0.00001 pf is added to formula (3).

3. The method for measuring the flow rate of tobacco shreds in a pneumatically powered tobacco delivery pipe according to claim 1, characterized in that: The additional scaling parameter γ shown is 0.

3.

4. The method for measuring the flow rate of tobacco shreds in a pneumatically powered tobacco delivery pipe according to claim 1, characterized in that, Step 4 also includes a calibration process to compensate for deviations between the measurement system and the measurement equations.

5. The method for measuring the flow rate of tobacco shreds in a pneumatically powered tobacco delivery pipe according to claim 4, characterized in that, The offset / gain calibration is applied to the original capacitance measurement. The calibration points are two calibration points, one for an empty tube and one for a full tube, and the values ​​of offset b and gain k are obtained.

6. The method for measuring the flow rate of tobacco shreds in a pneumatically fed tobacco duct according to claim 4, characterized in that, The point-by-point calibration method was adopted to gradually calibrate the flow rate of tobacco in the pipeline with a measurement value of 0.001pf.

7. A computer-readable storage medium having a computer program stored thereon, the computer program being executable by a processor to implement the steps of the method for measuring the flow rate of tobacco shreds in a wind-powered tobacco feeding duct as claimed in any one of claims 1-6.

8. A device for measuring the flow rate of tobacco shreds in a wind-powered tobacco delivery duct, characterized in that, It includes a capacitance tomography sensor, a sensor measurement circuit, a data acquisition unit, and a computer. The data acquisition unit is used to acquire the voltage scalar V output by the sensor measurement circuit, and the computer has a built-in computer-readable storage medium as described in claim 7.

9. The tobacco flow rate measuring device in the wind-powered tobacco delivery pipe according to claim 8, characterized in that, Multiple sets of capacitance tomography sensors are evenly distributed along the circumference of a cross-section of the pipe. The capacitance tomography sensors are used to measure the flow rate of tobacco in the pipe. Each set of capacitance tomography sensors includes two electrodes, which are arranged on the circumference of a non-conductive pipe section.

10. The tobacco flow rate measuring device in the wind-powered tobacco delivery pipe according to claim 9, characterized in that, The sensor measurement circuit includes capacitors Cs1 and Cs2, which are respectively connected to the two electrodes of the capacitance tomography sensor Cx. One end of capacitor Cs1 is connected to a signal generator Vc, and the other end is grounded. One end of capacitor Cs2 is connected to the negative input terminal of a first operational amplifier, and the other end is grounded. The positive input terminal of the first operational amplifier is grounded, and its output is connected to the negative input terminal of a second operational amplifier after passing through a resistor. The positive input terminal of the second operational amplifier is grounded, and its output voltage scalar V is processed to obtain the tobacco flow in the pipe. Vc is a sine wave signal generator. Capacitors and resistors for filtering are connected in parallel directly at the negative input terminals and output terminals of the first and second operational amplifiers.

Images