Capacitive sensor, device and method for double-sleeve particle conveying detection

Abstract

The invention discloses a capacitive sensor, device and method for double-sleeve particle conveying detection, the capacitive flow sensor comprises an outer sleeve, a tubular excitation electrode, a first detection electrode and a second detection electrode, the tubular excitation electrode is arranged on the inner side of the outer sleeve, and the first detection electrode is arranged on the outer sleeve; the tubular excitation electrode is used for being connected with an excitation source to generate an excitation signal; the first detection electrode and the second detection electrode are arranged at different positions in the axial direction of the outer sleeve through an isolating ring; the first detection electrode and the second detection electrode are used for respectively acquiring detection signals of the excitation signals acting on powder particles, so that the special structure of the ash conveying double sleeve can be well adapted, and the technical bottleneck that a traditional sensor cannot be applied to the ash conveying double sleeve is effectively solved; and a solution is provided for accurately measuring the flow in the ash conveying double sleeve.

Description

Technical Field

[0001] The present invention relates to the field of powder particle transportation, and particularly to a capacitive flow measurement method and device applicable to a double-tube powder particle transportation system. Background Art

[0002] An electrostatic precipitator is an important device used in coal-fired power plants to treat the coal ash dust generated after combustion. It is widely used to reduce the emission of coal ash particles in flue gas and lower air pollution. It charges the coal ash dust in the flue gas through a high-voltage electric field, and then uses the dust collection electrode to capture the dust particles to achieve efficient dust removal. The coal ash dust collected by the electrostatic precipitator needs to be transported to the ash bunker through an ash transportation system, and this process is a super-dense-phase gas transportation. Due to the high concentration of dust particles and the significant interaction between gas and solid, problems such as dust accumulation and incomplete gas-solid separation often occur in the ash transportation pipeline, which not only reduces the ash transportation efficiency but also easily causes pipeline blockage, seriously affecting the stability of the system operation. To solve the above problems, a double-tube structure is widely used in modern ash transportation systems. The double-tube design features an inner tube installed inside the dense-phase transportation pipe. By introducing the transportation air flow into the inner tube and using the function of the perforated disc to generate turbulence in the pipeline, it promotes the full mixing and fluidization of the material and gas. This structure can effectively reduce the deposition and blockage of dust in the pipeline, thereby improving the fluidity and stability of the ash transportation system.

[0003] However, due to the special nature of the double-tube structure, traditional flow measurement sensors cannot be applied to the ash transportation double-tube system, making it difficult to accurately obtain the ash transportation flow data and unable to provide a solid and reliable basis for the optimization and control of the ash transportation system. This not only affects the real-time monitoring of the system but also restricts the optimized operation of the ash transportation system. In summary, for the ash transportation system with a double-tube structure, there is an urgent need to develop a flow measurement method and device adapted to its special structure, which can provide accurate flow data under complex super-dense-phase gas transportation conditions and provide technical support for the precise monitoring and optimization control of the ash transportation system. Summary of the Invention

[0004] In view of the above problems, based on the structure of the ash transportation double-tube, the present invention proposes a capacitive flow sensor, device and method for a double-tube powder particle transportation system. The aim is to provide a precise and effective flow measurement solution for the ash transportation double-tube system, thereby giving full play to the advantages of the ash transportation double-tube, solving its flow measurement problem, and meeting the requirements of accurate monitoring and management of the ash transportation process in industrial production.

[0005] Technical Solution

[0006] To solve the above technical problems, the technical solution adopted by the present invention is:

[0007] The present invention first provides a capacitive flow sensor for a double-tube powder particle transportation system, including:

[0008] An outer sleeve having the same inner diameter as the transport pipe of the double-sleeve powder particle conveying system, for connecting with the transport pipe of the double-sleeve powder particle conveying system to allow the powder particles conveyed by the transport pipe to flow through;

[0009] A tubular excitation electrode is arranged inside the outer sleeve and has an inner channel through which air flows; the position of the tubular excitation electrode in the outer sleeve is the same as the position of the inner pipe of the transport pipe in the double-sleeve powder particle conveying system in the transport pipe; the tubular excitation electrode is used to connect to an excitation source to generate an excitation signal;

[0010] A first detection electrode and a second detection electrode are arranged at different positions in the axial direction of the outer sleeve through an isolation ring; the first detection electrode and the second detection electrode are used to respectively obtain detection signals of the excitation signal acting on the powder particles;

[0011] An insulating liner is arranged between the tubular excitation electrode and the outer sleeve for insulating between the tubular excitation electrode and the two detection electrodes on the outer sleeve.

[0012] Flanges for connecting the outer sleeve of the double-sleeve powder particle conveying system are arranged at both ends of the outer sleeve.

[0013] A shielding cover is further arranged on the outer side of the outer sleeve; the two detection electrodes are arranged inside the shielding cover.

[0014] The tubular excitation electrode includes a conductive sleeve and a lead end arranged on the conductive sleeve; the lead end passes through the outer sleeve and the shielding cover.

[0015] The present invention further provides a flow measurement system for a double-sleeve powder particle conveying system, including:

[0016] The capacitive flow sensor for the double-sleeve powder particle conveying system provided above;

[0017] An excitation source, connected to the tubular excitation electrode of the capacitive flow sensor for generating an excitation signal on the tubular excitation electrode;

[0018] A signal processing circuit, connected to the two detection electrodes of the capacitive flow sensor, processes the obtained detection signals to obtain the powder particle flow rate.

[0019] The signal processing circuit includes a signal conditioning circuit and a digital signal acquisition and processing circuit; the signal conditioning circuit converts the capacitance signal output by the detection electrode into a voltage signal suitable for analog circuit processing; the digital signal processing circuit calculates the particle flow parameters according to the converted voltage signal.

[0020] The digital signal processing circuit calculates particle flow parameters based on the converted voltage signal, including:

[0021] Obtaining the particle mass concentration according to the converted voltage signal;

[0022] Calculating the particle velocity by performing cross-correlation analysis on the voltage signal;

[0023] Calculating the mass flow rate of the particles based on the obtained particle mass concentration and particle velocity.

[0024] The step of obtaining the particle mass concentration according to the converted voltage signal includes:

[0025] Calculating the average value of the extracted voltage signal:

[0026]

[0027] Wherein, and are the average values of the voltage signals V Cx and V Cy respectively, f is the sampling frequency, N is the number of samples, x i and y i are the sequences of V Cx and V Cy respectively;

[0028] Obtaining the particle mass concentration β according to the calculated average value of the voltage signal:

[0029]

[0030] Wherein, V c0 is the voltage signal in the empty tube state, and f() represents the response of the measurement system to the particle concentration.

[0031] The step of calculating the particle velocity by performing cross-correlation analysis on the voltage signal includes:

[0032] Performing mean removal processing on the output voltage signal:

[0033]

[0034] Wherein, xx i and yy i are the voltage signal sequences of the first detection electrode and the second detection electrode after mean removal respectively;

[0035] After mean removal processing, performing cross-correlation analysis on the signals xx i and yy i The cross-correlation function R(n) is expressed as:

[0036]

[0037] Among them, n is the number of time delay points; the sampling delay point corresponding to the first maximum peak point of the cross-correlation function except the zero point is denoted as M, then the particle flow velocity v is calculated according to the following:

[0038]

[0039] Among them, L is the center distance between the two detection electrodes.

[0040] The present invention also provides a flow measurement method for a double-tube powder particle conveying system, including:

[0041] Obtain the capacitance signals detected by the first detection electrode and the second detection electrode respectively;

[0042] Convert the detected capacitance signal into a voltage signal;

[0043] Calculate the average value of the voltage signal:

[0044]

[0045] Among them, and are the average values of the voltage signals V Cx and V Cy respectively, f is the sampling frequency, N is the number of samplings, x i and y i are the sequences of V Cx and V Cy respectively;

[0046] According to the calculated average value of the voltage signal, obtain the particle mass concentration β:

[0047]

[0048] Among them, V C0 is the voltage signal in the empty tube state, f() represents the response of the measurement system to the particle concentration; f() can obtain a series of measurement points by filling a certain amount of particles in the sensitive area of the sensor and determine the functional relationship between them through curve fitting. Through the above calibration process, the concentration of particles can be accurately determined according to the average value of the capacitance signal.

[0049] Perform de-averaging processing on the output voltage signal:

[0050]

[0051] Among them, xx i and yy iThe voltage signal sequences of the first and second detection electrodes after detrending, respectively;

[0052] After the detrending process, for the signals xx i and yy i perform cross-correlation analysis. The cross-correlation function R(n) is expressed as:

[0053]

[0054] where n is the number of time delay points; the sampling delay point corresponding to the first maximum peak point of the cross-correlation function except the zero point is denoted as M, then the particle flow velocity v is calculated according to the following:

[0055]

[0056] where L is the center distance between the two detection electrodes;

[0057] According to the obtained particle mass concentration and particle velocity, calculate the mass flow rate of the particles:

[0058] M = A·v·β

[0059] In the formula, M is the mass flow rate of the particles; A is the cross-sectional area of the sensor device.

[0060] Compared with the prior art, the present invention has the following advantages:

[0061] 1. The double-sleeve capacitive flow measurement method and device of the present invention are designed based on the structure of the ash conveying double sleeve. Compared with the existing conventional ash conveying measurement sensors, it can well adapt to the special structure of the ash conveying double sleeve, effectively solving the technical bottleneck that traditional sensors cannot be applied to the ash conveying double sleeve, and providing a solution for accurately measuring the flow rate in the ash conveying double sleeve.

[0062] 2. In this measurement device, the inner sleeve is innovatively used as the excitation electrode. This unique design effectively reduces signal interference and noise effects, can form a more uniform and stable electric field environment in the measurement space, enabling the detection electrode to more sensitively capture the weak capacitance value changes caused by fluid flow rate changes, greatly improving the sensitivity of the detection electrode, and thus providing more accurate and detailed data feedback for flow measurement, significantly enhancing the accuracy and reliability of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a schematic structural diagram of the capacitive flow sensor of the present invention;

[0064] Figure 2 is a schematic block diagram of the flow measurement system for the double-sleeve powder particle conveying system of the present invention;

[0065] Figure 3 It is a schematic diagram of the application of the capacitive flow sensor of the present invention.

[0066] Wherein: 1. Tubular excitation electrode; 2. First detection electrode; 3. Second detection electrode; 4. Outer sleeve; 5. Shielding cover; 6. Isolation ring; 7. Insulating liner; 8. Insulating sleeve; 9. Lead end of the excitation electrode; 10. Nut; 11. Lead boss; 12. Lead tube; 13. Circuit housing; 14. Flange; 15. Transport pipe; 16. Inner tube of the transport pipe; 17. Flange of the transport pipe. Specific embodiments

[0067] Embodiment 1

[0068] This embodiment provides a capacitive flow sensor for a double-sleeve powder particle conveying system. Refer to Figure 1 , including:

[0069] An outer sleeve 4, having the same inner diameter as the transport pipe 15 of the double-sleeve powder particle conveying system, for connecting with the transport pipe of the double-sleeve powder particle conveying system to allow the powder particles conveyed by the transport pipe to flow through;

[0070] A tubular excitation electrode 1, arranged inside the outer sleeve 4, having an inner channel through which air flows; the position of the tubular excitation electrode 1 in the outer sleeve 4 is the same as the position of the inner tube 16 of the transport pipe in the transport pipe 15 of the double-sleeve powder particle conveying system; the tubular excitation electrode 1 is used to connect to an excitation source to generate an excitation signal;

[0071] A first detection electrode 2 and a second detection electrode 3, arranged at different positions axially on the outer sleeve 4 through an isolation ring 6; the first detection electrode 2 and the second detection electrode 3 are used to respectively obtain detection signals of the excitation signal acting on the powder particles;

[0072] An insulating liner 7, arranged between the tubular excitation electrode 1 and the outer sleeve 4, for insulating between the tubular excitation electrode 1 and the two detection electrodes on the outer sleeve 4.

[0073] In order to facilitate the connection of the capacitive flow sensor to the conveying pipe of the double-sleeve powder particle conveying system, flanges 14 for connecting the outer sleeves of the double-sleeve powder particle conveying system are arranged at both ends of the outer sleeve.

[0074] A shielding cover 5 is further arranged outside the outer sleeve 4; the two detection electrodes are arranged inside the shielding cover 5.

[0075] In order to facilitate the lead-out of the tubular excitation electrode, the tubular excitation electrode includes a conductive sleeve and a lead end 9 of the excitation electrode arranged on the conductive sleeve; the lead end 9 of the excitation electrode passes through the outer sleeve 4 and the shielding cover 5.

[0076] Embodiment 2

[0077] This embodiment provides a double - sleeve capacitive flow measurement system, which consists of two parts: a double - sleeve capacitive flow sensor and a signal processing circuit. The structural schematic diagram of the double - sleeve capacitive flow sensor is as shown in Figure 1 Figure [not shown in the original text, should be filled in according to the actual figure], and it includes a shielding cover, an outer sleeve, a tubular excitation electrode, a flange, an insulating material, two detection electrodes, a lead boss, a wire conduit, and a circuit housing. According to the ash - conveying double - sleeve structure, the sensor's tubular excitation electrode is connected to the inner sleeve of the ash - conveying double - sleeve, and air is conveyed inside it. The inside of the outer sleeve is a detection channel. The tubular excitation electrode is energized to form capacitances with the two detection electrodes respectively. The two detection electrodes are arranged at intervals along the axial direction of the sensor's tubular excitation electrode tube and are in direct contact with the detection channel. Between the two detection electrodes and between the excitation electrode and the detection electrodes, there are insulating material rings for isolation to ensure the electrical insulation performance between the electrodes and fix the electrode positions.

[0078] When the double - sleeve capacitive flow measurement system is in use, referring to Figure 3 Figure [not shown in the original text, should be filled in according to the actual figure], the capacitive flow sensor is connected through the transportation pipe flange 17 and the flange 14 on the capacitive flow sensor, so as to install the capacitive flow sensor on the transportation pipe.

[0079] From the perspective of the capacitive sensor, a capacitance C x is formed between the tubular excitation electrode and the first detection electrode, and a capacitance C y is formed between the tubular excitation electrode and the second detection electrode. When the capacitance signal is used for particle concentration measurement, for a known sensor measurement device, the measured equivalent capacitance is mainly affected by factors such as particle concentration, types of gas and solid. Generally, the measurement of particle concentration needs to be achieved through calibration.

[0080] The signal processing circuit is as shown in Figure 2 Figure [not shown in the original text, should be filled in according to the actual figure], and it mainly consists of a signal conditioning circuit and a digital signal acquisition and processing circuit. The signal conditioning circuit converts the capacitance signal output by the detection electrode into a voltage signal suitable for analog circuit processing:

[0081]

[0082] where V Cx0 (t) is the voltage signal between the processed tubular excitation electrode and the first detection electrode, V Cy0 (t) is the voltage signal between the processed tubular excitation electrode and the second detection electrode, ω is the frequency of the excitation signal; V s (t) is the high - frequency alternating voltage applied to the tubular excitation electrode generated by the DDS signal generator; R f is the feedback resistor; C f is the feedback capacitor.

[0083] To optimize the signal quality, the converted voltage signals V Cx0 and V Cy0 are successively connected to a band - pass filter and an amplitude converter to obtain voltage signals V Cx and V Cy : The band - pass filter is used to filter out low - frequency ambient noise and high - frequency interference outside the preset frequency band, retain the effective frequency band of the target signal, and ensure the accuracy and stability of the signal; the amplitude converter dynamically adapts the signal amplitude to ensure that it meets the input dynamic range of the digital signal acquisition and processing circuit. The processed signal is collected, analyzed, and output through a digital circuit, and finally, high - precision and anti - interference detection signal processing is achieved.

[0084] For the voltage signals V Cx and V Cy of the first detection electrode and the second detection electrode after processing, the signal sequences collected at the sampling frequency f are x i and y i respectively, and the average values of the signal sequences are:

[0085]

[0086] The relationship between the particle mass concentration β and the voltage signal V c can be expressed as:

[0087]

[0088] where V C0 is the voltage signal in the empty - tube state, and f() represents the response of the measurement system to the particle concentration. By filling a certain amount of particles in the sensitive area of the sensor, a series of measurement points can be obtained and the functional relationship between them can be determined by curve fitting. Through the above calibration process, the particle concentration can be accurately measured according to the average value of the voltage signal.

[0089] The particle velocity can be calculated by performing cross - correlation analysis on the voltage signal. First, the average value of the output voltage signal is removed, that is:

[0090]

[0091] where xx i and yy i are the voltage signal sequences of the first detection electrode and the second detection electrode after removing the average value respectively.

[0092] After removing the average value, cross - correlation analysis is performed on the signals xx i and yy i after removing the average value, and the cross - correlation function R(n) can be expressed as:

[0093]

[0094] Among them, n is the number of time delay points. The sampling delay point corresponding to the first maximum peak point of the cross-correlation function except the zero point is denoted as M, then the particle flow velocity v can be calculated according to the following:

[0095]

[0096] Among them, L is the center distance between the two detection electrodes.

[0097] A more accurate particle concentration value can be obtained by calculating the average value of the two concentration calibration results obtained by the two detection electrodes. After the velocity and concentration of the particles are known, the mass flow rate M of the particles can be calculated:

[0098]

[0099] In the formula, A is the cross-sectional area of the sensor device, is the function coefficient between the particle concentration and the output voltage of the capacitance measurement circuit, V is the particle movement velocity, is the average value of the collected voltage signals, V C0 is the voltage signal in the empty tube state. After obtaining the particle velocity and the output voltage of the capacitance measurement circuit, the function coefficient between the particle concentration and the output voltage of the capacitance measurement circuit can be determined by calibration to calculate the particle mass flow rate.

Claims

1. A capacitive flow sensor for a double-tube powder particle conveying system, characterized in that: include: The outer sleeve has the same inner diameter as the transport pipe of the double-sleeve powder particle transport system and is used to connect with the transport pipe of the double-sleeve powder particle transport system so that the powder particles transported by the transport pipe flow through; A tubular excitation electrode is arranged inside the outer sleeve and has an inner passage through which air flows; the position of the tubular excitation electrode in the outer sleeve is the same as the position of the inner tube of the transport tube of the double-tube powder particle conveying system in the transport tube; the tubular excitation electrode is used to connect to an excitation source to generate an excitation signal; The first detection electrode and the second detection electrode are arranged at different axial positions of the outer sleeve through an isolation ring; the first detection electrode and the second detection electrode are used to respectively obtain detection signals of the excitation signal acting on the powder particles; The insulating liner is arranged between the tubular excitation electrode and the outer sleeve and is used for insulation between the tubular excitation electrode and the two detection electrodes on the outer sleeve.

2. The capacitive flow sensor for a double-tube powder particle conveying system according to claim 1, characterized in that: Flanges for connecting the outer sleeves of a double-sleeve powder particle conveying system are arranged at both ends of the outer sleeve.

3. The capacitive flow sensor for a double-tube powder particle conveying system according to claim 1, characterized in that: A shielding cover is also arranged on the outside of the outer sleeve; two detection electrodes are arranged in the shielding cover.

4. The capacitive flow sensor for a double-tube powder particle conveying system according to claim 3 is characterized in that: The tubular excitation electrode comprises a conductive sleeve and a lead end arranged on the conductive sleeve; the lead end passes through the outer sleeve and the shielding cover.

5. A flow measurement system for a double-tube powder particle conveying system, characterized in that: include: A capacitive flow sensor for a double-tube powder particle conveying system according to any one of claims 1 to 4; an excitation source connected to the tubular excitation electrode of the capacitive flow sensor and used to generate an excitation signal on the tubular excitation electrode; The signal processing circuit is connected to the two detection electrodes of the capacitive flow sensor, and processes the acquired detection signal to obtain the powder particle flow rate.

6. The flow measurement system for a double-tube powder particle conveying system according to claim 5, characterized in that: The signal processing circuit includes a signal conditioning circuit and a digital signal acquisition and processing circuit; the signal conditioning circuit converts the output capacitance signal of the detection electrode into a voltage signal suitable for analog circuit processing; the digital signal processing circuit calculates the particle flow parameters based on the converted voltage signal.

7. The flow measurement system for a double-tube powder particle conveying system according to claim 6, characterized in that: The digital signal processing circuit calculates the particle flow parameters according to the converted voltage signal, including: According to the converted voltage signal, the particle mass concentration is obtained; The particle velocity is calculated by cross-correlation analysis of the voltage signal; The mass flow rate of the particles is calculated based on the obtained particle mass concentration and particle velocity.

8. The flow measurement system for a double-tube powder particle conveying system according to claim 7, characterized in that: According to the converted voltage signal, the particle mass concentration step is obtained, including: Calculate the average value of a voltage signal: in, and They are voltage signals V Cx and V Cy The average value, f is the sampling frequency, N is the number of samples, x i and i They are voltage signals V Cx and V Cy sequence; According to the average value of the extracted voltage signal, the particle mass concentration β is obtained: Among them, V C0 is the voltage signal in the empty tube state, and f() represents the response of the measurement system to the particle concentration.

9. The flow measurement system for a double-tube powder particle conveying system according to claim 7, characterized in that: The steps of calculating the particle velocity by cross-correlation analysis of the voltage signal include: Perform the average value processing on the output capacitance signal: Among them, xx i and yy i are respectively the voltage signal sequences of the first detection electrode and the second detection electrode after averaging; After the average value is removed, the average value of the signal xx is i and yy i Perform cross-correlation analysis, and the cross-correlation function R(n) is expressed as: Where n is the number of time delay points; the number of sampling delay points corresponding to the first maximum peak point of the cross-correlation function except the zero point is recorded as M, and the particle flow velocity v is calculated according to the following: Wherein, L is the center distance between two detection electrodes.

10. A flow measurement method for a flow measurement system for a double-tube powder particle conveying system according to any one of claims 5 to 9, characterized in that: include: Respectively acquiring capacitance signals detected by the first detection electrode and the second detection electrode; Convert the detected capacitance signal into a voltage signal; Calculate the average value of a voltage signal: in, and They are voltage signals V Cx and V Cy The average value, f is the sampling frequency, N is the number of samples, x i and i V Cx and V Cy sequence; According to the calculated average value of the voltage signal, the particle mass concentration β is obtained: Among them, V C0 is the voltage signal in the empty tube state, and f() represents the response of the measurement system to the particle concentration; Perform average value processing on the output voltage signal: Among them, xx i and yy i are respectively the voltage signal sequences of the first detection electrode and the second detection electrode after averaging; After the average value is removed, the average value of the signal xx is i and yy i Perform cross-correlation analysis, and the cross-correlation function R(n) is expressed as: Where n is the number of time delay points; the number of sampling delay points corresponding to the first maximum peak point of the cross-correlation function except the zero point is recorded as M, and the particle flow velocity v is calculated according to the following: Wherein, L is the center distance between two detection electrodes; According to the obtained particle mass concentration and particle velocity, the mass flow rate of the particles is calculated: M = A·v·β Where M is the mass flow rate of particles; A is the cross-sectional area of ​​the sensor device.

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