A method for spatial sensitivity homogenization of electrostatic sensors

Abstract

This invention discloses a method for homogenizing the spatial sensitivity of an electrostatic sensor, belonging to the field of online gas-solid two-phase flow measurement technology. This method involves placing a thicker insulating layer between a non-invasive electrode and the inner wall of the pipe, increasing the distance between the electrode and the inner wall. Utilizing the characteristic that spatial sensitivity changes more slowly at greater distances from the electrode, the method aims to achieve a more uniform spatial sensitivity distribution within the pipe. Simultaneously, it increases the voltage gain of the electrostatic sensor's signal conditioning circuit to compensate for the sensitivity loss caused by the insulating layer, resulting in a sufficiently strong electrostatic signal. This invention enables the induced charge generated on the electrode by particles at different locations within the cross-section of a pneumatic conveying pipe to become more consistent, thereby improving the accuracy of pneumatic powder flow parameter measurements.

Description

Technical Field

[0001] This invention falls within the scope of online measurement technology for gas-solid two-phase flow, and specifically relates to a method for homogenizing the spatial sensitivity of an electrostatic sensor. Background Technology

[0002] In pneumatic powder conveying, moving particles acquire a certain amount of static charge due to collisions and friction. Electrostatic sensors can detect the fluctuating electric field caused by these charged particles, enabling online measurement of parameters such as particle velocity, concentration, and mass flow rate. However, the spatial sensitivity of electrostatic sensors is non-uniform; the amount of induced charge on the electrode by charged particles depends on the distance between the particle and the electrode—the closer the distance, the greater the induced charge. Therefore, particles near the inner wall of the pneumatic conveying pipeline play a dominant role in generating the electrostatic signal. Furthermore, the powder concentration and velocity distribution within the pneumatic conveying pipeline is uneven. The flow parameters measured by the electrostatic sensor mainly reflect the flow state near the inner wall and cannot represent the overall flow state inside the pipeline, leading to significant measurement errors.

[0003] To address the aforementioned problems, this invention proposes a method for homogenizing the spatial sensitivity of an electrostatic sensor. Since the spatial sensitivity of an electrostatic sensor tends to become more uniform with increasing distance from the electrode, this invention proposes to reduce the non-uniformity of spatial sensitivity within the pipe by increasing the distance between the non-invasive electrode and the inner wall of the pipe. Simultaneously, it increases the voltage gain of the electrostatic sensor signal conditioning circuit to compensate for the sensitivity loss caused by the increased distance. This invention enables the amount of induced charge generated on the electrode by particles at different locations within the cross-section of the pneumatic conveying pipe to become more consistent, thereby reducing the measurement error of pneumatic powder flow parameters, especially effective in conditions with large pipe diameters and uneven powder distribution. Summary of the Invention

[0004] The purpose of this invention is to provide a method for homogenizing the spatial sensitivity of an electrostatic sensor. The electrostatic sensor comprises a non-invasive electrode and a signal conditioning circuit. A thick insulating layer is provided between the non-invasive electrode and the inner wall of the pipe to reduce the non-uniformity of the spatial sensitivity inside the pipe. The signal conditioning circuit has sufficient voltage gain to compensate for the sensitivity loss caused by the insulating layer.

[0005] The insulating layer should preferably be made of an insulating material with a large dielectric constant to improve the spatial sensitivity uniformity effect, reduce the insulating layer thickness and electrode size.

[0006] The non-uniformity of spatial sensitivity within the pipe can be measured by the relative difference in spatial sensitivity between the inner wall and the center of the pipe, i.e.

[0007]

[0008] Among them, S r S0 and S0 represent the spatial sensitivity of the inner wall and the center of the pipe, respectively. The selection of the insulation material and thickness should be such that Δ is less than 10%.

[0009] The signal conditioning circuit uses a transimpedance amplifier to convert the induced current signal into a voltage signal. The feedback resistor of the transimpedance amplifier has a sufficiently large resistance value to obtain a high voltage gain. The signal conditioning circuit can also use a charge amplifier to convert the induced charge signal into a voltage signal. The feedback capacitor of the charge amplifier has a sufficiently small capacitance value to obtain a high voltage gain.

[0010] The beneficial effects of this invention are: it can improve the uniformity of spatial sensitivity within the pipe cross-section, making the contribution of charged particles at different locations to the electrostatic signal more consistent, which is beneficial to improving the measurement accuracy of powder flow parameters. Attached Figure Description

[0011] Figure 1 The curve shows the radial distribution of the spatial sensitivity of the electrostatic sensor without an insulating layer.

[0012] Figure 2 The image shows the radial distribution curve of the spatial sensitivity of the electrostatic sensor when an insulating layer is present.

[0013] Figure 1 , 2 In the middle: 1. Electrode; 2. Insulating layer; 3. Pipe; 4. Particle; 5. Spatial sensitivity radial distribution curve. Detailed Implementation

[0014] This invention provides a method for spatial sensitivity uniformity of an electrostatic sensor. The invention is described below with reference to the accompanying drawings and embodiments:

[0015] Figure 1 The figure shows the radial distribution curve of the spatial sensitivity of the electrostatic sensor when there is no insulating layer between the electrode and the inner wall of the pipe. In the figure, electrode 1 is flush with the inner wall of pipe 3, and non-invasive measurement of particles 4 inside pipe 3 is performed. Insulating layer 2 insulates electrode 1 from pipe 3. Through finite element numerical simulation or theoretical model analysis, the radial distribution curve 5 of the spatial sensitivity of the electrostatic sensor can be obtained, and its shape depends on the ratio of the axial width of the electrode to the pipe diameter. It can be seen that the spatial sensitivity of the electrostatic sensor is extremely non-uniform along the radial direction, and the spatial sensitivity near the inner wall is much higher than that at the center of the pipe, causing the signal of the electrostatic sensor to be mainly generated by particles near the inner wall.

[0016] Figure 2The figure shows the radial distribution curve of the spatial sensitivity of the electrostatic sensor when there is a thick insulating layer between the electrode and the inner wall of the pipe. Because there is a certain distance between electrode 1 and the inner wall of pipe 3, and the spatial sensitivity changes more slowly at a greater distance from the electrode, the radial distribution of spatial sensitivity tends to be uniform. By selecting appropriate insulating materials and insulating layer thickness, the radial distribution of spatial sensitivity can be adjusted, making the contribution of particles at different locations on the pipe cross-section to the electrostatic signal more consistent.

[0017] Compare Figure 1 , 2 As can be seen from the radial distribution curve of spatial sensitivity in Figure 5, Figure 2 The middle insulation layer 2 reduces the spatial sensitivity within the cross-section of pipe 2. Therefore, the voltage gain of the electrostatic sensor signal conditioning circuit should be increased to compensate for the loss of spatial sensitivity in order to obtain an electrostatic signal with sufficient strength.

Claims

1. A method for uniformizing the spatial sensitivity of an electrostatic sensor, characterized in that, The electrostatic sensor consists of a non-invasive electrode and a signal conditioning circuit; a thick insulating layer is provided between the non-invasive electrode and the inner wall of the pipe to reduce the non-uniformity of sensitivity in the internal space of the pipe; the signal conditioning circuit has sufficient voltage gain to compensate for the sensitivity loss caused by the insulating layer. The non-uniformity of spatial sensitivity within the pipe can be measured by the relative difference in spatial sensitivity between the inner wall and the center of the pipe, i.e. Among them, S r S0 and S0 represent the spatial sensitivity of the inner wall and the center of the pipe, respectively. The selection of the insulation material and thickness should be such that Δ is less than 10%.

2. The method for uniformizing the spatial sensitivity of an electrostatic sensor according to claim 1, characterized in that, The insulating layer should preferably be made of an insulating material with a large dielectric constant to improve the spatial sensitivity uniformity effect, reduce the insulating layer thickness and electrode size.

3. The method for uniformizing the spatial sensitivity of an electrostatic sensor according to claim 1, characterized in that, The signal conditioning circuit uses a transimpedance amplifier to convert the induced current signal into a voltage signal. The feedback resistor of the transimpedance amplifier has a sufficiently large resistance value to obtain a high voltage gain. The signal conditioning circuit can also use a charge amplifier to convert the induced charge signal into a voltage signal. The feedback capacitor of the charge amplifier has a sufficiently small capacitance value to obtain a high voltage gain.

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