Performance evaluation of conductivity wire-mesh sensors in vertical channels

In order to maintain safe and efficient operation of a fluidized bed, the electrostatic charges in the bed should be monitored continuously. Electrostatic sensors with wire-mesh electrodes are introduced in this paper to measure the charge distribution in the cross section of a fluidized bed. A finite element model is built to investigate the sensing characteristics of the wire-mesh sensors. In comparison with conventional electrostatic sensors, wire-mesh sensors have higher and more uniform sensitivity distribution. Based on the induced charges on the electrodes and the sensitivity distributions of the sensors, the charge distribution in the cross section of the fluidized bed is reconstructed. However, it is difficult to directly measure the induced charges on the electrodes. A charge calibration process is conducted to establish the relationship between the induced charge on the electrode and the electrostatic signal. Experimental studies of charge distribution measurement were conducted on a lab-scale bubbling fluidized bed. The electrostatic signals from the wire-mesh sensors in the dense phase and splash regions of the bed for different fluidization air flow rates were obtained. Based on the results obtained from the charge calibration process, the estimated induced charges on the electrodes are calculated from the root-mean-square values of the electrostatic signals. The characteristics of the induced charges on the electrodes and the charge distribution in the cross section under different flow conditions are investigated, which proves that wire-mesh electrostatic sensors are able to measure the charge distribution in the bubbling fluidized bed.

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Measurement of Charge Distributions in a Bubbling Fluidized Bed Using Wire-Mesh Electrostatic Sensors

The invention relates to a device and method for measuring the grain flow velocity field, and the device comprises a horizontal rotating table, a roller, a light source part, an image collection part, and a computer. The method comprises the following steps: 1, collecting an image of a grain flow on the surface of a fluidized bed; 2, segmenting the image into a plurality of measurement subregions; 3, carrying out the spatial filtering, carrying out the traversal of all measurement subregions, and obtaining a spatial filtering original signal; 4, carrying out the spectrum analysis of the original signal, obtaining the signal spectrum, correcting the signal spectrum, obtaining the central frequency of the signal, and obtaining the speed of the measurement subregions through calculation; 5, repeatedly carrying out the steps 2, 3, 4 for all sample points, obtaining the speed of the whole measurement region, and achieving the measurement of the velocity field of the grain flow. The device is simple in debugging, does not need a complex optical lens and a complex transmission grating, and solves a problem that the conventional spatial filtering cannot solve a problem of the measurement of the velocity field.

Device and method for measuring grain flow velocity field

The invention discloses a method for detecting the dynamic material level in a fluidized bed. The method comprises steps as follows: 1) an inductive type electrostatic sensor array is used for continuously acquiring inductive electrostatic pressure signals in the gas-solid fluidized bed; 2) related speeds of particles are calculated by means of the inductive electrostatic pressure signals detected by upstream and downstream adjacent electrodes, and normalized probability density distribution at the related speeds is acquired; 3) normalized probability density distribution characteristics of the particles at related speeds detected by the electrodes in different axial positions are contrasted, and the dynamic material level fluctuation interval is obtained. The method has the characteristics of high precision, on-line property and noninvasive property, and equipment is simple in structure and wide in applicability.

Method for detecting dynamic material level in fluidized bed

The invention provides an analyzer for the on-line measurement of boiler pipeline pulverized coal flow parameters. The analyzer comprises a signal conditioning unit, an AD acquisition unit, an FPGA dispatching unit, a CPU control unit, a communication unit, a power supply unit and a working status indicating unit. The signal conditioning unit converts 10 paths of sensor weak electric signals into voltage signals and transmits the voltage signals to the AD acquisition unit. The FPGA dispatching unit controls the collection and data caching of the AD acquisition unit and carries out data real-time interaction with a CPU. The CPU control unit is responsible for the task scheduling, data calculation and data interaction of the whole analyzer. The communication unit transmits measurement data and a result to a host computer in real time. The analyzer has the advantages of low cost, long-term and stable operation and a high precision of a calculation result and meets the application requirements of an industrial site.

Analyzer for on-line measurement of boiler pipeline pulverized coal flow parameters

The invention discloses a fluidized bed mixed particle detection device and a fluidized bed mixed particle detection method based on an electrostatic and photoelectric sensor, and belongs to the field of gas-solid multi-phase flow parameter detection. According to the fluidized bed mixed particle detection device, an arc-shaped electrostatic sensor and a photoelectric excited and detection array are respectively mounted on the outer wall of a fluidized bed pipeline; the arc-shaped electrostatic sensor is connected with a cross-correlation calculating module through an electrostatic signal regulating module; the photoelectric excited and detection array is connected with a photoelectric signal exciting module, a photoelectric signal regulating module and a signal characteristic extraction module; the photoelectric signal regulating module and the electrostatic signal regulating module are used for transforming, filtering and amplifying weak photoelectric and electrostatic signals; the cross-correlation calculating module is used for implementing cross-correlation calculation on electrostatic signals of different components at the upper stream and the lower stream; the signal characteristic extraction module is used for extracting parameters associated with mixed particle concentration distribution in a fluidized bed. Therefore, real-time detection on multiple parameters such as flowing speed and concentration distribution of mixed particles in the fluidized bed can be achieved. The fluidized bed mixed particle detection device measures in a non-invasive mode and is simple in structure, low in cost and high in sensitivity.

Fluidized bed mixed particle detection device and method based on electrostatic and photoelectric sensor

The presence of electrostatic charge in a bubbling fluidized bed influences the operation of the bed. In order to maintain an effective operation, the electrostatic charges in different positions of the bed should be monitored. In this paper a wire-mesh electrostatic sensor is introduced to reconstruct the charge distribution in a bubbling fluidized bed. The wire-mesh sensor is fabricated by two mutually perpendicular strands of insulated wires. A Finite Element Model is built to analyze the sensing characteristics of the sensor. The sensitivity distributions of each wire electrode and the whole sensor are obtained from the model, which proves that wire-mesh electrostatic sensor has a higher and more uniform sensitivity distribution than single wire sensors. Experiments were conducted in a gravity drop test rig to validate the reconstruction method. Experimental results show that the charge distribution can be reconstructed when sand particles pass through the cross section of the sensor.

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Binbin Yang

Papers

Fluidized bed mixed particle detection device and method based on electrostatic and photoelectric sensor

Charge distribution reconstruction in a bubbling fluidized bed using a wire-mesh electrostatic sensor