Zhiyao Huang

Application of electrical capacitance tomography to the void fraction measurement of two-phase flow

Based on the electrical capacitance tomography technique, a new method for the void fraction measurement of two-phase flow is proposed. A 12-electrode void fraction measurement system is established. A mathematical model of image reconstruction of electrical capacitance tomography is developed. To obtain the quantitative information of two-phase flow, combining the Tikhonov regularization principle and the algebraic reconstruction technique algorithm, a new image reconstruction algorithm is presented. The experimental results show that the accuracy of void fraction measurement is satisfactory. The proposed method is suitable for the void fraction measurement of many kinds of two-phase flow.

A high-speed data acquisition system for ECT based on the differential sampling method

A new capacitance measuring circuit based on differential sampling methods for electrical capacitance tomography has been developed. The measured capacitance is only charged and discharged once and no noise is created by the measurement principle. A capacitance measurement system for 12 electrodes is constructed based on the new measurement circuit. Test results show the data acquisition time for 66 capacitances (for reconstructing one image) is less than 1.25 ms.

Flow-pattern identification of gas-liquid two-phase flow based on capacitively coupled contactless conductivity detection

Based on a capacitively coupled contactless conductivity detection technique, a new method for the online flow pattern identification of gas-liquid two-phase flow is proposed. This paper includes two parts: First, a new sensor (the single-shield sensor), which is suitable for the parameter measurement of gas-liquid two-phase flow, is developed, and second, with the developed single-shield sensor, the flow pattern identification of gas-liquid two-phase flow is studied by combining the wavelet analysis technique and the support vector machine technique. The experimental results show that the developed single-shield sensor is successful. It has the advantages of low cost, simpler construction, better stability, and better measurement performance. The experimental results also indicate that the proposed flow pattern identification method is effective, and the identification accuracy results are satisfactory. In five different pipes (the inner diameters are 1.8, 2.8, 4, 6.1, and 7.8 mm, respectively), the identification accuracy results for typical flow patterns (stratified, wavy, bubbly, slug, and annular flow) are all above 91%. This paper verifies that is a promising technique for flow pattern identification of gas-liquid two-phase flow, and it may have a broad perspective in related industrial field.

An intelligent measurement system for powder flowrate measurement in pneumatic conveying system

A novel method for the on-line measurement of powder flowrate in pneumatic conveying system is proposed. It is a nonrestrictive method based on the measurement values of total pressure drop of gas-solid two-phase flow and the powder concentration, and also has the advantage of simplicity, reliability and low cost. An intelligent measurement system for the powder flowrate measurement is developed. The experimental results show that the maximum measurement error is satisfactory for industrial application.

A novel electrical resistance tomography system based on C4D technique

For the traditional electrical resistance tomography systems, the contact between the electrodes and liquid may result in electrode corrosion, which limits the application of ERT in industry. In this paper, a new electrical resistance tomography system based on capacitively coupled contactless conductivity technique was developed. The conductivity distribution of liquid between electrodes can be measured without direct contact with the liquid. The data acquisition system is designed based on phase-sensitive demodulation method. Experiment results show that the conductivity distribution images can be reconstructed.

Flow Pattern Identification Based on EMD and LS-SVM for Gas–Liquid Two-Phase Flow in a Minichannel

Based on empirical mode decomposition (EMD) and least squares support vector machine (LS-SVM), a new method is proposed to identify the flow pattern of gas-liquid two-phase flow in a minichannel. Four flow patterns are observed in three pipes with inner diameters of 4.0, 3.1, and 1.8 mm. For each flow pattern, the capacitance signals are obtained by a two-electrode capacitance sensor. The EMD method is applied to the capacitance signal to obtain intrinsic mode functions (IMFs) with different characteristic time scales. For each IMF, the autoregression (AR) model is built to extract multiscale features. Combining the extracted features with the energy feature of each IMF, the flow patterns are identified by the multiclassification LS-SVM classifier. The experimental results indicate that the presented method is effective for flow pattern identification and has identification rates higher than 91%.

A Novel Electrical Resistance Tomography System Based on

For the traditional electrical resistance tomography systems, the contact between the electrodes and liquid may result in electrode corrosion, which limits the application of ERT in industry. In this paper, a new electrical resistance tomography system based on capacitively coupled contactless conductivity technique was developed. The conductivity distribution of liquid between electrodes can be measured without direct contact with the liquid. The data acquisition system is designed based on phase-sensitive demodulation method. Experiment results show that the conductivity distribution images can be reconstructed.

{\rm{C}}^{4}{\rm D}

Process tomography technique provides a novel method to investigate the multi-phase flow distribution inside pipe or vessel. Electrical resistance tomography (ERT) and electrical capacitance tomography (ECT) are extensively studied in recent years. As the capacitance to voltage and resistance to voltage converters run faster, the speeds of other circuits in the system, such as MCU, A/D, D/A etc, have become the bottlenecks of improving the speed. This paper describes a new dual-modal, ECT and ERT, data acquisition system. The system is controlled by a digital signal processor. Both the ERT and the ECT systems use one platform to simplify the system design and maintenance. The system can work at high speed which is only limited by the capacitance to voltage converter or resistance to voltage converter. Primary test results show the speed of the new system is 1400 frames/second for 16-electrode ERT and 2200 frames/second for 12-electrode ECT.

Technique

Based on the capacitances obtained from a 12-electrode electrical capacitance tomography (ECT) system and the least-squares support vector machine (LS-SVM) technique, a new method is proposed for the online voidage measurement of the gas-oil two-phase flow. In the practical voidage-measurement process, the real-time flow pattern of the gas-oil two-phase flow is directly identified from 66 capacitances obtained from the ECT system. Then, according to the flow pattern-identification results, a suitable measurement model is selected, and the voidage value is calculated. Both static and dynamic experimental results show that the proposed method is effective. The voidage-measurement result is independent of the flow pattern, and the real-time performance is satisfactory. Meanwhile, compared with the conventional voidage-measurement method based on an ECT system, the proposed method can produce more accurate voidage measurement without going through an image-reconstruction process.

Design of high-speed ECT and ERT system

The performance of a hybrid flow meter for the measurement of oil-water two-phase flow rates is investigated. The hybrid flow meter consists of a venturi meter and an oval gear flow meter. Experimental investigations were undertaken on horizontal pipelines of 15 mm, 25 mm, and 40 mm diameters on an oil-water two-phase flow loop. The total flow rate of the oil-water two-phase flow is in the range of 1.2 ∼ 5.5 m3/h, while the oil volume fraction varies from 0 to 100%. The research verifies that the hybrid flow meter is feasible for oil-water two-phase flow measurement and the accuracy of the hybrid flow meter is satisfactory. Experimental results also indicate that the oil fraction has a significant impact on the selection of the meter coefficient of the venturi and hence the measurement results of density and total mass flow rate.