Cross-correlation Velocity Measurement Research Articles

A D-norm cross-correlation method for particle velocity measurement through electrostatic sensing

The cross-correlation (CC) method is conventionally used for measuring the velocity of gas–solid flows using electrostatic sensors, wherein velocity measurement is transformed into a time-delay estimation problem. However, owing to the intricacies of signals in gas–solid flows, the cross-correlation function may exhibit multiple peaks, resulting in peak misjudgment and time-delay estimation bias. To address these issues, this paper proposes a D-norm cross-correlation (DCC) velocity measurement method and applies it to flow velocity measurements in pneumatic conveying. Such a technique leverages the sensitivity of D-norm to pulses, highlighting the pulse characteristics of measurement signals. This approach increases the accuracy of time-delay estimation for upstream and downstream signals, mitigating the issues caused by multi-peaks and fake peaks in the cross-correlation function. Compared to conventional CC, the DCC can eliminate the problem of multiple and fake peaks in cross-correlation functions more effectively, thereby increasing the reliability of velocity measurements.

A New Contactless Cross-Correlation Velocity Measurement System for Gas–Liquid Two-Phase Flow

Based on the principle of Contactless Conductivity Detection (CCD), a new contactless cross-correlation velocity measurement system with a three-electrode construction is developed in this work and applied to the contactless velocity measurement of gas–liquid two-phase flow in small channels. To achieve a compact design and to reduce the influence of the slug/bubble deformation and the relative position change on the velocity measurement, an electrode of the upstream sensor is reused as an electrode of the downstream sensor. Meanwhile, a switching unit is introduced to ensure the independence and consistency of the upstream sensor and the downstream sensor. To further improve the synchronization of the upstream sensor and the downstream sensor, fast switching and time compensation are also introduced. Finally, with the obtained upstream and downstream conductance signals, the velocity measurement is achieved by the principle of cross-correlation velocity measurement. To test the measurement performance of the developed system, experiments are carried out on a prototype with a small channel of 2.5 mm. The experimental results show that the compact design (three-electrode construction) is successful, and its measurement performance is satisfactory. The velocity range for the bubble flow is 0.312–0.816 m/s, and the maximum relative error of the flow rate measurement is 4.54%. The velocity range for the slug flow is 0.161 m/s–1.250 m/s, and the maximum relative error of the flow rate measurement is 3.70%.

New method for bubble/slug velocity measurement in small channels.

Based on the C4D technique and cross correlation velocity measurement technique, a new method for bubble/slug velocity measurement of the gas-liquid two-phase flow in small channels is proposed. A new C4D sensor, which is suitable for the parameter measurement of the gas-liquid two-phase flow in small channels, is developed by introducing the principle of capacitive reactance elimination. With two new C4D sensors, a bubble/slug velocity measurement system is developed, and the bubble/slug velocity is determined by the cross correlation velocity measurement technique. To verify the effectiveness of the proposed bubble/slug velocity measurement method, three prototypes of bubble/slug velocity measurement systems with different diameters (1.82 mm, 2.65 mm, and 2.96 mm, respectively) were established, and the bubble/slug measurement experiments were carried out. The research results show that the capacitive reactance elimination is an effective way to overcome the unfavorable influence of the coupled capacitances on measurement results. The experimental results indicate that the proposed method can successfully realize the bubble/slug velocity measurement in small channels, and the velocity measurement accuracy is satisfactory. For the three prototypes of the bubble/slug velocity measurement system, the maximum relative errors of the bubble/slug velocity measurement are all less than 5%.

A New Contactless Bubble/Slug Velocity Measurement Method of Gas–Liquid Two-Phase Flow in Small Channels

A new contactless bubble/slug velocity measurement method of the gas–liquid two-phase flow in small channels is proposed by extending the contactless conductivity detection technique to the contactless impedance detection (CID) technique. Two kinds of CID sensors with different constructions (tubular construction and radial construction) are developed to obtain the total impedance information (the real part, the imaginary part, and the amplitude) of the gas–liquid two-phase flow. Two bubble/slug velocity measurement systems with different constructions, the tubular three-electrode velocity measurement system and the radial four-electrode velocity measurement system, are developed. With the obtained total impedance information, three initial estimation values of the bubble/slug velocity are determined by the principle of the cross correlation velocity measurement. Then, with the real-time flow pattern identification result implemented by the fuzzy C-means, a corresponding velocity measurement model [which is the linear combination of the three initial estimation values of the bubble/slug velocity and is developed by the penalty function method and the Davidon–Fletcher–Powell algorithm] is applied to obtain the final bubble/slug velocity. Two groups of the bubble/slug velocity measurement system prototypes with three different inner diameters are developed. The bubble/slug velocity measurement experiments are carried out. The experimental results show that the proposed method is effective. For the two bubble/slug velocity measurement systems with different constructions, the maximum relative errors of the bubble/slug velocity measurement are all less than 4.5%. The research results also indicate that making full use of the total impedance information is an effective approach to improve the accuracy of the velocity measurement.

Measurement of Oil-Gas-Water Mixture Velocity Using a Conductance Cross-Correlation Flowmeter With Center Body in Small Pipe

To be able to acquire the mixture velocity of water continuous oil-gas-water three-phase flow in 20-mm inner diameter small pipe based on the cross-correlation method (CCM), accurate measurement of the cross-correlation velocity, and establishing valid relationship between cross-correlation velocity and mixture velocity is of importance. Due to the severe slippage effect and the non-uniform distribution of phases in three-phase flow, the correlation between the upstream and downstream signals is seriously affected, and the relationship between the cross-correlation velocity and the mixture velocity is extremely complicated. Moreover, the low-sampling frequency and noise also reduce the accuracy of cross-correlation velocity measurement. In this paper, a cross-correlation flowmeter (CCFM) with two ring-shape conductance sensors embedded on the center body is proposed. Based on the finite element method (FEM), the geometry of the CCFM is designed and optimized. A novel fast Fourier transform (FFT) interpolation algorithm is investigated to increase the sampling frequency while eliminating the noise. Afterward, the performances of the CCFM and the FFT interpolation algorithm combined with the CCM are experimentally evaluated. The results show that the CCFM can enhance the correlation of upstream and downstream signals while FFT interpolation algorithm can effectively increase the sampling frequency and eliminate the noise, which can improve the accuracy of cross-correlation velocity measurement. The CCFM also can simplify the relationship between the cross-correlation velocity and mixture velocity, and thus the mixture velocity can be satisfactorily predicted.

A New Contactless Method for Velocity Measurement of Bubble and Slug in Millimeter-Scale Pipelines

Combining C4D technique and cross-correlation velocity measurement technique, a new measurement method, which is suitable for the bubble/slug velocity measurement in millimeter-scale pipelines, is proposed. Based on the series resonance principle and the simulated inductor technique, a new C4D sensor is developed. With two conductance signals obtained by two new C4D sensors (the upstream sensor and the downstream sensor), the bubble/slug velocity measurement is implemented by the cross-correlation velocity measurement technique. Experiments are carried out in three pipelines with different inner diameters of 4.50, 5.46, and 6.44 mm, respectively. The experimental results show that the proposed bubble/slug velocity measurement method is effective, the development of the new C4D sensor is successful, and the velocity measurement accuracy is satisfactory. The relative error of bubble velocity measurement is less than 5.41% and the relative error of slug flow velocity measurement is less than 4.90%.

Cross-correlation velocity measurement of horizontal oil–water two-phase flow by using parallel–wire capacitance probe

Horizontal oil–water two-phase flow widely exists in petroleum industry. The flow measurement in oil well, which is one of key production logging technologies, is becoming more and more important for horizontal well production management. The complicated flow structures happened in horizontal oil–water two-phase flow bring a great challenge to flow measurement. We employ a parallel–wire capacitance probe (PWCP) to compose the cross-correlation velocity measurement. Firstly, we investigate the distribution of sensitivity field of PWCP by using finite element method (FEM). Then, we carry out the flow loop test to figure out the cross-correlation velocity from the voltage fluctuation signals measured from upstream and downstream probes. The results indicate that the cross-correlation characteristic of PWCPs depends on the oil–water flow structures. Finally, we use the kinematic wave model to predict the homogeneous velocity for six different horizontal oil–water two-phase flow patterns.

Measurement of bubble velocity using Capacitively Coupled Contactless Conductivity Detection (C4D) technique

The feasibility of applying Capacitively Coupled Contactless Conductivity Detection (C4D) technique to measurement of bubble velocity in gas–liquid two-phase flow in millimeter-scale pipe is investigated. And, a new method, which combines the C4D technique and the principle of cross-correlation velocity measurement, is proposed for the measurement of bubble velocity. This research includes two parts. First, based on the principle of C4D, a new five-electrode C4D sensor is developed. Then, with two conductivity signals obtained by the C4D sensor, the velocity measurement of bubble is implemented according to the principle of cross-correlation. The research results indicate that the C4D technique is highly effective and anticipates a broad potential in the field of two-phase flow. Experimental results show that the five-electrode C4D sensor is suitable for measuring the velocity of single bubbles with a relative error of less than 5%.

Fraction of Multiphase Flow Measurement System Design and Application

This paper introduced the application of pattern recognition in the measuring phase fraction of gas-powder mixed flow. Flow-through measurement system based on virtual instrument techniques; include the techniques of electrical capacitance tomography and cross-correlation velocity measurement technology. The module structure of the system is present. According the principle of the phase fraction based on pattern recognition technology, the arithmetic with C++ program is described in the paper. The experiment process for this flow-through measurement system and experiment results are described in this article.

Dense-phase pneumatically conveyed coal particle velocity measurement using electrostatic probes

The fundamental measurement theory of an electrostatic probe and cross-correlation velocity measurement method are introduced in this paper. The effects of the probe's geometric parameters, including the length of the probe; the thickness, length and relative permittivity of the dielectric pipe; the radius of the screen on the dimensionless calibration coefficient ( k), and the statistical error of the transit time ( τ m) of the correlation velocity measurement system using electrostatic probes were investigated theoretically. Finally the measurement system was applied in a 10 mm bore horizontal section of a dense-phase pneumatic conveying system under high pressure circulating pulverized coal over a superficial air velocity range of 0.5–7 m/s for a particle concentration 0.052–0.141 m 3/m 3. The experimental results that were obtained demonstrate that the system is capable of providing solid particle velocity measurements with repeatability better than 10% under the given experimental conditions.

Dense-phase pneumatically conveyed coal particle velocity measurement using electrostatic probes and cross correlation algorithm

The fundamental measurement theory of an electrostatic probe and cross-correlation velocity measurement method are introduced in the paper. The effects of the probe's geometric parameters including the length of the probe, the thickness, the length and the relative permittivity of the dielectric pipe, the radius of the screen on the dimensionless calibration coefficient (k) and the statistical error of the transit time (τm) of the correlation velocity measurement system using electrostatic probes were investigated theoretically. Finally the measurement system was applied in a 10 mm bore horizontal section of a dense phase pneumatic conveying system under high pressure circulating pulverized coal over a superficial air velocity range of 0.5-7 m/s for a particle concentration 0.052-0.141 m3/m3. Experimental results obtained demonstrate that the system is capable of providing solid particle velocity measurements with repeatability better than 10 % under the given experimental conditions.

A six-electrode local probe for measuring solids velocity and volumefraction profiles in solids-water flows

This paper describes the design and construction of a localsix-electrode conductivity probe which can be used in solids-water pipeflows to simultaneously measure the local solids volume fraction and thelocal solids axial velocity. Using finite element analysis, the probeelectrode geometry was designed so that the regions of the solids-watermixture that were interrogated by the probe were optimal for measurementof the volume fraction and for cross correlation velocity measurement. Theprobe was used, in conjunction with a computer controlled traversingmechanism, to obtain distributions of the local solids volume fraction andthe local solids axial velocity both in vertical upward and in upwardinclined solids-water flows. Such distributions can be used to validatevolume fraction and velocity profiles obtained using dual-plane electricalresistance tomography systems. Experimental results indicated that thesix-electrode probe can be used to estimate the local solids volumefraction in vertical upward solids-water flows with a mean absolute errorof approximately 0.01. Experimental results also indicated that thesix-electrode probe can be used to measure the local axial solids velocitywith a mean error of 2% of the reading.