Search

Flow rate and holdup are two essential parameters to describe oil-water two-phase flow. The distribution of oil-water two-phase flow in the pipeline is very uneven, and there is a significant slippage between the phases. This makes it difficult to measure these two flow parameters. In this paper, a new measurement method of flow rate and holdup based on phase state regulation is proposed. The oil-water two-phase flow is adjusted to oil or water single-phase flow according to the time sequence by the phase state regulation, and the oil-water phase interface is measured with a conductance sensor. A wavelet transform based phase inflection point detection model is proposed to detect the oil-water phase change point. The experimental results show that the maximum measurement error of the flow rate of water is 3.73%, the maximum measurement error of the flow rate of oil is 3.68%, and the flow rate measurement repeatability is 0.0002. The accuracy of the measurement holdup is better than 3.23%, and the repeatability of the measurement holdup is 0.0003. The prototype designed based on this method has two advantages. One is that it is small in size, the other is that it does not depend on the accuracy of the sensor. Therefore, it can be widely used in oilfield ground measurement.

Velocity is an important parameter for fluid flow characteristics in profile logging. Particle tracking velocimetry (PTV) technology is often used to study the flow characteristics of oil wells with low flow velocity and high water cut, and the key to PTV technology is particle matching. The existing particle matching algorithms of PTV technology do not meet the matching demands of oil drops in the oil phase velocity measurement of oil-water two-phase flow with low velocity and high water cut. To raise the particle matching precision, we improved the particle matching algorithm from the oriented FAST and the rotated BRIEF (ORB) feature description and the random sample consensus (RANSAC) algorithm. The simulation and experiment were carried out. Simulation results show that the improved algorithm not only increases the number of matching points but also reduces the computation. The experiment shows that the improved algorithm in this paper not only reduces the computation of the feature description process, reaching half of the computation amount of the original algorithm, but also increases the number of matching results, thus improving the measurement accuracy of oil phase velocity. Compared with the SIFT algorithm and the ORB algorithm, the improved algorithm has the largest number of matching point pairs. And the variation coefficient of this algorithm is 0.039, which indicates that the algorithm is stable. The mean error of oil phase velocity measurement of the improved algorithm is 1.20 %, and the maximum error is 6.16 %, which is much lower than the maximum error of PTV, which is 25.89 %. The improved algorithm overcomes the high computation cost of the SIFT algorithm and achieves the precision of the SIFT algorithm. Therefore, this study contributes to the improvement of the measurement accuracy of oil phase velocity and provides reliable production logging data for oilfield.

There are many problems among contemporary college students, such as weak innovation consciousness, insufficient innovation motivation and poor ability of innovation achievements transformation. Through analyzing the relevant elements of innovation chain, ideas about the construction of collaborative innovation ecological environment is proposed for improving the teaching effect of innovation education for college students in this paper. The concrete measures and effects about the practical platform of university-enterprise collaborative innovation, the comprehensive and multi-dimensional innovation education system in universities, and the construction of first-class undergraduate courses in innovation education are introduced in detail. The practice shows that the construction of collaborative innovation ecological environment fundamentally solves the “bottleneck” problem of college students innovation, and provides inexhaustible power for the cultivation of college students innovation ability.

A flexible dual‐band efficient polarization converter is realized by both coupled mode theory (CMT) analysis and numerical simulation in the microwave regime. The proposed structure can convert linearly polarized electromagnetic waves into their orthogonal components in the two sidebands. Moreover, a specular reflection performance is obtained in the central frequency band. The polarization conversion ratio (PCR) and operating bandwidth of dual band is dynamically modulated by vanadium dioxide (VO2). In the simulation results, it is shown that the proposed metasurface can achieve linear polarization conversion in 8.17–12.87 and 14.63–18.92 GHz in the insulating phase. PCRs of the dual band are 97.06% and 98.13%, the corresponding relative bandwidths (RBs) are 44.68% and 25.58%. In the metallic phase, the PCRs in 6.81–13.95 and 16.23–18.16 GHz are 91.12% (RB = 68.79%) and 96.92% (RB = 11.22%). The analyses of the phase difference (u–v coordinate system) and the surface current are given to explain the mechanisms of dual‐band and high PCR. The simulation results are in good agreement with those of CMT. Furthermore, the structure has a robust response to the oblique incidence angle (up to 30°) and has polarization insensitivity. The proposed metasurface has great potential applications in antenna radiation, biosensing, and stealth technology. [ABSTRACT FROM AUTHOR]

The injection of CO2 to displace CH4 in coal seams is an effective method to exploit coalbed methane (CBM), for which the CO2 injection temperature and pressure are important influential factors. We performed simulations, using COMSOL Multiphysics to determine the effect of CO2 injection temperature and pressure on CO2-enhanced coalbed methane (CO2-ECBM) recovery, according to adsorption/desorption, seepage, and diffusion of binary gas (CO2 and CH4) in the coal seam, and deriver a thermal−hydraulic−mechanical coupling equation of CO2-ECBM. The simulation results show that, as CO2 injection pressure in CO2-ECBM increases, the molar concentration and displacement time of CH4 in the coal seam significantly decrease. With increasing injection temperature, the binary gas adsorption capacity in the coal seam decreases, and CO2 reserves and CH4 production decrease. High temperatures are therefore not conducive for CH4 production.

This paper introduces a double-walled hollow pipe (DWHP) that demonstrates good corrosion resistance and mechanical properties and that can be used in pipeline transportation and structural stress components in marine, freshwater, and corrosive environments. We designed and machined the specimens to meet the bending bearing capacity using a cross section method. We conducted low-cycle loading tests of the specimens to investigate the energy dissipation capacity of the DWHP, the effects of different geometrical parameters, and the concrete-filled strength of the DWHP on energy dissipation capacity. The results show that the failure forms of the specimens are similar. The geometrical characteristics of the specimens, the cohesive function between the concrete and the steel plate, and the strength of the concrete-filled pipe showed a significant influence on the mechanical properties of the specimens. Hysteretic curves are plump and possess a high capacity for energy dissipation. The energy dissipation capacity of the specimen decreases with an increase in the slenderness ratio. The slope of strength degradation decreases with any increase in the strength of the concrete-filled pipe. We optimized the section design of the component by improving the constraint effect coefficient, and we effectively improved its stability by adding stiffeners to the inner side of the outer wall of steel.

Leakage incidents on LNG bunker vessels will result in a serious degree of hazard. This paper investigates typical high-risk scenarios such as hose ruptures and valve joint leakages. The consequences of an LNG leakage accident during the simultaneous operation of a bunker vessel and a container carrier are simulated using the FLACS software, and the dispersion range of the combustible vapor cloud is quantitatively analyzed under both ballast and laden conditions. Under the ballast condition, the diffusion range of the combustible vapor cloud on the side of the bunker vessel is 58 × 15.5 m from the front wall of the cargo equipment room to the bow of the vessel, and 35 × 9.5 m between the cargo equipment room and the transom of the vessel. Under the laden condition, the diffusion range on the side of the bunker vessel is 58 × 15.5 m from the front wall of the cargo equipment room to the bow of the vessel, and 15 × 4 m between the rear end wall of the cargo equipment room and the front wall of the stern of the vessel. These results provide important technical guidance and reference values for the safe operation of LNG bunker vessels. [ABSTRACT FROM AUTHOR]

This paper studies the influence of small clamping eccentricity on the measurement and evaluation of involute profile, analyzes the cause of clamping eccentric error, establishes a clamping eccentric error compensation model, and introduces a computing method of clamping eccentric parameters. Experimental testing of the computing method of clamping eccentric parameters proves that the computing method of clamping eccentric parameters is correct and feasible when the clamping eccentric value is within three quarters of the measurement range of the probe. The results of the clamping eccentricity error compensation experiment show that the clamping eccentric error compensation model can compensate measurement results to the results attained under operating conditions, and achieve precision measurement of involute profiles. The highest allowed clamping eccentric value can be extended to three quarters of the measurement range of the probe by the clamping eccentricity error compensation model proposed in this paper, thereby saving time otherwise spent adjusting for clamping eccentricity. [ABSTRACT FROM AUTHOR]

A wideband low-scattering metasurface with optical transparency and flexibility is proposed by using the combination of phase cancellation and absorption mechanisms. Electromagnetic (EM) diffusion is achieved through the random phase distribution design of the two coding elements. The enhanced energy absorption can be obtained in a wide spectrum by using indium tin oxide (ITO) with suitable sheet resistance in the supercells. The experimental results show that the radar cross section (RCS) reductions of less than -10 dB under the planar and conformal cases are in 6.65-19.40 GHz and 6.11-17.37 GHz, corresponding relative bandwidth are 97.89% and 95.91%, respectively. Both theoretical analysis and simulated results are good accordance with the experiment. Furthermore, the analyses of the surface current, EM field distribution and power loss density are given to explain the hybrid RCS reduction mechanism. The proposed composite transparent flexible coding metasurface (CTFCM) maintains good angular stability within 0°-60° oblique incidence and has polarization insensitivity. The CTFCM has excellent flexibility and high optical transparency, which provides a way to reduce RCS in a wider band and has important application potential for stealth aircraft cockpit and transparent radome.