气井涡流排水采气新技术及其应用

涡流排水采气技术是一项由中国石油天然气集团公司于2011年率先引进的排水采气新技术，既可应用于气井井下，也可应用于地面集输系统。为此，在论述了气井井下涡流排水采气的工艺原理、技术优点，工具组成、下入操作程序的基础上，总结了该技术在松辽盆地、鄂尔多斯盆地所取得的主要成果、经验与认识，并进一步提出了深入进行科研、试验与攻关的可行性建议。结论认为：应在总结升1-1、苏36-4-3等井试验经验的基础上，针对我国有水气田开发的实际情况，加强涡流排水采气工艺的适应性、影响因素及关键技术的研究，並从选井原则的合理确定、优化设计与座封方式、优化组合等方面入手，学习国外成功经验，进一步加快该项工艺技术在我国的推广应用步伐。     

A second-order algorithm for curve orthogonal projection onto parametric surface

Repeated use of point projection to find the projection of a curve on a surface is rather inefficient as the iteration procedures in point projection is typically slow. A novel curve projection scheme is proposed for computing the orthogonal projection of a progenitor curve onto a parametric surface. Under this scheme, the projection curve is parameterized using the parameter of the progenitor curve. Differential geometric characteristics of the projection curve are analysed. A marching method with error adjustment is used to calculate the projection curve. Several examples are presented and comparisons are made to demonstrate the effectiveness of the proposed scheme.     

A robust weakly compressible SPH method and its comparison with an incompressible SPH

This paper presents a comparative study for the weakly compressible (WCSPH) and incompressible (ISPH) smoothed particle hydrodynamics methods by providing numerical solutions for fluid flows over an airfoil and a square obstacle. Improved WCSPH and ISPH techniques are used to solve these two bluff body flow problems. It is shown that both approaches can handle complex geometries using the multiple boundary tangents (MBT) method, and eliminate particle clustering‐induced instabilities with the implementation of a particle fracture repair procedure as well as the corrected SPH discretization scheme. WCSPH and ISPH simulation results are compared and validated with those of a finite element method (FEM). The quantitative comparisons of WCSPH, ISPH and FEM results in terms of Strouhal number for the square obstacle test case, and the pressure envelope, surface traction forces, and velocity gradients on the airfoil boundaries as well as the lift and drag values for the airfoil geometry indicate that the WCSPH method with the suggested implementation produces numerical results as accurate and reliable as those of the ISPH and FEM methods. Copyright © 2011 John Wiley & Sons, Ltd.     

Steady and transient inflow dynamics with actuator disk vortex theory

The actuator disk is a well‐known and widely used theoretical tool in wind engineering. This work proposes a new theory based on an actuator surface, capable of treating time‐varying vectorial load distributions and yaw/pitch misalignment. A simplified representation of vortex motion is used to arrive at a tractable problem. The theory is not restricted to disks; arbitrary coplanar (optionally disjoint) actuator surfaces may be modeled. Some of the theoretical novelties used in the modeling includes use of the fractional Laplacian and extensive use of the Fourier transform on . Promising experimental validation based on pitch‐step experiments at the Tjæreborg turbine is furnished. Comparisons are also made to existing methodologies. Analysis and numerical work shows that the model encapsulates Coleman's vortex theory.     

Numerical study on erosion of a pipe bend with a vortex chamber

Abrasive erosion at bend is a common issue in gas–solid pneumatic system. Vortex chamber design is one of the specialized designs that offers promising prospect at reducing erosion. The performance of design is still relatively unknown in the literature. The aim of this work is to study the effect of basic erosion variables such as the flow Reynolds number, the particle Stokes number, and the vortex chamber size. The results show that the vortex chamber always reduces the erosion in comparison to the common radius bend, and it is more effective at higher Reynolds number. Increasing the chamber size reduces the erosion but the most significant reduction happens when the chamber size to the pipe diameter ratio is increased from 1 to 1.25. The chamber size influences the erosion differently at different Reynolds number. Trends describing these effects were obtained through trial-and-error approach. The particle Stokes number has nonunique effect on erosion. Increasing Stokes number through increasing Re increases the erosion while increasing Stokes number through decreasing Re_p decreases the erosion.     

Effect of permanent magnet stirring on internal quality of steel

Permanent magnet stirring (PMS) featuring low power dissipation and high-intensity magnetic field was investigated as a means of decreasing internal solidification defects. In this study, the magnetic Taylor number (Ta) was used to quantify the melt ?ow. Initial research of PMS involved a laboratory study of the solidification of Sn–20 wt-% Pb alloy. An industrial plant trial with continuously cast tire cord steel confirmed that PMS, in accord with the laboratory findings, produced an improvement in central cavities in the cast product. Moreover, it was established that PMS is an alternative method for reducing carbon macrosegregation in tire cord steel billets with different section sizes. It was also found that PMS (Ta?=?8.97?×?10⁷) was more effective for improving central carbon macrosegregation of tire cord steel than electromagnetic stirring (Ta?=?6.33?×?10⁷) due to the larger Ta related to the driven-flow intensity of the residual melt.     

Numerical modeling of hydrogen catalytic reactions over a circular bluff body

This paper was intended to delineate numerical research for hydrogen catalytic combustion over a circular cylinder. The wire/rod-type catalytic reactor is a simple geometry reactor with an economical design with less pressure loss. For the single rod in the reaction channel, the flow characteristic and the difference of conversion efficiency between non-gas-phase reaction and gas-phase reaction have been delineated in the present study. The flow field and the chemical reactions were numerically modeled using 2D Large Eddy Simulation combined with the gas-phase and surface reaction mechanisms. The results show that the current numerical simulation has been validated to precisely predict the vortex shedding and its frequency in the cold flows. Despite the variation trends being dominated by the upstream flow, the vortex shedding phenomena were affected by the flue gas generated from the rod surface. It can be seen from the linear relationship between the vortex shedding frequency of reacting flow and Reynolds Number. It is noted that the vortex shedding vanished if the gas-phase reaction was ignited in the reaction channel. In addition, the geometric modified conversion efficiency was proposed to delineate an indicator that could be potential for the optimization of rod-type catalytic reactor. In summary, the fundamental study of a rod in a 2D flow channel can provide information for optimizing the catalytic design or the rod array arrangement in the reactor. Moreover, the rod can also be a partial catalytic flame holder to ignite and stabilize the gas-phase reaction. The obtained results could be the potential for practical applications of rod-type catalytic combustion, catalytic gas turbine, hydrogen generation, partially catalytic reaction flame holder, and other catalytic reactions that can be appreciated.     

Renewable energy harvesting from water flow

The hydrokinetic energy of flowing water is plentiful, environment-friendly, renewable and can be harvested. This paper reports a new energy harvesting system using vortex-induced vibration (VIV). The proposed convertor harvests vibrations of a bluff body resulting from interaction of the alternating vortices created by the unsteady separation. These vortices are shed from the sides of the bluff body and form a pattern in the wake known as the von Kármán vortex street. The vortices create unsteady loading and induce vibrations with a predictable frequency and amplitude. Assisted by the bluff body with specific geometry and piezoelectric generators, the kinetic energy of the water flow can be converted into mechanical vibrations and electrical energy. In order to maximise the output energy of the harvester, the natural frequency of the mechanical system needs to lock into the frequency of the VIVs. Thus, the geometry of the bluff body has to be optimised to match the natural frequency of the convertor. This study examines the conceptual design of the physical model. The fluid–structure interaction model is applied to study the preliminary design. The maximum energy density that can be extracted by the proposed convertor from the water flow with velocities from 0.2 to 1 m/s is also estimated.Abbreviations: 1.CFD Computational Fluid Dynamics; 2.DC Direct Current (electricity); 3.FIM Fluid Induced Motion; 4.ODE Ordinary Differential Equation; 5.PTC Passive Turbulence Control; 6.VIV Vortex Induced Vibration; 7.VIVACE Vortex Induced Vibration Aquatic Clean Energy; 8.2D Two Dimensional     

Noise reduction of ultrasonic Doppler velocimetry in liquid metal experiments with high magnetic fields

The last decades have seen a number of liquid metal experiments on the interaction of magnetic fields with the flow of electrically conducting fluids. The opaqueness of liquid metals requires non-optical methods for inferring the velocity structure of the flow. Quite often, such experiments are carried out in the presence of high electrical currents to generate the necessary magnetic fields. Depending on the specific purpose, these currents can reach several kiloamperes. The utilized switching mode power supply can then influence seriously the measurement system by electromagnetic interference. A recent experiment on the azimuthal magnetorotational instability (AMRI) has shown that a hydrodynamically stable Taylor–Couette flow becomes unstable under the influence of a high azimuthal magnetic field. An electrical current along the axis of the experiment with up to 20 kA generates the necessary field to destabilize the flow. We present experimental results of this AMRI experiment carried out at the PROMISE facility with an enhanced power supply. For this setup, we discuss the elaborate measures that were needed to obtain a reasonable signal-to-noise ratio of the ultrasonic Doppler velocimetry (UDV) system. In dependence on various parameter variations, some typical features of the observed instability, such as the energy content, the wavelength, and the frequency are analyzed and compared with theoretical predictions.