Numerical Simulation of Particle Separation in An Oil-Sand Separator

The gathering systems of crude oil are greatly endangered by the fine sand and soil in oil. Up to now , how to separate sand from the viscid oil is still a technical problem for oil production home or abroad. Recently , Institute of Mechanics in Chinese Academy of Sciences has developed a new type of oil-sand separator , which has been applied successfully in oil field in situ. In this paper, the numerical method of vortex-stream function is used to predict the liquid-solid separating course and the efficiency for this oil-sand separator. Results show that the viscosity and particle diameter have much influence on the particle motion. The calculating separating efficiency is compared with that of experiment and indicates that this method can be used to model the complex two-phase flow in the separator.

Mechanics of a grip system of three-key-board hydraulic tongs developed for offshore oil pipe lines

This paper carries out the analysis of mechanics of a grip system of three-key-board hydraulic tongs developed for offshore oil pipe lines which has been successfully used in oil fields in China. The main improvement of this system is that a lever frame structure is used in the structural design, which reduces greatly the stresses of the major components of the oil pipe tongs. Theoretical analysis and numerical calculation based on thirteen basic equations developed Show that the teeth board of the tongs is not easy to slip as frequently happens to other systems and is of higher reliability.

Analysis of Temperature and Pressure Changes in Liquefied Natural Gas (LNG) Cryogenic Tanks

Liquefied natural gas (LNG) is being developed as a transportation fuel for heavy vehicles such as trucks and transit buses, to lessen the dependency on oil and to reduce greenhouse gas emissions. The LNG stations are properly designed to prevent the venting of natural gas (NG) from LNG tanks, which can cause evaporative greenhouse gas emissions and result in fluctuations of fuel flow and changes of fuel composition. Boil-off is caused by the heat added into the LNG fuel during the storage and fueling. Heat can leak into the LNG fuel through the shell of tank during the storage and through hoses and dispensers during the fueling. Gas from tanks onboard vehicles, when returned to LNG tanks, can add additional heat into the LNG fuel. A thermodynamic and heat transfer model has been developed to analyze different mechanisms of heat leak into the LNG fuel. The evolving of properties and compositions of LNG fuel inside LNG tanks is simulated. The effect of a number of buses fueled each day on the possible total fuel loss rate has been analyzed. It is found that by increasing the number of buses, fueled each day, the total fuel loss rate can be reduced significantly. It is proposed that an electric generator be used to consume the boil-off gas or a liquefier be used to re-liquefy the boiloff gas to reduce the tank pressure and eliminate fuel losses. These approaches can prevent boil-off of natural gas emissions, and reduce the costs of LNG as transportation fuel.

Oil-Water Two-Phase Flow Inside T-Junction

The oil/water two-phase flow inside T-junctions was numerically simulated with a 3-D two-fluid model, and the turbulence was described using the mixture k - epsilon model. Some experiments of oil/water flow inside a single T-junction were conducted in the laboratory. The results show that the separating performance of T-junction largely depends oil the inlet volumetric fraction and flow patterns. A reasonable agreement is reached between the numerical simulation and the experiments for both the oil fraction distribution and the separation efficiency.

Experimental Investigation On The Slip Between Oil And Water In Horizontal Pipes

This work is devoted to study of the slip phenomenon between phases in water-oil two-phase flow in horizontal pipes. The emphasis is placed on the effects of input fluids flow rates, pipe diameter and viscosities of oil phase on the slip. Experiments were conducted to measure the holdup in two horizontal pipes with 0.05 m diameter and 0.025 m diameter, respectively, using two different viscosities of white oil and tap water as liquid phases. Results showed that the ratios of in situ oil to water velocity at the pipe of small diameter are higher than those at the pipe of big diameter when having same input flow rates. At low input water flow rate, there is a large deviation on the holdup between two flow systems with different oil viscosities and the deviation becomes gradually smaller with further increased input water flow rate. (C) 2008 Elsevier Inc. All rights reserved.

Experimental Investigation On The Holdup Distribution Of Oil-Water Two-Phase Flow In Horizontal Parallel Tubes

An experimental investigation was conducted to study the holdup distribution of oil and water two-phase flow in two parallel tubes with unequal tube diameter. Tests were performed using white oil (of viscosity 52 mPa s and density 860 kg/m(3)) and tap water as liquid phases at room temperature and atmospheric outlet pressure. Measurements were taken of water flow rates from 0.5 to 12.5 m(3)/h and input oil volume fractions from 3 to 94 %. Results showed that there were different flow pattern maps between the run and bypass tubes when oil-water two-phase flow is found in the parallel tubes. At low input fluid flow rates, a large deviation could be found on the average oil holdup between the bypass and the run tubes. However, with increased input oil fraction at constant water flow rate, the holdup at the bypass tube became close to that at the run tube. Furthermore, experimental data showed that there was no significant variation in flow pattern and holdup between the run and main tubes. In order to calculate the holdup in the form of segregated flow, the drift flux model has been used here.

A coupled model for multiphase fluid flow and sedimentation deformation in oil reservoir and its numerical simulation

A mathematical model for coupled multiphase fluid flow and sedimentation deformation is developed based on fluid-solid interaction mechanism. A finite difference-finite element numerical approach is presented. The results of an example show that the fluid-solid coupled effect has great influence on multiphase fluid flow and reservoir recovery performances, and the coupled model has practical significance for oilfield development.

Distribution, stability, bifurcations and catastrophe of steady rotation of a symmetrical heavy gyroscope with viscous-liquid-filled cavity

The number, the angles of orientation and the stability in Rumyantsev Movchan's sense of oblique steady rotations of a symmetric heavy gyroscope with a cavity completely filled with a uniform viscous liquid, possessing a fixed point 0 on its symmetric axis. are given for various values of the parameters. By taking the square of the upright component of the angular momentum M2 as a control parameter, three types of bifurcation diagrams of the steady rotations, two types of jumps and two kinds of local catastrophes, one being the symmetric reduced cusp type and the other being of the symmetric reduced butterfly type, are obtained. By taking account of the M2-damping owing to the moment of unavoidable faint friction, two different modes for the gyroscope, initially in a stable quasi-steady upright rotation with a nutation angle theta(s) equal to zero, to topple over are found.

Study on the Performance of a Compact Compound Oil/Gas/Water Separator for Offshore Oil Industry

High-efficiency separation of the oil/gas/water mixtures is a significant issue in offshore oil industry. To reduce the total cost by means of reduction in weight and space compared with conventional separators, a novel compact compound oil/gas/water separator is developed. The research works on oil-gas-water separation by compound separating techniques is described in this paper. The innovative separator is a gravity settling tank with helical pipes within and T-shaped pipes outside. Both experiments and numerical simulations are presented to study the separating performance and efficiency of the helical pipes, which are the main part of the separator.

Effect of Pipe Diameter on Flow Pattern Transition in Vertical Oil Water Flows

This paper investiges the effect of pipe diameter on flow pattern transition boundary in oil water vertical flows, and proposes a model to determine the maximum inner diameter (D_{infty s}) of a pipe in which the slug flow would not occur When pipe inner diameter D>D_{infty s}, only bubble flow exists, while D

Multiphase Flow Measurement in the Offshore Oil Industry

In recent years, considerable research has been conducted into the development of a three-phase flowmeter suitable for use in an offshore environment, and oil/gas/water three-phase metering becomes an important aspect in multiphase flow measurement. This paper discusses the importance of three-phase flow measurement in offshore oil industry, describes the current development in this area, and points out the principal strategies which may be used to meter three-phase flow.

Numerical study on heavy rigid particle motion in a plane wake flow by spectral element method

Experimental particle dispersion patterns in a plane wake flow at a high Reynolds number have been predicted numerically by discrete vortex method (Phys. Fluids A 1992; 4:2244-2251; Int. J. Multiphase Flow 2000; 26:1583-1607). To address the particle motion at a moderate Reynolds number, spectral element method is employed to provide an instantaneous wake flow field for particle dynamics equations, which are solved to make a detail classification of the patterns in relation to the Stokes and Froude numbers. It is found that particle motion features only depend on the Stokes number at a high Froude number and depend on both numbers at a low Froude number. A ratio of the Stokes number to squared Froude number is introduced and threshold values of this parameter are evaluated that delineate the different regions of particle behavior. The parameter describes approximately the gravitational settling velocity divided by the characteristic velocity of wake flow. In order to present effects of particle density but preserve rigid sphere, hollow sphere particle dynamics in the plane wake flow is investigated. The evolution of hollow particle motion patterns for the increase of equivalent particle density corresponds to that of solid particle motion patterns for the decrease of particle size. Although the thresholds change a little, the parameter can still make a good qualitative classification of particle motion patterns as the inner diameter changes.

Large-eddy simulation of turbulent collision of heavy particles in isotropic turbulence

The small-scale motions relevant to the collision of heavy particles represent a general challenge to the conventional large-eddy simulation (LES) of turbulent particle-laden flows. As a first step toward addressing this challenge, we examine the capability of the LES method with an eddy viscosity subgrid scale (SGS) model to predict the collision-related statistics such as the particle radial distribution function at contact, the radial relative velocity at contact, and the collision rate for a wide range of particle Stokes numbers. Data from direct numerical simulation (DNS) are used as a benchmark to evaluate the LES using both a priori and a posteriori tests. It is shown that, without the SGS motions, LES cannot accurately predict the particle-pair statistics for heavy particles with small and intermediate Stokes numbers, and a large relative error in collision rate up to 60% may arise when the particle Stokes number is near St_K=0.5. The errors from the filtering operation and the SGS model are evaluated separately using the filtered-DNS (FDNS) and LES flow fields. The errors increase with the filter width and have nonmonotonic variations with the particle Stokes numbers. It is concluded that the error due to filtering dominates the overall error in LES for most particle Stokes numbers. It is found that the overall collision rate can be reasonably predicted by both FDNS and LES for St_K>3. Our analysis suggests that, for St_K<3, a particle SGS model must include the effects of SGS motions on the turbulent collision of heavy particles. The spectral analysis of the concentration fields of the particles with different Stokes numbers further demonstrates the important effects of the small-scale motions on the preferential concentration of the particles with small Stokes numbers.

Generating monoenergetic heavy-ion bunches with laser-induced electrostatic shocks

A method for efficient laser acceleration of heavy ions by electrostatic shock is investigated using particle-in-cell (PIC) simulation and analytical modeling. When a small number of heavy ions are mixed with light ions, the heavy ions can be accelerated to the same velocity as the light ions so that they gain much higher energy because of their large mass. Accordingly, a sandwich target design with a thin compound ion layer between two light-ion layers and a micro-structured target design are proposed for obtaining monoenergetic heavy-ion beams.