WO2015020550A1

WO2015020550A1 - Arrangement and method for multiphase flow measurements

Info

Publication number: WO2015020550A1
Application number: PCT/RU2013/000678
Authority: WO
Inventors: Viktor Serafimovich Aksenov; Alexandra Igorevna BOTYACHKOVA; Gennadiy Gennadievich KARPINSKIY; Stepan Alexandrovich Polikhov
Original assignee: Siemens Aktiengesellschaft
Priority date: 2013-08-06
Filing date: 2013-08-06
Publication date: 2015-02-12

Abstract

The present invention relates to an arrangement for multiphase flow measurements comprising at least one radiation source (1), at least one radiation detector (5) and at least one conduit (4) to be passed by a fluid. The conduit (4) is located to be transmitted by radiation (2) from the source (1) detected by the detector (5) with a body (3) arranged in the conduit (4) to be passed and/or flowed round by the fluid. The present invention further relates to a method to measure the flow of a fluid, particularly with the described arrangement. At a body (3) arranged in the fluid flow fluctuations of pressure and/or density and/or phase are produced and the fluctuations are measured. FIG.1

Description

Arrangement and method for multiphase flow measurements The present invention relates to an arrangement for

multiphase flow measurements comprising at least one

radiation source, at least one radiation detector and at least one conduit to be passed by a fluid. The conduit is located to be transmitted by radiation from the source detected by the detector. The present invention further relates to a method to measure the flow of a fluid,

particularly with the described arrangement.

For velocity and composition measurements of fluids there are different techniques known from the state of the art, see for example WO 2011/119045. Usually they require a combination of different approaches for velocity measurements, e.g. Venturi tube, cross-correlation methods, and for composition

measurements e.g. capacitance, resistivity, x-ray and gamma- ray absorption.

Fluids in the further described context are inter alia liquids or gases like oil and gas from mining, or liquids from food production and other industrial processes . These liquids comprise normally different components and/or phases. In gas for example small droplets of liquid can be used to monitor the velocity of the fluid flow. Also fluctuations of density without phase changes in the fluid can be used.

Cross-correlation methods of velocity measurement are based on the detection of the flow of inhomogeneities at different moments of time and at different locations. Bubbles, slugs, solid particles and others are used as inhomogeneities for velocity measurements. The interpretation of cross- correlation based measurements are easier to perform and more reliable than results obtained from differential pressure measurements like Ventury and V-cone.

Multiphase flow composition and component velocities of fluids can be measured inline with a multiphase flow meter device. A flow measurement and visualization is for example performed by means of x-rays and/or gamma-rays, but other kinds of radiation are also used. Cross-correlation based measurements usually do not require Equation of State (EOS) for multiphase mixtures. The need of EOS for differential pressure measurements of multiphase flow velocity is a limiting factor for multiphase flow meters accuracy and reliability. However, the variety of multiphase flows and regimes not always provide significant flow inhomogeneities to implement cross-correlation methods in practice .

Multiphase flow measurements are known from the state of the art, for example from WO 2011/005133A1 and WO 2011/119045. In the state of the art the fact, that the absorption

coefficient for X-rays strongly depends on the material and photon energy is used for measurements. In WO 2011/005133A1 one or several x-ray tubes and a two-dimensional array of detector elements or a set of detector elements arranged over a two-dimensional area, so called matrix detector, are used for multiphase flow measurements. The matrix detector receives photons attenuated by a multiphase flow. Flow velocity calculation is based on the analysis of consequent flow images. In WO 2011/119045 two sources and two matrix detectors are used for multiphase flow velocity measurements in tomography mode.

The known multiphase flow metering approaches utilize usually 2D and 3D image processing for flow velocity calculation in a wide range of gas volume fraction, including wet gas

conditions. But often multiphase flows with high gas volume fractions are homogeneous and liquid droplets are too small to be detected by x-ray flat panel detectors. Due to this fact the velocity calculation utilized in methods according to WO 2011/005133A1 and WO 2011/119045 are difficult to perform and can lead to inaccurateness . The object of the present invention is to overcome the problems described above. Especially an object of the present invention is to enable or improve the flow measurements of fluids. Particularly an object is to give an accurate and reliable method to determine the velocity for multiphase fluid flows for example for fluids like wet gases with high volume fraction of gas.

The above objects are achieved by the arrangement for multiphase flow measurements according to claim 1 and the method to measure the flow of a fluid, particularly with the before described arrangement, according to claim 6.

An arrangement according to the present invention for multiphase flow measurements comprises at least one radiation source, at least one radiation detector and at least one conduit to be passed by a fluid. The conduit is located to be transmitted by radiation from the source detected by the detector. A body is arranged in the conduit to be passed and/or flowed round by the fluid.

The arrangement allows reliable velocity detection of fluid flow and cross-correlation based velocity measurements of multiphase flows with low inhomogeneities, especially for wet gas flows, particularly with a gas volume fraction greater than 90 %. The body arranged inside the fluid flow leads to a concentration and increase of fluctuations in the fluid, which can be measured and increases the visibility and detectability. The measurable velocity of fluctuations is correlated to the velocity of the fluid and the fluid velocity can be derived from the measurement of velocity of fluctuations. The arrangement allows the correct

determination of a fluid velocity, particularly of a

multiphase fluid.

The body can be a bluff body, particularly at a position in the conduit to produce fluctuations of pressure and/or density and/or phase within the fluid stream. A bluff body effectively increases the amount of fluctuations within a flowing fluid.

The body can have the form of a polyhedron, particularly a cuboid or a prism with trapezoid base. These shapes of a body are well able to produce adequate fluctuations within a fluid stream to be measured.

The at least one conduit can be a pipe shaped conduit for the fluid to flow within the pipe, particularly with the body positioned in the conduit in a multiphase flow of fluid upstream the body. This arrangement is easy to use and effective to measure fluctuations within the fluid produced by the body. The body can be arranged in the middle of the stream to produce on all sides nearly the same fluctuations or it can be positioned near the walls of the conduit, for easy fixation. The conduit can be a hollow cylinder with fluid flowing within the hollow cylinder. It can be formed for example with a round, elliptical or rectangular shape of the base area. Other shapes are suitable too, depending on the fluid flow and body shape.

The at least one radiation source can be an x-ray and/or a gamma-ray and/or a Thz radiation source. These rays are able to pass through the liquid and particularly the walls of the conduit, being able to detect fluctuations within a fluid by the changes of absorption. The arrangement can comprise one or more corresponding detectors designed to detect the radiation of the radiation source, particularly with a 2D matrix radiation detector. The fluctuations can be made visible within space with this arrangement and the fluid flow can be measured reliable.

A Method according to the present invention to measure the flow of a fluid, particularly with an arrangement as

described before, comprises the measurement of the radiation of a source by a detector, in which the radiation detected passed through the flowing fluid at least partly. At a body arranged in the fluid flow fluctuations of pressure and/or density and/or phase are produced and the fluctuations are measured.

The fluid can be a liquid and/or a gas, particularly a multiphase fluid from the production of oil, gas, food or from mining. It can be a multiphase fluid with high gas volume fraction (GVF) , particularly comprising small

droplets. The droplets can be produced in the fluid due to the fluctuations caused by the body. With standard methods known from the state of the art it is not possible to reliable measure the fluid flow of these multiphase fluids. With the help of the body placed within the fluid and introduced fluctuations due to the body within the fluid, these fluctuations can be measured and detected, and the velocity of phases of the fluid can be determined.

The body placed in the fluid flow can cause droplets to be formed and/or increased in size within the fluid. The velocity of droplets in the fluid can be measured by the radiation and/or the velocity of the fluid flow can be determined by the droplet velocity, particularly by the droplet mean velocity.

Upstream the body a Carmen vortex street can be generated by the body and fluctuations and/or droplets can be measured in the region of Carmen vortex street.

The measurement can be performed with a multiphase flow meter, comprising the radiation source and detector. One or more 2D detectors can be used to detect and determine the fluctuations in the fluid in space. The method can comprise a transmission radiation technique. Fluctuations are well detectable in transmission mode, if fluctuations are big enough. The method can be based on a flow visualization method.

The advantages in connection with the described method to measure the flow of a fluid according to the present

invention are similar to the previously, in connection with the arrangement for multiphase flow measurements described advantages .

The present invention is further described hereinafter with reference to illustrated embodiments shown in the

accompanying drawings, in which:

FIG. 1 illustrates an arrangement for multiphase flow

measurements according to the present invention with a body 3 placed in a fluid flow in top view, and

FIG. 2 illustrates the arrangement of FIG. 1 in side view, and

FIG. 3 illustrates the arrangement of FIG. 1 in front view with traces of liquid droplets 7 in the fluid flow 6. FIG. 1 shows the arrangement for fluid flow measurements according to the present invention. The arrangement comprises a radiation source 1 and a radiation detector 5 for inter alia rays 2 like x-ray, gamma-ray and/or a Thz radiation. The radiation passes through a conduit 4. Within the conduit 4 a fluid is flowing and passing alongside a body 3. As shown in Fig. 1 the conduit can have the form of a cylindrical pipe. Other forms like cubic or rectangular chambers can be used too. The body 3 produces and/or increases fluctuations within the fluid. The fluctuations are measured with radiation from the source 1. The detector 5 in Fig. 1 is a 2D matrix detector. Other kinds of detectors and/or more than one detector can be used to view the fluctuations in space.

Fluids flowing through the conduit are liquids and/or gas. For example the flow of a multiphase fluid with high gas volume fraction (GVF) can be visualized with the arrangement according to the present invention. The fluctuations can have the form of droplets, which are introduced and/or increased in size by the fluid flowing along the surface of body 3. The velocity of droplets is measured and used to determine the fluid flow of the multiphase fluid. For some fluids the velocity of the fluid is for example the same as the droplet velocity.

FIG. 2 shows the arrangement for fluid flow measurements of FIG. 1 in side view. Arrows represent the direction of fluid flowing through the conduit 4, passing by the body 3. For simplicity means for fixing the body for example at the wall of the conduit 4 are not shown in the FIG. It can be fixed inter alia direct at the wall of conduit , or indirectly by for example a rack fixed to the wall .

In FIG. for simplicity only a part of conduit 4 is shown, denoted by curled lines. It can be part of a pipe system. The fluid enters the measuring part shown in FIG. 2 flowing in direction 6 to the body 3 , for example as shown with the body 3 upstream in the fluid flow. The fluid passes by and flows along the body surface. The body 3 alters the fluid flow and introduces density and pressure variations and/or

oscillations within the fluid. High density gradients and liquid droplets for example within GVF gas improve the visualization by higher contrasts in transmission radiation measurements. The fluid exits the measuring region as shown in FIG. 2 in direction 6'. The region next to the body 3, in the direction of fluid flow behind the body, is the region for radiation measurements .

Fluctuations and/or droplets exhibit in radiation

transmission measurements different absorption coefficients compared with other parts of the fluid and are visualized by the change in transmitted radiation intensity and/or spectra. They are detectable and visualized with radiation from the source 1 passing through the fluid and measured with detector 5. With a 2D matrix detector 5 or detectors 5 at different positions the spatial behavior, arrangement and velocity of fluctuations within the fluid can be measured. For measurements various arrangements with different positions of sources 1 and detectors 5 can be used, not shown in FIG. for simplicity. The FIG. show just an embodiment out of different possibilities .

In FIG. 3 the arrangement for multiphase flow measurements of FIG. 1 and 2 is shown in front view. In this embodiment the body 3 has the form of a trapezoid. A GVF gas or other fluid in upstream direction 6, indicated by dotted lines passes the body 3. The body 3 is within the fluid stream and affects the multiphase flow, creating density and pressure oscillations in the flow upstream the bluff body 3. A Carman vortex street 7 occurs. Oscillations of pressure upstream the bluff body 3 causes a concentration of liquid droplets. Concentrated droplets are transported with the gas flow and droplet velocity, particularly mean droplet velocity is measured to determine the flow velocity of the gas. It is measured in transmission mode by radiation from the source 1 detected by the detector 5.

Without a bluff body particularly in GVF gas droplets are too small to be detected. The body 3 introduces and/or increases the fluctuations, particularly liquid droplet concentration and/or size in the fluid. Increased fluctuations are easier to visualize or enable visualization with transmission radiation techniques. The mean droplet velocity is determined with this method and is a measure for the flow of multiphase fluids . The described embodiments can be combined with each other or used in combination with embodiments known from the state of the art. Different materials and forms of the body 3 can be used, depending on the chemical composition of multiphase fluid and velocity of fluid flow. For example the body 3 can be made of metal like steel or cupper, or out of plastic. The form can be trapezoidal to introduce density and pressure oscillations in form of a Carman vortex street. Other forms, particularly with special surface structures can be used to affect the fluid fluctuations. The use of different radiation detectors spatial distributed around the conduit 4 enable a 3D visualization of fluid flow. Measurements with radiation of different wavelength or spectra can give information about the fluid composition.

Fluctuations in the fluid flow introduced by the body 3 produce measurable pressure and/or density and/or phase changes within the fluid stream. These fluid fluctuations enable reliable and easy the velocity determination of the multiphase fluid flow with transmission radiation techniques, particularly for GVF gases. The method can also be used inter alia in food industry, oil and gas industry and applications, where a reliable multiphase fluid flow measurement is needed.

List of Reference Characters

1 radiation source

2 radiation

3 body

4 conduit

5 radiation detector

6, 6' direction of fluid flow

7 droplets in the Carmen vortex street

Claims

Arrangement for multiphase flow measurements comprising at least one radiation source (1) , at least one radiation detector (5) and at least one conduit (4) to be passed by a fluid, where the conduit (4) is located to be transmitted by radiation (2) from the source (1) detected by the detector (5) ,

characterized in that a body (3) is arranged in the conduit (4) to be passed and/or flowed round by the fluid.

Arrangement according to claim 1, characterized in that the body (3) is a bluff body, particularly at a position in the conduit (4) to produce fluctuations of pressure and/or density and/or phase within the fluid stream.

Arrangement according to any one of claims 1 or 2, characterized in that the body (3) has the form of a polyhedron, particularly a cuboid or a prism with trapezoid base.

Arrangement according to any one of claims 1 to 3, characterized in that the at least one conduit (4) is a pipe shaped conduit for the fluid to flow within the pipe, particularly with the body (3) positioned in the conduit (4) in a multiphase flow of fluid upstream the body (3) .

Arrangement according to any one of claims 1 to 4 , characterized in that the at least one radiation source (1) is a x-ray and/or a gamma-ray and/or a Thz

radiation source, and/or the arrangement comprises one or more corresponding detectors (5) designed to detect the radiation (2) of the radiation source (1),

particularly with a 2D matrix radiation detector. Method to measure the flow of a fluid, particularly with an arrangement according to any one of claims 1 to 5, comprising the measurement of the radiation (2) of a source (1) by a detector (5) , in which the radiation (2) passes through the flowing fluid, characterized in that at a body (3) arranged in the fluid flow

fluctuations of pressure and/or density and/or phase are produced and the fluctuations are measured.

Method according to claim 6, characterized in that the fluid is a liquid and/or a gas, particularly a

multiphase fluid from the production of oil, gas, food or from mining, and/or a multiphase fluid with high gas volume fraction (GVF) , particularly comprising small droplets .

Method according to any one of claims 6 or 7,

characterized in that droplets (7) are produced in the fluid due to the fluctuations caused by the body (3) .

Method according to claim 8, characterized in that the velocity of the droplets (7) in the fluid is measured by the radiation (2) and/or the velocity of the fluid flow is determined by the droplet velocity,

particularly by the droplet mean velocity. Method according to any one of claims 6 to 9,

characterized in that upstream the body (3) a Carmen vortex street is generated by the body (3) and

fluctuations and/or droplets (7) are measured in the region of Carmen vortex street. Method according to any one of claims 6 to 10, characterized in that the measurement is performed with a multiphase flow meter, comprising the radiation source (1) and detector (5) , and/or is based on a flow visualization method.

12. Method according to any one of claims 6 to 11, comprising a transmission radiation technique.