CN109060861A - The permanent magnet device and metering method of nuclear magnetic resonance fluid gauge - Google Patents
The permanent magnet device and metering method of nuclear magnetic resonance fluid gauge Download PDFInfo
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Abstract
The permanent magnet device and metering method of nuclear magnetic resonance fluid gauge provided by the invention, permanent magnet device include two sections of pre-polarizing magnets being sequentially coaxially arranged and one section of main magnet；The pre-polarizing magnet and main magnet are round tube shape structure, and the cavity at center is the channel of fluid flowing；Equivalent model on the pre-polarizing magnet and main magnet axial section is the extremely opposite magnet of the pole N and S；The pre-polarizing magnet can be rotated along its central axes.The permanent magnet device pre-polarizing magnet either identical or opposite situation of magnetic direction, can the fluid shorter to longitudinal relaxation time generate certain magnetization effect, this allow main magnet length do not have to it is too long.It only needs one layer of magnet structure that can realize the change of pre-polarizing magnet effective length, shortens the entire length of permanent magnet device, more compact structure is simple.
Description
Technical field
The invention belongs to nuclear magnetic resonance technique fields, and in particular to the permanent magnet device and meter of nuclear magnetic resonance fluid gauge
Amount method.
Background technique
In oil and natural gas production management process, contained oil, the ratio of gas and water in the fluid-mixing that oil/gas well is produced
It is often real-time change at any time with flow velocity, or even the indexs such as oil, the viscosity of gas, temperature, pressure can also change therewith.Often
The heterogeneous fluid gauge of the on-line checking of rule is the radiodensity method based on gamma ray, and different material pair is utilized in it
The difference of gamma ray absorbability, so as to extrapolate ratio shared by each phase fluid in fluid-mixing.However, gamma is flowed
Body gauge contains nuclear radioactive source, and there are the security risks of leakage.In addition gamma ray Fluid meter needs to mention before work
It is preceding that scale is carried out in the lab to sample, therefore the case where change in real time for oil and gas property, it can not make
Timely and effectively accurately identify.In order to replace conventional gamma ray Fluid meter, other have been proposed in the world at present
Heterogeneous fluid metered scheme, wherein most typically based on the heterogeneous fluid metering method of nuclear magnetic resonance physical principle.
But permanent magnet device length is longer in existing nuclear magnetic resonance fluid gauge, magnet dosage very significantly, cost
It is high.In addition, the structure of magnet is also more complicated, volume is bigger than normal, weight is overweight, is unfavorable for the operation and use of instrument.
Summary of the invention
For the defects in the prior art, the present invention provides the permanent magnet device of nuclear magnetic resonance fluid gauge, and structure is tight
It gathers simply, length is shorter.
Another object of the present invention is to provide the metering method of above-mentioned nuclear magnetic resonance fluid gauge.
In a first aspect, a kind of permanent magnet device of nuclear magnetic resonance fluid gauge, two sections including being sequentially coaxially arranged pre-
Polarized magnets and one section of main magnet；
Also containing measurement antenna in the main magnet；
The pre-polarizing magnet and main magnet are round tube shape structure, and the cavity at center is the channel of fluid flowing；It is described
Equivalent model on pre-polarizing magnet and main magnet axial section is the extremely opposite magnet of the pole N and S；The pre-polarizing magnet energy
It is enough to be rotated along its central axes.
Further, the pre-polarizing magnet and main magnet are all made of monopole cylinder Halbach permanent magnet array structure.
Further, two sections of pre-polarizing magnet shapes are identical；There is circle outside the pre-polarizing magnet and main magnet
Tubulose magnetic masking layer.
Second aspect, a kind of metering method of nuclear magnetic resonance fluid gauge, comprising the following steps:
The pre-polarizing magnet in above-mentioned permanent magnet device is rotated, so that the magnetic field that two pre-polarizing magnets and main magnet generate
Direction is identical；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is first
Magnetization vector；The fluid to be measured includes two kinds of ingredients: first composition and second composition；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the first nuclear magnetic signal；
The magnetic direction for keeping second segment pre-polarizing magnet and main magnet to generate is identical, rotates first segment pre-polarizing magnet,
So that the magnetic direction that two pre-polarizing magnets generate is opposite；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is second
Magnetization vector；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the second nuclear magnetic signal；
The ratio of two kinds of ingredients in fluid to be measured is calculated according to the first nuclear magnetic signal and the second nuclear magnetic signal.
Further, it is assumed that the ratio of first composition is λ in fluid to be measuredo, then in fluid to be measured second composition ratio
For λw=1- λo；
When the magnetic direction that two pre-polarizing magnets and main magnet generate is identical,
Fluid to be measured passes through the magnetization vector M that first segment pre-polarizing magnet generatesz(t1) are as follows:
Wherein, t1Time needed for passing through first segment pre-polarizing magnet for fluid to be measured,It relaxes for the longitudinal direction of second composition
The Henan time,For the longitudinal relaxation time of first composition,Magnetization for first composition in fluid to be measured in t moment is sweared
Amount,For second composition in fluid to be measured t moment magnetization vector；
For oil saturated magnetization vector,For the saturated magnetization vector of water；
Fluid to be measured passes through the magnetization vector M that second segment pre-polarizing magnet generatesz(t1+t2) are as follows:
Wherein, t2Pass through the time needed for second segment pre-polarizing magnet for fluid to be measured；
The magnetization vector that fluid to be measured generates when measuring antenna by main magnet, i.e. the first magnetization vector Mz(t1+t2+t3)
Are as follows:
Wherein, t3It is fluid to be measured from main magnet is entered to by the time needed for measuring antenna；
Y function is prepared by the following:
Construct following equation:
It willWith
It is brought into above-mentioned formula, common factor formula is extracted, just obtains y function.
Further, when the magnetic direction that two pre-polarizing magnets generate is opposite,
Fluid to be measured passes through the magnetization vector M that first segment pre-polarizing magnet generatesz(t1) are as follows:
Fluid to be measured passes through the magnetization vector M that second segment pre-polarizing magnet generatesz′(t1+t2) are as follows:
The magnetization vector that fluid to be measured generates when measuring antenna by main magnet, i.e. the second magnetization vector M 'z(t1+t2+t3)
Are as follows:
Wherein, y ' function is prepared by the following:
Construct following equation:
It willWith
Enter to above-mentioned formula, extracts common factor formula, just obtain y ' function.
Further, described that first composition and second in fluid to be measured is calculated according to the first nuclear magnetic signal and two nuclear magnetic signals
The ratio of ingredient specifically includes:
Construct following equation:
Wherein, S is the first nuclear magnetic signal, S/For the second nuclear magnetic signal.
The third aspect, a kind of metering method of nuclear magnetic resonance fluid gauge, comprising the following steps:
The pre-polarizing magnet in permanent magnet device described above is rotated, so that two pre-polarizing magnets and main magnet generated
Magnetic direction is identical；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is first
Magnetization vector；The fluid to be measured includes three kinds of ingredients；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the first nuclear magnetic signal；
The magnetic direction for keeping second segment pre-polarizing magnet and main magnet to generate is identical, rotates first segment pre-polarizing magnet,
So that the magnetic direction that two pre-polarizing magnets generate is opposite；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is second
Magnetization vector；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the second nuclear magnetic signal；
The magnetic direction for keeping first segment pre-polarizing magnet and main magnet to generate is identical, rotates second segment pre-polarizing magnet,
So that the magnetic direction that magnetic direction and main magnet that second segment pre-polarizing magnet generates generate is opposite；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is third
Magnetization vector；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as third nuclear magnetic signal；
The ratio of three kinds of ingredients in fluid to be measured is calculated according to the first nuclear magnetic signal, the second nuclear magnetic signal and third nuclear magnetic signal
Example.
As shown from the above technical solution, permanent magnet device provided by the invention, pre-polarizing magnet either magnetic direction phase
With or opposite situation, can the fluid shorter to longitudinal relaxation time generate certain magnetization effect, this makes main magnet
Length can not have to too long.It only needs one layer of magnet structure that can realize the change of pre-polarizing magnet effective length, shortens forever
The entire length of magnet apparatus, more compact structure are simple.
Metering method provided by the invention, according to the nuclear magnetic signal difference under the conditions of different pre-polarizing, so that it may calculate
Ratio shared by each ingredient in fluid-mixing.
Detailed description of the invention
It, below will be to specific in order to illustrate more clearly of the specific embodiment of the invention or technical solution in the prior art
Embodiment or attached drawing needed to be used in the description of the prior art are briefly described.In all the appended drawings, similar element
Or part is generally identified by similar appended drawing reference.In attached drawing, each element or part might not be drawn according to actual ratio.
Fig. 1 is the structural schematic diagram for the permanent magnet device that embodiment one provides.
Fig. 2 is the method flow diagram that embodiment two provides.
Fig. 3 rotates the structural schematic diagram of pre-polarizing magnet in the case of being embodiment two provide two kinds.Wherein (a) is pre- pole
Change the permanent magnet device that magnet generates direction same magnetic field；(b) the permanent magnet dress in contrary magnetic field is generated for pre-polarizing magnet
It sets；
In the case of Fig. 4 is two kinds that embodiment two provides, the static magnetic field strength that pre-polarizing magnet generates in the cavities, horizontal seat
Mark is distance, and ordinate is magnetic induction intensity.Wherein (a) is the static magnetic field strength that pre-polarizing magnet generates direction same magnetic field；
(b) static magnetic field strength in contrary magnetic field is generated for pre-polarizing magnet；
The magnetization vector of oil and water changes in the case of Fig. 5 is embodiment two provide two kinds.Wherein (a) is pre-polarizing magnet
Generate the magnetization vector variation of direction same magnetic field；(b) the magnetization vector variation in contrary magnetic field is generated for pre-polarizing magnet；
Fig. 6 is the method flow diagram that example IV provides.
Specific embodiment
It is described in detail below in conjunction with embodiment of the attached drawing to technical solution of the present invention.Following embodiment is only used for
Clearly illustrate technical solution of the present invention, therefore be only used as example, and cannot be used as a limitation and limit protection model of the invention
It encloses.It should be noted that unless otherwise indicated, technical term or scientific term used in this application are should be belonging to the present invention
The ordinary meaning that field technical staff is understood.
Spin is the intrinsic attribute of microcosmic particle, and the particle being not zero that spins is in external magnetic field B0Magnetization under can generate
Net magnetic moment, the magnetic moment do Larmor precession along outer magnetic field direction.When apply one with outer magnetic field direction orthogonal and frequency and magnetic moment
The consistent pulse radiation frequency field B of Larmor precession frequency1When, a large amount of spin particle will transit to high level from low-lying level, hair
Raw RESONANCE ABSORPTION, this is just referred to as nmr phenomena.After removing radiofrequency field, the spin particle in high level can discharge again
Energy comes back to lower state, this evolutionary process is known as relaxation process.Currently, being most widely used and mature pulse nuclear-magnetism
What resonance technique detected is exactly the NMR relaxation process of various substances.NMR relaxation process is divided into two kinds again: a kind of
It is longitudinal relaxation process, what it was indicated is the process that substance is magnetized in external magnetic field, and token state is longitudinal relaxation time T1；Separately
One is transverse relaxation processes, and what it was indicated is evolutionary process of the magnetization vector under spin particle interaction, and token state is
Lateral relaxation time T2。
Embodiment one:
A kind of permanent magnet device of nuclear magnetic resonance fluid gauge, referring to Fig. 1, including two sections of pre- poles being sequentially coaxially arranged
Change magnet 1 and one section of main magnet 3；
Also containing measurement antenna 5 in the main magnet, the loop construction of the measurement antenna 5 is solenoid shape；
Specifically, measurement antenna is used to detect the nuclear magnetic signal of fluid.
The pre-polarizing magnet 1 and main magnet 3 are round tube shape structure, and the cavity at center is the channel 2 of fluid flowing；Institute
Stating the equivalent model on 3 axial section of pre-polarizing magnet 1 and main magnet is the extremely opposite magnet of the pole N and S；The pre-polarizing magnetic
Body 1 can be rotated along its central axes.
Specifically, pre-polarizing magnet magnetizes fluid, and fluid develops by longitudinal relaxation rule generates a magnetization arrow
M is measured, which will be detected in main magnet, and size is proportional to nuclear magnetic signal intensity.Pre-polarizing magnet can be along it
Central axes rotation, changes the magnetic direction of pre-polarizing magnet.
The identical or opposite situation of pre-polarizing magnet either magnetic direction in permanent magnet device, when can be to longitudinal relaxation
Between shorter fluid generate certain magnetization effect, it is too long that this does not have to the length of main magnet.Only need one layer of magnet
Structure can realize the change of pre-polarizing magnet effective length, shorten the entire length of permanent magnet device, more compact structure letter
It is single.
Further, the pre-polarizing magnet 1 and main magnet 3 are all made of monopole cylinder Halbach permanent magnet array structure.
Specifically, the Halbach permanent magnet array structure includes a series of magnetic patch arranged by the specific direction of magnetization
And magnetic patch is fixed required without magnetic metallic framework.Monopole cylinder Halbach array can produce in the channel that fluid flows
Raw homogeneous static magnetic field, halbach array are the key that generate uniform magnetic field.
Further, two sections of pre-polarizing magnets, 1 shape is identical；Have outside the pre-polarizing magnet 1 and main magnet 3
Circular tube shaped magnetic masking layer 4.
Specifically, magnetic masking layer is the substance of high magnetic permeability, such as soft iron.Magnetic masking layer can both block magnetostatic field to outside
The interference of equipment, and the effect of internal shimming can be played.Embodiment two:
Embodiment two propose using above-mentioned nuclear magnetic resonance fluid gauge to tool there are two types of ingredient fluid to be measured carry out
The method of test.
A kind of metering method of nuclear magnetic resonance fluid gauge, referring to fig. 2, comprising the following steps:
S1: referring to Fig. 3 (a), rotating the pre-polarizing magnet in above-mentioned permanent magnet device, so that two pre-polarizing magnets and master
The magnetic direction that magnet generates is identical；
S2: flowing through pre-polarizing magnet and main magnet for fluid to be measured, is defined through the magnetization vector that magnetic field magnetization generates and is
First magnetization vector；The fluid to be measured includes two kinds of ingredients: first composition and second composition；
S3: main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the first nuclear magnetic signal；
Specifically, fluid to be measured can be the fluid comprising the biggish two kinds of ingredients of longitudinal relaxation time difference.Such as it wraps
The fluid of two kinds of ingredients of oil-containing and water.Oil and water are all rich in hydrogen atom, and hydrogen nuclei is 1/2 particle and most common of spinning
Nuclear magnetic resonance research object.Hydrogen atom in two kinds of substances has due to the difference of locating molecular structure and chemical environment
The longitudinal relaxation time of notable difference.Wherein, the typical T of underground mineralized water1Value typically about 1~2s, and the typical T of moveable oil1
Value is typically about 100~300ms.
When the direction of magnetization of two sections of pre-polarizing magnets is identical, fluid will be polarized at this time along the identical direction of magnetization always
Pre-polarizing magnet is in fully effective situation, and oil and water are magnetized simultaneously, the nuclear magnetic signal finally measured be comprising oil with
The mixed signal of water, it depends not only on the ratio of oil and water, additionally depends on the degree that You Heshui is magnetized.Wherein pre-polarizing magnetic
The static magnetic field strength that body generates in the cavities is referring to fig. 4 (a)；The magnetization vector generating process of oil and water is referring to Fig. 5 (a)
S4: referring to Fig. 3 (b), the magnetic direction for keeping second segment pre-polarizing magnet and main magnet to generate is identical, rotation first
Section pre-polarizing magnet, so that the magnetic direction that two pre-polarizing magnets generate is opposite；
S5: flowing through pre-polarizing magnet and main magnet for fluid to be measured, is defined through the magnetization vector that magnetic field magnetization generates and is
Second magnetization vector；
S6: main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the second nuclear magnetic signal；Wherein pre-polarizing
The static magnetic field strength that magnet generates in the cavities is referring to fig. 4 (b).The magnetization vector generating process of oil and water is referring to Fig. 5 (b)
Specifically, when the direction of magnetization of two sections of pre-polarizing magnets is opposite, fluid first polarizes along a direction of magnetization, then
It is polarized again along the opposite direction of magnetization.When the direction of magnetization is opposite, oil also can be by a small amount of magnetized, and water can only be by very little
Magnetization, the nuclear magnetic signal of water are smaller.
S7: the ratio of two kinds of ingredients in fluid to be measured is calculated according to the first nuclear magnetic signal and the second nuclear magnetic signal.
This method is according to the nuclear magnetic signal difference under the conditions of different pre-polarizing, so that it may calculate oil and water in fluid-mixing
Shared ratio.Embodiment three:
Embodiment three on the basis of example 2, increases the following contents:
For being rich in the substance of protium, along magnetostatic field B0The magnetization vector M in directionzEvolutionary process strictly meet cloth
The conspicuous equation in Lip river:
Mz(t)=Mz(0)e-t/T+M0(1-e-t/T)；
Wherein, Mz(0) magnetization vector of zero moment, M are indicated0Indicate saturated magnetization vector, T is the longitudinal relaxation of the substance
Time.
Assuming that volume shared by fluid to be measured is 1, it is assumed that the ratio of first composition is λ in fluid to be measuredo, then in fluid to be measured
The ratio of second composition is λw=1- λo；
1, when the magnetic direction that two pre-polarizing magnets and main magnet generate is identical,
Fluid to be measured passes through the magnetization vector M that first segment pre-polarizing magnet generatesz(t1) are as follows:
Wherein, t1Time needed for passing through first segment pre-polarizing magnet for fluid to be measured,It relaxes for the longitudinal direction of second composition
The Henan time,For the longitudinal relaxation time of first composition,Magnetization for first composition in fluid to be measured in t moment is sweared
Amount,For second composition in fluid to be measured t moment magnetization vector；
For oil saturated magnetization vector,For the saturated magnetization vector of water.
Fluid to be measured passes through the magnetization vector M that second segment pre-polarizing magnet generatesz(t1+t2) are as follows:
Wherein, t2Pass through the time needed for second segment pre-polarizing magnet for fluid to be measured；
The magnetization vector that fluid to be measured generates when measuring antenna by main magnet, i.e. the first magnetization vector Mz(t1+t2+t3)
Are as follows:
Wherein, t3It is fluid to be measured from main magnet is entered to by the time needed for measuring antenna；
Y function is prepared by the following:
Construct following equation:
It willWithBand
Enter to above-mentioned formula, extracts common factor formula, just obtain y function.
2, when the magnetic direction that two pre-polarizing magnets generate is opposite,
Fluid to be measured passes through the magnetization vector M that first segment pre-polarizing magnet generatesz(t1) are as follows:
Fluid to be measured passes through the magnetization vector M that second segment pre-polarizing magnet generatesz′(t1+t2) are as follows:
The magnetization vector that fluid to be measured generates when measuring antenna by main magnet, i.e. the second magnetization vector M 'z(t1+t2+t3)
Are as follows:
Wherein, y ' function is prepared by the following:
Construct following equation:
It willWithEnter
To above-mentioned formula, common factor formula is extracted, y ' function is just obtained.
Specifically, when the direction of magnetization is opposite, referring to Fig. 5 (b), magnetization vector first increases from zero in one direction, then again
Increase in reverse direction.Due to the longitudinal relaxation time of oilTime is short,Close to zero,Close to list
Position 1.And the longitudinal relaxation time of waterTime is long,Close to 1,Then close to zero.This shows pre-
Polarized magnets greatly reduce the magnetization of water when the direction of magnetization is opposite, but still make with certain magnetization to oil
With this undoubtedly increases the comparison of grease signal, while can also further shorten the length of main magnet, saves more bodies
Product, weight, cost.
Further, described that first composition and second in fluid to be measured is calculated according to the first nuclear magnetic signal and two nuclear magnetic signals
The ratio of ingredient specifically includes:
Construct following equation:
Wherein, S is the first nuclear magnetic signal, S/For the second nuclear magnetic signal.
Specifically, Mz、M′zIt is all deterministic expression, so f is also a determining function expression.In this way, two
Under kind pre-polarizing magnet operating mode, oil-water ratio is brought into equation group, magnetization vector is proportional to nuclear magnetic signal intensity.Cause
This, the signal measured under both of which, which is divided by, can obtain one containing only a unknown number λoEquation, solve it and just obtain
Each phase fluid accounting of fluid-mixing.
Method provided by the embodiment of the present invention, to briefly describe, embodiment part does not refer to place, can refer to aforementioned side
Corresponding contents in method embodiment.
Example IV:
Example IV provides the method using fluid of the above-mentioned nuclear magnetic resonance fluid gauge detection comprising three kinds of ingredients.
A kind of metering method of nuclear magnetic resonance fluid gauge, referring to Fig. 6, comprising the following steps:
S11: rotating the pre-polarizing magnet in permanent magnet device described above, so that two pre-polarizing magnets and main magnet produce
Raw magnetic direction is identical；
S12: flowing through pre-polarizing magnet and main magnet for fluid to be measured, is defined through the magnetization vector that magnetic field magnetization generates and is
First magnetization vector；The fluid to be measured includes three kinds of ingredients；
S13: main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the first nuclear magnetic signal；
S14: the magnetic direction for keeping second segment pre-polarizing magnet and main magnet to generate is identical, rotates first segment pre-polarizing magnetic
Body, so that the magnetic direction that two pre-polarizing magnets generate is opposite；
S15: flowing through pre-polarizing magnet and main magnet for fluid to be measured, is defined through the magnetization vector that magnetic field magnetization generates and is
Second magnetization vector；
S16: main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the second nuclear magnetic signal；
S17: the magnetic direction for keeping first segment pre-polarizing magnet and main magnet to generate is identical, rotates second segment pre-polarizing magnetic
Body, so that the magnetic direction that magnetic direction and main magnet that second segment pre-polarizing magnet generates generate is opposite；
S18: flowing through pre-polarizing magnet and main magnet for fluid to be measured, is defined through the magnetization vector that magnetic field magnetization generates and is
Third magnetization vector；
S19: main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as third nuclear magnetic signal；
S20: three kinds of ingredients in fluid to be measured are calculated according to the first nuclear magnetic signal, the second nuclear magnetic signal and third nuclear magnetic signal
Ratio.
Specifically, when measurement includes the fluid to be measured of three kinds of ingredients, the direction of premagnetization magnet is rotated, 3 kinds of magnetic are formed
When change process, the component ratio of the fluid to be measured just can be tested out.
Method provided by the embodiment of the present invention, to briefly describe, embodiment part does not refer to place, can refer to aforementioned side
Corresponding contents in method embodiment.
Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention., rather than its limitations；To the greatest extent
Pipe present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that: its according to
So be possible to modify the technical solutions described in the foregoing embodiments, or to some or all of the technical features into
Row equivalent replacement；And these are modified or replaceed, various embodiments of the present invention technology that it does not separate the essence of the corresponding technical solution
The range of scheme should all cover within the scope of the claims and the description of the invention.
Claims (8)
1. a kind of permanent magnet device of nuclear magnetic resonance fluid gauge, which is characterized in that two sections including being sequentially coaxially arranged pre-
Polarized magnets and one section of main magnet；
Also containing measurement antenna in the main magnet；
The pre-polarizing magnet and main magnet are round tube shape structure, and the cavity at center is the channel of fluid flowing；The pre- pole
The equivalent model changed on magnet and main magnet axial section is the extremely opposite magnet of the pole N and S；The pre-polarizing magnet being capable of edge
Its central axes rotation.
2. the permanent magnet device of nuclear magnetic resonance fluid gauge according to claim 1, which is characterized in that
The pre-polarizing magnet and main magnet are all made of monopole cylinder Halbach permanent magnet array structure.
3. the permanent magnet device of nuclear magnetic resonance fluid gauge according to claim 1, which is characterized in that
Two sections of pre-polarizing magnet shapes are identical；There is circular tube shaped magnetic masking layer outside the pre-polarizing magnet and main magnet.
4. a kind of metering method of nuclear magnetic resonance fluid gauge, which comprises the following steps:
The pre-polarizing magnet in permanent magnet device described in claim 1 is rotated, so that two pre-polarizing magnets and main magnet generate
Magnetic direction it is identical；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is the first magnetization
Vector；The fluid to be measured includes two kinds of ingredients: first composition and second composition；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the first nuclear magnetic signal；
The magnetic direction for keeping second segment pre-polarizing magnet and main magnet to generate is identical, rotates first segment pre-polarizing magnet, so that
The magnetic direction that two pre-polarizing magnets generate is opposite；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is the second magnetization
Vector；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the second nuclear magnetic signal；
The ratio of two kinds of ingredients in fluid to be measured is calculated according to the first nuclear magnetic signal and the second nuclear magnetic signal.
5. the metering method of nuclear magnetic resonance fluid gauge according to claim 4, which is characterized in that
Assuming that the ratio of first composition is λ in fluid to be measuredo, then the ratio of second composition is λ in fluid to be measuredw=1- λo；
When the magnetic direction that two pre-polarizing magnets and main magnet generate is identical,
Fluid to be measured passes through the magnetization vector M that first segment pre-polarizing magnet generatesz(t1) are as follows:
Wherein, t1Pass through time needed for first segment pre-polarizing magnet, T for fluid to be measured1 wFor second composition longitudinal relaxation when
Between, T1 oFor the longitudinal relaxation time of first composition,For first composition in fluid to be measured t moment magnetization vector,For second composition in fluid to be measured t moment magnetization vector； For oil
Saturated magnetization vector,For the saturated magnetization vector of water；
Fluid to be measured passes through the magnetization vector M that second segment pre-polarizing magnet generatesz(t1+t2) are as follows:
Wherein, t2Pass through the time needed for second segment pre-polarizing magnet for fluid to be measured；
The magnetization vector that fluid to be measured generates when measuring antenna by main magnet, i.e. the first magnetization vector Mz(t1+t2+t3) are as follows:
Wherein, t3It is fluid to be measured from main magnet is entered to by the time needed for measuring antenna；
Y function is prepared by the following:
Construct following equation:
It willWithBand
Enter to above-mentioned formula, extracts common factor formula, just obtain y function.
6. the metering method of nuclear magnetic resonance fluid gauge according to claim 5, which is characterized in that
When the magnetic direction that two pre-polarizing magnets generate is opposite,
Fluid to be measured passes through the magnetization vector M that first segment pre-polarizing magnet generatesz(t1) are as follows:
Fluid to be measured passes through the magnetization vector M that second segment pre-polarizing magnet generatesz′(t1+t2) are as follows:
The magnetization vector that fluid to be measured generates when measuring antenna by main magnet, i.e. the second magnetization vector M 'z(t1+t2+t3) are as follows:
Wherein, y ' function is prepared by the following:
Construct following equation:
It willWithEnter
To above-mentioned formula, common factor formula is extracted, y ' function is just obtained.
7. the metering method of nuclear magnetic resonance fluid gauge according to claim 6, which is characterized in that
It is described to calculate the ratio of first composition and second composition tool in fluid to be measured according to the first nuclear magnetic signal and two nuclear magnetic signals
Body includes:
Construct following equation:
Wherein, S is the first nuclear magnetic signal, S/For the second nuclear magnetic signal.
8. a kind of metering method of nuclear magnetic resonance fluid gauge, which comprises the following steps:
The pre-polarizing magnet in permanent magnet device described in claim 1 is rotated, so that two pre-polarizing magnets and main magnet generate
Magnetic direction it is identical；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is the first magnetization
Vector；The fluid to be measured includes three kinds of ingredients；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the first nuclear magnetic signal；
The magnetic direction for keeping second segment pre-polarizing magnet and main magnet to generate is identical, rotates first segment pre-polarizing magnet, so that
The magnetic direction that two pre-polarizing magnets generate is opposite；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, being defined through the magnetization vector that magnetic field magnetization generates is the second magnetization
Vector；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as the second nuclear magnetic signal；
The magnetic direction for keeping first segment pre-polarizing magnet and main magnet to generate is identical, rotates second segment pre-polarizing magnet, so that
The magnetic direction that the magnetic direction and main magnet that second segment pre-polarizing magnet generates generate is opposite；
Fluid to be measured is flowed through into pre-polarizing magnet and main magnet, is defined through the magnetization vector that magnetic field magnetization generates as third magnetization
Vector；
Main magnet measures the nuclear magnetic signal of antenna detection fluid to be measured, is defined as third nuclear magnetic signal；
The ratio of three kinds of ingredients in fluid to be measured is calculated according to the first nuclear magnetic signal, the second nuclear magnetic signal and third nuclear magnetic signal.
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