阅读说明：本技术 一种差压式流量计的压差自适应计量段 (Differential pressure self-adaptation measurement section of differential pressure type flowmeter ) 是由 张家铭 张天宏 孙汝辉 黄向华 盛汉霖 *** 于 2020-07-02 设计创作，主要内容包括：本发明提出的是一种差压式流量计的压差自适应计量段,包括壳体、引导装置、纺锤形节流体、高压测量口、低压测量口和弹性装置；其中壳体整体呈圆管形,纺锤形节流体置于壳体内部,并与壳体同轴安装,弹性装置安装于纺锤形节流体的尾部,引导装置一体化集成于壳体的内表面,高压测量口和低压测量口分别设于壳体外表面相对纺锤形节流体的前部与中部位置。本发明利用沿程压损与流道长度成反比、节流件压差与流量成正相关的关系,使压差-流量关系曲线满足数学上凸或线性的函数关系,满足小流量时压差较大,大流量时压差较小,且保证压差-流量满足一一映射,可实现低压损,量程比大,精度高的流量计量。(The invention provides a differential pressure self-adaptive metering section of a differential pressure type flowmeter, which comprises a shell, a guide device, a spindle-shaped throttling body, a high-pressure measuring port, a low-pressure measuring port and an elastic device, wherein the shell is provided with a guide hole; the whole shell is in a circular tube shape, the spindle-shaped throttling body is arranged in the shell and is coaxially installed with the shell, the elastic device is installed at the tail part of the spindle-shaped throttling body, the guiding device is integrated on the inner surface of the shell, and the high-pressure measuring port and the low-pressure measuring port are respectively arranged on the outer surface of the shell and are opposite to the front part and the middle part of the spindle-shaped throttling body. The invention utilizes the relationship that the on-way pressure loss is in inverse proportion to the length of the flow channel and the differential pressure of the throttling element is in positive correlation with the flow, so that a differential pressure-flow relation curve meets the mathematical convex or linear function relationship, the requirements of large differential pressure at small flow and small differential pressure at large flow are met, the differential pressure-flow meets the one-to-one mapping, and the flow measurement with low pressure loss, large range ratio and high precision can be realized.)

1. A differential pressure self-adaptive metering section of a differential pressure type flowmeter is characterized by comprising a shell (1), a guide device (2), a fusiform throttling body (3), a high-pressure measuring port (4), a low-pressure measuring port (5) and an elastic device (6); the whole shell (1) is in a circular tube shape, the spindle-shaped throttling body (3) is arranged inside the shell (1) and is coaxially mounted with the shell (2), the elastic device (6) is mounted at the tail part of the spindle-shaped throttling body (3), the guide device (2) is integrated on the inner surface of the shell (1), and the high-pressure measuring port (4) and the low-pressure measuring port (5) are respectively arranged at the front part and the middle part of the outer surface of the shell (1) relative to the spindle-shaped throttling body (3).

2. The differential pressure adaptive metering section of the differential pressure flowmeter according to claim 1, characterized in that flanges are arranged at both ends of the casing (1).

3. The differential pressure adaptive metering section of the differential pressure flowmeter according to claim 1, characterized in that the guide device (2) is a pin guide device or a guide rail guide device, so that the spindle-shaped throttle body can move only along the axial direction and is limited in circumferential rotation and radial movement; when the pin type guide device is adopted, the guide device (2) and the inner surface of the shell (1) are integrated at 180 degrees, a movable groove is formed in the 180-degree corresponding position of the side surface of the fusiform throttle body (3), and the pin type guide device and the movable groove are in clearance fit to realize the functions; when the three-jaw chuck type guide rail is adopted, the guide device (2) adopts the three-jaw chuck type guide rail to be integrated with the inner surface of the shell (1) at 120 degrees, and the outer surface of the spindle-shaped throttling body (3) is directly in clearance fit with the guide rail to realize the functions.

4. The differential pressure self-adaptive metering section of the differential pressure type flowmeter according to claim 1, characterized in that the spindle-shaped throttle body (3) and the shell (1) form an annular flow passage, the metered fluid forms a pressure drop in the annular flow passage, and the metering of the fluid flow is realized by utilizing the function relation of the pressure drop and the flow; the front section of the outer surface of the spindle-shaped throttle body (3) adopts a smooth curved surface which can be guided by the second order mathematically, the middle section of the outer surface adopts a straight line section, and the rear section of the outer surface adopts a smooth curved surface which can be guided by the second order mathematically.

5. The differential pressure adaptive metering section of the differential pressure flowmeter according to claim 1, wherein the elastic device (6) is a mechanical spring, a hydraulic spring or a gas spring, and the compression length of the elastic device is proportional to the pressure.

6. The differential pressure adaptive metering section of the differential pressure flowmeter according to claim 1, wherein the specific adjusting process of the elastic device (6) for adaptively adjusting the differential pressure between the high pressure measuring port (4) and the low pressure measuring port (5) is as follows:

1) when the flow is small, the fluid friction force and the fluid pressure on the surface of the spindle-shaped throttle body (3) are small, and the front-back pressure difference of the spindle-shaped throttle body (3) is small, so that the area integral of the stress on the surface of the spindle-shaped throttle body (3) is small, and the contraction length of the elastic device (6) is small due to stress balance, so that the length of an annular flow passage formed by the shell (1) and the straight line section of the spindle-shaped throttle body (3) between the high-pressure measuring port (4) and the low-pressure measuring port (5) is long, and the pressure loss generated by the fluid flowing through the annular flow passage is in direct proportion to the length of the annular flow passage, so that the pressure difference measured between the high-pressure measuring port (4) and the low-pressure measuring port (5) is large, and;

2) when the flow begins to increase, the fluid friction force and the fluid pressure on the surface of the spindle-shaped throttling body (3) are increased, and the front-back pressure difference of the spindle-shaped throttling body (3) is increased, so the surface integral of the stress on the surface of the spindle-shaped throttling body (3) is increased, and the contraction length of the elastic device (6) is increased due to the stress balance, so that the length of an annular flow passage formed by the shell (1) and the straight line section of the spindle-shaped throttling body (3) between the high-pressure measuring port (4) and the low-pressure measuring port (5) is reduced, and the pressure loss generated by the fluid flowing through the annular flow passage is in direct proportion to the length of the annular flow passage, so that the pressure difference measured between the high-pressure measuring port (4) and the low-pressure measuring port (5) is reduced according to a certain proportion, but.

7. The differential pressure adaptive metering section of the differential pressure type flowmeter according to any one of claims 1 to 6, characterized in that the metering section measures the differential pressure between the high pressure measuring port (4) and the low pressure measuring port (5) through a differential pressure sensor and converts the differential pressure into the flow rate metered by the metering section according to the following formula:

wherein pi is the circumference ratio, D is the shell inner diameter which is the difference between the shell inner diameter and the diameter of the middle section of the spindle-shaped throttle body, mu is the viscosity coefficient of the fluid to be measured, delta p is the pressure difference measured between the pressure difference measuring ports, l' is the length of the residual annular flow passage between the pressure difference measuring ports when the elastic device is compressed to the limit, S is the section area of the middle section of the spindle-shaped throttle body, l₁Is the length of the middle section of the spindle-shaped throttle body, k is the stiffness coefficient of the elastic device, q is the measured fluid flow_maxThe maximum flow of fluid or the maximum flow for a given flow in an actual project is measured for the designed flowmeter.

8. The differential pressure adaptive metering section of the differential pressure flowmeter according to claim 7, wherein according to the differential pressure-flow formula (1), when the flow is given and the differential pressure has the maximum value limit, the differential pressure-flow adaptive relationship or the linear differential pressure-flow adaptive relationship satisfying the quadratic curve is realized by adjusting the geometric parameters corresponding to the positions of the shell (1), the spindle-shaped throttle body (3), the high-pressure measuring port (4) and the low-pressure measuring port (5) and by adjusting the stiffness coefficient of the elastic device (6): the pressure difference changes violently when the flow is small, and the pressure difference measurement precision and the fluid metering precision when the flow is small are improved; when the linear pressure difference-flow self-adaptive relation is met, the pressure difference changes uniformly in the full-flow range, and the flow metering requirement in the full-flow range is met.

Technical Field

The invention relates to a differential pressure self-adaptive metering section of a differential pressure type flowmeter, belonging to the technical field of flow measuring equipment.

Background

The flowmeter is one of important instruments in industrial measurement, is widely applied to various fields of chemical industry, petroleum, nuclear energy, metallurgy, electric power, electronics, traffic, light textile, food and the like, is an important tool for developing industrial and agricultural production, saving energy, improving product quality and improving economic benefit and management level, and plays an important role in national economy. To accommodate various applications, various types of flow meters have been developed in succession.

The flow meters are mainly classified into differential pressure flow meters, rotor flow meters, turbine flow meters, volumetric flow meters, electromagnetic flow meters, ultrasonic flow meters, and the like according to the measurement principle. The differential pressure flowmeter obtains the real-time flow of the measured fluid through the relation of differential pressure and flow based on the differential pressure before and after the measurement section, and is developed from the theoretical basis of the differential pressure flowmeter established in Torricelli in the 17 th century, and is one of the flowmeter types with the longest application history, the mature practical experience and the perfect standard specification; meanwhile, the differential pressure flowmeter has the advantages of good real-time performance, wide measurement range, simple measurement principle and the like. However, since the accuracy of the existing differential pressure transmitter is defined based on the full measurement range, the accuracy in the low differential pressure range is lower than the accuracy in the high differential pressure range; meanwhile, in some specific occasions, such as the control problem of an electric fuel pump of an aeroengine, the maximum value of the fluid flow is given, the maximum value of the allowed pressure difference is also strictly limited, a large pressure difference is needed at the time of small flow, high-precision flow measurement is realized at the time of small flow, and the precision can be relatively low at the time of large flow. The existing differential pressure type flowmeter structure lacks self-adaptive function, can not correspondingly adjust the measurement precision according to the differential pressure change, and brings great difficulty to data collection and measurement.

In the prior published patent technical scheme, the utility model with publication number CN210069116U provides a satisfy the big-traffic throttling arrangement of the big-traffic of high pressure differential little flow and low pressure differential, and the device has solved the above-mentioned problem that current differential pressure flowmeter exists to a certain extent. However, the device adopts a design scheme that a plurality of small holes are formed in the sleeve, the small flow channels and the large flow channels are alternately arranged, the position of the valve core needs to be manually adjusted according to the flow, and only the functions of high differential pressure small flow and low differential pressure large flow are respectively realized, but the automatic adaptive adjustment function cannot be realized. The invention patent application with publication number CN110662946A discloses a flow rate measuring device and a flow rate measuring method, which propose a pressure difference-flow rate relation formula that also conforms to a mathematical quadratic curve, but do not propose a structure of a measuring device or a related description that can realize a high pressure difference small flow rate and a low pressure difference large flow rate. Each patent or patent application with publication numbers CN209783664U, CN109489741A, CN106441468A and CN106248159A respectively discloses some high-precision flow metering devices and methods based on the relation of pressure difference and flow, but the adopted flow metering devices all utilize orifice plates or venturi flow meters to realize accurate metering of flow, and do not provide a throttling device with self-adaptive function and capable of meeting the requirements of high-pressure-difference small flow and low-pressure-difference large flow. The invention patent with publication number CN106525173A discloses a measuring device with seamless switching of measuring ranges, which adopts a method that a bent pipe is used for throttling, a single chip microcomputer is used for automatically judging the differential pressure of a plurality of measuring holes, and the seamless switching cannot be realized because the differential pressure of the plurality of measuring holes is not automatically adjusted by a throttling device. The utility model patent with publication number CN2736741 and the invention patent application with publication number CN107806912A both disclose devices that use a spindle throttle to realize accurate measurement of flow, but none of the above two patents uses an elastic device to make the measuring device adaptive-adjust according to pressure difference, so as to realize measurement of high-pressure-difference small flow and low-pressure-difference large flow, and it is difficult to apply the situation of accurate measurement of full-flow range flow when the maximum value of flow and the maximum value of pressure difference have strict limitations. A flow metering scheme is researched for an Electric Fuel pump of an aircraft Engine by Noriko Morioka schooler and other scholars of IHI company in Japan in 2014, the flow metering scheme aims to achieve the aim of accurately metering the full-flow range flow when the maximum flow value and the maximum pressure difference value are strictly limited, and the metering method adopts the pressure difference-flow relation to meter the flow and needs to meet the metering of high-pressure-difference small flow and low-pressure-difference large flow. However, the adopted scheme is to measure the flow from two flow passages, a pore plate is adopted for throttling when the flow is small, a special valve which is automatically opened when the flow is large is adopted for throttling when the flow is large, and the throttling device is not integrated.

Disclosure of Invention

The invention aims to overcome the defects of the existing differential pressure flowmeter structure and provides a differential pressure self-adaptive metering section of the differential pressure flowmeter, which realizes the self-adaptive regulation of differential pressure-flow by utilizing three proportional relations, namely that the length of an elastic device is inversely proportional to the front-back differential pressure of a throttling element, the on-way pressure loss of the throttling section is inversely proportional to the length of a flow passage and the front-back differential pressure of the throttling element is proportional to the flow, can be applied to the flow metering occasions with given maximum value of flow and strictly limited maximum value of differential pressure, ensures the metering of small flow with high differential pressure and large flow with low differential pressure, and ensures the high-precision flow metering in the.

The technical solution of the invention is as follows: a differential pressure self-adaptive metering section of a differential pressure type flowmeter is characterized by comprising a shell, a guide device, a spindle-shaped throttling body, a high-pressure measuring port, a low-pressure measuring port and an elastic device; the shell is a main flow channel for metering fluid, is integrally in a circular tube shape, and is provided with flanges at two ends for being installed on various occasions needing to meter flow; the spindle-shaped throttle body is arranged in the shell and is coaxially arranged with the shell, the elastic device is arranged at the tail part of the spindle-shaped throttle body, elastic equipment with the compression length being in direct proportion to the pressure is adopted, such as a mechanical spring, a hydraulic spring or a gas spring, and the like, and is used for adaptively adjusting the pressure difference between the high-pressure measuring port and the low-pressure measuring port, the guide device adopts a pin type guide device or a guide rail type guide device and is integrated on the inner surface of the shell and used for limiting the circumferential motion and the radial motion of the spindle-shaped throttle body so as to enable the spindle-shaped throttle body to move freely only in the axial; the high-pressure measuring port and the low-pressure measuring port are respectively arranged at the front part and the middle part of the outer surface of the shell, which are opposite to the spindle-shaped throttle body.

Furthermore, the spindle-shaped throttle body and the shell form an annular flow passage, the metered fluid forms pressure drop in the annular flow passage, and the metering of the fluid flow is realized by utilizing the functional relation between the pressure drop and the flow; the front section of the outer surface of the spindle-shaped throttling body adopts a smooth curved surface which can be guided by the second order in mathematics, so that the rectification effect is realized, the incoming flow is stabilized into a laminar flow, the pressure difference is uniformly distributed along the radial direction, and the pressure difference is reduced along the axial direction with equal gradient, so that the pressure at the high-pressure measuring port is stable; the middle section of the outer surface of the spindle-shaped throttling body adopts a straight line section, so that the pressure at a low-pressure measuring port is stable, the pressure difference is uniformly distributed along the radial direction, and the pressure difference is reduced in an axial equal gradient manner; the rear section of the outer surface of the spindle-shaped throttling body adopts a smooth curved surface which can be guided by the second order in mathematics, and the outlet jet flow of the annular flow channel has sufficient space to decelerate along with the expansion of the flow channel through the slow expansion of the flow channel, so that the turbulent flow when the annular flow channel is suddenly expanded is avoided.

Further, the specific adjusting process of the elastic device for adaptively adjusting the pressure difference between the high-pressure measuring port and the low-pressure measuring port is as follows: when the flow is small, the fluid friction force and the fluid pressure on the surface of the spindle-shaped throttle body are small, and the front and back pressure difference of the spindle-shaped throttle body is also small, so that the surface integral of the stress on the surface of the spindle-shaped throttle body is small, the contraction length of the elastic device is small at the moment due to the stress balance, and then the length of an annular flow passage formed by the shell and the straight line section of the spindle-shaped throttle body between the high-pressure measuring port and the low-pressure measuring port is long, and the pressure loss generated by the fluid flowing through the annular flow passage is in direct proportion to the length of the annular flow passage, so that the pressure difference measured between the high-pressure measuring port and the low-pressure measuring port; when the flow begins to increase, the fluid friction force and the fluid pressure on the surface of the spindle-shaped throttling body are increased, the front and back pressure difference of the spindle-shaped throttling body is increased, the area integral of the stress on the surface of the spindle-shaped throttling body is increased, the contraction length of the elastic device is increased at the moment due to the stress balance, the length of an annular flow passage formed by the shell and the straight line section of the spindle-shaped throttling body of the high-pressure measuring port and the low-pressure measuring port is reduced, the pressure loss generated when the fluid flows through the annular flow passage is in direct proportion to the length of the annular flow passage, the pressure difference measured between the high-pressure measuring port and the low-pressure measuring port is reduced according to a certain proportion at the moment, but the.

Furthermore, the metering section measures the pressure difference between the high-pressure measuring port and the low-pressure measuring port through a pressure difference sensor, converts the pressure difference into the flow metered by the metering section according to a pressure difference-flow formula, and can realize the pressure difference-flow self-adaptive relationship meeting a quadratic curve or the linear pressure difference-flow self-adaptive relationship by adjusting the geometric parameters corresponding to the positions of the shell, the spindle-shaped throttle body, the high-pressure measuring port and the low-pressure measuring port and adjusting the rigidity coefficient of the elastic device.

Compared with the prior art, the invention has the advantages that:

1) because the existing differential pressure sensor has limited measuring range and precision, especially has lower precision at low pressure difference, the differential pressure-flow self-adaptive adjustment of the device can realize the fluid flow measurement of high pressure difference at small flow and low pressure difference at large flow, overcomes the defect of poorer precision of the differential pressure sensor at small flow and low pressure difference, ensures the accurate measurement of the fluid flow in the full measuring range, can be applied to various flow measurement occasions with given flow maximum value and limited measuring pressure difference range, and has extremely high differential pressure measurement precision and flow measurement precision;

2) by adjusting appropriate geometric parameters and stiffness coefficients, a mathematical convex function or a linear differential pressure-flow relation can be realized, the differential pressure-flow is ensured to be in a one-to-one mapping relation, and the reliability of the metering data is ensured;

3) compared with various conventional flow metering devices, the device has the advantages of integration, no need of regulation, realization of self-adaptation of pressure difference and flow, guarantee of effective measurement of the pressure difference, realization of accurate flow metering on the basis, no need of shunt metering of fluid, high integration level, compact structure, convenience in use and the like, and can realize flow metering with low pressure loss, large range ratio and high measurement precision;

4) the pressure difference sensors are fully utilized, the dependence of the metering device on the number and the performance of the pressure difference sensors is greatly reduced, the reliability of fluid flow metering is obviously improved, and the weight, the cost and the complexity are reduced.

Drawings

FIG. 1 is a schematic sectional structure diagram of a differential pressure adaptive metering section of the differential pressure flowmeter of the invention.

FIG. 2 is a pressure difference-flow relation curve diagram of the pressure difference self-adaptive metering section of the pressure difference type flowmeter of the invention.

FIG. 3 is a simulated pressure gradient diagram of the differential pressure adaptive metering section of the differential pressure flowmeter of the present invention.

FIG. 4 is a simulated velocity vector diagram of the differential pressure adaptive metering section of the differential pressure flowmeter of the present invention.

In the figure, 1 is a shell, 2 is a guide device, 3 is a spindle-shaped throttle body, 4 is a high differential pressure measuring port, 5 is a low differential pressure measuring port, and 6 is an elastic device.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings. Examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In describing the present invention, it is to be understood that various terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation to be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the present invention, unless otherwise specifically stated or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or directly integrated and combined; can be directly connected or indirectly connected through an intermediate medium; the connection may be physical, electrical or wireless. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

The differential pressure self-adaptive metering section of the differential pressure type flowmeter shown in fig. 1 is characterized by comprising a shell 1, a guide device 2, a spindle-shaped throttling body 3, a high-pressure measuring port 4, a low-pressure measuring port 5 and an elastic device 6; the whole shell 1 is in a round tube shape, the spindle-shaped throttling body 3 is arranged inside the shell 1 and is coaxially arranged with the shell 2, the elastic device 6 is arranged at the tail part of the spindle-shaped throttling body 3, the guiding device 2 is integrated on the inner surface of the shell 1, and the high-pressure measuring port 4 and the low-pressure measuring port 5 are respectively arranged at the front part and the middle part of the outer surface of the shell 1 relative to the spindle-shaped throttling body 3.

The guiding device 2 is integrated inside the shell 1, in the embodiment, a pin type guiding device is adopted and is integrated with the inner surface of the shell by 180 degrees, a movable groove is formed in a position corresponding to 180 degrees of the outer surface of the spindle-shaped throttling body, and the pin type guiding device is matched with the movable groove, so that the spindle-shaped throttling body can only move along the axial direction of the pin type guiding device, the circumferential rotation and the radial movement of the spindle-shaped throttling body are limited, an annular flow passage with a stable area is formed between the straight section of the spindle body and the shell, and the influence on flow measurement caused by the geometric distortion of the flow passage is avoided.

The front section of the spindle-shaped throttling body 3 adopts a smooth curved surface which can be guided by two orders in mathematics, and mainly realizes the rectification function, so that the incoming flow is stabilized into laminar flow, the pressure difference is uniformly distributed along the radial direction, and the pressure difference is reduced along the axial direction with equal gradient, so that the pressure at the high-pressure measuring port is stable; the middle section of the fusiform throttling body 3 adopts a straight line section, so that the fusiform throttling body 3 and the shell 1 form an annular flow passage with a proper flow area, the pressure at the low-pressure measuring port is stable, the pressure difference is uniformly distributed along the radial direction, and the pressure difference is reduced along the axial direction with equal gradient; the rear section of the spindle-shaped throttle body 3 adopts a smooth curved surface which can be guided by the second order in mathematics, the jet flow at the outlet of the annular runner has sufficient space to decelerate along with the expansion of the runner mainly through the slow expansion of the runner, the turbulent flow when the annular runner is suddenly expanded is avoided, the pressure fluctuation at the outlet of the spindle-shaped throttle body 3 caused by the turbulent flow is avoided, the shake of the elastic device 6 caused by the unstable stress of the spindle-shaped throttle body 3 is avoided, the spindle-shaped throttle body 3 and the shell 1 are coaxially installed, and the straight line section of the spindle-shaped throttle body 3 and the shell 1 form the annular runner.

The high-pressure measuring port 4 is opened on the shell 1, is arranged in front of the spindle-shaped throttle body and is used for measuring the pressure of the high-pressure end of the fluid; the low-pressure measuring port 5 is also opened on the shell 1, is arranged at the middle straight section of the spindle-shaped throttling body and is used for measuring the pressure at the low-pressure end of the fluid, and the pressure difference measured by the high-low measuring port is used for calculating the actual flow of the fluid.

The fluid flow measurement of the present embodiment is to use a differential pressure sensor with a range of 0.1MPa for aviation kerosene with a maximum given flow rate of 550kg/h, and therefore, preferably, the geometric parameters of the above components are as shown in table 1, and the position distances described in table 1 are the positions when the elastic device 6 is in a natural state and is not compressed by fluid pressure and viscous friction:

TABLE 1 differential pressure adaptive metering section parts geometry parameters

In this embodiment, the elastic device 6 is disposed inside the housing 1 and mounted at the tail of the spindle-shaped throttle 3, a mechanical compression spring is adopted, the central axis of the mechanical compression spring is coaxial with the spindle-shaped throttle 3 and is connected with the inside of the housing 1 through a support plate, and through the balance between the elastic force of the elastic device 6 and the fluid pressure and the viscous force applied to the spindle-shaped throttle 3, when the flow rates are different, the compression amount of the elastic device 6 is different, so that the self-adaptive adjustment of the pressure difference along with the flow rate is realized, and the compression length of the elastic device 6 is in direct proportion to the applied pressure, the proportionality coefficient is k, in this embodiment, the stiffness coefficient is selected to be.

The length of an annular flow channel formed by the middle section of the spindle-shaped throttling body 3 between the flow and high-pressure measuring port 4 and the low-pressure measuring port 5 and the shell 1 is coupled, the length of the annular flow channel formed by the middle section of the spindle-shaped throttling body 3 between the high-pressure measuring port 4 and the low-pressure measuring port 5 and the shell 1 is coupled with the measured pressure difference, and the pressure difference of the annular flow channel formed by the middle section of the spindle-shaped throttling body 3 and the shell 1 is coupled with the flow, so that when the flow is changed, the compression length of the elastic device 6 is changed, the length of the annular flow channel formed by the middle section of the spindle-shaped throttling body 3 between the high-pressure measuring port 4 and the low-pressure measuring port 5 and the shell 1 are correspondingly changed, and the.

Relative to the annular flow passage with a fixed position, the differential pressure measured by the differential pressure self-adaptive metering section of the differential pressure type flowmeter in the embodiment does not follow the relationship between the differential pressure and the flow of the common annular flow passage, but follows the relationship between the flow and the length of the annular flow passage formed by the shell 1 and the spindle-shaped throttle body 3 between the high pressure measuring port 4 and the low pressure measuring port 5, the length of the annular flow passage formed by the shell 1 and the spindle-shaped throttle body 3 between the high pressure measuring port 4 and the low pressure measuring port 5 and the measured differential pressure, the differential pressure and the flow of the annular flow passage formed by the shell 1 and the spindle-shaped throttle body 3, and the differential pressure and flow relationship obtained by the triple coupling relationship; when the flow changes, the compression length of the elastic device 6 changes, and the length of the annular flow passage between the high-pressure measuring port 4 and the low-pressure measuring port 5 correspondingly changes, so that the pressure difference measured between the high-pressure measuring port 4 and the low-pressure measuring port 5 is adaptively adjusted according to the flow. The specific working process is as follows:

when the flow is small, the fluid friction force and the fluid pressure on the surface of the spindle-shaped throttle body 3 are small, and the front and back pressure difference of the spindle-shaped throttle body 3 is also small, so that the area integral of the stress on the surface of the spindle-shaped throttle body 3 is small, and the contraction length of the elastic device 6 is small at the moment due to the stress balance, so that the length of an annular flow passage formed by the casing 1 and the straight line section of the spindle-shaped throttle body 3 between the high-pressure measuring port 4 and the low-pressure measuring port 5 is long, and the pressure loss generated by the fluid flowing through the annular flow passage is in direct proportion to the length of the annular flow passage, so that the pressure difference measured by the two pressure difference measuring ports is large at;

when the flow begins to increase, the fluid friction force and the fluid pressure on the surface of the spindle-shaped throttle body 3 are increased, the front and back differential pressure of the spindle-shaped throttle body 3 is increased, so the area integral of the stress on the surface of the spindle-shaped throttle body 3 is increased, the contraction length of the elastic device 6 is increased at the moment due to the balance of the stress, the length of an annular flow passage formed by the shell 1 and the straight line section of the spindle-shaped throttle body 3 is reduced between two differential pressure measurement ports, and the differential pressure measured by the two differential pressure measurement ports is reduced according to a certain proportion because the pressure loss generated by the fluid flowing through the annular flow passage is in direct proportion to the length of the annular flow passage, but the whole trend is still increased, so that the measurement of the.

The differential pressure-flow equation is derived in detail below.

For an annular flow channel, neglecting the change in density, i.e. assuming the fluid is incompressible, the pressure difference-flow relationship in the annular flow channel can be expressed as:

wherein, delta p is the pressure difference before and after the annular flow channel, mu is the viscosity coefficient, and l is the length of the flow channel.

For the elastic means 6 used in this embodiment, there is hooke's law:

F＝kx (3)

meanwhile, for the spindle-shaped throttle body 3 in the present embodiment, the force balance equation is:

whereas, for the spindle-shaped throttle body 3, the total throttle length is fixed to l₁If so:

then there are:

q_max＝k₁Δp_max(7)

simultaneous equations (7), (10) can be derived, with respect to the maximum flow, when the elastic means 6 are compressed to the limit, the compression length of the elastic means 6 is:

for the relative positions of the high pressure measuring port 4 and the low pressure measuring port 5, the remaining annular flow path length is:

l＝l′+x (9)

where l' is the length of the remaining annular flow path between the high pressure measuring port 4 and the low pressure measuring port 5 when the elastic means 3 are compressed to the limit, with respect to the maximum flow, q_maxIs the maximum metered flow.

Since D,. mu.are constants, for convenience of representation, let:

then equations (5), (11) and (12) are obtained, and for this embodiment, the pressure difference-flow relationship is:

wherein k ', l' are,q_maxAre constant coefficients determined on the geometric parameters as in table 1 and on the stiffness coefficient of the elastic means 6 selected.

From this, the pressure difference-flow equation can be derived:

wherein pi is the circumference ratio, D is the inner diameter of the shell and is the difference between the inner diameter of the shell and the diameter of the middle section of the spindle-shaped throttle body, mu is the viscosity coefficient of the measured fluid (aviation kerosene), delta p is the pressure difference measured between the pressure difference measuring ports, when the elastic device with the maximum flow rate is compressed to the limit, the length of the residual annular flow passage between the pressure difference measuring ports, S is the section area of the middle section of the spindle-shaped throttle body, and l is the section area of the middle section of the spindle-shaped throttle body₁Is the length of the middle section of the spindle-shaped throttle body, k is the stiffness coefficient of the elastic device, q is the measured fluid flow_maxA given maximum flow rate of fluid is metered for the designed flow meter. Thereby enabling metering of the flow.

The geometric parameters in this embodiment are substituted into the above formula 1 to obtain the pressure difference flow rate relation curve as plotted in fig. 2. The straight line of the linear relation in fig. 2 is a linear relation expressed by the pressure difference-flow when the rigidity coefficient is infinite, and the curve relation of the mathematical convex in fig. 2 is a relation when the rigidity coefficient is selected to be 0.625N/mm and the pressure difference-flow is self-adaptive through the device. It can be clearly seen from fig. 2 that when the stiffness coefficient and the geometric parameter are selected appropriately, the pressure difference can be changed violently at a small flow rate, and the precision of the small flow rate measurement can be improved, when the geometric parameter and the stiffness coefficient are adjusted to satisfy the linear pressure difference-flow adaptive relationship, the pressure difference is changed uniformly within the full flow rate range, and the flow rate measurement requirement within the full flow rate range is satisfied, and the relationship does not exceed the point of the maximum flow rate value and the maximum pressure difference value on the pressure difference-flow rate relationship curve, that is, when the maximum flow rate value is given, and the allowable pressure difference has the maximum value limit, the flow rate measurement with high precision of the small flow rate or uniform precision of the full flow rate can be realized by adjusting the geometric parameter and the stiffness coefficient. Meanwhile, as can be clearly seen from fig. 2, the pressure difference-flow rate is a monotonous curve, which satisfies the one-to-one mapping, and the one-to-one correspondence of the pressure difference-flow rate can be realized.

In order to further illustrate the reliability of the embodiment in terms of design and the effectiveness of the embodiment in terms of flow measurement, the fluid simulation software FLUENT is used for simulating the fluid profile designed by the embodiment, and in the simulation result, a pressure gradient diagram is shown in fig. 3, and a velocity vector diagram is shown in fig. 4. As can be seen from fig. 3, the pressure gradient is uniformly decreased along the axial direction of the adaptive metering section designed in this embodiment, and is not changed in the radial direction, so that the effectiveness and reliability of the differential pressure-flow metering are ensured, and the measured differential pressure satisfies the functional relationship shown in formula (1). As can be seen from the velocity vector diagram in fig. 4, in the adaptive metering section designed in this embodiment, the spindle-shaped throttle body 3 is preferably designed, so that the fluids flow adherent to the wall without separation, the fluids within the full range do not separate, and the fluids are all in a laminar state, thereby effectively ensuring that the pressure gradient uniformly drops along the axial direction, and ensuring that the force applied to the spindle-shaped throttle body 3 is uniform.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the contents of the specification and the drawings, or applied to other related technical fields directly or indirectly, are included in the scope of the present invention.