CN1180226C - Electromagnetic differential vortex flowmeter - Google Patents

Abstract

The present invention discloses an electromagnetic differential vortex street flowmeter. Two blunt bodies, a front blunt body and a rear blunt body, are arranged in a measuring pipe vertical to the shaft line of the measuring pipe, wherein a symmetrical position for the side surface of the rear blunt body is provided with two groups of identical sensors which constitute a differential sensor connected with a secondary meter outside the measuring pipe through a line. A magnetic exciter is arranged on the outer wall of the measuring pipe and a vortex street generated by the blunt bodies and the differential sensor are arranged in a magnetic field generated by the magnetic exciter, wherein the direction of the magnetic field generated by the magnetic exciter is vertical to a plane formed by the differential sensor. After a vortex initiated by the front blunt body of the invention in the measuring pipe drops out and passes through the rear blunt body, the same phase superposition of vortex street signals are realized at both sides of the rear blunt body so that the strength of the signals are enhanced without signal frequency change so that fluid oscillation is reinforced and a measuring lower limit is reduced. The differential sensor can inhibit common-mode interference signals and can also avoid interference caused by ambient pressure oscillation to improve measuring precision.

Description

Translated fromChinese

电磁差动式涡街流量计Electromagnetic differential vortex flowmeter

                          技术领域Technical field

本发明是属于流体计量设备，特别是涉及一种电磁差动式涡街流量计。The invention belongs to fluid metering equipment, in particular to an electromagnetic differential vortex flowmeter.

                          背景技术 Background technique

现有技术中，用于化工方面的磁电涡街流量计，专利号为98207578.2，是一种抗干扰能力较强的磁电采样结构的涡街流量计，它包括流体管道、一个涡流发生体、采样检测体及采样电路，在涡流发生体的后面或贴合或分置一个磁电采样检测体，采样信号引至采样电路，通过检测电信号频率而获得涡流频率，便可间接测得流体的流速与流量。该实用新型磁电涡街流量计也是利用流体力学中著名的“卡门涡街”原理结合磁电系统而成的。与现有技术的涡街流量计相比，结构简单，检测微弱信号的能力有所增强、抗干扰能力有所提高。但是该现有技术由于采用单钝体涡街发生体，存在以下两大问题：In the prior art, the magnetoelectric vortex flowmeter used in the chemical industry, the patent number is 98207578.2, is a vortex flowmeter with a magnetoelectric sampling structure with strong anti-interference ability, which includes a fluid pipeline, a vortex generator , Sampling detection body and sampling circuit, a magnetoelectric sampling detection body is attached or separated behind the eddy current generator, the sampling signal is led to the sampling circuit, and the eddy current frequency is obtained by detecting the frequency of the electrical signal, and the fluid can be measured indirectly velocity and flow. The utility model magnetoelectric vortex street flowmeter is also made of the famous "Karman vortex street" principle in fluid mechanics combined with the magnetoelectric system. Compared with the vortex flowmeter in the prior art, the structure is simple, the ability to detect weak signals is enhanced, and the anti-interference ability is improved. But this prior art has the following two major problems due to the use of a single blunt body vortex generator:

(1)可测量的流量下限高，因为旋涡的脱落频率与流体的流速成正比，而旋涡脱落的频率与斯特罗哈数(Strouhal Number)有关，只有当雷诺数在某一范围内时，斯特罗哈数才为常数，此时旋涡脱落频率与被测流体的流速成正比，钝体绕流的这一特性限制了它的测量范围，再加上由于机械振动干扰的存在，实际测量的下限要高于理论下限；采用单涡街发生体，对于微弱的涡流脱落不能得到有效的加强，因此微弱的涡流脱落给其在磁场中切割磁力线转化成的电波变化频率的测量带来了一定的难度。(1) The lower limit of the measurable flow rate is high, because the frequency of vortex shedding is proportional to the flow velocity of the fluid, and the frequency of vortex shedding is related to the Strouhal Number. Only when the Reynolds number is within a certain range, The Stroha number is a constant. At this time, the frequency of vortex shedding is proportional to the flow velocity of the measured fluid. This characteristic of the flow around the blunt body limits its measurement range. In addition, due to the existence of mechanical vibration interference, the actual measurement The lower limit is higher than the theoretical lower limit; using a single vortex street generator, the weak eddy current shedding cannot be effectively strengthened, so the weak eddy current shedding brings certain problems to the measurement of the frequency change of the electric wave transformed by cutting the magnetic force line in the magnetic field. difficulty.

(2)由于采用单个采样检测体，对于涡街发生体两侧的流体外界环境的共模干扰，不能抑制，在二次仪表中很难将其去掉，明显地影响测量的准确性。(2) Due to the use of a single sampling detection body, the common mode interference of the fluid external environment on both sides of the vortex street generator cannot be suppressed, and it is difficult to remove it in the secondary instrument, which obviously affects the accuracy of the measurement.

                          发明内容Contents of Invention

本发明的目的在于克服上述现有技术的不足和缺陷，提供一种可明显改善抗干扰性能、提高测量精度及降低流量测量下限的电磁差动式涡街流量计。The object of the present invention is to overcome the shortcomings and defects of the above-mentioned prior art, and provide an electromagnetic differential vortex flowmeter that can significantly improve the anti-interference performance, improve the measurement accuracy and reduce the lower limit of flow measurement.

它包括测量管、传感器、二次仪表，测量管内有两个均垂直于测量管轴线安装的钝体，即前钝体和后钝体；测量管内装有内衬，垂直于测量管轴线安装前钝体和后钝体，在后钝体的侧面对称位置上，装有相同的两组传感器，其中两组传感器的一个电极是安装在后钝体上，两组传感器的另一个电极是通过联接螺栓安装在测量管上，两组传感器构成一个差动式传感器，两组传感器分别通过线路与测量管外的二次仪表连接；由电磁铁、线圈组成的励磁装置和由电磁铁、线圈组成的励磁装置对称地安装在测量管外，后钝体产生的涡街及两组传感器均置于励磁装置两线圈产生的稳定且分布均匀的磁场中，两励磁装置产生的磁场方向垂直于差动传感器所构成的平面。It includes a measuring tube, a sensor, and a secondary instrument. There are two blunt bodies installed perpendicular to the axis of the measuring tube in the measuring tube, namely the front blunt body and the rear blunt body; The blunt body and the rear blunt body are equipped with the same two sets of sensors on the side symmetrical position of the rear blunt body, one electrode of the two groups of sensors is installed on the rear blunt body, and the other electrode of the two groups of sensors is connected by Bolts are installed on the measuring tube, two sets of sensors form a differential sensor, and the two sets of sensors are respectively connected to the secondary instrument outside the measuring tube through lines; the excitation device composed of electromagnet and coil and the The excitation device is installed symmetrically outside the measuring tube. The vortex street generated by the rear blunt body and the two sets of sensors are placed in the stable and evenly distributed magnetic field generated by the two coils of the excitation device. The direction of the magnetic field generated by the two excitation devices is perpendicular to the differential sensor. constituted plane.

所说的前钝体和后钝体均采用其横截面为非流线型的三棱柱体。Said front blunt body and rear blunt body all adopt the triangular prism whose cross section is not streamlined.

本发明具有的有益的效果是：The beneficial effects that the present invention has are:

1)本发明提供的电磁差动式涡街流量计，前钝体在测量管中引发的旋涡脱落经过后钝体后，在后钝体周围实现同相位叠加的最佳钝体组合，这种叠加只是增强了信号的强度而不改变信号的频率，使流体振动得到加强，降低计量的下限；1) In the electromagnetic differential vortex flowmeter provided by the present invention, after the vortex shedding caused by the front blunt body in the measuring tube passes through the rear blunt body, the optimal combination of the same phase superimposed blunt bodies is realized around the rear blunt body. Superposition only enhances the strength of the signal without changing the frequency of the signal, which strengthens the fluid vibration and reduces the lower limit of measurement;

2)本发明利用后钝体两侧的流体振动具有180°相位差的特点，采用差动式传感器抑制共模干扰信号，明显提高流量计的抗干扰性能；2) The present invention utilizes the characteristics of 180° phase difference between the fluid vibrations on both sides of the rear blunt body, adopts differential sensors to suppress common-mode interference signals, and significantly improves the anti-interference performance of the flowmeter;

3)本发明利用运动流体切割磁力线产生周期性变化的感应电动势信号，差动式传感器检测出电动势波动频率，通过磁电转化方式对外界机械振动的影响可有力抑制，所以可以避免这些外界压力振动带来的干扰，提高本发明的测量精度。3) The present invention utilizes the moving fluid to cut the magnetic field lines to generate periodically changing induced electromotive force signals. The differential sensor detects the electromotive force fluctuation frequency, and the influence on external mechanical vibrations can be effectively suppressed through the magnetoelectric conversion method, so these external pressure vibrations can be avoided The interference caused improves the measurement accuracy of the present invention.

                        附图说明Description of drawings

图1为本发明的结构原理图；Fig. 1 is a structural principle diagram of the present invention;

图2为本发明的结构示意图；Fig. 2 is a structural representation of the present invention;

图3为图2沿A-A平面的剖面图。Fig. 3 is a sectional view of Fig. 2 along the A-A plane.

                        具体实施方式 Detailed ways

下面结合附图和实施例详细说明本发明的具体实施方式。The specific implementation manner of the present invention will be described in detail below in conjunction with the accompanying drawings and examples.

如图1、图2、及图3所示，本发明提供一种电磁差动式涡街流量计，它包括：带有法兰1的测量管2(测量管内装有内衬10)、传感器(由13、14组成的左传感器和由5、17组成的右传感器)、励磁装置的电磁铁7、线圈12和励磁装置的电磁铁16、线圈18及二次仪表24，在测量管2内并垂直于测量管2轴线安装两个钝体即前钝体3和后钝体8，后钝体采用了可拆卸的结构，分拆时，把后钝体压盖23取下，就可以取下后钝体8，压盖23通过联接螺栓21和测量管联接在一起。在后钝体8的侧面对称位置上，装有相同的两组传感器13、14及5、17，其中两个传感器5、14的两个电极是安装在后钝体本体上的，另外两个传感器13、17的两个电极是通过联接螺栓20安装在测量管2上的。两组传感器13、14及5、17构成一个差动式传感器，两组传感器13、14及5、17分别通过线路与测量管2外的二次仪表24连接；所述的励磁装置的电磁铁7、线圈12和励磁装置的电磁铁16、线圈18安装在测量管2外，通过保护垫6由上箱盖4和下箱盖22保护起来，上下箱盖内部设有支持筋板19，上下箱盖通过联结螺栓11联结起来，后钝体8产生的涡街及两组传感器13、14及5、17均置于励磁装置12、18产生的稳定且分布均匀的磁场中，励磁装置的电磁铁7、线圈12和励磁装置的电磁铁16、线圈18产生的磁场方向垂直于差动式传感器所构成的平面，电极所测涡街信号由引线15通过接线出口孔9送到二次仪表中。在本实施例中，前钝体3和后钝体8均采用非流线型，如三棱柱体、梯形柱体、以及其他异性非流线型钝体。As shown in Figure 1, Figure 2, and Figure 3, the present invention provides an electromagnetic differential vortex flowmeter, which includes: ameasuring tube 2 with a flange 1 (the measuring tube is equipped with a liner 10), a sensor (the left sensor made up of 13,14 and the right sensor made up of 5,17), theelectromagnet 7 of the excitation device, thecoil 12 and theelectromagnet 16 of the excitation device, thecoil 18 and thesecondary instrument 24, in themeasuring tube 2 And two blunt bodies are installed perpendicular to the axis of themeasuring tube 2, that is, the frontblunt body 3 and the rearblunt body 8. The rear blunt body adopts a detachable structure. Lower the rearblunt body 8, thegland 23 is connected together with the measuring tube through the connectingbolt 21. On the side symmetrical position of rearblunt body 8, identical two groups ofsensors 13,14 and 5,17 are housed, wherein two electrodes of twosensors 5,14 are installed on the rear blunt body body, the other two The two electrodes of thesensors 13 , 17 are mounted on themeasuring tube 2 via connectingbolts 20 . Two groups ofsensors 13, 14 and 5, 17 constitute a differential sensor, and two groups ofsensors 13, 14 and 5, 17 are respectively connected with thesecondary instrument 24 outside themeasuring tube 2 by lines; the electromagnet of theexcitation device 7. Thecoil 12 and theelectromagnet 16 andcoil 18 of the excitation device are installed outside themeasuring tube 2, and are protected by theupper box cover 4 and thelower box cover 22 through theprotective pad 6, and the upper and lower box covers are provided with supportingribs 19, the upper and lower The case cover is connected by connectingbolts 11. The vortex street produced by the rearblunt body 8 and the two groups ofsensors 13, 14 and 5, 17 are all placed in the stable and uniformly distributed magnetic field generated by theexcitation device 12, 18. The electromagnetic field of the excitation device The direction of the magnetic field generated byiron 7,coil 12,electromagnet 16 andcoil 18 of the excitation device is perpendicular to the plane formed by the differential sensor, and the vortex signal measured by the electrodes is sent to the secondary instrument by thelead wire 15 through thewiring outlet hole 9 . In this embodiment, both the frontblunt body 3 and the rearblunt body 8 adopt a bluff shape, such as a triangular prism, a trapezoidal cylinder, and other bluff bodies of the opposite sex.

当测量流体流量时，本电磁差动式涡街流量计安装在待测流体的管路中，流体流过经前钝体3、后钝体8形成涡街，引起流速场的波动。大量实验证明：在一定雷诺数的范围内，稳定的旋涡发生频率f与旋涡发生体侧流速v₁及柱宽d有如下确定的关系式：When measuring fluid flow, the electromagnetic differential vortex flowmeter is installed in the pipeline of the fluid to be measured, and the fluid flows through the frontblunt body 3 and the rearblunt body 8 to form a vortex street, causing fluctuations in the flow velocity field. A large number of experiments have proved that within a certain range of Reynolds number, the stable vortex occurrence frequency f has the following relationship with the vortex generation body side flow velocity v₁ and column width d:

            f＝(v₁/d)Sr                         (1)f=(v₁ /d)Sr (1)

其中Sr是斯特劳哈尔数，对于三棱柱体形状的钝体，在一定流量范围内是雷诺数的函数，在Re＝300~2□10⁵范围内，Sr是一个常量。Among them, Sr is the Strouhal number. For the blunt body in the shape of a triangular prism, it is a function of the Reynolds number in a certain flow range. In the range of Re=300~2□10⁵ , Sr is a constant.

对于三棱柱体形状的钝体，其钝体侧面与管道璧间的平均流速v₁与管道内流体平均流速v的关系，据推导结果如下：For a blunt body in the shape of a triangular prism, the relationship between the average flow velocity_v1 between the side of the blunt body and the pipe wall and the average flow velocity v of the fluid in the pipe is deduced as follows:

            v₁＝v/(1-1.25d/D)                   (2)v₁ =v/(1-1.25d/D) (2)

式中，D为流量计公称直径。In the formula, D is the nominal diameter of the flowmeter.

把式(1)代入(2)，则有：Substituting formula (1) into (2), we have:

            f＝vSr/{(1-1.25d/D)d}               (3)f＝vSr/{(1-1.25d/D)d} (3)

又：again:

            q_v＝πD²v/4                         (4)q_v ＝πD² v/4 (4)

二次仪表24仪表系数为：The meter factor of thesecondary instrument 24 is:

            K＝f/q_v                             (5)K=f/_qv (5)

把(3)和(4)代入(5)得：Substitute (3) and (4) into (5) to get:

            K＝4Sr/(1-1.25d/D)πdD²             (6)K＝4Sr/(1-1.25d/D)πdD² (6)

对于给定的三棱柱体形状的钝体，其流量计直径D、旋涡钝体特征尺寸d及斯特劳哈尔数是可确知的，为此流量计仪表系数K也可确定。For a given blunt body in the shape of a triangular prism, the flowmeter diameter D, the characteristic size d of the vortex blunt body and the Strouhal number can be ascertained, so the meter coefficient K of the flowmeter can also be determined.

由前钝体产生的涡流经过后钝体后叠加的涡流信号，流过励磁装置7、12和16、18产生的磁场时，切割磁力线产生感应电动势，由于涡街的交变作用，在两组传感器13、14及5、17中可测量到频率相同、振幅相近、相位相差180度的电动势波动信号，而机械振动共模干扰信号被抑制，电动势波动的频率同涡流的产生频率相同，因此通过检测电动势波动的信号的频率就可以得到旋涡的频率，由式(2)、(3)和式(5)可以看出，只要准确测得旋涡的分离频率f，就可以准确的得知被测流体的速度，从而达到测量管道内流量的目的。When the eddy current generated by the front blunt body passes through the superimposed eddy current signal after the rear blunt body, when it flows through the magnetic field generated by theexcitation device 7, 12 and 16, 18, the magnetic force line is cut to generate an induced electromotive force. Due to the alternating action of the vortex street, in the twogroups Sensors 13, 14, 5, and 17 can measure electromotive force fluctuation signals with the same frequency, similar amplitude, and 180-degree phase difference, while the mechanical vibration common-mode interference signal is suppressed, and the frequency of electromotive force fluctuations is the same as that of eddy currents. Therefore, through The frequency of the vortex can be obtained by detecting the frequency of the electromotive force fluctuation signal. It can be seen from formulas (2), (3) and (5) that as long as the separation frequency f of the vortex is accurately measured, the measured The velocity of the fluid, so as to achieve the purpose of measuring the flow in the pipeline.

将电动势波动信号在二次仪表24中进行处理和换算，获得流量信息。The electromotive force fluctuation signal is processed and converted in thesecondary instrument 24 to obtain flow information.

因此可以采用电磁差动式涡街流量计可以抑制共模干扰信号，提高其抗干扰性能和测量精度。Therefore, electromagnetic differential vortex flowmeters can be used to suppress common-mode interference signals and improve their anti-interference performance and measurement accuracy.

Claims (2)

1. electromagnetism differential vortex street flow meter, it comprises measuring tube, sensor, secondary instrument, two bluff bodies of all installing perpendicular to the measuring tube axis are arranged in the measuring tube, bluff body and back bluff body promptly, it is characterized in that: liner (10) is housed in the measuring tube (2), perpendicular to measuring tube (2) axis preceding bluff body (3) and back bluff body (8) are installed, on the side symmetric position of back bluff body (8), identical two sensors is housed, two sensors (5 wherein, 14) two electrodes are mounted on the bluff body of back, two other sensor (13,17) two electrodes are to be installed on the measuring tube (2) by attachment bolt (20), two sensors constitutes a differential generator, two sensors (13,14), (5,17) be connected by the outer secondary instrument (24) of circuit and measuring tube (2) respectively; The excitation unit of forming by electromagnet (7), coil (12) and be installed in symmetrically outside the measuring tube (2) by the excitation unit that electromagnet (16), coil (18) are formed, vortex street that back bluff body (8) produces and two sensors place all that excitation unit two coils (12,18) produce the stable and magnetic field that is evenly distributed, the magnetic direction that two excitation units produce is perpendicular to plane that differential pick-up constituted.

2. electromagnetism differential vortex street flow meter according to claim 1 is characterized in that: it is the cylinder of blunt form that said preceding bluff body (3) and back bluff body (8) all adopt its xsect.

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