CN111412956A - Vortex street probe based on acceleration measurement - Google Patents

Abstract

The invention relates to a vortex probe based on a three-axis acceleration sensor, which is composed of three parts, which are a top disc, a middle cylinder and a bottom cuboid. A probe cavity is formed inside the middle cylinder and the bottom cuboid, and the top disc is convenient The pipeline is fixed and is provided with a positioning slot to calibrate the positive direction. The triaxial acceleration sensor as a sensitive element is embedded in the bottom cuboid. The connection between the vortex flowmeter probe cavity and the pipeline is a direct contact hard connection, and it is connected with The generating body does not contact, and the sensitive element is a three-axis acceleration sensor, which can sense the vibration change of the vortex pipeline to measure the vortex flow field information inside the pipeline.

Description

A Vortex Probe Based on Acceleration Measurement

technical field

The invention relates to the field of vortex flow field measurement, in particular, to a vortex probe based on acceleration measurement.

Background technique

The vortex flowmeter is commonly used in the industrial field to measure the volume flow of the fluid. The vortex flowmeter is a velocity-type flow meter based on the Karman vortex principle. It has been widely used because of its insensitivity to changes. On the one hand, the Karman vortex street originates from fluid vibration and is easily disturbed by vibration noise and becomes unstable, while vibration interference inevitably exists in the installation environment of the vortex flowmeter, such as the natural frequency interference of the vortex pipeline or the interference with the pipe. The periodic vibration of the centrifugal pump and compressor connected to the road and the pressure pulsation interference caused by the valve action, etc.

On the other hand, from the perspective of spatial distribution, traditional measurement methods can only obtain "one-dimensional" signals, which are mixed with different flow field information, such as vortex signals, vibration signals, etc., and the signals are mostly frequencies. The information obtained is limited, which is not conducive to subsequent signal analysis.

At present, the acceleration sensor based on MEMS technology tends to be miniaturized, which brings the possibility to realize multidisciplinary cross-measurement. According to Newton's second law, acceleration is proportional to the resultant external force on an object. Integrating the acceleration can get the velocity information, and then integrating it can get the displacement information. In addition, the frequency signal can be obtained by performing frequency domain analysis on the acceleration time domain signal.

SUMMARY OF THE INVENTION

The invention designs a vortex probe based on a MEMS three-axis acceleration sensor. The probe combines the integrated three-axis acceleration sensor and vortex probe, and then designs a reasonable acquisition circuit and vortex probe structure, so that it can realize the functions of accurate vortex frequency measurement and spatial three-dimensional vortex flow field signal measurement. The technical solution is as follows:

A vortex probe based on a three-axis acceleration sensor is composed of three parts: a top disc, a middle cylinder and a bottom cuboid. The middle cylinder and the bottom cuboid form a probe cavity, and the top disc is convenient for pipe fixing and There is a positioning slot to calibrate the positive direction. The triaxial acceleration sensor as a sensitive element is embedded in the bottom cuboid. The connection between the vortex flowmeter probe cavity and the pipeline is a hard connection of direct contact, and is not connected to the generator. Contact, the sensitive element is a three-axis acceleration sensor, which can sense the vibration change of the vortex pipeline to measure the vortex flow field information inside the pipeline.

Description of drawings

Fig. 1 is the structure composition of the vortex probe designed by the embodiment of the present invention;

2 is a schematic diagram of the connection between the probe and the pipeline provided by the implementation of the present invention;

Fig. 3 is a working condition of gas-phase flow rate of P=400kPa, Qg=19.27m3/h (gas-phase flow rate is 28.56m/s) designed by the embodiment of the present invention, (a) is the measurement signal without applying transient excitation on the pipeline And the frequency domain analysis diagram, (b) is the time and frequency signal of the rubber hammer hammering the Y direction;

Fig. 4 is the spatial distribution diagram of the force under the two-phase flow field under the working conditions of P=300kPa and Ql=25m3/h provided by the embodiment of the present invention;

In the drawings: 1- vortex flowmeter probe cavity, 2- pipeline, 3- generator, 4- triaxial acceleration sensor, 5- voltage regulator module, 6- hollow structure.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

As shown in Figure 1, the probe material is magnesium-aluminum alloy. In general, the probe consists of three parts, which are the top disc, the middle cylinder and the bottom cuboid. As a whole, it is the vortex flowmeter probe cavity 1, which mainly includes a hollow structure 6. The top disc is convenient for pipe fixing and has a positioning groove to calibrate the positive direction. The middle cylinder structure can minimize the influence of the probe on the flow field. , the bottom cuboid is embedded in the sensitive element, in order to increase the friction between the vortex signal and the bottom cuboid, the bottom is processed by a milling machine.

As shown in Figure 2, the connection between the vortex flowmeter probe cavity 1 and the pipeline 2 is a hard connection with direct contact, and does not contact the generator 3, so the pipeline can be transmitted to the entire vortex when the vibration occurs. In the probe cavity, the sensitive element can feel the vibration change of the vortex pipeline, so it can realize the measurement of pipeline resonance interference. Therefore, when the pipeline vibrates, it can be transmitted to the entire vortex probe, and the detection element can feel the vibration change of the vortex pipeline. It is used as a sensitive detection element to measure the vortex flow field information inside the pipeline.

The three-axis acceleration sensor 4 has three axial directions, and the voltage stabilization module 5 includes a chip and a voltage stabilization circuit, which are used to ensure a voltage stabilization power supply and prevent the chip from being burned.

The sensor embedded in the end of the probe can sensitively sense the mechanical deformation caused by the vortex impact probe in the pipeline, so as to obtain the acceleration information of the flow field. On the one hand, according to the uniqueness of the vortex signal and the multidirectionality of the vibration signal, the vortex signal is only sensitive to the x-axis, and the vibration is reflected in multiple axes. Analysis can effectively obtain accurate vortex street information.

The following will use the above probe to analyze the three axes of the vortex signal. Through the cooperation of the three axes, the frequency characteristics of each axis can be effectively identified, which reflects the anti-vibration performance of the acceleration vortex probe to a certain extent. Next, the anti-vibration characteristics of the vortex probe will be further studied by applying transient excitation to the vortex pipeline. The test experiment is performed at the gas flow rate of P=400kPa, Qg=19.27m3/h (the gas flow velocity is 28.56m/s) As shown in Figure 3(a), it is the measurement signal and frequency domain analysis without transient excitation applied to the pipeline. From the signal point of view, the vortex street lift frequency is effectively measured on the Z axis, and the vortex street lift frequency is effectively measured on the X axis. The street resistance frequency, the Y axis reflects the frequency information of the Z and X axes and the interference frequency at the same time. Similarly, due to the limitation of the sensor's own structure, there are interference frequencies of about 5kHz and 8kHz.

Fig. 3(b) is the acquisition signal using the rubber hammer to apply excitation on the Y-axis. The time-domain signal completely reproduces the triggering and decay process of the transient excitation signal. Since the excitation direction is the Y-axis direction, it is also more sensitive to vibration. Sensitive, due to the transmissibility of vibration, the other two axes will also be disturbed by vibration to varying degrees. From the perspective of the Y-axis frequency domain, the vibration interference is mostly concentrated in the 1kHz low frequency frequency band, and the excited vibration is less than the interference of the sensor structure itself.

In addition, the amplitude information of the vortex probe is the acceleration with physical meaning, and there is a definite linear relationship between the acceleration and the force. Therefore, the two-phase measurement is taken as an example here, as shown in Figure 4, where P = The spatial distribution of the force in the two-phase flow field under the working condition of 300kPa and Ql=25m3/h. The measured acceleration time series signal is used to reflect the change law of the force in the gas-liquid two-phase flow. Due to the more complex flow environment of the mist flow, the time series signal becomes obviously irregular, and at the same time reflects the complexity of the force change. It can be seen that the acceleration vortex probe has certain advantages in signal identification.

It can be seen from the above analysis that the designed acceleration vortex probe can measure the frequency characteristics of the three axes, and the lift frequency, drag frequency and vibration interference frequency characteristics can be effectively identified through the cooperation of the three axes, and the measured flow rate can be achieved. The purpose of the field multi-dimensional frequency information, and the probe has stable anti-vibration performance, which lays a solid foundation for improving the accuracy and stability of vortex street measurement, and also provides a new idea for the original vortex street signal measurement analysis. Moreover, through the time-domain acceleration signals measured in multiple axial directions, the spatial distribution of the force in the vortex flow can be effectively constructed.

Claims (1)

1. The utility model provides a vortex street probe based on triaxial acceleration sensor, constitute by the triplex structure, be the top disc respectively, middle cylinder and bottom cuboid, the inside probe cavity that forms of middle cylinder and bottom cuboid, the top disc makes things convenient for the pipeline to fix and is equipped with a constant head tank and is used for demarcating the positive direction, embedding bottom cuboid in the triaxial acceleration sensor as sensing element, the connected mode between vortex street flowmeter probe cavity and the pipeline is direct contact's hard connection, and with the generator contactless, sensing element can experience the vibration change of vortex street pipeline for triaxial acceleration sensor, be used for measuring the inside vortex street flow field information of pipeline.

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