CN102901598B - Device for measuring radial force of transient-state hydraulic power of centrifugal pump and measuring method thereof - Google Patents

Abstract

The invention provides a centrifugal pump transient hydraulic radial force measuring device and a measuring method thereof. A measuring device is disclosed, comprising a housing 1, a rear fixing ring 2, a compression plate 3, a tight bearing 4, a shaft cavity 5, an elastic support for a tight bearing 6, an operating hole 7, an elastic support for a loose bearing 8, and a loose bearing 9, Front retaining ring 10. The outer rings of the tight bearing 4 and the loose bearing 9 are respectively connected and fixed to the device housing 1 by four elastic supports 6 and 8, the elastic supports are distributed at intervals of 90°, and two longitudinal and transverse strain gauges are installed on each side. For calibration, an object of known mass is placed on the front end of the pump shaft, the output signal of the circuit is amplified, collected and combined for output, and the data in all directions of the device is recorded. Change the mass of the object installed at the front end of the pump shaft, and use the same method to perform multiple measurements to realize the calibration of the device and the conversion of the measured value.

Description

A centrifugal pump transient hydraulic radial force measuring device and its measuring method

technical field

The invention provides a measuring device and method for measuring the transient hydraulic radial force acting on the impeller rotor caused by the unsteady flow inside the centrifugal pump, which belongs to the transient hydraulic radial force and its induced vibration inside the pump machinery related technical fields.

Background technique

Pumps are important energy conversion devices and fluid delivery equipment, among which centrifugal pumps are the most widely used. Centrifugal pumps are not only used in industrial and agricultural fields such as petroleum, chemical industry, and water conservancy, but also are key equipment in high-tech fields such as aviation, ships, and submarines. Centrifugal pumps will inevitably generate vibration during operation, which will affect the stability and safety of centrifugal pump operation and affect the life of the machine. The pump is the key equipment of major projects. Reducing vibration as much as possible can improve the reliability of pump unit operation and reduce the incidence of major accidents, so as to ensure personal safety and avoid loss of national property. It has important social and economic significance. significance. There are many factors that cause vibration problems in centrifugal pumps. In addition to purely mechanical reasons, the periodic load generated by the complex flow inside the pump is also a non-negligible factor that causes vibration, and it is more difficult to control. The phenomenon of flow-induced vibration has become an urgent problem to be solved in engineering practice. Therefore, in order to be able to monitor the vibration load on the components of the centrifugal pump in real time, effectively control the flow-induced vibration, and improve the overall performance of the pump unit and piping system, it is necessary to design a system that can measure the instantaneous hydraulic radial force inside the centrifugal pump in real time. experimental device.

After retrieval, the currently declared patents related to the radial force measuring device are: a radial force measuring instrument, application number 201020297952; a measuring device for measuring radial force and/or axial force, application number 01822374.5; a measuring Radial force sensor, application number 201020628728.6; a radial force measuring instrument and its lip seal ring radial force value measurement method, application number 201010274222.4; oil seal radial force dynamic measuring instrument, application number 88217115. At present, in these patents, there is no measuring device for the instantaneous radial force of the centrifugal pump impeller rotor in the rotating state, there is no measuring device suitable for the installation of the ordinary centrifugal pump bearing seat structure, and there is no perfect rotating coordinate system for the accurate radial force of the pump impeller. Methods of measurement and conversion.

Contents of the invention

The purpose of the present invention is to propose a device with simple structure, low price, high response frequency and high precision, which can realize the measurement of transient radial force on the rotating mechanism of the centrifugal pump. A new housing structure is proposed, and new measurement, calibration and conversion methods are established.

The device of the present invention comprises a device housing, a rear fixing ring, a pressing plate, a tight bearing, a shaft cavity, a tight bearing support, an operation hole, an elastic support of a loose bearing, a loose bearing and a front fixing ring. The device housing is connected to the external fixed end, the rear fixing ring is connected to the device housing, the pressing plate is connected to the rear fixing ring, the elastic support of the tight bearing and the loose bearing is fixedly connected to the housing, and the front fixing ring is connected to the housing. The device housing is connected. The shaft cavity is used to install the pump shaft, and the operation hole is convenient for installing strain gauges and routing sensor cables. The outer ring of the bearing is connected and fixed with the device housing by 4 elastic support plates. The dimensions of the elastic plates are: length 15cm, width 5cm and thickness 1cm. The elastic support material is phenyl silicone rubber, which is a polymer damping material. When the material is thermally deformed, it can maintain a stable dynamic modulus, and the Shore A hardness of the material is 50-70 degrees. The elastic supports are distributed at intervals of 90° in the radial direction, and the 5cm*1cm plane of the support plate is respectively connected with the bearing and the bearing seat. Two strain gauges are placed on each 15cm*5cm side of each elastic support plate, and they are distributed perpendicular to each other to measure the bending deformation in two directions respectively. Therefore, the deformation of the elastic support in each direction can be obtained, so that It is convenient to analyze the force of the bearing structure. A total of 4 strain gauges on each elastic support form a whist bridge measurement circuit, which has a high response frequency and can eliminate errors caused by temperature changes and strain unit bending. In addition, the purpose of simultaneously measuring the radial force at the loose and tight bearings is that the measurement of one bearing can be used to check the reliability of the deformation measurement at the previous bearing.

For the above measuring devices, special calibration and radial force conversion methods are proposed. Remove the impeller and the pump casing from the device, leaving only the pump shaft installed on the measuring device, place an object of known mass on the front end of the pump shaft, and fix the two bearings on a total of 8 sets of whist The output signal of the electric bridge is amplified, collected and combined for output. Then keep the shaft and the loaded object stationary, and then measure after the measuring mechanism rotates 45°. After collecting the data of the entire circumference (8 positions), change the mass of the object installed at the front end of the pump shaft and perform another measurement. By analogy, a total of multiple sets of measurements with different calibration qualities are performed. This can ensure that the measuring device can collect signals in all radial directions to calculate the radial force. At the same time, since the added mass is known, the corresponding gravity value can be calculated, so the output voltage of the bridge in any radial direction can be drawn. The linear relationship diagram between the value and the radial force on the device realizes the calibration of the device and the conversion of the measurement and the actual value.

The invention has the advantages of: designing for the structure of the bearing seat of the centrifugal pump, the structure of the test device is simple, the price of the strain gauge sensor is low, but the precision is high, the response frequency of the bridge circuit is high, and the measurement of the dynamic signal can be realized. The measurement and conversion of the radial force on a rotating body under a fixed coordinate system.

Description of drawings

Figure 1 is a schematic diagram of a centrifugal pump hydraulic radial force measurement device.

Figure 2 is the A-A section of Figure 1

Fig. 3 is a schematic diagram of the arrangement of strain gauges on the elastic support.

In the figure, 1. Device housing, 2. Rear fixed ring, 3. Compression plate, 4. Tight bearing, 5. Shaft cavity, 6. Tight bearing elastic support, 7. Operation hole, 8. Loose bearing elastic support, 9. Loose bearing, 10. Front retaining ring

Figure 4 is an example result of measuring the radial force of a single vane centrifugal pump using this method.

Detailed ways

The measuring device of the present invention is described in detail below in conjunction with the example and accompanying drawing of the radial force measurement that utilizes this device to carry out:

As shown in Fig. 1, the present invention comprises device housing (1), rear fixed ring (2), pressure plate (3), tight bearing (4), shaft cavity (5), tight bearing elastic support (6), Operation hole (7), loose bearing elastic support (8), loose bearing (9) and front fixed ring (10) form. Among them, the device housing (1) is connected with the external fixed end, the rear fixed ring (2) is connected with the device housing (1), the pressing plate (3) is connected with the rear fixed ring (2), and the tight bearing is elastically supported (6) and the loose bearing elastic support (8) are fixedly connected with the housing (1), and the front fixing ring (10) is connected with the device housing (1). The shaft cavity (5) is used to install the pump shaft, and the operation hole (7) is convenient for installing strain gauges and arranging sensor cables. The outer ring of the bearing (4) (9) is connected and fixed with the device housing (1) by 4 elastic support plates (6) (8). The size of the elastic plate is: length 15cm, width 5cm and thickness 1cm. It is phenyl silicone rubber, which is a polymer damping material, which can maintain a stable dynamic modulus when the material is thermally deformed. The Shore A hardness of the material is 50-70 degrees. The elastic supports are distributed at intervals of 90° in the radial direction, and the 5cm*1cm plane of the support plate is respectively connected with the bearing and the bearing seat. Two strain gauges are placed on each 15cm*5cm side of each elastic support plate, and they are distributed perpendicular to each other. Q1 and Q2 measure axial deformation, and L1 and L2 are used to measure radial deformation, as shown in Figure 3. Therefore, the deformation of the elastic support in all directions can be obtained, which facilitates the analysis of the force on the bearing structure, as shown in Figure 2. A total of 4 strain gauges on each elastic support form a whist bridge measurement circuit, which has a high response frequency and can eliminate errors caused by temperature changes and strain unit bending. In addition, the purpose of measuring the radial force at the loose bearing and the tight bearing at the same time is to use the measurement of one bearing to check the reliability of the deformation measurement at the previous bearing.

The calibration and conversion method for measuring the radial force is as follows: remove the impeller and the pump casing from the device, leaving only the pump shaft installed on the measuring device, and place an object with a known mass m _cal on the front end of the pump shaft, The output signals of 4 groups of Whistler bridges on each bearing fixed support are respectively amplified, collected and combined for output. Then keep the shaft and the loaded object stationary, and measure once every 45° rotation of the measuring device until the data of the entire circumference (8 positions) are collected, which can ensure that the measuring device can collect signals in all radial directions for radial measurement. force calculation. Change the mass of the object installed at the front end of the pump shaft, and use the same method to measure again, and so on to perform a total of multiple sets of measurements with different calibration masses. At the same time, since the added mass m _cal is known, it can be calculated according to formula (1)

F _g = m _cal g (1)

Calculate the gravity value F _g used for calibration, so the linear relationship between the output voltage value of the bridge in any radial direction and the radial force on the bearing can be obtained (2) and (3)

$\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; fixed</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; ref</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; fixed</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

$\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; loose</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; ref</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; loose</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, F _fixed and F _loose are the radial force on the tight bearing and loose bearing respectively, which can be simply converted from F _g , F _ref is the reference value of the force, U _fixed and U _loose are the tight and loose bearings respectively The output voltage of the pine bearing bridge circuit, a and b are the linear coefficients of the radial force and the output voltage of the bridge circuit. Thus, the calibration of the device and the conversion of the measured electrical signal and the actual radial force value can be realized.

Claims (3)

1. A centrifugal pump transient hydraulic radial force measuring device, comprising housing (1), tight bearing (4), loose bearing (9), shaft chamber (5), is characterized in that, also includes rear retaining ring ( 2), compression plate (3), tight bearing elastic support (6), operation hole (7), loose bearing elastic support (8), front fixing ring (10); The outer ring of the bearing is connected and fixed with the device housing by 4 elastic support plates. The size of the elastic plate is 15cm in length, 5cm in width and 1cm in thickness. The elastic support material is polymer damping material phenyl silicone rubber. When the material is thermally deformed It can maintain a stable dynamic modulus, and the Shore A hardness of the material is 50-70 degrees; The elastic supports are distributed at 90° intervals in the radial direction, and the 5cm*1cm planes of the support plates are respectively connected to the bearing and the bearing seat; 2 strain gauges are placed on each 15cm*5cm side of each elastic support plate, and they are perpendicular to each other. The distribution is used to measure the bending deformation in two directions respectively, so the deformation of the elastic support in each direction can be obtained, so as to facilitate the analysis of the bearing structure force; A total of 4 strain gauges on each elastic support form a whist bridge measurement circuit, which has a high response frequency and can eliminate errors caused by temperature changes and strain unit bending. 2. A centrifugal pump transient hydraulic radial force measuring method is characterized in that, it is applied to the centrifugal pump transient hydraulic radial force measuring device as claimed in claim 1; to loose bearing and tight bearing place radial force measurement The purpose is that the measurement of one bearing can be used to check the reliability of the deformation measurement at the previous bearing; the method is: An object of known mass is placed at the front end of the pump shaft to amplify, collect and combine the output signals of 4 sets of Whistler bridges on the fixed support of each bearing; Then keep the pump shaft and the loaded object still, and measure once every 45° rotation of the measuring device until the data of one cycle is collected, so as to ensure that the measuring device can collect signals in all directions in the radial direction to calculate the radial force; Change the mass of the object installed at the front end of the pump shaft, and use the same method to perform multiple measurements. 3. method as claimed in claim 2, is characterized in that, also comprises: Draw the linear relationship diagram of arbitrary radial direction Whistler bridge output voltage value and the different radial force that measuring device suffers, realizes measuring device Calibration and conversion of measured values.