Method, device and application for measuring the effect of additives on flow-induced vibrations of a rotor test rig

Abstract

This invention discloses a method, apparatus, and application for measuring the effect of additives on flow-induced vibration of a rotor experimental device, belonging to the field of vibration reduction and noise reduction technology. The method comprises the following steps: placing an accelerometer on the surface of the outer cylinder of the rotor experimental device; closing the drain port on the outer cylinder and opening the injection port and gas injection port; injecting working liquid into the device through a liquid pipe while simultaneously venting gas from the rotor experimental device through a gas pipe until the working liquid completely fills the entire device; activating the drive mechanism to control the inner cylinder of the rotor experimental device to rotate around its axis; when the inner cylinder's rotational speed reaches a set value, shutting off the drive mechanism, and allowing the inner cylinder to continue rotating around its axis due to inertia; and acquiring the flow-induced vibration signal generated by the liquid flow between the inner and outer cylinders using an accelerometer. This invention solves the problem that existing technologies cannot measure and suppress the flow-induced vibration generated in the internal annular cavity of a rotor experimental device, and can measure the flow-induced vibration frequency with high precision.

Description

Technical Field

[0001] This invention belongs to the field of vibration reduction and noise reduction technology, specifically relating to a method, apparatus and application for measuring the effect of additives on flow-induced vibration of a rotor experimental device. Background Technology

[0002] In studies related to fluid vibration, researchers have discovered that when a fluid flows over a solid, it exerts alternating fluid forces on the solid surface, causing the solid to reciprocate. This reciprocating motion of the solid alters the fluid flow pattern, thereby changing the fluid forces acting on the solid surface. In vibration mechanics, this phenomenon of fluid-solid interaction is called flow-induced vibration. Specifically, in the field of marine engineering equipment, reducing flow-induced vibration between the equipment and the surrounding water is of great significance for enhancing the equipment's performance, improving its operational capabilities, and extending its service life. Furthermore, in experiments using a Taylor-Couette rotor flow experimental device composed of two coaxial cylinders to test frictional resistance, fluid viscosity, and fluid heat transfer characteristics, as the rotational speed increases, the working fluid between the inner and outer cylinders forms turbulence during flow, generating structures such as Taylor vortices, which interact with the surrounding solid, thus inducing flow-induced vibration.

[0003] Existing technologies disclose flow-induced vibration suppression devices applicable to external flow-induced vibrations in columnar and tubular objects such as offshore platform pillars and deep-sea risers. These devices utilize a passive control mechanism with a flexible membrane to suppress flow-induced vibrations, are applicable to any flow direction, and exhibit significant suppression effects. However, these devices are only suitable for flow-induced vibrations generated by external fluids. Existing technologies also disclose coaxial rotating corrosion flow simulation systems. These systems employ coaxial inner and outer cylinder experimental setups and primarily target flow corrosion experiments. They utilize a combination of fluid rotation in a pipe and sample detection, but do not consider the interference from external air intake. After air mixing, the flow-induced vibrations of the entire system evolve from periodic vibrations between the solution and solid structure to periodic vibrations resulting from the combined effects of the solution, air, and solid structure. For testing the influence of additive solutions on flow-induced vibrations, the introduction of air alters the tested object, compromising the rigor of the experiment. Furthermore, the electric motor, as the power source for the inner cylinder's rotation, inevitably vibrates, and this vibration is also transmitted to the outer cylinder through the rotating liquid, affecting the accuracy of the measurement results.

[0004] Therefore, this invention proposes a method for measuring the effect of additives on flow-induced vibration based on a rotor experimental device, in order to improve the accuracy and rigor of the measurement. Summary of the Invention

[0005] The technical problem to be solved:

[0006] To overcome the shortcomings of existing technologies, this invention provides a method and apparatus for measuring the effect of additives on flow-induced vibrations in a rotor experimental device. The rotor experimental device includes an inner cylinder and an outer cylinder arranged coaxially. Gas or liquid is injected into the annular cavity between the inner and outer cylinders through gas and liquid pipes on the outer cylinder. After the inner cylinder reaches a set speed controlled by a drive unit, the drive unit stops, and the inner cylinder continues to rotate due to inertia. The vibration signal during this stage is monitored by an accelerometer. By injecting solutions of different concentrations into the annular cavity, the optimal solution concentration for suppressing flow-induced vibrations within the annular cavity can be determined. This invention solves the problem that existing technologies cannot experimentally measure the flow-induced vibrations generated in the annular cavity of a rotor experimental device, and demonstrates the effect of additives on these vibrations, enabling high-precision and wide-range measurement of flow-induced vibrations.

[0007] The technical solution of this invention is: a method for measuring the effect of additives on flow-induced vibration of a rotor experimental device, the specific steps of which are as follows:

[0008] An acceleration sensor is placed on the surface of the outer cylinder of the rotor experimental device;

[0009] Seal the drain port on the outer cylinder and open the injection port and air injection port;

[0010] The working liquid is poured into the device through the liquid pipe, and the gas in the rotor experimental device is discharged through the gas pipe until the working liquid completely fills the entire device.

[0011] Start the drive unit to control the inner cylinder of the rotor experimental device to rotate around the axis;

[0012] When the inner cylinder reaches the set value, the drive unit is turned off, and the inner cylinder continues to rotate around the axis due to inertia;

[0013] The flow-induced vibration signal generated by the liquid flow between the inner and outer cylinders is collected by an accelerometer.

[0014] A further technical solution of the present invention is: the rotational speed setting value of the inner cylinder satisfies the condition that the inner cylinder can continue to rotate for a sufficient time due to inertia after the drive component is turned off, and this time is sufficient to ensure that the acceleration sensor measures a signal sufficient to generate a flow-induced vibration frequency diagram.

[0015] A further technical solution of the present invention is: the flow-induced vibration signal collected by the acceleration sensor is transmitted to the host computer, and the vibration frequency is obtained by analysis and calculation, thereby generating a flow-induced vibration spectrum.

[0016] A further technical solution of the present invention is as follows: after the measurement is completed, the drain port is opened to discharge the working liquid, and at the same time, gas is injected into the device through the air pipe until the gas completely fills the entire device, and then the bottom drain port is closed.

[0017] A rotor experimental device includes an inner cylinder and an outer cylinder arranged coaxially, forming an annular cavity between them; the inner cylinder is controlled by a driving component to rotate around an axis inside the outer cylinder; the top of the outer cylinder has a liquid injection port and a gas injection port, the bottom has a liquid discharge port, and an acceleration sensor is installed on its outer circumferential surface.

[0018] The accelerometer transmits the collected signals to the host computer for analysis and calculation.

[0019] A further technical solution of the present invention is: the outer cylinder is a hollow cylindrical shell fixed on the base, and the material is plexiglass, which allows the liquid flow to be observed from the outside.

[0020] A further technical solution of the present invention is: the liquid injection port is connected to the liquid pipe of the external valve, and the two liquid injection ports are symmetrically arranged on the top surface of the outer cylinder; the air injection port is connected to the air pipe of the external valve, and the two air injection ports are symmetrically arranged on the top surface of the outer cylinder.

[0021] A further technical solution of the present invention is that the inner cylinder is a solid cylinder made of high-density metal material, which can increase rotational inertia.

[0022] A further technical solution of the present invention is: the driving component is an electric motor, which is mounted directly above the outer cylinder via a support frame, and its output shaft is coaxially connected to the inner cylinder via a coupling to drive the inner cylinder to rotate.

[0023] A method for measuring the effect of additives on flow-induced vibration in a rotor testing apparatus is applied to suppress flow-induced vibration within the apparatus. This method determines the optimal working fluid concentration for suppressing flow-induced vibration. The working fluid has a molecular weight of 8 × 10⁻⁶. 6 Polyethylene oxide solution.

[0024] Beneficial effects

[0025] The beneficial effects of this invention are as follows: This invention proposes a method for measuring the effect of additives on the flow-induced vibration of a rotor experimental device. The method comprises a motor, a motor support frame, an inner cylinder, an outer cylinder, a base, a liquid pipe, and a gas pipe, among other components, to achieve the measurement of the flow-induced vibration of the rotor experimental device. The use of additives such as polymers as working solutions in experiments, which can alter turbulence characteristics, delay transition, and suppress initial shear vortices and pressure pulsations during turbulence, thereby reducing flow resistance, is already widely studied. Furthermore, such additives can also suppress flow-induced vibration through a similar mechanism.

[0026] In tests on the suppression of flow-induced vibration of rotor experimental devices using additives such as high molecular weight polymers (e.g., polyethylene oxide), if the influence of external air is not eliminated, the air will participate in the flow along with the working fluid, resulting in air vibration interference during the measurement process, which will cause the sensor measurement results to be too high. In addition, the motor driving the inner cylinder will also vibrate during operation, and the vibration will be transmitted to the inner cylinder through the motor output shaft, and further transmitted to the outer cylinder, which serves as the fixed area for the acceleration sensor, through the working fluid, thus interfering with the sensor measurement and causing the measurement results to be too high.

[0027] In this invention, air pipes and liquid pipes are installed on the existing rotor top cover to perform ventilation / exhaust and liquid injection operations, respectively. This can check the airtightness of the device while minimizing the influence of external air on the vibration test. Moreover, setting the vibration test method to be performed after the inner cylinder stops rotating is beneficial to taking advantage of the large inertia of the inner cylinder and eliminating the influence of motor vibration on the flow-induced vibration test through the motion characteristics of the inner cylinder itself.

[0028] Overall, the method proposed in this patent application has a simple structure and is easy to implement, which can reduce the interference of external air introduction and motor vibration on flow-induced vibration measurement. Attached Figure Description

[0029] Figure 1 This is an isometric view of the test apparatus for a method of measuring the effect of additives on flow-induced vibration of a rotor experimental device, as described in this application.

[0030] Figure 2 This is a half-sectional view of the core structure of the test device for a method of measuring the effect of additives on the flow-induced vibration of a rotor experimental apparatus, as described in this application.

[0031] Figure 3 This is a flowchart of a method for measuring the effect of additives on flow-induced vibration of a rotor experimental apparatus, as described in this application.

[0032] Figure 4 A graph showing the effect of exhaust and no exhaust conditions on the measurement results of rotor flow-induced vibration at 300 r / min.

[0033] Figure 5 The graph shows the influence of the motor's operation and shutdown on the rotor flow-induced vibration test results at 300 r / min.

[0034] Figure 6 The experimental tests conducted in Example 1 under different working fluids showed that the fluid-induced vibration was significantly suppressed in multiple frequency bands, including 0Hz-500Hz, 750Hz-1650Hz, and 2000Hz-12800Hz. (Line graph)

[0035] Figure 7 The experimental tests conducted in Example 2 under different working fluids showed that the fluid-induced vibration was significantly suppressed in the frequency bands of 0Hz-500Hz, 750Hz-1650Hz, 2000Hz-10000Hz, and 11000Hz-12800Hz. (Line graph)

[0036] Explanation of reference numerals in the attached diagram: 1 is the electric motor, 2 is the electric motor support frame, 3 is the liquid pipe of the external valve (symmetrically arranged along both sides of the cross section), 4 is the air pipe of the external valve (symmetrically arranged along both sides of the cross section), 5 is the coupling, 6 is the outer cylinder, 7 is the inner cylinder, 8 is the base, and 9 is the drain port. Detailed Implementation

[0037] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0038] Existing technologies cannot measure or suppress the flow-induced vibration generated within the annular cavity of a rotor experimental device, nor can they determine the impact of air introduced into the working fluid on the experiment. This invention provides a method and apparatus for measuring the effect of additives on the flow-induced vibration of a rotor experimental device. The rotor experimental device used in this method consists of an inner cylinder and an outer cylinder. The outer cylinder is a closed-end cylindrical shell made of plexiglass fixed to a base, allowing external observation of the liquid flow and minimizing signal propagation loss. The inner cylinder is a solid cylinder made of high-density metal to increase inertia. An air extraction / injection pipe and a liquid injection pipe are installed at the top of the outer cylinder to suppress air interference with the flow-induced vibration of the liquid. During use, the rotor experimental device drives the inner cylinder to rotate via a motor. Once the target speed is reached, the motor immediately stops. The greater inertia of the inner cylinder allows for a relatively long measurement time in a power-free state (e.g., experiments show that a 1.1kW motor at 500 r / min speed, an inner cylinder radius of 216 mm, and an outer cylinder diameter of 240 mm takes approximately 10 seconds to stop after shutdown), thus suppressing the interference of motor vibration on the measurement of the flow-induced vibration of the liquid.

[0039] The motor 1 and the support frame 2, and the outer cylinder 6 and the base 7 are connected by screws; the liquid pipe 3, the gas pipe 4 and the outer cylinder 6, and the outer cylinder 6, the inner cylinder 7 and the shaft are connected by interference fit; the motor support frame 2 and the base 8 are directly connected to the ground.

[0040] This invention is applied to suppressing flow-induced vibration in a rotor testing apparatus. The optimal working fluid concentration for suppressing flow-induced vibration is obtained by measuring the effect of additives on the flow-induced vibration of the rotor testing apparatus. The working fluid has a molecular weight of 8 × 10⁻⁶. 6 Polyethylene oxide solution.

[0041] The above technical solution will be analyzed and explained through specific embodiments below.

[0042] Example 1:

[0043] This embodiment 1 presents a method for measuring the effect of additives on the flow-induced vibration of a rotor experimental device. The specific process for measuring the effect of additives on the flow-induced vibration of a rotor experimental device is as follows:

[0044] Step 1: With the bottom drain port closed, open the valves on the liquid pipe and the gas pipe respectively;

[0045] Step 2: Pour the working liquid into the device through the liquid pipe, and at the same time expel the gas in the device through the gas pipe until the working liquid completely fills the entire device.

[0046] Step 3: Start the motor and make it rotate around the shaft;

[0047] Step 4: When the motor reaches the set speed value, turn off the motor;

[0048] Step 5: Use an accelerometer to test the flow-induced vibration generated by the fluid flow between the inner and outer cylinders during the inertial rotation phase of the inner cylinder;

[0049] Step 6: After the test is completed, open the drain port to discharge the working liquid, and at the same time inject gas into the device through the air tube until the entire device is completely filled with gas, then close the bottom drain port.

[0050] The inventors set the rotor device to have a stainless steel solid inner cylinder radius of 216 mm and an organic glass hollow outer cylinder inner wall diameter of 240 mm (i.e., a gap of 12 mm for fluid flow). The device stopped working immediately after the motor reached a speed of 600 r / min. Concentrations of 0 ppm, 50 ppm, 100 ppm, and 200 ppm (ppm means parts per million, the same below) were used, with a molecular weight of 8 × 10⁻⁶. 6 The polyethylene oxide (PEO) solution was tested using the above process. Flow-induced vibration at the outer wall of the outer cylinder of the device was measured using an accelerometer, with reference to... Figure 6 As shown in the figure. The results show that the device can measure relatively obvious flow-induced vibrations, and based on the acceleration levels of different frequency bands within the full frequency range (0-12.8kHz), compared with 0ppm (i.e., pure water), PEO solution has a significant inhibitory effect on flow-induced vibrations in multiple frequency bands such as 300Hz-500Hz, 750Hz-1650Hz, and 2000Hz-5000Hz.

[0051] Example 2:

[0052] This embodiment 2 presents a method for measuring the effect of additives on the flow-induced vibration of a rotor experimental device. The specific process for measuring the effect of additives on the flow-induced vibration of a rotor experimental device is as follows:

[0053] Step 1: With the bottom drain port closed, open the valves on the liquid pipe and the gas pipe respectively;

[0054] Step 2: Pour the working liquid into the device through the liquid pipe, and at the same time expel the gas in the device through the gas pipe until the working liquid completely fills the entire device.

[0055] Step 3: Start the motor and make it rotate around the shaft;

[0056] Step 4: When the motor reaches the set speed value, turn off the motor;

[0057] Step 5: Use an accelerometer to test the flow-induced vibration generated by the fluid flow between the inner and outer cylinders during the inertial rotation phase of the inner cylinder;

[0058] Step 6: After the test is completed, open the drain port to discharge the working liquid, and at the same time inject gas into the device through the air tube until the entire device is completely filled with gas, then close the bottom drain port.

[0059] The inventors set the rotor device to have a stainless steel solid inner cylinder radius of 214 mm and an organic glass hollow outer cylinder inner wall diameter of 250 mm (i.e., a gap of 18 mm for fluid flow). The device stopped working immediately after the motor reached a speed of 500 r / min. Concentrations of 0 ppm, 50 ppm, 100 ppm, and 200 ppm, with a molecular weight of 8 × 10⁻⁶, were used. 6 The polyethylene oxide (PEO) solution was tested using the above process. Flow-induced vibration at the outer wall of the outer cylinder of the device was measured using sensors, referring to... Figure 7 As shown in the figure. The results show that the device can measure relatively obvious flow-induced vibrations, and based on the total acceleration level across the entire frequency band (0-12.8kHz), the PEO solution has a significant inhibitory effect on flow-induced vibrations compared to 0ppm (i.e., pure water).

[0060] Comparative Example 1:

[0061] The rotor experimental device of this invention was configured with an inner cylinder radius of 216 mm and an outer cylinder diameter of 240 mm (i.e., a 12 mm gap for fluid flow). Two sets of experiments were conducted after pure water was introduced into the annular cavity: Experiment 1: Air was injected into the water; Experiment 2: Liquid was injected only without air / venting, using the technical solution of this invention. The test results for both sets were as follows: In Experiment 1, after liquid injection and air intake, the motor stopped after reaching a speed of 300 r / min. During the inertial rotation phase of the inner cylinder, the vibration measured by the accelerometer was within the vast majority of frequency bands (…). Figure 4 The vibration produced by the medium-fine thread was significantly greater than that produced in Experiment 2. Figure 4 (Medium-thick line), see details Figure 4 .

[0062] Comparative Example 2:

[0063] The rotor experimental device of this invention is configured with an inner cylinder radius of 216 mm and an outer cylinder diameter of 240 mm (i.e., a 12 mm gap for fluid flow). After ensuring good airtightness and introducing pure water, two sets of experiments were conducted. Experiment 1: The inner cylinder was continuously rotated by a motor, and vibration was measured using an accelerometer during rotation. Experiment 2: Using the technical solution of this invention, the inner cylinder was rotated to 300 r / min by a motor, at which point the motor stopped, and vibration was measured using an accelerometer during the stage when the inner cylinder continued to rotate due to inertia. Figure 5 It can be seen that the vast majority of frequency bands measured using the technical solution of this invention in Experiment 2 ( Figure 5 The medium-thickness lines are significantly smaller than those obtained using the method in Experiment 1. Figure 5 (Medium-fine thread).

[0064] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method of measuring the effect of an additive on flow-induced vibrations of a rotor test apparatus, characterized by, The specific steps are as follows: An accelerometer is arranged on the surface of the outer cylinder of the rotor experimental device; the rotor experimental device includes an inner cylinder and an outer cylinder arranged coaxially, forming an annular cavity between them; the inner cylinder is controlled by a drive component to rotate around an axis inside the outer cylinder; the top of the outer cylinder has a liquid injection port and a gas injection port, and the bottom has a liquid discharge port, and an accelerometer is installed on its outer circumference; the accelerometer transmits the collected signals to a host computer, which analyzes and calculates them. Seal the drain port on the outer cylinder and open the injection port and air injection port; The working liquid is poured into the device through the liquid pipe, and the gas in the rotor experimental device is discharged through the gas pipe until the working liquid completely fills the entire device. Start the drive unit to control the inner cylinder of the rotor experimental device to rotate around the axis; When the inner cylinder reaches the set value, the drive unit is turned off, and the inner cylinder continues to rotate around the axis due to inertia; The flow-induced vibration signal generated by the liquid flow between the inner and outer cylinders is collected by an accelerometer.

2. The method of claim 1, wherein: The flow-induced vibration signal collected by the acceleration sensor is transmitted to the host computer, where the vibration frequency is obtained through analysis and calculation, and then a flow-induced vibration spectrum is generated.

3. The method of claim 1, wherein: After the measurement is completed, open the drain port to discharge the working liquid, and at the same time inject gas into the device through the air tube until the entire device is completely filled with gas, then close the bottom drain port.

4. The method of claim 1, wherein: The outer cylinder is a hollow cylindrical shell fixed on the base, made of plexiglass, which allows the liquid flow to be observed from the outside.

5. The method of claim 4, wherein: The liquid injection port is connected to the liquid pipe of the external valve, and the two liquid injection ports are symmetrically arranged on the top surface of the outer cylinder; the air injection port is connected to the air pipe of the external valve, and the two air injection ports are symmetrically arranged on the top surface of the outer cylinder.

6. The method of claim 1, wherein: The inner cylinder is a solid cylinder made of high-density metal material, which can increase rotational inertia.

7. The method for measuring the effect of additives on flow-induced vibration of a rotor experimental apparatus according to claim 1, characterized in that: The driving component is an electric motor, which is mounted directly above the outer cylinder via a support frame. Its output shaft is coaxially connected to the inner cylinder via a coupling, driving the inner cylinder to rotate.

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