Resonance liquid density meter with self-cleaning function

Abstract

The application discloses a resonance type liquid density meter with a self-cleaning function, which comprises a transmission rod, a fixing nut, an excitation source, a vibration pickup source, a flange base, a rubber gasket, a pipeline, a resonance body, a vibration pickup source signal line and an excitation source signal line; the resonance body is immersed in liquid, the transmission rod is connected with the resonance body through the flange base, the excitation source and the vibration pickup source are transitionally matched with the transmission rod through a hole shaft, and then the excitation source and the vibration pickup source are fixed on the flange base by cooperating with the fixing nut; the excitation source signal line is led out from the excitation source, the vibration pickup source signal line is led out from the vibration pickup source, the density meter is screw-connected with the pipeline through a threaded hole of the flange base and through the rubber gasket. The application utilizes the technology of leading a special high-frequency mode vibration mode by inputting a high-frequency alternating current signal to the excitation source, and leads ultrasonic vibration of the density meter, so that the density meter can ultrasonically vibrate in water or air without affecting measurement, and the cleaning effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of liquid density measurement technology, and in particular to a resonant liquid density meter with self-cleaning function. Background Technology

[0002] The resonant liquid density meter is designed to solve the challenges of liquid measurement in petrochemical pipelines, and its technology is primarily based on vibration theory. By applying an AC signal to a piezoelectric excitation source, a resonant body is induced to resonate with the liquid being measured. The resonant frequency is detected by another vibration pickup source, and then amplified, filtered, and shaped by circuitry. This amplification is fed back to the excitation piezoelectric ceramic during density calculation, stabilizing the resonant body at its resonant frequency. When the resonant body is immersed in the liquid, the resonant frequency changes due to the change in the added mass of the vibration system. The liquid density is then measured based on the relationship between mass and density.

[0003] Resonant liquid density meters are primarily designed for pipeline measurements. Therefore, over long-term operation, dirt accumulates on the resonant body, leading to a continuous decrease in testing accuracy. Traditional methods often require removing the density meter from the pipeline and cleaning it with paper towels and detergent. This method is not only ineffective but also labor-intensive and resource-intensive. Therefore, the self-cleaning mechanism of density meters has always been a pressing issue that needs to be addressed.

[0004] Existing liquid densitometers typically employ a tuning fork structure. The tuning fork structure is more complex than that of a resonant liquid densitometer. During measurement, the tuning fork structure is prone to accumulating dirt, and manual cleaning often results in incomplete cleaning, leading to difficulties in cleaning and consequently, poorer performance in the measurement. Furthermore, traditional liquid densitometers use relatively weak excitation sources, such as electromagnetic coils or ordinary piezoelectric ceramics, which, combined with the difficulty in exciting the tuning fork structure, prevent the achievement of optimal results. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a resonant liquid density meter with self-cleaning function. By using a technique of sending a high-frequency AC signal to the excitation source to induce a special high-frequency mode vibration, the density meter is induced to vibrate ultrasonically in water or air without affecting the measurement, thereby achieving a cleaning effect.

[0006] To solve the above-mentioned technical problems, the present invention provides a resonant liquid density meter with self-cleaning function, comprising: a transmission rod 1, a fixing nut 2, an excitation source 3, a vibration pickup source 4, a flange base 5, a rubber gasket 6, a pipe 7, a resonant body 8, a vibration pickup source signal line 10, and an excitation source signal line 11; the resonant body 8 is immersed in liquid 9, the transmission rod 1 passes through the flange base 5 and is connected to the resonant body 8, the excitation source 3 and the vibration pickup source 4 are connected to the transmission rod 1 through a hole-shaft transition fit, and then the fixing nut 2 is used to fix the excitation source 3 and the vibration pickup source 4 on the flange base 5, the excitation source signal line 10 is led out from the excitation source 3, and the vibration pickup source signal line 11 is led out from the vibration pickup source 4, and the density meter is threadedly connected to the pipe 7 through the threaded hole of the flange base 5, through the rubber gasket 6.

[0007] Preferably, the excitation source 3 excites the resonant body 8 to resonate through the inverse piezoelectric effect, and the vibration pickup source 4 detects the resonant frequency of the resonant body 8 through the direct piezoelectric effect.

[0008] Preferably, the excitation source 3 and the vibration pickup source 4 are Landerwen oscillators.

[0009] Preferably, the resonator 8 has a spherical structure or a helical structure.

[0010] Preferably, the resonator 8 has an axisymmetric structure, with the axis of symmetry being the central axis of the transmission rod 1. The excitation source 3 and the vibration pickup source 4 are located at the axis of symmetry of the resonator 8 through the hole and shaft of the transmission rod 1.

[0011] Preferably, when the hydrometer is immersed in liquid 9 for detection, the excitation source 3 excites the resonant body 8 through the transmission rod 1, causing it to resonate at a set frequency. At the same time, the vibration pickup source 4 detects the frequency at which the resonant body 8 resonates. The resonant body 8 vibrates at the detected resonant frequency, and this resonant frequency satisfies the following relationship with the liquid density:

[0012]

[0013] Where ρ is the density of the liquid being measured, f is the resonant frequency, and m0, m1, and m2 are sensor coefficients that need to be determined through calibration experiments.

[0014] Preferably, the natural frequencies and mode shapes of the free vibration of the uniform rod equivalent to that of the densitometer are as follows:

[0015]

[0016] Where, ω n For the natural frequency of the equivalent uniform rod, φ n (x) is the nth natural frequency ω corresponding to the rod. n The natural mode shape function is given by the formula, where c is the propagation velocity of the longitudinal wave along the longitudinal direction of the rod, and l is the rod length. The suitable longitudinal vibration mode and corresponding frequency of the densitometer during self-cleaning can be calculated using the above formula.

[0017] The beneficial effects of the present invention are as follows: (1) The Lander oscillator, as the excitation source, has a stronger excitation capability and a wider frequency range. Using the Lander oscillator as the vibration pickup source, it has higher sensitivity and test accuracy; (2) By applying a high-frequency AC signal to the excitation source, the signal frequency is specially selected to induce longitudinal vibration of the resonant body; according to vibration theory, when the structure vibrates ultrasonically, especially the longitudinal vibration of the high-frequency mode, it can clean the high-viscosity liquid being tested or the dirt left by long-term use; the self-cleaning function is easy to use and can be self-cleaned before each test, which not only greatly reduces labor costs, but also improves the accuracy of online measurement of the density meter; (3) No other mechanical structure is added, it is easy to use and reasonably designed. Not only is the liquid density detection accurate and effective, but the self-cleaning function is also comprehensive, which can ensure long-term online measurement. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the density meter of the present invention.

[0019] Figure 2 This is a schematic diagram of the density meter of the present invention.

[0020] Figure 3 This is a diagram illustrating the self-cleaning function of the density meter of this invention.

[0021] Figure 4 This is a diagram illustrating the ideal uniform beam longitudinal vibration effect of the present invention.

[0022] Figure 5 This is a schematic diagram of the finite element simulation structure of the density meter of the present invention.

[0023] Figure 6 This is a finite element simulation diagram of the low-frequency mode shape of the density meter of this invention.

[0024] Figure 7 This is a finite element simulation diagram of the high-frequency mode shape of the density meter of this invention.

[0025] Figure 8 This is a finite element simulation diagram of the high-frequency mode shape of the density meter of this invention.

[0026] The components are: 1. Transmission rod; 2. Fixing nut; 3. Excitation source; 4. Vibration pickup source; 5. Flange base; 6. Rubber gasket; 7. Pipeline; 8. Resonator; 9. Liquid; 10. Vibration pickup source signal line; 11. Excitation source signal line; 12. Simulation model; 13. Simulation medium. Detailed Implementation

[0027] like Figure 1As shown, a resonant liquid density meter with self-cleaning function includes: a transmission rod 1, a fixing nut 2, an excitation source 3, a vibration pickup source 4, a flange base 5, a rubber gasket 6, a pipe 7, a resonant body 8, a vibration pickup source signal line 10, and an excitation source signal line 11. The resonant body 8 is immersed in liquid 9. The transmission rod 1 passes through the flange base 5 and is connected to the resonant body 8. The excitation source 3 and the vibration pickup source 4 are connected to the transmission rod 1 through a hole-shaft transition fit. The fixing nut 2 is then used to fix the excitation source 3 and the vibration pickup source 4 on the flange base 5. The excitation source signal line 10 is led out from the excitation source 3, and the vibration pickup source signal line 11 is led out from the vibration pickup source 4. The density meter is threadedly connected to the pipe 7 through the threaded hole of the flange base 5, separated by the rubber gasket 6.

[0028] A resonant liquid density meter not only detects the density of liquid 9 but also has a self-cleaning function. It includes a resonant body 8 immersed in the liquid, an excitation source 3 that excites the resonant body to resonate via the inverse piezoelectric effect, a pickup source 4 that detects the resonant frequency of the resonant body via the direct piezoelectric effect, a transmission rod 1, and a flange base 5 that serve as transmission and load-bearing components. When the density meter is immersed in liquid 9 for detection, the excitation source 3 excites the resonant body 8 via the transmission rod 1, causing it to resonate at a preset frequency. Simultaneously, the pickup source detects the resonant frequency of the resonant body 8. Then, through a designed circuit, the resonant body 8 vibrates at the detected resonant frequency. This resonant frequency and the liquid density are related as follows:

[0029]

[0030] In the formula, ρ is the density of the liquid being measured, f is the resonant frequency, and m0, m1, and m2 are sensor coefficients that need to be determined through calibration experiments.

[0031] The excitation source 3 and the vibration pickup source 4 are made of piezoelectric materials. This invention uses a Landerwin oscillator, which is commonly used in the field of ultrasonic vibration, such as ultrasonic motors and ultrasonic cleaning equipment. Therefore, the Landerwin oscillator not only perfectly meets the technical requirements of the self-cleaning function of the density meter of this invention, but also better satisfies the excitation requirements for density measurement.

[0032] In addition, the excitation source signal line 11, serving as a signal input terminal, can transmit not only a low-frequency AC signal that causes the resonant body to resonate, but also a high-frequency AC signal that causes the resonant body to vibrate at high frequencies. This is to enable the densitometer to achieve a self-cleaning function. The vibration pickup source signal 12, serving as a signal output terminal, is used to obtain the resonant frequency of the density measured by the densitometer.

[0033] like Figure 2The diagram shown is a basic structural schematic of the density meter described in this invention. The transmission rod 1 and the flange base 5 are interference-fitted through a hole and shaft, and welding is required to strengthen the fit between the two; the transmission rod 1 and the resonator 8 are connected by threads; the excitation source 3 and the vibration pickup source 4 are transition-fitted to the transmission rod 1 through a hole and shaft, and then fixed with a fixing nut 2 to fix the excitation source 3 and the vibration pickup source 4 on the flange base 5.

[0034] A resonant liquid density meter with a self-cleaning function, wherein the self-cleaning function is performed according to the following steps based on the principle:

[0035] Step 1: To address the issue of decreased measurement accuracy caused by the accumulation of dirt in the density meter during long-term use of pipeline density measurement, an ultrasonic vibration self-cleaning solution is proposed. A Landerwen oscillator is used as the excitation source to stimulate the density meter to complete its self-cleaning under high-frequency vibration.

[0036] Step Two: As Figure 3 The image shown is an illustration of the self-cleaning function of the densitometer. Figure 4 The diagram shows the longitudinal vibration effect of an ideal uniform beam. The designed densitometer structure approximates an ideal uniform beam, thus exhibiting mode shapes similar to those of an ideal uniform beam. Longitudinal vibration under high-frequency conditions can effectively clean the densitometer. Through vibration theory calculations and analysis, the resonant frequency and amplitude that can induce longitudinal vibration at high frequencies (10 MHz) are derived.

[0037] Step 3: Based on mechanical vibration theory, the natural frequencies and mode shapes of the equivalent uniform rod of the densitometer can be calculated as follows:

[0038]

[0039] Where, ω n For the natural frequency of the equivalent uniform rod, φ n (x) is the nth natural frequency ω corresponding to the rod. n The natural mode shape function is given by the formula, where c is the propagation velocity of the longitudinal wave along the longitudinal direction of the rod, and l is the rod length. Using the above formula, the suitable longitudinal vibration mode and corresponding frequency for the hydrometer during self-cleaning can be calculated. As can be seen from the formula, selecting a higher-order longitudinal vibration mode results in a higher natural frequency and a shorter period for the natural mode shape function. The resulting vibration effect is that the hydrometer's transmission rod and resonant body vibrate more rapidly up and down, thus making self-cleaning more effective. Therefore, the resonant liquid hydrometer disclosed in this invention must employ higher-order longitudinal vibration to achieve its self-cleaning function.

[0040] like Figure 5 As shown, after proving its feasibility from vibration theory, the low-frequency and high-frequency modes of the density meter can be further analyzed using finite element software. Figure 5This is a schematic diagram of the finite element simulation structure of the density meter described in this invention. In the finite element software, by setting reasonable parameters for the simulation model 12 and performing modal analysis, the various modes of the density meter and their corresponding resonance frequencies can be calculated.

[0041] like Figure 6 The figure shown is a low-frequency mode shape diagram of the densitometer described in this invention, obtained through finite element simulation. It can be seen that this mode shape is a bending vibration, which serves as the basic mode shape for the density measurement function of the densitometer described in this invention. Furthermore, the low-frequency mode vibration frequency is the operating frequency of the densitometer for measuring liquid density.

[0042] Furthermore, in finite element software, parameters such as density and viscosity of the measured medium 13 can be modified to calculate the resonance frequencies of the simulation model 12 in the measured medium 13 with different parameters. This simulates the vibration of the densitometer immersed in liquids of different densities and viscosities, yielding the resonance frequencies in different liquids. This method can identify the direction for optimizing the densitometer dimensions and suitable mode shapes, which is of great significance for improving measurement sensitivity. Therefore, based on the finite element simulation results, the selected low-frequency mode shape is the most suitable mode shape for the sensitivity of the densitometer in this invention.

[0043] like Figure 7 and Figure 8 The figure shows the high-frequency mode shape diagram of the density meter described in this invention, obtained through finite element simulation. It can be seen that this mode shape is longitudinal vibration, which serves as the basic mode shape for the self-cleaning function of the density meter. Based on vibration theory, the free longitudinal vibration model of a uniform beam illustrates that higher-order longitudinal vibrations correspond to higher natural frequencies and mode shapes, resulting in better and faster longitudinal vibrations for the density meter. Therefore, higher-order longitudinal vibrations lead to better self-cleaning effects. In conclusion, high-frequency longitudinal vibration is selected as the basic mode shape for the self-cleaning function of the density meter.

[0044] The specific working process of the density meter of the present invention is as follows: When measuring the density of a liquid, a low-frequency AC signal is sent to the excitation source 3 to induce the resonator 8 to resonate in the liquid, and the vibration pickup source 4 detects the resonant frequency. This process is repeated. When the liquid being measured changes or the measurement accuracy decreases after a period of use, the density meter needs to be cleaned. In this case, a high-frequency AC signal is sent to the excitation source 3 to induce the resonator 8 to vibrate ultrasonically. After running for a period of time, the dirt is shaken off, the density meter is cleaned, and the normal measurement accuracy of the density meter is restored.

Claims

1. A resonant liquid density meter with self-cleaning function, characterized in that, include: Transmission rod (1), fixing nut (2), excitation source (3), vibration pickup source (4), flange base (5), rubber gasket (6), pipe (7), resonator (8), vibration pickup source signal line (10) and excitation source signal line (11); the resonator (8) is immersed in liquid (9), the transmission rod (1) passes through the flange base (5) and connects to the resonator (8), the excitation source (3) and vibration pickup source (4) are connected to the transmission rod (1) through a hole-shaft transition fit, and then the fixing nut (2) is used to fix the excitation source (3) and vibration pickup source (4) on the flange base (5), the excitation source signal line (11) is led out from the excitation source (3), and the vibration pickup source signal line (10) is led out from the vibration pickup source (4). The density meter is threadedly connected to the pipe (7) through the threaded hole of the flange base (5) and through the rubber gasket (6); When the hydrometer is immersed in the liquid (9) for testing, the excitation source (3) excites the resonant body (8) through the transmission rod (1) to make it resonate at a set frequency. At the same time, the vibration pickup source (4) detects the frequency of the resonant body (8) at the resonance. The resonant body (8) vibrates at the detected resonance frequency. This resonance frequency and the liquid density satisfy the following relationship: in, Let f be the density of the liquid being measured, and f be the resonant frequency. These are the sensor coefficients that need to be determined through calibration experiments; The natural frequencies and mode shapes of the uniform rod undergoing free vibration, equivalent to that of a densitometer, are as follows: ; ； in, The natural frequency of the equivalent uniform rod. The nth natural frequency corresponding to the rod The natural mode shape function, where c is the propagation velocity of the longitudinal wave along the longitudinal direction of the rod. Given the rod length, the suitable longitudinal vibration mode and corresponding frequency of the densitometer during self-cleaning can be calculated using the above formula.

2. The resonant liquid density meter with self-cleaning function as described in claim 1, characterized in that, Excitation source (3) excites the resonant body (8) to resonate through the inverse piezoelectric effect, and vibration pickup source (4) detects the resonant frequency of the resonant body (8) through the positive piezoelectric effect.

3. The resonant liquid density meter with self-cleaning function as described in claim 1, characterized in that, The excitation source (3) and the oscillation source (4) are Langevin oscillators.

4. The resonant liquid density meter with self-cleaning function as described in claim 1, characterized in that, The resonator (8) has a spherical or helical structure.

5. The resonant liquid density meter with self-cleaning function as described in claim 1, characterized in that, The resonator (8) is an axisymmetric structure with the axis of symmetry being the central axis of the transmission rod (1). The excitation source (3) and the vibration pickup source (4) are located at the axis of symmetry of the resonator (8) through the hole and shaft of the transmission rod (1).

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