A piezoelectric sensor device suitable for high temperature measurement

Abstract

The present invention discloses a piezoelectric sensor device suitable for high temperature measurement, which includes a sensor body, a sensor base and a vibration measuring block; two layers of water cooling channels isolated from each other are arranged inside the vibration measuring block, and the water flow directions of the upper water cooling channel and the lower water cooling channel are opposite. The device is not aimed at the sensor itself, but the vibration measuring block connected to the fixed part is designed to reduce the temperature, so that the temperature of the sensor installation surface reaches the working range of the normal temperature vibration sensor, so that ordinary normal temperature vibration sensors can also realize high temperature vibration measurement, which greatly improves the reliability of the sensor during high temperature measurement and reduces the cost of using the sensor.

Description

Technical Field

[0001] The invention relates to a piezoelectric vibration sensor, in particular to a piezoelectric sensor device suitable for high temperature measurement. Background Art

[0002] The vibration sensor works based on the principle of "piezoelectric effect". It is a detection device that converts mechanical quantity into electrical quantity. It can be used to measure vibration impact and linear acceleration. In liquid rocket engine tests and impact vibration tests, acceleration sensors have become an important measurement tool in vibration testing. Commonly used piezoelectric acceleration sensors are as follows Figure 1 As shown, it is a central compression acceleration sensor, and its key component is a piezoelectric chip made of a piezoelectric quartz crystal or ceramic or the like.

[0003] The working principle of piezoelectric sensors is based on the piezoelectric effect of certain dielectric materials (usually quartz wafers), that is, when certain dielectric materials are deformed by external forces in a certain direction, polarization will occur inside and charges will be generated on the surface. This phenomenon is called the piezoelectric effect. The charge output piezoelectric accelerometer uses the charge output of the piezoelectric crystal to be proportional to the force it receives, and the force it receives is proportional to the acceleration value when the sensitive mass is constant. Under certain conditions, the amount of charge generated by the piezoelectric crystal after the force is applied is proportional to the acceleration value felt, and the amount of charge output by the piezoelectric crystal satisfies the following equation:

[0004]

[0005] Where: Q is the charge output by the piezoelectric crystal. ij ――The second-order piezoelectric tensor (piezoelectric constant) of the piezoelectric crystal. m0――The sensitive mass of the sensor. ——Vibration acceleration value, S q is the sensor sensitivity.

[0006] The second-order piezoelectric tensor of the crystal element in each piezoelectric sensor is constant, and the sensitive mass m0 is a constant, so formula (1) shows that the charge generated by the piezoelectric acceleration sensor is related to the vibration acceleration. This is the working principle of the electromechanical conversion performed by the piezoelectric accelerometer.

[0007] As can be seen from the above figure, the characteristics of piezoelectric vibration sensors are firm and reliable structure, wide frequency response range, long service life, and can be designed to be high temperature resistant, etc. According to piezoelectric theory, as the base temperature increases, the piezoelectric constant that reflects the piezoelectric characteristics of the piezoelectric material gradually decreases; when the ambient temperature exceeds the Curie temperature of the piezoelectric material, the piezoelectric material loses its piezoelectricity, resulting in an abnormal waveform of the sensor output signal. Therefore, ordinary vibration sensors cannot achieve vibration measurement in high temperature areas.

[0008] There are two main methods for vibration testing in high temperature environments: non-contact laser measurement and high temperature resistant acceleration sensor measurement.

[0009] When using a non-contact laser vibrometer for measurement, since the surface of the target to be measured has extremely low laser reflection intensity, vibration response measurement in a continuous high temperature environment also requires solving problems such as laser reflection signal enhancement, time domain response data post-processing, and laser vibrometer thermal protection. Therefore, it is difficult to obtain relatively accurate measurement data using a non-contact laser vibrometer. Therefore, high-temperature vibration measurement is currently mainly based on the use of high-temperature resistant acceleration sensors.

[0010] There are certain limitations on the temperature that high-temperature sensors can withstand. Currently, the highest continuous working temperature of high-temperature accelerometers is 780°C. However, high-temperature accelerometers still have the following shortcomings when performing high-temperature vibration measurements:

[0011] 1. The structure of the existing high temperature resistant sensor is usually to apply a water cooling device inside, and then the sensitive element is connected to the cable through the socket on the sensor housing. The connector between the sensor and the cable is in the measuring point and the high temperature area, and often fails in a large vibration environment. This kind of sensor can meet the requirements in laboratories and general occasions, but it is unreliable if it is installed in the high temperature part of the liquid rocket engine for a long time.

[0012] 2. Since a water cooling device is applied inside the high temperature vibration sensor, the overall sensor is large in size and cannot be installed and used in some narrow places. Summary of the invention

[0013] In order to solve the problem that existing piezoelectric sensors are unreliable when installed in high-temperature parts of liquid rocket engines for a long time, and the problem that the sensors are bulky and cannot be installed and used in some narrow parts, the present invention provides a piezoelectric sensor device suitable for high-temperature measurement.

[0014] The specific technical solution of the present invention is:

[0015] A piezoelectric sensor device suitable for high temperature measurement, comprising a sensor body, a sensor base and a vibration measuring block;

[0016] The improvements are:

[0017] Two layers of water cooling channels isolated from each other are arranged inside the vibration measuring block, and the water flow directions of the upper water cooling channel and the lower water cooling channel are opposite.

[0018] Furthermore, the upper water cooling channel and the lower water cooling channel are both S-shaped.

[0019] Furthermore, the vibration measuring block comprises a sensor mounting portion, a middle isolation portion and a base portion which are arranged in sequence from top to bottom;

[0020] The sensor mounting portion is provided with a plurality of screw holes for mounting the sensor body;

[0021] The base part is provided with a mounting hole for docking with the object to be measured;

[0022] A plurality of first baffles parallel to each other are arranged between the middle isolation part and the sensor installation part, thereby forming an S-shaped upper cooling channel;

[0023] A plurality of second baffles parallel to each other are arranged between the middle isolation part and the base part, thereby forming an S-shaped lower cooling channel.

[0024] Furthermore, the plurality of first baffles are arranged on the lower surface of the sensor mounting portion, the upper surface of the middle isolation portion is provided with a plurality of first grooves corresponding to the plurality of first baffles one by one, and the lower ends of the first baffles are embedded in the first grooves.

[0025] Furthermore, the plurality of second baffles are arranged on the upper surface of the base portion, and the lower surface of the middle isolation portion is provided with a plurality of second grooves corresponding to the plurality of second baffles one by one, and the upper ends of the second baffles are embedded in the second grooves.

[0026] Furthermore, the sensor mounting portion, the middle isolation portion and the base portion are connected by welding.

[0027] Furthermore, the sensor mounting portion, the middle isolation portion and the base portion are integrally formed by 3D printing.

[0028] The beneficial effects of the present invention are:

[0029] 1. The present invention is not aimed at the sensor itself, but at the vibration measuring block connected to the fixed part, so that the temperature of the sensor installation surface reaches the working range of the normal temperature vibration sensor. In this way, ordinary normal temperature vibration sensors can also realize high temperature vibration measurement, which greatly improves the reliability of the sensor during high temperature measurement and reduces the cost of using the sensor.

[0030] 2. Compared with the commonly used high-temperature sensors, a water cooling device is applied inside, and then the sensitive element is connected to the cable through the socket on the sensor housing, and the connector between the sensor and the cable is in the measuring point and the high-temperature area. During use, there are still factors such as piezoelectric element instability, sensor strain, and low reliability of connectors and cables. As a result, these sensors have poor reliability when used in harsh environments with large vibrations, and often fail. The present invention cools the vibration measuring block to meet the working environment temperature requirements of the vibration sensor, without any impact on the internal structural components and leads of the sensor.

[0031] 3. Compared with the commonly used high temperature sensors which have a water cooling device inside, which makes the sensor bulky and cannot be properly installed in some narrow places, the present invention provides a cooling structure on the vibration measuring block, which facilitates the installation and use of the sensor in narrow and different space structures.

[0032] 4. The present invention adopts a double-layer water cooling structure in the vibration measuring block. Each layer adopts an independent water inlet and outlet. Different layers can be injected with water flow at different flow rates, which effectively improves the cooling effect. At the same time, under the same flow rate, since the water inlets and outlets of the two layers are opposite, the vibration caused by the water flow rate is offset, which affects the sensor signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of an existing piezoelectric sensor.

[0034] Figure 2 A schematic diagram of the structure of the present invention

[0035] Figure 3 This is a cross-sectional view of the vibration measuring block.

[0036] Figure 4 A cross-sectional view of the base portion.

[0037] Figure 5 It is a cross-sectional view of the cooling layer.

[0038] Figure 6 This is a cross-sectional view of the sensor installation part.

[0039] Figure 7 This is the simulation analysis diagram of the vibration measuring block.

[0040] Figure 8 This is the temperature measurement curve of the vibration block during the actual test.

[0041] The reference numerals are as follows:

[0042] 1-sensor body, 2-connecting seat, 3-connecting screw, 4-vibration measuring block, 5-upper water cooling channel, 6-lower water cooling channel, 7-sensor mounting part, 71-screw hole, 72-first baffle, 8-middle isolation part, 81-first cavity, 82-first groove, 83-second baffle, 9-base part, 91-mounting hole, 92-second cavity, 93-second groove. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0044] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0045] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0046] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] The present invention provides a piezoelectric sensor device suitable for high-temperature measurement. The main design idea is: the sensor body (normal temperature vibration sensor) is installed on the object to be measured through a vibration measuring block, and there is no need to set a water cooling device in the sensor body, but a water cooling structure is set in the vibration measuring block, so that the piezoelectric sensor can be installed in the high temperature (>750℃) part of the liquid rocket engine for a long time and will not be limited by the space in a small part.

[0048] This embodiment provides a specific structure of the piezoelectric sensor device, such as Figure 2 As shown, it includes a sensor body 1, a connecting seat 2, a connecting screw 3 and a vibration measuring block 4;

[0049] A connecting seat 2 is installed at the lower end of the sensor body 1, and the connecting seat 2 is connected to a vibration measuring block 4 by a screw rod 3; the vibration measuring block 4 is installed on the object to be measured;

[0050] Two layers of water cooling channels isolated from each other are arranged inside the vibration measuring block 4, and the water flow directions of the upper water cooling channel 5 and the lower water cooling channel 6 are opposite, and the upper water cooling channel 5 and the lower water cooling channel 6 are both S-shaped.

[0051] like Figure 3 As shown, the vibration measuring block 4 includes a sensor mounting portion 7, a middle isolation portion 8 and a base portion 9 which are arranged in sequence from top to bottom;

[0052] like Figure 4 As shown, the sensor mounting portion 7 is provided with a plurality of screw holes 71 for mounting the sensor body (the screw holes are used to Figure 2 The connection is realized by a middle screw rod, and the screw holes are distributed on the upper surface and the side surface of the sensor mounting part), and a plurality of first baffles 72 parallel to each other are arranged on the lower surface of the sensor mounting part 7;

[0053] like Figure 5 As shown, the middle isolation part 8 includes a first concave cavity 81 opening upward, a first water inlet A1 and a first water outlet A2 are provided on the first concave cavity, and a plurality of first grooves 82 are provided on the inner bottom surface of the first concave cavity 81 corresponding to the positions of the plurality of first baffles 72; a plurality of second baffles 83 parallel to each other are provided on the lower surface of the first concave cavity 81;

[0054] like Figure 6 As shown, a mounting hole 91 for docking with the object to be measured is provided at the bottom of the base part 9, a second concave cavity 92 with an upward opening is provided at the top of the base part 9, a second water inlet B1 and a second water outlet B2 are provided on the side wall of the second concave cavity 92, and a plurality of second grooves 93 are provided on the inner bottom surface of the second concave cavity 92 corresponding to the positions of the plurality of second baffles 83; the second water inlet B1 and the first water outlet A2 are provided on the same side, and the second water outlet B2 and the first water inlet A1 are provided on the same side, so that the influence of the vibration caused by the water flow rate on the sensor signal can be offset;

[0055] The sensor mounting part 7, the middle isolation part 8 and the base part 9 are connected together by welding, wherein a plurality of first baffles 72 extend into their corresponding first grooves 82, which not only facilitates positioning during welding, but also is used to form an S-shaped upper water cooling channel 5; a plurality of second baffles 83 extend into their corresponding second grooves 93, which not only facilitates positioning during welding, but also is used to form an S-shaped lower water cooling channel 6.

[0056] During use: When the temperature of the part where the vibration measuring block is installed on the measured object is high, two layers of water cooling channels are used to cool it down at the same time, which can effectively achieve the cooling effect. That is, the required temperature is first reduced to half through the lower water cooling channel, and then the required temperature is reduced to the required temperature through the upper water cooling channel. At the same time, since the upper and lower water cooling channels are independent structures, the flow rates of the two layers of water can be adjusted separately, which is more flexible to use.

[0057] When the temperature of the part of the measured object where the vibration measuring block is installed is low, only one layer can be used for cooling, which is more convenient and flexible to use and saves the use cost.

[0058] The specific structure provided in the above embodiment is obtained through a series of theoretical analysis, and the specific analysis process is as follows:

[0059] According to the heat calculation formula Q = c*m*ΔT, where c is the specific heat (capacity) of the substance, m is the mass of the substance, ΔT (heat release) = T 末温 -T 初温 ; ΔT(absorption) = T 初温 -T 末温 , in order to maintain the heat balance Q in the initial situation 测振块 =Q 水 Since the vibration measuring block is welded in the high temperature part of the engine, it is an endothermic process. Water takes away the heat by flowing quickly, so the water flow is an exothermic process. Therefore, the cooling and heat dissipation structure design of the vibration measuring block must be carried out according to this formula.

[0060] The vibration block used in the test is made of stainless steel. The initial ambient temperature is 20°C. During the operation of the engine, the temperature of the vibration block at this location is 400°C. The heat calculation formula is as follows:

[0061] Q 测振块 =C 不锈钢 *m 不锈钢 *(400℃-20℃)

[0062] It can be found from materials such as "Heat Transfer" and "Material Handbook" that the specific heat value of stainless steel is: C 不锈钢 =460J / KG*℃, the stainless steel vibration block is 0.12KG, from which the heat value of the vibration block can be calculated as: Q 测振块 =20976J.

[0063] The heat formula of water at this time is: Q 水 =C 水 *m 水 *(400℃-20℃)=20976J. From "Heat Transfer" and "Material Handbook", we can find out that the specific heat of water is: C 水 =4200J / KG*℃, the mass of water is: m 水 =ρ 水 *V 水 =ρ 水 *π*r 2 *v 水流速 *t

[0064] In the above formula, 水 is the density of water; r is the radius of the cooling tube inside the vibration measuring block; υ 水流速 is the flow rate of water in the cooling pipe inside the vibration measuring block; t is the time for water to flow through the cooling pipe inside the vibration measuring block.

[0065] When the water flow time t in the water cooling channel inside the vibration measuring block is set to 1 second, the flow radius r of the water cooling channel inside the vibration measuring block and the flow rate υ of the water in the water cooling channel inside the vibration measuring block are adjusted. 水流速 , the effective size of the vibration measuring block can be designed.

[0066] In order to cool the sensor, a water cooling channel is set on the vibration block. Since the temperature of the high-temperature part of the engine being measured reaches 400°C or even higher, if a water cooling channel is simply opened, the water flow speed must be very fast when the shape and size of the vibration block are fixed, which puts higher requirements on the water supply. In order to further reduce the cost of use and improve the availability and flexibility of the vibration block.

[0067] Therefore, a double-layer water cooling channel is used in the design of the vibration measuring block. This structure has the following advantages:

[0068] 1. The reverse flow of water in and out of the two layers can effectively offset the influence of water flow pulsation on the vibration signal;

[0069] 2. When the temperature of the vibration measuring block is high, the two-layer water-cooling structure can effectively achieve the cooling effect, that is, first reduce the required temperature to half through the bottom layer of water-cooling structure, and then reduce the required temperature to the required temperature through the second layer of water-cooling structure. At the same time, since the upper and lower layers are independent structures, the flow rate of the two layers of water can be adjusted separately, which is more flexible to use.

[0070] 3. When the temperature of the part where the vibration measuring block is installed on the measured object is low, only one layer can be used for cooling, which is convenient and flexible to use.

[0071] In order to ensure the effectiveness of this embodiment, specific verification is carried out through simulation analysis and real experiments as follows:

[0072] 1. Simulation Analysis

[0073] According to the relevant theories of heat transfer, the three-dimensional heat conduction equation of an object is:

[0074]

[0075] Where: T represents temperature; k is the thermal conductivity of the medium, c is the specific heat of the medium, and ρ is the density of the medium.

[0076] According to the above mathematical model, the software simulation geometric model of the piezoelectric sensor device is established using the finite element analysis software ANSYS, and then the mesh is locally divided. The geometric model is then calculated and solved using the solver, and finally the thermal simulation results of the vibration block are obtained, such as Figure 7 As shown in the figure, when the temperature at the bottom of the vibration block reaches 800℃, after the double-layer water cooling, the surface temperature of the vibration block where the sensor body is installed is only 98.259℃. The normal operating range of the sensor body temperature is: -5℃∽120℃. In this way, after double-layer water cooling, the commonly used vibration sensor can be fully used for vibration measurement in high-temperature parts, which also shows the effectiveness of the design.

[0077] 2. Real Test

[0078] In order to verify the design performance of the above-mentioned vibration measuring block, this embodiment also builds a high-temperature performance test system for the vibration measuring block. The vibration measuring block equipped with the piezoelectric sensor is installed in the high-temperature area of ​​the object to be measured. Cooling water is supplied to the vibration measuring block through a tap water pipe. The temperature sensors are respectively installed at the base position of the vibration measuring block (used to measure the actual temperature value of the high-temperature area of ​​the object to be measured, temperature measuring point 2) and the position where the sensor body is installed (used to measure the actual working temperature value of the sensor body. Temperature measuring point 1). The temperature sensor adopts a thermocouple sensor and is fixed to the corresponding position of the vibration measuring block by spot welding. The temperature measurement range of the thermocouple sensor is not less than 1200°C. During the test, the data acquisition system is started to collect data from the two temperature measuring points. The obtained data curve is shown as follows. Figure 8 As shown:

[0079] By obtaining the data curves of the two measuring points, it can be seen that when the temperature of the measured part is 415°C, after double-layer water cooling, the temperature value of the vibration sensor part is 110°C, which meets the actual working temperature range of conventional vibration sensors and meets the design requirements.

[0080] The vibration block was thermally simulated and a special test system was built to test the performance of the vibration block. The test results show that the performance of the vibration block meets the design requirements. The implementation of this design research work can not only solve the problem that the high-temperature parts cannot be measured during the engine test, but also meet the measurement requirements of high-temperature vibration under different temperature conditions by changing the volume and shape of the vibration block based on existing design experience. In this way, the purpose of using normal temperature vibration sensors for high-temperature vibration measurement is achieved, effectively saving the test cost. The vibration block has a simple design structure, is easy to process and batch produce, and is convenient, flexible and reliable to use.

Claims

1. A piezoelectric sensor device suitable for high temperature measurement, comprising a sensor body, characterized in that: It also includes a vibration measuring block for mounting the sensor body on the object to be measured; the sensor body adopts a normal temperature vibration sensor; Two layers of water cooling channels isolated from each other are arranged inside the vibration measuring block, and the water flow directions of the upper water cooling channel and the lower water cooling channel are opposite, and the upper water cooling channel and the lower water cooling channel are both S-shaped; The vibration measuring block comprises a sensor installation part, a middle isolation part and a base part which are arranged in sequence from top to bottom; The sensor mounting portion is provided with a plurality of screw holes for mounting the sensor body; The base part is provided with a mounting hole for docking with the object to be measured; A plurality of first baffles parallel to each other are arranged between the middle isolation part and the sensor installation part, thereby forming an S-shaped upper cooling channel; A plurality of second baffles parallel to each other are arranged between the middle isolation part and the base part, thereby forming an S-shaped lower cooling channel; The plurality of first baffles are arranged on the lower surface of the sensor mounting part, and the upper surface of the middle isolation part is provided with a plurality of first grooves corresponding to the plurality of first baffles one by one, and the lower ends of the first baffles are embedded in the first grooves; The plurality of second baffles are arranged on the upper surface of the base part, and the lower surface of the middle isolation part is provided with a plurality of second grooves corresponding to the plurality of second baffles one by one, and the upper ends of the second baffles are embedded in the second grooves.

2. The piezoelectric sensor device suitable for high temperature measurement according to claim 1, characterized in that: The water flow rates of the upper water cooling channel and the lower water cooling channel are the same.

3. The piezoelectric sensor device suitable for high temperature measurement according to claim 1 or 2, characterized in that: The sensor installation part, the middle isolation part and the base part are connected by welding.

4. The piezoelectric sensor device suitable for high temperature measurement according to claim 3, characterized in that: Three sensor bodies are installed on one vibration measuring block, and the three sensor bodies are arranged orthogonally to each other.

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