CN114814284A - Method and device for measuring cascade flow field by reflection-type mounted ultrasonic array - Google Patents
Method and device for measuring cascade flow field by reflection-type mounted ultrasonic array Download PDFInfo
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Abstract
The invention discloses a method for measuring a cascade flow field by a reflection-type mounted ultrasonic array, which comprises the following steps: step 1, arranging a two-dimensional ultrasonic transducer array right above a plane blade grid channel, transmitting and receiving ultrasonic waves by an ultrasonic measurement system when gas flows through the blade grid channel, and acquiring transit time signal waveforms of the ultrasonic waves in a forward and reverse flow state; and 2, processing the transit time signal waveform by adopting a signal processing method to obtain the transit time of the ultrasonic wave reaching the receiving transducer, and reconstructing a two-dimensional velocity field by the transit time. M multiplied by N ultrasonic transducers are vertically arranged right above the channels of two adjacent blades in the plane blade grid channel, and the matching layers of the ultrasonic transducers are required to be flush with the upper surfaces of the blades. The invention also discloses a device for measuring the cascade flow field by the reflection-type mounted ultrasonic array. The measuring method and the device have simple structure and principle, can realize non-contact on-line measurement, and do not cause interference to a flow field.
Description
Technical Field
The invention relates to the technical field of flow field measurement, in particular to a method and a device for measuring a cascade flow field by a reflection-type mounted ultrasonic array.
Background
The factors influencing the cascade flow field are various and complex, and have geometrical factors: consistency, geometric setting angle, etc., with aerodynamic factors: the mach number of the incoming flow, the interference of a shock wave boundary layer and the like. The air flow in the compressor is diffusion flow, so that flow separation is easy to occur, stall flutter of blades is triggered or the compressor surging is caused, and serious accidents are caused. In the gas turbine, because phenomena such as supercharging acceleration and vortex can be generated among the multi-stage blade grids, the combustion efficiency in a combustion chamber of the gas turbine is influenced, and the performance of the whole gas turbine is further influenced. The key to solve these problems is to master the flow field distribution in the cascade. Therefore, flow field measurement techniques are the basis for understanding cascade performance. The complex flow phenomenon can be known through flow field measurement, the complex physical mechanism of the complex flow phenomenon can be explored, a new flow phenomenon can be established and found for people, and a basis is provided for establishing a new concept and a new physical model.
The existing measurement modes are mainly divided into contact measurement and non-contact measurement. The contact measurement mainly comprises a pressure probe and a pneumatic probe, and is characterized by low cost, high signal-to-noise ratio, single-point measurement and large influence on a flow field. The non-contact measurement is mainly Particle Image Velocimetry (PIV), but tracer particles need to be distributed in a flow field during measurement, the uniformity of the tracer particles cannot be ensured under high-speed airflow, and the tracer particles collide with the wall surface of a flow channel, so that abrasion is caused.
Disclosure of Invention
The present invention is made to solve the above problems, and an object of the present invention is to provide a method and an apparatus for measuring a cascade flow field by using a reflection-type ultrasonic array.
The invention provides a method for measuring a cascade flow field by a reflection-type mounted ultrasonic array, which is characterized by comprising the following steps: step 1, arranging a two-dimensional ultrasonic transducer array right above a plane blade grid channel, transmitting and receiving ultrasonic waves by an ultrasonic measurement system when gas flows through the blade grid channel, and acquiring transit time signal waveforms of the ultrasonic waves in a forward and reverse flow state; and 2, processing the transit time signal waveform by adopting a signal processing method to obtain the transit time of the ultrasonic wave reaching the receiving transducer, and reconstructing a two-dimensional velocity field by the transit time. In step 1, the two-dimensional ultrasonic transducer array includes a plurality of ultrasonic transducers. M multiplied by N ultrasonic transducers are vertically arranged right above the channels of two adjacent blades in the plane blade grid channel, and the matching layers of the ultrasonic transducers are required to be flush with the upper surfaces of the blades.
In the method for measuring the cascade flow field by the reflection-type mounted ultrasonic array, the method can also have the following characteristics: in step 1, the specific values of M and N are determined according to the size of the piezoelectric wafer of the ultrasonic transducer, the frequency of the ultrasonic transducer, and the size of the space between the two blades. When the two-dimensional ultrasonic transducer array is arranged perpendicular to the incoming flow direction, the ultrasonic transducer emits ultrasonic waves within the range of the sound beam angle, and the ultrasonic waves are reflected by the reflecting surface at the root of the cascade and then continuously transmitted to the receiving transducer to be received by the receiving transducer.
In the method for measuring the cascade flow field by the reflection-type mounted ultrasonic array, the method can also have the following characteristics: the size of the sound beam angle alpha is determined by the size of a piezoelectric wafer of the ultrasonic transducer and the frequency of the ultrasonic transducer together:
α/2＝arcsin 1.22λ/D s ＝70λ/D s
wherein λ represents the wavelength of the ultrasonic wave, D S The piezoelectric wafer of the ultrasonic transducer is sized to ensure that the two most distal transducers receive a signal from each other when M and N are determined.
In the method for measuring the cascade flow field by the reflection-type mounted ultrasonic array, the method can also have the following characteristics: wherein, the step 2 specifically comprises the following steps: step 2-1, measuring the temperature of the experimental environment by using a high-precision temperature measuring meter, calculating the sound velocity c in the air at the ambient temperature according to a formula, collecting (M + N) x (M + N-1) groups of static data for multiple times under the working condition that the wind speed is 0 to obtain the time of the ultrasonic wave reaching a receiving transducer,
wherein T represents the ambient temperature of the experiment, T 0 ＝273.16K，c 0 331.45m/s, c represents the sound velocity in air corresponding to the temperature T, and the theoretical propagation time of the ultrasound under the static working condition is as follows:
in the formula, T represents the propagation time of ultrasonic waves, L represents the propagation path of the ultrasonic waves, c represents the actual sound velocity, and the measured time is compared with the theoretical time to obtain a difference so as to eliminate static errors; step 2-2, collecting (M + N) x (M + N-1) group waveform data under the working condition of wind tunnel air supply, and solving the transit time of the ultrasonic wave reaching the receiving transducer; and 2-3, introducing the (M + N) × (M + N-1) effective transit times into a flow field reconstruction program to obtain a two-dimensional velocity field.
In the method for measuring the cascade flow field by the reflection-type mounted ultrasonic array, the method can also have the following characteristics: the specific process of the step 2-2 is as follows: the upstream transducer a transmit signal is received by the downstream transducer B, while the downstream transducer B transmit signal is received by the upstream transducer a. Due to the influence of the flow velocity of the fluid, the transmission time of the ultrasonic waves in the forward and reverse flow is different:
t up ＝L/(c+vcosθ)
t down ＝L/(c-vcosθ)
in the formula, t up The time of the downstream propagation of the ultrasonic wave in the fluid is the time when the ultrasonic wave transmits the ultrasonic wave, and the ultrasonic wave is received by the transducer B; t is t down The time of the ultrasonic wave in the fluid in countercurrent propagation is defined, namely the transducer B transmits the ultrasonic wave, and the transducer A receives the ultrasonic wave; c, ultrasonic propagation speed; l is the distance of the ultrasonic wave in the flow field; theta is ultrasonic wave propagationThe included angle between the path and the axial direction of the fluid; v is the fluid flow rate. The formula of the speed difference method can be obtained from the two formulas as follows:
in the procedure of reconstructing the flow field, the planar cascade two-dimensional flow field is reconstructed based on the formula.
In the method for measuring the cascade flow field by the reflection-type mounted ultrasonic array, the method can also have the following characteristics: wherein, the reconstruction process in the step 2-3 is as follows: the method comprises the steps of calculating an included angle cos theta value between different transducers according to the distance between the transducers and the blade height of a plane blade cascade, constructing a plane grid in a measuring area between two blades, decomposing a velocity value calculated by using a formula into x and y directions, generating a path crossing point in different ultrasonic propagation paths in a blade cascade channel, calculating the velocity at the path crossing point, and finally carrying out Lagrange's method interpolation on the basis of existing velocity data measured between the ultrasonic transducers to meet the measurement resolution of a flow field.
In the method for measuring the cascade flow field by the reflection-type mounted ultrasonic array, the method can also have the following characteristics: in step 2-3, the method for calculating the speed at the sound path intersection point comprises the following steps: if the intersection point of the sound paths is formed by the intersection of the two sound paths, the speed of the point in the x direction is obtained by adding the speeds of the two sound paths in the x direction and then taking the average value, and the speed of the point in the y direction is obtained by adding the speeds of the two sound paths in the y direction and then taking the average value. If the sound path intersection point is formed by intersecting more sound paths, and so on.
The invention provides a device for measuring a cascade flow field by a reflection-type mounted ultrasonic array, which is characterized by comprising the following components: the data generating part is used for arranging a two-dimensional ultrasonic transducer array right above the plane blade cascade channel, and when gas flows through the blade cascade channel, the ultrasonic measuring system transmits and receives ultrasonic waves to obtain the transit time signal waveform of the ultrasonic waves in a forward and reverse flow state; and the data acquisition processing part is used for processing the signal waveform of the transit time by adopting a signal processing method to obtain the transit time of the ultrasonic wave reaching the receiving transducer, and reconstructing a two-dimensional velocity field through the transit time. Wherein, in the data generation section, the two-dimensional ultrasonic transducer array includes a plurality of ultrasonic transducers. M multiplied by N ultrasonic transducers are vertically arranged right above the channels of two adjacent blades in the plane blade grid channel, and the matching layers of the ultrasonic transducers are required to be flush with the upper surfaces of the blades.
Action and effects of the invention
According to the method for measuring the cascade flow field by the reflection-type mounted ultrasonic array, the specific steps are as follows: step 1, arranging a two-dimensional ultrasonic transducer array right above a plane blade grid channel, transmitting and receiving ultrasonic waves by an ultrasonic measurement system when gas flows through the blade grid channel, and acquiring transit time signal waveforms of the ultrasonic waves in a forward and reverse flow state; and 2, processing the transit time signal waveform by adopting a signal processing method to obtain the transit time of the ultrasonic wave reaching the receiving transducer, and reconstructing a two-dimensional velocity field by the transit time. In step 1, the two-dimensional ultrasonic transducer array includes a plurality of ultrasonic transducers. M multiplied by N ultrasonic transducers are vertically arranged right above the channels of two adjacent blades in the plane blade grid channel, and the matching layers of the ultrasonic transducers are required to be flush with the upper surfaces of the blades.
Therefore, the method and the device for measuring the cascade flow field by the reflection-type mounted ultrasonic array have simple structure and principle, can realize non-contact on-line measurement, and do not cause interference to the flow field.
Drawings
FIG. 1 is a flow chart of a method for reflectively mounting an ultrasonic array to measure a cascade flow field in an embodiment of the invention;
FIG. 2 is a schematic diagram of an M N reflective ultrasound array in an embodiment of the present invention;
FIG. 3 is a schematic diagram of the principle of ultrasonic transmission and reception in an embodiment of the present invention;
FIG. 4 is a schematic view of a two-dimensional flow field measurement device in an embodiment of the invention;
FIG. 5 is a schematic view of a 2 × 4 reflective ultrasound array in an embodiment of the present invention;
FIG. 6 is a schematic diagram of the ultrasonic time difference method in accordance with an embodiment of the present invention;
FIG. 7 is a flow chart of flow field reconstruction in an embodiment of the present invention;
FIG. 8 is a flow field reconstruction result under a 10m/s condition in an embodiment of the present invention.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the following embodiments are combined with the accompanying drawings to specifically describe the method and the device for measuring the cascade flow field by the reflection-type mounting ultrasonic array.
In this embodiment, a method of reflectively mounted ultrasonic array measurement of cascade flow fields is provided.
FIG. 1 is a flow chart of a method for reflectively mounting an ultrasonic array to measure a cascade flow field in an embodiment of the invention.
As shown in fig. 1, the method for measuring a cascade flow field by using a reflectively-mounted ultrasonic array according to the present embodiment includes the following steps:
and step S1, arranging a two-dimensional ultrasonic transducer array right above the plane blade cascade channel, when gas flows through the blade cascade channel, transmitting and receiving ultrasonic waves by an ultrasonic measurement system, and acquiring transit time signal waveforms of the ultrasonic waves in a forward and reverse flow state.
Fig. 2 is a schematic diagram of an mxn reflective ultrasound array in an embodiment of the present invention.
As shown in fig. 2, M × N ultrasonic transducers are vertically arranged right above the channels a and b of two adjacent blades in the cascade to form a reflective ultrasonic array c, and the matching layer of the ultrasonic transducers needs to be flush with the upper surface of the blades, so as to avoid the influence on the flow field caused by the installation of the transducers.
And determining specific numerical values of M and N according to the size of a piezoelectric wafer of the transducer, the frequency of the ultrasonic transducer, the size of a space between two blades and the like. When the ultrasonic array is arranged perpendicular to the incoming flow direction, the ultrasonic transducer emits ultrasonic waves in the range of the sound beam angle, and the ultrasonic waves are reflected by the reflecting surface at the root of the blade cascade and then continuously transmitted to the receiving transducer to be received by the receiving transducer. And the size of the sound beam angle alpha is determined by the size of the piezoelectric wafer of the transducer and the frequency of the ultrasonic transducer together:
α/2＝arcsin 1.22λ/D s ＝70λ/D s
in the above formula, λ represents the wavelength of ultrasonic wave, D S The size of the piezoelectric wafer of the ultrasonic transducer is shown. In determining M and N, it is considered that the two most distant transducers can receive signals from each other.
Fig. 3 is a schematic diagram illustrating the principle of transmitting and receiving ultrasonic waves in an embodiment of the present invention.
As shown in fig. 3, the interface of the industrial personal computer includes a human-computer interaction interface, which can visually display the transmitting and receiving oscillograms of the ultrasonic signals. The system operates as follows: firstly, an industrial personal computer is excited to generate an ultrasonic signal; then, the amplitude of the signal can be manually adjusted to a reasonable size according to the waveform condition on the human-computer interaction interface; then, ultrasonic waves are transmitted to a blade cascade channel space through the inverse piezoelectric effect of the ultrasonic transducer to be transmitted, and signals are received through the piezoelectric effect by the receiving transducer. And finally, storing the signal data into an industrial personal computer through an acquisition card. The device system can realize that one transducer transmits signals and the other transducers receive signals, and can quickly and automatically switch the next transmitting transducer after the signals are transmitted and received. The acquisition and storage time to complete a complete set of (M + N) × (M + N-1) signals is short, about 1 s.
Fig. 4 is a schematic view of a two-dimensional flow field measurement device in an embodiment of the invention.
Fig. 5 is a schematic view of a 2 x 4 reflective ultrasound array in an embodiment of the present invention.
As shown in fig. 4, in this embodiment, the two-dimensional flow field measurement apparatus 100 takes 2 × 4 ultrasonic transducers as an example, 2 × 4 ultrasonic transducers 20 are vertically arranged right above two adjacent blade channels in the blade cascade 10, and the matching layer of the ultrasonic transducers needs to be flush with the upper surface of the blade, so as to avoid the influence of the transducer on the flow field, and the specific installation manner is as shown in fig. 5. And then waveform data is collected under the condition of wind supplied by the wind tunnel 30.
And step S2, processing the signal waveform of the transit time by a signal processing method to obtain the transit time of the ultrasonic wave reaching the receiving transducer, and reconstructing a two-dimensional velocity field by the transit time. The method specifically comprises the following steps:
step S2-1, measuring the temperature of the experimental environment by a high-precision temperature measuring meter, calculating the sound velocity c in the air under the environment temperature according to a formula, collecting 7 x 8 groups of static data for a plurality of times under the working condition that the wind speed is 0 to obtain the time when the ultrasonic wave reaches the receiving transducer,
wherein T represents the ambient temperature of the experiment, T 0 ＝273.16K，c 0 331.45m/s, c represents the sound velocity in air corresponding to the temperature T, and the theoretical propagation time of the ultrasound under the static working condition is as follows:
in the formula, T represents the propagation time of ultrasonic waves, L represents the propagation path of the ultrasonic waves, c represents the actual sound velocity, and the measured time is compared with the theoretical time to obtain a difference so as to eliminate static errors.
And step S2-2, collecting 7 multiplied by 8 groups of waveform data under the working condition of wind tunnel air supply, and calculating the transit time of the ultrasonic wave reaching the receiving transducer.
Fig. 6 is a schematic diagram of the principle of the ultrasonic time difference method in the embodiment of the present invention.
As shown in fig. 6, the upstream transducer a transmits a signal that is received by the downstream transducer B, while the downstream transducer B transmits a signal that is received by the upstream transducer a. Due to the influence of the flow velocity of the fluid, the transmission time of the ultrasonic waves in the forward and reverse flow is different:
t up ＝L/(c+vcosθ)
t down ＝L/(c-vcosθ)
in the formula, t up The time of the downstream propagation of the ultrasonic wave in the fluid is the time when the ultrasonic wave transmits the ultrasonic wave, and the ultrasonic wave is received by the transducer B; t is t down Is flowing ultrasonicallyThe time of the countercurrent propagation in the body, namely the ultrasonic wave is transmitted by the transducer B, and the ultrasonic wave is received by the transducer A; c, ultrasonic propagation speed; l is the distance of the ultrasonic wave in the flow field; theta is an included angle between the ultrasonic wave propagation path and the axial direction of the fluid; v is the fluid flow rate. The formula of the speed difference method can be obtained from the two formulas as follows:
compared with the traditional time difference method, the speed obtained by the speed difference method is irrelevant to the temperature, namely the temperature condition in the flow field does not need to be measured. In the procedure of reconstructing the flow field, the planar cascade two-dimensional flow field is reconstructed based on the formula.
And step S2-3, introducing the (M + N) × (M + N-1) effective transit times into a flow field reconstruction program to obtain a two-dimensional velocity field.
And (3) utilizing a time signal flow field reconstruction process: and calculating the value of cos theta of an included angle between different transducers according to the distance between the transducers and the blade height of the planar blade cascade. A plane grid is constructed in a measuring area between two blades, and a speed value calculated by using a formula is decomposed into an x direction and a y direction. In cascade channels, since different ultrasonic propagation paths will produce an intersection point (called the acoustic path intersection point), the way to calculate the velocity at this point is slightly different. If the point is formed by the intersection of two sound paths, the speed of the point in the x direction is obtained by adding the speeds of the two sound paths and then taking the average value, and the speed of the point in the y direction is obtained by adding the speeds of the two sound paths and then taking the average value. If the point is formed by intersecting more sound paths, and so on.
Fig. 7 is a flow chart of flow field reconstruction in an embodiment of the present invention.
As shown in fig. 7, in this embodiment, the flow field reconstruction step includes:
in step S2-3-1, after calculating the basic parameters such as cos θ, L, the speed in the path is calculated by introducing the 56-sound time data.
And step S2-3-2, finding out the sound path cross points between the transducers and judging whether the sound path cross points are in the measuring area, if so, calculating the speed of the point, and if not, rejecting the point.
And S2-3-3, reconstructing a two-dimensional flow field by interpolation according to a Lagrange method.
The x and y direction velocity magnitudes, and vector velocity magnitudes and angle data of the two-dimensional flow field are shown in table 1.
Table 1 shows the flow field reconstruction results under 10m/s conditions, where negative numbers indicate the positive direction of the coordinate axis and positive numbers indicate the positive direction of the coordinate axis.
TABLE 1
FIG. 8 is a flow field reconstruction result under a 10m/s condition in an embodiment of the present invention.
The embodiment also provides a device for measuring the cascade flow field by the reflection-type mounted ultrasonic array.
The device for measuring the cascade flow field by the reflection-type mounted ultrasonic array in the embodiment comprises:
the data generator acquires the transit time signal waveform in the ultrasonic forward/backward flow state by the method of step S1 in the present embodiment.
The data acquisition processing unit reconstructs a two-dimensional velocity field by the method of step S2 in the present embodiment.
Effects and effects of the embodiments
According to the method for measuring the cascade flow field by the reflection-type mounting ultrasonic array, the specific steps are as follows: step 1, arranging a two-dimensional ultrasonic transducer array right above a plane blade grid channel, transmitting and receiving ultrasonic waves by an ultrasonic measurement system when gas flows through the blade grid channel, and acquiring transit time signal waveforms of the ultrasonic waves in a forward and reverse flow state; and 2, processing the transit time signal waveform by adopting a signal processing method to obtain the transit time of the ultrasonic wave reaching the receiving transducer, and reconstructing a two-dimensional velocity field by the transit time. In step 1, the two-dimensional ultrasonic transducer array includes a plurality of ultrasonic transducers. M multiplied by N ultrasonic transducers are vertically arranged right above the channels of two adjacent blades in the plane blade grid channel, and the matching layers of the ultrasonic transducers are required to be flush with the upper surfaces of the blades.
Therefore, the method and the device for measuring the cascade flow field by the reflection-type mounted ultrasonic array have simple structure and principle, can realize non-contact on-line measurement, and do not cause interference to the flow field.
The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.
Claims (8)
1. A method for measuring a cascade flow field by a reflection-type mounted ultrasonic array is characterized by comprising the following steps:
step 1, arranging a two-dimensional ultrasonic transducer array right above a plane blade cascade channel, transmitting and receiving ultrasonic waves by an ultrasonic measurement system when gas flows through the blade cascade channel, and acquiring transit time signal waveforms of the ultrasonic waves in a forward and reverse flow state;
step 2, processing the transit time signal waveform by adopting a signal processing method to obtain the transit time of the ultrasonic wave reaching the receiving transducer, reconstructing a two-dimensional velocity field by the transit time,
wherein, in step 1, the two-dimensional ultrasonic transducer array comprises a plurality of ultrasonic transducers,
and M multiplied by N ultrasonic transducers are vertically arranged right above the channels of two adjacent blades in the plane blade grid channel, and the matching layers of the ultrasonic transducers are flush with the upper surfaces of the blades.
2. The method of reflectively mounting an ultrasonic array measuring a cascade flow field of claim 1, wherein:
wherein, in the step 1, the specific numerical values of M and N are determined according to the size of the piezoelectric wafer of the ultrasonic transducer, the frequency of the ultrasonic transducer and the space size between the two blades,
when the two-dimensional ultrasonic transducer array is arranged perpendicular to the incoming flow direction, the ultrasonic transducer emits the ultrasonic wave within the range of the sound beam angle, and the ultrasonic wave is reflected by the reflecting surface at the root of the cascade and then continuously transmitted to the receiving transducer to be received by the receiving transducer.
3. The method of reflectively mounting an ultrasonic array to measure a cascade flow field of claim 2, wherein:
wherein the size of the beam angle α is determined by the piezoelectric wafer size of the ultrasonic transducer and the ultrasonic transducer frequency:
α/2＝arcsin1.22λ/D s ＝70λ/D s
wherein λ represents the wavelength of the ultrasonic wave, D S The piezoelectric wafer of the ultrasonic transducer is sized to ensure that the two most distal transducers receive a signal from each other when M and N are determined.
4. The method of reflectively mounting an ultrasonic array measuring a cascade flow field of claim 1, wherein:
wherein, the step 2 specifically comprises the following steps:
step 2-1, measuring the temperature of the experimental environment by using a high-precision temperature measuring meter, calculating the sound velocity c in the air at the ambient temperature according to a formula, collecting (M + N) x (M + N-1) groups of static data for multiple times under the working condition that the wind speed is 0 to obtain the time of the ultrasonic wave reaching the receiving transducer,
wherein T represents the ambient temperature of the experiment, T 0 ＝273.16K，c 0 331.45m/s, c represents the sound velocity in air corresponding to the temperature T, and the theoretical propagation time of the ultrasound under the static working condition is as follows:
in the formula, T represents the propagation time of ultrasonic waves, L represents the propagation path of the ultrasonic waves, c represents the actual sound velocity, and the measured time is compared with the theoretical time to obtain a difference so as to eliminate static errors;
step 2-2, collecting (M + N) x (M + N-1) group waveform data under the working condition of wind tunnel air supply, and solving the transit time of the ultrasonic wave reaching the receiving transducer;
and 2-3, introducing (M + N) x (M + N-1) effective transit times into a flow field reconstruction program to obtain the two-dimensional velocity field.
5. The method of reflectively mounting an ultrasonic array to measure a cascade flow field of claim 4, wherein:
the specific process of the step 2-2 is as follows:
the upstream transducer a transmits a signal that is received by the downstream transducer B, while the downstream transducer B transmits a signal that is received by the upstream transducer a,
due to the influence of the flow velocity of the fluid, the transmission time of the ultrasonic waves in the forward and reverse flow is different:
t up ＝L/(c+vcosθ)
t down ＝L/(c-vcosθ)
in the formula, t up The time of the downstream propagation of the ultrasonic wave in the fluid is the time when the ultrasonic wave transmits the ultrasonic wave, and the ultrasonic wave is received by the transducer B; t is t down The time of the ultrasonic wave in the fluid in countercurrent propagation is defined, namely the transducer B transmits the ultrasonic wave, and the transducer A receives the ultrasonic wave; c, ultrasonic propagation speed; l is the distance of the ultrasonic wave in the flow field; theta is an included angle between the ultrasonic propagation path and the axial direction of the fluid; v is the flow rate of the fluid and,
the formula of the speed difference method can be obtained from the two formulas as follows:
in the procedure of reconstructing the flow field, the planar cascade two-dimensional flow field is reconstructed based on the formula.
6. The method of reflectively mounting an ultrasonic array to measure a cascade flow field of claim 4, wherein:
wherein, the reconstruction process in the step 2-3 is as follows:
calculating an included angle cos theta value between different transducers according to the distance between the transducers and the blade height of the planar blade cascade, constructing a planar grid in a measurement area between two blades, decomposing a velocity value calculated by using a formula into x and y directions, generating a path intersection point in different ultrasonic propagation paths in a blade cascade channel, calculating the velocity at the path intersection point, and finally performing Lagrange's method interpolation on the basis of existing velocity data measured between the ultrasonic transducers to meet the measurement resolution of a flow field.
7. The method of reflectively mounting an ultrasonic array to measure a cascade flow field of claim 6, wherein:
in step 2-3, the method for calculating the speed at the sound path intersection point comprises the following steps:
if the intersection point of the sound paths is formed by the intersection of two sound paths, the speed of the point in the x direction is obtained by adding the speeds of the two sound paths in the x direction and then taking the average value, the speed of the point in the y direction is obtained by adding the speeds of the two sound paths in the y direction and then taking the average value,
if the sound path intersection point is formed by intersecting more sound paths, and so on.
8. A reflectively mounted ultrasonic array apparatus for measuring a cascade flow field, comprising:
the data generating part is used for arranging a two-dimensional ultrasonic transducer array right above the plane blade cascade channel, and when gas flows through the blade cascade channel, the ultrasonic measuring system transmits and receives ultrasonic waves to obtain the transit time signal waveform of the ultrasonic waves in a forward and reverse flow state;
a data acquisition processing part which processes the signal waveform of the transit time by adopting a signal processing method to obtain the transit time of the ultrasonic wave reaching the receiving transducer and reconstructs a two-dimensional velocity field by the transit time,
wherein, in the data generation section, the two-dimensional ultrasonic transducer array includes a plurality of ultrasonic transducers,
and M multiplied by N ultrasonic transducers are vertically arranged right above the channels of two adjacent blades in the plane blade grid channel, and the matching layers of the ultrasonic transducers are flush with the upper surfaces of the blades.
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| Publication number | Priority date | Publication date | Assignee | Title |
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