Rotational flow speed calibration device and method

Abstract

The invention discloses a rotational flow speed calibration device and method, and belongs to the field of aero-engine air systems. The method comprises the following steps: constructing a rotational flow speed calibration device; arranging measuring points; a probe for measuring a static characteristic index is arranged at the outlet section, and a calibration probe for measuring a dynamic characteristic index is arranged on the downstream of the outlet section along the axial direction of airflow in a windward manner; setting a deflection angle change range of the calibration probe; determining a speed relative error as an evaluation index of a rotational flow speed calibration result; setting a flow field to carry out a calibration test, and determining a calibration probe deflection angle range generating a speed relative error; and fitting based on a relational graph of the velocity coefficient and the deflection angle of the calibration probe to obtain a velocity coefficient correction formula for eliminating a measurement error, thereby completing calibration. According to the invention, the problem of large deviation in rotational flow speed measurement in the prior art is solved.

Description

Technical Field

[0001] The invention belongs to the field of aviation engine air systems, and in particular relates to a swirl velocity calibration device and method. Background Art

[0002] In aircraft engines and gas turbines, the air system is an indispensable part, which can ensure the normal operation of the engine in any working state. There are a large number of rotor-static interfaces in the engine air system, so the sealing device is an indispensable part of the gas turbine engine air system.

[0003] The grate seal at the compressor can reduce the pressure loss caused by high-pressure gas leakage to ensure the compression efficiency of the compressor; the grate seal at the turbine can prevent the mainstream gas from invading the disc cavity, thereby ensuring that the turbine disc, bearings and other components can work stably. At the same time, the grate seal at the turbine can also reduce the energy loss of the gas and ensure the work efficiency of the turbine.

[0004] The main function of the grate seal is to reduce the amount of gas leakage. At present, the focus of the study of the grate seal is mainly on the leakage characteristics. In recent years, with the advancement of industrial level, the high pursuit of engine performance has made the research on the grate seal more in-depth. The airflow in the engine air system will be subjected to a large shear force due to the existence of the rotor-static interface, resulting in a significant increase in the swirl and wind resistance temperature rise of the airflow in the grate flow channel. In the turbine disc pre-swirl system, the size of the swirl will affect the cooling airflow flow provided by the pre-swirl system to the turbine blades. Therefore, with the requirements for high safety and reliability of the engine, it is of great significance to systematically study the swirl characteristics of the grate. To study the swirl characteristics of the grate, it is inevitable to measure the swirl velocity in the experiment. In other words, accurately obtaining the grate swirl velocity is of great significance to the design of the aircraft engine air system.

[0005] In the prior art, the method for measuring swirl velocity is usually to indirectly calculate the airflow velocity by measuring the total temperature, total pressure and static pressure of the airflow. However, due to the deviation in the direction of the airflow velocity, the measured total pressure also has a deviation. Therefore, the swirl velocity measured by the traditional method has a large deviation, and there is still a lack of a more accurate calibration method. Summary of the invention

[0006] Technical issues to be solved:

[0007] In order to avoid the shortcomings of the prior art, the present invention provides a swirl velocity calibration device and method. Based on the calibration device, experiments are conducted to measure the static characteristic index of the device. Combined with the deflection angle adjustability of the calibration probe, the directional total pressure at different deflection angles is measured, and the velocity separation after the deflection angle is calculated, thereby obtaining the relative error between the theoretical value velocity and the measured velocity at the same deflection angle as an evaluation index for the swirl velocity calibration result. The deflection angle of the calibration probe is adjusted to obtain the relative velocity error corresponding to each deflection angle, and the probe deflection angle range that produces the relative velocity error is obtained. The velocity coefficient within the range is corrected to eliminate the error, thereby obtaining accurate measurement accuracy. The present invention solves the problem of large deviations in swirl velocity measurement in the prior art.

[0008] The technical solution of the present invention is: a swirl velocity calibration method, the specific steps are as follows:

[0009] Constructing a swirl velocity calibration device; the calibration device is a wind tunnel capable of measuring static characteristic indicators of airflow at the outlet section;

[0010] Arrange measurement points; arrange a probe for measuring static characteristic indicators at the outlet section, and arrange a calibration probe for measuring dynamic characteristic indicators downstream of the outlet section and along the airflow axis;

[0011] Set the deflection angle variation range of the calibration probe;

[0012] Determine the velocity relative error as an evaluation index of the swirl velocity calibration result;

[0013] Set up a flow field for calibration test to determine the range of calibration probe deflection angles that produce relative velocity error;

[0014] The velocity coefficient correction formula is obtained based on the relationship diagram between the velocity coefficient and the deflection angle of the calibration probe to eliminate the measurement error, thus completing the calibration.

[0015] A further technical solution of the present invention is: the outlet section of the swirl velocity calibration device is successively composed of a contraction section and a straight section along the airflow direction, and a plurality of radially arranged probes are evenly distributed in the circumferential direction near the inlet end of the contraction section, which are used to measure the total temperature and total pressure of the airflow at the inlet of the contraction section; a plurality of probes parallel to the axial direction are evenly distributed in the circumferential direction near the outlet end of the straight section, which are used to measure the static pressure of the airflow at the outlet of the contraction section.

[0016] A further technical solution of the present invention is: the calibration probe is mounted on a coordinate frame via a dividing plate, the x, y, z axial positions of the calibration probe are adjusted via the coordinate frame, and the deflection angle of the calibration probe is adjusted via the dividing plate.

[0017] A further technical solution of the present invention is: the calculation formula of the speed relative error is as follows:

[0018]

[0019] Where V θ It represents the measured velocity component in this direction after the calibration probe is deflected by angle θ, V θ ′ represents the theoretical velocity after the calibration probe is deflected by an angle of θ; V θ ′=V0·cosθ, V0 represents the axial air flow velocity at the outlet of the contraction section.

[0020] A further technical solution of the present invention is: the calculation formula of the axial air flow velocity V0 at the outlet of the contraction section is as follows:

[0021]

[0022] In the formula, is the total airflow pressure at the inlet of the contraction section / Pa; P2 is the static airflow pressure at the outlet of the contraction section / Pa; is the total temperature of the airflow at the inlet of the contraction section / K; κ is the constant entropy index; R g is the gas constant / J·(kg·K) -1 .

[0023] A further technical solution of the present invention is: the method for determining the deflection angle range of the calibration probe that produces the speed relative error is to perform a calibration test with a set deflection angle step within the deflection angle variation range of the calibration probe; record the characteristic indicators measured at each deflection angle, and calculate the speed relative error at each deflection angle, establish a deflection angle-speed relative error relationship diagram, and obtain from the diagram the deflection angle range in which the speed relative error increases approximately linearly with the change in the deflection angle of the calibration probe, that is, obtain the deflection angle range of the calibration probe that produces the speed relative error.

[0024] A further technical solution of the present invention is that the deflection angle range of the calibration probe that produces the relative speed error is 8° to 24°.

[0025] A further technical solution of the present invention is: the method for obtaining the speed coefficient correction formula is:

[0026] Define the speed coefficient ζ as:

[0027]

[0028] Calculate the velocity coefficient of the calibration probe at each deflection angle and establish a deflection angle-velocity coefficient relationship diagram;

[0029] The speed coefficient correction formula is obtained by fitting the deflection angle-speed coefficient curve.

[0030] A swirl velocity calibration device comprises an inlet section, a diffusion section, a rectifying section, a steady flow section and an outlet section which are sequentially connected along the flow direction of an airflow; a perforated plate, a honeycomb and a damping net are sequentially arranged in the rectifying section along the flow direction of the airflow, respectively used to rectify the airflow so that the airflow can enter the contraction section uniformly; the steady flow section allows the airflow to have enough time to decay small vortices in the airflow after passing through the damping net; the outlet section comprises a contraction section and a straight section sequentially arranged along the flow direction of the airflow, the contraction section adopts a Vickers curve as a profile curve to ensure uniform velocity distribution of the airflow in the outlet section; a calibration probe with an adjustable deflection angle is arranged at the outlet of the outlet section and along the airflow axis to face the wind.

[0031] An application of a swirl velocity calibration method, the specific steps are as follows:

[0032] Two swirl measuring points are arranged at the grate inlet, and total pressure probes are arranged to measure the axial total pressure and circumferential total pressure of the airflow at the grate inlet respectively;

[0033] The velocity component of the grate inlet airflow velocity in the probe installation direction is calculated based on the measurement values ​​of the two total pressure probes. The formula is as follows:

[0034]

[0035] Where P 轴 It represents the total pressure of the airflow measured by the first total pressure probe which is biased toward the axial direction of the grate disc, P 周 represents the total pressure of the airflow measured by the second total pressure probe biased in the radial direction of the grate disc, P represents the static pressure of the airflow, ρ represents the airflow density, V1 represents the velocity component of the airflow velocity at the grate inlet in the direction of the first total pressure probe, and V2 represents the velocity component of the airflow velocity at the grate inlet in the direction of the second total pressure probe;

[0036] The component velocity is corrected based on the velocity coefficient, and then the velocity V of the airflow at the grate inlet is calculated, and the formula is as follows:

[0037] ζ(θ-θ1)V1=V·cos(θ-θ1)

[0038] ζ(90-θ-θ2)V2=V·cos(90-θ-θ2)

[0039] Wherein, θ1 represents the angle between the first total pressure probe and the axial direction of the grate disc, θ2 represents the angle between the second total pressure probe and the radial direction of the grate disc, and θ represents the angle between the velocity of the grate inlet airflow and the axial direction of the grate disc;

[0040] Calculate the total axial pressure of the airflow at the grate inlet and circumferential total pressure The formula is as follows:

[0041]

[0042] Beneficial Effects

[0043] The beneficial effects of the present invention are as follows: the present invention proposes a swirl velocity calibration device and method, which can calibrate the measurement results of the swirl velocity in a complex rotation experiment under static conditions. The calibration experiment is carried out on the swirl velocity calibration device under static conditions to obtain the variation law of the velocity coefficient with the probe deflection angle under different flow fields. There is no problem of sealing between the rotating and static parts, and there is no need to measure the leakage flow, which greatly improves the accuracy of the calibration. At the same time, since the calibration is carried out under static conditions, there is no need to calibrate the swirl velocity under rotation conditions, which greatly reduces the cost of calibration. Rotation experiments involve problems such as vibration, and the risk factor of the experiment is very high, and safety accidents are prone to occur. Calibration under static conditions greatly improves the safety of the calibration experiment.

[0044] The calibration method of the present invention has a relatively mature theoretical support, the calibration result is accurate and reliable, and can greatly improve the measurement accuracy of the swirl velocity. When the probe deflection angle is within a certain range, the relative error of the velocity increases approximately linearly with the change of the probe deflection angle. Based on this, the velocity coefficient is introduced to calibrate and correct the swirl velocity. After correction, the relative error of the swirl velocity measurement is less than 0.3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of the structure of a swirl velocity calibration device in an embodiment of the present invention;

[0046] Figure 2 A schematic diagram of the arrangement of measuring points of a calibration device in an embodiment of the present invention;

[0047] Figure 3 The swirl velocity calibration result in the embodiment of the present invention;

[0048] Figure 4 Schematic diagram of the decomposition of the swirl velocity at the grate inlet in an embodiment of the present invention;

[0049] Figure 5 Schematic diagram of the variation of the relative speed deviation with the deflection angle of the calibration probe in an embodiment of the present invention;

[0050] Figure 6 Schematic diagram of the variation of the velocity coefficient with the deflection angle of the calibration probe in an embodiment of the present invention;

[0051] Explanation of the reference numerals: 1. Inlet section, 2. Diffusion section, 3. Orifice plate, 4. Honeycomb, 5. Damping net, 6. Contraction section, 7. Straight section, 8. Calibration probe, 9. First section, 10. Second section, 11. First total pressure probe, 12. Second total pressure probe. DETAILED DESCRIPTION

[0052] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0053] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0054] Based on the existing method of measuring swirl velocity, the velocity of the airflow is usually calculated indirectly by measuring the total temperature, total pressure and static pressure of the airflow. Due to the deviation of the velocity direction of the airflow, the total pressure measured also has the problem of deviation. The present invention provides a swirl velocity calibration device, referring to Figure 1 As shown, it includes an inlet section, a diffusion section, a rectifying section, a steady flow section and an outlet section connected in sequence along the flow direction of the airflow; the diffusion angle of the diffuser section is 10°; the rectifying section is sequentially provided with a perforated plate, a honeycomb and a damping net along the flow direction of the airflow, and a perforated plate is installed at the outlet of the diffuser section to reduce the separation of the airflow from the diffuser section wall by increasing the flow resistance of the airflow; the airflow is rectified by installing a honeycomb and a damping net so that the airflow can enter the contraction section uniformly. The part from the damping net to the inlet of the contraction section is called the steady flow section, and the function of the steady flow section is to ensure that the airflow has enough time to attenuate the small vortex in the airflow after passing through the damping net. In addition, the damping net can also play a role in filtering impurities in the gas to prevent clogging of the total pressure probe to be measured. The outlet section includes a contraction section and a straight section sequentially arranged along the flow direction of the airflow, and the Vickers curve is used as the profile curve of the contraction section to ensure that the velocity distribution of the airflow in the outlet section is more uniform. At the outlet of the outlet section, a calibration probe with an adjustable deflection angle is arranged along the airflow axis to face the wind.

[0055] The present invention provides a swirl velocity calibration method, the specific steps are as follows:

[0056] Step 1: construct a swirl velocity calibration device;

[0057] Step 2: Arrange measurement points; arrange a probe for measuring static characteristic indicators at the outlet section, and arrange a calibration probe for measuring dynamic characteristic indicators downstream of the outlet section and along the airflow axis;

[0058] Multiple radially arranged probes are evenly distributed circumferentially near the inlet end of the contraction section for measuring the total temperature and pressure of the airflow at the inlet of the contraction section; multiple probes parallel to the axial direction are evenly distributed circumferentially near the outlet end of the straight section for measuring the static pressure of the airflow at the outlet of the contraction section.

[0059] The calibration probe is mounted on a coordinate frame via a dividing plate, the x, y, z axial positions of the calibration probe are adjusted via the coordinate frame, and the deflection angle of the calibration probe is adjusted via the dividing plate.

[0060] Step 3: Set the deflection angle range of the calibration probe;

[0061] Step 4: Determine the speed relative error as an evaluation index of the swirl speed calibration result; the calculation formula of the speed relative error is as follows:

[0062]

[0063] Where V θ It represents the measured velocity component in this direction after the calibration probe is deflected by angle θ, V θ ′ represents the theoretical velocity after the calibration probe is deflected by an angle of θ; V θ ′=V0·cosθ, V0 represents the axial air flow velocity at the outlet of the contraction section, and the calculation formula is as follows:

[0064]

[0065] In the formula, is the total airflow pressure at the inlet of the contraction section / Pa; P2 is the static airflow pressure at the outlet of the contraction section / Pa; is the total temperature of the airflow at the inlet of the contraction section / K; κ is the constant entropy index; R g is the gas constant / J·(kg·K) -1 .

[0066] Step 5: Set up the flow field for calibration test to determine the deflection angle range of the calibration probe that produces relative velocity error;

[0067] Within the deflection angle variation range of the calibration probe, the calibration test is performed with the set deflection angle step; the characteristic indicators measured at each deflection angle are recorded, and the relative speed error at each deflection angle is calculated, and the relationship diagram between the deflection angle and the relative speed error is established (such as Figure 5 As shown in the figure, the deflection angle range in which the velocity relative error increases approximately linearly with the change of the deflection angle of the calibration probe is obtained, that is, the deflection angle range of the calibration probe that produces the velocity relative error is obtained.

[0068] In order to ensure that the experimental results can be applied to the swirl velocity calibration at the grate inlet, it is necessary to ensure that the flow field during the calibration experiment is the same as the grate inlet flow field. Through numerical simulation, it is known that when the design gap C′0=0.8mm, the Mach number of the airflow at the grate inlet is Ma=0.15, so the flow field of this calibration experiment is set to Ma=0.15. Figure 3 It can be seen that when the deflection angle between the probe and the airflow is between 0° and 8°, the relative error of the velocity changes with the change of the probe deflection angle by less than 1%. This is because the deflection angle between the probe and the airflow is too small, resulting in the insensitivity of the airflow to the probe deflection angle. When the probe deflection angle is between 8° and 24°, the relative error of the velocity increases approximately linearly with the change of the probe deflection angle, so the velocity measurement value within this range is corrected.

[0069] Step 6: Based on the relationship diagram between the velocity coefficient and the deflection angle of the calibration probe, a velocity coefficient correction formula is obtained to eliminate the measurement error, thus completing the calibration.

[0070] The method for obtaining the speed coefficient correction formula is:

[0071] Step 6.1: Define the velocity coefficient ζ as:

[0072]

[0073] Step 6.2: Calculate the velocity coefficient of the calibration probe at each deflection angle and establish a deflection angle-velocity coefficient relationship diagram (such as Figure 6 shown);

[0074] Step 6.3: Fit the deflection angle-speed coefficient curve to obtain the speed coefficient correction formula.

[0075] Reference Figure 3 The variation of velocity coefficient with the deflection angle of the probe is given. By correcting the velocity coefficient, the relative error of velocity measurement can be made less than 0.3%. In the same way, the flow fields of Ma=0.10, 0.20, 0.30, and 0.40 are calibrated, and the correction formulas of velocity coefficient are obtained as ζ=-0.001θ+1.0251, ζ=-0.0012θ+1.0055, ζ=-0.0015θ+1.0088, and ζ=-0.0015θ+1.009.

[0076] The present invention provides an application of a swirl velocity calibration method. The swirl velocity measurement error increases with the increase of the deflection angle between the total pressure probe and the airflow, and the velocity coefficient is used to correct the measurement result of the total pressure probe within the deflection angle range of 8° to 24°. When arranging the swirl measurement point at the comb tooth inlet, it is necessary to ensure that the deflection angle between the total pressure probe and the airflow is within the range of 8° to 24° before the velocity coefficient obtained by the wind tunnel calibration experiment can be applied. The specific steps are as follows:

[0077] Step 1: Arrange two swirl measuring points at the grate inlet, and arrange total pressure probes for measuring the axial total pressure and circumferential total pressure of the airflow at the grate inlet respectively;

[0078] Reference Figure 4 The figure shows the schematic diagram of the decomposition of the swirl velocity at the grate inlet. Assume that the velocity of the grate inlet airflow is V, and the angle between it and the axial direction of the grate disc is θ. The axial total pressure and circumferential total pressure of the grate inlet airflow are obtained by arranging two total pressure probes, where the angle between the first total pressure probe and the axial direction of the grate disc is θ1, and its measured value is P 轴 The angle between the second total pressure probe and the circumferential direction of the comb disc is θ2, and its measured value is P 周 .

[0079] Step 2: Calculate the velocity component of the grate inlet airflow velocity in the probe installation direction based on the measurement values ​​of the two total pressure probes. The formula is as follows:

[0080]

[0081] Where P 轴 It represents the total pressure of the airflow measured by the first total pressure probe which is biased toward the axial direction of the grate disc, P 周 represents the total pressure of the airflow measured by the second total pressure probe biased in the radial direction of the grate disc, P represents the static pressure of the airflow, ρ represents the airflow density, V1 represents the velocity component of the airflow velocity at the grate inlet in the direction of the first total pressure probe, and V2 represents the velocity component of the airflow velocity at the grate inlet in the direction of the second total pressure probe;

[0082] Step 3: According to Figure 4 The known angles can be obtained. The angle between the first total pressure probe and the incoming flow direction is (θ-θ1), and the angle between the second probe and the incoming flow direction is (90-θ-θ2). After substituting the total pressure probe measurement values ​​into equations (4) and (5), the velocities V1 and V2 of the airflow in the directions where the No. 1 and No. 2 total pressure probes are placed can be obtained. There is an error between the velocities V1 and V2 measured by the total pressure probes and the velocity component of the incoming flow V in this direction. The measurement error can be reduced by introducing the velocity coefficient ζ to correct V1 and V2. Therefore, after the velocity coefficient correction and the application of the velocity decomposition principle, the relationship between V1, V2 and velocity V can be obtained as follows:

[0083] ζ(θ-θ1)V1=V·cos(θ-θ1)(6)

[0084] ζ(90-θ-θ2)V2=V·cos(90-θ-θ2)(7)

[0085] Wherein, θ1 represents the angle between the first total pressure probe and the axial direction of the grate disc, θ2 represents the angle between the second total pressure probe and the radial direction of the grate disc, and θ represents the angle between the velocity of the grate inlet airflow and the axial direction of the grate disc;

[0086] Step 4: The velocity magnitude V and direction θ of the incoming flow can be obtained from equations (6) and (7). The velocity magnitudes of the airflow in the axial direction and the circumferential direction are obtained by the orthogonal decomposition principle as V·cosθ and V·sinθ, respectively. Therefore, the axial total pressure and circumferential total pressure of the incoming flow can be obtained by the Bernoulli equation as follows:

[0087]

[0088]

[0089] The above technical solution is further described below with reference to the accompanying drawings and examples:

[0090] This embodiment uses a swirl velocity calibration device and method to calibrate a flow field with an airflow Mach number Ma=0.2, including the following steps:

[0091] Step 1: Calibration device installation;

[0092] Swirl velocity calibration device, refer to Figure 1 As shown, the device is a small wind tunnel, including an inlet section, a diffuser section, a straightening section, a flow stabilization section and an outlet section which are arranged in sequence along the axial direction.

[0093] Step 2, measurement point arrangement;

[0094] Reference Figure 2 The schematic diagram of the measurement point arrangement of the swirl velocity calibration device shows that 3 total temperature measurement points and 4 total pressure measurement points are evenly arranged at different circumferential positions of the first radial section near the inlet of the contraction section, respectively, for measuring the total temperature and total pressure of the airflow at the inlet of the contraction section. 4 static pressure measurement points are evenly arranged at different circumferential positions of the second radial section near the outlet of the straight section, for measuring the static pressure of the airflow at the outlet of the contraction section.

[0095] The pressure and temperature parameters are collected by pressure scanning valve, thermocouple and temperature scanning valve respectively. When calibrating, the probe to be measured needs to be able to rotate and move within a certain range, so the calibration probe is installed on the dividing plate and coordinate frame. The coordinate frame can realize the three-dimensional movement of the probe to be measured, and the travel in the x, y and z directions is 100mm, 110mm and 100mm respectively. The coordinate frame adopts double scale reading, the minimum reading of the coordinate scale is 0.1mm, and a double locking device is adopted. This structure can enhance the stability of the calibration probe during movement. The dividing plate can achieve 360° rotation, and its minimum scale is 1°.

[0096] Step 3, conduct calibration experiment;

[0097] The probe deflection angle variation range of this calibration experiment is set to 0°~40°. At the same time, in order to reduce the influence of random errors on the experimental results, the experimental data are recorded every 2° during the experiment. The experimental data are shown in Table 1 below.

[0098] Table 1 Experimental data of swirl velocity calibration at Ma = 0.2

[0099]

[0100]

[0101] Calculate the velocity V measured by the total pressure probe θ and theoretical speed V θ ′, the calculation results are shown in Table 2 below.

[0102]

[0103]

[0104] Step 4, fitting the correction formula of the speed coefficient;

[0105] Reference Figure 5 The variation law of the speed relative deviation with the probe deflection angle shows that the speed relative deviation increases first and then decreases with the increase of the probe deflection angle. In the deflection angle range of 8° to 28°, the speed relative deviation increases approximately linearly with the change of the probe deflection angle, and the maximum deviation is 2.77%. The speed measurement value within this range is corrected.

[0106] In the range of deflection angle of 8° to 28°, the least square method is used to fit the variation trend of the velocity coefficient with the deflection angle, as shown in the figure below, and the correction formula of the velocity coefficient is ζ = -0.0012θ + 1.0055.

[0107] Step 5, using a new method to arrange the measuring points for measurement;

[0108] Reference Figure 4 The figure shows the decomposition diagram of the swirl velocity at the grate inlet. Assume that the velocity of the grate inlet airflow is V, and the angle between it and the axial direction of the grate disc is θ. The axial total pressure and circumferential total pressure of the grate inlet airflow are obtained by arranging two total pressure probes, where the angle between the first total pressure probe and the axial direction of the grate disc is θ1 = 9°, and its measured value is The angle between the second total pressure probe and the circumferential direction of the comb disc is θ2 = 27°, and its measured value is

[0109] The velocity of the airflow at the grate inlet is very small (Ma<0.3), so the total pressure and static pressure of the airflow satisfy the Bernoulli equation:

[0110]

[0111]

[0112] According to the static pressure and temperature measurement results at the comb inlet: P = 175.05 kpa, T = 298.14 K, it can be calculated according to formulas (1) and (2) that V1 = 65.21 m / s, V2 = 64.46 m / s.

[0113] Step 6, introducing a speed coefficient to correct the swirl speed;

[0114] according to Figure 4 The known angles can be obtained. The angle between the No. 1 total pressure probe and the incoming flow direction is (θ-θ1), and the angle between the No. 2 probe and the incoming flow direction is (90-θ-θ2). There is an error between the velocities V1 and V2 measured by the total pressure probe and the velocity component of the incoming flow V in this direction. By introducing the velocity coefficient ζ to correct V1 and V2, the measurement error can be reduced. Therefore, after the velocity coefficient correction and the application of the velocity decomposition principle, the relationship between V1, V2 and velocity V can be obtained as follows:

[0115] ζ(θ-θ1)V1=V·cos(θ-θ1)(3)

[0116] ζ(90-θ-θ2)V2=V·cos(90-θ-θ2)(4)

[0117] Solving the above equations yields V = 70.80 m / s, θ = 35.24°.

[0118] according to Figure 4 By decomposing the swirl velocity, we can obtain the axial velocity and circumferential velocity of the swirl at the grate inlet:

[0119] V x =V·cosθ=70.80×cos35.24°=57.82 (5)

[0120] V y =V·sinθ=70.80×sin35.24°=40.85 (6)

[0121] After calibration by the device and method of the present invention, the measurement error of the swirl velocity can be reduced to less than 0.3%.

[0122] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for calibrating swirl velocity, characterized in that The specific steps are as follows: Constructing a swirl velocity calibration device; the calibration device is a wind tunnel capable of measuring static characteristic indicators of airflow at the outlet section; Arrange measurement points; arrange a probe for measuring static characteristic indicators at the outlet section, and arrange a calibration probe for measuring dynamic characteristic indicators downstream of the outlet section and along the airflow axis; Set the deflection angle variation range of the calibration probe; Determine the velocity relative error as an evaluation index of the swirl velocity calibration result; Set up a flow field for calibration test to determine the range of calibration probe deflection angles that produce relative velocity error; The velocity coefficient correction formula is obtained based on the relationship diagram between the velocity coefficient and the deflection angle of the calibration probe to eliminate the measurement error, thus completing the calibration.

2. A swirl velocity calibration method according to claim 1, characterized in that: The outlet section of the swirl velocity calibration device is composed of a contraction section and a straight section in sequence along the airflow direction. A plurality of radially arranged probes are evenly distributed in the circumferential direction near the inlet end of the contraction section, which are used to measure the total temperature and pressure of the airflow at the inlet of the contraction section; a plurality of probes parallel to the axial direction are evenly distributed in the circumferential direction near the outlet end of the straight section, which are used to measure the static pressure of the airflow at the outlet of the contraction section.

3. A swirl velocity calibration method according to claim 1, characterized in that: The calibration probe is mounted on a coordinate frame via a dividing plate, the x, y, z axial positions of the calibration probe are adjusted via the coordinate frame, and the deflection angle of the calibration probe is adjusted via the dividing plate.

4. A swirl velocity calibration method according to claim 1, characterized in that: The calculation formula of the speed relative error is as follows: Where V θ It represents the measured velocity component in this direction after the calibration probe is deflected by angle θ, V θ ′ represents the theoretical velocity after the calibration probe is deflected by an angle of θ; V θ ′=V0·cosθ, V0 represents the axial air flow velocity at the outlet of the contraction section.

5. A swirl velocity calibration method according to claim 4, characterized in that: The calculation formula of the axial air flow velocity V0 at the outlet of the contraction section is as follows: Where P1 * is the total airflow pressure at the inlet of the contraction section / Pa; P2 is the static airflow pressure at the outlet of the contraction section / Pa; T1 * is the total temperature of the airflow at the inlet of the contraction section / K; κ is the constant entropy index; R g is the gas constant / J·(kg·K) -1 .

6. A swirl velocity calibration method according to claim 5, characterized in that: The method for determining the deflection angle range of the calibration probe that produces the relative speed error is to perform a calibration test with a set deflection angle step within the deflection angle variation range of the calibration probe; The characteristic indicators measured at each deflection angle are recorded, and the speed relative error at each deflection angle is calculated. A deflection angle-speed relative error relationship diagram is established. From the diagram, the deflection angle range in which the speed relative error increases approximately linearly with the change of the deflection angle of the calibration probe is obtained, that is, the deflection angle range of the calibration probe that produces the speed relative error is obtained.

7. A swirl velocity calibration method according to claim 6, characterized in that: The deflection angle range of the calibration probe that produces the relative speed error is 8° to 24°.

8. A swirl velocity calibration method according to claim 6, characterized in that: The method for obtaining the speed coefficient correction formula is: Define the speed coefficient ζ as: Calculate the velocity coefficient of the calibration probe at each deflection angle and establish a deflection angle-velocity coefficient relationship diagram; The speed coefficient correction formula is obtained by fitting the deflection angle-speed coefficient curve.

9. A swirl velocity calibration device, characterized in that: Used to implement the swirl velocity calibration method described in any one of claims 1 to 8; comprising an inlet section, a diffusion section, a rectifying section, a steady flow section and an outlet section connected in sequence along the airflow direction; a perforated plate, a honeycomb and a damping net are arranged in sequence in the rectifying section along the airflow direction, respectively used to rectify the airflow so that the airflow can enter the contraction section evenly; the steady flow section allows the airflow to have enough time to decay small vortices in the airflow after passing through the damping net; the outlet section comprises a contraction section and a straight section arranged in sequence along the airflow direction, the contraction section adopts a Vickers curve as a profile curve to ensure uniform velocity distribution of the airflow in the outlet section; a calibration probe with an adjustable deflection angle is arranged at the outlet of the outlet section and along the airflow axis to face the wind.

10. An application of the swirl velocity calibration method according to any one of claims 1 to 8, characterized in that The specific steps are as follows: Two swirl measuring points are arranged at the grate inlet, and total pressure probes are arranged to measure the axial total pressure and circumferential total pressure of the airflow at the grate inlet respectively; The velocity component of the grate inlet airflow velocity in the probe installation direction is calculated based on the measurement values ​​of the two total pressure probes. The formula is as follows: P 轴 =P+0.5ρV1 2 P 周 =P+0.5ρV2 2 Where P 轴 It represents the total pressure of the airflow measured by the first total pressure probe which is biased toward the axial direction of the grate disc, P 周 represents the total pressure of the airflow measured by the second total pressure probe biased in the radial direction of the grate disc, P represents the static pressure of the airflow, ρ represents the airflow density, V1 represents the velocity component of the airflow velocity at the grate inlet in the direction of the first total pressure probe, and V2 represents the velocity component of the airflow velocity at the grate inlet in the direction of the second total pressure probe; The component velocity is corrected based on the velocity coefficient, and then the velocity V of the airflow at the grate inlet is calculated, and the formula is as follows: ζ(θ-θ1)V1=V·cos(θ-θ1) ζ(90-θ-θ2)V2=V·cos(90-θ-θ2) Wherein, θ1 represents the angle between the first total pressure probe and the axial direction of the grate disc, θ2 represents the angle between the second total pressure probe and the radial direction of the grate disc, and θ represents the angle between the velocity of the grate inlet airflow and the axial direction of the grate disc; Calculate the total axial pressure of the airflow at the grate inlet and circumferential total pressure The formula is as follows:

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