Pneumatic performance test system, flow tube calibration method and apparatus

Abstract

The application aims to provide a pneumatic performance test system, a flow tube calibration method and device, wherein the flow tube calibration method comprises the following steps: placing a flow tube to be calibrated in an experimental device, obtaining the total temperature, total pressure and total pressure static pressure difference of the inlet of the flow tube to be calibrated; calculating the flow tube flow coefficient of the flow tube to be calibrated and the Reynolds number of the flow tube to be calibrated; changing the parameters of the inlet flow working condition, obtaining the combination of the flow tube flow coefficient and the Reynolds number under multiple different inlet flow working conditions; fitting the calibration curve according to the combination of the flow tube flow coefficient and the Reynolds number under multiple different inlet flow working conditions, and calibrating the flow tube to be calibrated according to the calibration curve. The calibration precision of the flow tube can be improved by the flow tube calibration method.

Description

Technical Field

[0001] This invention relates to the field of aerodynamic performance testing, and more particularly to an aerodynamic performance testing system, a flow tube calibration device, and a method. Background Technology

[0002] The fan compressor is one of the most important and complex components of an aero-engine. Experimental research is a crucial means of verifying the performance of the fan compressor during its design and development. When conducting aerodynamic performance tests, the fan intake flow rate is a key parameter. Obtaining fan performance parameters such as characteristic curves, surge boundaries, and margins requires high-precision flow rate measurements.

[0003] Currently, the airflow rate of fan test pieces is mainly measured through an airflow pipe. However, the airflow pipe is a non-standard flow measurement device, and its flow coefficient lacks standard specifications for calibration and calculation. For airflow pipes, the flow coefficient is usually determined by wind tunnel calibration. Generally, newly developed airflow pipes require wind tunnel calibration to determine the flow coefficient in order to ensure that the measurement accuracy meets the usage requirements.

[0004] Current flow tube calibration typically involves measuring the velocity distribution at a target cross-section to obtain the boundary layer thickness, which is then converted into a flow coefficient. However, the inventors discovered that existing flow tube calibration methods cannot obtain high-precision flow coefficients, resulting in insufficient calibration accuracy. Summary of the Invention

[0005] The purpose of this invention is to provide a flow tube calibration method that can improve the calibration accuracy of the flow tube.

[0006] The flow tube calibration method for achieving the aforementioned objective includes the following steps:

[0007] Place the flow tube to be calibrated in the experimental setup and allow air to flow towards the flow tube under inlet conditions.

[0008] Obtain the inlet total temperature, inlet total pressure, and total static pressure difference of the flow tube to be calibrated;

[0009] Obtain the actual flow rate of the inlet of the flow tube to be calibrated;

[0010] Obtain the ambient temperature of the flow tube to be calibrated during calibration, and simultaneously measure the original diameter of the flow tube during calibration;

[0011] The corrected pipe diameter of the flow tube to be calibrated is calculated based on the ambient temperature and the original pipe diameter.

[0012] Obtain the ambient relative humidity during the calibration of the flow tube to be calibrated;

[0013] The corrected gas constant is calculated based on the ambient relative humidity, the inlet total temperature, and the inlet total pressure.

[0014] The measured flow rate of the flow tube to be calibrated is calculated based on the corrected gas constant, the corrected pipe diameter, the inlet total temperature, and the inlet total pressure.

[0015] The flow coefficient of the flow tube to be calibrated is calculated based on the measured flow rate and the actual flow rate, and the Reynolds number of the flow tube to be calibrated is calculated based on the actual flow rate and the corrected pipe diameter.

[0016] By changing the parameters of the intake flow condition, multiple combinations of flow tube flow coefficient and Reynolds number under different intake flow conditions can be obtained;

[0017] A calibration curve is obtained by fitting the flow coefficient and Reynolds number of the flow tube under multiple different inlet flow conditions, and the flow tube to be calibrated is calibrated according to the calibration curve.

[0018] In one or more embodiments, the corrected pipe diameter is calculated using the following formula:

[0019] D t =D ref [1+α(T t -T ref )];

[0020] Among them, D ref T represents the original pipe diameter of the flow meter to be calibrated during calibration. t For the total imported temperature, T ref The ambient temperature during the calibration of the flow meter is α, where α is the coefficient of thermal expansion of the flow meter, and D is the coefficient of thermal expansion of the flow meter. t To correct the pipe diameter.

[0021] In one or more embodiments, the corrected gas constant is calculated using the following formula:

[0022]

[0023] Among them, R f To correct for the gas constant, R is the air gas constant, RH is the ambient relative humidity, and P... t This is the total pressure of the import.

[0024] In one or more embodiments, the measured flow rate is calculated using the following formula:

[0025]

[0026] Where, m ideal Δp is the measured flow rate, Δp is the total static pressure difference, and k is the specific heat ratio of air.

[0027] In one or more embodiments, the flow coefficient and Reynolds number of the flow tube are calculated using the following formula:

[0028]

[0029] Among them, C d Here, Re is the flow coefficient of the flow tube, and Re is the Reynolds number, m real denoted as the actual flow rate, and μ as the aerodynamic viscosity.

[0030] In one or more embodiments, a calibration curve is obtained by fitting the flow coefficient and Reynolds number combination of the flow tube under multiple different inlet flow conditions using the nonlinear least squares method.

[0031] On the other hand, according to some embodiments of the present invention, a flow tube calibration device is also provided, characterized in that the flow tube is calibrated using the flow tube calibration method described above, and the flow tube calibration device includes:

[0032] The intake unit provides a uniform inflow of air toward the flow tube to be calibrated;

[0033] An inlet total temperature probe is positioned upstream of the flow tube to be calibrated along the inlet flow direction to detect and obtain the inlet total temperature;

[0034] A total pressure probe is positioned upstream of the flow tube to be calibrated, along the flow direction, to detect and obtain the inlet total pressure.

[0035] A total pressure-static pressure sensor is installed in the flow tube to be calibrated to detect and obtain the total pressure-static pressure difference;

[0036] A standard flow meter is installed downstream of the flow tube to be calibrated, along the direction of the incoming flow, to detect and obtain the actual flow rate; and

[0037] The exhaust unit is located downstream of the standard flow meter along the direction of the incoming flow.

[0038] In another aspect, according to some embodiments of the present invention, a pneumatic performance testing system is also provided, characterized in that a flow tube calibrated using the flow tube calibration method described above is used for testing.

[0039] In one or more embodiments, the aerodynamic performance testing system is used for aerodynamic testing of compressor fan performance.

[0040] The beneficial effects of this invention are as follows:

[0041] This flow tube calibration method considers the influence of temperature, performing a thermal expansion temperature correction for the flow tube. It also considers the effect of humidity on the air medium, performing a humidity correction for the air gas constant R. Furthermore, it acknowledges the significant impact of static pressure measurement accuracy on flow rate, employing a total pressure-static pressure difference sensor to measure the static pressure on the flow tube wall. Finally, it addresses the dispersion of calibration results, combining the relationship between the flow coefficient and Reynolds number (Re) of the flow tube with least-squares fitting to obtain the curve showing the relationship between the flow coefficient Cd and the Reynolds number Re, thus providing the accuracy of the calibration results. This method offers intake flow tube calibration results and curves that meet the accuracy requirements for fan performance testing.

[0042] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0043] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0044] Figure 1 A schematic diagram of a flow tube calibration apparatus provided according to some embodiments of this application is shown;

[0045] Figure 2 A schematic diagram of a curve obtained by fitting a flow tube calibration method according to some embodiments of this application is shown. Detailed Implementation

[0046] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0048] Regarding the calibration of flow tubes, the applicant found that the current method of measuring the velocity distribution of the target cross section, obtaining the boundary layer thickness, and finally converting it into the flow coefficient only considers the influence of the boundary layer and does not fully consider the fluid compressibility of the entire target cross section. As a result, the obtained fluid coefficient has a large error. However, by providing a new flow tube calibration method and device, the calibration accuracy of flow tubes can be improved.

[0049] According to some embodiments of this application, a flow tube calibration method and a flow tube calibration apparatus for calibrating a flow tube using the flow tube calibration method are provided, such as... Figure 1 A schematic diagram of a flow tube calibration apparatus provided according to some embodiments of this application is shown.

[0050] The flow tube calibration device is used to calibrate the flow tube 7 installed therein. It includes: an intake unit 1, an incoming flow total temperature probe 2, an incoming flow total pressure probe 3, a total pressure static pressure sensor 4, a standard flow meter 5, and an exhaust unit 6. As shown in the figure, the intake unit 1 provides the incoming flow, that is, it introduces air into the flow tube 7 to be calibrated. The airflow direction in this flow tube calibration device, that is, the incoming flow direction, is indicated by arrow a.

[0051] Along the flow direction a, the total temperature probe 2 is positioned upstream of the flow tube 7 to be calibrated, and the total pressure probe 3 is positioned upstream of the flow tube 7 to be calibrated. For example, in the embodiment shown in the figure, the total pressure probe 3 is positioned between the total temperature probe 2 and the flow tube 7 to be calibrated. The total pressure / static pressure sensor 4 is positioned within the flow tube 7 to be calibrated, for example, on the inner wall of the flow tube 7. The standard flow meter 5 is positioned downstream of the flow tube 7 to be calibrated, and the exhaust unit 6 is positioned downstream of the standard flow meter 5.

[0052] The flow tube calibration method includes the following steps:

[0053] Place the flow tube to be calibrated in the experimental setup, and allow air to flow towards the flow tube under inlet flow conditions. For example... Figure 1 As shown, the flow tube 7 to be calibrated is arranged in the test device, and the air intake unit 1 intakes air towards the flow tube 7. It can be understood that the test device can intake air towards the flow tube 7 under different air intake flow conditions. By adjusting parameters such as ambient temperature, ambient humidity, and inlet flow velocity, different air intake flow conditions can be obtained.

[0054] Obtain the inlet total temperature, inlet total pressure, and total static pressure difference of the flow tube to be calibrated. Specifically, for example... Figure 1As shown, the inlet total temperature is obtained through the inlet total temperature probe 2, the inlet total pressure is obtained through the inlet total pressure probe 3, and the total pressure static pressure difference is obtained through the total pressure static pressure sensor 4. It can be understood that the inlet total temperature, inlet total pressure, and total pressure static pressure difference can be detected by other different types of sensors.

[0055] Obtain the actual flow rate at the inlet of the flow tube to be calibrated; specifically, for example... Figure 1 The actual flow rate is obtained through a standard flow meter 5, as shown in the figure.

[0056] Subsequently, the ambient temperature of the flow tube to be calibrated during calibration is obtained, and the original diameter of the flow tube during calibration is measured.

[0057] Subsequently, the corrected pipe diameter of the flow tube to be calibrated is calculated based on the ambient temperature and the original pipe diameter.

[0058] The relative humidity of the environment during the calibration of the flow tube to be calibrated can be obtained, specifically, by detecting it using a corresponding humidity detection device.

[0059] Subsequently, the corrected gas constant was calculated based on the ambient relative humidity, inlet total temperature, and inlet total pressure.

[0060] Subsequently, the measured flow rate of the flow tube to be calibrated is calculated based on the corrected gas constant, corrected pipe diameter, inlet total temperature, and inlet total pressure.

[0061] Subsequently, the flow coefficient of the flow tube to be calibrated is calculated based on the measured flow rate and the actual flow rate, and the Reynolds number of the flow tube to be calibrated is calculated based on the actual flow rate and the corrected pipe diameter.

[0062] Subsequently, the parameters of the intake flow conditions were changed to obtain multiple combinations of flow tube flow coefficients and Reynolds numbers under different intake flow conditions.

[0063] Finally, a calibration curve is obtained by fitting the flow coefficient and Reynolds number combination of the flow tube under multiple different inlet flow conditions, and the calibration accuracy of the flow tube to be calibrated is improved based on the calibration curve.

[0064] Furthermore, in one specific embodiment, the corrected pipe diameter is calculated using the following formula:

[0065] D t =D ref [1+α(T t -T ref )];

[0066] Among them, D ref The original pipe diameter of the flow meter to be calibrated is in meters (m); T t Total inlet temperature, in K; T refα is the ambient temperature during the calibration of the flow meter, in K; α is the coefficient of thermal expansion of the flow meter, in 1 / K; D t To correct for pipe diameter, the unit is meters (m).

[0067] Furthermore, in one specific embodiment, the corrected gas constant is calculated using the following formula:

[0068]

[0069] Among them, R f To correct for the gas constant, the unit is J / (kg K); R is the air gas constant, the unit is J / (kg K); RH is the ambient relative humidity, P t The total inlet pressure is expressed in Pa.

[0070] Furthermore, in one specific embodiment, the measured flow rate is calculated using the following formula:

[0071]

[0072] Where, m ideal The measured flow rate is given by Δp, where Δp is the total static pressure difference in Pa, and k is the specific heat ratio of air.

[0073] Furthermore, in a specific embodiment, the flow coefficient and Reynolds number of the flow tube are calculated using the following formula:

[0074]

[0075] Among them, C d Here, Re is the flow coefficient of the flow tube, and Re is the Reynolds number, m real The actual flow rate is given, and μ is the aerodynamic viscosity, expressed in kg / (m / s).

[0076] Furthermore, in a specific embodiment, a calibration curve is obtained by fitting the flow coefficient and Reynolds number combination of the flow tube under multiple different inlet flow conditions using the nonlinear least squares method. This curve makes the distribution of the flow coefficient and Reynolds number curves of the flow tube more reasonable, effectively improving the calibration accuracy.

[0077] Traditional flow tube calibration methods do not consider the effect of temperature on the thermal expansion of the flow tube, nor do they consider the effect of humidity on the air medium in the flow tube. In addition, they usually directly measure the static pressure on the wall and only provide discrete point values ​​of the flow coefficient. Without analysis and optimization, there are systematic errors in the calibration process.

[0078] This flow tube calibration method considers the influence of temperature, performing a thermal expansion temperature correction for the flow tube. It also considers the effect of humidity on the air medium, performing a humidity correction for the air gas constant R. Furthermore, it acknowledges the significant impact of static pressure measurement accuracy on flow rate, employing a total pressure-static pressure difference sensor to measure the static pressure on the flow tube wall. Finally, it addresses the dispersion of calibration results, combining the relationship between the flow coefficient and Reynolds number (Re) of the flow tube with least-squares fitting to obtain the curve showing the relationship between the flow coefficient Cd and the Reynolds number Re, thus providing the accuracy of the calibration results. This method offers intake flow tube calibration results and curves that meet the accuracy requirements for fan performance testing.

[0079] On the other hand, according to some embodiments of this application, an aerodynamic performance testing system is also provided, in which a flow tube calibrated by the flow tube calibration method described above is used for testing, thereby obtaining more accurate aerodynamic performance test data.

[0080] According to some embodiments of this application, the aerodynamic performance testing system is used for compressor fan performance testing and aerodynamic testing.

[0081] To further demonstrate the advancements of this flow tube calibration method, an example is provided below for further illustration:

[0082] In one specific embodiment, for temperature correction, if the inlet air temperature is 40°C and the relative humidity is 80%, the change rate of the flow tube diameter before and after temperature correction is 0.04%; the change rate of the gas constant before and after humidity correction is 0.02%, and the theoretical flow measurement accuracy can be calculated to be improved by 0.07% according to the flow formula.

[0083] Finally, as Figure 2 As shown, the least squares fitting of the collected flow coefficients and Reynolds number of multiple flow tubes can convert the discrete calibration results into a curve showing the relationship between the flow coefficient Cd and the Reynolds number Re. The points in the figure are the data points showing the relationship between the flow coefficients and Reynolds number of multiple flow tubes, and the curve is the fitting curve obtained after least squares fitting. The calculated flow coefficient calibration accuracy can reach 0.5%.

[0084] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0085] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two).

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A flow tube calibration method, characterized in that, Includes the following steps: Place the flow tube to be calibrated in the experimental setup and allow air to flow towards the flow tube under inlet conditions. Obtain the inlet total temperature, inlet total pressure, and total static pressure difference of the flow tube to be calibrated; Obtain the actual flow rate of the inlet of the flow tube to be calibrated; Obtain the ambient temperature of the flow tube to be calibrated during calibration, and simultaneously measure the original diameter of the flow tube during calibration; The corrected pipe diameter of the flow tube to be calibrated is calculated based on the ambient temperature and the original pipe diameter. Obtain the ambient relative humidity during the calibration of the flow tube to be calibrated; The corrected gas constant is calculated based on the ambient relative humidity, the inlet total temperature, and the inlet total pressure. The measured flow rate of the flow tube to be calibrated is calculated based on the corrected gas constant, the corrected pipe diameter, the inlet total temperature, and the inlet total pressure. The flow coefficient of the flow tube to be calibrated is calculated based on the measured flow rate and the actual flow rate, and the Reynolds number of the flow tube to be calibrated is calculated based on the actual flow rate and the corrected pipe diameter. By changing the parameters of the intake flow condition, multiple combinations of flow tube flow coefficient and Reynolds number under different intake flow conditions can be obtained; A calibration curve is obtained by fitting the flow coefficient and Reynolds number of the flow tube under multiple different inlet flow conditions, and the flow tube to be calibrated is calibrated according to the calibration curve.

2. The flow tube calibration method as described in claim 1, characterized in that, The corrected pipe diameter is calculated using the following formula: D t =D ref [1+α(T t -T ref )]; Among them, D ref T represents the original pipe diameter of the flow meter to be calibrated during calibration. t For the total imported temperature, T ref The ambient temperature during the calibration of the flow meter is α, where α is the coefficient of thermal expansion of the flow meter, and D is the coefficient of thermal expansion of the flow meter. t To correct the pipe diameter.

3. The flow tube calibration method as described in claim 2, characterized in that, The corrected gas constant is calculated using the following formula: Among them, R f To correct for the gas constant, R is the air gas constant, RH is the ambient relative humidity, and P... t This is the total pressure of the import.

4. The flow tube calibration method as described in claim 3, characterized in that, The measured flow rate is calculated using the following formula: Where, m ideal Δp is the measured flow rate, Δp is the total static pressure difference, and k is the specific heat ratio of air.

5. The flow tube calibration method as described in claim 4, characterized in that, The flow coefficient and Reynolds number of the flow tube are calculated using the following formula: Among them, C d Here, Re is the flow coefficient of the flow tube, and Re is the Reynolds number, m real denoted as the actual flow rate, and μ as the aerodynamic viscosity.

6. The flow tube calibration method as described in claim 1, characterized in that, The calibration curves were obtained by fitting the flow coefficient and Reynolds number combination of the flow tube under several different inlet flow conditions using the nonlinear least squares method.

7. A flow tube calibration device, characterized in that, The flow tube is calibrated using the flow tube calibration method as described in any one of claims 1 to 6, wherein the flow tube calibration device comprises: The intake unit provides a uniform inflow of air toward the flow tube to be calibrated; An inlet total temperature probe is positioned upstream of the flow tube to be calibrated along the inlet flow direction to detect and obtain the inlet total temperature; A total pressure probe is positioned upstream of the flow tube to be calibrated, along the flow direction, to detect and obtain the inlet total pressure. A total pressure-static pressure sensor is installed in the flow tube to be calibrated to detect and obtain the total pressure-static pressure difference; A standard flow meter is installed downstream of the flow tube to be calibrated, along the direction of the incoming flow, to detect and obtain the actual flow rate; and The exhaust unit is located downstream of the standard flow meter along the direction of the incoming flow.

8. A pneumatic performance testing system, characterized in that, The flow tube calibrated using the flow tube calibration method as described in any one of claims 1 to 6 is then tested.

9. The aerodynamic performance testing system as described in claim 8, characterized in that, The aerodynamic performance testing system is used for aerodynamic testing of compressor fan performance.

Images