GB/T 2423.41-1994 Basic environmental testing procedures for electrical and electronic products - Wind pressure test method
Some standard content:
National Standard of the People's Republic of China
Basic environmental testing procedures for electricand electronic products
Wind pressure
1 Subject content and scope of application
GB/T 2423.41-94
This standard specifies the terminology, requirements for test equipment and test samples (hereinafter referred to as test pieces), test conditions and test methods for wind pressure tests of electric and electronic products using wind tunnels. This standard is applicable to testing the adaptability of electric and electronic equipment or components (such as radar antennas, microwave antennas, satellite antennas, etc.) installed outdoors when subjected to wind pressure and evaluating the rationality of their structures. This standard does not apply to towers for fixing electric and electronic equipment or components. 2 Terminology
2.1 Wind tunnel
In a pipeline system designed according to special requirements, a power device such as a fan is used to artificially generate and control airflow to simulate the flow of gas around the test piece, and the effect of the airflow on the test piece can be measured. The part where the test piece is installed is called the test section. A wind tunnel with a wind speed lower than 135m/s is called a low-speed wind tunnel. 2.2 Wind tunnel test
Install the test piece in the wind tunnel test section and measure the aerodynamic force acting on the test piece when the airflow flows through the test piece to obtain the performance data of the test piece. The test piece can change direction to simulate different wind direction conditions. 2.3 Wind tunnel balance A device that senses and measures the aerodynamic force and aerodynamic torque acting on the test piece. 2.4 Elevation angle
The angle between the projection of the longitudinal reference line (o,) of the test piece and the airflow direction on the longitudinal symmetry plane (αo) of the test section is denoted as α. When the test piece faces the wind head-on, the elevation angle is 0°, when it is tilted upward, the elevation angle is positive, and when it is tilted downward, the elevation angle is negative (see Figure 1). 2.5 Azimuth angle
The angle between the projection of the longitudinal reference line (o) of the test piece and the airflow direction on the horizontal symmetry plane (oy) of the test section is denoted as β. When the test piece faces the wind head-on, the azimuth angle is 0°, when it rotates counterclockwise, the azimuth angle is positive, and when it rotates clockwise, the azimuth angle is negative (see Figure 1). Approved by the State Administration of Technical Supervision on July 7, 1994 392
Implementation on January 1, 1995
View (along the oy axis)
Top view (z axis》
GB/T 2423.41-94
Front view (or axis)
Figure 1 Schematic diagram of wind axis o, oyoz, body axis or1oy1oz1, elevation angle α and azimuth angle β 2.6 Aerodynamic force The forces (including drag, crosswind force, side force) and moments (including rolling moment, pitching moment, yaw moment, see Figure 2) generated when air flows through the test piece.
Figure 2 Schematic diagram of drag X, crosswind force Z, side force Y, rolling moment Mx, pitching moment My, yaw moment Mz 2.7 Aerodynamic force (moment) coefficients aerodynamic force coefficientThe dimensionless coefficient of aerodynamic force (torque) divided by the characteristic area of the test piece (characteristic area multiplied by characteristic length) and the airflow dynamic pressure. Aerodynamic coefficient C, = F/(Q·S), aerodynamic moment coefficient Cm=M/(Q·S·L) where F and M are force and moment respectively, C and C are their coefficients respectively, S is the characteristic area, which is the maximum projection area of the solid part of the test piece in this standard, L is the characteristic length, which is the maximum extension length of the solid part of the test piece in this standard, Q is the dynamic pressure, Q=0.5·β· (where β is the air density and is the wind speed). 2.8 Wind pressurewind pressure
The pressure generated on the surface of the test piece when the airflow flows through the test piece. The wind pressure coefficient is C(P1-P)/Q, where P1 is the pressure value at a certain point of the test piece, and P is the static pressure value far in front of the incoming flow that is not disturbed by the test piece. 2.9 Wind speedwind speed
GB/T 2423.41—94
Relative speed between the test piece and the airflow. For a test piece mounted on a moving device (such as a ship radar), it refers to the vector sum of the wind speed in the atmosphere and the speed of the device.
2.10 Reynolds number
A dimensionless parameter that characterizes the relative magnitude of the inertial force and the viscous force of the air, denoted by Re. Re=（p·u·l）/u, where β is the air density, is the dynamic viscosity coefficient of the air, is the wind speed, and L is the characteristic length. 2.11 Body axes system The orthogonal coordinate axes 0T1, 0y1, 021 (see Figure 1) fixed on the test piece conform to the right-hand rule. 2.12 Wind axes system system
The reference orthogonal coordinate axis system 0α, 0y, 0z (see Figure 1) based on the airflow direction conforms to the right-hand rule. 3 Requirements for test equipment and test pieces
3.1 The diameter of the wind tunnel test section should be greater than 2m.
3.2 The accuracy of wind tunnel flow field and wind tunnel balance and other measuring instruments shall comply with relevant standards. 3.3 The extension of the test piece shall not exceed 70% of the width of the wind tunnel test section. 3.4 The maximum projected area of the test piece shall not exceed 10% of the cross-sectional area of the wind tunnel test section. 3.5 The rotation center of the test piece is located on the geometric center axis of the wind tunnel test section. 3.6 When the test piece is a scaled model for wind tunnel testing, the model shall meet the requirements of the similarity criterion. 4 Test conditions
4.1 Test wind speed
The test wind speed is 15, 30, 35, 45 and 52m/s, or as specified in relevant standards. If the test piece is a scaled model, its test wind speed shall be converted according to the similarity criterion or as specified in relevant standards.
4.2 Test angle
Range of elevation angle α and azimuth angle β of the test piece: α = -15°~+15°, interval 2.5° = -10°~+190°, interval 10° For test pieces with pitch working state, the above α angle should be added to the pitch working angle or combined according to the relevant standards. 4.3 Test items
According to the actual environmental conditions, the test piece shall be subjected to the following (or select several) tests: static state force measurement;
rotating state force measurement;
static state pressure measurement,
d, flexible component deformation measurement.
5 Test method
5.1 Initial measurement
5.1.1 Place the test piece under normal atmospheric conditions and conduct electrical performance, mechanical performance testing and appearance inspection according to the relevant standards. 5.1.2 The test piece is installed in the wind tunnel test section according to the usage status. After horizontal calibration and debugging, the original data of each component force at each angular position are read out without blowing wind.
5.2 Wind measurement
5.2.1 When measuring force in static state, the test piece shall be installed in the wind tunnel according to the use state, and the force and torque shall be measured according to 4.1 and 4.2 or relevant standards.
5.2.2 Force measurement in rotating state:
a. The test piece shall be installed in the test section of the wind tunnel according to the use state, and the wind speed shall be increased to 35m/s or as required by relevant standards. The test piece shall be started by adjusting the change angle according to 4.2, and the force and torque shall be measured. At the same time, the performance index 39.1 shall be tested according to the test time and whether the power is turned on according to the relevant standards;
GB/T 2423. 41--94
The test piece shall be installed in the test section of the wind tunnel according to the use state, and the wind speed shall be increased to 52m/s or as required by relevant standards. The test piece shall be started by adjusting the change angle according to 4.2, and the force and torque shall be measured. At the same time, the performance index shall be tested according to the test time and whether the power is turned on according to the relevant standards.
Measurement. bZxz.net
When measuring pressure in static state, the test piece is installed in the wind tunnel according to the use state, and the pressure is measured according to 4.1 and 4.2 or relevant standards. 5.2.4 For test pieces installed close to the ground or with large objects around them, typical situations should be selected for simulation tests to provide the magnitude of possible impact.
5.2.5 For test pieces with greater flexibility, pre-calibrated strain gauges should also be attached to the relevant positions of the test pieces to measure the deformation of the relevant components of the test pieces.
5.3 Final measurement
Under normal atmospheric conditions, the test piece is tested for electrical properties, mechanical properties and appearance, or in accordance with relevant standards. 6 Data processing
6.1 The wind tunnel test data should be corrected for support interference and tunnel wall interference according to relevant standards, and the shaft system should be converted to provide usable wind shaft system aerodynamic coefficients.
6.2 When the test piece is used for wind tunnel testing, the corrected test data can be directly compared with the original design data to determine the rationality of the test piece's external structure.
6.3 When the test piece is a scaled model for wind tunnel testing, the corrected test data must be converted into data corresponding to the test piece in accordance with the relevant standards before it can be compared with the original design data. 7 Contents to be included in relevant standards
When the relevant standards cite this standard, specific provisions should be made for the following items: requirements for test equipment;
description of the test piece;
selection of test conditions and relevant performance measurement content and requirements; c.
intermediate measurement content and requirements;
final measurement content and requirements.
GB/T 2423.41--94
Appendix A
Data processing
(Supplement)
The aerodynamic force measured by the wind tunnel balance is given in terms of the body axis system. When used, the data of the body axis system should be converted into data of the wind axis system. The formula is:
Cx,cosacos -- Cyisinp + C, sinacospCx=
C, = Cx,cosasinβ + Cyicosβ + Cz,sinasinβC, =- C,sinα + C,cosa
Cmx Cmx, cosacosp +- Cmy,sinβ + Cm, sinacospCmy = Cmx,cosasinβ+ Cmy,cosβ + Cm,sinasinpCm =-Cmx,sina + Cmr,cosa
For test pieces with relatively small obstruction, the blockage correction can be made directly by using formula 1
(maximum projected area of the test piece + projected area of the bracket) cross-sectional area of the test section
, where is the blockage correction factor. When the blockage is relatively large, the wall pressure information method should be used for correction. The bracket interference correction can be made by deducting the aerodynamic force of the individual bracket. Except for parabolic antennas, the influence of the Reynolds number Re can be ignored. Appendix B
Reference table of wind speed levels
(reference)
Sea wave height, m
1~～5
20～28
Consequences
nmile/h
17~～~21
41～47
0. 3~1. 5
5. 5~7. 9
10.8~13.8
13. 9~17.1
17.2~20.7
20.8~~24.4
Smoke can indicate direction
People feel wind on their faces, leaves rustle slightly
Flags spread out, leaves sway
Small branches sway
Small trees sway, small waves on inland waters
Big branches sway, electric wires whirr
Whole trees sway, big branches bend down
People feel great resistance when moving forward
Smoke windows and roofs are sometimes damaged
Additional notes:
Sea wave height, m
GB/T2423.41—94
89～102
103~~117
118~133
n mile/h
56~~63
24.5~28.4
28. 5~32. 6
32. 7 ~~36. 9
Consequences
Can uproot trees, rarely seen on land
Major losses, rarely seen on land
Great destructive power, rarely seen on land
This standard is under the jurisdiction of the National Technical Committee for Environmental Testing and Environmental Conditions for Electrical and Electronic Products. This standard was drafted by the Standards and Metrology Institute of the Ministry of Transport and the Low Speed Institute of the China Aerodynamics Research and Development Center. The main drafters of this standard are Yuan Shuncai, He Dexin, Liu Shangpei, Zhang Liangliang, and Tian Lin. 397
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