CN111677683B - Method and device for testing pneumatic performance of micro fan based on flow compensation method - Google Patents

Abstract

The invention discloses a method and device for testing the aerodynamic performance of a micro-fan based on a flow compensation method. Switch on to obtain the desired flow point. The flow compensation unit contains pipes and laminar flow elements corresponding to those in the flow measurement unit. Each flow measurement pipeline and the flow compensation pipeline are connected together through a three-way ball valve, and the other outlet of the three-way ball valve is connected to the collecting container. When working, the regulating valve is fixed at a certain opening and remains unchanged, and the three-way ball valve is used to control the opening and closing of each measuring pipeline to change the test flow. The three-way ball valve is either connected to the measuring pipe or the compensation pipe. The flow rates of the two pipes are complementary, and the working conditions of the auxiliary fan are almost unchanged. This adjustment method can obtain a relatively accurate flow point. The data is accurate and suitable for aerodynamic performance testing of micro-flow fans.

Description

A method and device for testing aerodynamic performance of micro-fan based on flow compensation method

technical field

The invention relates to the field of fan performance testing, in particular to a method and device for testing the aerodynamic performance of a miniature fan based on a flow compensation method.

Background technique

With the miniaturization of electronic equipment, the fans in the cooling system also have requirements for miniaturization and miniaturization, and the air volume and air pressure parameters of micro fans are smaller and lower. At the same time, the existing fan aerodynamic performance testing technology and devices need to be improved and updated to meet the needs of fan production and use.

In the field of fan aerodynamic performance testing, the more commonly used standard is the "Laboratory Method for Fan Rated Performance Experiments" by the American National Standards Organization Ventilation and Air Conditioning Association -- ANSI/AMCA210/ASHRAE51-2007. The Chinese standard GB/T1236-2000 "Industrial Fans - Performance Test with Standardized Air Ducts" is a commonly used standard in the field of domestic fans. In the standard, it is generally recommended to use flow nozzles for flow measurement. In order to meet a wide range of flow measurement, a multi-nozzle combination is used. The standard provides more detailed regulations for nozzle shape design and multi-nozzle layout requirements. The calculation formula of the flow correction coefficient used for the flow nozzle, but the formula has the applicable range of Reynolds number, and cannot be used directly for micro-fans with small flow. In addition, micro-throat nozzles are difficult to process, which limits their use in micro-gas flow. The standard states that other suitable flow measurement techniques can be selected, and suggestions are also given for the selection of flow points, but there are no specific provisions for flow adjustment methods.

The laminar flow measurement technology works based on the principle that the flow through the laminar flow element has a linear relationship with the pressure drop. It has the characteristics of accurate measurement, good repeatability, wide range ratio, stability and reliability, and low requirements for straight pipe sections. It is very suitable for measurement Small gas flow is also more suitable as a standard flow meter. However, the laminar flow element generally has a relatively large pressure loss, so when it is used for fan performance testing, it is necessary to control the pressure loss of the laminar flow element as much as possible in the design.

The fan test system generally uses a flow control valve to adjust the flow, and can also adjust the flow by changing the fan motor speed. At present, the fan test system is usually automatically controlled, that is, the automatic test is carried out according to the set flow point under the control of the computer, which requires automatic adjustment and control of the flow. Since the characteristics of the flow control valve and the fan are nonlinear, it is not easy to obtain good results in automatic control, and the adjustment time is long, the accuracy is not good, and even the situation is not easy to stabilize. In addition, the flow range of the test system is very large, and the auxiliary fan often works unstable under the condition of small flow rate. Sometimes it is necessary to select two fans of large and small size to solve this problem, which increases the complexity of the equipment.

SUMMARY OF THE INVENTION

In order to solve the problems of micro-flow measurement and automatic flow adjustment in the micro-fan aerodynamic performance testing system, the present invention provides a micro-fan aerodynamic performance testing method and device based on the flow compensation method, and the specific technical scheme is as follows:

The micro-fan aerodynamic performance test device based on the flow compensation method is composed of an equalizing chamber, a flow measurement unit, a flow compensation unit, a collection container, a regulating valve, an auxiliary fan, and a sensing and measurement and control system. Among them, the flow measurement unit includes multiple measurement pipelines with different flow ranges, and the laminar flow method is used to measure the flow. Each pipeline is equipped with a laminar flow element, a three-way ball valve, and the corresponding pressure pipe and solenoid valve; The flow compensation unit contains pipes, laminar flow elements and compensation chambers corresponding to the flow measurement unit; the sensing and measurement and control system includes a differential pressure sensor, a pressure sensor, a temperature sensor, an atmospheric pressure and humidity sensor, a measurement and control unit and a computer.

During the fan test, the air flow enters the pressure equalizing chamber, the flow measurement pipe, the three-way ball valve, the collecting container, and the regulating valve in turn through the tested fan, and finally is discharged through the auxiliary fan. The flow is measured by the flow measurement unit, and the wind pressure of the fan to be measured is led out to the pressure sensor for measurement through the arrangement in the air-equalizing chamber.

The specifications and flow ranges of laminar flow elements of each measuring pipeline are generally different, and each pipeline can be connected individually or in combination to obtain the required flow point.

According to the principle of laminar flow measurement, the flow through the laminar flow element is proportional to its upstream and downstream pressure drop, and the flow is calculated from the measured differential pressure according to the Hagen-Poiseuille formula. The air viscosity required in the calculation is calculated from the air viscosity physical property formula according to the temperature, humidity and atmospheric pressure data measured by the sensor. The measured fan wind pressure is led out to the pressure sensor for measurement through the pressure taking hole arranged in the air equalizing chamber.

Through the L-type three-way ball valve, control whether each flow measurement pipeline is connected to adjust the flow. The three-way ball valve is either connected to the measurement pipeline or the compensation pipeline. The measurement pipeline and the compensation pipeline are complementary. If the influence of the measured fan is ignored, the impedance of the entire pipeline system remains unchanged, and the flow through the entire pipeline system It remains unchanged and the auxiliary fan working condition remains unchanged, so a relatively accurate flow point can be obtained by connecting different measuring pipes.

The reason for choosing the laminar flow measurement technology is that this technology is very suitable for the measurement of gas micro flow. In addition, in the laminar flow method, the flow rate is proportional to the pressure drop at both ends of the laminar flow element, and the flow rate of the laminar flow element (each measuring pipe) is easily combined. Each laminar flow element contains multiple capillaries. The length and inner diameter of the capillaries in each laminar flow element are exactly the same. The only difference is the number of capillaries. The laminar flow elements in each measuring pipe and its corresponding flow compensation pipe are exactly the same. In this way, under the same differential pressure, the flow rate of each laminar flow element is proportional to the number of capillaries, and the flow combination model of each flow measurement pipeline is linear, and the combination is simple and reliable. If other types of flowmeters are selected, the flow compensation method of the present invention can also be used to realize flow adjustment, and the adjustment accuracy will be lower than that of the laminar flow method.

The upper laminar flow elements of each flow measurement pipeline share the same differential pressure sensor. If a flow measurement pipeline is connected, the electronic valve on the pressure taking pipe will be opened at the same time to connect the pressure taking pipe, otherwise it will be closed.

The signals of the differential pressure sensor, pressure sensor, atmospheric pressure and temperature pressure sensor are collected by the measurement and control unit, and the measurement data is processed, analyzed, displayed and output by the computer. The measurement and control unit controls the action of the three-way ball valve and the solenoid valve at the same time, and completes the measurement process under the control of the computer program.

The function of the auxiliary fan is to overcome the flow resistance of the flow measurement pipe and ensure that the fan under test can reach the maximum flow condition.

The function of the regulating valve is to adjust the overall impedance of the entire pipeline system to meet the measurement requirements. During the fan test, firstly adjust each three-way ball valve to the connected state of the measurement pipeline, turn on the auxiliary fan, and then adjust the valve to an appropriate opening, so that the pressure at the pressure measuring point of the air-equalizing chamber is zero. At this time, the fan under test is The maximum flow rate is reached. Next, neither the auxiliary fan nor the regulating valve is adjusted. According to the computer setting program, the measurement and control unit controls the three-way ball valve to sequentially close and connect each measurement pipeline to obtain the required flow point and complete the measurement process.

The beneficial effects that the present invention has are:

1) The present invention proposes a flow compensation method. Based on this method, the overall impedance of the entire pipeline system remains unchanged, and the flow adjustment required for measurement can be realized by the combination of opening or closing each measurement pipeline. The flow adjustment method is simple, reliable, fast and accurate. , which can improve the work efficiency of the test system.

2) The laminar flow technology is used for flow measurement, which can ensure the accurate measurement of gas micro flow.

3) The specifications of the capillaries in each laminar flow element are the same, and under the same differential pressure, the flow rate of each laminar flow element is proportional to the number of capillaries, which makes the flow combination model between the measurement pipes simple and linear, and ensures fast flow adjustment during the measurement process. precise.

4) The laminar flow element is used for flow measurement, which does not require long upstream and downstream straight pipe sections, and the device has a compact structure.

5) Since the flow rate is proportional to the differential pressure on both sides of the laminar flow element, under the same range of the differential pressure sensor, a larger range ratio can be achieved than the flow nozzle (the flow rate and the differential pressure have a quadratic relationship).

6) During the measurement process, the auxiliary fan is in the best working condition range, and the operation is stable, which ensures the stability of the airflow in the fan test pipeline.

Description of drawings

Fig. 1 Schematic diagram of aerodynamic performance testing device of micro-fan by flow compensation method;

Figure 2 is a schematic diagram of the flow measurement pipeline and the flow compensation pipeline;

Each reference number in the figure:

100-flow measurement unit; 200-flow compensation unit

1- Tested fan; 2- Air chamber; 3- Collecting container; 4- Regulating valve; 5- Auxiliary fan; 6- Differential pressure sensor; 7- Pressure sensor; 8- Atmospheric pressure and temperature and humidity sensor; 9- Measurement and control unit; 10-computer; 11-laminar flow element A; 12-laminar flow element B; 13-laminar flow element C; 14-laminar flow element D; 15-three-way ball valve A; 16-three-way ball valve B; 17 -Three-way ball valve C; 18-Three-way ball valve D; 19-Solenoid valve A; 20-Solenoid valve B; 21-Solenoid valve C; 22-Solenoid valve D; 23-Laminar flow element A'; 24-Laminar flow element B'; 25 - laminar flow element C'; 26 - laminar flow element D'; 27 - compensation chamber.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings.

As shown in FIG. 1 , the flow compensation method micro-fan aerodynamic performance test device of the present invention consists of an air equalizing chamber 2, a flow measurement unit 100, a flow compensation unit 200, a collection container 3, a regulating valve 4, an auxiliary fan 5, and a sensor It is composed of measurement and control system. The flow measurement unit 100 includes a plurality of measurement pipes, without loss of generality. Here, four measurement pipes are taken as an example. Each measurement pipe is equipped with a laminar flow element, an L-shaped three-way ball valve, and a corresponding Pressure pipes and solenoid valves, etc., as shown in Figure 2, namely laminar flow element A 11, laminar flow element B 12, laminar flow element C 13, laminar flow element D 14, three-way ball valve A 15, three-way ball valve B 16, Three-way ball valve C 17, three-way ball valve D 18, solenoid valve A 19, solenoid valve B 20, solenoid valve C 21, solenoid valve D 22; the flow compensation unit 200 contains pipes and laminar flow elements corresponding to the flow measurement unit 100 and compensation chamber, namely laminar flow element A'23, laminar flow element B'24, laminar flow element C'25, laminar flow element D'26 and compensation chamber 27; the sensing and measurement and control system includes differential pressure sensor 6 , pressure sensor 7 , atmospheric pressure and temperature and humidity sensor 8 , measurement and control unit 9 and computer 10 .

During the fan test, the air flow enters the pressure equalizing chamber 2, the flow measurement pipe, the three-way ball valve, the collecting container, and the regulating valve in turn through the tested fan 1, and finally is discharged through the auxiliary fan. The flow is measured by the flow measurement unit, and the wind pressure of the fan to be measured is led out to the pressure sensor for measurement by being arranged in the air equalizing chamber.

According to the laminar flow measurement principle, the flow through a laminar flow element is proportional to its upstream and downstream pressure drop. According to the Hagen-Poiseuille formula, the measured differential pressure is calculated to obtain the flow Q _i , namely

（1）

(1)

In the formula, μ-dynamic viscosity of air;

n _i - the number of capillaries in the laminar flow element;

d - the inner diameter of the capillary;

L-capillary length;

ΔP - Differential pressure across the laminar flow element.

The air viscosity required in the calculation is calculated from the air viscosity physical property formula according to the temperature, humidity and atmospheric pressure data measured by the sensor.

The measured fan wind pressure is led out to the pressure sensor for measurement through the pressure taking hole arranged in the air equalizing chamber. The gauge pressure (or relative pressure, that is, the difference between absolute pressure and atmospheric pressure) measured by the pressure sensor is the fan static pressure P _s .

The specifications and flow ranges of laminar flow elements in each flow measurement pipeline are generally different, and each pipeline can be connected individually or in combination to obtain the required flow point. The laminar flow elements in each measuring pipe and its corresponding flow compensation pipe are identical. During the fan test, the L-shaped three-way ball valve is used to control whether the flow measurement pipeline is connected to adjust the flow. The three-way ball valve is either connected to the measurement pipeline or the compensation pipeline. The measurement pipeline and the compensation pipeline are complementary. Under the condition that the influence of the measured fan is ignored, the impedance of the entire pipeline system remains unchanged and flows through the entire pipeline system. The flow rate is always the same, and the working condition of the auxiliary fan is unchanged, so a relatively accurate flow point can be obtained by connecting different measurement pipes.

The capillary length and inner diameter of each laminar flow element are exactly the same, the difference is the number of capillaries. The upper laminar flow elements of each flow measurement pipe share the same differential pressure sensor, that is, when multiple measurement pipes are in the connected state, it is equivalent to parallel connection of multiple laminar flow elements, and the differential pressure on both sides is the same. According to formula (1), when the capillary length, diameter and differential pressure at both ends are the same, the flow is proportional to the number of capillaries. The flow combination model of each flow measurement pipeline is linear, and the combination is very simple. For example, assuming that the ratio of the number of capillaries of laminar flow elements in 4 pipes is 1:2:4:8, and the passing capacity of the smallest pipe is q, the combination of q, 2q, 3q,...,15q can be obtained. any of the traffic.

It should be pointed out that if other types of flowmeters are selected, the flow compensation method of the present invention can also realize flow adjustment, and the adjustment accuracy will be lower than that of the laminar flow flow measurement method. In addition, although the parameters of the micro-fan under test are generally much lower than those of the auxiliary fan, the change of the working conditions still has a certain influence on the entire pipeline system. When the flow point is not strictly required, this influence can be ignored.

When using the device in the present invention to carry out the actual test, the following operation process can be referred to:

1) Select the appropriate connection accessories according to the shape and size of the outlet of the tested fan 1, install the fan on the inlet panel of the air chamber, and seal the gap between the fan inlet and the connection accessories to ensure that there is no air leakage when the fan is working;

2) Set the flow point on the computer operation interface;

3) Set the 4 three-way ball valves to the state of being connected to the flow measurement pipeline, and adjust the regulating valve to the closed state;

4) Turn on the power of the fan under test, and the fan under test enters the running state. At this time, the flow in the flow measuring pipe is zero, and the pressure measured by the pressure sensor is a positive pressure number, which is actually the maximum wind pressure of the fan under test;

5) Start the auxiliary fan;

6) Adjust the opening of the regulating valve until the wind pressure is displayed as zero, or slightly greater than zero. Be careful not to be negative. At this time, the tested fan reaches the maximum flow condition;

7) Click the start measurement button on the computer measurement interface to complete the measurement process under the control of the computer program.

The above are only the basic ideas and methods of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the ideas and principles of the present invention should be included in the protection of the present invention. within the range.

Claims (6)

1. The utility model provides a miniature fan aerodynamic performance testing arrangement based on flow compensation method, includes even wind cavity (2), flow measurement unit (100), flow compensation unit (200), collection container (3), governing valve (4), auxiliary fan (5) to and sensing and observing and controlling system, its characterized in that: the flow measurement unit (100) comprises a plurality of measurement pipelines, wherein each measurement pipeline is provided with 1 laminar flow element, 1 three-way ball valve, and corresponding pressure tapping pipes and corresponding electromagnetic valves, namely a laminar flow element A (11), a laminar flow element B (12), a laminar flow element C (13), a laminar flow element D (14), a three-way ball valve A (15), a three-way ball valve B (16), a three-way ball valve C (17), a three-way ball valve D (18), an electromagnetic valve A (19), an electromagnetic valve B (20), an electromagnetic valve C (21) and an electromagnetic valve D (22); the flow compensation unit (200) comprises a pipeline, a laminar flow element and a compensation chamber corresponding to the flow measurement unit (100), namely a laminar flow element A '(23), a laminar flow element B' (24), a laminar flow element C '(25), a laminar flow element D' (26) and a compensation chamber (27); the sensing, measuring and controlling system comprises a micro differential pressure sensor (6), a pressure sensor (7), an atmospheric pressure and temperature and humidity sensor (8), a measuring and controlling unit (9) and a computer (10); the air flow sequentially enters an air equalizing chamber (2), a flow measuring pipeline, a three-way ball valve, a collecting container and a regulating valve through a tested fan (1), and is finally discharged through an auxiliary fan, the flow is measured by a flow measuring unit, and the wind pressure of the tested fan is led out to a pressure sensor for measurement through the air equalizing chamber;

the laminar flow elements of each measuring pipeline have different flow ranges, and each pipeline is independently communicated or communicated in combination to obtain a required flow point.

2. The device for testing the aerodynamic performance of a micro fan based on the flow compensation method as claimed in claim 1, wherein: each flow measuring pipeline is connected with the flow compensation pipeline through a three-way ball valve, and the other outlet pipeline of the three-way ball valve is connected to the collecting container; when the fan is tested, the flow measuring pipeline is controlled to be connected or not through the three-way ball valve to adjust the required flow; the three-way ball valve is communicated with a measuring pipeline or a compensating pipeline, and the flow of the measuring pipeline and the flow of the compensating pipeline are in a complementary relationship.

3. The device for testing the aerodynamic performance of a micro fan based on the flow compensation method as claimed in claim 1, wherein: each laminar flow element contains a plurality of capillaries, and the lengths and the inner diameters of the capillaries in the laminar flow elements are completely the same, and the number of the capillaries is different; each measuring pipeline is completely the same as the laminar flow element in the corresponding flow compensation pipeline, and under the condition that the differential pressure is the same, the flow of each laminar flow element is in direct proportion to the number of the capillary tubes.

4. The device for testing the aerodynamic performance of a micro fan based on the flow compensation method as claimed in claim 1, wherein: and the upper flow elements of all the flow measuring pipelines share the same micro differential pressure sensor, if a certain flow measuring pipeline is connected, the electronic valve on the pressure sampling pipe is simultaneously opened to connect the pressure sampling pipe, and if not, the electronic valve is closed.

5. The device for testing the aerodynamic performance of a micro fan based on the flow compensation method as claimed in claim 1, wherein: other types of flow meters are used instead of laminar flow measurement components.

6. A method for testing the aerodynamic performance of a micro fan using the apparatus for testing the aerodynamic performance of a micro fan based on the flow compensation method according to claim 1, comprising the steps of:

1) selecting a connecting fitting according to the shape and the size of an outlet of the tested fan (1), and mounting the fan on an inlet panel of the air equalizing chamber;

2) setting a flow point on a computer operation interface;

3) setting 4 three-way ball valves to be in a state of being communicated with a flow measurement pipeline, and adjusting a regulating valve to be in a closed state;

4) turning on a power supply of the tested fan, enabling the tested fan to enter an operating state, wherein the flow in the flow measuring pipeline is zero, the value measured by the pressure sensor is a certain positive pressure figure, and the maximum wind pressure of the tested fan is actually measured;

5) starting the auxiliary fan;

6) adjusting the opening of the regulating valve until the wind pressure is zero or slightly greater than zero, and the measured fan reaches the maximum flow working condition;

7) and clicking a measurement starting key on a computer measurement interface to finish the measurement process under the control of a computer program.

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