A control method for spray icing system in icing test

Abstract

A control method for a spray icing system in an icing test relates to the field of icing technology. The method solves the problem that the amount of droplets on the surface of the test piece is small and the ice layer is thin during the existing icing test on the surface of the test piece. The method comprises: a temperature sensor is provided in the test chamber, and the temperature sensor feeds back the temperature measurement signal to the PLC; the difference between the temperature measurement value and the set value and the air temperature inside and outside the test chamber is calculated; the amount of cold air to be introduced into the test chamber is calculated according to the difference; a fan is selected according to the amount of circulating air to form a circulating fan; when the temperature in the test chamber reaches a preset temperature, the background fan array is turned on; when the icing test starts, the valves of the water supply and air supply pipelines are opened, and compressed air and low-temperature ultrapure water are respectively provided by the air compressor and the water pump and sprayed through the nozzle to form a cloud, and the circulating fan continues to work to provide the refrigeration required for the cloud icing test. The present invention improves the effect and reliability of the icing test.

Description

Technical Field

[0001] The invention relates to the technical field of icing. Background Art

[0002] The existing icing technologies mainly include icing wind tunnels and climate environment laboratories. Among them, the incoming flow of the icing wind tunnel test can simulate the flight process very well, and is suitable for icing simulation under high-speed airflow conditions (such as aircraft flight process, engine air intake, etc.). The size of the test piece accounts for 1 / 5 to 1 / 10 of the cross-sectional area of ​​the cloud flow, and the impact of the airflow around the flow is small, and the icing effect is good; the trajectory of the cloud in the climate environment laboratory is close to a parabola, and with the array nozzle, a large-scale low-wind speed cloud environment can be formed, and a good icing effect can be obtained on the horizontal plane, so it is suitable for icing tests of helicopters.

[0003] For vertical test pieces, if an icing wind tunnel is used, in order to optimize the icing effect, the required cross-sectional area of ​​the cloud flow will be very large, and the construction cost will be very high. However, the cloud environment in the climate environment laboratory that is suitable for helicopter icing tests has a poor icing effect on the surface of the vertical test piece.

[0004] When using an array air atomizing nozzle to spray directly at a large vertical test piece and conducting an icing test on the test piece surface in a low-temperature environment, the spray droplets are greatly affected by gravity, and most of the droplets will fall on the ground in front of the spray. Some droplets follow the airflow to the two sides of the vertical test piece, resulting in a small amount of droplets hitting the surface of the test piece and a thin ice layer.

[0005] Prior art CN112923623A discloses a high snowmaking rate snowmaking machine and its control method and working method, comprising a barrel and a plurality of nozzles, a plurality of gas-liquid nucleators and a plurality of air nucleators installed on the inner surface of the barrel: a water inlet pipe is connected to each nozzle and each gas-liquid nucleator respectively, an air compressor outlet is divided into two paths, one is connected to each gas-liquid nucleator, and the other is connected to each air nucleator through a flow control valve; a fan is installed at the middle position of the barrel inlet, and a temperature and humidity sensor (TH) is installed on the outer wall of the barrel; a control module (C1) is connected to the flow control valve temperature and humidity sensor (TH) respectively; the air nucleator throttles and expands the compressed air to reduce the temperature, and mixes it with the droplets and ice nuclei sprayed from the nozzle and the gas-liquid nucleator, providing a secondary supercooling area, promoting the nucleation of atomized water droplets that have not been nucleated, and also promoting the rapid growth of nucleated ice particles into snowflakes, thereby improving the snowmaking efficiency of the snowmaking machine.

[0006] The snowmaking involved in this technology is a type of frost, namely soft frost, and other types of icing, such as clear ice and mixed ice, cannot be obtained. In addition, this technology is only applicable to small test pieces and can only obtain one type of icing, namely soft frost. Therefore, it cannot be used for icing tests on larger vertical test pieces. Summary of the invention

[0007] The present invention aims at the problem that when an array air atomizing nozzle is used to spray a large vertical test piece and an ice coating test is performed on the test piece surface in a low temperature environment, since the spray droplets are greatly affected by gravity, most of the droplets will fall on the ground in front of the spray, and some droplets will follow the airflow to the two sides of the vertical test piece, resulting in a small amount of droplets hitting the surface of the test piece and a thin ice coating layer. A control method for a spray icing system in an ice coating test is proposed, and the scheme is specifically as follows:

[0008] A control method for a spray icing system in an icing test, the method comprising:

[0009] S1: The test chamber is placed inside a low-temperature environment. Temperature sensors are provided inside the low-temperature environment and inside the test chamber. The temperature sensors feed back temperature measurement signals to the PLC.

[0010] S2: Calculate the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber according to the temperature measurement signal obtained by the industrial computer PLC;

[0011] S3: Calculate the amount of circulating air that needs to be introduced into the test chamber based on the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber;

[0012] S4: Select a fan according to the circulating air volume, form a circulating fan, and start the circulating fan;

[0013] S5: When the temperature in the test chamber reaches the preset temperature, the background fan array is turned on;

[0014] S6: The icing test begins. The valves of the water and air supply pipelines are opened. Compressed air and low-temperature ultrapure water are provided by the air compressor and water pump respectively and sprayed out through the nozzle to form a cloud. The circulating fan works continuously to provide the cooling capacity required for the cloud icing test.

[0015] Furthermore, a preferred method is proposed, wherein the amount of circulating air to be introduced into the test chamber is calculated according to the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber in step S3, including:

[0016] The maximum heat release of the cloud and fog simulation test was obtained through theoretical calculation;

[0017] Select the minimum temperature difference between the air in the low temperature environment outside the test chamber and the air in the test chamber;

[0018] Thermodynamic calculations are performed based on the minimum temperature difference to determine the maximum amount of circulating air required. Due to different test conditions, the amount of heat released during the actual test is different. The frequency converter is used to adjust the operating frequency of the fan in real time to stabilize the temperature in the test chamber within the range of ±1°C of the set value.

[0019] The thermodynamic calculation formula is:

[0020] Q=mc p ΔT

[0021] Where Q is the amount of heat absorbed (or released) by the object (J); m is the mass of the object (kg); c p is the specific heat capacity at constant pressure [J / (kg·K)]; ΔT is the change in temperature before and after the object absorbs (or releases) heat.

[0022] Furthermore, a preferred embodiment is proposed, wherein step S3 further comprises:

[0023] The low temperature environment temperature is taken as the air temperature in the test chamber minus 10~15℃.

[0024] Furthermore, a preferred method is proposed, in step S4, a fan is selected according to the amount of circulating air to form a circulating fan, specifically:

[0025] According to the circulating air volume, divided by the number of circulating fans, the air volume of a single fan is obtained and the fan is selected.

[0026] Furthermore, a preferred embodiment is proposed, in which the preset temperature in step S5 is -5°C, -10°C, -15°C, or -20°C.

[0027] Furthermore, a preferred method is proposed, in step S6, a PID (proportional-integral-differential) operation is performed by an industrial computer PLC to control the opening of the valves of the water supply and gas supply pipelines.

[0028] Furthermore, a preferred method is proposed, wherein step S6 further includes controlling the cloud flow rate, specifically:

[0029] Calculate the maximum wind speed based on the fan's power frequency air volume and flow cross-sectional area;

[0030] Perform linear differentiation of the operating frequency from 0 Hz to 50 Hz to obtain a corresponding table between wind speed and fan operating frequency;

[0031] During the test, the corresponding table of wind speed and fan operating frequency is queried according to the required background wind speed, and the corresponding fan operating frequency is set to obtain the required cloud flow rate.

[0032] Furthermore, a preferred embodiment is proposed, wherein the method further comprises reducing the concentration of air mist entering the low-temperature environment from the test chamber by a defogger, specifically:

[0033] Set the defogger start temperature. When the temperature measured by the temperature sensor at the defogger inlet is lower than -3°C, the defogger starts heating. When it is higher than 3°C, the heating stops.

[0034] Furthermore, a preferred embodiment is proposed, wherein the demister is composed of three groups of 5.4kW 50W / m electric heating cables, and the outer shell of the heating cables is made of AlMg3 rust-proof aluminum alloy material.

[0035] Furthermore, a preferred embodiment is proposed, wherein the spray icing system comprises:

[0036] Test chamber, induced draft fan, exhaust fan, background fan array, honeycomb panel, screen, spray rack and demister;

[0037] The test chamber is provided with an induced draft fan on the left side and an exhaust fan and a demister on the right side;

[0038] The background fan array, honeycomb panel, screen and spray rack are placed in the test chamber in sequence.

[0039] The present invention is beneficial in that:

[0040] The present invention solves the problem that when an array air atomizing nozzle is used to spray a large vertical test piece and an ice coating test is performed on the surface of the test piece in a low-temperature environment, since the spray droplets are greatly affected by gravity, most of the droplets will fall on the ground in front of the spray, and some droplets will follow the airflow to the two sides of the vertical test piece, resulting in a small amount of droplets hitting the surface of the test piece and a thin ice coating.

[0041] The present invention proposes a control method for a spray icing system in an icing test. The temperature is monitored in real time by setting temperature sensors in a low-temperature environment and in a test chamber, and the circulating air volume is calculated according to the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber. Then, a suitable type of fan is selected according to the circulating air volume to form a circulating fan. These measures are intended to ensure the temperature stability of the test environment and provide the necessary airflow environment for the spray system. When the temperature in the test chamber reaches the preset temperature, the background fan array is turned on and the icing test is started. At the same time, by opening the valve of the water supply and air supply pipeline, compressed air and low-temperature ultrapure water are provided by the corresponding equipment and sprayed through the nozzle to form a cloud. These control measures ensure that the spray system operates under environmental conditions with controllable parameters and the test is carried out effectively. The method increases the contact between the droplets and the surface of the test piece by controlling the temperature and airflow of the test environment and accurately controlling the operation of the spray system, thereby solving the problem of a thin ice layer on the surface of the test piece and improving the effect and reliability of the icing test.

[0042] The present invention proposes a control method for a spray icing system in an icing test. By controlling the background fan array, a controllable airflow environment is formed around the test piece, so that more sprayed droplets hit the surface of the test piece, increasing the number of droplets frozen into ice. The background wind volume is calculated based on the background wind speed of 2 to 5 m / s and the flow cross-sectional area, and a suitable background fan operating frequency is selected to ensure that the ice layer can cover the entire surface of the test piece during the test and obtain a thicker ice layer. Through steps S1 to S6, the surface of the test piece can be covered with more droplets, thereby more accurately simulating the icing condition of the test piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A flow chart of a control method for a spray icing system in an icing test according to the first embodiment;

[0044] Figure 2 This is a schematic diagram of reducing the cloud concentration by the demister described in Implementation Mode 8;

[0045] Figure 3 Schematic diagram of a spray icing system in an icing test according to Embodiment 10;

[0046] Figure 4 Schematic diagram of the connection relationship between various electrical equipment in the spray icing system in the icing test described in Implementation Example 10. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0048] Implementation method 1, see Figure 1 The present embodiment is described as follows. A control method for a spray icing system in an icing test is described in the present embodiment, and the method comprises:

[0049] S1: The test chamber is set inside the low-temperature environment. Temperature sensors are provided inside the low-temperature environment and inside the test chamber. The temperature sensors feed back the temperature measurement signals to the PLC.

[0050] S2: Calculate the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber according to the temperature measurement signal obtained by the industrial computer PLC;

[0051] S3: Calculate the amount of circulating air that needs to be introduced into the test chamber based on the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber;

[0052] S4: Select a fan according to the amount of circulating air to form a circulating fan;

[0053] S5: When the temperature in the test chamber reaches the preset temperature, the background fan array is turned on;

[0054] S6: The icing test begins. The valves of the water and air supply pipelines are opened. Compressed air and low-temperature ultrapure water are provided by the air compressor and water pump respectively and sprayed out through the nozzle to form a cloud. The circulating fan works continuously to provide the cooling capacity required for the cloud icing test.

[0055] Among them, the induced draft fan and the exhaust fan form a circulating fan, whose main function is to introduce the cold air outside the test cabin into the cabin to achieve cabin cooling. Figure 3 As shown, the fan array placed on the left side of the honeycomb panel is a background fan array, which is used to provide a background wind of 2 to 5 m / s to assist in the transportation of clouds and fog.

[0056] The method described in this embodiment controls the background fan array to form a controllable airflow environment around the test piece, so that the sprayed droplets hit the surface of the test piece more and the number of ice-covered droplets increases. The background wind volume is calculated based on the background wind speed of 2 to 5 m / s and the flow cross-sectional area, and a suitable background fan operating frequency is selected to ensure that the ice layer will cover the entire surface of the test piece during the test and achieve uniform ice coverage. Through steps S1 to S6, the surface of the test piece can be covered with more droplets, thereby more accurately simulating the icing condition of the test piece and improving the test effect and reliability.

[0057] Specifically, there is 1 temperature sensor in the low-temperature environment, 4 temperature sensors and 4 humidity sensors in the test chamber, the humidity sensor is used to monitor the humidity data around the vertical test piece in the test chamber (humidity is an important factor affecting the results of the icing test), and the 4 temperature sensors and 4 humidity sensors are used to monitor the temperature and humidity parameters around the vertical test piece in the test chamber. After the temperature and humidity measurement values ​​reach the test parameters, the test can be started, and the temperature and humidity data are monitored and saved in real time during the test. Temperature sensors are installed in the low-temperature environment and the test chamber to monitor and record the temperature of the test environment in real time. The industrial computer PLC obtains the signal of the temperature sensor, calculates the difference between the measured value and the set value of the air temperature in the test chamber, and the temperature difference between the air inside and outside the test chamber. The difference between the measured value and the set value of the air temperature in the test chamber reflects the deviation between the actual temperature and the expected temperature. Using the temperature difference, the amount of circulating air to be introduced into the test chamber is calculated through a pre-set relationship. It should be noted that the amount of circulating air that needs to be introduced into the test cabin according to the temperature difference between the air inside and outside the test cabin described in this embodiment does not refer to the process of gradually cooling the cabin by turning on the circulating fan before the icing test, but the amount of circulating air that needs to be introduced into the test cabin according to the temperature difference between the air inside and outside the test cabin during the icing test. The reason is that before the start of the icing test, the room temperature air in the cabin is relatively high and has a large heat capacity. If the amount of circulating air calculated by cooling the room temperature air in the test cabin to the test set temperature within a few seconds will be very large, and it is not necessary in actual operation. This calculation is based on the theoretical model of thermodynamics, taking into account factors such as constant pressure specific heat capacity and temperature difference. Among them, the basis for calculating the maximum amount of circulating air is: using the cold air introduced from outside the test cabin into the test cabin, absorbing the heat released by the cooling of the spray in the icing test, and then bringing it to the outside of the test cabin to achieve the maintenance of the low temperature in the cabin. According to the calculated amount of circulating air, select a suitable fan to form a circulating fan. (The above is the function of the background air fan) When the temperature in the test cabin reaches the preset test temperature, the system will automatically turn on the background fan array to start the airflow environment preparation work before the test. With the background fan array running, the valves of the water and air supply pipelines are opened, and the air compressor and water pump provide compressed air and ultrapure water, which are sprayed through the nozzle to form a cloud. The droplets hit the surface of the test piece under the action of the airflow to carry out the icing test.

[0058] In this embodiment, by monitoring the temperature in real time and comparing it with the set value, the system can ensure that the temperature of the test environment meets the expectations. This helps to accurately calculate the maximum amount of circulating air. The maximum amount of circulating air calculated based on the temperature difference ensures that sufficient airflow is generated during the test to achieve cooling. Select a suitable background wind fan array to ensure that a controllable airflow environment is formed around the test piece, so that the sprayed droplets can hit the surface of the test piece more. When the temperature in the test chamber reaches the preset temperature, turn on the background fan array to ensure that there is an appropriate airflow environment at the beginning of the test. After the airflow environment is ready, turn on the water and air supply pipelines to form a cloud spray, and the droplets cover the surface of the test piece under the action of the airflow.

[0059] Embodiment 2: This embodiment further limits the control method of the spray icing system in the icing test described in Embodiment 1. The step S3 calculates the circulating air volume in the test chamber according to the difference between the temperature measurement value and the set value, including:

[0060] The maximum heat release of the cloud and fog simulation test was obtained through theoretical calculation;

[0061] Select the minimum temperature difference between the low temperature environment outside the test chamber and the test chamber;

[0062] Perform thermodynamic calculations based on the minimum temperature difference to determine the maximum amount of circulating air required;

[0063] The thermodynamic calculation formula is:

[0064] Q=mc p ΔT

[0065] Where Q is the amount of heat absorbed (or released) by the object (J); m is the mass of the object (kg); c p is the specific heat capacity at constant pressure [J / (kg·K)]; ΔT is the change in temperature before and after the object absorbs (or releases) heat.

[0066] In practical applications, the calculation of the maximum circulating air volume must first determine the maximum heat release of the spray in each working condition of the icing test. For the open ice condition in the icing test, the maximum spray volume is 823.2L / h, and the water temperature is 5°C. The maximum compressed air flow rate is 840NL / min, and the air temperature is 20°C. The lowest temperature in the test chamber is -20°C. After entering the test chamber, the water first cools down to 0°C, then solidifies, and finally changes from 0°C ice to -20°C ice. After entering the test chamber, the compressed air cools down from 20°C to -20°C. The constant pressure specific heat capacity of water is 4.2kJ / kg / °C, the latent heat of solidification is 335kJ / kg, and the constant pressure specific heat capacity of ice is 2.1kJ / kg / °C. The constant pressure specific heat capacity of compressed air is 1.005kJ / kg / °C.

[0067] According to the heat release formula:

[0068] Q=mc p ΔT

[0069] Where Q is the amount of heat absorbed (or released) by the object (J); m is the mass of the object (m); c p is the specific heat capacity at constant pressure [J / (kg·K)]; ΔT is the change in temperature before and after the object absorbs (or releases) heat.

[0070] It is calculated that 823.2L / h of water at 5℃ and 840NL / min of compressed air at 20℃ enter the test chamber and release heat to the set temperature of the test chamber (-20℃). The total heat released per unit time is Q=86.94kJ, that is, the calorific value is 86.94kW. The temperature difference between the air inside and outside the test chamber is 10℃, that is, the inlet cold air temperature is -30℃ and the outlet temperature is -20℃. According to the heat absorption formula Q=mc p ΔT, then 6.66m is needed 3 / s(23955m 3 / h) of circulating air volume flow can remove 86.94kW of heat generated in the cabin.

[0071] This embodiment calculates the maximum heat released by the experiment through theoretical calculation, and selects the minimum temperature difference between the low temperature environment outside the test chamber and the test chamber based on this heat, and then performs relevant thermodynamic calculations to determine the required maximum circulating air volume. This method determines the required circulating air volume more accurately, ensuring that the cloud formed in the test can meet the requirements of the icing test. The maximum circulating air volume is determined by considering thermodynamic factors such as heat release and temperature difference. This comprehensive consideration can better adapt to the complexity of the test environment and ensure the accuracy and reliability of the test.

[0072] Specifically, this embodiment first obtains the maximum heat released in the experiment through theoretical calculation. This heat is an important parameter in the icing test, which affects the temperature change and ice formation during the test. Then, the minimum temperature difference between the low-temperature environment outside the test chamber and the test chamber is selected according to the maximum heat. This temperature difference can affect the air circulation speed and heat transfer rate in the test environment. After determining the minimum temperature difference, relevant thermodynamic calculations are performed to determine the required amount of circulating air. This calculation process takes into account factors such as the air flow speed and temperature distribution to ensure that the low-temperature air flow can evenly cool down the test piece and meet the temperature control accuracy requirements of the icing test.

[0073] This embodiment further improves the accuracy and reliability of the icing test by accurately calculating the maximum circulating air volume and comprehensively considering thermodynamic and fluid dynamic factors to ensure that the formed cloud can be cooled sufficiently and evenly, thereby obtaining more reliable test results.

[0074] Embodiment 3: This embodiment further limits the control method of the spray icing system in the icing test described in embodiment 1, and the step S3 also includes: subtracting 10-15° C. from the test chamber temperature and setting it as the low temperature environment temperature.

[0075] This embodiment can more accurately control the temperature of the low-temperature environment by subtracting a certain value from the temperature of the test chamber and setting it as the temperature of the low-temperature environment, so that it has a certain difference with the temperature of the test chamber. This difference helps to form environmental conditions that are more suitable for icing tests and improve the controllability and accuracy of the test. By setting the temperature of the low-temperature environment, the test system can be made more stable during operation. Temperature stability is crucial to the temperature control accuracy and droplet cooling rate in icing tests, so this method can improve the stability of the test system and ensure the reliability of the test results.

[0076] The temperature of the test chamber is set as the temperature of the low-temperature environment after subtracting a certain value. In this way, a certain temperature difference can be formed between the low-temperature environment and the test chamber. This temperature difference can affect the circulation speed of the air and the heat transfer rate in the test environment, and then affect the freezing rate and effect of the fog on the surface of the test piece. This embodiment further optimizes the temperature control of the test system and improves the controllability and accuracy of the test. By accurately adjusting the temperature of the low-temperature environment so that it has a certain difference with the temperature of the test chamber, it is conducive to forming environmental conditions suitable for icing tests. This can ensure that the fog formed in the test can obtain a better freezing effect and obtain more reliable test results.

[0077] Embodiment 4: This embodiment further limits the control method of the spray icing system in the icing test described in embodiment 1. In step S4, a fan is selected according to the amount of circulating air to form a circulating fan, specifically:

[0078] Based on the maximum circulating air volume, divided by the number of circulating fans, the air volume of a single fan is obtained and the fan is selected.

[0079] Embodiment 5: This embodiment further limits the control method of the spray icing system in the icing test described in embodiment 1, and the preset temperature in step S5 is -5°C, -10°C, -15°C, and -20°C.

[0080] Corresponding to different test conditions, such as -5℃ should be selected for open ice conditions, and -15 or -20℃ should be selected for frost conditions. Adjustment of different conditions can be achieved by changing the temperature of the test space.

[0081] Embodiment 6: This embodiment further limits the control method of the spray icing system in the icing test described in embodiment 1. In step S6, the PID (proportional-integral-differential) operation is performed by the industrial computer PLC to control the opening of the valve of the water supply and air supply pipelines.

[0082] Specifically, before the icing test begins, the circulating fan should be turned on to introduce external cold air into the test chamber. After a period of gradual cooling, the test temperature is reached and the circulating fan stops running or switches to low-frequency operation.

[0083] Open the background fan array and the air and water supply pipeline valves, and start the spray and icing test.

[0084] During the icing test, the temperature sensor in the test cabin monitors the temperature changes in the test cabin in real time, and adjusts the operating frequency of the fan in real time according to the relationship between the monitoring value and the set value. There are two temperature control methods: hysteresis control and PID adjustment. Among them, hysteresis control means that when the detection value exceeds the set value within the range of ±1°C, if the monitoring temperature-set temperature>1°C, the operating frequency of the circulating fan is increased or the full frequency is operated through the inverter to increase the amount of circulating cold air; if the monitoring temperature-set temperature is <1°C, the operating frequency of the circulating fan is lowered or stopped through the inverter to reduce the amount of circulating cold air. Similarly, the cold air temperature outside the test cabin must also be maintained within the range of -10°C±1°C of the set temperature in the test cabin. PID adjustment can automatically adjust the fan operating frequency according to the temperature change trend, and the temperature control accuracy is higher.

[0085] The PID (proportional-integral-differential) algorithm used in this embodiment can more accurately control the opening of the valves in the water supply and gas supply pipelines. The PID controller can adjust the opening of the valve according to the real-time pressure feedback signal, so that the system can respond quickly and accurately to different working conditions and requirements, improving the stability and control accuracy of the system. The PID controller is adaptive and can automatically adjust the control parameters according to the actual operating conditions of the system, adapt to different working environments and load changes, and improve the applicability and reliability of the system. It should be noted that the control of the valves in the water supply and gas supply pipelines is only completed by monitoring and controlling the pipeline pressure.

[0086] PID controller is a classic control algorithm, which consists of three parts: proportional (P), integral (I), and differential (D). The proportional part controls the valve opening according to the difference between the target value and the actual value, the integral part adjusts the control amount according to the accumulation of errors, and the differential part improves the dynamic response capability of the system according to the rate of error change. Through the synergistic effect of these three parts, the PID controller can achieve precise adjustment of the valve opening. In this embodiment, the PID control algorithm is used to achieve precise control of the valve opening of the water supply and air supply pipelines, thereby optimizing the working efficiency and performance of the spray icing system. By automatically adjusting the valve opening, it can be ensured that the spray system can be adjusted in real time according to changes in the upstream pressure, keeping the system running in the best state, improving the accuracy and reliability of the test, and reducing energy consumption and resource waste.

[0087] Embodiment 7: This embodiment further limits the control method of the spray icing system in the icing test described in Embodiment 1, and the step S6 further includes controlling the cloud flow rate, specifically:

[0088] Calculate the maximum wind speed based on the fan's power frequency air volume and flow cross-sectional area;

[0089] Perform linear differentiation of the operating frequency from 0 Hz to 50 Hz to obtain a corresponding table between wind speed and fan operating frequency;

[0090] During the test, the corresponding table of wind speed and fan operating frequency is queried according to the required background wind speed, and the corresponding fan operating frequency is set to obtain the required cloud flow rate.

[0091] This implementation method can achieve precise control of the cloud and fog flow rate by calculating the maximum wind speed based on the fan power frequency air volume and the flow cross-sectional area, and then performing linear differentiation of the operating frequency from 0Hz to 50Hz to obtain a corresponding table of wind speed and fan operating frequency. This method can ensure that the corresponding fan operating frequency is set according to the required background wind speed during the test, thereby obtaining the required cloud and fog flow rate, thereby improving the adjustability and stability of the system.

[0092] Specifically, by measuring the air volume at the working frequency of the fan and combining it with the area of ​​the flow section, the maximum wind speed that the fan can provide at the maximum operating frequency can be calculated. This step is to determine the upper limit of the performance of the fan and provide basic data for subsequent wind speed control. The operating frequency of the fan is linearly differentiated from 0Hz to 50Hz, and a correspondence table between the wind speed and the operating frequency of the fan can be obtained. The correspondence table can be used to query the corresponding fan operating frequency according to the required background wind speed during the test. During the test, according to the required background wind speed, the corresponding fan operating frequency can be set by querying the previously obtained correspondence table of wind speed and fan operating frequency, so as to achieve the required cloud flow rate. This embodiment accurately controls the cloud flow rate, so that the spray icing system can adjust the cloud flow rate according to actual needs to meet the requirements under different test conditions. By adjusting the operating frequency of the fan, the speed of the cloud can be controlled, thereby achieving precise control of the icing process, improving the controllability and accuracy of the test, and ensuring the reliability of the test results.

[0093] Implementation Method 8: See Figure 2 This embodiment further defines the control method for a spray icing system in an icing test described in Embodiment 1, wherein the method further includes reducing the cloud concentration by a defogger, specifically:

[0094] Set the defogger start temperature. When the temperature measured by the temperature sensor at the defogger inlet is lower than -3°C, the defogger starts heating. When it is higher than 3°C, the heating stops.

[0095] In this embodiment, a defogger is introduced to adjust the cloud concentration. According to the measurement results of the temperature sensor, the heating state of the defogger is controlled in real time, thereby effectively reducing the cloud concentration. Such a control method can more flexibly adjust the cloud concentration in the icing test to meet the requirements of different test conditions.

[0096] Specifically, a threshold temperature of -3°C is set. When the temperature measured by the temperature sensor at the inlet of the defogger is lower than this threshold, it means that the ambient temperature is low, and the low-temperature fog freezes on the surface of the defogger, which is easy to freeze and block the airflow channel. It is suitable to melt and defog by heating the defogger to maintain the defog function of the defogger. A temperature sensor is used to monitor the temperature at the inlet of the defogger. When the temperature is lower than the set start temperature (-3°C), the heating function of the defogger is started; when the temperature is higher than 3°C, the heating is stopped. This can avoid wasting energy under suitable temperature conditions. By introducing a defogger, the working state of the defogger is adjusted in real time according to the temperature at the inlet of the defogger, thereby effectively reducing the fog concentration. This control method can flexibly respond to the needs under different temperature conditions during the test process, ensuring more accurate and controllable results in the icing test. By timely reducing the fog concentration, it can be ensured that the fog concentration in the test space does not change with the test time, such as fog accumulation, making the test more realistic and improving the reliability of the test data. At the same time, by stopping heating under high temperature conditions, unnecessary energy waste can also be avoided.

[0097] Embodiment 9. This embodiment further limits the control method of the spray icing system in the icing test described in embodiment 1. The defogger is composed of three groups of 5.4kW 50W / m electric heating cables, and the heating cable casing is made of AlMg3 rust-proof aluminum alloy material.

[0098] This embodiment uses three groups of 5.4kW 50W / m electric heating cables, which can provide more heating power than a single group of electric heating cables, and can be divided into three groups to achieve more precise control to meet the heating needs under different conditions. The AlMg3 rust-proof aluminum alloy material is used as the heating cable shell, which has good rust-proof performance, can increase the service life of the electric heating system and reduce maintenance costs.

[0099] The defogger is composed of three groups of 5.4kW 50W / m electric heating cables. The power of each group of electric heating cables is 5.4kW, and the length of the electric heating cables is 50W per meter. Such a design can provide higher heating power and speed up the heating speed of the defogger. The shell of the heating cable is made of AlMg3 rust-proof aluminum alloy material, which has good thermal conductivity and corrosion resistance, can effectively conduct heating power, and can resist corrosion in the environment, ensuring the stability and reliability of the electric heating system. This embodiment improves the heating efficiency and stability of the defogger by optimizing the composition and materials of the electric heating cable, and realizes more sophisticated heating control. This can more effectively reduce the cloud concentration, improve the data accuracy and repeatability of the icing test, and ensure the reliability of the test results. At the same time, the use of rust-proof aluminum alloy materials can also extend the service life of the electric heating system and reduce maintenance costs.

[0100] Implementation Method 10: See Figure 3 and Figure 4 This embodiment further defines the control method of the spray icing system used in the icing test described in the first embodiment, and the spray icing system includes:

[0101] Test chamber, induced draft fan, exhaust fan, background fan array, honeycomb panel, screen, spray rack and demister;

[0102] The test chamber is provided with an induced draft fan on the left side and an exhaust fan and a demister on the right side;

[0103] The background fan array, honeycomb panel, screen and spray rack are sequentially arranged inside the test chamber.

[0104] The structural position relationship of the spray icing system in the icing test is as follows: Figure 3 As shown, the induced draft fan and the exhaust fan form a circulating fan, whose main function is to introduce cold air outside the test cabin into the test cabin to achieve cooling in the test cabin. The fan array placed on the left side of the honeycomb panel is the background fan array, which is used to provide a background wind of 2 to 5 m / s to assist in the transportation of clouds and fog. In actual applications, the aerodynamic dimensions of the test cabin are a cross-section of 4.3m×4.66m, a length of 9.7m, and a pressure of 1atm, so the volume of the test cabin is 194m 3 Considering the impact of the test chamber volume and airflow backflow, the maximum airflow velocity of the uniform wind generator is designed to be 5.0m / s. The internal dimensions of the uniform wind generator are 2.35m×3.29m=7.73m 2 , the total air flow is 5.0×7.73×3600=140000m 3 / h. The number of fans is 35, and the flow rate of each fan is 140000 / 35=4000m 3 / h. Use industrial low-noise exhaust fan, model YWF-4E-400, air volume 4800m 3 / h, power 190W, total power of background fan array is 190W×35=6650W, 7 2.2kW inverters are used, 1 inverter controls the speed of 5 fans. The power requirement is based on a certain margin, 5 fans use 1 2.2kW inverter. The maximum wind speed is 6.03m / s by using the fan air volume and speed.

[0105] The connection relationship between various electrical equipment is as follows Figure 4 As shown. Placing the induced draft fan, exhaust fan and demister on the left and right sides of the test chamber respectively helps to distribute the wind force and the demisting effect more evenly, and improves the efficiency of the entire system. Placing the background fan array, honeycomb panel, screen and spray rack in the test chamber in sequence optimizes the structural layout of the icing system, making the spraying and ventilation process smoother and improving the stability and controllability of the system.

[0106] The induced draft fan is set on the left side of the test chamber, and the exhaust fan and demister are set on the right side of the test chamber, which can evenly blow wind and perform demisting treatment, avoiding the situation where one side has good effect and the other side has poor effect, and improving the balance and stability of the whole system. The background fan array, honeycomb plate, screen and spray rack are arranged in the test chamber in sequence. This design makes the whole process from induced draft, filtration, spraying to demisting smoother. The background fan array provides wind, the honeycomb plate and screen rectify the background wind to make it more uniform, the spray rack sprays water mist, and the demister processes the water mist to ensure that the cloud concentration in the test chamber will not gradually increase as the test proceeds. When the temperature in the test chamber reaches the set temperature, the background fan array is turned on to provide the set background wind speed, and the icing test begins. The valves of the water supply and air supply pipelines are opened, and the compressed air and low-temperature ultrapure water are provided by the air compressor and the water pump respectively and sprayed through the nozzle to form clouds. The size of the air duct behind the spray rack, the size of the honeycomb plate, and the size of the spray rack are determined according to the ice area on the surface of the test piece. According to the maximum compressed air flow rate of the nozzle, the maximum wind speed after the spray moves forward 1.0m does not exceed 0.01m / s. The nozzle spray speed is relatively small. Compared with the wind speed of 2 to 5m / s provided by the background fan array, the speed of the nozzle spray after 1.0m can be ignored. The spray wind speed at the nozzle is related to the compressed air flow rate. The cloud and fog flow rate is mainly adjusted by the operating frequency of the background fan array: the maximum wind speed is calculated according to the fan power frequency air volume and the cross-sectional area of ​​the flow, corresponding to the operating frequency of 50Hz, the wind speed of 0Hz is zero, and the linear difference is obtained to obtain the corresponding table of wind speed and fan operating frequency. During the test, the fan operating frequency is queried and set according to the background wind speed. The cloud and fog working condition of the test system described in this embodiment can simulate snowy days below 0℃ and freezing rain weather around 0℃ within 4 wind speeds (<7.9m / s). The purpose of this embodiment is to improve the efficiency and stability of the spray icing system through distributed settings and process optimization, so that it can better control the icing process and defogging effect in the icing test. Through reasonable structural layout and process design, the accuracy and repeatability of test data can be ensured, the scientificity and reliability of the test can be improved, and better technology can be provided for the implementation of icing tests.

[0107] The above further describes in detail the technical solution provided by the present invention in conjunction with the accompanying drawings in order to highlight the advantages and benefits, and is not intended to be a limitation of the present invention. Any modification, combination of implementation modes, improvement and equivalent substitution of the present invention within the spirit and scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control method for a spray icing system in an icing test, characterized in that: The method comprises: S1: The test chamber is placed inside a low-temperature environment. Temperature sensors are provided inside the low-temperature environment and inside the test chamber. The temperature sensors feed back temperature measurement signals to the PLC. S2: Calculate the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber according to the temperature measurement signal obtained by the industrial computer PLC; S3: Calculate the amount of circulating air that needs to be introduced into the test chamber based on the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber; S4: Select a fan according to the circulating air volume, form a circulating fan, and start the circulating fan; S5: When the temperature in the test chamber reaches the preset temperature, the background fan array is turned on; S6: The icing test begins. The valves of the water and air supply pipelines are opened. Compressed air and low-temperature ultrapure water are provided by the air compressor and water pump respectively and sprayed out through the nozzle to form a cloud. The circulating fan works continuously to provide the cooling capacity required for the cloud icing test.

2. A control method for a spray icing system in an icing test according to claim 1, characterized in that: The step S3 calculates the amount of circulating air that needs to be introduced into the test chamber according to the difference between the temperature measurement value in the test chamber and the set value and the temperature difference between the air inside and outside the test chamber, including: The maximum heat release of the cloud and fog simulation test was obtained through theoretical calculation; Select the minimum temperature difference between the air in the low temperature environment outside the test chamber and the air in the test chamber; Thermodynamic calculations are performed based on the minimum temperature difference to determine the maximum amount of circulating air required. Due to different test conditions, the amount of heat released during the actual test is different. The frequency converter is used to adjust the operating frequency of the fan in real time to stabilize the temperature in the test chamber within the range of ±1°C of the set value. The thermodynamic calculation formula is: in, Q The heat absorbed or released by an object (J); m is the mass of the object (kg); c p is the specific heat capacity at constant pressure [J / (kg·K)]; ΔT The change in temperature of an object before and after it absorbs or releases heat.

3. A control method for a spray icing system in an icing test according to claim 2, characterized in that: The step S3 also includes: the low temperature environment temperature is taken as the air temperature in the test chamber minus 10-15°C.

4. The control method for a spray icing system in an icing test according to claim 1, characterized in that: In step S4, a fan is selected according to the amount of circulating air to form a circulating fan, specifically: According to the circulating air volume, divided by the number of circulating fans, the air volume of a single fan is obtained and the fan is selected.

5. The control method for a spray icing system in an icing test according to claim 1, characterized in that: The preset temperatures in step S5 are -5°C, -10°C, -15°C, and -20°C.

6. The control method for a spray icing system in an icing test according to claim 1, characterized in that: In step S6, PID calculation is performed by the industrial computer PLC to control the opening of the valves of the water supply and gas supply pipelines.

7. The control method for a spray icing system in an icing test according to claim 1, characterized in that: The step S6 also includes controlling the cloud flow rate, specifically: Calculate the maximum wind speed based on the fan's power frequency air volume and flow cross-sectional area; Perform linear differentiation of the operating frequency from 0 Hz to 50 Hz to obtain a corresponding table between wind speed and fan operating frequency; During the test, the corresponding table of wind speed and fan operating frequency is queried according to the required background wind speed, and the corresponding fan operating frequency is set to obtain the required cloud flow rate.

8. The control method for a spray icing system in an icing test according to claim 1, characterized in that: The method further includes reducing the cloud concentration by a demister, specifically: Set the defogger start temperature. When the temperature measured by the temperature sensor at the defogger inlet is lower than -3°C, the defogger starts heating. When it is higher than 3°C, the heating stops.

9. A control method for a spray icing system in an icing test according to claim 8, characterized in that: The demister is composed of three groups of 5.4kW 50W / m electric heating cables, and the heating cable casing is made of AlMg3 rust-proof aluminum alloy material.

10. The control method of a spray icing system in an icing test according to claim 1, characterized in that: The spray icing system comprises: Test chamber, induced draft fan, exhaust fan, background fan array, honeycomb panel, screen, spray rack and demister; The test chamber is provided with an induced draft fan on the left side and an exhaust fan and a demister on the right side; The background fan array, honeycomb panel, screen and spray rack are placed in the test chamber in sequence.

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