A low temperature humidity control system for automobile environmental wind tunnel

Abstract

The present invention relates to the field of automobile environmental wind tunnels and discloses a low-temperature humidity control system for an automobile environmental wind tunnel, comprising an air duct, a dehumidification section and a low-temperature humidity control section, wherein the dehumidification section is connected to the low-temperature humidity control section, and the low-temperature humidity control section is connected to the air duct; the low-temperature humidity control section comprises a cryogenic coil, a plurality of steam nozzles, a steam regulating valve, an inlet air temperature sensor, an inlet air humidity sensor, an inlet air volume sensor, an inlet air pressure sensor, an outlet air temperature sensor and an outlet air humidity sensor, and the steam nozzles are all connected to the steam regulating valve; a main heat exchanger and an air duct humidity sensor are provided in the air duct; and the system also comprises a controller, wherein the inlet air temperature sensor, the inlet air humidity sensor, the inlet air volume sensor, the inlet air pressure sensor, the outlet air temperature sensor and the outlet air humidity sensor transmit collected data to the controller, and the controller controls the valve opening of the steam regulating valve, so as to solve the problem that it is difficult to accurately control the humidity in existing automobile environmental wind tunnels under low-temperature conditions.

Description

Technical Field

[0001] The present invention relates to the field of automobile environmental wind tunnels, and in particular to a low-temperature humidity control system for an automobile environmental wind tunnel. Background Art

[0002] Automotive environmental wind tunnels are crucial testing rooms in vehicle R&D, simulating real-world climates to test vehicle performance. Humidity simulation is a core system within these systems, designed to simulate real-world humidity. Currently, most automotive environmental wind tunnels can simulate humidity at both room and high temperatures, achieving a relative humidity range of 5% to 95% with a control accuracy of ±3%. However, in cryogenic environments (-40°C to 0°C), these tunnels cannot precisely control humidity and can only perform low-temperature dehumidification. Consequently, the humidity within these tunnels decreases rapidly under low-temperature conditions, making it difficult to maintain a constant value.

[0003] Patent application number 201711480498.6 discloses a low-temperature air-cooled heat exchanger performance monitoring test bench. Humidity is controlled in a low-temperature environment with a wind speed of 0.3 to 10 m / s. Humidity is adjusted by directly spraying steam into the wind tunnel. However, due to the high wind speeds in automotive environmental wind tunnels, which can reach 200 to 250 km / h, such high wind speeds blowing through the steam nozzles can cause severe stratification between the steam ejected from the steam nozzles and the wind tunnel air, resulting in extremely poor humidity uniformity. Furthermore, the steam nozzles increase wind resistance within the wind tunnel, significantly increasing the power of the main fan, which significantly compromises the safety and wind speed simulation of the entire automotive environmental wind tunnel. Furthermore, the refrigerant oil temperature in the main heat exchanger is lower than the wind tunnel temperature. If humidity control is performed at low temperatures, such as -20°C and 90% operating conditions, the surface temperature of the main heat exchanger will be around -25°C. This can cause ice and blockage in the main heat exchanger, necessitating the suspension of heating and defrosting for a prolonged test period, leading to failure of the entire test. For example, the patent with application number: 201810132378.5 can only control humidity above 0°C. If this patent is directly used for humidity control under deep cold and low temperature conditions, there will be shortcomings: the air temperature in the large flow section is as low as 10°C. If steam is sprayed into the wind tunnel to adjust the humidity, the air temperature will be even higher. A large amount of high-temperature air entering the deep cold and low temperature wind tunnel will cause great temperature field disturbances, resulting in a decrease in temperature simulation performance.

[0004] The rapid development of new energy vehicles in recent years has led to comprehensive technological advancements in these vehicles. During the winter heating cycle of a pure electric vehicle's heat pump air conditioning system, the external heat exchanger acts as an evaporator, absorbing heat from the outside environment, while the internal condenser releases heat to the inside environment to achieve winter heating. Due to the low ambient temperature outside the vehicle in winter, if the surface temperature of the external heat exchanger is lower than the air dew point, moisture in the air will condense and form frost on the surface of the external heat exchanger. This frost will hinder the heat exchange between the external heat exchanger and the external environment, hindering the normal operation of the system. In severe cases, it may even prevent normal heating. Therefore, winter defrosting of pure electric vehicle heat pump air conditioning has become a must-solve issue in this field. Testing and verification of heat pump anti-frost control strategies has become a must-do test for automakers. This also urgently requires that automotive environmental wind tunnels have excellent low-temperature humidity control capabilities to better provide excellent environmental simulation for similar tests. Summary of the Invention

[0005] The present invention aims to provide a low-temperature humidity control system for an automotive environmental wind tunnel to solve the problem that existing automotive environmental wind tunnels are difficult to accurately control humidity under low-temperature conditions.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solutions: a low-temperature humidity control system for an automobile environmental wind tunnel, comprising an air duct, a dehumidification section and a low-temperature humidity control section, the dehumidification section being connected to the low-temperature humidity control section, and the low-temperature humidity control section being connected to the air duct; the low-temperature humidity control section comprising a cryogenic coil, a plurality of steam nozzles, a steam regulating valve, an inlet temperature sensor, an inlet humidity sensor, an inlet air volume sensor, an inlet air pressure sensor, an outlet air temperature sensor and an outlet air humidity sensor, and the steam nozzles are all connected to the steam regulating valve; a main heat exchanger and an air duct humidity sensor are provided in the air duct; and the system also comprises a controller, the inlet air temperature sensor, the inlet air humidity sensor, the inlet air volume sensor, the inlet air pressure sensor, the outlet air temperature sensor and the outlet air humidity sensor transmit the collected data to the controller, and the controller controls the valve opening of the steam regulating valve.

[0007] The benefits of this solution are as follows: 1. By adding a low-temperature humidity control section, the temperature of the incoming air is lowered to the same level as the wind tunnel test temperature and the air is humidified before being introduced into the wind tunnel. This prevents the addition of air from causing temperature fluctuations inside the wind tunnel in the deep cold wind tunnel environment, which could affect the accuracy of the vehicle wind tunnel test.

[0008] 2. The steam nozzle is placed in the low-temperature humidity control section. This changes the existing technique of injecting steam directly into the wind tunnel during humidity control. This solves the problem of injecting high-temperature steam directly into a deep, low-temperature automotive environmental wind tunnel. This not only causes excessive wind speed inside the automotive environmental wind tunnel, which causes stratification of the added steam and makes it difficult for the steam to mix evenly with the air, but also solves the problem of the steam nozzle increasing the wind resistance inside the wind tunnel. To ensure the test wind speed, the main fan power needs to be increased, which may lead to safety hazards in wind tunnel testing.

[0009] 3. Since the steam regulating valve is set in the low-temperature humidity control section, in order to ensure timely response between the humidity in the wind tunnel and the opening of the steam regulating valve, the temperature, humidity and other data collected in the air duct and the low-temperature humidity control section are used to determine the opening preset value and correction value, and the opening of the steam regulating valve is adjusted dynamically in real time. This overcomes the long length of the air duct in the entire low-temperature humidity control section and the relatively long distance from the air inlet to the installation position of the air duct humidity sensor. This leads to large delays and large inertia when correcting the steam regulating valve opening, making it take a long time from the action of the steam regulating valve to the response of the wind tunnel humidity, and extremely difficult to control the humidity between the steam regulating valve and the wind tunnel, thus achieving precise control of the humidity inside the wind tunnel.

[0010] Preferably, the steam nozzles are all arranged on a side of the cryogenic coil close to the dehumidification section, and the steam nozzles are all facing the direction of air inlet.

[0011] The beneficial effects of this solution are as follows: the steam nozzles are all arranged on the side of the cryogenic coil close to the dehumidification section, so that the air is humidified first and then cooled, which can avoid the cooled air from coming into contact with the high-temperature steam, making it difficult to control the temperature of the fresh air; the direction of the steam nozzle spray is towards the direction of the air flow, so that the steam ejected from the steam nozzle can be fully and evenly mixed with the air flowing into the air duct, further ensuring the precise control of the low-temperature and humidity control of the wind tunnel.

[0012] Preferably, the dehumidification section further includes a hydrophobic antifreeze mechanism and a compensating fan. The hydrophobic antifreeze mechanism is arranged on both sides of the steam nozzle, and the compensating fan is arranged between the hydrophobic antifreeze mechanism and the cryogenic coil.

[0013] The beneficial effects of this solution are as follows: 1. During the humidification process of dry fresh air, a small amount of steam ejected from the steam nozzle will reach the inner surface of the air duct, causing some steam to condense and adhere. The hydrophobic antifreeze mechanism can collect and drain the condensed water, thereby preventing the condensed water from adhering to the inner surface of the air duct and being blown along the air duct to the surface of the cryogenic coil under the action of air flow, causing the surface of the cooling coil to freeze and affect the cooling effect of the cryogenic coil;

[0014] 2. The compensating fan is set at the rear end of the hydrophobic antifreeze mechanism. Since the use of the steam nozzle and the hydrophobic antifreeze mechanism will increase the wind resistance in the air duct, the added compensating fan can just compensate for this part of the pressure drop, thereby achieving the purpose of accurately controlling the wind pressure in the low-temperature and humidity control section; and, during the rotation process, the compensating fan can fully stir and mix the steam and air, thereby further improving the uniformity of the air humidity and preventing the surface of the cooling coil from being frozen due to excessive humidity in some areas.

[0015] Preferably, the dehumidification section also includes an electric heating device, a cryogenic coil temperature sensor and a cryogenic coil differential pressure sensor. The electric heating device is arranged on one side of the cryogenic coil, and the cryogenic coil temperature sensor and the cryogenic coil differential pressure sensor are both connected to the cryogenic coil.

[0016] The beneficial effects of this solution are as follows: 1. The cryogenic coil temperature sensor monitors the surface temperature of the cryogenic coil. The surface temperature of the cryogenic coil cannot be lower than the dew point temperature of the air in this state, otherwise the cryogenic coil will freeze. Therefore, the cryogenic coil temperature sensor can provide an early warning. When the monitored temperature is about to reach the dew point temperature, the steam control valve opening is adjusted in advance to limit steam entry, so that the dew point temperature in the low-temperature humidity control section is always higher than the monitoring value of the cryogenic coil temperature sensor, thereby preventing the cryogenic coil from freezing.

[0017] 2. A cryogenic coil differential pressure sensor is installed on the cryogenic coil to monitor the differential pressure between the main heat exchanger and the cryogenic coil. If ice blockage is detected in the main heat exchanger or cryogenic coil, a timely response can be made to close the steam regulating valve, start the electric heating device, and perform heating and de-icing operations to ensure the safety of the automotive environmental wind tunnel test.

[0018] Preferably, it also includes a small flow section, which includes a cooling coil and an air volume regulating valve.

[0019] The beneficial effects of this solution are: using cooling coils to initially cool the air in the small flow section can reduce the cooling load in the low-temperature and humidity control section, avoid the low-temperature and humidity control section from being loaded to cool down due to excessive air temperature, and cannot lower the air temperature to the same level as the test set temperature in the wind tunnel, that is, ensure the precise control of the air temperature by the low-temperature and humidity control section, avoid high-temperature air from entering the air duct, causing fluctuations in the temperature field in the wind tunnel, and affecting the test results.

[0020] Preferably, a main heat exchanger temperature sensor is provided on the main heat exchanger.

[0021] The beneficial effects of this solution are as follows: the main heat exchanger temperature sensor monitors the temperature of the main heat exchanger surface. According to the temperature monitored by the main heat exchanger temperature sensor, the opening of the steam regulating valve is adjusted in advance to limit the amount of steam entering. As the amount of steam decreases, the humidity of the air in the air duct also decreases accordingly, so that the dew point of the air in the air duct is always higher than the monitoring value of the main heat exchanger temperature sensor, avoiding ice blockage of the main heat exchanger in a low-temperature and humidity-controlled environment.

[0022] Preferably, a main heat exchanger differential pressure sensor is also provided on the main heat exchanger.

[0023] The beneficial effect of this solution is that the main heat exchanger differential pressure sensor can provide a prompt when the main heat exchanger is blocked by ice, thereby further ensuring the safety of automobile environmental wind tunnel testing in a low-temperature and humidity-controlled environment.

[0024] Preferably, a large flow section is also included, and the large flow section and the small flow section are connected in parallel with the dehumidification section and the low-temperature humidity control section.

[0025] The beneficial effect of this solution is that the large flow section improves the diversity of simulation scenarios of automobile environmental wind tunnel tests.

[0026] Preferably, two outlet valves are provided on the large flow section, and an antifreeze drying air duct is connected between the dehumidification section and the two outlet valves.

[0027] The beneficial effects of this solution are as follows: when the large flow section stops working, the first outlet valve and the second outlet valve are closed at the same time, and the antifreeze drying air duct stop valve is opened, so that a small amount of dry fresh air in the dehumidification section that has been dehumidified and heated by the rotary dehumidifier is introduced between the first outlet valve and the second outlet valve, so that the first outlet valve and the second outlet valve are always in a dry state, thereby avoiding the situation where the second outlet valve is frozen; in addition, the use of the first outlet valve can also prevent the fresh air in the antifreeze drying air duct from entering the large flow section, resulting in waste of dry fresh air. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic structural diagram of Example 1 of the present invention;

[0029] Figure 2 This is a schematic structural diagram of the low-temperature humidity control section in Example 1 of the present invention;

[0030] Figure 3 This is a structural diagram of Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The following is further described in detail through specific implementation methods:

[0032] The reference numerals in the drawings of the specification include: air duct 1, dehumidification section 2, small flow section 3, low temperature humidity control section 4, large flow section 5, first corner 101, second corner 102, third corner 103, fourth corner 104, nozzle 105, stationary chamber 106, insulation compartment plate 107, collection port 108, crawler drum pit cover 109, drum 110, drum pit 111, main fan 112, main heat exchanger 113, sunlight simulation system 114, main heat exchanger temperature sensor 115, air duct humidity sensor 116, first outlet valve 117, second outlet Valve 118, third outlet valve 119, antifreeze drying air duct stop valve 120, main heat exchanger differential pressure sensor 121, inlet air temperature sensor 401, inlet air volume sensor 402, hydrophobic antifreeze mechanism 403, steam nozzle 404, compensating fan 405, electric heating device 406, cryogenic coil differential pressure sensor 407, outlet air temperature sensor 408, outlet air humidity sensor 409, cryogenic coil 410, cryogenic coil temperature sensor 411, hydrophobic pipe 412, steam regulating valve 413, inlet air pressure sensor 414, inlet air humidity sensor 415.

[0033] Example 1

[0034] Example 1 is basically as shown in the attached Figure 1-2 As shown, Figure 1The shown automobile environmental wind tunnel low-temperature humidity control system includes an air duct 1, a dehumidification section 2, a small flow section 3 and a low-temperature humidity control section 4. The air duct 1 is provided with a first corner 101, a second corner 102, a third corner 103 and a fourth corner 104. A main fan 112 is installed between the second corner 102 and the third corner 103. The main fan 112 provides power for the automobile environmental wind tunnel test to accelerate the air in the air duct 1 to the wind speed required for the test. In this embodiment, after the main fan 112 is started, the air circulates counterclockwise along the air duct 1; a stationary chamber 106 is provided between the first corner 101 and the fourth corner 104. The stationary chamber 106 is the test section of the automobile environmental wind tunnel. The stationary chamber 106 is provided with an insulation compartment plate 107, a crawler drum pit cover plate 109, a drum 110 and a drum pit 111. The insulation compartment plate 107 ensures that the test temperature can be controlled within the set temperature. The drum 110 is set at a constant temperature to enable the vehicle to conduct a road dynamic simulation test. A sunlight simulation system 114 is arranged directly above the drum 110 to improve the diversity of the test simulation environment; the air duct 1 at the fourth corner 104 extends to one end of the stationary chamber 106 and is provided with a nozzle 105, the air duct 1 at the first corner 101 extends to one end of the stationary chamber 106 and is provided with a collecting port 108, and a main heat exchanger 113 is provided at the third corner 103. When the main fan 112 is working, the air continuously flows through the main heat exchanger 113 for heat exchange and cooling to reach the set temperature required for the test, and then is guided through the third corner 103 and the fourth corner 104 to be ejected from the nozzle 105 into the stationary chamber 106 and blow air to the test car in the stationary chamber 106, and then is guided through the collecting port 108, the first corner 101 and the second corner 102 to the rear end of the main fan 112, thereby completing a cycle.

[0035] Dehumidification section 2, low-flow section 3, and low-temperature humidity control section 4 are connected in series. Low-temperature humidity control section 4 is connected to second corner 102 via a pipe equipped with a third outlet valve 119. During low-temperature humidity control, outside air first enters dehumidification section 2 for dehumidification and drying. Dehumidification section 2 includes a filter and a rotary dehumidifier. Dehumidification section 2 operates as follows: Outside air enters the air duct of dehumidification section 2, first passes through the filter, and after impurities are removed from the air, enters the rotary dehumidifier for dehumidification, completing the dehumidification and drying process. The dehumidified dry air enters the small flow section 3 from the dehumidification section 2. The small flow section 3 includes a cooling coil and an air volume regulating valve. Since the rotary dehumidifier in the dehumidification section 2 will cause the air temperature to rise to 45℃~60℃ after dehumidification, a cooling coil is set in the small flow section 3. Cooling water of 2℃-3℃ is passed through the cooling coil to first reduce the temperature of the dry air to 10℃. The cooled air is then reduced in flow by the air volume regulating valve and then enters the low-temperature humidity control section 4. Using the cooling coil to preliminarily cool the air in the small flow section 3 can reduce the cooling load in the low-temperature humidity control section 4, and avoid the low-temperature humidity control section 4 being loaded for cooling due to excessive air temperature, and failing to reduce the air temperature to the same as the test set temperature in the wind tunnel, that is, ensuring the precise control of the air temperature by the low-temperature humidity control section 4, and avoiding high-temperature air entering the air duct 1, causing fluctuations in the temperature field in the wind tunnel, and affecting the test results.

[0036] Low temperature and humidity control section 4 is the most important technical means for this solution to achieve low temperature and precise humidity control. Figure 2 As shown, the low-temperature humidity control section 4 is provided with an inlet air temperature sensor 401, an inlet air volume sensor 402, an inlet air pressure sensor 414, an inlet air humidity sensor 415, several steam nozzles 404, a steam regulating valve 413, a cryogenic coil 410, an outlet air temperature sensor 408, an outlet air humidity sensor 409 and a cryogenic coil temperature sensor 411 in sequence. With the air inlet end as the front end and the air outlet end as the rear end, the steam nozzles 404 are all arranged at the front end of the cryogenic coil 410, and the spray direction of the steam nozzles 404 is all toward the direction of the air flow, so that the steam can be fully and evenly mixed with the air flowing into the air duct after being ejected from the steam nozzles 404. The spray angle of each steam nozzle 404 is V-shaped to ensure that the steam ejected by the steam nozzle 404 can occupy the cross-section of the entire low-temperature humidity control section 4 air duct to achieve uniform spraying, thereby further ensuring that the steam and air are mixed evenly, avoiding the occurrence of excessive local humidity in the air, affecting the precise control of humidity. In addition, the steam nozzle 404 is set at the front end of the cryogenic coil 410, so that the air is humidified first and then cooled. This can avoid the cooled air from coming into contact with the high-temperature steam again, which will lead to the problem of poor control of the temperature of the fresh air. Figure 2The lower portion is a left side view of the steam nozzles 404. In this embodiment, the steam nozzles 404 are arranged in three rows, with five nozzles in each row, and all the steam nozzles 404 are evenly distributed. The steam regulating valve 413 is connected to a steam generating device (not shown in the figure), that is, one steam regulating valve 413 controls all the steam nozzles 404. In addition, the steam regulating valve 413 is a low-flow steam regulating valve 413 because, in a low-temperature humidity-controlled environment, the amount of steam required to increase the humidity of the dried air by injecting steam is relatively small. When a low-flow steam regulating valve 413 is used to adjust the valve opening, more precise control of the amount of steam added can be achieved. Precise control of the amount of steam added can further ensure precise control of the air humidity in the low-temperature environment.

[0037] like Figure 2 As shown, the dehumidification section 2 also includes a hydrophobic antifreeze mechanism 403, a compensating fan 405, an electric heating device 406 and a cryogenic coil differential pressure sensor 407. The hydrophobic antifreeze mechanism 403 includes a drain pipe 412 and an annular water collecting pipe welded on the inner wall of the air duct of the low-temperature humidity control section 4. The annular water collecting pipe is located at the front and rear ends of the steam nozzle 404, and the annular water collecting pipe is connected to the drain pipe 412. In the process of humidifying the dry fresh air, a small amount of steam ejected from the steam nozzle 404 will reach the inner wall surface of the air duct, and some steam will condense and adhere. The additional annular water collecting pipe can collect the condensed water and discharge it through the drain pipe 412, thereby preventing the condensed water from adhering to the inner surface of the air duct and being blown to the surface of the cryogenic coil 410 along the air duct under the action of air flow, causing the surface of the cooling coil to freeze, affecting the cooling effect of the cryogenic coil 410, and avoiding interruption of the automobile environmental wind tunnel test. The compensating fan 405 is arranged at the rear end of the hydrophobic antifreeze mechanism 403. Since the use of the steam nozzle 404 and the hydrophobic antifreeze mechanism 403 will increase the wind resistance in the air duct, the added compensating fan 405 can just compensate for this part of the pressure drop, thereby achieving the purpose of accurately controlling the wind pressure in the low-temperature and humidity control section 4; and, during the rotation process, the compensating fan 405 can fully stir and mix the steam and air, thereby further improving the uniformity of the air humidity and preventing the surface of the cooling coil from being frozen due to excessive humidity in some areas. The cryogenic coil differential pressure sensor 407 is connected to both ends of the cryogenic coil 410 to monitor the differential pressure before and after the cryogenic coil 410; the electric heating device 406 is arranged on the front side of the cryogenic coil 410. When the cryogenic coil differential pressure sensor 407 detects that the differential pressure before and after the cryogenic coil 410 reaches a certain value, it indicates that the cryogenic coil 410 is blocked by ice. At this time, the steam regulating valve 413 must be closed immediately, humidification must be stopped, and the electric heating device 406 must be turned on at the same time to heat and de-ice. Dry air is continuously blown in from the small flow section 3 to accelerate the heat generated by the electric heating device 406 to blow to the cryogenic coil 410, thereby quickly removing the ice on the cooling coil to avoid damage to the device and ensure the safety of the operation of the low-temperature humidity control section 4.

[0038] The inlet air temperature sensor 401 monitors the inlet air temperature of the low temperature and humidity control section 4. The inlet air temperature is controlled by the cooling coil in the small flow section 3. In this embodiment, the inlet air temperature is controlled at 10°C. The inlet air volume sensor 402 monitors the inlet air volume in m 3 / h, the air volume is controlled by the air volume regulating valve in the small flow section 3, and the air volume is controlled at 1000~5000m 3 / h; the inlet air pressure sensor 414 monitors the pressure of the inlet air, the unit is Pa; the inlet air humidity sensor 415 monitors the humidity of the inlet air, and the monitored humidity is the relative humidity. In order to achieve precise control of the humidity inside the wind tunnel at low temperatures, it is necessary to calculate the mass flow rate of the inlet air and the absolute humidity content of the inlet air. The mass flow rate of the inlet air is obtained by multiplying the volume flow rate by the air density. The volume flow rate is collected by the inlet air volume sensor 402, and the air density is calculated from the wind pressure collected by the inlet air pressure sensor 414, the wind temperature collected by the inlet air temperature sensor 401, and the relative humidity collected by the inlet air humidity sensor 415. The absolute humidity content of the inlet air also has a functional relationship with the wind pressure, wind temperature and relative humidity. Therefore, the humidity of the air can be pre-controlled at the inlet end of the low-temperature humidity control section 4, preparing for the next step of precise control of the air humidity at the outlet end of the low-temperature humidity control section 4.

[0039] At the same time, if Figure 1As shown, the third corner 103 is also provided with an air duct humidity sensor 116, and the main heat exchanger 113 is connected to the main heat exchanger temperature sensor 115 and the main heat exchanger differential pressure sensor 121. The air duct humidity sensor 116 monitors the air humidity in the air duct 1, and this humidity is relative humidity. The main heat exchanger temperature sensor 115 monitors the temperature of the surface of the main heat exchanger 113, and the main heat exchanger differential pressure sensor 121 monitors the differential pressure value before and after the main heat exchanger 113. In addition, the temperature in the air duct 1 is monitored by the air duct 1 temperature sensor (the air duct temperature sensor is not shown in the figure); the temperature of the air in the air duct 1 and the relative humidity in the air duct 1 can calculate the dew point temperature of the air in the air duct 1 in this state. The temperature value monitored by the main heat exchanger temperature sensor 115 cannot be lower than the dew point temperature, otherwise, in the deep cold and low temperature experimental environment, the main heat exchanger The heat exchanger 113 may be blocked by ice, and after ice formation, the main heat exchanger differential pressure sensor 121 will prompt that the differential pressure is too high and the main heat exchanger 113 is in a blocked state; based on this, in order to avoid the main heat exchanger 113 from being frozen, the opening of the steam regulating valve 413 is adjusted in advance according to the temperature monitored by the main heat exchanger temperature sensor 115, and the amount of steam entering is limited. As the amount of steam decreases, the humidity of the air in the air duct 1 also decreases accordingly, so that the air dew point in the air duct 1 is always higher than the monitoring value of the main heat exchanger temperature sensor 115, avoiding the main heat exchanger 113 from being blocked by ice in a low-temperature and humidity-controlled environment; the main heat exchanger differential pressure sensor 121 can give a prompt when the main heat exchanger 113 is blocked by ice, so as to further ensure the safety of the automobile environmental wind tunnel test in a low-temperature and humidity-controlled environment.

[0040] There is a transfer function relationship between the opening of the steam control valve 413 and the humidity value inside the air duct 1. This transfer function can be obtained by performing a step response test during commissioning. The limit value of the humidity setting in the air duct 1 can be obtained by reversely calculating the dew point temperature formula, specifically:

[0041]

[0042] φ set (limit) is the air duct humidity limit value, t HXC is the surface temperature of the main heat exchanger 113, in °C; t main is the wind tunnel temperature, which is monitored by the wind tunnel temperature sensor 116, in °C; in the formula (t HXC -1) is to make φ set (limit) humidity and t main The dew point temperature calculated by temperature is t HXC 1°C lower, thereby further avoiding ice blockage of the main heat exchanger 113.

[0043] When pre-controlling the humidity of the air flowing out of the low-temperature humidity control section 4, it is necessary to set a preset opening value for the steam control valve 413. Specifically, the steam control valve 413 is first opened at the preset opening value to humidify the air before fine-tuning. Since the air duct of the entire low-temperature humidity control section 4 is relatively long, and the distance from the air inlet to the installation location of the air duct humidity sensor 116 is also relatively long, there is a significant delay and inertia when correcting the opening of the steam control valve 413. This results in a long time from the action of the steam control valve 413 to the wind tunnel humidity response. This means that controlling the relationship between the steam control valve 413 and the wind tunnel humidity is extremely difficult. Therefore, a preset opening value for the steam control valve 413 is obtained through theoretical calculation. Finally, by compensating for interference during the humidity control process, the controlled variable is stabilized, errors are eliminated, and precise control of the wind tunnel humidity in the automotive environment is achieved.

[0044] The calculation process of the preset value of the steam control valve opening is as follows:

[0045] T1=t1+273

[0046] p sac,1 =exp(-6094.4642×T1 -1 +21.1249952-2.724552×10 -2 ×T1+1.6853396×10 -5 ×T1 2 +2.4575506×ln(T1))

[0047]

[0048]

[0049] m1=ρ1×V1

[0050]

[0051] Where: t1 is the temperature value monitored by the inlet air temperature sensor 401, unit: °C; T1 is the absolute temperature of the inlet air, unit: K; p sac,1 is the inlet air saturated steam pressure, in Pa; p1 is the pressure value monitored by the inlet air pressure sensor 414, in Pa; φ1 is the relative humidity monitored by the inlet air humidity sensor 415, in %; χ1 is the inlet air absolute humidity, in kg / kg; R air is the gas constant of air, which is 287.06, in J / (kg k); R V is the water vapor gas constant, which is 461.04, in J / (kg k); ρ1 is the inlet air density, in kg / m 3 ; V1 is the air volume flow rate, which is monitored by the air volume sensor 402, in m3 / h; m1 is the air inlet mass flow rate, unit is kg / h; m max is the steam mass flow rate at the maximum opening of the steam regulating valve 413, in kg / h; u feedford (s) is the steam control valve opening feedforward value, 0≤u feedford (s)≤100.

[0052] The temperature monitored by the cryogenic coil temperature sensor 411 is the surface temperature of the cryogenic coil 410, the temperature monitored by the outlet air temperature sensor 408 is the outlet air temperature of the low-temperature humidity control section 4, and the humidity monitored by the outlet air humidity sensor 409 is the outlet air relative humidity of the low-temperature humidity control section 4. The dew point temperature of the air in the low-temperature humidity control section 4 can be calculated based on the outlet air temperature and the outlet air relative humidity. The reason for obtaining the dew point temperature at the outlet end of the low-temperature humidity control section 4 is also because the temperature value monitored by the cryogenic coil temperature sensor 411 cannot be lower than the dew point temperature, otherwise the cryogenic coil 410 will freeze. Therefore, in order to further avoid freezing on the surface of the cryogenic coil 410, the temperature monitored by the cryogenic coil temperature sensor 411 is compared with the duct humidity limit value φ in the duct 1. set By coordinating the steam control valve 413 opening and limiting steam entry, the low-temperature humidity control section 4's dew point temperature is consistently above the value monitored by the cryogenic coil temperature sensor 411, thereby preventing icing on the cryogenic coil 410. A transfer function exists between the steam control valve 413 opening and the humidity setpoint within the low-temperature humidity control section 4. This transfer function can also be determined through a step response test during commissioning. The formula for calculating the humidity setpoint limit for the low-temperature humidity control section is still derived by inversely deducing the dew point temperature formula:

[0053]

[0054] φ 2set (limit) is the humidity limit value of the low temperature humidity control section, t deep cooling is the surface temperature of the cryogenic coil, unit is ℃; t exit is the outlet air temperature of the low temperature and humidity control section, unit is ℃; in the formula (t deep cooling -1) is to make φ 2set (limit) humidity and t exit The dew point temperature calculated by temperature is t deep cooling 1°C lower to further ensure that the cryogenic coil does not freeze.

[0055] At the same time, the system also includes a controller. The main heat exchanger temperature sensor 115, the air duct humidity sensor 116 and other sensors transmit the collected data to the controller. After analysis and judgment, the controller controls the steam regulating valve 413, the electric heating device 406 and the like to take action to realize automatic control of the system humidity.

[0056] In addition, during the low temperature humidity control process, a humidity setting value in the air duct will be determined first according to the specific requirements of the automobile environmental wind tunnel test. This setting value cannot be higher than the air duct humidity limit value φ set Therefore, when using the low-temperature humidity control section to humidify the dry fresh air, it is necessary to first determine the final value of the duct humidity. The final value is obtained by taking the smaller value of the humidity set value and the humidity limit value. According to the final value of the duct humidity, the humidity set value of the low-temperature humidity control section is determined by PID calculation. The humidity set value of the low-temperature humidity control section cannot be higher than the humidity limit value φ of the low-temperature humidity control section. 2set (limit), that is, the final humidity value of the low-temperature humidity control section still needs to be obtained by taking the smaller value between the humidity set value and the humidity limit value. Finally, the correction value of the steam control valve opening is obtained through PID calculation. The correction value corrects the preset value of the steam control valve to determine the final value of the steam control valve opening. The humidity in the air duct that is originally relatively far away from the steam control valve is promptly fed back to the control of the steam control valve opening through various sensors in the system, thereby realizing precise control of the humidity in the automotive environmental wind tunnel.

[0057] The specific implementation process is as follows: first, the main heat exchanger 113 is used to reduce the temperature inside the wind tunnel to the set temperature required for the test; then the dehumidification section 2, the small flow section 3, the low-temperature humidity control section 4 and the third outlet valve 119 are opened in sequence, and the outside air is first filtered and dried through the dehumidification section 2, and then enters the small flow section 3 for pre-cooling and air volume reduction. The small flow of dry air enters the low-temperature humidity control section 4, and the low-temperature humidity control section 4 cools and humidifies the air about to enter the wind tunnel, and the air temperature is reduced to the same as the set temperature required for the wind tunnel test, thereby avoiding the fluctuation of the temperature field inside the wind tunnel caused by the addition of air in the deep cold and low temperature wind tunnel environment, affecting the accuracy of the test.

[0058] At the same time, the steam nozzle 404 is positioned in the low-temperature humidity control section 4, which changes the prior art arrangement of directly injecting steam into the wind tunnel when controlling the humidity of the wind tunnel. This solves the problem of directly injecting high-temperature steam into a deep, low-temperature automotive environmental wind tunnel. This not only causes the problem of excessive wind speed inside the automotive environmental wind tunnel causing stratification of the added steam, making it difficult for the steam to mix evenly with the air, but also solves the problem of the steam nozzle increasing the wind resistance inside the wind tunnel, requiring the main fan 112 power to be increased to ensure the test wind speed, which could lead to safety hazards in the wind tunnel test. Since the steam control valve 413 is positioned in the low-temperature humidity control section 4, in order to ensure a timely response between the humidity inside the wind tunnel and the opening of the steam control valve 413, the humidity sensors and temperature sensors in the wind tunnel and the low-temperature humidity control section 4 are used to determine the preset opening value and the correction value, and the opening of the steam control valve 413 is dynamically adjusted in real time, thereby achieving precise control of the humidity inside the wind tunnel. A main heat exchanger differential pressure sensor 121 is provided on the main heat exchanger 113, and a cryogenic coil differential pressure sensor 407 is provided on the cryogenic coil 410 to monitor the differential pressure between the main heat exchanger 113 and the cryogenic coil 410. If ice blockage is detected in the main heat exchanger 113 or the cryogenic coil 410, a timely response can be made to close the steam regulating valve 413 and start the electric heating device 406 to perform heating and de-icing operations, thereby ensuring the safety of the automobile environmental wind tunnel test.

[0059] Example 2

[0060] like Figure 3 The illustrated low-temperature humidity control system for an automotive environmental wind tunnel differs from Example 1 in that it also includes a high-flow section 5, which is connected in parallel with the low-flow section 3 and the low-temperature humidity control section 4. These sections are then connected in series with the dehumidification section 2 and the air duct 1, respectively. The high-flow section 5 includes a variable-frequency fan, an aftercooling coil, a steam coil, a humidifier, and an antifreeze-drying duct, enabling it to perform both heating and heating-humidification mode simulations. The outlet of the high-flow section 5 is equipped with a first outlet valve 117 and a second outlet valve 118. In this embodiment, an antifreeze-drying duct is connected to the dehumidification section 2. The other end of the antifreeze-drying duct is connected between the first outlet valve 117 and the second outlet valve 118. The antifreeze-drying duct is also equipped with an antifreeze-drying duct shutoff valve 120.

[0061] During long periods of low-temperature and humidity control, to reduce the complexity of the system structure, the air ducts of the large flow section 5 and the small flow section 3 are connected in parallel. Therefore, when performing low-temperature and humidity control on the wind tunnel, it is necessary to close the large flow section 5, simultaneously closing the first outlet valve 117 and the second outlet valve 118. Then, open the third outlet valve 119 to connect the low-temperature and humidity control section 4 with the wind tunnel. As a result, the low-temperature, high-humidity air in the low-temperature and humidity control section 4 will flow back to the second outlet valve 118 of the large flow section 5, causing the temperature of the second outlet valve 118 to drop. At the same time, since some condensed water will remain in the large flow section 5 during use, if only one second outlet valve 118 is installed, condensed water will also be present around the second outlet valve 118. Under the influence of the low-temperature air returning from the low-temperature and humidity control section 4, the temperature of the second outlet valve will drop below 0°C, and ice will freeze, resulting in the valve of the large flow section 5 being unable to open the next time it is used. Therefore, a first outlet valve 117 is added. When the high-flow section 5 stops working, the first outlet valve 117 and the second outlet valve 118 are closed simultaneously, and the antifreeze drying air duct stop valve 120 is opened. A small amount of dry fresh air in the dehumidification section 2, which has been dehumidified and heated by the rotary dehumidifier, is introduced between the first outlet valve 117 and the second outlet valve 118. This keeps the first outlet valve 117 and the second outlet valve 118 in a dry state at all times, thus preventing the second outlet valve 118 from freezing. Furthermore, the use of the first outlet valve 117 can prevent the fresh air in the antifreeze drying air duct from entering the high-flow section 5, resulting in waste of dry fresh air. At the same time, a tail exhaust pipe is also provided in the station chamber 106, which exhausts a portion of the air in the station chamber 106, thereby further ensuring the test environment in the automotive environmental wind tunnel.

[0062] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A low-temperature humidity control system for an automotive environmental wind tunnel, characterized by: It includes an air duct, a dehumidification section and a low-temperature humidity control section, the dehumidification section is connected to the low-temperature humidity control section, and the low-temperature humidity control section is connected to the air duct; the low-temperature humidity control section includes a cryogenic coil, a plurality of steam nozzles, a steam regulating valve, an inlet air temperature sensor, an inlet air humidity sensor, an inlet air volume sensor, an inlet air pressure sensor, an outlet air temperature sensor and an outlet air humidity sensor, and the steam nozzles are all connected to the steam regulating valve; a main heat exchanger and an air duct humidity sensor are provided in the air duct; it also includes a controller, and the inlet air temperature sensor, inlet air humidity sensor, inlet air volume sensor, inlet air pressure sensor, outlet air temperature sensor and outlet air humidity sensor transmit the collected data to the controller, and the controller controls the valve opening of the steam regulating valve; The steam nozzles are all set on the side of the cryogenic coil close to the dehumidification section, and the steam nozzles are all facing the direction of air inlet; The dehumidification section also includes a hydrophobic antifreeze mechanism and a compensating fan. The hydrophobic antifreeze mechanism is arranged on both sides of the steam nozzle, and the compensating fan is arranged between the hydrophobic antifreeze mechanism and the cryogenic coil. It also includes a small flow section, which includes a cooling coil and an air volume regulating valve; the dehumidification section, the small flow section and the low-temperature humidity control section are connected in series.

2. The low-temperature humidity control system for an automotive environmental wind tunnel according to claim 1, characterized in that: The dehumidification section also includes an electric heating device, a cryogenic coil temperature sensor and a cryogenic coil differential pressure sensor. The electric heating device is arranged on one side of the cryogenic coil, and the cryogenic coil temperature sensor and the cryogenic coil differential pressure sensor are both connected to the cryogenic coil.

3. The low-temperature humidity control system for an automotive environmental wind tunnel according to claim 1, characterized in that: A main heat exchanger temperature sensor is provided on the main heat exchanger.

4. The low-temperature humidity control system for an automotive environmental wind tunnel according to claim 3, characterized in that: A main heat exchanger differential pressure sensor is also provided on the main heat exchanger.

5. The low-temperature humidity control system for an automotive environmental wind tunnel according to any one of claims 1 to 4, characterized in that: It also includes a large flow section, which is connected in parallel with the small flow section and the low-temperature humidity control section.

6. The low-temperature humidity control system for an automotive environmental wind tunnel according to claim 5, characterized in that: Two outlet valves are provided on the large flow section, and an antifreeze drying air duct is connected between the dehumidification section and the two outlet valves.

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