An air intake pressure regulating system and pressure regulating method for a low-density wind tunnel

Abstract

The present invention provides an air inlet pressure regulation system and pressure regulation method for a low-density wind tunnel. The system includes an air source module, a pressure regulation module, a heater, and a nozzle, which are connected in sequence. The air source module includes a nitrogen preparation station, a dynamic air storage tank, and an energy storage air storage tank. The dynamic air storage tank and the energy storage air storage tank are connected in parallel via a pipeline, and valves are provided at the inlet and outlet ends of the dynamic air storage tank and the energy storage tank. The pressure regulation module includes multiple parallel pressure regulation pipelines, and pressure regulating valves for different volume flow rates are respectively provided on different pressure regulation pipelines. The pressure regulation method adopts the method of controlling the pressure drop of the air storage tank, controlling the initial pressure of the air storage tank, and controlling multiple types of pressure regulating valves, replacing the conventional wind tunnel's pressure-graded air storage tank + single-stage or multi-stage PID control pressure regulating valve solution. This method overcomes the inherent characteristics of small-diameter pressure regulating valves, such as poor continuity of high-precision valve position control, narrow linear adjustment range, and low pressure regulation accuracy, and meets the high-precision pressure regulation requirements of low-density wind tunnel experiments with small volume flow rates and a wide volume flow rate range.

Description

Technical Field

[0001] The present invention relates to the technical field of wind tunnel testing, and in particular to an air intake pressure regulating system and a pressure regulating method for a low-density wind tunnel. Background Art

[0002] Low-density wind tunnel inlet pressure regulating systems exhibit operational characteristics such as low volumetric flow rates and a wide volumetric flow rate range, which are key issues to address when designing low-density wind tunnel inlet pressure regulating systems. Typical low-density wind tunnels have a Mach number range of 10 to 25, a regulated total pressure range of 0.05 MPa to 1.5 MPa (a 30-fold pressure span), an regulated mass flow rate range of 1 g / s to 500 g / s (a 500-fold flow span), and an regulated volumetric flow rate range of 0.4 to 120 L / s (a 300-fold volumetric flow rate span). The air source is a 2 MPa medium-pressure air source with a volumetric flow rate of 0.04 to 40 L / s (a 1000-fold volumetric flow rate span). These systems exhibit typical operational characteristics such as low volumetric flow rates and a wide volumetric flow rate range.

[0003] Existing conventional wind tunnel inlet pressure regulation systems generally use medium-pressure or high-pressure air sources, or both, in conjunction with single-stage or two-stage pressure regulating valve systems to meet the wide pressure regulation requirements of conventional wind tunnels. Typical meter-scale conventional wind tunnels operate at Mach numbers of 5 to 10, with a total pressure range of 0.01 MPa to 6 MPa (a 600-fold pressure span), a mass flow rate range of 1 kg / s to 200 kg / s (a 200-fold flow span), and a volume flow rate of 800 to 8000 L / s (a 10-fold volume flow rate span). These air sources include a 20 MPa high-pressure source and a 2 MPa medium-pressure source, with a volume flow rate of 30 to 900 L / s (a 30-fold volume flow rate span). These systems exhibit typical operating characteristics, including a wide operating pressure range and a moderate volume flow rate. Conventional wind tunnel air inlet pressure regulating systems use air source systems with different pressure levels, combined with single-stage or multi-stage pressure regulating valves, and employ two-stage or single-stage pressure reducing methods to meet different operating pressure tests, thereby meeting the wide operating pressure range pressure regulation requirements of conventional wind tunnels. Conventional wind tunnel air inlet pressure regulating systems are only suitable for conventional wind tunnel pressure regulation needs with medium volume flow rates. The pressure regulation accuracy of small-diameter pressure regulating valves below DN10 can only reach the order of 5%, the high-precision valve position control of small-diameter pressure regulating valves of DN25 is discontinuous, and the linear adjustment range of small-diameter pressure regulating valves of DN40 is narrow. Due to the lack of suitable small-diameter high-precision pressure regulating valves, the existing small-diameter pressure regulating valve + conventional wind tunnel air inlet pressure regulating system solution cannot meet the high-precision pressure regulation requirements of low-density wind tunnels.

[0004] The typical conventional wind tunnel inlet pressure regulating system scheme is as follows:

[0005] [1] Patent CN201911204272.2 “A wide range intake pressure regulating system for hypersonic wind tunnels” discloses an intake pressure regulating system for conventional wind tunnels. It uses a high-pressure gas source and a medium-pressure gas source in combination with a single-stage or two-stage pressure regulating valve. The first-stage pressure regulating valve is a bypass butterfly valve or a front-stage high-pressure pressure reducing valve, and the second-stage is a medium-pressure pressure regulating valve or a rear-stage high-pressure pressure regulating valve. These valves respectively realize high-precision intake pressure regulating functions over a wide range of vacuum, medium-pressure, and high-pressure inlet pressures. The first-stage pressure regulating valve used in this intake pressure regulating system is a bypass butterfly valve or a hydraulic pressure reducing valve, and the second-stage pressure regulating valve is a hydraulic plunger pressure regulating valve. Combined with the general PID pressure regulating method, this system meets the high-precision intake pressure regulating requirements over a wide range of vacuum, medium-pressure, and high-pressure inlet pressures for conventional hypersonic wind tunnels. Due to the lack of high-precision small-diameter pressure regulating valves, it cannot meet the intake pressure regulating requirements of low-density wind tunnels with small volume flow rates and a wide volume flow rate range.

[0006] [2] Patent CN201911204248.9, “A method for regulating vacuum pressure inlet pressure in a hypersonic wind tunnel”, discloses a method for regulating vacuum inlet pressure in conventional wind tunnels. The method utilizes a medium-pressure gas source, a two-stage pressure regulating system with a bypass valve and a single-stage medium-pressure regulating valve. The first-stage bypass valve is a bypass butterfly valve, and the second-stage pressure regulating valve is a hydraulic plunger pressure regulating valve. Combined with the general PID pressure regulation method, the method can achieve precise control of the vacuum inlet pressure. Due to the lack of high-precision small-diameter pressure regulating valves, it is impossible to meet the intake pressure regulation requirements of low-density wind tunnels with small volume flow rates and a wide volume flow rate range. Summary of the Invention

[0007] The object of the present invention is to provide an air intake pressure regulating system and pressure regulating method for a low-density wind tunnel, which is used to solve the problem of high-precision pressure regulation in a low-density wind tunnel with a small volume flow rate and a wide volume flow rate range.

[0008] The present invention provides an air intake pressure regulating system for a low-density wind tunnel, comprising an air source module, a pressure regulating module, a heater and a nozzle connected in sequence. The air source module comprises a nitrogen preparation station, a dynamic air storage tank and an energy storage air storage tank. The dynamic air storage tank and the energy storage air storage tank are connected in parallel via pipelines, and valves are provided at the inlet and outlet ends of the dynamic air storage tank and the energy storage tank. The pressure regulating module comprises a plurality of pressure regulating pipelines connected in parallel, and pressure regulating valves for different volume flow rates are respectively provided on different pressure regulating pipelines.

[0009] Furthermore, the dynamic gas storage tank and the energy storage tank are both medium-pressure gas storage tanks with a maximum operating pressure of 2 MPa.

[0010] Furthermore, both the dynamic gas storage tank and the energy storage tank are provided with a deflation pipeline, and the deflation pipeline is provided with a deflation valve.

[0011] Furthermore, the pressure regulating module includes a first pressure regulating pipeline, a second pressure regulating pipeline, a third pressure regulating pipeline and a fourth pressure regulating pipeline connected in parallel. The first pressure regulating pipeline is provided with a positioning pressure reducing valve a and a solenoid valve a, the second pressure regulating pipeline is provided with a positioning pressure reducing valve b and a solenoid valve b, the third pressure regulating pipeline is provided with an electric pressure regulating valve, and the fourth pressure regulating pipeline is provided with a hydraulic pressure regulating valve.

[0012] Furthermore, the inlet end of the dynamic gas storage tank is provided with a gas source preparation valve a, and the outlet end is provided with a gas source management valve a; the inlet end of the energy storage gas storage tank is provided with a gas source preparation valve b, and the outlet end is provided with a gas source management valve b.

[0013] A pressure regulation method for an air inlet pressure regulating system for a low-density wind tunnel utilizes different combinations of medium-pressure gas storage tanks based on different volume flow rate test requirements. The pressure drop ratio of the medium-pressure gas storage tanks is controlled during effective testing, reducing the design difficulty of the pressure regulating valve in the downstream pressure regulating module and meeting the high-precision pressure regulation requirements of low-volume flow rate tests. The pressure regulation method is divided into three operating conditions: extremely low, moderate, and high, depending on the outlet volume flow rate of the pressure regulating module.

[0014] In the test of the outlet volume flow rate range of the pressure regulating module under extremely small working conditions, the pressure regulation method is as follows:

[0015] a1: Select a dynamic gas storage tank to supply gas for the test within the minimum test volume flow range;

[0016] a2: Release air by opening the bleed valve a to reduce the initial pressure of the dynamic gas storage tank, or increase the initial pressure of the dynamic gas storage tank by opening the gas source management valve a and gas source management valve b to charge the dynamic gas storage tank from the accumulator gas tank. Accurately control the initial pressure of the dynamic gas storage tank required by the test state, and control the initial pressure accuracy within 1%;

[0017] a3: Open the gas source management valve a;

[0018] a4: According to the test state requirements, open the solenoid valve a and / or the solenoid valve b, use the positioning pressure reducing valve a and / or the positioning pressure reducing valve b to reduce the pressure. After the decompressed air flow is heated by the heater, a test air flow medium with stable total pressure and total temperature is formed at the nozzle inlet. The pressure regulation control accuracy is within 1.5%;

[0019] In the moderate operating conditions test of the outlet volume flow rate range of the pressure regulating module, the pressure regulation method is as follows:

[0020] b1: Select a dynamic gas storage tank to supply gas for the test within a moderate test volume flow range;

[0021] b2: Release the air by opening the air release valve a to reduce the initial pressure of the dynamic air storage tank, or increase the initial pressure of the dynamic air storage tank by opening the air source management valve a and the air source management valve b to charge the dynamic air storage tank from the energy storage tank. Accurately control the initial pressure of the dynamic air storage tank required by the test state, so that the initial pressure accuracy is controlled within 1%;

[0022] b3: Open the gas source management valve a;

[0023] b4: According to the test state requirements, open the electric pressure regulating valve to a certain opening and maintain it. After the decompressed air flow is heated by the heater, a test air flow medium with stable total pressure and total temperature is formed at the nozzle inlet. The pressure regulation control accuracy is within 2%;

[0024] In the test of the outlet volume flow rate range of the pressure regulating module under larger working conditions, the pressure regulation method is as follows:

[0025] c1: Select dynamic gas storage tanks and energy storage tanks to supply gas for the test with a larger test volume flow range;

[0026] c2: According to the test requirements, release air by opening the air release valve a and the air release valve b to reduce the initial pressure of the dynamic air storage tank and the accumulator air storage tank respectively; or increase the initial pressure of the dynamic air storage tank and the accumulator air storage tank by opening the nitrogen preparation station and the gas source preparation valve a and the gas source preparation valve b to inflate the tanks. Set the initial pressure of the two gas storage tanks so that the pressure regulating valve operates within its linear adjustment range;

[0027] c3: Open the gas source management valve a and gas source management valve b;

[0028] c4: The PID control strategy is used to implement feedback control of the valve position of the hydraulic pressure regulating valve. After the air flow is heated by the heater, a test air flow medium with stable total pressure and total temperature is formed at the nozzle inlet, and the pressure regulation control accuracy is within 2%.

[0029] Furthermore, during the effective test process, the pressure drop ratio control of the medium-pressure gas storage tank adopts a classification control strategy based on the gas volume flow rate at the outlet of the pressure regulating module, specifically:

[0030] Minimum working condition: When the outlet volume flow rate range of the pressure regulating module is 0L / s<G≤5L / s, a dynamic gas storage tank is used for gas supply, and the effective test duration of a single test is ≥30s. The pressure drop ratio of the medium-pressure gas storage tank during the effective test is controlled. ≤1%;

[0031] Moderate working conditions: When the outlet volume flow rate of the pressure regulating module is within the range of 5L / s<G≤20L / s, a dynamic gas storage tank is used for gas supply, and the single test duration is ≥30s. The pressure drop ratio of the medium-pressure gas storage tank during the effective test process is controlled. ≤2%;

[0032] Large working condition: When the outlet volume flow rate range of the pressure regulating module is 20L / s<G≤120L / s, the dynamic gas storage tank and the energy storage tank are used to supply gas together. The single test duration is ≥30s. The pressure drop ratio of the medium pressure gas storage tank during the effective test process is controlled. ≤8%.

[0033] Furthermore, according to the pressure regulation requirements of different pressure regulating module outlet volume flow rate range tests, pressure regulation accuracy control strategies based on different types of pressure regulating valves are adopted to meet the high-precision pressure regulation requirements of low-density wind tunnel small volume flow rate tests, as follows:

[0034] When the outlet volume flow rate of the pressure regulating module is 0.4L / s≤G≤5L / s, the pressure regulating valve adopts positioning pressure reducing valve a and positioning pressure reducing valve b, and accurately controls the initial pressure of the dynamic gas storage tank to achieve a pressure regulation accuracy within 1.5%;

[0035] When the outlet volume flow rate of the pressure regulating module is 5L / s<G≤20L / s, a DN25 electric pressure regulating valve is used to accurately control the initial pressure of the dynamic gas storage tank so that the pressure regulation accuracy is within 2%;

[0036] When the outlet volume flow rate of the pressure regulating module is 20 L / s<G≤120L / s, a DN40 hydraulic pressure regulating valve is used in conjunction with PID control technology to control the positioning accuracy of the pressure regulating valve within 0.3%, so that its pressure regulation accuracy reaches within 2%.

[0037] Furthermore: when the outlet volume flow rate range of the pressure regulating module is 0.4 L / s≤G≤5L / s, positioning pressure reducing valve a and positioning pressure reducing valve b are used as pressure regulating valves, which are fixed throat orifice plates or flow nozzles to accurately control the initial pressure of the dynamic gas storage tank, with a repeatable control accuracy within 1%, so that the pressure regulation accuracy is within 1.5%;

[0038] When the outlet volume flow rate range of the pressure regulating module is 5 L / s<G≤20L / s, the pressure regulating valve adopts a DN25 electric pressure regulating valve to accurately control the initial pressure of the dynamic gas storage tank, with a repeatable control accuracy within 1%, so that the pressure regulation accuracy can reach within 2%;

[0039] When the outlet volume flow rate range of the pressure regulating module is 20 L / s<G≤120L / s, the pressure regulating valve uses a DN40 hydraulic pressure regulating valve combined with PID control technology as the pressure regulating valve. The positioning accuracy of the pressure regulating valve is within 0.3%, so that the pressure regulation accuracy reaches within 2%.

[0040] Furthermore, in the test where the outlet volume flow rate of the pressure regulating module is in the range of 0.4 L / s≤G≤5 L / s, both the positioning pressure reducing valve a and the positioning pressure reducing valve b adopt a fixed throat orifice plate or a throttling nozzle.

[0041] The beneficial effects of the present technical solution are as follows: the present invention provides an air intake pressure regulating system for a low-density wind tunnel and a pressure regulating method for different volume flow rates after pressure regulating valves. It adopts the method of controlling the pressure drop of the air storage tank, controlling the initial pressure of the air storage tank and controlling multiple types of pressure regulating valves to replace the conventional wind tunnel's pressure grade air storage tank + single-stage or multi-stage PID control pressure regulating valve solution, overcomes the inherent characteristics of small-caliber pressure regulating valves such as poor continuity of high-precision valve position control, narrow linear adjustment range, and low pressure regulation accuracy, and meets the high-precision pressure regulation requirements of low-density wind tunnel tests with small volume flow rates and a wide volume flow rate range. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 This is a system principle diagram of the present invention.

[0044] Explanation of the accompanying symbols: 1-nitrogen preparation station; 2-gas source preparation valve a; 3-gas source preparation valve b; 4-dynamic gas storage tank; 5-energy storage tank; 6-air release valve a; 7-air release valve b; 8-gas source management valve a; 9-gas source management valve b; 10-solenoid valve a; 11-solenoid valve b; 12-positioning pressure reducing valve a; 13-positioning pressure reducing valve b; 14-electric pressure regulating valve; 15-hydraulic pressure regulating valve; 16-heater; 17-nozzle. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting the present invention.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0048] Example 1

[0049] like Figure 1 As shown, the present invention provides an air intake pressure regulation system for a low-density wind tunnel, comprising an air source module, a pressure regulation module, a heater 16 and a nozzle 17 connected in sequence. The air source module comprises a nitrogen preparation station 1, a dynamic air storage tank 4 and an energy storage air storage tank 5. The dynamic air storage tank 4 and the energy storage air storage tank 5 are connected in parallel through pipelines. Both the dynamic air storage tank 4 and the energy storage air storage tank 5 are provided with a venting pipeline. The venting pipeline of the dynamic air storage tank 4 is provided with a venting valve a6, and the venting pipeline of the energy storage air storage tank 5 is provided with a venting valve b7; the inlet end of the dynamic air storage tank 4 is provided with an air source preparation valve a2, and the outlet end is provided with an air source management valve a8; the inlet end of the energy storage air storage tank 5 is provided with an air source preparation valve b3, and the outlet end is provided with an air source management valve b9. The pressure regulating module includes multiple pressure regulating pipelines connected in parallel, and pressure regulating valves for different volume flow rates are respectively arranged on different pressure regulating pipelines. Specifically: the pressure regulating module includes a first pressure regulating pipeline, a second pressure regulating pipeline, a third pressure regulating pipeline and a fourth pressure regulating pipeline connected in parallel. The first pressure regulating pipeline is provided with a positioning pressure reducing valve a12 and a solenoid valve a10, the second pressure regulating pipeline is provided with a positioning pressure reducing valve b13 and a solenoid valve b11, the third pressure regulating pipeline is provided with an electric pressure regulating valve 14, and the fourth pressure regulating pipeline is provided with a hydraulic pressure regulating valve 15.

[0050] Dynamic air storage tank 4 and accumulator air storage tank 5 are medium-pressure air storage tanks used to store medium-pressure nitrogen for low-density wind tunnel testing, with a maximum operating pressure of 2 MPa. Different combinations of medium-pressure air storage tanks are used to meet the requirements of different volume flow rate tests, and the pressure drop ratio of the medium-pressure air storage tanks during the active test process is controlled. This reduces the design difficulty of the pressure regulating valve in the downstream pressure regulating module and meets the high-precision pressure regulation requirements (within 2%) for low volume flow rate tests. During the active test process (after the total pressure and total temperature at the wind tunnel nozzle 17 inlet have stabilized), the air storage tank pressure drop ratio is defined by the following formula:

[0051] (1);

[0052] in Indicates the pressure of the medium pressure gas storage tank at the initial moment of the effective test process; Indicates the pressure of the medium-pressure gas storage tank at the end of the effective test process; The pressure drop of the medium pressure gas tank during the effective test; is the average pressure of the medium-pressure gas storage tank during the effective test process, and it is considered that the pressure of the medium-pressure gas storage tank decreases approximately linearly.

[0053] 1. During the effective test process, the pressure drop ratio control of the medium-pressure gas storage tank adopts a classification control strategy based on the gas volume flow rate at the outlet of the pressure regulating module. According to the different outlet volume flow rates of the pressure regulating module, the pressure regulation method is divided into three working conditions: extremely small, moderate and large. The details are as follows:

[0054] a): Test the outlet volume flow rate range of the pressure regulating module under extremely low working conditions (0L / s<G≤5L / s), using dynamic gas tank 4 (volume V1) to supply gas, with a single effective test duration of ≥30s, and controlling the pressure drop ratio of the medium-pressure gas tank during the effective test. ≤1%.

[0055] b) Test the outlet volume flow rate range of the pressure regulating module under moderate working conditions (5L / s<G≤20L / s), using dynamic gas tank 4 (volume V1) for gas supply, with a single test duration of ≥30s, and controlling the pressure drop ratio of the medium-pressure gas tank during the effective test process. ≤2%.

[0056] c) Test of the outlet volume flow rate range of the pressure regulating module under larger working conditions (20L / s<G≤120L / s), using dynamic gas storage tank 4 (volume V1) and energy storage gas storage tank 5 (volume V1) to jointly supply gas, with a single test duration of ≥30s, and controlling the pressure drop ratio of the medium-pressure gas storage tank during the effective test process ≤8%.

[0057] 2. In low-density wind tunnel tests, the outlet volume flow rate of the pressure regulating module is primarily determined by the throat cross-sectional area of ​​the selected test nozzle 17. Based on the different test conditions of the low-density wind tunnel, the total pressure, total temperature, and Mach number requirements of the wind tunnel test are determined, and nozzle 17 is selected. The test mass flow rate is calculated using the following formula:

[0058] (2);

[0059] Where G is the test mass flow rate, kg / s; C is the nitrogen flow coefficient, 0.04; The average total pressure of the wind tunnel test airflow under the selected test conditions for the low-density wind tunnel, Pa; is the throat cross-sectional area of ​​the selected nozzle 17, m 2 ; The average total temperature of the wind tunnel test airflow under the selected test conditions for the low-density wind tunnel, K.

[0060] According to the experimental mass flow conservation, the mass flow at the outlet of the pressure regulating module Equal to the mass flow rate at the inlet of nozzle 17, then:

[0061] (3);

[0062] Ignoring the internal pressure loss of the heater 16, the volume flow rate at the outlet of the pressure regulating module is approximately calculated by the following formula:

[0063] (4);

[0064] (5);

[0065] (6);

[0066] in, The average stagnation density at the outlet of the pressure regulating module under the selected test conditions of the low-density wind tunnel, kg / s; is the average stagnation density at the outlet of the pressure regulating module under the selected test conditions of the low-density wind tunnel, Pa; R is the nitrogen gas constant, 297 J / (kg*K); The average stagnation temperature at the outlet of the pressure regulating module under the test conditions of the low-density wind tunnel is approximately room temperature, 288K. Combining formulas (1) to (6), we can obtain:

[0067] (7);

[0068] From the above formula, we can see that C and R are both constants. Approximately room temperature; is the total test temperature, which is mainly determined by the anti-condensation relationship of the selected nozzle 17. Due to the limited heating technology, the total test temperature of the nozzle 17 with different Mach numbers varies relatively little, approximately 2 times; The throat area of ​​the selected nozzle 17 determines the overall variation range of the nozzle 17 tests at different Mach numbers, with a difference of approximately 200 times or more. Therefore, the outlet volume flow rate of the pressure regulating module is mainly determined by the throat cross-sectional area of ​​the selected nozzle 17. Formula (7) shows that in the low-density wind tunnel test, the classification benchmark for the pressure drop ratio classification control strategy of the medium-pressure air tank is the nozzle 17 test at different Mach numbers, using different medium-pressure air tank operation strategies.

[0069] 3. Based on the classification control strategy of the pressure drop ratio of the medium-pressure gas storage tank during the effective test process, the medium-pressure gas storage tank is designed to meet the small volume flow and high-precision test requirements of the low-density wind tunnel. According to the law of conservation of mass, the mass of the gas flowing out of the nozzle 17 during the effective test is equal to the mass of the gas flowing out of the medium-pressure gas storage tank, then:

[0070] (8);

[0071] in, is the mass of gas flowing out during the effective test, kg; is the effective test duration, s; is the gas mass in the medium-pressure gas storage tank at the initial moment of the effective test process, kg; is the gas mass in the medium-pressure gas storage tank at the end of the effective test process, kg. The low-density wind tunnel test is a small flow test. It can be assumed that the gas temperature in the medium-pressure gas storage tank remains unchanged. The gas mass in the medium-pressure gas storage tank at different times is:

[0072] (9);

[0073] (10);

[0074] (11);

[0075] (12);

[0076] in, is the gas density of the medium pressure gas storage tank at the initial moment of the effective test process, ; is the gas density of the medium pressure gas storage tank at the end of the effective test process, ; is the volume of the medium pressure gas storage tank, ; is the gas temperature of the medium pressure gas storage tank, approximately room temperature, 288K. Combining formulas (1), (2), (7) to (12), the gas source volume is Determined by the following formula:

[0077] (13);

[0078] The lowest medium pressure gas tank operating pressure at the initial moment of the effective test process is usually selected as:

[0079] (14);

[0080] in is the loss regulation ratio of the voltage regulating module, which is usually selected to be 1.4 to 1.6. Combining formulas (13) and (14), we get:

[0081] (15);

[0082] According to different test conditions of the low-density wind tunnel, the parameters such as the throat cross-sectional area and total temperature of the nozzle 17 are determined, and the corresponding pressure regulating module outlet volume flow rate is determined using formula (7) ; Using the pressure drop ratio classification control strategy of the medium pressure gas storage tank, the maximum pressure under three types of working conditions is determined respectively. , pressure drop ratio , effective test duration , using formula (15) to calculate the volume of the medium pressure gas storage tank under three working conditions The classified medium-pressure gas storage tank usage strategy based on the pressure drop ratio classification control strategy of the medium-pressure gas storage tank is:

[0083]

[0084]

[0085] (16);

[0086] The calculated volumes of the dynamic air tank 4V1 and the energy storage tank 5V2 are as follows:

[0087] (17);

[0088] (18);

[0089] In order to further improve the interchangeability efficiency of the dynamic gas storage tank 4 and the energy storage gas storage tank 5, the dynamic gas storage tank 4 and the energy storage gas storage tank 5 adopt an equal volume design strategy, then:

[0090] (19).

[0091] 4. According to the pressure regulation requirements of different pressure regulating module outlet volume flow rate range tests, pressure regulation precision control strategies based on different types of pressure regulating valves are adopted to meet the high-precision pressure regulation requirements of low-density wind tunnel small volume flow rate tests. The details are as follows:

[0092] a. For the test of the outlet volume flow rate range of the pressure regulating module under extremely small working conditions (0.4L / s≤G≤5L / s), the pressure regulating valves used are positioning pressure reducing valve a12 and positioning pressure reducing valve b13. Both pressure reducing valves are equipped with a fixed throat orifice plate or throttling nozzle, and accurately control the initial pressure of the dynamic air storage tank 4 (repeat control accuracy within 1%), so that the pressure regulation accuracy is within 1.5%, meeting the high-precision pressure regulation requirements of the extremely small volume flow range of the low-density wind tunnel.

[0093] b. For the test of the outlet volume flow rate range of the pressure regulating module under moderate operating conditions (5 L / s < G ≤ 20 L / s), a small-diameter (DN25) electric pressure regulating valve 14 is used. This pressure regulating valve has a high-precision positioning discontinuous characteristic and adopts a high-precision positioning opening method. The initial pressure of the dynamic air storage tank 4 is precisely controlled (with repeatable control accuracy within 1%), so that its pressure regulation accuracy is within 2%, meeting the high-precision pressure regulation requirements of the moderate volume flow range of the low-density wind tunnel.

[0094] c. For tests with a wide range of outlet volume flow rates (20 L / s < G ≤ 120 L / s) under larger operating conditions, a medium-caliber (DN40) hydraulic pressure regulating valve 15 is used in conjunction with PID control technology. This allows the positioning accuracy of the pressure regulating valve to be within 0.3%, and the pressure regulation accuracy to be within 2%, meeting the high-precision test requirements of a large volume flow range in low-density wind tunnels.

[0095] 5. In the volume flow rate range test at the outlet of the pressure regulating module under extremely low working conditions, the pressure regulating valve adopts a fixed throat orifice plate or a throttling nozzle, and the pressure regulating accuracy is achieved within 1.5% through the following control method. At the initial moment of the effective test process in the low-density wind tunnel, the test gas mass flow rate is:

[0096] (20);

[0097] At the end of the effective test process in the low-density wind tunnel, the test gas mass flow rate is:

[0098] (twenty one);

[0099] Ignoring the pipeline flow resistance, the pressure regulating valve is a fixed throat orifice plate or throttling nozzle during the effective test, and its throat cross-sectional area To simplify the analysis, it is assumed that the throat of the pressure regulating valve operates at the speed of sound. At the initial moment of the effective test process in the low-density wind tunnel, the gas mass flow rate of the pressure regulating valve is:

[0100] (twenty two);

[0101] At the end of the effective test process in the low-density wind tunnel, the gas mass flow rate of the pressure regulating valve is determined by the following formula:

[0102] (twenty three);

[0103] According to the law of conservation of mass, the gas mass flow rate at the initial and final moments is conserved, so:

[0104] (twenty four);

[0105] (25);

[0106] The pressure regulation accuracy during the effective wind tunnel test is determined by the following formula:

[0107] (26);

[0108] Combining formulas (1), (20) to (26), we can obtain:

[0109] (27);

[0110] In the test of the outlet volume flow rate of the minimum pressure regulating module, it can be seen from formula (27) that the pressure regulating accuracy of a single test during the effective test process of the pressure regulating valve with a fixed throat orifice plate is only related to the pressure drop ratio of the medium pressure gas tank, and is half of the pressure drop ratio. According to the pressure drop ratio classification control strategy of the medium pressure gas tank, during the test of the minimum volume flow range, the pressure drop ratio of the medium pressure gas tank is If the pressure is less than 1%, the voltage regulation accuracy of a single test reaches 0.5%.

[0111] In many tests, the initial pressure of the medium pressure gas tank was precisely controlled. , so that its repeatability Assuming that multiple repeated experiments The mean of ,but:

[0112] (28);

[0113] (29);

[0114] From formula (1), we can know that:

[0115] (30);

[0116] Combining formulas (28) to (30), we can obtain:

[0117] (31);

[0118] (32);

[0119] (33);

[0120] Combined with formula (27), the maximum deviation in multiple pressure regulation tests is determined by the maximum possible pressure difference. Therefore, the pressure regulation accuracy in multiple tests is:

[0121] (34);

[0122] Combining formulas (27), (28), (32), (33) and (34), and because 、 is a small quantity and ignoring the high-order small quantities, we can get:

[0123] (35);

[0124] From formula (35), we can see that in the test of the outlet volume flow rate of the minimum pressure regulating module, the pressure regulation accuracy in multiple tests is determined by the single test accuracy and the repeatability accuracy of the initial pressure of the medium pressure gas tank, and they are linearly superimposed. Based on the above analysis, in the test of the outlet volume flow rate of the minimum pressure regulating module, the pressure drop ratio classification control strategy of the medium pressure gas tank can be used to determine the pressure drop ratio of the medium pressure gas tank. ≤1%, according to the pressure regulation accuracy control strategy based on different types of pressure regulating valves ≤1%, then test the voltage regulation accuracy multiple times ≤1.5%, meeting the pressure regulation control accuracy of low-density wind tunnels.

[0125] 6. In the moderate pressure regulating module outlet volume flow rate range test, the pressure regulating valve uses a small-diameter (e.g. DN25) electric pressure regulating valve 14, and the following control method is used to make its pressure regulation accuracy within 2%. The small-diameter electric pressure regulating valve 14 does not have the high-positioning accuracy control function of the continuous opening of the valve core position, but only has the high-positioning accuracy control of the step opening of the valve core position (e.g. stroke interval 1mm). When conducting the moderate pressure regulating module outlet volume flow rate range test, the pressure regulating valve is always opened to a certain valve opening in the single-state test, and the opening is kept unchanged during the effective test process, so that the throttling throat cross-sectional area remains unchanged. Using the same analysis method as the pressure regulation progress of the extremely small pressure regulating module outlet volume flow rate range test, the pressure regulation accuracy calculation results such as formulas (27) and (35) can be obtained. Based on this analysis, in the moderate pressure regulating module outlet volume flow rate test, the pressure regulating valve is moderately opened at a certain valve opening in the single-state test, and the pressure drop ratio classification control strategy of the medium-pressure gas storage tank is known. ≤2%, according to the pressure regulation accuracy control strategy based on different types of pressure regulating valves ≤1%, then test the voltage regulation accuracy multiple times ≤2%, meeting the pressure regulation control accuracy of low-density wind tunnels.

[0126] VII. For tests covering a wide range of pressure-regulating module outlet volume flow rates, a medium-caliber (DN40) hydraulic pressure-regulating valve 15 was used. In conjunction with a PID pressure-regulating control scheme, the pressure-regulating valve achieved a positioning accuracy of 0.3%, achieving a pressure-regulating accuracy within 2%. Under these test conditions, the minimum volume flow rate after the pressure-regulating valve was 20 L / s. Using a DN40 liquid-hole pressure-regulating valve, according to the valve regulation characteristic calculation method, the velocity coefficient of the pipeline after the pressure-regulating valve was >0.05. With an elliptical valve core, the linear regulation range for the pressure recovery coefficient was between 0.1 and 0.8, and the valve stroke ratio was between 10% and 40%. For tests with a volume flow rate of 20 L / s, assuming a valve core positioning accuracy of within 0.3%, the pressure-regulating accuracy within the linear regulation range of the pressure recovery coefficient of 0.3 to 0.8, combined with the PID control strategy, was within 2%, meeting the pressure regulation requirements of low-density wind tunnels.

[0127] 8. Based on the aforementioned designed intake pressure regulating system, in the test of the outlet volume flow rate range of the pressure regulating module under extremely low working conditions, the pressure regulation method is as follows:

[0128] a1: Select dynamic gas storage tank 4 to supply gas for the test within the minimum test volume flow range;

[0129] a2: The initial pressure of the dynamic air storage tank 4 is reduced by opening the air release valve a6 to release air from the dynamic air storage tank 4 to the environment, or the initial pressure of the dynamic air storage tank 4 is increased by quickly opening the air source management valve a8 and the air source management valve b9 to charge the dynamic air storage tank from the energy storage tank 5. The initial pressure of the dynamic air storage tank 4 required by the test state is accurately controlled to ensure that the initial pressure accuracy is within 1%;

[0130] a3: Open the gas source management valve a8;

[0131] a4: Based on the test state requirements, choose to open the solenoid valve a10, or choose to open the solenoid valve b11, or choose to open the solenoid valve a10 and the solenoid valve b11 at the same time, and then use the positioning pressure reducing valve a12, or the positioning pressure reducing valve b13, or both to reduce the pressure. After the decompressed air flow is heated by the heater 16, a test air flow medium with stable total pressure and total temperature is formed at the inlet of the nozzle 17, and the pressure regulation control accuracy reaches within 1.5%.

[0132] IX. Based on the aforementioned designed intake pressure regulating system, in the pressure regulating module outlet volume flow rate range test under moderate working conditions, the pressure regulation method is as follows:

[0133] b1: Select dynamic gas storage tank 4 to supply gas for the test within a moderate test volume flow range;

[0134] b2: The initial pressure of the dynamic air storage tank 4 is reduced by releasing air from the dynamic air storage tank 4 to the environment by opening the air release valve a6, or the initial pressure of the dynamic air storage tank 4 is increased by quickly opening the air source management valve a8 and the air source management valve b9 to charge the dynamic air storage tank from the energy storage tank 5. The initial pressure of the dynamic air storage tank 4 required by the test state is accurately controlled to ensure that the initial pressure accuracy is controlled within 1%;

[0135] b3: Open the gas source management valve a8;

[0136] b4: According to the test state requirements, open the electric pressure regulating valve 14 to a certain opening and maintain it. After the decompressed air flow is heated by the heater 16, a test air flow medium with stable total pressure and total temperature is formed at the inlet of the nozzle 17. The pressure regulation control accuracy is within 2%.

[0137] 10. Based on the aforementioned designed intake pressure regulating system, in the test of the outlet volume flow rate range of the pressure regulating module under a larger working condition, the pressure regulation method is as follows:

[0138] c1: Dynamic gas storage tank 4 and energy storage tank 5 are selected to supply gas for the test with a larger test volume flow range;

[0139] c2: According to the test requirements, either release air to the environment by opening the air release valve a6 and the air release valve b7 to reduce the initial pressure of the dynamic air storage tank 4 and the accumulator air storage tank 5, or increase the initial pressure of the dynamic air storage tank 4 and the accumulator air storage tank 5 by opening the nitrogen preparation station 1, the gas source preparation valve a2, and the gas source preparation valve b3 to fill the tanks with air. Set the initial pressure of the gas storage tanks to a certain level (for example, 1.8 MPa, 1.0 MPa) so that the pressure regulating valve operates within its linear adjustment range;

[0140] c3: Open the air source management valve a8 and the air source management valve b9;

[0141] c4: The PID control strategy is used to implement feedback control of the valve position of the hydraulic pressure regulating valve 15. After the air flow is heated by the heater 16, a test air flow medium with stable total pressure and total temperature is formed at the inlet of the nozzle 17. The pressure regulation control accuracy reaches within 2%.

[0142] The present invention provides an air intake pressure regulating system and a pressure regulating valve method for three different volume flow rates after pressure regulating valves. The system adopts the method of controlling the pressure drop of the air storage tank, controlling the initial pressure of the air storage tank, and using multiple types of pressure regulating valves to replace the conventional wind tunnel's pressure grade air storage tank + single-stage or multi-stage PID control pressure regulating valve scheme. The system overcomes the inherent characteristics of small-caliber pressure regulating valves, such as poor continuity of high-precision valve position control, narrow linear adjustment range, and low pressure regulation accuracy, and meets the high-precision pressure regulation requirements of low-density wind tunnel tests with small volume flow rates and a wide volume flow rate range.

[0143] ① An air inlet pressure regulating system and pressure regulating method for testing volume flow rates (0.4L / s to 5L / s) after a pressure regulating valve under extremely low operating conditions. By controlling the pressure drop of the medium-pressure gas storage tank to ≤1% during the effective test process and reducing the pressure using a fixed-throat orifice plate or throttling nozzle, the pressure regulation accuracy for a single test is maintained within 0.5%. By controlling the initial pressure accuracy of the medium-pressure gas storage tank to within 1%, combined with single-shot pressure regulation accuracy control technology, the pressure regulation accuracy for multiple tests is maintained within 1.5%. A pressure regulation solution that controls the gas source pressure drop ratio and the initial gas storage pressure, combined with a fixed-throttle-diameter pressure reducing valve, replaces the ultra-small-diameter (DN10 and below) variable-throat pressure regulating valve (pressure regulation accuracy less than 5%) solution. This overcomes the insufficient pressure regulation accuracy of ultra-small-diameter pressure regulating valves and meets the high-precision pressure regulation requirements for ultra-low volume flow tests in low-density wind tunnels.

[0144] ② An inlet pressure regulating system and pressure regulating method for post-pressure regulating valve volume flow tests under moderate operating conditions (5 L / s to 20 L / s). By controlling the pressure drop of the medium-pressure gas storage tank to ≤2% during the effective test process and utilizing an electric pressure regulating valve 14 with a fixed opening, the pressure regulation accuracy for a single test is maintained within 1%. By controlling the initial pressure of the medium-pressure gas storage tank to within 1% and combining single-shot pressure regulation accuracy control technology, the pressure regulation accuracy for multiple tests is maintained within 2%. A pressure regulation scheme that controls the gas source pressure drop ratio, the initial gas storage pressure, and combines a fixed opening setting for the pressure regulating valve overcomes the discontinuous nature of high-precision valve position control for small-diameter (e.g., DN25) pressure regulating valves, achieving the high-precision pressure regulation requirements for moderate volume flow tests in low-density wind tunnels. Compared with the air inlet pressure regulating system for the extremely small volume flow test, the single electric pressure regulating valve 14 with a fixed opening setting is adopted. By setting different valve position openings, multiple pressure reducers with fixed throat diameters can be obtained, so that the initial pressure setting of a single gas tank can meet the pressure regulation requirements of more different test conditions.

[0145] ③ An inlet pressure regulating system and method for testing volume flow rates (20L / s to 120L / s) after a pressure regulating valve under larger operating conditions. By controlling the pressure drop of the medium-pressure gas tank to ≤8% during the effective test, the initial pressure of the medium-pressure gas tank is controlled in stages (e.g., 1MPa, 1.8MPa) according to test requirements. PID control is then used to control a medium-caliber (DN40) hydraulic pressure regulating valve 15 with high positioning accuracy, achieving a test pressure regulation accuracy of less than 2%. By controlling the initial pressure of the medium-pressure gas tank in stages, the pressure recovery coefficient before and after the pressure regulating valve is moderate, ensuring that the hydraulic pressure regulating valve 15 always operates within a high-precision linear regulation range, overcoming the narrow linear regulation range of small-caliber pressure regulating valves.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pressure regulating method for an air inlet pressure regulating system for a low-density wind tunnel, characterized in that: The air intake pressure regulation system includes an air source module, a pressure regulating module, a heater, and a nozzle that are connected in sequence. The air source module includes a nitrogen preparation station, a dynamic air storage tank, and an energy storage air storage tank. The dynamic air storage tank and the energy storage air storage tank are connected in parallel via pipelines. The inlet and outlet ends of the dynamic air storage tank and the energy storage tank are both equipped with valves. The pressure regulating module includes multiple pressure regulating pipelines connected in parallel, and different pressure regulating pipelines are respectively provided with pressure regulating valves for different volume flow rates. The dynamic gas storage tank and the energy storage gas storage tank are both medium-pressure gas storage tanks with a maximum operating pressure of 2MPa; the dynamic gas storage tank and the energy storage gas storage tank are both provided with a venting pipeline, and the venting pipeline is provided with a venting valve; The pressure regulating module includes a first pressure regulating pipeline, a second pressure regulating pipeline, a third pressure regulating pipeline and a fourth pressure regulating pipeline connected in parallel, the first pressure regulating pipeline is provided with a positioning pressure reducing valve a and a solenoid valve a, the second pressure regulating pipeline is provided with a positioning pressure reducing valve b and a solenoid valve b, the third pressure regulating pipeline is provided with an electric pressure regulating valve, and the fourth pressure regulating pipeline is provided with a hydraulic pressure regulating valve; The inlet end of the dynamic gas storage tank is provided with a gas source preparation valve a, and the outlet end is provided with a gas source management valve a; the inlet end of the energy storage gas storage tank is provided with a gas source preparation valve b, and the outlet end is provided with a gas source management valve b; The pressure regulation method is as follows: according to the requirements of different volume flow rate tests, different medium-pressure gas storage tank combinations are used to control the pressure drop ratio of the medium-pressure gas storage tanks during the effective test process. In addition, a pressure regulation accuracy control strategy based on different types of pressure regulating valves is adopted to meet the high-precision pressure regulation requirements of small volume flow rate tests. The pressure regulation method is divided into multiple working conditions according to the different outlet volume flow rates of the pressure regulating module. In the test of the outlet volume flow rate range of the pressure regulating module under extremely small working conditions, the pressure regulation method is as follows: a1: Select a dynamic gas storage tank to supply gas for the test within the minimum test volume flow range; a2: Release air by opening the bleed valve a to reduce the initial pressure of the dynamic gas storage tank, or increase the initial pressure of the dynamic gas storage tank by opening the gas source management valve a and gas source management valve b to charge the dynamic gas storage tank from the accumulator gas tank. Accurately control the initial pressure of the dynamic gas storage tank required by the test state, and control the initial pressure accuracy within 1%; a3: Open the gas source management valve a; a4: According to the test state requirements, open the solenoid valve a and / or the solenoid valve b, use the positioning pressure reducing valve a and / or the positioning pressure reducing valve b to reduce the pressure. After the decompressed air flow is heated by the heater, a test air flow medium with stable total pressure and total temperature is formed at the nozzle inlet, and the pressure regulation control accuracy is within 1.5%.

2. The pressure regulating method of the air intake pressure regulating system for a low-density wind tunnel according to claim 1, characterized in that: In the moderate operating conditions test of the outlet volume flow rate range of the pressure regulating module, the pressure regulation method is as follows: b1: Select a dynamic gas storage tank to supply gas for the test within a moderate test volume flow range; b2: Release the air by opening the air release valve a to reduce the initial pressure of the dynamic air storage tank, or increase the initial pressure of the dynamic air storage tank by opening the air source management valve a and the air source management valve b to charge the dynamic air storage tank from the energy storage tank. Accurately control the initial pressure of the dynamic air storage tank required by the test state, so that the initial pressure accuracy is controlled within 1%; b3: Open the gas source management valve a; b4: According to the test state requirements, open the electric pressure regulating valve to a certain opening and maintain it. After the decompressed air flow is heated by the heater, a test air flow medium with stable total pressure and total temperature is formed at the nozzle inlet. The pressure regulation control accuracy is within 2%.

3. The pressure regulating method of the air intake pressure regulating system for a low-density wind tunnel according to claim 1, characterized in that: In the test of the outlet volume flow rate range of the pressure regulating module under larger working conditions, the pressure regulation method is as follows: c1: Select dynamic gas storage tanks and energy storage tanks to supply gas for the test with a larger test volume flow range; c2: According to the test requirements, release air by opening the air release valve a and the air release valve b to reduce the initial pressure of the dynamic air storage tank and the accumulator air storage tank respectively; or increase the initial pressure of the dynamic air storage tank and the accumulator air storage tank by opening the nitrogen preparation station and the gas source preparation valve a and the gas source preparation valve b to inflate the tanks. Set the initial pressure of the two gas storage tanks so that the pressure regulating valve operates within its linear adjustment range; c3: Open the gas source management valve a and gas source management valve b; c4: The PID control strategy is used to implement feedback control of the valve position of the hydraulic pressure regulating valve. After the air flow is heated by the heater, a test air flow medium with stable total pressure and total temperature is formed at the nozzle inlet, and the pressure regulation control accuracy is within 2%.

4. The pressure regulating method of the air intake pressure regulating system for a low-density wind tunnel according to claim 1, characterized in that: During the effective test, the pressure drop ratio control of the medium-pressure gas storage tank adopts a classification control strategy based on the gas volume flow rate at the outlet of the pressure regulating module, specifically: Minimum working condition: When the outlet volume flow rate range of the pressure regulating module is 0L / s<G≤5L / s, a dynamic gas storage tank is used for gas supply, and the effective test duration of a single test is ≥30s. The pressure drop ratio of the medium-pressure gas storage tank during the effective test is controlled. ≤1%; Moderate working conditions: When the outlet volume flow rate of the pressure regulating module is within the range of 5L / s<G≤20L / s, a dynamic gas storage tank is used for gas supply, and the single test duration is ≥30s. The pressure drop ratio of the medium-pressure gas storage tank during the effective test process is controlled. ≤2%; Large working condition: When the outlet volume flow rate range of the pressure regulating module is 20L / s<G≤120L / s, the dynamic gas storage tank and the energy storage tank are used to supply gas together. The single test duration is ≥30s. The pressure drop ratio of the medium pressure gas storage tank during the effective test process is controlled. ≤8%.

5. The pressure regulating method of the air intake pressure regulating system for a low-density wind tunnel according to claim 4, characterized in that: According to the pressure regulation requirements of different pressure regulating module outlet volume flow rate range tests, pressure regulation accuracy control strategies based on different types of pressure regulating valves are adopted to meet the high-precision pressure regulation requirements of low-density wind tunnel small volume flow rate tests, as follows: When the outlet volume flow rate of the pressure regulating module is 0.4L / s≤G≤5L / s, the pressure regulating valve adopts positioning pressure reducing valve a and positioning pressure reducing valve b, and accurately controls the initial pressure of the dynamic gas storage tank to achieve a pressure regulation accuracy within 1.5%; When the outlet volume flow rate of the pressure regulating module is 5 L / s<G≤20L / s, a DN25 electric pressure regulating valve is used to accurately control the initial pressure of the dynamic gas storage tank so that the pressure regulation accuracy is within 2%; When the outlet volume flow rate of the pressure regulating module is 20L / s<G≤120L / s, a DN40 hydraulic pressure regulating valve is used in conjunction with PID control technology to control the positioning accuracy of the pressure regulating valve within 0.3%, so that its pressure regulation accuracy reaches within 2%.

6. The pressure regulating method for an air intake pressure regulating system for a low-density wind tunnel according to claim 5, characterized in that: When the outlet volume flow rate range of the pressure regulating module is 0.4L / s≤G≤5L / s, positioning pressure reducing valve a and positioning pressure reducing valve b are used as pressure regulating valves to accurately control the initial pressure of the dynamic gas storage tank, with a repeatable control accuracy within 1%, so that the pressure regulation accuracy is within 1.5%; When the outlet volume flow rate range of the pressure regulating module is 5L / s<G≤20L / s, the pressure regulating valve adopts a DN25 electric pressure regulating valve to accurately control the initial pressure of the dynamic gas storage tank, with a repeatable control accuracy within 1%, so that the pressure regulation accuracy can reach within 2%; When the outlet volume flow rate range of the pressure regulating module is 20 L / s<G≤120L / s, the pressure regulating valve uses a DN40 hydraulic pressure regulating valve combined with PID control technology as the pressure regulating valve. The positioning accuracy of the pressure regulating valve is within 0.3%, so that the pressure regulation accuracy reaches within 2%.

7. The pressure regulating method of the air inlet pressure regulating system for a low-density wind tunnel according to claim 6, characterized in that: In the test where the outlet volume flow rate of the pressure regulating module is in the range of 0.4L / s≤G≤5L / s, both the positioning pressure reducing valve a and the positioning pressure reducing valve b adopt a fixed throat orifice plate or a throttling nozzle.

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