Bimodal oxygen control continuous cooling closed-loop fluid system and precise control method

Abstract

According to the bimodal oxygen control continuous cooling closed-loop fluid system and the precise control method, precise control over the oxygen content in closed-loop fluid equipment is guaranteed; the continuous cooling closed-loop fluid system comprises a compressor section, a liquid nitrogen injection section, a heat exchange section, a stable section, a test cabin section, a diffusion unit, an oxygen injection section and a steering unit which are sequentially connected and form a circulation shaped like a Chinese character'hui ', an oxygen content detection assembly is assembled between the stable section and the test cabin section, and an oxygen injection assembly is assembled on the oxygen injection section. The oxygen injection assembly comprises a feed-forward control pipeline and a feedback control pipeline, receives a feed-forward control instruction of the PLC, and automatically injects along with liquid nitrogen according to liquid nitrogen injection data by combining an ideal gas equation with a correction equation or an oxygen molecule demand calculated by a simulation mode value; the feedback control pipeline receives a PID feedback control instruction, and the feedback control instruction calculates the demanded quantity of oxygen supplementation molecules through real-time oxygen content data obtained by the oxygen content measuring assembly and liquid nitrogen injection data.

Description

Technical Field

[0001] The present invention relates to the field of closed-loop fluid system tests. Specifically, it relates to a dual-mode oxygen control continuous cooling closed-loop fluid system and a precise control method. Background Art

[0002] Continuous closed-loop fluid systems can be applied to the aerodynamic design and performance evaluation of aircraft, missiles, satellites and other aircraft. By simulating the airflow conditions of the aircraft in different flight states, this closed-loop fluid system helps researchers optimize the aircraft's shape design and adjust flight control strategies to improve the performance and safety of the aircraft.

[0003] Generally, the operating medium of continuous closed-loop fluid systems is mainly air. However, in some special tests with strict requirements for the test environment, nitrogen, carbon dioxide, etc. may also be used as the operating medium. For the requirement that the operating medium is dry nitrogen with a temperature range of 105K to 334K, and the incoming oxygen content of the equipment is in the range of (1000 - 3000 ppm), and at the same time, precise oxygen content control (≤ ±15 ppm) needs to be achieved, there is currently no equipment that meets this requirement. The present invention conducts research and development on continuous closed-loop fluid systems for this task, and designs an oxygen content stable control system based on the injection of liquid nitrogen and its precise control method, thus achieving the design task. Summary of the Invention

[0004] The purpose of the present invention is to provide a dual-mode oxygen control continuous cooling closed-loop fluid system and a precise control method, which can complete the research and development task while ensuring precise control of the oxygen content in the closed-loop fluid equipment.

[0005] The embodiments of the present invention are implemented as follows:

[0006] A dual-mode oxygen control continuous cooling closed-loop fluid system. This continuous cooling closed-loop fluid system includes a compressor section, a liquid nitrogen injection section, a heat exchange section, a stabilization section, a test chamber section, a diffuser unit, an oxygen injection section, and a steering unit that are connected in sequence to form a "return" - shaped cycle. An oxygen content detection component is assembled between the stabilization section and the test chamber section, and an oxygen injection component is assembled in the oxygen injection section. The oxygen injection component includes:

[0007] A feedforward control pipeline, which serves as a large-flow gas path during the oxygen injection process, receives the feedforward control instruction of the PLC. The feedforward control instruction is automatically accompanied by the liquid nitrogen injection according to the oxygen molecule demand calculated by the ideal gas equation combined with the correction equation or the simulation mode value based on the liquid nitrogen injection data;

[0008] The feedback control pipeline, as a small-flow gas pipeline during the oxygen injection process, receives PID feedback control instructions, which are calculated based on the real-time oxygen content data obtained by the oxygen content measurement component and the oxygen supplementation molecule demand calculated from the liquid nitrogen injection data.

[0009] In a preferred embodiment of the present invention, the above-mentioned feedforward control pipeline includes a first pressure and temperature sensor, a first pneumatic regulating valve, a first vortex flowmeter, a first pneumatic valve, and a second pressure and temperature sensor, which are connected in sequence, and one of the input ends of the oxygen injection rake. The real-time data of the first pneumatic valve is fed back to the PID control end.

[0010] In a preferred embodiment of the present invention, the above-mentioned feedback control pipeline includes large, medium, and small oxygen supplementation pipelines arranged in parallel. The large oxygen supplementation pipeline includes a second pneumatic regulating valve, a second vortex flowmeter, and a second pneumatic valve connected in sequence; the medium oxygen supplementation pipeline includes a third pneumatic valve and a large mass flow control valve connected in sequence; the small oxygen supplementation pipeline includes a fourth pneumatic valve and a small mass flow control valve connected in sequence. The real-time data of the second pneumatic valve and the large / small mass flow control valves are fed back to the PID control end. The output ends of the large, medium, and small oxygen supplementation pipelines converge to the other input end of the oxygen injection rake.

[0011] In a preferred embodiment of the present invention, the above-mentioned oxygen injection rake includes:

[0012] The front section of the oxygen injection rake. The front section of the oxygen injection rake is composed of a cylinder, a transition body, and an oblate body connected in sequence. The oblate body has an oblate body structure with a "playground-shaped" cross-section, and it smoothly transitions from the cylinder to the oblate body through the transition body. The cross-sectional areas of the internal air flow pipelines of the cylinder, the transition body, and the oblate body are the same. The other end of the cylinder is equipped with a gas supply pipe docking flange, and the other end of the oblate body is equipped with a closed-loop fluid system docking flange.

[0013] The rear section of the oxygen injection rake. The rear section of the oxygen injection rake is an oblate plate with a "playground-shaped" cross-section. Exhaust holes are arranged at equal intervals on the midlines of the two arc-shaped sides of the rear section of the oxygen injection rake. The cross-section of the internal air flow pipeline of the rear section of the oxygen injection rake is the same as that of the internal air flow pipeline of the oblate body.

[0014] In a preferred embodiment of the present invention, a gas source pretreatment component is also connected before the above-mentioned oxygen injection component. The gas source pretreatment component includes:

[0015] The oxygen injection pipeline, which includes an air access port and / or an oxygen access port;

[0016] The drying and filtering pipeline, which is connected to the output end of each oxygen injection pipeline;

[0017] The dew point detection pipeline is a branch pipeline connecting to the output end of the drying and filtering pipeline. The dew point detection pipeline includes a branch pneumatic valve, a pre-processor, and a dew point meter connected in sequence, ensuring that the gas dew point reaches below -70°C;

[0018] The automatic pressure / flow regulation pipeline is the main pipeline connecting to the drying and filtering pipeline. An automatic pressure / flow regulating valve is provided on each pipeline of the automatic pressure / flow regulation pipeline, and a safety valve is assembled on the confluence pipeline of the automatic pressure / flow regulation pipeline.

[0019] In a preferred embodiment of the present invention, at least two groups of the above oxygen content detection components are provided, one group is assembled at the rear end of the stable section, and the other group is assembled at the rear end of the test chamber section.

[0020] In a preferred embodiment of the present invention, the parameter configuration of the above feedback control pipeline is as follows:

[0021] The large oxygen supply pipeline has a nominal diameter of DN50, a flow range of 200 - 500 Nm 3 / h, with a control accuracy of ±2%;

[0022] The medium oxygen supply pipeline has a nominal diameter of DN25, a flow range of 50 - 200 Nm 3 / h, with a control accuracy of ±0.5%;

[0023] The small oxygen supply pipeline has a nominal diameter of DN10, a flow range of 5 - 50 Nm 3 / h, with a control accuracy of ±0.1%.

[0024] A precise control method for a dual-mode oxygen control continuous cooling closed-loop fluid system, including the continuous cooling closed-loop fluid system described in any one of the above, the precise control method includes the following steps:

[0025] Read the liquid nitrogen injection data to obtain the liquid nitrogen injection flow rate parameter and injection time parameter of the liquid nitrogen injection section in real time;

[0026] Monitor the oxygen content in real time through the oxygen content detection component configured in the closed-loop fluid equipment system to collect the oxygen content reference value in the set time interval before injection;

[0027] When the liquid nitrogen injection flow rate is lower than the preset threshold, calculate the air compensation flow rate according to the real-time liquid nitrogen injection flow rate in proportion, and control the oxygen injection component to start injection synchronously;

[0028] When the liquid nitrogen injection flow rate exceeds the preset threshold, record the total liquid nitrogen injection volume, and the oxygen injection component injects the oxygen-containing gas flow at the maximum supply flow rate until the cumulative injection volume reaches the compensation volume corresponding to the total liquid nitrogen injection volume.

[0029] In a preferred embodiment of the present invention, the setting time interval of the above oxygen content reference value is a sliding window of 2-10 seconds before the liquid nitrogen injection.

[0030] In a preferred embodiment of the present invention, the above preset threshold is 80%-95% of the maximum flow rate of the oxygen injection component.

[0031] The beneficial effects of the embodiments of the present invention are as follows:

[0032] 1. Dual-mode precise control ability: Through the synergistic effect of the feedforward control pipeline (large flow rate) and the feedback control pipeline (small flow rate), both the rapid oxygen compensation response accompanied by liquid nitrogen injection (feedforward control response time ≤ 0.5 seconds) is achieved, and the oxygen content control accuracy (±5 ppm) is ensured through PID closed-loop regulation, solving the technical contradiction that the traditional single control mode cannot balance rapidity and accuracy;

[0033] 2. Improved dynamic compensation efficiency: The feedforward control calculates the oxygen molecule demand in real time based on the liquid nitrogen injection data, and uses the ideal gas equation combined with the CFD simulation correction coefficient (correction error ≤ 3%) to make the compensation action advance the oxygen content detection feedback signal, shortening the system stabilization time by 40%-60%, which is especially suitable for the transient control of the high-speed cooling process (cooling rate ≥ 50°C / min);

[0034] 3. Enhanced anti-interference ability: The liquid nitrogen injection flow prediction model (ARIMA time series analysis) is embedded in the feedforward-feedback composite control algorithm, which can predict the oxygen content fluctuation trend of the system 3-5 seconds in advance, combined with real-time PID parameter tuning (Ziegler-Nichols optimization method), so that the oxygen content fluctuation amplitude of the system remains ≤ ±10 ppm when the liquid nitrogen injection flow rate suddenly changes (≥ 30% of the rated value / s).

[0035] 4. Enhanced multi-condition adaptability: Through the dynamic switching of the simulation mode value database (covering the temperature range of 105K to 334K) and the real-time correction equation, the system can still maintain the control accuracy under extreme test conditions, meeting the wide-range environmental requirements of aerospace material testing (cross-temperature zone test switching time ≤ 5 minutes).

[0036] 5. Innovative control delay compensation: A transmission delay calculation module (real-time calculation based on pipeline volume and flow rate) is introduced in the pipeline design to perform time-phase compensation on the feedforward control instruction (compensation accuracy ±0.1 s), eliminating the overshoot phenomenon caused by the physical delay of gas transmission, and controlling the overshoot of the system step response within 5%. Description of the Drawings

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0038] Figure 1 Schematic structural diagram of the continuous cooling closed-loop fluid system for the embodiments of the present invention;

[0039] Figure 2 Schematic diagram of the pipeline connection of the oxygen precise control system for the embodiments of the present invention;

[0040] Figure 3 Schematic structural diagram of the oxygen injection rake for the embodiments of the present invention;

[0041] Figure 4 Flowchart of the use of the continuous cooling closed-loop fluid system for the embodiments of the present invention.

[0042] Icons: Compressor section 110; Heat exchange section 120; Stabilization section 130; Test chamber section 140; Diffuser unit 150; Oxygen injection section 160; Steering unit 170; Oxygen content detection component 180; Oxygen injection component 190; Feedforward control pipeline 191; First pressure and temperature sensor 1911; First pneumatic regulating valve 1912; First vortex flowmeter 1913; First pneumatic valve 1914; Second pressure and temperature sensor 1915; Feedback control pipeline 192; Second pneumatic regulating valve 1921; Second vortex flowmeter 1922; Second pneumatic valve 1923; Third pneumatic valve 1924; Large mass flow control valve 1925; Fourth pneumatic valve 1926; Small mass flow control valve 1927; Air access port 1931; Oxygen access port 1932; Dry filter pipeline 1933; Branch pneumatic valve 1934; Pretreatment unit 1935; Dew point meter 1936; Automatic pressure / flow regulation pipeline 1937; Cylinder 1941; Transition body 1942; Oval body 1943; Gas supply pipe docking flange 1944; Rear section of oxygen injection rake 1945; Exhaust hole 1946; Closed-loop fluid system docking flange 1947; Isolation valve 001. Detailed implementation manners

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0044] Accordingly, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0045] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0046] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more complete and comprehensive, and will fully convey the concept of the example embodiments to those skilled in the art.

[0047] In addition, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present application. However, those skilled in the art will realize that the technical solutions of the present application can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be used. In other cases, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the present application.

[0048] The block diagrams shown in the drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0049] The flowcharts shown in the drawings are merely illustrative and do not necessarily include all content and operations / steps, nor are they necessarily executed in the order described. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined. Therefore, the actual execution order may change according to the actual situation.

[0050] First Embodiment

[0051] In this embodiment, the continuous cooling closed-loop fluid system adopted uses low-temperature dry nitrogen with a temperature in the range of 105K to 334K as the operating medium. The outlet pressure of this gas source is 1 MPa, and the maximum usable flow rate it can provide can reach 1400 Nm 3 / h; the liquid nitrogen injection flow rate ranges from 0 to 315 Kg / s; the dew point of the injected dry gas is lower than or equal to -70°C. To meet the requirement of the test for the oxygen content of the incoming flow of this equipment to be in the range of 1000 - 3000 ppm and to achieve precise control of the incoming oxygen content (error range ≤ ±15 ppm), an oxygen precise control system suitable for this equipment is specially developed.

[0052] Please refer to Figure 1 , this embodiment provides a dual-mode oxygen control continuous cooling closed-loop fluid system. This continuous cooling closed-loop fluid system includes a compressor section 110, a liquid nitrogen injection section, a heat exchange section 120, a stabilization section 130, a test chamber section 140, a diffuser unit 150, an oxygen injection section 160, and a steering unit 170 that are connected in sequence to form a "return" shaped loop. An oxygen content detection component 180 is assembled between the stabilization section 130 and the test chamber section 140, and an oxygen injection component 190 is assembled in the oxygen injection section 160.

[0053] In this embodiment, the oxygen injection system equipment injects dry oxygen-containing gas at the position between the diffuser unit 150 and the steering unit 170. At the same time, the oxygen content measurement point will be set at the test chamber section 140 and its upstream position. Thus, the injected oxygen-containing gas must pass through the entire equipment loop before reaching the oxygen content measurement point. In view of this, the oxygen content control system needs to have strong anti-interference ability (i.e., to cope with the mutual interference between the injection amount of dry oxygen, the injection amount of liquid nitrogen, and the discharge amount of gaseous nitrogen), and good anti-large lag performance (due to the long distance between the oxygen content measurement point and the oxygen injection point). In response to the above situation, this embodiment designs a new oxygen injection component 190, which includes:

[0054] A feedforward control pipeline 191. The feedforward control pipeline 191 serves as the large-flow gas path during the oxygen injection process and receives the feedforward control instruction from the PLC. The feedforward control instruction automatically follows the liquid nitrogen injection according to the oxygen molecule demand calculated by the ideal gas equation combined with the correction equation or the simulation mode value based on the liquid nitrogen injection data.

[0055] A feedback control pipeline 192. The feedback control pipeline 192 serves as the small-flow gas path during the oxygen injection process and receives the PID feedback control instruction. The feedback control instruction calculates the supplementary oxygen molecule demand through the real-time oxygen content data obtained by the oxygen content measurement component and the liquid nitrogen injection data.

[0056] Among them, the feedforward control pipeline 191 includes a first pressure and temperature sensor 1911, a first pneumatic control valve 1912, a first vortex flowmeter 1913, a first pneumatic valve 1914, and a second pressure and temperature sensor 1915 that are connected in sequence, and one of the inputs of the oxygen injection rake. The real-time data of the first pneumatic valve 1914 is fed back to the PID control end. The first pneumatic control valve 1912 is a pilot-operated electromagnetic quick-opening valve, and the opening response time ≤ 100 ms.

[0057] Air or pure oxygen automatically adjusts the gas pressure in the pipe through the pneumatic regulating valve to provide a constant pressure difference that meets the working pressure. The current design pressure difference at both ends of the pipeline is 0.4Mpa; after the pressure regulating valve, add a pressure sensor and a temperature sensor in front of the closed-loop fluid equipment to monitor the working pressure and temperature, and use the pressure and temperature sensors of the pneumatic pressure regulating valve to automatically compensate for the pressure. The main goal of automatic pressure regulation is to control and maintain a stable pressure difference in the gas circuit. Since the test pressure of the main equipment is a variable, in order to obtain a stable flow in the gas circuit, the pressure difference at both ends of the gas circuit must also be relatively stable.

[0058] The difficulties in the oxygen injection process and the innovations made in this embodiment are:

[0059] ① During the test operation of the closed-loop fluid equipment, liquid nitrogen may be automatically added to the equipment system at any time. However, the addition of liquid nitrogen will cause the oxygen content ppm value to change. When the oxygen content ppm is stably controlled, this random interference factor must be considered. To this end, this embodiment eliminates this random interference by designing a large flow gas path that automatically accompanies the liquid nitrogen injection;

[0060] ② By reading the injection-related data of liquid nitrogen, such as the liquid nitrogen injection flow rate and liquid nitrogen injection time, the corresponding air to be injected is controlled. Specifically, by accurately regulating the air flow rate and air injection time, it is matched with the liquid nitrogen injection flow rate, time and even the total injection amount, so as to achieve the function of stabilizing the system oxygen content ppm value;

[0061] ③ In consideration of the automatic injection function, for 1400Nm 3 In the case where the gas source supply of 1000 t / h may not be compatible with the large-scale injection of liquid nitrogen, the automatic accompanying injection will implement the injection operation at the maximum flow rate of air until the total injection amount of oxygen reaches the ppm value before the liquid nitrogen injection.

[0062] ④ When the liquid nitrogen injection flow rate is at a low level, the air injection flow rate can match the liquid nitrogen flow rate. At this time, the automatic accompanying injection can be basically synchronized with the liquid nitrogen injection without obvious delay.

[0063] In terms of the output innovation of the feedforward command, we have made the following improvements: During the test phase of the closed-loop fluid device, considering the total pressure control requirement of the device, when the device pressure reaches a specific threshold, a pressure relief procedure will be executed. Therefore, the device system is not a closed system. During the pressure relief process, some of the injected nitrogen and oxygen molecules will be lost. Therefore, the total number of nitrogen or oxygen molecules in the device is not equal to the cumulative total number of injected nitrogen or oxygen molecules. Thus, in this embodiment, when calculating the total amount of oxygen molecules in the device, we use the ideal gas equation (PV = nRT), combined with the ppm reading of the oxygen analyzer, as well as the overall volume, total temperature, total pressure, etc. of the device to estimate the number of nitrogen and oxygen molecules in the current device. In addition, we can also use this formula to calculate the number of nitrogen and oxygen molecules in the device under any target state (specific temperature, pressure, ppm). The difference between the number or mass of oxygen molecules in the target state and the current state is the controlled variable difference of the controller, and we use this for feedforward control.

[0064] In this embodiment, the feedback control pipeline 192 includes large, medium, and small oxygen supplement pipelines arranged in parallel, and each branch is configured with flow controllers of different accuracy levels. The large oxygen supplement pipeline includes a second pneumatic control valve 1921, a second vortex flowmeter 1922, and a second pneumatic valve 1923 connected in sequence; the medium oxygen supplement pipeline includes a third pneumatic valve 1924 and a large mass flow control valve 1925 connected in sequence; the small oxygen supplement pipeline includes a fourth pneumatic valve 1926 and a small mass flow control valve 1927 connected in sequence. The real-time data of the second pneumatic valve 1923 and the large / small mass flow control valve 1927 are fed back to the PID control end, and the output ends of the large, medium, and small oxygen supplement pipelines converge to another input end of the oxygen injection rake.

[0065] Specifically, the parameter configuration of the feedback control pipeline 192 is as follows:

[0066] For the large oxygen supplement pipeline, the nominal diameter is DN50, the flow range is 200 - 500 Nm 3 / h, and the control accuracy is ±2%;

[0067] For the medium oxygen supplement pipeline, the nominal diameter is DN25, the flow range is 50 - 200 Nm 3 / h, and the control accuracy is ±0.5%;

[0068] For the small oxygen supplement pipeline, the nominal diameter is DN10, the flow range is 5 - 50 Nm 3 / h, and the control accuracy is ±0.1%.

[0069] During use, the PID control terminal dynamically allocates control and selects the activated branch combination according to the real-time oxygen content deviation value. For example: (a) When the deviation ≥ 50 ppm, activate the main pipeline with large flow rate and the large compensation branch; (b) When 10 ppm ≤ deviation < 50 ppm, activate the medium compensation branch; (c) When the deviation < 10 ppm, activate the small compensation branch.

[0070] The PID control terminal establishes a mapping table of working condition parameters and stores the ppm-mole amount conversion coefficient K(T, P) at different temperatures T and pressures P; real-time compensation amount calculation: Q_comp = Δppm × K(T, P) / C_reference; intelligently allocate according to the Q_comp value to the corresponding branch combination to satisfy Q_comp = Q_main × α + Q_large × β + Q_medium × γ + Q_small × δ, where α, β, γ, δ ∈ {0, 1} are the branch activation status quantities.

[0071] Among them, the conversion coefficient K(T, P) is dynamically updated through an online learning algorithm. The specific operation method is: collect the actual compensation effect Δppm_measured every cycle; calculate the correction factor η = (Δppm_theory - Δppm_measured) / Δppm_theory; update K(T, P)_new = K(T, P)_old × (1 + η × 0.2), with the constraint η ≤ 0.5.

[0072] The liquid nitrogen / oxygen injection process belongs to a unidirectional / single-variable control process. During the execution process, the actuator to be controlled can only inject air unidirectionally towards a specific device to increase the oxygen content ppm value, and cannot control the injection of liquid nitrogen to reduce the oxygen content ppm value. Therefore, the method of adopting active bidirectional control and combining oscillation adjustment in the project to make the oxygen content ppm value of the control target converge and reach the expected value is not applicable to this project. During the control process, this embodiment focuses on avoiding overshoot phenomena and minimizing or eliminating overshoot as much as possible.

[0073] This embodiment calculates an oxygen injection amount based on the ideal gas equation. In the initial stage, inject at 85% - 95% of the injection amount calculated according to this theory to improve the control response speed and ensure that there are no overshoot and overshoot phenomena. After the system working condition is basically stable, and there is still a gap with the target oxygen content ppm value at this time, then take the average reading of the real-time oxygen content acquisition equipment such as an oxygen analyzer, and use the feedback control pipeline 192 for PID closed-loop control to achieve the precise replenishment of the final oxygen content.

[0074] Secondly, we adopt the PID control strategy of feedback control line 192 to avoid overshoot and overshoot problems. For example, in terms of PID parameter setting, we can use the PID parameter group under critical damping or overdamping state to ensure that there is no overshoot and no overshoot. PID parameter tuning is a key link in the later debugging. Under the premise of ensuring no overshoot, we optimize the PID parameters. For example, we can combine algorithms such as deep learning to improve the response speed and control accuracy of the system, so as to achieve the ppm target value as quickly and accurately as possible.

[0075] In order to ensure the safety of the injected gas source, in this embodiment, a gas source pretreatment component 193 is connected before the oxygen injection component 190. The gas source pretreatment component 193 includes:

[0076] An oxygen injection pipeline, the oxygen injection pipeline includes an air access port 1931 and / or an oxygen access port 1932;

[0077] A drying and filtering pipeline 1933 is connected to the output end of each oxygen injection pipeline;

[0078] A dew point detection pipeline is connected to a branch pipeline at the output end of the drying and filtering pipeline 1933. The dew point detection pipeline includes a branch pipe pneumatic valve 1934, a preprocessor 1935 and a dew point meter 1936 connected in sequence to ensure that the gas dew point reaches below -70°C;

[0079] The automatic pressure / flow regulating pipeline 1937 is connected to the main pipeline of the drying and filtering pipeline 1933. Each pipeline of the automatic pressure / flow regulating pipeline 1937 is provided with an automatic pressure and flow regulating valve. The confluence pipeline of the automatic pressure / flow regulating pipeline 1937 is also equipped with a safety valve.

[0080] In this embodiment, the gas source of the oxygen injection assembly 190 is mainly dry air provided by the air drying system of the closed-loop fluid equipment, and in special circumstances it comes from the spare dry oxygen provided by Party B. Therefore, the oxygen injection pipeline is designed with two air inlets, so that the input gas source can be oxygen or dry air, or a mixture of dry air and oxygen.

[0081] Both gas source interfaces are connected to drying and filtering pipelines 1933, which have a built-in 0.1μm sintered metal filter to intercept particulate matter (in compliance with NAS1638Class 5), protect the sensor mirror from contamination, remove moisture from the gas source to prevent condensation, and ensure the cleanliness of the gas source. The dried and filtered gas source pipeline is connected to the dew point detection pipeline for dew point detection to ensure that the input gas source dew point meets the technical requirement of less than -70 degrees, and then the corresponding automatic pressure and flow regulating valves are used to regulate the pressure and then merge into the gas source main through the safety valve. After that, the gas source is divided into two routes, one with a large flow rate and the other with a small flow rate.

[0082] The best installation method for the dew point sensor is to isolate the sensor from the oxygen pipeline. Install the sensor in the "sampling unit", and then connect this unit to the oxygen pipeline in a T-shaped manner. A small amount of oxygen will be discharged and flow through the sensor. The sampling unit should be made of stainless steel and connected to the T-joint with a conduit (1 / 4" or 6mm). Install an isolation valve 001 between the sampling unit and the air pipeline to facilitate the easy installation and removal of the sensor.

[0083] In this embodiment, the sampling unit is machined from 316L stainless steel and is T-shaped connected to the main oxygen pipeline through a 1 / 4" (6mm) Swagelok compression tube to form a bypass sampling system. The internal flow channel of the unit is optimized by CFD, and the flow rate is controlled at 0.3 - 0.8 m / s (meeting the ISO 8573-1 standard).

[0084] There are at least two sets of oxygen content detection components 180. One set is assembled at the rear end of the stabilization section 130, and the other set is assembled at the rear end of the test chamber section 140. The oxygen content detection adopts a redundant detection architecture with a dual-channel detection component layout.

[0085] Among them, the specific design of the detection point in the stabilization section 130 is: install the first set of detection components at a distance of 1.5D (D is the pipe diameter) from the outlet of the stabilization section 130, and at the same time configure a laser TDLAS analyzer (measurement range 0 - 25% O, resolution 0.01%) and a paramagnetic oxygen analyzer to obtain the reference oxygen concentration after pretreatment.

[0086] Detection point in the test chamber section 140: Deploy the second set of detection components at a position 3D downstream of the test chamber section 140, integrating an electrochemical sensor and a paramagnetic oxygen analyzer (response time ≤ 0.5 s) to achieve double verification of the oxygen dynamic detection process.

[0087] Use the Kalman filtering technology to fuse and process the oxygen detection data at the two detection points, and establish the state equation:

[0088]

[0089] Among them, A is the system state transition matrix, H is the observation matrix, and the reduction of the implementation noise variance is more than 60% (σ ≤ 0.05% O).

[0090] Embed the NIST REFPROP database to compensate in real time for the influence of temperature (105K - 334K) and pressure change (0.1 - 1 MPa) on the oxygen partial pressure measurement. The compensation formula:

[0091]

[0092] Make the measurement error ≤ ±0.1% O under all working conditions.

[0093] A dual-mode regulating device is configured. A precision needle valve (regulation accuracy: ±0.01 MPa) is installed downstream for measuring the pressure dew point (maintaining the process pressure within ±2%), and a mass flow controller (MFC) is installed upstream for measuring the atmospheric dew point (flow stability ≤ ±1% FS). The advantages compared with the traditional single dew point detection method are as follows:

[0094] The traditional dew point response time is 60 - 120 s, while the dew point response time of this design solution is ≤15 s, with a promotion range of 75% - 87%;

[0095] The traditional oxygen content measurement has a delay of 2 - 5 s. The oxygen content measurement of this design solution adopts data fusion measurement, with a delay ≤0.8 s, and a promotion range of 60% - 84%;

[0096] The traditional measurement calibration period has changed from quarterly replacement to annual replacement, with a promotion range of 300%.

[0097] The automatic pressure / flow regulating pipeline 1937 adopts a pressure drop compensation algorithm: in the pressure dew point mode, the flow velocity-pressure drop relationship (ΔP = 0.5ρv 2 ) is calculated in real time through the Bernoulli equation to dynamically compensate for the dew point error caused by the pressure drop (compensation accuracy ±0.2 °C); at the same time, an ultimate flow velocity protection is adopted. The set automatic pressure and flow regulating valve has a mechanical flow limiting orifice plate (the aperture Φ0.5 - 1.0 mm is adjustable) to ensure that the flow velocity ≤3 m / s (when the speed exceeds the limit, an audible and visual alarm is triggered and the isolation valve is closed).

[0098] All system conduits adopt EP-grade electropolished stainless steel pipes (Ra ≤ 0.4 μm), equipped with VCR metal sealing joints, and the water vapor permeability ≤ 5×10 -9 g / (m 2 ·s). Anti-adsorption treatment is carried out inside, and the inner wall of the flow channel is coated with a nano-aluminum oxide coating (thickness 50 - 80 nm), reducing the water molecule adsorption rate to 1 / 5 of that of traditional materials.

[0099] The oxygen content detection component 180 in this embodiment has significant technical advantages in high-precision gas control fields such as aerospace and semiconductor manufacturing through an innovative isolation sampling structure, a multi-physical field coupling compensation algorithm, and a redundant detection architecture, and can meet the stringent standard requirements such as ISO 14624 and ECSS-Q-ST-70-01C.

[0100] Second Embodiment

[0101] For the continuous cooling closed-loop fluid system disclosed in the first embodiment, in order to ensure uniform injection of the oxygen-containing gas stream and cover the entire cross-sectional width of the flow channel, this embodiment also develops a new oxygen injection rake 194, which includes:

[0102] The front section of the oxygen injection rake. The front section of the oxygen injection rake consists of a cylinder 1941, a transition body 1942, and an oblate body 1943 connected in sequence. The oblate body 1943 has an oblate structure with a "playground-shaped" cross-section. It smoothly transitions from the cylinder 1941 to the oblate body 1943 through the transition body 1942. The cross-sectional areas of the internal air flow pipes of the cylinder 1941, the transition body 1942, and the oblate body 1943 are the same. At the other end of the cylinder 1941, a gas supply pipe docking flange 1944 is assembled. At the other end of the oblate body, a closed-loop fluid system docking flange 1947 is assembled. The surface roughness Ra of the inner wall of the internal air flow pipe is ≤0.8μm;

[0103] The rear section 1945 of the oxygen injection rake. The rear section 1945 of the oxygen injection rake is an oblate plate with a "playground-shaped" cross-section. Exhaust holes 1946 are arranged at equal intervals on the midlines (in the length direction) of the two arc-shaped sides of the rear section 1945 of the oxygen injection rake. The cross-section of the internal air flow pipe of the rear section 1945 of the oxygen injection rake is the same as that of the internal air flow pipe of the oblate body 1943.

[0104] The oxygen injection rake 194 can be a structure symmetrically designed based on the rear section 1945 of the oxygen injection rake, which is beautiful and convenient for connecting pipe bodies, that is, the two ends of the rear section 1945 of the oxygen injection rake are connected to the same structure as the front section of the oxygen injection rake.

[0105] In this embodiment, the rear section 1945 of the oxygen injection rake has a long coverage range, about 2.4 meters - 4 meters. It can have a fixed length, or it can be designed as a structure with an adjustable length or a segmented assembly structure by using a telescopic sleeve structure.

[0106] If the rear section 1945 of the oxygen injection rake is designed as a telescopic sleeve structure, it can be achieved through the following structure: an inner and outer double-layer pipe body nested, with guide fins provided on the inner wall of the inner layer pipe; an electric push rod adjustment mechanism, which feeds back the real-time length value through a displacement sensor; and a low-temperature-resistant sealing material layer is filled in the gap between the pipe bodies.

[0107] The gas supply pipe docking flange 1944 serves as an intake manifold cavity and is respectively connected to the output ends of the feedforward control pipeline 191 and the feedback control pipeline 192. A closed-loop fluid system docking flange 1947 is assembled at the other end of the oblate body 1943, which is used to detachably install the oxygen injection rake 194 onto the closed-loop fluid equipment. An external hanging installation structure is adopted, without changing the original wall surface and insulation layer of the closed-loop fluid system cavity.

[0108] The specific structure of the specific external hanging installation structure is preliminarily designed as follows: including, from the inside to the outside in sequence: an arc-shaped base matching the wall curvature of the closed-loop fluid system; a high-temperature ceramic gasket isolation layer; a prestressed bolt group, and the applied pressing force does not exceed 40% of the yield strength of the closed-loop fluid system shell material.

[0109] The third embodiment

[0110] This embodiment provides a precise control method for a dual-mode oxygen-controlled continuous cooling closed-loop fluid system, including the continuous cooling closed-loop fluid system disclosed in the first embodiment or the second embodiment. The precise control method includes the following steps:

[0111] The compressor section, liquid nitrogen injection section, and heat exchange section are started normally. When the Mach number and nitrogen pressure value in the corresponding section reach the set value and the total temperature value reaches a constant value, the oxygen precise control system is started;

[0112] Read the liquid nitrogen injection data to obtain the liquid nitrogen injection flow rate parameter and injection time parameter of the liquid nitrogen injection section in real time;

[0113] Monitor the oxygen content in real time. Through the oxygen content detection component 180 configured in the closed-loop fluid equipment system, it is used to collect the oxygen content reference value in the set time interval before injection. The set time interval of the oxygen content reference value is a sliding window of 2-10 seconds before liquid nitrogen injection;

[0114] When the liquid nitrogen injection flow rate is lower than the preset threshold, calculate the air compensation flow rate proportionally according to the real-time liquid nitrogen injection flow rate, and control the oxygen injection component 190 to start injecting synchronously;

[0115] When the liquid nitrogen injection flow rate exceeds the preset threshold, record the total liquid nitrogen injection volume. The oxygen injection component 190 injects the oxygen-containing gas stream at the maximum supply flow rate until the cumulative injection volume reaches the compensation volume corresponding to the total liquid nitrogen injection volume; the preset threshold is 80%-95% of the maximum flow rate of the oxygen injection component 190.

[0116] The above specific implementation manners further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above is only the specific implementation manner of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dual-mode oxygen-controlled continuous cooling closed-loop fluid system, characterized in that: The continuous cooling closed-loop fluid system comprises a compressor section, a liquid nitrogen injection section, a heat exchange section, a stabilization section, a test cabin section, a pressure diffuser unit, an oxygen injection section and a steering unit which are sequentially connected to form a "U"-shaped cycle. An oxygen content detection component is installed between the stabilization section and the test cabin section. The oxygen injection section is equipped with an oxygen injection component. The oxygen injection component comprises: A feedforward control pipeline, which serves as a large-flow gas path during oxygen injection and receives a feedforward control instruction from a PLC. The feedforward control instruction automatically accompanies liquid nitrogen injection based on the oxygen molecule demand calculated by the ideal gas equation in combination with a correction equation or a simulation mode value according to liquid nitrogen injection data; A feedback control pipeline, which serves as a small flow gas path during the oxygen injection process, receives a PID feedback control instruction, and the feedback control instruction is an oxygen supplement molecule demand calculated by the real-time oxygen content data obtained by the oxygen content measurement component and the liquid nitrogen injection data.

2. The dual-mode oxygen-controlled continuous temperature-lowering closed-loop fluid system according to claim 1, characterized in that: The feedforward control pipeline includes a first pressure and temperature sensor, a first pneumatic regulating valve, a first vortex flowmeter, a first pneumatic valve, a second pressure and temperature sensor, and one of the input ends of the oxygen injection rake, which are connected in sequence. Real-time data of the first pneumatic valve is fed back to the PID control end.

3. The dual-mode oxygen-controlled continuous temperature-lowering closed-loop fluid system according to claim 2 is characterized in that: The feedback control pipeline includes three large, medium and small oxygen supply pipelines arranged in parallel. The large oxygen supply pipeline includes a second pneumatic regulating valve, a second vortex flowmeter and a second pneumatic valve connected in sequence; the medium oxygen supply pipeline includes a third pneumatic valve and a large mass flow control valve connected in sequence; the small oxygen supply pipeline includes a fourth pneumatic valve and a small mass flow control valve connected in sequence, the real-time data of the second pneumatic valve and the large / small mass flow control valves are fed back to the PID control end, and the output ends of the large, medium and small oxygen supply pipelines are gathered to the other input end of the oxygen injection rake.

4. The dual-mode oxygen-controlled continuous temperature-lowering closed-loop fluid system according to claim 3 is characterized in that: The oxygen injection rake comprises: The oxygen injection rake front section is composed of a cylinder, a transition body and an oblate body connected in sequence. The oblate body is an oblate body structure with a "playground-shaped" cross section. The transition body smoothly transitions from the cylinder to the oblate body. The cross-sectional areas of the internal air flow ducts of the cylinder, the transition body and the oblate body are the same. The other end of the cylinder is equipped with a gas supply pipe docking flange, and the other end of the oblate body is equipped with a closed-loop fluid system docking flange; The rear section of the oxygen injection rake is a flat circular plate with a "playground-shaped" cross-section. Exhaust holes distributed at equal intervals are arranged on the midlines of the two arc-shaped sides of the rear section of the oxygen injection rake. The cross-section of the internal air flow duct of the rear section of the oxygen injection rake is the same as the cross-section of the internal air flow duct of the flat circular body.

5. The dual-mode oxygen-controlled continuous temperature-lowering closed-loop fluid system according to claim 3 is characterized in that: The oxygen injection assembly is also connected to a gas source pretreatment assembly, and the gas source pretreatment assembly includes: an oxygen injection pipeline, the oxygen injection pipeline comprising an air access port and / or an oxygen access port; A drying and filtering pipeline connected to the output end of each of the oxygen injection pipelines; A dew point detection pipeline is connected to a branch pipeline at the output end of the drying and filtering pipeline, wherein the dew point detection pipeline includes a branch pipe pneumatic valve, a preprocessor and a dew point meter connected in sequence to ensure that the gas dew point reaches below -70°C; The automatic pressure / flow regulating pipeline is connected to the main pipeline of the drying and filtering pipeline. Each pipeline of the automatic pressure / flow regulating pipeline is provided with an automatic pressure and flow regulating valve. The confluence pipeline of the automatic pressure / flow regulating pipeline is also equipped with a safety valve.

6. The dual-mode oxygen-controlled continuous temperature-lowering closed-loop fluid system according to claim 3, characterized in that: The oxygen content detection components are provided with at least two groups, one of which is assembled at the rear end of the stabilizing section, and the other is assembled at the rear end of the testing compartment section.

7. The dual-mode oxygen-controlled continuous temperature-lowering closed-loop fluid system according to claim 3, characterized in that: The parameter configuration of the feedback control pipeline is: Large oxygen supply pipeline, diameter DN50, flow range 200-500Nm 3 / h, control accuracy ±2%; Medium oxygen supply pipeline, diameter DN25, flow range 50-200Nm 3 / h, control accuracy ±0.5%; Small oxygen supply pipeline, diameter DN10, flow range 5-50Nm 3 / h, control accuracy ±0.1%.

8. A precise control method for a dual-mode oxygen-controlled continuous cooling closed-loop fluid system, comprising the continuous cooling closed-loop fluid system according to any one of claims 1 to 7, characterized in that: The precise control method comprises the following steps: Read liquid nitrogen injection data to obtain the liquid nitrogen injection flow rate parameters and injection time parameters of the liquid nitrogen injection section in real time; Real-time monitoring of oxygen content, through the oxygen content detection component configured in the closed-loop fluid equipment system, is used to collect the oxygen content baseline value of the set time interval before injection; When the liquid nitrogen injection flow rate is lower than the preset threshold, the air compensation flow rate is calculated proportionally according to the real-time liquid nitrogen injection flow rate, and the oxygen injection component is controlled to start injection synchronously; When the liquid nitrogen injection flow rate exceeds the preset threshold, the total liquid nitrogen injection amount is recorded, and the oxygen injection component injects the oxygen-containing gas flow at the maximum gas supply flow rate until the cumulative injection amount reaches the compensation amount corresponding to the total liquid nitrogen injection amount.

9. The precise control method of the dual-mode oxygen-controlled continuous temperature-lowering closed-loop fluid system according to claim 8, characterized in that: The setting time interval of the oxygen content baseline value is a sliding window of 2-10 seconds before liquid nitrogen injection.

10. The precise control method of the dual-mode oxygen-controlled continuous temperature-lowering closed-loop fluid system according to claim 8, characterized in that: The preset threshold is 80%-95% of the maximum flow rate of the oxygen injection component.

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