A dual-mode oxygen-controlled continuous cooling closed-loop fluid system and precise control method

Abstract

The application provides a bimodal oxygen control continuous cooling closed-loop fluid system and a precise control method, which ensures precise control of oxygen content in a closed-loop fluid device. 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, an expansion unit, an oxygen injection section and a steering unit connected in sequence and forming a "back" shape circulation. An oxygen content detection assembly is arranged between the stabilization section and the test cabin section. The oxygen injection section is provided with an oxygen injection assembly. The oxygen injection assembly comprises a feedforward control pipeline and a feedback control pipeline. The feedforward control pipeline receives a feedforward control instruction of a PLC and automatically accompanies liquid nitrogen injection according to oxygen molecule demand calculated by an ideal gas equation combined with a correction equation or a simulation mode value. The feedback control pipeline receives a PID feedback control instruction. The feedback control instruction is calculated by real-time oxygen content data obtained by an oxygen content measurement assembly and oxygen molecule demand calculated by liquid nitrogen injection data.

Description

Technical Field

[0001] This invention relates to the field of closed-loop fluid system testing, and more specifically, to a dual-mode oxygen-controlled continuous cooling closed-loop fluid system and a precise control method. Background Technology

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

[0003] Normally, air is the primary operating medium for continuous closed-loop fluid systems. However, in some special experiments with stringent environmental requirements, nitrogen, carbon dioxide, etc., may also be used as the operating medium. Currently, there is no equipment that meets the requirement of using dry nitrogen gas with a temperature range of 105K to 334K as the operating medium, and the oxygen content of the incoming flow to the equipment being in the range of 1000–3000 ppm, while simultaneously achieving precise oxygen content control (≤±15 ppm). This invention addresses this requirement by developing a continuous closed-loop fluid system, designing an oxygen content stabilization control system based on liquid nitrogen injection and its precise control method, thereby achieving the design objectives. Summary of the Invention

[0004] The purpose of this invention is to provide a dual-mode oxygen-controlled 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-modal oxygen-controlled 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, which are sequentially connected and form a U-shaped loop. An oxygen content detection component is installed between the stabilization section and the test chamber section, and an oxygen injection component is installed in the oxygen injection section. The oxygen injection component includes:

[0007] The feedforward control pipeline, as a high-flow gas path in the oxygen injection process, receives feedforward control commands from the PLC. The feedforward control commands calculate the oxygen molecule demand based on the liquid nitrogen injection data through the ideal gas equation combined with the modified equation or simulation mode value, and automatically accompany the liquid nitrogen injection.

[0008] The feedback control line, which serves as a low-flow gas path during the oxygen injection process, receives PID feedback control commands. These commands are calculated based on the real-time oxygen content data obtained from the oxygen content measurement component and the liquid nitrogen injection data, determining the required amount of supplemental oxygen molecules.

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

[0010] In a preferred embodiment of the present invention, the above-mentioned feedback control pipeline includes three parallel large, medium and small oxygen supply pipelines. The large oxygen supply pipeline includes a second pneumatic regulating valve, a second vortex flow meter 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 valve are fed back to the PID control terminal, and the output terminals of the large, medium and small oxygen supply pipelines converge to another input terminal of the oxygen injection rake.

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

[0012] The oxygen injection rake front section consists of a cylinder, a transition body, and a flattened sphere connected in sequence. The flattened sphere has a "playground-shaped" cross-section and smoothly transitions from the cylinder to the flattened sphere through the transition body. The cross-sectional area of ​​the internal airflow pipes of the cylinder, transition body, and flattened sphere is the same. The other end of the cylinder is equipped with an air supply pipe docking flange, and the other end of the flattened sphere is equipped with a closed-loop fluid system docking flange.

[0013] The oxygen injection rake section is a flat circular plate with a "playground-shaped" cross-section. There are equally spaced exhaust holes on the center line of the two arc-shaped sides of the oxygen injection rake section. The cross-section of the internal airflow pipe of the oxygen injection rake section is the same as the cross-section of the internal airflow pipe of the flat circular plate.

[0014] In a preferred embodiment of the present invention, a gas source pretreatment component is further connected before the oxygen injection component, the gas source pretreatment component comprising:

[0015] Oxygen injection line, the oxygen injection line including an air inlet port, and / or an oxygen inlet port;

[0016] Drying and filtering tubing connects to the output end of each oxygen injection tubing;

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

[0018] The automatic pressure / flow regulating pipeline is the main pipeline connecting the drying and filtering pipeline. Each pipeline in the automatic pressure / flow regulating pipeline is equipped with an automatic pressure / flow regulating valve, and a safety valve is also installed on the manifold of the automatic pressure / flow regulating pipeline.

[0019] In a preferred embodiment of the present invention, the above-mentioned oxygen content detection component is provided in at least two sets, one set being assembled at the rear end of the stabilization section and the other set being assembled at the rear end of the test chamber section.

[0020] In a preferred embodiment of the present invention, the parameters of the feedback control circuit are configured as follows:

[0021] Large oxygen supply pipeline, DN50 diameter, flow range 200-500 Nm 3 / h, control accuracy ±2%;

[0022] Central oxygen supply pipeline, DN25 diameter, flow range 50-200 Nm 3 / h, control accuracy ±0.5%;

[0023] Small oxygen supply pipeline, DN10 diameter, flow range 5-50 Nm 3 / h, control accuracy ±0.1%.

[0024] A precise control method for a dual-modal oxygen-controlled continuous cooling closed-loop fluid system, comprising any of the aforementioned continuous cooling closed-loop fluid systems, the precise control method comprising the following steps:

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

[0026] Real-time monitoring of oxygen content is achieved by using an oxygen content detection component configured in a closed-loop fluid equipment system to collect baseline values ​​of oxygen content for a set time interval before injection.

[0027] When the liquid nitrogen injection flow rate is lower than the preset threshold, the air compensation flow rate is calculated proportionally based on the real-time liquid nitrogen injection flow rate, and the oxygen injection component is controlled to start injection synchronously.

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

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

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

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

[0032] 1. Dual-mode precision control capability: Through the synergistic effect of the feedforward control pipeline (high flow rate) and the feedback control pipeline (low flow rate), it not only achieves rapid oxygen compensation response (feedforward control response time ≤ 0.5 seconds) accompanying liquid nitrogen injection, but also ensures oxygen content control accuracy (±5ppm) through PID closed-loop regulation, thus solving the technical contradiction that traditional single control mode cannot balance speed and accuracy.

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

[0034] 3. Enhanced anti-interference capability: The feedforward-feedback composite control algorithm incorporates a liquid nitrogen injection flow prediction model (ARIMA time series analysis), 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), the system can maintain an oxygen content fluctuation range of ≤±10ppm even when the liquid nitrogen injection flow rate changes abruptly (≥30% of the rated value / s).

[0035] 4. Enhanced adaptability to multiple operating conditions: By dynamically switching between the simulation mode value database (covering temperatures from 105K to 334K) and the real-time correction equation, the system can maintain control accuracy under extreme test conditions and adapt to the wide-range environmental requirements of aerospace material testing (cross-temperature zone test switching time ≤ 5min).

[0036] 5. Innovative Control Delay Compensation: A transmission delay calculation module (based on real-time measurement of pipeline volume and flow velocity) is introduced into the pipeline design to perform time phase compensation on the feedforward control command (compensation accuracy ±0.1s), eliminating the overshoot phenomenon caused by the physical delay of gas transmission and keeping the system step response overshoot within 5%. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the continuous cooling closed-loop fluid system structure according to an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the piping connection of the oxygen precision control system according to an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the oxygen injection rake structure according to an embodiment of the present invention;

[0041] Figure 4 This is a flowchart illustrating the use of the continuous cooling closed-loop fluid system according to an embodiment 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 assembly 180; Oxygen injection assembly 190; Feedforward control line 191; First pressure and temperature sensor 1911; First pneumatic regulating valve 1912; First vortex flow meter 1913; First pneumatic valve 1914; Second pressure and temperature sensor 1915; Feedback control line 192; Second pneumatic regulating valve 1921; Second vortex flow meter 1922; Second pneumatic valve 1923; Third gas... Pneumatic valve 1924; Large mass flow control valve 1925; Fourth pneumatic valve 1926; Small mass flow control valve 1927; Air inlet port 1931; Oxygen inlet port 1932; Dryer filter line 1933; Branch pneumatic valve 1934; Pre-processor 1935; Dew point meter 1936; Automatic pressure / flow regulation line 1937; Cylindrical body 1941; Transition body 1942; Flattened cylindrical body 1943; Air supply pipe connecting flange 1944; Oxygen injection rake rear section 1945; Exhaust port 1946; Closed-loop fluid system connecting flange 1947; Isolation valve 001. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0044] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0045] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

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

[0047] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

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

[0049] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0050] First Embodiment

[0051] In this embodiment, the continuous cooling closed-loop fluid system uses low-temperature dry nitrogen gas with a temperature range of 105K to 334K as the operating medium. The gas source outlet pressure is 1MPa, and its maximum usable flow rate can reach 1400Nm³. 3 / h; liquid nitrogen injection flow rate ranges from 0 to 315 kg / s; the dew point of the injected dry gas is below or equal to -70℃. To meet the experimental requirement of the incoming oxygen content of 1000-3000 ppm and to achieve precise control of the incoming oxygen content (error range ≤ ±15 ppm), a precise oxygen control system suitable for this equipment was specially developed.

[0052] Please see Figure 1 This embodiment provides a dual-modal oxygen-controlled continuous cooling closed-loop fluid system. The 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 connected in sequence to form a "U"-shaped loop. An oxygen content detection component 180 is installed between the stabilization section 130 and the test chamber section 140, and an oxygen injection component 190 is installed in the oxygen injection section 160.

[0053] In this embodiment, the oxygen injection system injects dry oxygen-containing gas between the diffuser unit 150 and the steering unit 170. Simultaneously, the oxygen content measurement point is located at the test chamber section 140 and its upstream position. Therefore, the injected oxygen-containing gas must travel through the entire equipment loop to reach the oxygen content measurement point. Given this, the oxygen content control system needs strong anti-interference capabilities (i.e., to handle mutual interference between the dry oxygen injection rate, liquid nitrogen injection rate, and gaseous nitrogen discharge rate) and good resistance to large hysteresis (due to the considerable distance between the oxygen content measurement point and the oxygen injection point). To address these issues, this embodiment designs a novel oxygen injection assembly 190, which includes:

[0054] Feedforward control line 191 serves as a high-flow gas path in the oxygen injection process. It receives feedforward control commands from the PLC. The feedforward control commands calculate the oxygen molecule demand based on the liquid nitrogen injection data using the ideal gas equation combined with the modified equation or simulation mode value, and automatically accompany the liquid nitrogen injection.

[0055] Feedback control line 192 serves as a low-flow gas path during the oxygen injection process. It receives PID feedback control commands, which are calculated based on the real-time oxygen content data obtained from the oxygen content measurement component and the liquid nitrogen injection data to determine the required amount of supplemental oxygen molecules.

[0056] The feedforward control line 191 includes a first pressure and temperature sensor 1911, a first pneumatic regulating valve 1912, a first vortex flow meter 1913, a first pneumatic valve 1914, a second pressure and temperature sensor 1915, and one of the input terminals of the oxygen injection rake, which are connected in sequence. The real-time data of the first pneumatic valve 1914 is fed back to the PID control terminal. The first pneumatic regulating valve 1912 is a pilot-operated electromagnetic quick-opening valve with an opening response time ≤100ms.

[0057] Air or pure oxygen is automatically regulated within the pipe via a pneumatic regulating valve to provide a constant pressure difference that meets the operating conditions. Currently, the designed pressure difference between the two ends of the pipeline is 0.4 MPa. Pressure and temperature sensors are added downstream of the pressure regulating valve and upstream of the closed-loop fluid equipment to monitor the operating pressure and temperature. Automatic pressure compensation is performed using the pressure and temperature sensors integrated into the pneumatic pressure regulating valve. The main objective of automatic pressure regulation is to control and maintain a stable pressure difference in the gas path. Since the test pressure of the main equipment is variable, the pressure difference between the two ends of the gas path must also be relatively stable to obtain a stable flow rate.

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

[0059] ① During the trial operation of the closed-loop fluid equipment, liquid nitrogen may be automatically replenished to the system at any time. However, the replenishment of liquid nitrogen will cause changes in the oxygen content (ppm). When stabilizing the oxygen content (ppm), this random disturbance must be considered. Therefore, this embodiment eliminates this random disturbance by designing a high-flow-rate gas path that automatically accompanies the liquid nitrogen injection.

[0060] ② By reading relevant data on liquid nitrogen injection, such as liquid nitrogen injection flow rate and injection duration, the corresponding air to be injected is controlled. Specifically, by precisely adjusting the air flow rate and injection duration to match the flow rate, duration, and even total injection volume of liquid nitrogen, the system's oxygen content (ppm) is stabilized.

[0061] ③ In considering the automatic accompanying injection function, for 1400Nm 3 If the gas supply of / h may not be compatible with the large-scale injection of liquid nitrogen, the automatic accompanying injection will carry out the injection operation at the maximum air flow rate until the total amount of oxygen injected 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 basically synchronize with the liquid nitrogen injection without significant delay.

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

[0064] In this embodiment, the feedback control pipeline 192 includes three parallel oxygen supply pipelines: a large, a medium, and a small oxygen supply pipeline. Each branch is equipped with a flow controller of different accuracy levels. The large oxygen supply pipeline includes a second pneumatic regulating valve 1921, a second vortex flow meter 1922, and a second pneumatic valve 1923 connected in sequence. The medium oxygen supply pipeline includes a third pneumatic valve 1924 and a large mass flow control valve 1925 connected in sequence. The small oxygen supply pipeline includes a fourth pneumatic valve 1926 and a small mass flow control valve 1927 connected in sequence. Real-time data from the second pneumatic valve 1923 and the large / small mass flow control valves 1927 is fed back to the PID control terminal. The outputs of the large, medium, and small oxygen supply pipelines converge at another input terminal of the oxygen injection rake.

[0065] Specifically, the parameters of the feedback control circuit 192 are configured as follows:

[0066] Large oxygen supply pipeline, DN50 diameter, flow range 200-500 Nm 3 / h, control accuracy ±2%;

[0067] Central oxygen supply pipeline, DN25 diameter, flow range 50-200 Nm 3 / h, control accuracy ±0.5%;

[0068] Small oxygen supply pipeline, DN10 diameter, flow range 5-50 Nm 3 / h, control accuracy ±0.1%.

[0069] When in use, the PID control terminal dynamically allocates control and selects the combination of active branches according to the real-time oxygen content deviation value. For example: (a) when the deviation is ≥50ppm, the high flow main branch and the large compensation branch are activated; (b) when 10ppm≤deviation<50ppm, the medium compensation branch is activated; (c) when the deviation is <10ppm, the small compensation branch is activated.

[0070] The PID control terminal establishes a working condition parameter mapping table to store the ppm-molar conversion coefficient K(T,P) under different temperatures T and pressures P; real-time compensation is calculated as: Q_comp=Δppm×K(T,P) / C_reference; based on the Q_comp value, it is intelligently allocated to the corresponding branch combination, satisfying 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 state quantities.

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

[0072] Both liquid nitrogen and oxygen injection processes are unidirectional / single-variable control processes. During execution, the controlled actuator can only inject air unidirectionally towards a specific device to increase the oxygen content (ppm), but cannot control the injection of liquid nitrogen to decrease the oxygen content (ppm). Therefore, the method typically used in projects, which combines active bidirectional control with oscillation adjustment to converge the controlled oxygen content (ppm) to the expected value, is not suitable for this project. In this embodiment, the control process focuses on avoiding overshoot and minimizing or eliminating overshoot as much as possible.

[0073] This embodiment calculates an oxygen injection volume based on the ideal gas equation. In the initial stage, 85%–95% of the theoretically calculated injection volume is injected to improve control response speed and ensure no overshoot or overshoot occurs. After the system operation stabilizes, there is still a difference between the actual oxygen content (ppm) and the target value. The average reading from real-time oxygen content acquisition devices such as an oxygen analyzer is then used, and PID closed-loop control is implemented using feedback control line 192 to achieve precise final oxygen replenishment.

[0074] Secondly, we adopt the PID control strategy for the feedback control pipeline 192, which can avoid overshoot and overregulation problems. For example, in terms of PID parameter setting, the PID parameter groups in the critically damped or overdamped state can be used to ensure no overshoot and no overregulation. The tuning of PID parameters is a key link in the later-stage debugging. On the premise of ensuring no overshoot, we optimize the PID parameters. For example, algorithms such as deep learning can be combined to improve the response speed and control accuracy of the system, so as to accurately reach the ppm target value as soon as possible.

[0075] For reasons such as ensuring the safety of the injected gas source, in this embodiment, a gas source pretreatment component 193 is further connected before the oxygen injection component 190. The gas source pretreatment component 193 includes:

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

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

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

[0079] An automatic pressure / flow regulation pipeline 1937, which is connected to the main pipeline of the drying and filtering pipeline 1933. An automatic pressure and flow regulating valve is provided on each pipeline of the automatic pressure / flow regulation pipeline 1937, and a safety valve is simultaneously installed on the confluence pipeline of the automatic pressure / flow regulation pipeline 1937.

[0080] In this embodiment, the gas source of the oxygen injection component 190 is mainly the dry air provided by the air drying system supporting the closed-loop fluid equipment, and in special cases, 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 mixed gas of dry air and oxygen.

[0081] After both gas source interfaces, a drying and filtering pipeline 1933 is connected. A 0.1μm sintered metal filter is内置 in the pipeline, which can intercept particulate matter (meeting the NAS1638 Class 5 level), protect the sensor mirror from pollution, remove the moisture in the gas source to prevent condensation, and at the same time 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, ensuring that the dew point of the input gas source reaches the technical requirement of below -70 degrees, and then passes through the corresponding automatic pressure and flow regulating valves for pressure regulation in sequence and汇入 the gas source main pipeline through the safety valve. After that, the gas source is split into two paths, one is a large-flow gas path and the other is a small-flow gas path.

[0082] The optimal installation method for the dew point sensor is to isolate it from the oxygen line. Install the sensor in a sampling unit, which is then connected to the oxygen line via a T-connector. A small amount of oxygen will be released and flow through the sensor. The sampling unit should be made of stainless steel and connected to the T-connector using a conduit (1 / 4” or 6mm). Install an isolation valve (001) between the sampling unit and the air line for easy sensor installation and removal.

[0083] In this embodiment, a sampling unit is formed from 316L stainless steel and connected to the main oxygen pipeline via a 1 / 4" (6mm) Swagelok tubing in a T-shape to form a bypass sampling system. The internal flow channels of the unit are optimized by CFD, and the flow velocity is controlled at 0.3-0.8m / s (compliant with ISO 8573-1 standard).

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

[0085] The specific design of the detection point at the stabilization section 130 is as follows: the first set of detection components is installed 1.5D (D is the pipe diameter) from the outlet of the stabilization section 130, and a laser TDLAS analyzer (measurement range 0-25% O, resolution 0.01%) and a paramagnetic oxygen analyzer are configured to obtain the reference oxygen concentration after pretreatment.

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

[0087] Kalman filtering was used to fuse oxygen detection data from two detection points, and a state equation was established:

[0088]

[0089] Where A is the system state transition matrix and H is the observation matrix, the noise variance is reduced by more than 60% (σ≤0.05%).

[0090] Embedded with the NIST REFPROP database, it compensates in real time for the effects of temperature (105K~334K) and pressure changes (0.1-1MPa) on oxygen partial pressure measurement. The compensation formula is as follows:

[0091]

[0092] Ensure that the measurement error is ≤ ±0.1% under all operating conditions.

[0093] Equipped with a dual-mode control system, a precision needle valve (adjustment accuracy ±0.01MPa) is installed downstream for pressure dew point measurement (maintaining process pressure ±2%), while a mass flow controller (MFC) is installed upstream for atmospheric pressure dew point measurement (flow stability ≤ ±1%FS). Compared to traditional single-dew point detection methods, its advantages are:

[0094] Traditional dew point response time is 60-120s, while the dew point response time of this design is ≤15s, representing an improvement of 75%-87%.

[0095] Traditional oxygen content measurement has a delay of 2-5 seconds. The oxygen content measurement in this design adopts data fusion measurement, with a delay of ≤0.8 seconds, and an improvement of 60% to 84%.

[0096] The traditional measurement calibration cycle has been changed from quarterly to annual, an improvement of 300%.

[0097] Automatic pressure / flow regulation pipeline 1937 employs a pressure drop compensation algorithm: in pressure dew point mode, it calculates the flow velocity-pressure drop relationship (ΔP=0.5ρv) in real time using Bernoulli's equation. 2 It dynamically compensates for dew point errors caused by pressure drop (compensation accuracy ±0.2℃); at the same time, it adopts limit flow rate protection, and the automatic pressure and flow regulating valve is equipped with a mechanical flow limiting orifice plate (orifice diameter Φ0.5-1.0mm adjustable) to ensure that the flow rate is ≤3m / s (an audible and visual alarm is triggered and the isolation valve is closed when the speed exceeds the limit).

[0098] The entire system's conduits are made of EP-grade electropolished stainless steel tubing (Ra≤0.4μm), fitted with VCR metal-sealed joints, with a water vapor permeability ≤5×10⁻⁶. -9 g / (m 2 The internal anti-adsorption treatment is applied, and the inner wall of the flow channel is coated with a nano-alumina coating (thickness 50-80nm), which reduces 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 its innovative isolation sampling structure, multi-physics field coupling compensation algorithm and redundant detection architecture, and can meet the stringent requirements of standards such as ISO 14624 and ECSS-Q-ST-70-01C.

[0100] Second Embodiment

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

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

[0103] The oxygen injection rake section 1945 is a flat circular plate with a cross-section shaped like a playground. The two arc-shaped sides of the oxygen injection rake section 1945 are provided with equally spaced exhaust holes 1946. The cross-section of the internal airflow pipe of the oxygen injection rake section 1945 is the same as the cross-section of the internal airflow pipe of the flat circular plate 1943.

[0104] The oxygen injection rake 194 can be a symmetrical design based on the rear section 1945 of the oxygen injection rake, which is aesthetically pleasing and facilitates the connection of the pipe body. 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 oxygen injection rake rear section 1945 has a long coverage area, approximately 2.4 meters to 4 meters. It can be of a fixed length, or it can be designed as an adjustable length structure or a segmented assembly structure by using a telescopic sleeve structure.

[0106] If the oxygen injection rake section 1945 is designed as a telescopic sleeve structure, it can be achieved through the following structure: nested inner and outer double-layer tubes, with guide fins on the inner tube wall; electric push rod adjustment mechanism, with real-time length value feedback through displacement sensor; and low-temperature resistant sealing material layer filling the gap between the tubes.

[0107] The gas supply pipe connecting flange 1944 serves as the air intake manifold, connecting to the output ends of the feedforward control line 191 and the feedback control line 192 respectively. The other end of the flat round body 1943 is equipped with a closed-loop fluid system connecting flange 1947, which is used to detachably install the oxygen injection rake 194 onto the closed-loop fluid equipment. It adopts an external installation structure, without changing the original wall surface and insulation layer of the closed-loop fluid system cavity.

[0108] The specific structure of the external mounting structure is initially designed as follows: from the inside out, it includes: an arc-shaped base that matches the curvature of the closed-loop fluid system wall; a high-temperature ceramic gasket isolation layer; and a prestressed bolt group, with the applied clamping force not exceeding 40% of the yield strength of the closed-loop fluid system shell material.

[0109] Third Embodiment

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

[0111] The compressor section, liquid nitrogen injection section, and heat exchange section start normally. When the Mach value, nitrogen pressure value, and total temperature value of the corresponding section reach the set value, the oxygen precision control system is activated.

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

[0113] Real-time monitoring of oxygen content is achieved by using an oxygen content detection component 180 configured in a closed-loop fluid equipment system to collect a baseline value of oxygen content within a set time interval before injection. The set time interval for the baseline value of oxygen content 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, the air compensation flow rate is calculated proportionally based on the real-time liquid nitrogen injection flow rate, and the oxygen injection component 190 is controlled to start injection synchronously.

[0115] When the liquid nitrogen injection flow rate exceeds the preset threshold, the total liquid nitrogen injection volume is recorded. The oxygen injection component 190 injects oxygen-containing flow at the maximum gas supply flow rate until the cumulative injection volume reaches the compensation amount 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 specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection 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 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, which are connected sequentially to form a U-shaped loop. An oxygen content detection assembly is installed between the stabilization section and the test chamber section. An oxygen injection assembly is installed in the oxygen injection section, and the oxygen injection assembly includes: The feedforward control pipeline serves as a high-flow gas path during the oxygen injection process. It receives feedforward control commands from the PLC. The feedforward control commands automatically accompany the liquid nitrogen injection based on the oxygen molecule demand calculated from the liquid nitrogen injection data using the ideal gas equation combined with the modified equation or simulation mode values. The feedback control pipeline, which serves as a low-flow gas path during the oxygen injection process, receives PID feedback control commands. These commands are based on the real-time oxygen content data obtained from the oxygen content measurement component and the liquid nitrogen injection data, which calculate the required amount of supplemental oxygen molecules.

2. The dual-mode oxygen-controlled continuous cooling 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 flow meter, a first pneumatic valve, a second pressure and temperature sensor, and one of the input terminals of the oxygen injection rake, which are connected in sequence. The real-time data of the first pneumatic valve is fed back to the PID control terminal.

3. The dual-mode oxygen-controlled continuous cooling closed-loop fluid system according to claim 2, characterized in that, The feedback control pipeline includes three parallel oxygen supply pipelines: a large, a medium, and a small oxygen supply pipeline. The large oxygen supply pipeline includes a second pneumatic regulating valve, a second vortex flow meter, 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 from the second pneumatic valve and the large / small mass flow control valve is fed back to the PID control terminal. The output terminals of the large, medium, and small oxygen supply pipelines converge at another input terminal of the oxygen injection rake.

4. The dual-modal oxygen-controlled continuous cooling closed-loop fluid system according to claim 3, characterized in that, The oxygen injection rake includes: The oxygen injection rake front section is composed of a cylinder, a transition body, and a flattened sphere connected in sequence. The flattened sphere has a "playground-shaped" cross-section. The transition body smoothly transitions from the cylinder to the flattened sphere. The cross-sectional area of ​​the internal airflow pipes of the cylinder, transition body, and flattened sphere is the same. The other end of the cylinder is equipped with an air supply pipe docking flange, and the other end of the flattened sphere is equipped with a closed-loop fluid system docking flange. The oxygen injection rake rear section is a flat circular plate with a "playground-shaped" cross-section. The two arc-shaped sides of the oxygen injection rake rear section are provided with equally spaced exhaust holes. The cross-section of the internal airflow pipe of the oxygen injection rake rear section is the same as the cross-section of the internal airflow pipe of the flat circular plate.

5. The dual-modal oxygen-controlled continuous cooling closed-loop fluid system according to claim 3, characterized in that, A gas source pretreatment component is connected before the oxygen injection assembly, and the gas source pretreatment component includes: An oxygen injection line, the oxygen injection line including an air inlet port and / or an oxygen inlet port; Drying and filtering tubing, connected to the output end of each of the aforementioned oxygen injection tubing; A dew point detection pipeline is connected to a branch pipeline at 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 to ensure that the gas dew point reaches below -70°C. An 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 equipped with an automatic pressure / flow regulating valve, and a safety valve is also installed on the manifold of the automatic pressure / flow regulating pipeline.

6. The dual-modal oxygen-controlled continuous cooling closed-loop fluid system according to claim 3, characterized in that, The oxygen content detection component is provided in at least two sets, one set is assembled at the rear end of the stabilization section, and the other set is assembled at the rear end of the test chamber section.

7. The dual-mode oxygen-controlled continuous cooling closed-loop fluid system according to claim 3, characterized in that, The parameters of the feedback control pipeline are configured as follows: Large oxygen supply pipeline, DN50 diameter, flow range 200-500 Nm 3 / h, control accuracy ±2%; Central oxygen supply pipeline, DN25 diameter, flow range 50-200 Nm 3 / h, control accuracy ±0.5%; Small oxygen supply pipeline, DN10 diameter, flow range 5-50 Nm 3 / h, control accuracy ±0.1%.

8. A precise control method for a dual-modal oxygen-controlled continuous cooling closed-loop fluid system, comprising the continuous cooling closed-loop fluid system as described in any one of claims 1-7, characterized in that, The precise control method includes the following steps: Read liquid nitrogen injection data to obtain liquid nitrogen injection flow rate and injection time parameters in real time for the liquid nitrogen injection section; Real-time monitoring of oxygen content is achieved by using an oxygen content detection component configured in a closed-loop fluid equipment system to collect baseline values ​​of oxygen content for a 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 based on 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 volume is recorded, and the oxygen injection component injects oxygen-containing flow at the maximum gas supply flow rate until the cumulative injection volume reaches the compensation amount corresponding to the total liquid nitrogen injection volume.

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

10. The precise control method for the dual-modal oxygen-controlled continuous cooling 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 assembly.

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