A method of designing an air separation unit based on inertization time

Abstract

This invention discloses a design method for an air separation device based on inertia time: S1. Construct a set of nitrogen-rich gas flow rates based on the nitrogen-rich gas flow rate with oxygen concentration x at various pressures; S2. Calculate the effective membrane area S0 of the air separation device sample; S3. Construct a set of nitrogen-rich gas flow rates Q per unit membrane area based on the nitrogen-rich gas flow rate with oxygen concentration x at various pressures per unit membrane area. 0,x S4. Input the air separation inlet pressure P and the oil tank volume V; S5. Calculate the effective membrane area S for each combination of membrane core length and diameter. i S6. Calculate the nitrogen-rich gas flow rate Q with concentration x for each combination of membrane core length and diameter, given the air separation inlet pressure P. x,i S7. Calculate the initial inerting time t at x concentration for each combination of membrane core length and diameter. x,i S8. Screen the membrane core length and diameter combinations that meet the initial inertization time, and determine the lightest membrane core length and diameter combination. This invention can improve design efficiency and shorten the research and development cycle.

Description

Technical Field

[0001] This invention relates to the field of aircraft fire prevention and explosion suppression technology, specifically to a design method for an air separation device based on inertia time. Background Technology

[0002] With increasingly stringent safety requirements for fuel tanks in modern aircraft, onboard nitrogen generation systems, as crucial protective equipment, have become standard equipment on various military and civilian aircraft. This system effectively reduces the oxygen concentration within the fuel tank by supplying nitrogen-rich gas to the air separation unit (AS / RS), thereby preventing potential fire risks. As the core component of the onboard nitrogen generation system, the performance of the AS / RS directly impacts aircraft flight safety.

[0003] However, there are many problems in the design process of existing air separation devices: First, the design phase usually only focuses on single-point performance indicators (such as generating nitrogen-rich gas with a concentration not lower than a certain flow rate under a certain pressure), while ignoring the complex requirements of the overall system operation conditions; Second, the design scheme often adopts empirical trial and error or iterative methods to determine the structural dimensions, which can easily lead to problems of over- or under-performance, which not only increases the research and development cycle and cost, but may also affect the reliability and economy of the system.

[0004] Especially regarding the critical indicator of inerting time (i.e., the time required for the oxygen concentration in the fuel tank to drop to a safe level), existing design methods lack systematic trade-off optimization techniques. The structural parameters of the air separation unit have a direct impact on its performance and weight, but achieving the optimal combination of structural dimensions while meeting the inerting time requirements has always been a design challenge. Summary of the Invention

[0005] The purpose of this invention is to provide a design method for an air separation device based on inertia time. This invention can effectively improve design efficiency, shorten the development cycle, and reduce development costs, while providing stronger guarantees for the safety and reliability of aircraft.

[0006] Technical solution. A design method for an air separation device based on inertization time, comprising the following steps: S1. Construct a set of nitrogen-rich gas flow rates Q based on the nitrogen-rich gas oxygen concentration x at various pressures. x ; S2. Calculate the effective membrane area S0 of the air separation device sample; S3. Based on the nitrogen-rich gas flow rate with oxygen concentration x at various pressures per unit membrane area, construct the nitrogen-rich gas flow rate set Q per unit membrane area. 0,x ; S4. Input air separation inlet pressure P and oil tank volume V; S5. Calculate the effective membrane area S for each combination of membrane core length and diameter. i ; S6. Calculate the nitrogen-rich gas flow rate Q for x concentration under each combination of membrane core length and diameter, given the air separation inlet pressure P. x,i ; S7. Calculate the initial inerting time t at x concentration for each combination of membrane core length and diameter. x,i ; S8. Screen the membrane core length and diameter combinations that meet the initial inerting time requirements, and determine the membrane core length and diameter combinations with the lightest weight.

[0007] In the aforementioned design method for an air separation device based on inertia time, x in S1 takes values ​​of 2% to 9%.

[0008] In the aforementioned design method for an air separation device based on inertia time, in S2, , Where n is the number of membrane filaments, S m This represents the effective surface area of ​​a single membrane filament.

[0009] In the aforementioned design method for an air separation device based on inertia time, in S3, .

[0010] In the aforementioned design method for an air separation device based on inertia time, in S5, , In the formula, L i D i L represents the length and diameter of membrane core i, respectively. i ∈L [1-i] D i ∈D [1-i] ;d in d is the inner diameter of a single membrane filament. out The outer diameter of a single membrane filament; L h The epoxy resin casting height is represented by z; the film fiber filling rate is represented by L. [1-i] Diameter sequence D [1-i] These are the core length sequence and the diameter sequence, respectively.

[0011] In the aforementioned design method for an air separation device based on inertia time, in S6, .

[0012] In the aforementioned design method for an air separation device based on inertia time, in S7, , In the formula, ρ is the air density at the air separation inlet pressure P, and O x For nitrogen-rich gas oxygen concentration, O m To achieve the required oxygen concentration in the fuel tank for inerting, O amb V represents the oxygen concentration in the atmosphere, and V represents the volume of the fuel tank.

[0013] In the aforementioned design method for an air separation device based on inertia time, S8 is specifically as follows: the initial inertia time for each combination is taken as the minimum value under different concentration ranges, and the calculation formula is as follows: , Select membrane core length and diameter combinations that meet the initial inertization time requirements; Calculate the membrane core weight (m) i Determine the combination of membrane core length and diameter for the lightest possible weight, and the membrane core weight in m. i The calculation formula is as follows: , Where, ρ m ρ is the density of the membrane fibers. h This represents the density of the epoxy resin.

[0014] Beneficial Effects: This invention proposes a method that comprehensively considers the performance and structural parameters of an air separation unit. While ensuring system inertia time, it rapidly generates multiple optimized combinations of structural dimensions and obtains the optimal solution through calculation and selection. This method will effectively improve design efficiency, shorten the R&D cycle, and reduce development costs, while providing stronger guarantees for the safety and reliability of aircraft.

[0015] Through systematic analysis and calculation, this invention achieves a reasonable allocation of structural parameters for the air separation unit while meeting the fuel tank inerting requirements, and completes a lightweight design based on this.

[0016] The core idea of ​​this invention lies in comprehensively balancing the inerting performance of the inerting system, the performance indicators of the device, and structural parameters. By generating multiple combinations of structural dimensions and calculating their corresponding system performance and device weight, the optimal solution is selected. Specifically, this method avoids the problem of unreasonable structural dimensions caused by focusing only on a single performance indicator in traditional design processes, while meeting the initial inerting time requirements of the air separation device. This invention is achieved through the following technical solutions.

[0017] By preparing a prototype of the air separation device, reliable basic data can be provided for subsequent performance testing and model building, ensuring the verifiability and practicality of the design results, greatly shortening the R&D cycle and reducing trial and error costs, and providing a reliable foundation for subsequent performance testing.

[0018] The flow rate of nitrogen-rich gas under different pressures was measured and a flow rate dataset was constructed. The flow rate of nitrogen-rich gas was measured under multiple pressure conditions, and a flow rate database was built through data collection, providing comprehensive support for subsequent performance evaluation.

[0019] The sample was disassembled and the membrane core and filaments were measured. Decoupling analysis was employed to separate the structural parameters from the system performance for further study. Precise measurement of the sample's structural parameters yielded data on key components, providing the necessary support for establishing an accurate model. Traditional design methods do not consider the parameters of the membrane core and filaments, focusing only on single-point performance indicators. Therefore, this step provides the necessary parameters for accurate calculations, improving the accuracy of air separation unit performance calculations and structural design by more than 20%.

[0020] The effective membrane area is calculated based on membrane fiber data, innovatively introducing a precise correspondence between geometric parameters and performance parameters. The effective membrane area is accurately determined using the number of membrane fibers and the surface area of ​​a single fiber, improving the model's accuracy and repeatability.

[0021] A set of nitrogen-rich gas flow rates per unit membrane area was constructed. Through standardization, complex system-level data was transformed into a single parameter that is easy to analyze, and flow rate data was transformed into a unit membrane area index, providing a new benchmark for the design and optimization of structural parameters.

[0022] By inputting the air separation inlet pressure P and the fuel tank volume V, this invention introduces inerting system-level data into the design of air separation units for the first time. A system-level performance prediction model is established, and the inlet pressure and fuel tank volume are input as important factors into the system for calculation. This is the first time that the performance of the inerting system has been taken into account in the design of air separation units. It connects the working process of typical inerting systems, such as engine bleed air, inerting system gas treatment, air separation, nitrogen-rich gas distribution, and fuel tank inerting, improving the accuracy and relevance of the inerting time calculation and ensuring that the design meets actual requirements.

[0023] The system generates membrane core length and diameter sequences, employing a systematic parameter combination method to cover multi-dimensional design possibilities. By automatically generating a large number of design schemes, it significantly improves design exploration efficiency and provides a rich data foundation for subsequent optimization. Comprehensive coverage of the design space ensures the finding of the optimal solution. Compared to the traditional design-prototype-verification-iteration design method for air separation units, this approach greatly improves design efficiency, avoids design changes, and reduces design, production, and verification costs.

[0024] The effective membrane area of ​​each combination is calculated, and the correspondence between the effective membrane area and the structural dimensions is established by applying the infinitesimal method. This ensures the accuracy and applicability of the calculation results and reduces the excessive reliance on experience in traditional methods.

[0025] The flow rate of nitrogen-rich gas for each combination was calculated. Based on the analysis of experimental data, it was found that the flow rate of nitrogen-rich gas in the air separation unit is proportional to the effective membrane area. A multi-dimensional performance prediction equation was constructed to achieve accurate simulation of the flow rate of nitrogen-rich gas in the air separation unit.

[0026] The initial inerting time for each combination was calculated, and a mathematical model for calculating the initial inerting time of the inerting system was introduced. The initial inerting time was combined with the membrane core performance, which ensured safety indicators while improving design efficiency.

[0027] By selecting membrane core length and diameter combinations that meet the initial inerting time requirements and setting strict selection criteria, the safety of the design scheme was ensured. Furthermore, by combining system performance under different nitrogen-enriched gas concentrations, multi-objective optimization was achieved, addressing the constraints between system performance, gas flow rate, and size. This improved the safety, economy, and manufacturability of the inerting system, significantly enhancing the quality of the design scheme.

[0028] By calculating the membrane core weight and determining the minimum weight combination of membrane core length and diameter, the lightweight design principles of the inerting system were introduced into the design of key components. Under the premise of meeting performance requirements, a method for calculating the weight of the air separation unit was proposed, optimizing structural dimensions and achieving the best balance between lightweight design, performance, and economy.

[0029] In summary, this invention achieves systematic optimization of the structural parameters of an air separation unit through a trade-off method based on inertia time. While meeting system inertia time requirements, it avoids the problem of unreasonable structural dimensions caused by focusing only on single-point performance in traditional designs. Secondly, this method can quickly generate multiple combinations of structural dimensions and calculate their corresponding system performance and unit weight, significantly improving design efficiency and reducing the development cycle and cost waste caused by repeated trial and error. Furthermore, by comprehensively balancing the relationship between performance and structural parameters, this method can achieve lightweighting and miniaturization of the air separation unit while ensuring safety and reliability, further improving the system's economics. Finally, this invention provides a scientific and efficient design method that can quickly select the optimal solution, providing more reliable technical protection for the safety of aircraft fuel tanks. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A diagram illustrating the calculation process; Figure 2 This is a schematic diagram of the structure. Detailed Implementation

[0032] 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, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0034] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0036] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0038] Example 1. The present invention addresses, for example, Figure 1 The flowchart shown illustrates the design of an air separation device. The specific design method includes the following steps: Prepare a prototype of the air separation device; The flow rates of nitrogen-rich gas with an oxygen concentration of x (ranging from 2% to 9%) were measured at different pressures to construct a nitrogen-rich gas flow rate set Q. x ; Disassemble the sample and measure the membrane core and membrane filament data; The effective membrane area S0 of the sample model is calculated based on the membrane core and membrane fiber data. The calculation formula is as follows:

[0039] Where n is the number of membrane filaments, S m The effective surface area of ​​a single membrane filament; Calculate the flow rate of nitrogen-rich gas with oxygen concentration x at different pressures per unit membrane area, in order to construct the set Q of nitrogen-rich gas flow rates per unit membrane area. 0,x ;

[0040] Input the air separation inlet pressure P and the oil tank volume V; Generate membrane core length sequence L [1-i] Diameter sequence D [1-i] ; Calculate the effective membrane area S for each combination of membrane core length and diameter. i ;

[0041] Among them, L i D i These are the length and diameter of the membrane core, L, respectively. i ∈L [1-i] D i ∈D [1-i] ,d in d represents the inner diameter of a single membrane filament (valued at 0.2 mm). out L represents the outer diameter of a single membrane filament (valued at 0.32 mm). h Z represents the epoxy resin casting height (40 mm), and z represents the membrane fiber filling rate (0.59). A typical air separation unit structure is shown below. Figure 2 ; For the air separation inlet pressure P, calculate the nitrogen-rich gas flow rate Q with concentration x for each combination of membrane core length and diameter. x,i The calculation formula is as follows:

[0042] The initial inerting time is calculated for each combination of membrane core length and diameter at concentration x. The initial inerting time for a specific nitrogen-rich gas with oxygen concentration x is calculated using the following formula:

[0043] in, O is the air density at the air separation inlet pressure P. x The oxygen concentration of nitrogen-rich gas (values ​​range from 2% to 9%), O m The required oxygen concentration in the fuel tank for inerting (generally 12% for civilian aircraft and 9% for military aircraft), O amb V represents the oxygen concentration in the atmosphere (valued at 21%), and V represents the volume of the fuel tank.

[0044] The initial inerting time for each combination is taken as the minimum value under different concentration ranges, and the calculation formula is as follows:

[0045] Select membrane core length and diameter combinations that meet the initial inertization time requirements; Calculate the membrane core weight (m) i Determine the combination of membrane core length and diameter for the lightest possible weight, and the membrane core weight in m. i The calculation formula is as follows:

[0046] Where, ρ m ρ represents the membrane fiber density (valued at 0.0296 g / fiber / meter). h The density of epoxy resin (value taken as 0.0013254 g / mm³) 3 ).

[0047] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A design method for an air separation device based on inertia time, characterized in that, Includes the following steps: S1. Construct a set of nitrogen-rich gas flow rates Q based on the nitrogen-rich gas oxygen concentration x at various pressures. x ; S2. Calculate the effective membrane area S0 of the air separation device sample; S3. Based on the nitrogen-rich gas flow rate with oxygen concentration x at various pressures per unit membrane area, construct the nitrogen-rich gas flow rate set Q per unit membrane area. 0,x ; S4. Input air separation inlet pressure P and oil tank volume V; S5. Calculate the effective membrane area S for each combination of membrane core length and diameter. i ; S6. Calculate the nitrogen-rich gas flow rate Q for x concentration under each combination of membrane core length and diameter, given the air separation inlet pressure P. x,i ; S7. Calculate the initial inerting time t at x concentration for each combination of membrane core length and diameter. x,i ; S8. Screen the membrane core length and diameter combinations that meet the initial inerting time requirements, and determine the lightest membrane core length and diameter combination.

2. The design method of the air separation device based on inertia time according to claim 1, characterized in that, In S1, x takes values ​​from 2% to 9%.

3. The design method of the air separation device based on inertia time according to claim 1, characterized in that, In S2, ， Where n is the number of membrane filaments, S m This represents the effective surface area of ​​a single membrane filament.

4. The design method of the air separation device based on inertia time according to claim 1, characterized in that, In S3, 。 5. The design method of the air separation device based on inertia time according to claim 1, characterized in that, In S5, ， In the formula, L i D i L represents the length and diameter of membrane core i, respectively. i ∈L [1-i] D i ∈D [1-i] ;d in d is the inner diameter of a single membrane filament. out The outer diameter of a single membrane filament; L h The epoxy resin casting height is represented by z; the film fiber filling rate is represented by L. [1-i] Diameter sequence D [1-i] These are the core length sequence and the diameter sequence, respectively.

6. The design method of the air separation device based on inertia time according to claim 1, characterized in that, In S6, 。 7. The design method of the air separation device based on inertia time according to claim 1, characterized in that, In S7 ， In the formula, ρ is the air density at the air separation inlet pressure P, and O x For nitrogen-rich gas oxygen concentration, O m To achieve the required oxygen concentration in the fuel tank for inerting, O amb V represents the oxygen concentration in the atmosphere, and V represents the volume of the fuel tank.

8. The design method of the air separation device based on inertia time according to claim 1, characterized in that, S8 is as follows: The initial inerting time for each combination is taken as the minimum value under different concentration ranges, and the calculation formula is as follows: ， Select membrane core length and diameter combinations that meet the initial inertization time requirements; Calculate the membrane core weight (m) i Determine the combination of membrane core length and diameter for the lightest possible weight, and the membrane core weight in m. i The calculation formula is as follows: ， Where, ρ m ρ is the density of the membrane fibers. h This represents the density of the epoxy resin.

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