Fire behavior intelligent control method based on high-temperature cabin of high-speed aircraft

Abstract

The invention belongs to the field of aircraft fire prevention system design, and particularly relates to an intelligent fire control method based on high-speed aircraft high-temperature cabins, which comprises the following steps of: calculating the concentration distribution condition of a fire extinguishing agent in each aircraft high-temperature cabin based on a simulation result, and setting a preliminary fire control strategy; then fire behavior control algorithm design of the controller is carried out based on the fire extinguishing agent concentration distribution condition, and an optimal fire behavior control strategy is obtained; a fire extinguishing strategy is formed through analysis and calculation of the controller according to the state of a reconstructed fire behavior simulated by the controller and development trend prediction of the reconstructed fire behavior, and the reasonable dosage of the fire extinguishing agent sprayed by the flow-adjustable fire extinguishing agent nozzles at different positions of each cabin area is intelligently controlled, so that the fire extinguishing agent forms the minimum fire extinguishing concentration meeting the requirement only in a fire behavior area and lasts for a certain time; and moreover, the chemical reaction of the fire extinguishing agent under a high-temperature condition interrupts a combustion reaction chain, and finally accurate control over the fire behavior is achieved.

Description

Technical Field

[0001] This application belongs to the field of aircraft fire protection system design, and specifically relates to an intelligent fire control method for high-temperature cabin areas of high-speed aircraft. Background Technology

[0002] Aircraft fires are among the most serious safety incidents during aircraft use and maintenance. Fires in areas such as the engine compartment, equipment compartment, and landing gear compartment are significant contributing factors. These compartments are confined spaces, and leaks in fuel lines can easily ignite upon contact with heat sources, spreading rapidly and causing damage to onboard systems with severe consequences. As new-generation aircraft evolve towards high speed and stealth capabilities, the power of electrical equipment, hydraulic drives, and aerodynamic heat have increased dramatically. Different compartments within an aircraft exhibit varying temperatures, pressures, and ventilation volumes, with some areas (such as the engine compartment) reaching temperatures as high as 600°C. Fires in different compartments develop and progress in different ways (smoke, flames, temperature changes, etc.), and these factors change in real time after a fire begins. Therefore, fire prevention systems must quickly and accurately detect and precisely control the fire in each area under these complex and variable conditions.

[0003] In traditional aircraft fire suppression systems, when overheating is detected within a cabin area, extinguishing agents such as Halon 1301 and ultrafine dry powder are released through fire extinguishing cylinders, transported via fire extinguishing pipelines, and injected into the fire area through nozzles. When the temperature field distribution within the fire zone cannot be confirmed, the amount of extinguishing agent sprayed often far exceeds the actual required amount to ensure complete fire suppression. For some high-speed aircraft, due to the overall thermal load, there are many cabin areas at risk of fire. Current traditional fire suppression system designs require the aircraft to carry a huge volume of extinguishing agent, which cannot meet the overall center of gravity control requirements of the aircraft. Furthermore, the ambient temperature and flow field structure vary between different cabin areas, resulting in significant differences in flame spread. Therefore, it is necessary to tailor fire suppression plans based on the temperature field distribution within the cabin area under fire conditions to achieve fire suppression with minimal extinguishing agent consumption.

[0004] The existing intelligent fire control system needs to address the following issues:

[0005] New high-speed aircraft have more high-temperature cabin areas, increasing the areas prone to fire and the volume of the fire zone. According to the current traditional fire extinguishing system design method, the extinguishing agent dosage is designed according to the maximum fire extinguishing demand. When a fire occurs, all the extinguishing agent is released to make the entire fire zone reach the required extinguishing agent concentration. However, during the duration of meeting the required extinguishing agent concentration, the distribution of extinguishing agent is not uniform. First, there is a certain amount of extinguishing agent in areas where the flames have not spread. Second, the extinguishing agent concentration in some fire areas exceeds the demand, even reaching 6-10 times the required extinguishing agent concentration, resulting in the waste of extinguishing agent.

[0006] Therefore, it is essential to conduct research on intelligent fire control methods by controlling the concentration of extinguishing agents. Summary of the Invention

[0007] The purpose of this application is to provide an intelligent fire control method for high-temperature compartments of high-speed aircraft, in order to solve the problem that it is difficult to meet fire extinguishing requirements with minimal fire extinguishing agent consumption in the existing technology.

[0008] The technical solution of this application is: a fire intelligent control method based on the high-temperature compartment of a high-speed aircraft, comprising:

[0009] Acquire the layout and geometric data of each high-temperature compartment of the aircraft, construct a general fire model of the high-temperature compartment of the aircraft, perform CFD simulation calculations, and obtain simulation results;

[0010] Based on the simulation results, the distribution of fire extinguishing agent concentration in the high-temperature compartment of each aircraft is calculated, a preliminary fire control strategy is set, and then the fire control algorithm of the controller is designed based on the distribution of fire extinguishing agent concentration to obtain the optimal fire control strategy.

[0011] Fire extinguishing experiments were conducted based on the optimal fire control strategy, and the optimal fire control strategy was iteratively optimized based on the experimental results until the minimum extinguishing agent consumption converged.

[0012] Preferably, when performing CFD simulation calculations, a typical mission profile of the current aircraft is obtained, along with the flight altitude, speed, and ambient temperature under the current high-temperature compartment layout, and CFD simulation calculations are carried out based on the geometric structure data.

[0013] Preferably, the simulation results include the development process of fires in different compartments and locations from occurrence to combustion over a certain period of time, and obtain the changes of various parameter domains in the compartments over time after the fire occurs, including the changes of temperature field, light intensity and combustion gas concentration with respect to the parameter domains, as characteristic parameters for judging the fire and predicting the fire trend.

[0014] Preferably, the preliminary fire control strategy includes: rationally arranging fire extinguishing agent nozzles in the high-temperature compartment of the aircraft and designing a flow-adjustable spray network; controlling the flow rate of the fire extinguishing agent by adjusting the spray rate and time; and conducting fire extinguishing agent concentration simulation analysis to calculate the distribution of fire extinguishing agent concentration in each high-temperature compartment of the aircraft under different conditions of opening different fire extinguishing agent nozzles and different fire extinguishing agent spray amounts.

[0015] Preferably, a generalized fire model for high-temperature compartments of aircraft is constructed based on the mass conservation equation, energy conservation equation, and heat conservation equation, specifically as follows:

[0016] The mass conservation equation can be described as follows: Within a unit time, the net mass flowing into a fluid element is equal to the increase in the element's mass; the expression is:

[0017] ;

[0018] In the formula, ρ represents fluid density; u, v, and w represent fluid velocities in different directions; t represents time.

[0019] The energy conservation equation can be described as follows: the rate of increase of energy within a fluid element is equal to the sum of the net heat flow into the element and the work done on the element by the surrounding environment; the expression is:

[0020] ;

[0021] In the formula, The average velocity of the fluid; It is a volume force; P x P y P z These are surface forces in the x, y, and z directions;

[0022] The heat conservation equation is:

[0023] ;

[0024] In the formula, C p is the specific heat capacity at constant pressure of the fluid; k is the heat transfer coefficient of the fluid; 𝑆 𝑇 The heat source within the fluid and the increase in heat due to friction caused by viscosity; T is the temperature.

[0025] Preferably, the CFD simulation calculation uses the RNG k-ε two-equation model, and the k-equation and ε-equation in the RNG k-ε model are as follows:

[0026] ;

[0027] ;

[0028] In the formula, , , , , , , , , , , .

[0029] Preferably, fire dynamics simulation software is used to conduct numerical simulation studies on typical oil mist fires and oil pool fires inside the cabin, analyze the ignition process and flame propagation law inside the cabin, obtain the velocity field, temperature field and heat flow inside the cabin, compare and analyze with the experimental results, and obtain the optimal fire control strategy.

[0030] Preferably, the Clausius-Clapeyron equations are used for solving the fire dynamics simulation software, specifically as follows:

[0031] The evaporation rate is determined by the latent heat of vaporization and the evaporation temperature, as shown in the following equation:

[0032] ;

[0033] In the formula, X F,l H represents the concentration of fuel vapor. V For the latent heat of vaporization, W F T is the molar mass of fuel. s For surface temperature, T b This refers to the evaporation temperature.

[0034] The turbulent combustion model adopts a vortex dissipation model based on the mixing fraction, and the combustion reaction mechanism adopts a single-step reaction, as shown in the following equation:

[0035] ;

[0036] mass fraction Y s It is time t and temperature T s The function, with the following expression:

[0037] ;

[0038] In the formula, A is the pre-exponential factor, E is the activation energy, and R is a constant;

[0039] Based on this, the fire control algorithm of the controller is designed, and the optimal fire control strategy is formed according to the fire distribution reconstructed by the controller and the predicted fire development trend.

[0040] The intelligent fire control method for high-temperature compartments of high-speed aircraft proposed in this application, based on the simulated reconstruction of the fire state and its development trend by the controller, and after analysis and calculation by the controller, forms a fire extinguishing strategy. It intelligently controls the adjustable flow rate fire extinguishing agent nozzles at different locations in each compartment to spray the appropriate dosage of fire extinguishing agent, so that the fire extinguishing agent forms the minimum required fire extinguishing concentration in the fire area and continues for a certain period of time, physically achieving the effect of oxygen isolation and asphyxiation. Moreover, the chemical reaction of the fire extinguishing agent under high temperature conditions interrupts the combustion reaction chain, ultimately achieving precise control of the fire. Attached Figure Description

[0041] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0042] Figure 1 This is a schematic diagram of the overall process of this application. Detailed Implementation

[0043] 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. 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.

[0044] A smart fire control method for high-temperature compartments of high-speed aircraft.

[0045] like Figure 1 As shown, it includes the following steps:

[0046] Step S100: Obtain the layout and geometric structure data of each high-temperature compartment of the aircraft, construct a general fire model of the high-temperature compartment of the aircraft, perform CFD simulation calculations, and obtain simulation results;

[0047] The high-temperature compartments of an aircraft have complex layouts and diverse geometric structures, and the internal temperature and airflow conditions have a certain impact on the spread and development of a fire and the effectiveness of fire extinguishing agents.

[0048] Preferably, a generalized fire model for high-temperature compartments of aircraft is constructed based on the mass conservation equation, energy conservation equation, and heat conservation equation, specifically as follows:

[0049] The law of conservation of mass can be described as follows: Within a unit time, the net mass flowing into a fluid element is equal to the increase in the element's mass. The expression is:

[0050] (1)

[0051] In the formula, denoted as fluid density; u, v, and w represent fluid velocities in different directions; and t represents time.

[0052] The energy conservation equation can be described as follows: the rate of increase of energy within a fluid element is equal to the sum of the net heat flow into the element and the work done on the element by the surrounding environment. The expression is:

[0053] (2)

[0054] In the formula, The average velocity of the fluid; It is a volume force; P x P y P z These are the surface forces in the x, y, and z directions.

[0055] The heat conservation equation is:

[0056] (3)

[0057] In the formula, C p is the specific heat capacity at constant pressure of the fluid; k is the heat transfer coefficient of the fluid; 𝑆 𝑇 The heat source within the fluid and the increase in heat due to friction caused by viscosity; T is the temperature.

[0058] Preferably, when performing CFD simulation calculations, a typical mission profile of the current aircraft is obtained, and the changes in multiple parameters such as flight altitude, speed and ambient temperature under the current high-temperature compartment layout are obtained, and CFD simulation calculations are carried out based on the geometric structure data.

[0059] The simulation results include the development process of fires in different compartments and locations from occurrence to combustion over a certain period of time, and obtain the changes of various parameter domains in the compartments over time after the fire occurs, including the changes of temperature field, light intensity and combustion gas concentration, etc., as characteristic parameters for judging the fire and predicting the fire trend.

[0060] The causes and processes of fires in the high-temperature compartments of aircraft were analyzed. Based on the above CFD simulation results, the fire development process was simulated and calculated.

[0061] Preferably, the CFD simulation uses the RNG k-ε two-equation model, and the standard wall function is selected. Currently, the two-equation model is the most widely used in engineering, and the most basic two-equation model is the standard k-ε model. The RNG k-ε model is derived from the Standard k-ε model. The RNG k-ε model incorporates the effects of small scales into large-scale motion and the modified viscous terms, thus removing small-scale motion systems from the governing equations. The k (turbulent kinetic energy) equation and ε (dissipation rate) equation in the RNG k-ε model are as follows:

[0062] (4)

[0063] (5)

[0064] In the formula, , , , , , , , , , , .

[0065] The RNG k-ε model, by correcting for turbulent viscosity, can simulate rotating and swirling flows in time-averaged flow; the dissipation rate equation considers the mainstream time-averaged strain rate E. ij Therefore, the generation terms of the RNG k-ε model are not only related to the flow but also become functions of the flow field coordinates. For near-wall flows and flows with low Reynolds numbers, wall functions are used for processing.

[0066] The causes and processes of fires in high-temperature compartments of aircraft were analyzed. Based on the aforementioned CFD simulation results, the fire development process was simulated. The simulation calculated the development process of fires in different compartments and locations from occurrence to combustion over a certain period of time, and obtained the changes of various parameter domains within the compartments over time after the fire occurred, such as the changes in temperature field, light intensity, and combustion gas concentration. These parameters serve as characteristic parameters for judging the fire situation and predicting fire trends.

[0067] Step S200: Calculate the distribution of fire extinguishing agent concentration in the high-temperature compartment of each aircraft based on the simulation results, set a preliminary fire control strategy, and then design the fire control algorithm of the controller based on the distribution of fire extinguishing agent concentration to obtain the optimal fire control strategy.

[0068] Preferably, the preliminary fire control strategy includes: based on the flame spread during the fire development process as shown in the simulation results, rationally arranging fire extinguishing agent nozzles in the high-temperature compartments of the aircraft and designing an adjustable flow rate spray network. By adjusting the fire extinguishing agent spray rate and time, the flow rate of the fire extinguishing agent can be controlled, serving as a prerequisite for precise fire control. Simultaneously, fire extinguishing agent concentration simulation analysis is conducted to calculate the distribution of fire extinguishing agent concentration in each high-temperature compartment of the aircraft under different conditions of opening different fire extinguishing agent nozzles and spraying different amounts of fire extinguishing agent.

[0069] Numerical simulation studies of typical oil mist fires and oil pool fires inside the chamber were conducted using fire dynamics simulation software. The ignition process and flame propagation laws inside the chamber were analyzed, and key parameters such as velocity field, temperature field, and heat flow inside the chamber were obtained and compared with experimental results.

[0070] According to the Clausius-Clapeyron equation, the evaporation rate is determined by the latent heat of vaporization and the evaporation temperature, as shown in the following equation:

[0071] (6)

[0072] In the formula, X F,l H represents the concentration of fuel vapor. V For the latent heat of vaporization, WF T is the molar mass of fuel. s For surface temperature, T b This is the evaporation temperature.

[0073] The turbulent combustion model adopts a vortex dissipation model based on the mixing fraction, and the combustion reaction mechanism adopts a single-step reaction, as shown in the following equation:

[0074] (7)

[0075] Solid fuel fires require setting parameters for both pyrolysis products and the pyrolysis rate. Regarding pyrolysis products, the pyrolysis products of combustible materials include combustible gases and solid residues. As for the pyrolysis rate, pyrolysis begins when the temperature reaches a certain value; as the mass fraction decreases, the reaction rate increases, and the temperature at which the reaction rate reaches its peak is the reference temperature for FDS (Fuel Dissolved Solids). Pyrolysis occurs before the reference temperature, and the pyrolysis of fuel requires the absorption of a certain amount of heat, known as the heat of reaction. Studies have shown that the mass fraction Y... s It is time t and temperature T s The function, with the following expression:

[0076] (8)

[0077] In the formula, A is the pre-exponential factor, E is the activation energy, and R is a constant.

[0078] Based on this, the fire control algorithm of the controller is designed. According to the fire distribution and predicted fire development trend reconstructed by the controller, the optimal fire control strategy is formed. By opening a certain number of fire extinguishing agent nozzles and spraying a certain amount of fire extinguishing agent at a certain rate, an effective fire extinguishing concentration is formed, and the fire in each high-temperature compartment is accurately controlled.

[0079] Step S300: Conduct fire extinguishing tests based on the optimal fire control strategy, and iteratively optimize the optimal fire control strategy based on the test results until the minimum fire extinguishing agent consumption converges.

[0080] When conducting fire extinguishing tests, the risk level and fuel type are first set. Then, based on the current distribution of extinguishing agent and extinguishing agent nozzles, the fuel is ignited to generate a fire of the set risk level, and the fire is extinguished using the extinguishing agent. The extinguishing agent concentration distribution in each area during fire extinguishing is collected and compared with the optimal fire control strategy. Optimization is carried out for areas where the difference does not meet the optimal fire control strategy.

[0081] In summary, this application, based on the controller's simulation and reconstruction of the fire's state and its development trend prediction, and after analysis and calculation by the controller, forms a fire extinguishing strategy. It intelligently controls the adjustable flow rate of the fire extinguishing agent nozzles at different locations in each compartment to spray a reasonable dosage of fire extinguishing agent, so that the fire extinguishing agent forms the minimum required fire extinguishing concentration only in the fire area and remains there for a certain period of time, physically achieving an oxygen-isolating and asphyxiating effect. Furthermore, the chemical reaction of the fire extinguishing agent under high-temperature conditions interrupts the combustion reaction chain, ultimately achieving precise, efficient, and reasonable control of the fire.

[0082] Finally, it should be noted that the accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0083] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for intelligent fire control in the high-temperature compartment of a high-speed aircraft, characterized in that, include: Acquire the layout and geometric data of each high-temperature compartment of the aircraft, construct a general fire model of the high-temperature compartment of the aircraft, perform CFD simulation calculations, and obtain simulation results; Based on the simulation results, the distribution of fire extinguishing agent concentration in the high-temperature compartment of each aircraft is calculated, a preliminary fire control strategy is set, and then the fire control algorithm of the controller is designed based on the distribution of fire extinguishing agent concentration to obtain the optimal fire control strategy. Fire extinguishing experiments were conducted based on the optimal fire control strategy, and the optimal fire control strategy was iteratively optimized based on the experimental results until the minimum extinguishing agent consumption converged.

2. The intelligent fire control method based on the high-temperature compartment of a high-speed aircraft as described in claim 1, characterized in that: When performing CFD simulation calculations, a typical mission profile of the current aircraft is obtained, along with the flight altitude, speed, and ambient temperature under the current high-temperature compartment layout. CFD simulation calculations are then carried out based on the geometric data.

3. The intelligent fire control method based on the high-temperature compartment of a high-speed aircraft as described in claim 2, characterized in that: The simulation results include the development process of fires in different compartments and locations from occurrence to combustion over a certain period of time, and obtain the changes of various parameter domains in the compartments over time after the fire occurs, including the changes of temperature field, light intensity and combustion gas concentration with respect to the parameter domains, as characteristic parameters for judging the fire and predicting the fire trend.

4. The intelligent fire control method for high-temperature compartments of high-speed aircraft as described in claim 1, characterized in that, The preliminary fire control strategy includes: rationally arranging fire extinguishing agent nozzles in the high-temperature compartments of the aircraft and designing a flow-adjustable spray network; controlling the flow rate of the fire extinguishing agent by adjusting the spray rate and time; and conducting fire extinguishing agent concentration simulation analysis to calculate the distribution of fire extinguishing agent concentration in each high-temperature compartment of the aircraft under different conditions of opening different fire extinguishing agent nozzles and different fire extinguishing agent spray volumes.

5. The intelligent fire control method for high-temperature compartments of high-speed aircraft as described in claim 1, characterized in that, A generalized fire model for high-temperature compartments of aircraft is constructed based on the mass conservation equation, energy conservation equation, and heat conservation equation. Specifically: The mass conservation equation can be described as follows: Within a unit time, the net mass flowing into a fluid element is equal to the increase in the element's mass; the expression is: ； In the formula, ρ represents the fluid density; u, v, and w represent the fluid velocities in different directions. t represents time; The energy conservation equation can be described as follows: the rate of increase of energy within a fluid element is equal to the sum of the net heat flow into the element and the work done on the element by the external environment. The expression is: ； In the formula, The average velocity of the fluid; It is a volume force; P x P y P z These are surface forces in the x, y, and z directions; The heat conservation equation is: ； In the formula, C p is the specific heat capacity at constant pressure of the fluid; k is the heat transfer coefficient of the fluid; 𝑆 𝑇 The heat source within the fluid and the increase in heat due to friction caused by viscosity; T is the temperature.

6. The intelligent fire control method based on the high-temperature compartment of a high-speed aircraft as described in claim 1, characterized in that: The CFD simulation calculation uses the RNG k-ε two-equation model. The k-equation and ε-equation in the RNG k-ε model are as follows: ； ； In the formula, , , , , , , , , , , .

7. The intelligent fire control method based on the high-temperature compartment of a high-speed aircraft as described in claim 4, characterized in that: Numerical simulation studies of typical oil mist fires and oil pool fires inside the cabin were conducted using fire dynamics simulation software. The ignition process and flame propagation laws inside the cabin were analyzed, and the velocity field, temperature field and heat flow inside the cabin were obtained. The results were compared and analyzed with experimental results to obtain the optimal fire control strategy.

8. The intelligent fire control method for high-temperature compartments of high-speed aircraft as described in claim 7, characterized in that: The fire dynamics simulation software uses the Clausius-Clapeyron equations for solving the problem, specifically: The evaporation rate is determined by the latent heat of vaporization and the evaporation temperature, as shown in the following equation: ； In the formula, X F,l H represents the concentration of fuel vapor. V For the latent heat of vaporization, W F T is the molar mass of fuel. s For surface temperature, T b This refers to the evaporation temperature. The turbulent combustion model adopts a vortex dissipation model based on the mixing fraction, and the combustion reaction mechanism adopts a single-step reaction, as shown in the following equation: ； mass fraction Y s It is time t and temperature T s The function, with the following expression: ； In the formula, A is the pre-exponential factor, E is the activation energy, and R is a constant; Based on this, the fire control algorithm of the controller is designed, and the optimal fire control strategy is formed according to the fire distribution reconstructed by the controller and the predicted fire development trend.

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