Method and system for adaptive adjustment of ambient wind speed for flame engulfment test chamber

Abstract

This invention belongs to the field of industrial automation control technology, specifically relating to an adaptive wind speed adjustment method and system for a flame incineration test chamber. The method includes the following steps: S1, collecting multidimensional thermal data of the test area and the current ambient wind speed, and extracting the temperature change rate, heat flux change rate, and wind speed change rate using a sliding window algorithm; S2, constructing a thermal response sensitivity index based on the temperature change rate, heat flux change rate, and wind speed change rate at the lag time, and determining the current combustion mode by the positive or negative sign of the thermal response sensitivity index. This invention can identify the combustion mode in real time and adaptively adjust the control damping, effectively solving the control inversion problem and ensuring control stability throughout the entire life cycle.

Description

Technical Field

[0001] This invention belongs to the field of industrial automation control technology, specifically relating to an adaptive wind speed adjustment method and system for a flame engulfment test chamber. Background Technology

[0002] In standard tests such as API 607 ​​or ISO 10497, ambient wind speed is a key source of interference affecting the stability of flame temperature and heat flux. These tests typically require maintaining an extremely high temperature environment for a specific period of time to test the fire resistance of equipment. However, the combustion process in the test chamber is an extremely complex physicochemical reaction process, influenced by multiple factors including airflow, oxygen concentration, and ambient thermal radiation.

[0003] Current technologies for controlling ambient wind speed typically employ PID control algorithms with fixed parameters. This traditional control method has significant limitations when facing complex combustion environments. Specifically, the effect of wind speed on temperature exhibits a significant non-monotonicity: in the early stages of combustion or in areas with localized oxygen deficiency, increasing wind speed replenishes oxygen, thus aiding combustion and raising the temperature, resulting in a positive gain; however, in oxygen-rich areas or when wind speed is excessive, increasing wind speed actually removes heat, leading to cooling, resulting in a negative gain. Traditional PID controllers cannot detect this sudden reversal of physical properties, easily leading to logical errors at critical points. This causes the system to oscillate repeatedly between heating and cooling, making it impossible to maintain stable experimental conditions.

[0004] Furthermore, as the experiment continues, the physical environment of the laboratory undergoes significant changes. The laboratory walls, fixtures, and other infrastructure gradually absorb heat until they reach saturation, leading to a decrease in the environment's heat dissipation capacity—that is, a change in the system's thermal damping. Existing algorithms cannot adapt to this cumulative "environmental variation" over time. In the later stages of the experiment, the same wind speed adjustment will produce much larger temperature fluctuations than in the initial stages. This thermal saturation effect results in a significant decrease in control accuracy in the later stages of the experiment, often causing experimental data to fail to meet standard requirements, resulting in costly waste of experimental resources. Summary of the Invention

[0005] This invention provides an adaptive wind speed control method and system for a flame engulfment test chamber, which solves the technical problems of existing fixed-parameter PID control being unable to adapt to the non-monotonic effects of wind speed and environmental variations, resulting in system oscillation, decreased accuracy, substandard data, and cost waste.

[0006] In a first aspect, the present invention provides an adaptive method for adjusting the ambient wind speed in a flame inhalation test chamber, comprising the following steps: S1: Collect multidimensional thermal data of the test area and the current ambient wind speed, and use the sliding window algorithm to extract the rate of temperature change, the rate of heat flux change, and the rate of wind speed change. S2, based on the rate of temperature change, the rate of heat flux change, and the rate of wind speed change at the lag time, constructs a thermal response sensitivity index, and determines the current combustion mode by the positive or negative sign of the thermal response sensitivity index; S3, collect the background ambient temperature of the laboratory, construct the environmental heat saturation coefficient based on the background ambient temperature, and use the environmental heat saturation coefficient to characterize the cumulative state of environmental thermal damping during the test. S4, based on the thermal response sensitivity index and the environmental thermal saturation coefficient, uses a variable structure gain algorithm to calculate the wind speed adjustment command increment at the next moment, and adaptively adjusts the environmental wind speed according to the wind speed adjustment command increment, thereby achieving precise control of the flame engulfment test environment.

[0007] Furthermore, the sliding window algorithm is used to extract the rates of temperature change, heat flux change, and wind speed change, specifically including: Set the time window length, and for the current moment, select the original data within the historical interval corresponding to the time window length; Linear regression is performed on the original data within the historical interval, and the slope of the fitted line is used as the rate of change of the corresponding physical quantity. The rates of change of temperature, heat flux, and wind speed were obtained respectively.

[0008] Furthermore, the formula for calculating the thermal response sensitivity index is as follows:

[0009] In the formula, This refers to the thermal response sensitivity index. For the rate of temperature change, The rate of change of heat flux. This is the heat flux weighting coefficient. The rate of change of wind speed before the lag time. is the numerical stability constant.

[0010] Furthermore, the process of obtaining the wind speed change rate before the lag time includes: Establish a first-in-first-out buffer queue to store wind speed change data within a preset lag time in the past; Historical data is retrieved from the head of the cache queue during calculation to align past wind speed changes with current temperature changes; A positive thermal response sensitivity index indicates that the region is in an oxygen-deficient combustion zone, while a negative index indicates that the region is in an oxygen-rich cooling zone.

[0011] Furthermore, the formula for calculating the environmental heat saturation coefficient is as follows:

[0012] In the formula, The environmental heat saturation coefficient, This represents the current background temperature in the laboratory. The initial ambient temperature before ignition. For the normalized reference temperature, As the saturation influence factor, It is the natural logarithm function.

[0013] Furthermore, the environmental thermal saturation coefficient increases monotonically with test time and is used as a damping term for the controller; the initial environmental temperature is recorded and locked at the moment the system starts.

[0014] Furthermore, the formula for calculating the increment of the wind speed adjustment command at the next moment is:

[0015] In the formula, This represents the increment of the wind speed adjustment command that needs to be adjusted in the current control cycle. To the maximum allowable adjustment step size, Let be a sign function of the thermal response sensitivity index. This is the absolute value of the thermal response sensitivity index. The environmental heat saturation coefficient, For the natural constant An exponential function with base 0.

[0016] Furthermore, the logic of the symbolic function is as follows: If the thermal response sensitivity index is greater than zero, return to a positive value to execute the air supply operation; If the thermal response sensitivity index is less than zero, return a negative value to perform a reduced airflow operation; The denominator in the formula is always greater than or equal to 1. As the environmental heat saturation coefficient increases, the increment of the wind speed adjustment command decreases.

[0017] Furthermore, the adaptive adjustment of ambient wind speed based on the incremental wind speed adjustment command specifically includes: Add the current wind speed value to the increment of the wind speed adjustment command to obtain the target wind speed for the next moment; The target wind speed is sent to the wind turbine frequency converter to adjust the ambient wind speed.

[0018] Secondly, the present invention provides an environmental wind speed adaptive adjustment system for a flame engulfment test chamber, including a memory and a processor. The memory stores computer program instructions, and when the computer program instructions are executed by the processor, the above-mentioned environmental wind speed adaptive adjustment method for a flame engulfment test chamber is implemented.

[0019] The beneficial effects are: 1. It fundamentally solves the problem of control reversal. By constructing a thermal response sensitivity index, the system can identify the direction of the current wind speed's influence on temperature in real time, just like an experienced engineer, i.e., determine whether it is for combustion support or cooling. This completely eliminates the oscillation risk caused by logical confusion at the combustion inflection point in traditional PID control, ensuring logical correctness under complex flow fields.

[0020] 2. Robust control throughout the entire lifecycle is achieved by innovatively introducing an environmental heat saturation coefficient and using a logarithmic function to accurately characterize the nonlinear growth of the laboratory environment's thermal inertia. By using this coefficient as a dynamic damping term in the control algorithm, the system can automatically adapt to environmental changes during the experiment, ensuring consistent control accuracy from the cold state at the start of the experiment to the heat saturation state at the end, effectively avoiding the risk of temperature runaway in the later stages. Attached Figure Description

[0021] Figure 1 This is a flowchart of the adaptive adjustment method for environmental wind speed in the flame engulfment test chamber of the present invention.

[0022] Figure 2 This is a comparison chart of temperature stability during the flame engulfment test process in this invention.

[0023] Figure 3 This is a comparison diagram of the wind speed regulation logic response of the control system in this invention. Detailed Implementation

[0024] 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, not all, of the embodiments of the present invention. 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.

[0025] An embodiment of the adaptive wind speed adjustment method for a flame engulfment test chamber provided by the present invention: like Figure 1 As shown, the adaptive wind speed adjustment method for a flame inhalation test chamber includes the following steps: S1 collects multidimensional thermal data of the test area and the current ambient wind speed, and uses a sliding window algorithm to extract the rate of temperature change, the rate of heat flux change, and the rate of wind speed change.

[0026] In the specific implementation process, the system uses a high-speed data acquisition card at a frequency Real-time acquisition of raw signals, including the average temperature measured by multiple thermocouples in the test area. Real-time heat flux measured by heat flux meter And the frequency feedback value of the wind turbine inverter at the current moment. .

[0027] Because flame combustion produces high-frequency flicker noise, directly using the raw data can lead to controller malfunctions. This step avoids using low-pass filtering, which introduces phase shift, and instead employs a sliding window least squares method to extract the rate of change. A time window length is set. For example, 30 sampling points, for the current time Select For data within a given interval, perform linear regression fitting; the slope of the straight line represents the rate of change of that physical quantity.

[0028] For example, if the sampling frequency is 10Hz and the window length is 30, then the data from the past 3 seconds is used for fitting; the following variables are finally obtained: Rate of temperature change , in units of ℃ / s, represents the current trend of heat energy rise and fall; rate of change of heat flux The unit is kW / m² / s. Since radiation transfer is faster than convection, this variable is used as an indicator for advance prediction. Wind speed change rate , in units of m / s², characterizes the intensity of action of the control system.

[0029] By extracting trends using a sliding window algorithm, the transient change direction of temperature and heat flux can be accurately captured while filtering out high-frequency combustion noise, providing dynamic data support without phase lag for subsequent judgment of the impact of wind speed on combustion.

[0030] S2, based on the rate of temperature change, the rate of heat flux change, and the rate of wind speed change at the lag time, constructs a thermal response sensitivity index, and determines the current combustion mode by the positive or negative sign of the thermal response sensitivity index.

[0031] In practical implementation, to resolve the ambiguity of whether the system supports combustion or cools, the system needs to calculate the comprehensive thermal energy response caused by a unit change in wind speed. This is equivalent to detecting the sensitivity of the current combustion chemical reaction to oxygen. A thermal response sensitivity index is then constructed. The formula is as follows:

[0032] In the formula, This is the thermal response sensitivity index. A positive value indicates that the area is in an oxygen-deficient combustion zone, while a negative value indicates that the area is in an oxygen-rich cooling zone. and It is calculated from step S1. This is a heat flux weighting coefficient, for example, 0.5, used to convert the rate of change of heat flux into an equivalent rate of change of temperature, balancing the dimensions, and using the leading nature of heat flux to compensate for temperature lag. for The rate of change of wind speed before the specified time.

[0033] Get The process is as follows: The system establishes a FIFO buffer queue to store past data. Wind speed changes over a period of seconds (e.g., 5 seconds) are calculated by retrieving historical data from the head of the queue. This is done to align past wind speed changes with current temperature changes. This is a numerical stability constant, for example, 0.01. To prevent the formula from becoming invalid due to a zero denominator, when... At that time, among them For a small threshold, the system is forced to maintain the value from the previous time step. The value is not updated, or it is directly set to [value]. To avoid logical errors.

[0034] Calculation example: Suppose that at the current moment, the temperature is rising rapidly. At ℃ / s, the heat flux is also increasing. kW / m² / s, weight ; Molecular part = .

[0035] Assuming 5 seconds ago (i.e.) The system executed an operation to increase wind speed; the rate of change of wind speed... m / s², ; denominator part = ;but .

[0036] A positive result indicates that the increased airflow 5 seconds ago led to the current temperature rise, meaning the airflow promoted combustion. The system determines that the system is currently in an oxygen-deficient combustion zone and needs to continue increasing airflow or maintain the airflow speed. Conversely, if airflow was increased 5 seconds ago but the temperature has now decreased, the result will be negative, indicating that the excessive airflow had a cooling effect.

[0037] By constructing a thermal response sensitivity index, the system can determine the causal relationship between wind speed and temperature in real time and accurately identify the current combustion mode, thereby avoiding the control direction error that occurs when the combustion characteristics of traditional PID are reversed.

[0038] S3: Collect the background ambient temperature of the laboratory, construct the environmental heat saturation coefficient based on the background ambient temperature, and use the environmental heat saturation coefficient to characterize the cumulative state of environmental thermal damping during the test.

[0039] In the specific implementation process, the environment is relatively cold in the early stage of the experiment, resulting in rapid heat dissipation and requiring sensitive control response. In the later stage of the experiment, the environment absorbs heat to saturation, and thermal inertia increases, so the same wind speed adjustment will produce different thermal effects. If the control parameters remain unchanged, overshoot is very likely to occur in the later stage. This step introduces the environmental heat saturation to evaluate this physical process. An environmental heat saturation coefficient is constructed. The formula is as follows:

[0040] In the formula, The environmental thermal saturation coefficient is a dimensionless value that increases monotonically with test time and is used as the damping term of the controller. The current background temperature of the laboratory is collected in real time by auxiliary thermocouples placed on the walls or ceiling of the laboratory away from the center of the flame. The initial ambient temperature before ignition, such as 25°C, is recorded and locked at the moment the system starts. A normalized reference temperature, such as 100°C, is used to eliminate the influence of the numerical magnitude of the temperature. The saturation influence factor is, for example, 1.5. It is the natural logarithm function.

[0041] Calculation example: Assuming the experiment has just begun, ℃, ℃, ℃, ; but At this point, there is no damping, and the control is most sensitive.

[0042] Assuming the experiment progresses to the later stages, the wall temperature rises to... ℃; .

[0043] The coefficient increases significantly at this point, indicating that the environmental heat saturation is high and a large damping effect needs to be applied to the control quantity.

[0044] By incorporating the changes in thermal inertia of the laboratory into the control logic through the environmental thermal saturation coefficient, the system can perceive the physical evolution of the environment over time, providing key environmental state parameters for subsequent adaptive adjustment.

[0045] S4, based on the thermal response sensitivity index and the environmental thermal saturation coefficient, uses a variable structure gain algorithm to calculate the wind speed adjustment command increment at the next moment, and adaptively adjusts the environmental wind speed according to the wind speed adjustment command increment, thereby achieving precise control of the flame engulfment test environment.

[0046] In the specific implementation process, the system is based on Determine the adjustment direction and utilize Apply damping. The control strategy employs "S-shaped variable structure control": when... When the gain is large, high gain is quickly adjusted; when... Over the course of hours, the gain automatically decays exponentially, achieving a smooth transition and remaining constant throughout. The damping is greater the hotter the environment.

[0047] Calculate the wind speed adjustment command increment for the next moment. :

[0048] In the formula, This represents the increment of the wind speed adjustment command that needs to be adjusted in the current control cycle. To determine the maximum allowable adjustment step size, such as 2Hz, a physical upper limit is set for the single adjustment. For symbolic functions: if Return +1 and execute the air supply increase; if Returns -1, and executes wind reduction. This is the absolute value of the thermal response sensitivity index, representing the degree of deviation from the optimal combustion point. As the denominator term, the physical mechanism is: as the experiment proceeds, As the denominator increases, the exponent approaches zero more slowly, resulting in a smaller overall value within the parentheses.

[0049] The final target wind speed is achieved through the following method: .

[0050] Calculation example: Scenario 1: Initial stage of the experiment ( Unstable combustion ( ),set up Hz; ; The result was close to the maximum step size, and the system rapidly increased airflow.

[0051] Scenario 2: Later stage of the experiment ( Combustion is also unstable. ); ; As can be seen, the adjustment amount is reduced under the same sensitivity to prevent overshoot in overheated environments.

[0052] Scenario 3: In the later stages of the experiment, combustion approaches equilibrium. ); ; At this point, the adjustment amount is very small, achieving fine adjustment.

[0053] Reference Figure 2 The curves of existing technologies show continuous oscillations in the later stages of the experiment, while the curves of the present invention always closely follow the target value.

[0054] Reference Figure 3 The wind speed regulation curve of the present invention presents a smooth S-shape, avoiding the chaotic fluctuations of the prior art.

[0055] By combining a variable structure gain algorithm with the environmental thermal saturation coefficient, the system not only ensures the correctness of the adjustment direction but also automatically adjusts the adjustment intensity according to the experimental stage. It exhibits rapid response in the early stages of the experiment and robust fine-tuning in the later stages, effectively preventing control divergence caused by environmental thermal saturation and achieving high-precision adaptive control.

[0056] An embodiment of the environmental wind speed adaptive adjustment system for a flame engulfment test chamber provided by the present invention: The environmental wind speed adaptive adjustment system for a flame engulfment test chamber includes a processor and a memory. The memory stores computer program instructions, which, when executed by the processor, implement the aforementioned environmental wind speed adaptive adjustment method for a flame engulfment test chamber.

[0057] The environmental wind speed adaptive adjustment system for the flame inhalation test chamber also includes other components well known to those skilled in the art, such as communication interfaces, the settings and functions of which are known in the art and will not be described in detail here.

[0058] In this invention, the aforementioned memory can be any tangible medium containing or storing a program that can be used or combined with an instruction execution system, apparatus, or device. For example, a computer-readable storage medium can be any suitable magnetic or magneto-optical storage medium, such as Resistive Random Access Memory (RRAM), Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), Enhanced Dynamic Random Access Memory (EDRAM), High-Bandwidth Memory (HBM), Hybrid Memory Cube (HMC), etc., or any other medium that can be used to store desired information and can be accessed by an application, module, or both. Any such computer storage medium can be part of a device or accessible to or connected to a device. Any application or module described in this invention can be implemented using computer-readable / executable instructions stored or otherwise maintained by such a computer-readable medium.

[0059] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for adaptive adjustment of the ambient wind speed in a flame uptake test chamber, characterized in that Includes the following steps: S1: Collect multidimensional thermal data of the test area and the current ambient wind speed, and use the sliding window algorithm to extract the rate of temperature change, the rate of heat flux change, and the rate of wind speed change. S2, based on the rate of temperature change, the rate of heat flux change, and the rate of wind speed change at the lag time, constructs a thermal response sensitivity index, and determines the current combustion mode by the positive or negative sign of the thermal response sensitivity index; S3, collect the background ambient temperature of the laboratory, construct the environmental heat saturation coefficient based on the background ambient temperature, and use the environmental heat saturation coefficient to characterize the cumulative state of environmental thermal damping during the test. S4, based on the thermal response sensitivity index and the environmental thermal saturation coefficient, uses a variable structure gain algorithm to calculate the wind speed adjustment command increment at the next moment, and adaptively adjusts the environmental wind speed according to the wind speed adjustment command increment, thereby achieving precise control of the flame engulfment test environment.

2. The adaptive wind speed adjustment method for a flame inhalation test chamber according to claim 1, characterized in that, The sliding window algorithm is used to extract the rates of temperature change, heat flux change, and wind speed change, specifically including: Set the time window length, and for the current moment, select the original data within the historical interval corresponding to the time window length; Linear regression is performed on the original data within the historical interval, and the slope of the fitted line is used as the rate of change of the corresponding physical quantity. The rates of change of temperature, heat flux, and wind speed were obtained respectively.

3. The adaptive wind speed adjustment method for a flame inhalation test chamber according to claim 1, characterized in that, The formula for calculating the thermal response sensitivity index is as follows: In the formula, This refers to the thermal response sensitivity index. For the rate of temperature change, The rate of change of heat flux, This is the heat flux weighting coefficient. The rate of change of wind speed before the lag time. is the numerical stability constant.

4. The adaptive wind speed adjustment method for a flame engulfment test chamber according to claim 3, characterized in that, The process of obtaining the rate of change of wind speed before the lag time includes: Establish a first-in-first-out buffer queue to store wind speed change data within a preset lag time in the past; Historical data is retrieved from the head of the cache queue during calculation to align past wind speed changes with current temperature changes; A positive thermal response sensitivity index indicates that the region is in an oxygen-deficient combustion zone, while a negative index indicates that the region is in an oxygen-rich cooling zone.

5. The adaptive wind speed adjustment method for a flame inhalation test chamber according to claim 1, characterized in that, The formula for calculating the environmental heat saturation coefficient is as follows: In the formula, The environmental heat saturation coefficient, This represents the current background temperature in the laboratory. The initial ambient temperature before ignition. For the normalized reference temperature, As the saturation influence factor, It is the natural logarithm function.

6. The adaptive wind speed adjustment method for a flame inhalation test chamber according to claim 5, characterized in that, The environmental thermal saturation coefficient increases monotonically with test time and is used as a damping term for the controller; the initial ambient temperature is recorded and locked at the moment the system starts.

7. The adaptive wind speed adjustment method for a flame engulfment test chamber according to claim 1, characterized in that, The formula for calculating the increment of the wind speed adjustment command at the next moment is: In the formula, This represents the increment of the wind speed adjustment command that needs to be adjusted in the current control cycle. To the maximum allowable adjustment step size, Let be a sign function of the thermal response sensitivity index. This is the absolute value of the thermal response sensitivity index. The environmental heat saturation coefficient, For the natural constant An exponential function with base 0.

8. The adaptive wind speed adjustment method for a flame engulfment test chamber according to claim 7, characterized in that, The logic of the symbolic function is as follows: If the thermal response sensitivity index is greater than zero, return to a positive value to execute the air supply operation; If the thermal response sensitivity index is less than zero, return a negative value to perform a reduced airflow operation; The denominator in the formula is always greater than or equal to 1. As the environmental heat saturation coefficient increases, the increment of the wind speed adjustment command decreases.

9. The adaptive wind speed adjustment method for a flame engulfment test chamber according to claim 7, characterized in that, Adaptive adjustment of ambient wind speed based on wind speed adjustment command increments specifically includes: Add the current wind speed value to the increment of the wind speed adjustment command to obtain the target wind speed for the next moment; The target wind speed is sent to the wind turbine frequency converter to adjust the ambient wind speed.

10. An adaptive wind speed control system for a flame inhalation test chamber, characterized in that, It includes a memory and a processor, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the method for adaptive adjustment of environmental wind speed for a flame engulfment test chamber as described in any one of claims 1-9 is implemented.

Images