Cloud parameter control method for aircraft engine inlet icing environment simulation test

Abstract

The present invention provides a method for controlling cloud parameters in aircraft engine intake icing environment simulation tests, characterized by the following steps: S1: establishing the effects of spray system water pressure and air pressure on average water droplet diameter; S2: calculating the effects of altitude simulation parameters and wind speed on average water droplet diameter; S3: coupling analysis of liquid water content parameters with intake and exhaust parameters to calculate the required water injection volume; S4: employing a unidirectional air supply system to achieve precise control of the spray system air pressure; and S5: employing a circulating water supply system to achieve stable control of the spray system water pressure. By collaboratively controlling the spray system and the intake and exhaust systems, this method significantly improves the accuracy of icing environment simulation, providing more reliable test conditions for aircraft engine intake icing tests. The method is particularly suitable for simulating cloud fields under complex environmental parameters (such as high wind speed and low air pressure).

Description

Technical Field

[0001] The present invention relates to the technical field of icing environment simulation tests, and in particular to a method for controlling cloud parameters in an aircraft engine intake icing environment simulation test. Background Art

[0002] The engine intake icing test uses a spray system to simulate a foggy environment. The spray system is a key system for constructing water droplets and foggy conditions during the test. Key foggy parameters include liquid water content (LWC) and mean droplet diameter (MVD). These parameters are achieved by the spray system through control of the gas-liquid two-phase nozzle, i.e., by maintaining a constant water and air supply pressure. Furthermore, to achieve precise control of LWC and MVD, coordinated control between the intake and exhaust systems and the spray system is required. Experimental or theoretical analysis of the control characteristics of altitude, foggy, and temperature simulation parameters reveals the coupling relationship between wind speed, altitude, temperature, and foggy conditions.

[0003] In a spray system, the water vapor pressure before the spray rake and the nozzle characteristics determine the cloud particle size and water flow rate at the nozzle outlet. The temperature, humidity, and velocity of the airflow in the intake and exhaust systems are external factors influencing cloud parameters. Temperature, humidity, and velocity affect the evaporation rate of cloud particles during their movement. Airflow velocity also changes the coverage area of ​​the cloud particles reaching the test section. The low internal pressure environment causes the mean droplet diameter (MVD, flow rate, atomization cone angle, etc.) to vary relative to the atmospheric pressure calibration. The initial cloud particle size and droplet temperature affect the evaporation and settling rates of the particles, and are internal factors that influence the final state of the cloud parameters. Summary of the Invention

[0004] In view of this, the present invention provides a method for controlling cloud parameters in an aircraft engine intake icing environment simulation test to solve the problem of coupling between cloud parameters and intake and exhaust parameters during the aircraft engine intake icing test environment simulation process.

[0005] The present invention provides the following technical solution: a method for controlling cloud parameters in an aircraft engine intake icing environment simulation test, characterized in that it includes the following steps: S1: establishing the influence of the water pressure and air pressure of the spray system on the average water droplet diameter; S2: calculating the influence of the height simulation parameter and the wind speed on the average water droplet diameter; S3: coupling analysis of the liquid water content parameter and the intake and exhaust parameters to calculate the required water injection volume; S4: using a one-way air supply system to achieve precise control of the air pressure of the spray system; S5: using a circulating water supply system to achieve stable control of the water pressure of the spray system.

[0006] Compared with the prior art, the beneficial effects achieved by at least one of the above-mentioned technical solutions adopted in the present invention include at least the following: this method significantly improves the accuracy of icing environment simulation by collaboratively controlling the spray system and the intake and exhaust system, providing more reliable test conditions for aircraft engine intake icing tests, and is particularly suitable for simulating cloud and fog fields under complex environmental parameters (such as high wind speed and low air pressure). BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0008] Figure 1 is a schematic diagram of a flow chart of an embodiment of the present invention;

[0009] Figure 2 It is a schematic diagram of the spray rake water pressure control process. DETAILED DESCRIPTION

[0010] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0011] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0012] like Figures 1 to 2 As shown, the present invention provides a method for controlling cloud parameters in an aircraft engine intake icing environment simulation test, the method comprising the following steps:

[0013] S1: Effect of spray water pressure on MVD

[0014] From the relationship diagram between MVD and the spray system water pressure Pw and air pressure Pa, it can be concluded that both nozzle water and air pressures affect MVD. When the air pressure remains constant, increasing the nozzle water pressure will increase the nozzle's atomization performance MVD; when the water pressure remains constant, increasing the nozzle air pressure will decrease MVD. Therefore, the following relationship exists:

[0015] ;

[0016] According to the test results of spray particle size, the following fitting formula can be used:

[0017] ;

[0018] Where x is the water pressure in the spray system, and the air pressure is a constant value during a single test. Coefficients such as a, b, c, d, and e are obtained by fitting test results under different operating conditions.

[0019] S2: Effects of height simulation parameters and wind speed on MVD;

[0020] Height simulation primarily involves changes in air pressure, temperature, and air density, all of which affect spray droplets. When there is a lateral air flow velocity u, the MVD of the spray droplets is affected not only by the simulated height H but also by the wind speed u, which influences the movement and evaporation of the droplets.

[0021] The relationship between MVD, simulation height H, incoming flow velocity u and incoming flow temperature when considering the lateral wind speed u.

[0022] a) Influence of height H

[0023] Changes in air pressure and air density: As the simulation height H increases, the air pressure and air density decrease. The decrease in air pressure and air density increases the evaporation rate of droplets and reduces the diameter of droplets.

[0024] b) Influence of incoming flow velocity u

[0025] The transverse wind speed u affects the trajectory of the droplet. The terminal velocity of the droplet and the wind speed u together determine the path of the droplet drifting in the wind; higher wind speeds may cause the droplet to break or deform in the wind, which will also affect the droplet's MVD.

[0026] Terminal velocity of a droplet moving naturally in an altitude platform It can be expressed as:

[0027] ;

[0028] Where, is the air density, is the liquid density, D is the droplet diameter, g is the weight acceleration, C d It is the drag coefficient related to the Reynolds number. The terminal velocity affects the motion state and residence time of the droplets, thereby indirectly affecting the evaporation rate. Among them, the air density Variation with altitude:

[0029] ;

[0030] Where e is a natural constant, R is a gas constant, and altitude H affects air pressure and density, thus affecting the droplet's evaporation rate. T is the temperature. Changes in air pressure and density cause fluctuations in the evaporation rate. Typically, the MVD of a droplet decreases with increasing altitude, and this change can be expressed using an exponential function:

[0031] ;

[0032] Among them, k1 is the fitting coefficient that needs to be determined through experiments, which represents the specific effect of altitude on MVD under different environmental conditions.

[0033] If there is air with an incoming flow velocity u, the drift of droplets needs to be considered due to the wind speed effect. However, in general, the wind speed effect of droplets indirectly affects MVD by changing the droplet trajectory and evaporation rate. The evaporation rate E can be expressed as:

[0034] ;

[0035] Where A is the surface area of ​​the droplet, k e is a constant related to the evaporation rate, P s is the saturated vapor pressure of the droplet. f(u) is a correction factor related to the wind speed u, which represents the effect of wind speed on the evaporation rate and can usually be approximated as a linear function:

[0036] ;

[0037] Among them, k u is the coefficient of wind speed on evaporation rate.

[0038] So we have:

[0039] ;

[0040] Wind speed u affects MVD by affecting the evaporation rate. Increased wind speed accelerates evaporation, thereby reducing MVD. This effect can be expressed as a correction factor:

[0041] ;

[0042] The correction factor is explained as follows:

[0043] Numerator 1 + k u u represents the enhancement effect of wind speed on evaporation rate. An increase in wind speed will increase the evaporation rate, thereby reducing MVD. , here is the ratio of the evaporation rate to the terminal velocity, and k² is the correction factor. This section considers the relationship between the evaporation rate and the droplet terminal velocity. A higher evaporation rate and a lower terminal velocity result in a smaller MVD because the droplet's residence time is shorter and evaporation is faster. Therefore, by comprehensively considering the effects of height H and wind speed u, the change in MVD can be derived. Assuming that MVD is the particle size under baseline conditions, the change in MVD under the influence of height H and wind speed u can be expressed as:

[0044] ;

[0045] Each part of this expression reflects a different aspect of the droplet behavior in real situations: the effect of height is expressed through the exponential function The effects of wind speed and evaporation rate are taken into account through correction factors to comprehensively consider the effects of wind speed and terminal velocity on droplet diameter.

[0046] The final expression is obtained by combining the theoretical model with experimental data. In practical applications, MVD, k1, k2 and k can be determined by experimental fitting. u Parameters such as the model can accurately reflect the spray droplet behavior under specific conditions.

[0047] S3: Coupling analysis of LWC parameters and intake and exhaust parameters

[0048] Temperature, altitude, and inflow velocity all have an impact on cloud parameters. Among them, the impact of temperature is more obvious. When the ambient temperature is below -25℃, the evaporation effect can be ignored. Altitude mainly affects the ambient pressure. Inflow velocity mainly affects the evaporation rate. The greater the speed, the greater the amount of evaporation, but the proportion of evaporation decreases.

[0049] LWC is a relatively macroscopic and overall quantity. It is not necessary to study the droplet particles themselves, but only to focus on the mass of liquid water contained in a unit space. It can be calculated and analyzed by borrowing concepts such as atmospheric moisture content and relative humidity. LWC can be calculated based on Get.

[0050] Air saturation vapor pressure The relationship with temperature T is as follows:

[0051] ;

[0052] Where T is the temperature in °C; saturated vapor pressure , unit is kPa.

[0053] Atmospheric moisture content d represents the ratio of water vapor mass to dry air mass. It has the following relationship with saturated vapor pressure, atmospheric relative humidity RH and atmospheric pressure P:

[0054] ;

[0055] Based on this, calculate the mass flow rate of liquid water to be injected for:

[0056] ;

[0057] Among them, the physical meaning of ϕ is: water mass flow rate (including liquid water and gaseous water) and air mass flow The ratio is recorded as:

[0058] ;

[0059] Air mass flow It is the engine inlet parameter and can be measured and calculated by sensors. It contains two parts: one is the water content in the test section space, and the other is the water content of the accompanying flow air loss. Now consider the parameter coupling under the steady-state spray state. Assuming that the test space volume is V, the cross-sectional area of ​​the test section is S, and the spray time is t, according to the above parameter definitions, we can get

[0060] ;

[0061] in, is the absolute humidity, which represents the gaseous water content: It contains two parts: liquid water and gaseous water. LWC is the liquid water content, which is multiplied by the volume V to get the mass of liquid water; similarly, multiplied by the volume V to get the mass of gaseous water. The sum of these two parts is the mass of all water, divided by the spray time t, to get the mass flow rate In summary, the ratio of water mass flow rate to air mass flow rate, φ, can be calculated using the following formula:

[0062] ;

[0063] All parameters in this formula can be measured directly or indirectly, including absolute humidity A hygrometer is required to directly measure relative humidity (RH). Measuring LWC at high altitudes is more complex and can be performed using methods such as scattering particle probing (FSSP), optical array probing (OAP), hot wire probing, and ultrasonic probing. Alternatively, the most commonly used ice skate method can be used. This involves placing an ice skate in an icing wind tunnel and analyzing the mass of ice on the skate to calculate LWC.

[0064] Through the above analysis, LWC, intake and exhaust parameters and theoretical water injection volume can be intuitively characterized. The coupling relationship between them is as follows:

[0065] ;

[0066] Among them, b = V / t, which is related to the size of the test section and is a constant.

[0067] S4: Spray system air pressure control method

[0068] The air supply system of the spray system adopts one-way air supply and traditional PID control, and realizes precise control of air supply pressure through multi-stage regulating valve.

[0069] S5: Spray system water pressure control method

[0070] The spray system's air supply utilizes a circulating water supply, with multiple spray rakes sharing a common water supply main. A specific operating pressure can be achieved by varying the pump flow rate and the inlet and outlet control valve openings. However, adjusting these three parameters simultaneously can interfere with each other, resulting in severe coupling issues and making it difficult to precisely control the pressures of each branch. To minimize the need for simultaneous adjustment of multiple variables and mitigate coupling issues between branches, a design process for spray rake water pressure control was developed.

[0071] The overall control process is as follows: In the main water supply line, the pump speed is pre-set to control the main water flow rate. In the multiple parallel branches, the inlet regulating valves are preset to a fixed opening, throttling and reducing pressure in each branch, while also isolating the branches from each other to a certain extent. To reduce pressure fluctuations within the branches, the outlet regulating valves are also pre-set to a certain opening. This opening parameter is obtained through multiple experiments and is an empirical value. The opening is then fine-tuned using a closed-loop control algorithm to achieve precise pressure control in each branch. During the spray test, the inlet regulating valve opening of each spray rake remains unchanged at the moment the solenoid valve opens. After spraying, the outlet regulating valve opening is adjusted through closed-loop control based on pressure fluctuations caused by the nozzle water flow, achieving precise pressure control during the spray test. This solution of pre-determining the pump speed and pre-setting the inlet regulating valve opening effectively addresses the mutual interference problem in the multivariable joint control process. The closed-loop control algorithm is the core design principle. Based on the analysis of coupling, a control strategy based on feedforward decoupling is adopted.

[0072] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for controlling cloud parameters in an aircraft engine intake icing environment simulation test, characterized in that: The following steps are involved: S1: Establish the influence of water pressure and air pressure of the spray system on the average droplet diameter; the air pressure in a single test is set to a constant value, and according to the fitting formula Calculate the average droplet diameter, where x is the water pressure in the spray system and a, b, c, d, and e are coefficients; S2: According to the formula , calculate the influence of height simulation parameters and wind speed on the average water droplet diameter, where, is the effect of the height simulation parameter H and wind speed u on the average droplet diameter, e is a natural constant, k1 is a fitting coefficient determined by experiment, is the ratio of evaporation rate to terminal velocity, k2 is the correction factor, k u is the coefficient of wind speed’s effect on evaporation rate; S3: Couple analysis of liquid water content parameters and intake and exhaust parameters is performed according to the formula Calculate the required water volume, where LWC is the liquid water content and RH is the relative humidity. is the saturated vapor pressure of air, is the absolute humidity, is the air mass flow rate, is the water spray volume, P is the atmospheric pressure, S is the cross-sectional area of ​​the test section, b is a constant value, is the air flow rate; S4: Use one-way air supply system to achieve precise control of spray system air pressure; S5: Use a circulating water supply system to achieve stable control of the water pressure in the spray system.

2. The method for controlling cloud parameters in an aircraft engine intake icing environment simulation test according to claim 1, characterized in that: Methods for measuring liquid water content parameters include scattered particle spectrum detection, optical array detection, hot wire method, ultrasonic method or ice knife method.

3. The method for controlling cloud parameters in an aircraft engine intake icing environment simulation test according to claim 1, characterized in that: S4 specifically adopts a one-way air supply system and realizes precise control of the spray system air pressure through PID control combined with a multi-stage regulating valve.

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