Aero-engine air inlet icing environment simulation test cloud and mist parameter control method

Abstract

The invention provides an aero-engine air inlet icing environment simulation test cloud and mist parameter control method, which is characterized by comprising the following steps: S1, establishing the influence of water pressure and air pressure of a spraying system on the average water drop diameter; s2, calculating the influence of the height simulation parameter and the wind speed on the average water drop diameter; s3, carrying out coupling analysis on the liquid water content parameter and the intake and exhaust parameters, and calculating the amount of water to be sprayed; s4, a one-way air supply system is adopted to achieve accurate control over the air pressure of the spraying system; s5, stable control over the water pressure of the spraying system is achieved through a circulating water supply system. According to the method, through cooperative control of the spraying system and the air intake and exhaust system, the precision of icing environment simulation is remarkably improved, more reliable test conditions are provided for an aero-engine air intake icing test, and the method is particularly suitable for cloud field simulation 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 particularly to a method for controlling cloud parameters in an icing environment simulation test of an aero-engine intake. Background Art

[0002] In the engine intake icing test, a spray system is used to simulate the cloud environment. The spray system is a key system for constructing water droplets and cloud states in the test. Important parameters of the cloud environment include liquid water content (LWC), mean volume diameter (MVD), etc. These parameters are all achieved by the spray system through controlling the gas-liquid two-phase nozzle, that is, by controlling a certain water supply and gas supply pressure. In addition, in order to achieve precise control of LWC and MVD, it is necessary to realize the coordinated control between the intake and exhaust system and the spray system, and reveal the coupling relationship existing among wind speed, altitude, temperature and cloud by highly simulating parameter control characteristics of altitude simulation parameters, cloud field simulation parameters and temperature field simulation parameters through experiments or theoretical analysis.

[0003] In the spray system, the water-vapor pressure in front of the spray rake and the nozzle characteristics determine the particle size and water flow rate of the cloud particles at the nozzle outlet. The temperature, humidity and velocity of the air flow in the intake and exhaust system are external factors affecting the cloud parameters. Among them, temperature, humidity and velocity affect the evaporation rate of cloud particles during movement. At the same time, the velocity of the air flow will also cause a change in the coverage area of the cloud particles reaching the test section, and the internal low-pressure environment will cause a change in the mean volume diameter (MVD, flow rate, atomization cone angle, etc.) relative to the calibration under normal pressure. The initial particle size of the cloud particles, water droplet temperature, etc. will affect the evaporation and sedimentation rates of the particles, and are internal factors affecting 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 icing environment simulation test of an aero-engine intake to solve the problem of coupling between cloud parameters and intake and exhaust parameters during the simulation of the icing test environment of an aero-engine intake.

[0005] The present invention provides the following technical solutions: A method for controlling cloud parameters in an icing environment simulation test of an aero-engine intake, characterized by comprising the following steps: S1: Establish the influence of the water pressure and gas pressure of the spray system on the mean volume diameter; S2: Calculate the influence of altitude simulation parameters and wind speed on the mean volume diameter; S3: Conduct a coupling analysis on the liquid water content parameters and intake and exhaust parameters, and calculate the required water injection volume; S4: Use a one-way gas supply system to achieve precise control of the gas pressure of the spray system; S5: Use 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 that can be achieved by at least one of the above technical solutions adopted in the present invention at least include: By coordinately controlling the spray system and the intake and exhaust systems, the accuracy of ice formation environment simulation is significantly improved, providing more reliable test conditions for the intake ice formation test of aero-engines, and is particularly suitable for the simulation of cloud 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 drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0008] Figure 1 is a schematic flowchart of an embodiment of the present invention; Figure 2 is a schematic flowchart of the water pressure control of the spray rake. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0009] The embodiments of the present application will be described in detail below with reference to the drawings.

[0010] The following specific examples illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content 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 implementation manners, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present application belong to the scope of protection of the present application.

[0011] As Figures 1 to 2 shown, the present invention provides a method for controlling cloud parameters in an intake ice formation environment simulation test of an aero-engine, and the method includes the following steps: S1: Influence of spray water pressure and air pressure on MVD From the relationship diagram of MVD with the water pressure Pw and air pressure Pa of the spray system, it can be concluded that both the water pressure and air pressure of the nozzle will affect MVD. When the air pressure remains unchanged, increasing the water pressure of the nozzle will increase the atomization performance MVD of the nozzle; when the water pressure remains unchanged, increasing the air pressure of the nozzle will decrease MVD. Therefore, the following relational expressions exist: ; According to the spray particle size test results, the following fitting formula can be used: ; where x is the water pressure of the spray system, and the air pressure is a constant value in a single test. The coefficients such as a, b, c, d, and e are obtained by fitting according to the test results under different working conditions.

[0012] S2: Influence of height simulation parameters and wind speed on MVD; Height simulation mainly involves changes in air pressure, temperature, and air density, all of which affect spray droplets. When there is air with a cross-flow velocity u, the MVD of spray droplets is affected not only by the simulated height H but also by the wind speed u. The wind speed affects the movement and evaporation process of droplets.

[0013] Relationship between MVD considering the cross-wind speed u, the simulated height H, the oncoming flow velocity u, and the oncoming flow temperature.

[0014] a) Influence of height H Changes in air pressure and air density: As the simulated height H increases, the air pressure and air density will decrease. The decrease in air pressure and air density will increase the evaporation rate of droplets and reduce the droplet diameter.

[0015] b) Influence of oncoming flow velocity u The cross-wind speed u affects the movement trajectory of droplets. The terminal velocity of droplets and the wind speed u jointly determine the path of droplet drift in the wind; a larger wind speed may cause droplets to break or deform in the wind, which also affects the MVD of droplets.

[0016] Terminal velocity of droplets moving naturally in the high-altitude test bench can be expressed as: ; where is the air density, is the liquid density, D is the droplet diameter, g is the gravitational acceleration, and C d is the drag coefficient related to the Reynolds number. The terminal velocity affects the movement state and residence time of droplets, thus indirectly affecting the evaporation rate. Among them, the air density varies with height: ; where e is the natural constant, R is the gas constant. The height H affects the air pressure and air density, thus affecting the evaporation rate of droplets. T is the temperature. The changes in air pressure and air density lead to fluctuations in the evaporation rate. Usually, the MVD of droplets decreases with the increase in height, and this change can be represented by an exponential function: ; Among them, k1 is a fitting coefficient that needs to be determined through experiments, representing the specific influence of height on MVD under different environmental conditions.

[0017] If there is air with an incoming flow velocity u, then due to the wind speed effect, the drift of droplets needs to be considered. Generally, however, the wind speed effect of droplets indirectly affects MVD by changing the movement trajectory and evaporation rate of droplets. And the evaporation rate E can be expressed as: ; Among them, 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, representing the influence of wind speed on the evaporation rate, and can usually be approximated as a linear function: ; Among them, k u is the coefficient of the influence of wind speed on the evaporation rate.

[0018] Therefore, there is: ; The wind speed u affects MVD by influencing the evaporation rate. An increase in wind speed will accelerate evaporation, thereby reducing MVD. This influence can be expressed as a correction factor: ; The explanation of this correction factor is as follows: The numerator part 1 + k u u represents the enhancement effect of wind speed on the evaporation rate. An increase in wind speed will increase the evaporation rate, thereby reducing MVD. The denominator part , where is the ratio of the evaporation rate to the terminal velocity, and k2 is a correction coefficient. This part considers the relationship between the evaporation rate and the terminal velocity of the droplet. A higher evaporation rate and a lower terminal velocity will result in a smaller MVD because the residence time of the droplet is shorter and evaporation is faster. Therefore, considering the influence of height H and wind speed u comprehensively, the change of MVD can be deduced. Assuming that MVD is the particle size under the reference conditions, under the influence of height H and wind speed u, the change of MVD can be expressed as: ; Each part of this expression reflects different aspects of the droplet behavior in actual situations: the influence of height is considered through the exponential function ; the influence of wind speed and evaporation rate is comprehensively considered through the correction factor to consider the influence of wind speed and terminal velocity on the droplet diameter.

[0019] The final expression is obtained by combining the theoretical model and experimental data. In practical applications, parameters such as MVD, k1, k2, and k can be determined through experimental fitting so that the model can accurately reflect the behavior of spray droplets under specific conditions. u

[0020] S3: Coupling Analysis of LWC Parameters and Inlet / Outlet Parameters Temperature, altitude, and oncoming flow velocity all affect cloud parameters. Among them, the influence of temperature is more obvious. When the ambient temperature is lower than -25°C, the evaporation effect can be ignored; altitude mainly affects the ambient pressure; the oncoming flow velocity mainly affects the evaporation rate. The greater the velocity, the greater the amount of evaporation, but the evaporation ratio decreases.

[0021] LWC is a relatively macroscopic and overall quantity. There is no need to study the liquid droplet particles themselves. Just focus on how much mass of liquid water is contained in a unit space. Concepts such as atmospheric moisture content and relative humidity can be borrowed for calculation and analysis. LWC can be obtained according to

[0022] Air saturation vapor pressure and temperature T are restricted by the following relationship: ; where T is the temperature in °C; the saturation vapor pressure , in kPa.

[0023] The atmospheric moisture content d represents the ratio of the mass of water vapor to the mass of dry air. It has the following relationship with the saturation vapor pressure, atmospheric relative humidity RH, and atmospheric pressure P: ; Based on this, the calculated mass flow rate of liquid water to be injected is: ; where the physical meaning of ϕ is: the ratio of the water mass flow rate (including liquid water and gaseous water) to the air mass flow rate , denoted as: ; The air mass flow rate is an engine inlet parameter and can be measured and calculated through sensors. consists of two parts. One is the water content in the test section space, and the other is the water content lost with the flowing air. Now consider the parameter coupling situation under steady-state spray conditions. Assume the volume of the test space 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 obtain ; 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. Multiplying it by volume V is the mass of liquid water. Similarly, multiplying it by volume V is the mass of gaseous water. The sum of these two parts is the mass of all water. Dividing it by the spray time t gives the mass flow rate. In summary, the ratio of water mass flow rate to air mass flow rate φ can be calculated by the following formula: ; All parameters in this formula can be measured directly or indirectly, including absolute humidity It is necessary to use a hygrometer to directly measure the relative humidity RH; the measurement of the water content LWC of the high-altitude platform is relatively complicated. For the measurement of LWC, the scattered particle spectrum detection (FSSP), optical array detection (OAP), hot wire method, ultrasonic method, etc. can be used to directly measure LWC. The most commonly used ice knife method can also be used for measurement. The ice knife is placed in an icing wind tunnel for experiment, and the LWC is calculated by analyzing the mass of ice on the ice knife.

[0024] Through the above analysis, the LWC, intake and exhaust parameters and theoretical water injection volume can be intuitively characterized. The coupling relationship between them is as follows: ; Among them, b = V / t, which is related to the size of the test section and is a constant.

[0025] S4: Spray system air pressure control method 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.

[0026] S5: Spray system water pressure control method The air supply system of the spray system adopts circulating water supply, and multiple spray rakes share a water supply main. For a certain working pressure, it can be obtained by different combinations of water pump flow, inlet and outlet regulating valve opening, but adjusting the three parameters at the same time will interfere with each other, there is a very serious coupling problem, and it is difficult to accurately control the pressure of each branch. In order to avoid multi-variable simultaneous adjustment as much as possible and weaken the coupling problem between each branch, the spray rake water pressure control design process is designed.

[0027] The entire control process is as follows: In the main water supply path, the rotational speed of the water pump is preset in advance to achieve the control of the main path water supply flow rate; in multiple parallel branches, the inlet regulating valve is preset with a fixed opening degree, which plays a role in throttling, pressure reduction, and to a certain extent, isolating the mutual influence of each branch; to reduce the pressure fluctuation in the branch, the outlet regulating valve can also be preset with an opening degree first. This opening degree parameter can be obtained through multiple tests and is an empirical value. Then, the opening degree is finely adjusted through a closed-loop control algorithm to achieve precise control of the pressure in each branch. During the spray test, when the solenoid valve is opened instantaneously, the opening degree of the inlet regulating valve of each spray rake remains unchanged. According to the pressure fluctuation caused by the water spray volume of the nozzle, the outlet regulating valve adjusts the opening degree through closed-loop control after spraying to complete the precise control of the pressure during the spray test. This scheme of determining the water pump rotational speed and presetting the opening degree of the inlet regulating valve in advance can effectively solve the problem of mutual interference in the process of multi-variable joint control. Among them, the closed-loop control algorithm is the main design. For the analysis of coupling, a control strategy based on feedforward decoupling is adopted.

[0028] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for controlling cloud parameters in an aviation engine intake icing environment simulation test, characterized in that Including the following steps: S1: Establish the influence of the water pressure and air pressure of the spray system on the average droplet diameter; S2: Calculate the influence of the height simulation parameter and wind speed on the average droplet diameter; S3: Conduct a coupling analysis on the liquid water content parameter and the intake and exhaust parameters, and calculate the required water injection volume; S4: Adopt a one-way gas supply system to achieve precise control of the air pressure of the spray system; S5: Adopt a circulating water supply system to achieve stable control of the water pressure of the spray system.

2. The method for controlling cloud parameters in an aero-engine inlet icing environment simulation test according to claim 1, wherein, Specifically, S1 is as follows: Set the air pressure in a single test to a fixed value, and calculate the average water droplet diameter according to the fitting formula where x is the water pressure of the spray system, and a, b, c, d, and e are coefficients.

3. The method for controlling cloud parameters in an aero-engine inlet icing environment simulation test according to claim 2, wherein Specifically, S2 is as follows: According to the formula , calculate the influence of the height simulation parameter and wind speed on the average droplet diameter, where is the influence of the average droplet diameter under the influence of height H and wind speed u, e is the natural constant, and k1 is the fitting coefficient determined by experiments is the ratio of the evaporation rate to the terminal velocity, k2 is the correction coefficient, and k u is the coefficient of the influence of wind speed on the evaporation rate 4. The method for controlling cloud parameters in an aviation engine inlet icing environment simulation test according to claim 3, characterized in that, Specifically, S3 is as follows: According to the formula calculate the required water injection volume, where LWC is the liquid water content, RH is the relative humidity, is the saturation vapor pressure of air, is the absolute humidity, is the air mass flow rate, is the water injection volume, P is the atmospheric pressure, S is the cross-sectional area of the test section, b is a constant value, is the air velocity.

5. The method for controlling cloud parameters in an aviation engine intake icing environment simulation test according to claim 4, characterized in that, The measurement methods of the liquid water content include scattered particle spectrum detection, optical array detection, hot wire method, ultrasonic method or ice knife method.

6. The method for controlling cloud parameters in an aviation engine inlet icing environment simulation test according to claim 1, wherein Specifically, S4 is as follows: Adopt a one-way gas supply system, and achieve precise control of the air pressure of the spray system through PID control combined with a multi-stage regulating valve.

7. The method for controlling cloud parameters in an aero-engine inlet icing environment simulation test according to claim 1, characterized in that, Specifically, S5 is as follows: Adopt a circulating water supply system, and achieve stable control of the water pressure of the spray system by presetting the pump speed, presetting the opening of the inlet regulating valve and controlling the outlet regulating valve in a closed loop, and adopt a feedforward decoupling strategy to eliminate the coupling interference between multiple branches.

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