CN104296957B - Method and system for measuring water drop collection coefficient of aerodynamic surface - Google Patents

Abstract

The present invention provides a method and system for measuring the droplet collection coefficient of an aerodynamic surface. including: heating the aerodynamic surface to a predetermined external surface temperature at a first power density under dry air at a specific velocity and a specific temperature; heating the aerodynamic surface to a predetermined external surface temperature at a second power density heating the aerodynamic surface to the predetermined external surface temperature, the humidified air has a specific liquid water content; and based on the specific velocity, the specific temperature, the liquid water content, the first power density, the The water drop collection coefficient of the aerodynamic surface is obtained based on the second power density and the predetermined external surface temperature. The method and system of the present invention can continuously measure the water droplet collection coefficient of aerodynamic surfaces in any state, especially for measuring the water droplet collection coefficient of aircraft aerodynamic surfaces (eg, wings, engine air intakes, etc.).

Description

Method and system for measuring droplet collection coefficient of an aerodynamic surface

technical field

The present invention relates to a method and system for measuring the droplet collection coefficient of an aerodynamic surface.

Background technique

When conducting anti-icing or icing simulation analysis, it is necessary to solve the heat flow required for water evaporation and heat dissipation, heating the supercooled water droplets, and the heat flow of the kinetic energy transformation of the water droplets. The three heat flows need to solve the impact water volume that hits the surface, and the impact water volume needs to solve the water droplet on the surface Collection factor. Among them, the amount of impinging water is a function of the droplet collection coefficient β, the air velocity V ₀ and the liquid water content LWC in the air. In order to verify the accuracy of the water droplet collection coefficient calculated by the calculation software or program, it is necessary to measure the water droplet collection coefficient through experiments.

A known drop collection factor method is the blotter staining method. Arrange the blotting paper on the measurement surface, the color of the blotting paper is darker in the area where the water droplets hit more, and the color is lighter in the area where the water droplet hits less. According to the color card, the impact water volume is obtained, and then the water droplet collection coefficient is obtained according to the impact water volume and the measurement time. In references "C.S. Bidwell, Cleveland, OH., S.R. Mohler, Jr. etc..' Collection Efficiency and Ice Accretion Calculations for a Sphere, a Swept MS(1)-317Wing, a Swept NACA-0012Wing Tip, an AxisymmetricInlet, and a Boeing737-300Inlet'AIAA-95-0755", using this method in the LEWIS Ice Wind Tunnel of the National Aeronautics and Space Administration (NASA) to test the sphere, MS-317 airfoil, NACA-0012 airfoil, and a symmetrical engine respectively. The air port and the B737-300 engine intake port measured their respective water drop collection coefficients to verify the accuracy of the water drop collection coefficient calculated by the LEWICE3D program.

The dyeing method of blotting paper is simple to operate, but it is limited by the water absorption capacity of blotting paper. For humid air with a large liquid water content, the blotting paper is oversaturated in a short period of time, so that it cannot be measured accurately. And in each state, the blotting paper needs to be replaced, so continuous measurement for different states cannot be performed.

Contents of the invention

The object of the present invention is to provide a method for measuring the droplet collection coefficient of an aerodynamic surface, which can continuously measure the droplet collection coefficient of the aerodynamic surface in any state, especially for measuring the aerodynamic surface of an aircraft (for example, Droplet collection coefficients for airfoils, engine intakes, etc.).

According to one aspect of the present invention, there is provided a method for measuring the droplet collection coefficient of an aerodynamic surface, said method comprising the steps of: heating said aerodynamic surface to a predetermined external surface temperature; heating said aerodynamic surface to said predetermined external surface temperature at said specified velocity and said specified temperature of humid air having a specified liquid state at a second power density water content; and based on the specified velocity, the specified temperature, the liquid water content, the first power density, the second power density, and the predetermined external surface temperature, obtaining all of the aerodynamic surface The water droplet collection coefficient.

In one embodiment, the first power density is a uniform value, the second power density is a distribution, and the predetermined external surface temperature is a distribution.

In another embodiment, the first power density is distributed, the second power density is distributed, and the predetermined external surface temperature is a uniform value.

The predetermined outer surface temperature is set such that supercooled water impinging on the aerodynamic surface evaporates completely at the point of impact. For example, the predetermined outer surface temperature is greater than 40°C.

Advantageously, the obtaining step includes:

- based on said second power density q _s and said first power density q _g , and according to the following formula, calculate the power density increment Δq

Δq= _qs - _qg ;

- Based on said power density increment Δq, said predetermined external surface temperature t _s , said specific temperature t ₀ and said specific velocity V ₀ , and according to the following formula, calculate the impact water volume W

Wherein said κ is an effective coefficient representing the ratio of the power density delivered to said aerodynamic surface to the heating power density, said _Cw is the specific heat of water, and said _Le is the latent heat of evaporation of water;

- Calculate the droplet collection coefficient β based on the impact water volume W, the liquid water content LWC and the specific velocity V ₀ according to the following formula

According to another aspect of the present invention, there is provided a system for measuring the droplet collection coefficient of an aerodynamic surface, the system comprising: a heater assembly disposed on the aerodynamic surface and configured to heat the the aerodynamic surface; a temperature sensor assembly disposed on the aerodynamic surface and configured to measure an outer surface temperature of the aerodynamic surface; and a controller coupled to the heater assembly and the aerodynamic surface, respectively the temperature sensor assembly, and is configured to: based on feedback from the temperature sensor assembly, control the heater assembly to heat the aerodynamic surface to a predetermined value at a first power density under dry air at a specific speed and a specific temperature surface temperature; adjusting the watt density of the heater assembly and heating the aerodynamic surface to the predetermined external surface temperature at a second watt density at the specified velocity and the specified temperature of humid air, the the humid air has a specific liquid water content; and based on the specific velocity, the specific temperature, the liquid water content, the first watt density, the second watt density, and the predetermined external surface temperature, calculating the The droplet collection coefficient of an aerodynamic surface.

In one embodiment, the first power density is a uniform value, the second power density is a distribution, and the predetermined external surface temperature is a distribution.

In another embodiment, the first power density is distributed, the second power density is distributed, and the predetermined external surface temperature is a uniform value.

Advantageously, said heater assembly comprises a set of heaters affixed to an inner surface of said aerodynamic surface, said temperature sensor assembly comprises a set of temperature sensors affixed to an outer surface of said aerodynamic surface , and each temperature sensor is correspondingly installed at the center of each heater.

The two heating modes described above are only two examples for realizing the object of the present invention, and it should be understood that the heating modes of the present invention are not limited to the above-mentioned specific modes.

Advantageously, said controller is configured to individually adjust the power density of each heater of said set of heaters.

Advantageously, the system further comprises: an insulating layer located between the aerodynamic surface and the heater assembly; an insulating layer located on the inner surface of the heater assembly.

Description of drawings

Other features and advantages of the present invention will be better understood through the following preferred embodiments described in detail in conjunction with the accompanying drawings. In the accompanying drawings, the same reference numerals identify the same or similar components, wherein:

Figure 1 shows a schematic diagram of an aerodynamic surface according to an embodiment of the invention;

FIG. 2 shows a system for measuring the droplet collection coefficient of an aerodynamic surface according to one embodiment of the present invention.

detailed description

The structural features, working principle and working process of the system for measuring the water droplet collection coefficient of an aerodynamic surface according to the present invention will be described in detail below. Here, the structural design drawings of the examples are only used to facilitate the understanding of the present invention, rather than specifically limiting the structural features of the present invention. In addition, in the following detailed description, directional terms, such as up, down, top, etc., are used with reference to the directions described in the drawings, and these directional terms are only for illustration rather than limitation. Therefore, the exemplary structural design diagrams and the following descriptions of the combined embodiments of the present invention are not intended to exhaust all embodiments according to the present invention.

Figure 1 shows a schematic diagram of an aerodynamic surface according to an embodiment of the invention. The example aerodynamic surface in the figure is an airplane wing. It can be understood that the aerodynamic surface involved in the present invention is not limited to the wing of an aircraft, it may also be an air intake of an aircraft engine and the like. The technical solutions of various embodiments of the present invention are used to measure the water drop collection coefficient of the exemplary aerodynamic surface shown in FIG. 1 .

FIG. 2 shows a system 20 for measuring the droplet collection coefficient of an aerodynamic surface according to one embodiment of the invention. The system 20 includes a heater assembly 201 disposed on an aerodynamic surface 30, such as an inner surface 301 of the aerodynamic surface 30, for heating the aerodynamic surface. Advantageously, an insulating layer 205 can be arranged between the heater assembly 201 and the inner surface 301 of the aerodynamic surface 30 , and an insulating layer 206 can be arranged on the other side of the heater assembly 201 opposite to the aerodynamic surface 30 .

The heater assembly 201 may for example comprise a set of heaters. Advantageously, an insulating and insulating material 207 may be arranged between the heaters. The heater can be any suitable heating device such as resistance wire or resistance film. The number of heaters can be determined from the measured area of the aerodynamic surface. Typically, the aerodynamic surface has a certain curvature (see Figure 1), therefore, advantageously, the heater is bendable so as to fit against the inner surface of the aerodynamic surface. The heater can be bonded to the inner surface of the aerodynamic surface by using heat-conducting silica gel, and of course, other suitable connection methods can also be used for connecting the heater to the inner surface of the aerodynamic surface.

Still referring to FIG. 2 , the system 20 also includes a temperature sensor assembly 202 disposed on the aerodynamic surface 30 , eg, an outer surface 303 of the aerodynamic surface 30 , for measuring the outer surface temperature of the aerodynamic surface. For example, temperature sensor assembly 202 may include a set of temperature sensors. Advantageously, each temperature sensor can be correspondingly installed at the center of each heater.

The temperature sensor may be a micro-volume type sensor such as a thermocouple. The temperature sensor can be fixed on the aerodynamic surface by bonding or other suitable connection means. In order not to affect the surface flow field, advantageously, a plurality of grooves can be provided on the outer surface 303 of the aerodynamic surface 30 , and each temperature sensor is embedded in the grooves, filled with thermally conductive silica gel or other high thermally conductive materials and then milled flat.

The system 20 also includes a controller 203, which is respectively coupled to the heater assembly 201 and the temperature sensor assembly 202, for controlling the heater assembly 201 to heat the aerodynamic surface 30, and for obtaining the aerodynamic surface measured by the temperature sensor assembly 202. 30 outside surface temperature. For example, for a group of temperature sensors in the temperature sensor assembly 202 , connecting wires can be respectively connected to the controller 203 through the fine holes at the bottom of the respective grooves and through the inner surface of the aerodynamic surface. A group of heaters in the heater assembly 201 can be respectively connected to the controller through connecting wires. Advantageously, the heating power of each heater in the heater assembly 201 can be individually controlled by the controller 203 .

In operation, the controller 203 controls each heater in the heater assembly 201 to heat the aerodynamic surface 30 to a predetermined outer surface temperature with a first power density under dry air at a specific speed and a specific temperature; then the controller 203 adjusts the heating The power density of each heater in the heater assembly 201, and at the same specific speed and the same specific temperature, and under humid air with a specific liquid water content, heat the aerodynamic surface 30 to the predetermined outer surface temperature at a second power density .

The predetermined outer surface temperature is set such that supercooled water impinging on said aerodynamic surface evaporates completely at the point of impact. For example, the predetermined outer surface temperature is greater than 40°C.

In one embodiment, the controller 203 firstly controls each heater in the heater assembly 201 to heat the aerodynamic surface 30 at the same power density (that is, the power density values in the first power density are the same), and The predetermined external surface temperature is measured by the temperature sensor assembly 202 . Since the local flow field and droplet impact characteristics of the aerodynamic surface are different, the predetermined external surface temperature measured by each heater after heating the aerodynamic surface with the same power density is a distribution, that is, in the entire heating area The outer surface temperature of an aerodynamic surface varies with spatial location. Then, under the same specific speed and the same specific temperature, and the humid air with specific liquid water content, the controller 203 adjusts the power density of each heater to another power density (each power density value in the second power density different) to heat the aerodynamic surface 30, and the predetermined outer surface temperature is measured by the temperature sensor assembly 202 (ie, consistent with the outer surface temperature heated to in dry air).

In another embodiment, the controller 203 firstly adjusts the power density of each heater in the heater assembly 201 to heat the aerodynamic surface 30, so that the temperature of each measurement point is the same, and obtains a predetermined external surface temperature by measuring the temperature sensor assembly 202 (The predetermined outer surface temperature is a uniform value, that is, the outer surface temperature in the entire heating area is consistent). Due to the difference in the local flow field of the aerodynamic surface and the impact characteristics of water droplets, in order to achieve the same temperature distribution, the heating power densities required by each heater are different (that is, the power density values in the first power density are different). Then, under the same specific speed, the same specific temperature, and the humid air with specific liquid water content, the controller 203 adjusts the power density of each heater to the second power density (the values of the power densities in the second power density are different ) to heat the aerodynamic surface 30, and the predetermined outer surface temperature is measured by the temperature sensor assembly 202 (ie, consistent with the outer surface temperature heated to in dry air).

Finally, the controller 203 obtains the droplet collection coefficient of the aerodynamic surface 30 based on the specific speed, the specific temperature, the liquid water content, the first power density, the second power density and the predetermined outer surface temperature.

For example, the controller 203 may obtain the water drop collection coefficient of the aerodynamic surface 30 in the following manner. Specifically, first, the controller 203 calculates the power density increment Δq based on the second power density q _s and the first power density q _g according to the following formula

Δq=q _s −q _g .

Next, the controller 203 calculates the impact water volume W based on the power density increment Δq, the predetermined outer surface temperature t _s , the specific temperature t ₀ and the specific speed V ₀ according to the following formula

Among them, κ is the effective coefficient, representing the ratio of the power density transmitted to the aerodynamic surface to the heating power density, C _w is the specific heat of water, and L _e is the latent heat of evaporation of water.

Then, the controller 203 calculates the water drop collection coefficient β based on the impacting water amount W, the liquid water content LWC and the specific velocity V ₀ according to the following formula

Controller 203 may be, for example, a microprocessor.

The technical content and technical features of the present invention have been disclosed above, and it should be understood that there are many modifications to the above embodiments, which are obvious to those skilled in the relevant art. These modifications/variations fall within the relevant field of the present invention and should also be included in the scope of the appended claims.

Claims (4)

1. a kind of method for being used to measure the drop collection coefficient of aerodynamic surface, the described method comprises the following steps：

- under the dry air of specific speed and specified temp, the aerodynamic surface is heated to predetermined with the first power density Hull-skin temperature；

- under the humid air of the specific speed and the specified temp, the air force table is heated with the second power density Face to the predetermined hull-skin temperature, the humid air has particular liquid water content；

- it is based on the specific speed, the specified temp, the Liquid water content, first power density, second work( Rate density and the predetermined hull-skin temperature, obtain the drop collection coefficient of the aerodynamic surface,

Wherein, the obtaining step includes：

- second power density and first power density are based on, and according to following formula, calculate power density increment

Δ q=q_s-q_g,

Wherein q_gRepresent first power density, q_sSecond power density is represented, Δ q represents power density increment；

- it is based on the power density increment, the predetermined hull-skin temperature, the specified temp and the specific speed, and root According to following formula, calculate and hit water

Wherein t_sRepresent the predetermined hull-skin temperature, t₀Represent the specified temp, V₀The specific speed is represented, W represents to hit The amount of striking waters, κ is coefficient of efficiency, characterizes the ratio of the power density for being delivered to the aerodynamic surface and heating power density, C_wFor the specific heat of water, L_eFor the evaporation latent heat of water；

- based on the shock water, the Liquid water content and the specific speed, and according to following formula, calculate the water droplet and receive Collect coefficient

Wherein, LWC represents the Liquid water content, and β represents the drop collection coefficient.

2. according to the method described in claim 1, it is characterised in that the predetermined hull-skin temperature is arranged to hit To the aerodynamic surface subcooled water at shock evaporating completely.

3. a kind of system for being used to measure the drop collection coefficient of aerodynamic surface, the system includes：

Heater assembly, it is arranged on the aerodynamic surface, and is configured as heating the aerodynamic surface；

Temperature sensor assembly, it is arranged on the aerodynamic surface, and is configured as measuring the air force table The hull-skin temperature in face；

Controller, it is respectively coupled to the heater assembly and the temperature sensor assembly, and is configured as：

Based on the feedback of the temperature sensor assembly, the heater assembly is controlled in specific speed and the dry sky of specified temp Under gas, the aerodynamic surface is heated to predetermined hull-skin temperature with the first power density；

The power density of the heater assembly is adjusted, and under the humid air of the specific speed and the specified temp, The aerodynamic surface is heated to the predetermined hull-skin temperature with the second power density, the humid air has particular liquid Water content；And

Based on the specific speed, the specified temp, the Liquid water content, first power density, second work( Rate density and the predetermined hull-skin temperature, calculate the drop collection coefficient of the aerodynamic surface,

Wherein, the controller is configured to：

- second power density and first power density are based on, and according to following formula, calculate power density increment

Δ q=q_s-q_g,

Wherein q_gRepresent first power density, q_sSecond power density is represented, Δ q represents power density increment；

- it is based on the power density increment, the predetermined hull-skin temperature, the specified temp and the specific speed, and root According to following formula, calculate and hit water

Wherein t_sRepresent the predetermined hull-skin temperature, t₀Represent the specified temp, V₀The specific speed is represented, W represents to hit The amount of striking waters, κ is coefficient of efficiency, characterizes the ratio of the power density for being delivered to the aerodynamic surface and heating power density, C_wFor the specific heat of water, L_eFor the evaporation latent heat of water；

- based on the shock water, the Liquid water content and the specific speed, and according to following formula, calculate the water droplet and receive Collect coefficient

Wherein, LWC represents the Liquid water content, and β represents the drop collection coefficient.

4. system according to claim 3, it is characterised in that the predetermined hull-skin temperature is arranged to hit To the aerodynamic surface subcooled water at shock evaporating completely.