A kind of hypersonic oil film interferometry frictional resistance measurement experiment device and experimental method
Technical field
The present invention is to be related to a kind of wind tunnel test coefficient of frictional resistance measuring device and method, and in particular to a kind of high ultrasound
The experimental provision and method of oil film interferometry measurement coefficient of frictional resistance are utilized under the conditions of speed.
Technical background
Aircraft surface frictional resistance occupies a big chunk of drag overall in flight course, for passenger plane and large-scale fortune
For defeated machine, the size of skin friction resistance has a great impact for voyage and payload, for hypersonic aircraft
For, the size of skin friction resistance then affects the thermal protection system of surface heat flow and aircraft.Therefore, for aircraft table
The measurement of face frictional resistance just seems particularly significant.
Oil film interferometry is a kind of simple, effective coefficient of frictional resistance measurement method.Oil film interferometry measures table at present
Face coefficient of frictional resistance has had sufficient application, the good effect of acquirement in low speed, subsonic speed and Supersonic Stream.
But hypersonic inlet flow conditions and above-mentioned condition are very different, for example, hypersonic incoming flow total temperature is very high, cause to test
Segment model wall surface temperature is higher, and common Mylar film cannot be pasted onto model surface well in low speed experiment.Therefore for height
Supersonic Stream condition, oil film interferometry coefficient of friction resistance measuring technique need biggish improvement.
Existing literature is (for achievement, Zhang Changfeng, yellow hurricane, the hypersonic skin friction stress oil film interferometry skill of Zhou Qingzhan
Art research [J] experimental fluid mechanics, 2012,26 (02):It 68-71+85.) announces under a kind of hypersonic inlet flow conditions, utilizes
The experimental method of oil film interferometry measurement skin friction stress.Wind-tunnel incoming flow stagnation pressure is big in document experiment, has selected viscosity larger
Silicone oil, blow-time is longer, at high cost;And since long-time is dried, when oil film fringe spacing is by incoming flow disturbance
Between it is long, affect the reading of fringe spacing, cause experimental error;Silicon oil viscosity is greatly influenced by temperature, and blowing is made for a long time
At the variation of test model wall surface temperature, the size of silicon oil viscosity is affected, experimental error is also resulted in.
Therefore, under the conditions of hypersonic, existing oil film interference experiment method there is also very big deficiency, need into
Row improves, and can either improve experimental precision, and can be reduced experimental cost.
Summary of the invention
Technical problem solved by the invention is to provide a kind of hypersonic oil film interference friction resistance coefficient measuring device
And method, model surface coefficient of frictional resistance can be obtained using oil film interferometry under hypersonic inlet flow conditions, improved real
Precision is tested, experimental cost is reduced.
The present invention provides a kind of hypersonic oil film interference frictional resistance measurement experiment device:Including hypersonic wind tunnel, high pressure
Gas source, high-pressure sodium lamp, high speed camera, experimental model, analysis level silicone oil, thermocouple.
As a preferred solution of the present invention, the hypersonic wind tunnel tests Mach number Ma=5.Ma=5 is superb
Velocity of sound typical case's Mach number.
As a preferred solution of the present invention, 5 atmospheric pressure are set as in the high-pressure air source experiment, i.e. experiment stagnation pressure
For 5 atmospheric pressure.
As a preferred solution of the present invention, the high-pressure sodium lamp power 400W issues the monochromatic light of wavelength 589nm.
The sodium vapor lamp be placed on the hypersonic wind tunnel stay interior, for illuminating the surface of the experimental model.
As a preferred solution of the present invention, the high speed camera is the CCD high speed camera of HotShot company, collocation
Nikon50-200mm zoom lens, camera filming frequency are 100Hz.The high speed camera is placed on the sight in the portion in ceiling
It examines on window.
As a preferred solution of the present invention, the experimental model uses flat plate model.
As a preferred solution of the present invention, the experimental model surface plates one layer of black titanium, and it is good to guarantee that surface has
Good finish and refractive index, and being capable of high temperature resistant.
As a preferred solution of the present invention, it is the aperture of 1mm that, which there is diameter in experimental model model test region,.
As a preferred solution of the present invention, the thermocouple is placed in the aperture.
As a preferred solution of the present invention, the thermocouple probe and the flat plate model flush.
As a preferred solution of the present invention, viscosity is 50mPas under the analysis level silicone oil normal temperature state.
As a preferred solution of the present invention, the analysis level silicone oil is applied to the experiment at the thermocouple location
The surface of model.
For the experimental method of above-mentioned hypersonic oil film interference friction measurement experiment device, realized by following step:
Step 1:The experimental model test zone is illuminated using the sodium vapor lamp.
Step 2:The high speed camera angle is adjusted, so that test zone is high-visible, and carries out calibrating length.
Step 3:The analysis level silicone oil is painted along straight line in the model surface test zone.Oily line just covers institute
State position of thermocouple.
Step 4:It is 5 atmospheric pressure that the high-pressure air source, which is arranged, is blown in, and blow-time is 7~8 seconds.
Step 5:Using the stripe order recognition image of the analysis level silicone oil during high speed camera shooting blowing, simultaneously
Utilize test zone temperature variations during thermocouple record blowing.
Step 6:It is respectively t that access time, which is separated by shooting time,1And t2Two oil-film images, utilize image processing software
And theoretical analysis method carries out data processing:
1. according to oil film interference friction resistance coefficient calculation formula:
N in formula Chinese style0Indicate the refractive index of silicone oil, θ indicates refraction angle, and N represents the fringe order of calculating, and λ indicates examination
Test the wavelength of the monochromatic sodium vapor lamp of middle selection, t1And t2Respectively represent the initial time of oil film pattern shooting and by moment, above-mentioned ginseng
Number is known in an experiment.
2. Δ x indicates the total distance that N grades of stripeds move between two moment:
Δ x=Δ x (t2)-Δx(t1)
Wherein Δ x (t1) and Δ x (t2) respectively represent t1And t2The N grade oil film fringe spacing at moment.
3.q∞(t) the incoming flow dynamic pressure of different moments is indicated.In the case where hypersonic Ma=5, fluid has very strong
Compressibility, therefore the calculating formula of incoming flow dynamic pressure:
Middle density p∞With speed of incoming flow V∞It is all unknown quantity, incoming flow dynamic pressure q∞It can not be calculated.So dynamic pressure q∞Meter
Calculate the Bernoulli equation for using compressible flow:
In conjunction with one dimensional isentropic flow basic relational expression:
Derive dynamic pressure q∞Calculating formula:
γ represents the specific heat ratio of air in formula, is constant 1.4 in experiment;Ma represents experiment Mach number, Ma=5;p0And ρ0
Stagnation pressure and gross density are respectively represented, p and ρ represent static pressure and quiet density.Wherein p0It is set as 5 atmospheric pressure.
4. μ (t) indicates to test the viscosity of silicone oil different moments used.It is quasi- according to the Temperature-Viscosity of the analysis level silicone oil
Curve is closed, in conjunction with the temperature that the thermocouple measures, obtains t1And t2Film viscosity μ (the t at moment1) and μ (t2)。
5. the parameter of above-mentioned acquisition is brought into coefficient of frictional resistance calculation formula, rubbing for model surface measurement point is acquired
Wipe resistance coefficient.
Hypersonic oil film interference frictional resistance measurement experiment device of the present invention and its experimental method have the following advantages that:
1. present invention improves over low speed oil film interference experiment model surface processing method, by model surface black coating titanium,
Instead of the method for traditional stickup Mylar film, it both ensure that the refractive index of the finish of model surface, and also compensated for Mylar
The shortcomings that film can not be pasted under high temperature environment.
2. the present invention realizes under the conditions of identical Mach number, reasonable hypersonic incoming flow stagnation pressure and appropriate viscosity are set
Silicone oil, achieve good experimental result, and reduce experimental period, cost be greatly saved.
3. the present invention is acted upon by temperature changes to silicon oil viscosity and is demarcated such as Fig. 5, the precision of experiment is improved.
Detailed description of the invention
The present invention will be further described with reference to the accompanying drawings and examples.
Fig. 1 is experimental provision arrangement schematic diagram of the present invention
Fig. 2 is experimental model test zone detail view of the present invention
Fig. 3 is experimental method flow chart of steps of the present invention
Fig. 4 is different moments t of the invention1、t2Oil film striped schematic diagram
Fig. 5 is silicon oil viscosity-temperature influence curve that viscosity is 50mPas under the conditions of 25 DEG C
Fig. 6 is the oil film bar graph (shooting interval 1s) of actual experiment shooting of the present invention
Fig. 7 is influence of the silicone oil temperature adjustmemt to coefficient of frictional resistance measurement experiment result
In attached drawing
10 hypersonic wind tunnels 11 stay 12 observation window of room
20 high-pressure air source, 30 high-pressure sodium lamp, 40 high speed camera
50 experimental model, 60 analysis level silicone oil, 70 thermocouple
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to embodiments and attached drawing, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are only used to explain the present invention,
It is not intended to limit the present invention.
Such as Fig. 1, a kind of hypersonic oil film interference frictional resistance measurement experiment device:Including hypersonic wind tunnel (10), high pressure
Gas source (20), high-pressure sodium lamp (30), high speed camera (40), experimental model (50), thermocouple (60), analysis level silicone oil (70).
Such as Fig. 1, hypersonic wind tunnel (10) tests Mach number Ma=5.Ma=5 is hypersonic typical Mach number.
Such as Fig. 1,5 atmospheric pressure are set as in high-pressure air source (20) experiment, i.e., experiment stagnation pressure is 5 atmospheric pressure.
Such as Fig. 1, high-pressure sodium lamp (30) power 400W, the monochromatic light of wavelength 589nm is issued.Sodium vapor lamp is placed on the high ultrasound
Fast wind-tunnel is stayed in room (11), for illuminating the surface of the experimental model.
Such as Fig. 1, high speed camera is the CCD high speed camera of HotShot company, Nikon50-200mm zoom lens of arranging in pairs or groups,
Camera filming frequency is 100Hz.The high speed camera is placed on the observation window (12) in the portion in ceiling.
Such as Fig. 1, experimental model (50) uses flat plate model.
Such as Fig. 1, experimental model (50) surface plates one layer of black titanium, guarantees that surface has good finish and refractive index,
And it being capable of high temperature resistant.
Such as Fig. 2, it is the aperture of 1mm that experimental model (50) measured zone, which has diameter,.
Such as Fig. 2, thermocouple (70) is placed in aperture.
Such as Fig. 2, thermocouple (70) probe and experimental model (50) flush.
Such as Fig. 2, dynamic viscosity coefficient is 50mPas under 25 DEG C of states of analysis level silicone oil (60) room temperature.
Such as Fig. 2, analysis level silicone oil (60) is applied to the surface of the experimental model (50) of thermocouple (70) installed position.Such as
Fig. 3 is realized for the experimental method of above-mentioned hypersonic oil film interference friction measurement experiment device by following step:
Step 1:The experimental model test zone is illuminated using the sodium vapor lamp.
Step 2:The high speed camera angle is adjusted, so that test zone is high-visible, and carries out calibrating length.
Step 3:The analysis level silicone oil is painted along straight line in the model surface test zone.Oily line just covers institute
State position of thermocouple.
Step 4:It is 5 atmospheric pressure that the high-pressure air source, which is arranged, is blown in, and blow-time is 7~8 seconds.
Step 5:Such as Fig. 4, the stripe order recognition figure of the analysis level silicone oil during high speed camera shooting blowing is utilized
Picture, while utilizing test zone temperature variations during thermocouple record blowing.
Step 6:Such as Fig. 4, it is respectively t that access time, which is separated by shooting time,1And t2Two oil-film images, at image
It manages software and theoretical analysis method carries out data processing:
1. according to oil film interference friction resistance coefficient calculation formula:
N in formula Chinese style0Indicate the refractive index of silicone oil, θ indicates refraction angle, and N represents the fringe order of calculating, and λ indicates examination
Test the wavelength of the monochromatic sodium vapor lamp of middle selection, t1And t2Respectively represent the initial time of oil film pattern shooting and by moment, above-mentioned ginseng
Number is known in an experiment.
2. Δ x indicates the total distance that N grades of stripeds move between two moment:
Δ x=Δ x (t2)-Δx(t1)
Wherein Δ x (t1) and Δ x (t2) respectively represent t1And t2The N grade oil film fringe spacing at moment.
3.q∞(t) the incoming flow dynamic pressure of different moments is indicated.In the case where hypersonic Ma=5, fluid has very strong
Compressibility, therefore the calculating formula of incoming flow dynamic pressure:
Middle density p∞With speed of incoming flow V∞It is all unknown quantity, incoming flow dynamic pressure q∞It can not be calculated.So dynamic pressure q∞Meter
Calculate the Bernoulli equation for using compressible flow:
In conjunction with one dimensional isentropic flow basic relational expression:
Derive dynamic pressure q∞Calculating formula:
γ represents the specific heat ratio of air in formula, is constant 1.4 in experiment;Ma represents experiment Mach number, Ma=5;p0And ρ0
Stagnation pressure and gross density are respectively represented, p and ρ represent static pressure and quiet density.Wherein p0It is set as 5 atmospheric pressure.
4. μ (t) indicates to test the viscosity of silicone oil different moments used.Such as Fig. 5, according to the temperature-of the analysis level silicone oil
Viscosity matched curve obtains t in conjunction with the temperature that the thermocouple measures1And t2Film viscosity μ (the t at moment1) and μ (t2)。
5. the parameter of above-mentioned acquisition is brought into coefficient of frictional resistance calculation formula, rubbing for model surface measurement point is acquired
Wipe resistance coefficient.
Hypersonic oil film interference frictional resistance measurement experiment device of the present invention and its experimental method have the following advantages that:
1. present invention improves over low speed oil film interference experiment model surface processing method, by model surface black coating titanium,
Instead of the method for traditional stickup Mylar film, it both ensure that the refractive index of the finish of model surface, and also compensated for Mylar
The shortcomings that film can not be pasted under high temperature environment.
2., for the candy strip obtained in experiment, fringe order is enough, clear-cut texture such as Fig. 6.The present invention realizes
Under the conditions of identical Mach number, the silicone oil of reasonable hypersonic incoming flow stagnation pressure and appropriate viscosity is set, good experiment is achieved
As a result, improving precision, and reduce blow-time, cost is greatly saved.
3. the present invention is acted upon by temperature changes to silicon oil viscosity and is demarcated such as Fig. 5, the precision of experiment is improved.
There are many particular use of the present invention, the above is only a preferred embodiment of the present invention, it is noted that for this skill
For the those of ordinary skill in art field, without departing from the principle of the present invention, several improvement can also be made, these change
Into also should be regarded as protection scope of the present invention.