CN-121994146-A - Hypersonic wind tunnel phase change sweating cooling liquid water outflow thickness measurement calibration method

CN121994146ACN 121994146 ACN121994146 ACN 121994146ACN-121994146-A

Abstract

The invention relates to the technical field of hypersonic aerodynamics experiment measurement and thermal protection, in particular to a hypersonic wind tunnel phase change sweating cooling liquid water outflow thickness measurement calibration method, which comprises the following steps of preparing fluorescent solution, and preparing fluorescent liquid films with different standard thicknesses as standard samples; collecting fluorescent images of fluorescent liquid films with known thickness, establishing a calibration relation between the fluorescent intensity and the thickness under different known thicknesses, carrying out temperature correction on the calibration relation, in hypersonic wind tunnel experiments, allowing fluorescent solution to permeate through a porous metal test piece, collecting fluorescent images to obtain the fluorescent intensity, measuring the real-time temperature of the surface of the porous metal test piece, substituting the collected fluorescent intensity value into the calibration relation after temperature correction, and obtaining the liquid water outflow thickness of the surface of the porous metal test piece. The method can adapt to the strong shearing and high-temperature environment of the hypersonic wind tunnel, and realizes non-contact, high-precision and full-field real-time measurement of the thickness of the liquid water outflow.

Inventors

WANG HONGWEI
LI XIAOHUI
REN SHAOJIE
CHEN XIYUE
LIU YAOFENG
HUANG ZHAN

Assignees

中国航天空气动力技术研究院

Dates

Publication Date: 20260508
Application Date: 20251229

Claims (10)

1. The hypersonic wind tunnel phase change sweating cooling liquid water outflow thickness measurement calibration method is characterized by comprising the following steps of: S1, preparing a fluorescent solution, and preparing fluorescent liquid films with different standard thicknesses as standard samples; S2, collecting fluorescent images of the fluorescent liquid films with known thicknesses, and establishing a calibration relation between the fluorescent intensity and the thickness of the fluorescent liquid films with different known thicknesses; S3, in a hypersonic wind tunnel experiment, the fluorescent solution is oozed out through a porous metal test piece, a fluorescent image of the area is acquired, and fluorescent intensity is obtained; S4, measuring the real-time temperature of the surface of the porous metal test piece, calling a calibration relation after corresponding temperature correction, substituting the fluorescence intensity value acquired in the step S3 into the calibration relation after correction, and obtaining the liquid water outflow thickness of the surface of the porous metal test piece.
2. The method according to claim 1, wherein the step S1 is characterized in that the water-soluble fluorescent substance is dissolved in deionized water to form a uniform fluorescent solution.
3. The method according to claim 2, wherein the water-soluble fluorescent substance is rhodamine B or sodium fluorescein.
4. The method according to claim 1, wherein the specific step of preparing the fluorescent liquid film with different standard thickness in step S1 is to provide standard thickness grooves with different thickness on the substrate, fill the fluorescent solution in the thickness grooves, and cover the surface of the substrate with the optical flat plate.
5. The method according to claim 1, wherein the specific step of establishing the calibration relation between the fluorescence intensity and the thickness of the fluorescent liquid film under different known thicknesses in the step S2 is: performing flat field correction on the fluorescent image, and deducting background noise; Calculating the average fluorescence intensity I corresponding to each thickness h; A linear calibration curve between I and h is established through least square fitting: I= K.h +i 0 formula (1); where K is the calibration coefficient and I 0 is the background noise strength.
6. The method according to claim 5, wherein the specific step of temperature correction of the calibration relation in the step S2 is to collect fluorescence images of the standard thickness fluorescent liquid film at different temperatures T and establish a calibration curve between I and h at different temperatures: i (T) =k (T) ·h+i 0 formula (2); establishing a correction relation between a calibration coefficient K and a temperature T through data fitting: K (T) =k 0 exp (- αt) formula (3); where K 0 and α are fitting constants.
7. The method according to claim 1, wherein the step S3 specifically comprises the steps of installing the porous metal test piece in a hypersonic wind tunnel experiment section, introducing the fluorescent solution into the porous metal test piece, allowing the fluorescent solution to permeate out through the porous metal test piece, projecting an illumination light source to an expected water outlet area on the surface of the porous metal test piece, enabling a high-speed camera to be perpendicular to a shooting plane, and collecting fluorescent images of the area.
8. A hypersonic wind tunnel phase change sweat cooling liquid water outflow thickness measurement calibration system, characterized by being used for implementing the method of claims 1-7, comprising: a fluorescent solution supply unit for supplying the prepared fluorescent solution into the porous metal test piece; an illumination light source unit for illuminating an area to be measured; The image acquisition unit is used for shooting fluorescent images of the region to be detected; the temperature measuring unit is used for monitoring the surface temperature T s of the porous metal test piece; and the data processing unit is used for calculating the thickness of the liquid water outflow on the surface of the porous metal test piece.
9. The system of claim 8, wherein the illumination light source unit employs a continuous or pulsed blue/green light band light source having an output wavelength matched to an absorption peak of the fluorescent substance in the fluorescent solution, and a light source shaping unit is provided at an output end of the light source to shape the light source into uniform light for uniformly illuminating the area to be measured.
10. The system of claim 8, wherein the image acquisition unit employs a high-speed camera, and a band-pass or high-pass filter matched with an emission spectrum of the fluorescent substance in the fluorescent solution is disposed at a front end of a lens of the high-speed camera, and the high-speed camera is perpendicular to a photographing plane and focuses on the region.

Description

Hypersonic wind tunnel phase change sweating cooling liquid water outflow thickness measurement calibration method Technical Field The invention relates to the technical field of hypersonic aerodynamics experiment measurement and thermal protection, in particular to a hypersonic wind tunnel phase change sweating cooling liquid water outflow thickness measurement calibration method. Background Hypersonic aircraft face severe aerodynamic thermal environments, and phase change sweating cooling technology is considered as a very promising active thermal protection solution due to its extremely high latent heat utilization efficiency. The technology permeates liquid coolant (such as water) to the high-temperature surface through the porous material, and the coolant absorbs heat and changes phase to take away a large amount of heat. The sweating cooling efficiency is directly related to the coverage state and thickness of the porous surface liquid water film. However, the hypersonic wind tunnel flow field has the characteristics of extremely strong shearing force, severe temperature change and much background interference, so that accurate thickness measurement of a dynamic change water film with the magnitude of micrometers to millimeters faces a great challenge. The existing measuring method such as a contact probe can seriously disturb a flow field, cannot obtain distribution characteristics and is slow in response, and the traditional optical method such as a laser interferometry is sensitive to vibration and a schlieren method is sensitive to density gradient, so that thin-layer liquid is difficult to distinguish, and the method is difficult to be applied to the severe environment. Therefore, the development of a thickness calibration method capable of resisting strong shearing, compensating temperature effects and realizing full-field real-time measurement is very important for quantitative research and engineering application of the sweating cooling technology. Disclosure of Invention The invention aims to overcome the defects of the prior art, provides a hypersonic wind tunnel phase change sweating cooling liquid water outflow thickness measurement and calibration method, the method can realize non-contact, high-precision and full-field real-time measurement of the thickness of the liquid water outflow in the strong shearing and high-temperature environment of the hypersonic wind tunnel. The invention provides a hypersonic wind tunnel phase-change sweating cooling liquid water outflow thickness measurement and calibration method, which comprises the following steps: S1, preparing a fluorescent solution, and preparing fluorescent liquid films with different standard thicknesses as standard samples; S2, collecting fluorescent images of the fluorescent liquid films with known thicknesses, and establishing a calibration relation between the fluorescent intensity and the thickness of the fluorescent liquid films with different known thicknesses; S3, in a hypersonic wind tunnel experiment, the fluorescent solution is oozed out through a porous metal test piece, a fluorescent image of the area is acquired, and fluorescent intensity is obtained; S4, measuring the real-time temperature of the surface of the porous metal test piece, calling a calibration relation after corresponding temperature correction, substituting the fluorescence intensity value acquired in the step S3 into the calibration relation after correction, and obtaining the liquid water outflow thickness of the surface of the porous metal test piece. Preferably, the specific step of preparing the fluorescent solution in the step S1 is to dissolve the water-soluble fluorescent substance in deionized water to form a uniform fluorescent solution. Preferably, the water-soluble fluorescent substance is rhodamine B or sodium fluorescein. Preferably, the specific step of preparing the fluorescent liquid film with different standard thickness in the step S1 is to provide standard thickness grooves with different thickness on the substrate, fill the fluorescent solution in the thickness grooves, and cover the optical flat plate on the surface of the substrate. Preferably, the specific step of establishing the calibration relation between the fluorescence intensity and the thickness of the fluorescent liquid film under different known thicknesses in the step S2 is as follows: performing flat field correction on the fluorescent image, and deducting background noise; Calculating the average fluorescence intensity I corresponding to each thickness h; A linear calibration curve between I and h is established through least square fitting: I= K.h +i 0 formula (1); where K is the calibration coefficient and I 0 is the background noise strength. Preferably, the specific step of temperature correction for the calibration relation in the step S2 is to collect fluorescence images of the standard thickness fluorescent liquid film at different temperatures T and establish