Radiant energy – Infrared-to-visible imaging
Patent
1990-04-02
1991-09-03
Hannaher, Constantine
Radiant energy
Infrared-to-visible imaging
250332, 250334, 250347, 250352, G01M 900, G01J 500, G01P 510
Patent
active
050456997
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a heat imaging camera with a cooled detector mosaic for sensing convective conditions on a surface.
BACKGROUND INFORMATION
Such a heat imaging camera is known from EP 0,035,587 Al. The heat imaging camera described therein has a detector field with detectors sensitive in the infrared spectrum range. The camera detects temperature distributions and converts them to electrical signals. Furthermore, the temperature distribution is pictorially and graphically displayed with the aid of an evaluation unit.
A method for sensing convective conditions in boundary layer flows occurring on wind tunnel models, is known from the DE-OS 2,901,625, which discloses the analogy of heat and impulse transfer for sensing convective conditions in boundary layer flows occurring on wind tunnel models to determine temperature distributions.
OBJECTS OF THE INVENTION
It is an object of the invention to further develop the construction of a heat imaging camera so that it is suitable for sensing flow images in a cryogenic wind tunnel.
SUMMARY OF THE INVENTION
The heat imaging camera according to the invention is characterized in that its detectors for sensing convective conditions on the surface of a wind tunnel model at the temperature of the liquid nitrogen, are sensitive in the long-wave infrared and are cooled in a high vacuum with liquid helium, that the optical system of the camera is cooled with liquid nitrogen and is automatically adjustable to focus on the surface of the model, and in that a computer is connected to the camera for converting the temperature image into a flow image.
The essential advantage of the invention lies in the fact that the conditions of boundary layer flows on wind tunnel models are sensed from the outside with the aid of the heat imaging camera according to the invention, particularly at low temperatures. Thus, the flow boundary layer can be sensed in a temperature range from 80.degree. to 350.degree. Kelvin with a high temperature resolution of 0.1 Kelvin, a spatial resolution of up to 2 mrad, and a chronological resolution of approximately 0.5 million image elements per second. Silicon detectors, such as doped silicon detectors, operated as extrinsic photoconductors and sensitive to the long-wave infrared spectrum range of approximately 10 to 30 .mu.m are used for application in the cryogenic wind tunnel and are cooled to the temperature of liquid helium. The scene to be measured is scanned according to the so-called "step-and-stare method", whereby an individually programmed scanning pattern containing scanning units, senses the contours of the wind tunnel model.
With the aid of the apparatus according to the invention, shear stress fields resulting from convection on the surface of the model, laminar-turbulent transitions in the boundary layer flow, areas of flow separation, and the dynamic behavior in the boundary layer flow in the cryogenic wind tunnel can be determined at flight Reynolds numbers and displayed. The invention provides substantial savings in the operation of cryogenic wind tunnels and substantial improvements in performance through laminarizationon flight equipment and thus, a greater economic efficiency thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
Example embodiments of the invention are explained in more detail below, with reference to the accompanying drawings, wherein:
FIG. 1 shows a wind tunnel with an apparatus for sensing conditions of boundary layer flows on a model;
FIG. 2 shows a camera for the apparatus according to FIG. 1;
FIG. 3 shows a detector mosaic for the camera according to FIG. 2;
FIG. 4 is a top view of another half-model of a wind tunnel with a layout of scanning units; and
FIG. 5 is a block diagram for the apparatus according to FIG. 1, including an evaluation unit.
DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BEST MODE
OF THE INVENTION
As shown schematically in FIG. 1, an airplane model 2 is suspended in a cryogenic, closed-circuit wind tunnel 1 in which a camera 3 senses the
REFERENCES:
patent: 3977244 (1976-08-01), Stone
patent: 4507551 (1985-03-01), Howard et al.
patent: 4590375 (1986-05-01), Rovati et al.
patent: 4783593 (1988-11-01), Noble
D. M. Heath et al., "Remote Noncontacting Measurements of Heat Transfer Coefficients for Detection of Boundary Layer Transition in Wind Tunnel Tests" ICIASF 1987.
A. M. Bouchardy et al., "Processing of Infrared Thermal Images for Aerodynamic Research" Spie, vol. 397, pp. 304-309.
D. A. Dress et al., "Cryogenic Wind Tunnel Research: A Global Perspective", Cryogenics, vol. 28, No. 1, Jan. 1988.
Craubner Siegfried
Lange Guenter
Schulze Bernd
Deutsche Airbus GmbH
Fasse W. G.
Glick Edward J.
Hannaher Constantine
Kane, Jr. D. H.
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