Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-11-28
2001-11-20
Wu, Daniel J. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S581000, C340S962000, C073S170170, C244S13400A
Reexamination Certificate
active
06320511
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a configuration of an ice detector that detects ice at temperatures that are near freezing and which has a pressure field that reduces the pressure on surface regions so that such regions cool to a lower temperature as air flows past the detector to detect ice prior to formation on critical aircraft surfaces. The ice detector is used on air vehicles and provides a warning of actual ice accretion.
Existing magnetostrictive ice detectors perform well over the typical aircraft performance envelope. However. as more and more aircraft are designed with high performance wings situations may arise at temperatures near freezing where ice will form on a wing while the conventional ice detector provides no information indicating ice. The critical temperature is defined as the temperature above which no ice will form on a structure given the aircraft configuration and other atmospheric conditions. The critical temperature can be different for a typical airfoil configuration and for a conventional ice detector, at the same airspeed. The conventional ice detectors generally have a circular cross section probe.
A paper entitled “Equilibrium Temperature of an Unheated Icing Surface as a Function of Air Speed”, Messinger, B. L., J. Aeronaut. Sci., p. 29-42, January 1953, provides insight into the thermodynamic balance at temperatures near the critical temperature for two dimensional cylinders. There comes a point in which the aerodynamic heating associated with direct impact cannot overcome the propensity of supercooled droplets (liquid water at temperatures below freezing) to change phase and remain on the structure as accreted ice. If the temperature is cold enough this will occur. In practice, the size of the ice detectors relative to the size of most wings can be selected so as to cause ice to accumulate on the detector faster than accretion on the wing, which is the intended result. This, however, did not take into account the fact that airflow over the lifting surface of the wing or airfoil can create localized areas of temperature colder than the ice detector. Hence ice accretion may occur on the wing at temperatures warmer than the conventional ice detector.
At high angles of attack, such as those present in takeoff and landing of an aircraft, the airflow around the leading edge of the wing accelerates around the top and creates a region of lower pressure or vacuum relative to ambient static pressure. This lower pressure in turn creates a temperature drop near the leading edge of the wing, and in the most extreme cases the area where the lower pressure occurs experiences ice accumulation. In other words, if supercooled droplets of water are present in the area of the wing where there is a lower pressure and a sufficient temperature drop occurs, ice will form.
SUMMARY OF THE INVENTION
The present invention relates to an ice detector strut and probe assembly that has a geometrical configuration that will alter the pressure distribution around the probe and reduce the temperature at some regions of the probe to a level less than the temperature on the critical surface of the aircraft that is to be protected from ice formation.
The geometrical configuration of the probe assembly can be an airfoil cross sectional shape, or can be a cylinder with a strut that alters the airflow to achieve the desired pressure distribution.
In one form an airfoil cross section probe is oriented relative to a wing so that as the angle of attack of the wing increases, the angle of attack of the airfoil-shaped ice detector probe also changes and provides regions where a lower pressure occurs than at the associated wing surface. Using a probe with a shorter chord length, and having an appropriate airfoil shape relative to the shape of the wing, results in accretion of ice on the probe at temperatures above the critical temperature of the wing. Thus, ice accretes on the probe at temperatures warmer than that of the wing.
The airfoil-shaped probe is positioned so that the pressure field on the probe and adjacent to the probe is similar to, but creating lower pressure than, the wing airfoil at high operating angles of attack.
Additional forms of the invention show a cylindrical tube probe, that projects normal (or perpendicular) to the aircraft surface, and is arranged with a strut which modifies the flow past the probe in order to reduce the temperature on the probe. In other words, the strut geometry decreases the pressure and temperature at the probe surfaces to a level below that created by the wing or other structure with which the ice detector is used. In particular, the strut can incorporate bodies either fore or aft of the cylindrical probe with which to alter the pressure distribution around the probe.
Another form includes an axially extending rib on a lateral side of the probe. The rib will cause flow separation around the probe resulting in uneven or asymmetric pressure distribution with areas of the probe at a lower pressure than the aircraft skin and thus at a lower temperature.
Other methods can include strut and probe assemblies that have longitudinal axes that are not normal to the surface on which they are mounted, but inclined either forwardly or rearwardly so that the airflow past the probe is modified due to the probe inclination relative to the direction of airflow.
The flow can be guided and in all instances, the ice detector strut and probe assembly is formed to provide a pressure at a surface portion of the ice detector probe that is less than the pressure on the critical surface that is being protected by the ice detector. The reduction in pressure also causes a reduction in the temperature at the ice detector surface, thereby causing ice accretion at a warmer temperature than with conventional probes. The local pressure distribution on the ice detector probe is modified by the strut geometry, sweep of the probe, or by the formation of the airfoil shape cross section of the probe.
REFERENCES:
patent: 4054255 (1977-10-01), Magenheim
patent: 4210021 (1980-07-01), Vykhodtsev et al.
patent: 4333004 (1982-06-01), Forgue et al.
patent: 4611492 (1986-09-01), Koosmann
patent: 5003295 (1991-03-01), Kleven
patent: 5821862 (1998-10-01), MacKenzie
patent: 5955887 (1999-09-01), Codner et al.
patent: 6010095 (2000-01-01), Hackmeister
patent: 6052056 (2000-04-01), Burns et al.
patent: 6196500 (2001-03-01), Al-Khalil et al.
“Equilibrium Temperature of an Unheated Icing Surface as a Function of Air Speed”, Messinger, B.L., J. Aeronaut. Sci., pp. 29-42, Jan. 1953.
Cronin Dennis J.
Jackson Darren G.
Owens David G.
Nguyen Phung
Rosemount Aerospace Inc.
Westman Champlin & Kelly P.A.
Wu Daniel J.
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