Keel probe

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Side view of the rockwell-MBB X-31 keel probe of the experimental aircraft

The keel probe , also known as the Kiel tube , is a further development of the pitot tube and named after its inventor Georg Kiel . It is used to measure the total pressure in moving flows and has the advantage over the normal pitot tube that it has a lower sensitivity with regard to the angle of attack .

Structure and functionality

View of the probe at an angle from the front. A little set back inside the Venturi nozzle, the narrow inlet opening of the pitot tube can be seen.

The keel probe essentially consists of a venturi nozzle with a pitot probe inside. The Venturi nozzle deflects the flow in the axial direction and thus ensures a more constant flow to the pitot probe. The geometry of the inlet is essential for the quality of the measuring arrangement. In addition to the radius of curvature of the inlet, ramp angle and diameter ratio of the Venturi nozzle, the position of the pitot probe in the axial direction also plays an important role for the sensitivity with regard to the angle of attack. Depending on the Mach number , good measurement results are achieved up to angles of attack of more than 60 ° relative to the axis of symmetry.

use

Climb with a large angle of attack. The keel probe mounted on the tip of the nasal mast can be seen in the picture above right, highlighted in light.

Keel probes are used wherever the total pressure is to be determined with a strongly varying direction of flow. In particular in the case of modern combat aircraft that fly at increasingly higher angles of attack, precise total pressure measurements are necessary to determine speed, even at high angles of attack. A well-known aircraft model that uses a keel probe is the Rockwell MBB X-31 - an experimental aircraft that was used, among other things, to research flight behavior at high angles of attack. Keel probes are also used in flight tests and in helicopters , where large changes in direction of the current can occur. The HASI sensor package of the Huygens space probe , which landed on Saturn's moon Titan , also contained a keel probe for scientific measurements during the descent through the atmosphere.

Alternatives

In addition to the aerodynamic design of the measuring point, there are other options for measuring total pressures in flows with strongly fluctuating directions. On the one hand, there are systems that have several measuring points with different orientations. The results of the individual measuring points are evaluated and then an overall solution is determined. On the other hand, tracking systems are also used, in which the pitot probe is aligned with the flow by means of a wind vane. The latter system was implemented in the Eurofighter .

Web links

Commons : Kielsonden  - Collection of images, videos and audio files

Individual evidence

  1. ^ A b G. Kiel: TN 775: Total-Head Meter with small sensitivity to yaw. (PDF; 559 kB) Retrieved July 15, 2013 .
  2. ↑ P. Balachandran: Fundamentals of Compressible Fluid Dynamics . 2006, ISBN 81-203-2857-4 , pp. 371 .
  3. ^ Walter R. Russell et al .: TN 2530: Wind tunnel testing of six shielded total-pressure tubes at high angles of attack. (PDF; 732 kB) Retrieved July 15, 2013 .
  4. ↑ United Sensor: Kiel Probes. Retrieved August 20, 2013 .
  5. ↑ Ryan F. Hook, Pennsylvania State University: A Study of Leading Edge Shapes for the Front Duct of a Dual Ducted Fan Vehicle . 2011.
  6. ↑ Joseph Sherma, Bernard Fried: Handbook of Turbomachinery . 2003, ISBN 0-8247-0995-0 , pp. 706 ff .
  7. ↑ SHJ Naarding, NG Verhaagen, TU Delft: Experimental and Numerical Investigation of the Vortex Flow over a Sharp Edgeed Delta Wing; with and without sideslip . 1988.
  8. ↑ Akademische Fliegergruppe Karlsruhe: Annual Report 2003. (PDF; 6.0 MB) (No longer available online.) Formerly in the original ; Retrieved July 15, 2013 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.akaflieg.uni-karlsruhe.de  
  9. ^ Leighton M. Myers: 67th American Helicopter Society International Annual Forum 2011: Investigation on Flow Physics of Edgewise Ducted Fan Air Vehicles . 2011, ISBN 978-1-61782-881-2 .
  10. ↑ M. Fulchignoni et al .: The Huygens Atmospheric Structure Instrument (HASI). Retrieved August 21, 2013 .
  11. ↑ ADS of the Eurofighter with movable pitot probes