Preprints
https://doi.org/10.5194/amt-2020-295
https://doi.org/10.5194/amt-2020-295

  08 Sep 2020

08 Sep 2020

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Photoacoustic hygrometer for icing wind tunnel water content measurement: Design, analysis and intercomparison

Benjamin Lang1,2,3, Wolfgang Breitfuss4, Simon Schweighart2, Philipp Breitegger1, Hugo Pervier5, Andreas Tramposch2, Andreas Klug2, Wolfgang Hassler2, and Alexander Bergmann1 Benjamin Lang et al.
  • 1Graz University of Technology, Institute of Electrical Measurement and Sensor Systems, Graz, Austria
  • 2FH JOANNEUM GmbH, Institute of Aviation, Graz, Austria
  • 3AVL List GmbH, Nanophysics & Sensor Technologies, Graz, Austria
  • 4RTA Rail Tec Arsenal Fahrzeugversuchsanlage GmbH, Vienna, Austria
  • 5Cranfield University, School of Aerospace, Transport and Manufacturing, Cranfield, UK

Abstract. This work describes the latest design, calibration and application of a near-infrared laser diode-based photoacoustic (PA) hygrometer, developed for total water content measurement in simulated atmospheric freezing precipitation and high ice water content conditions with relevance in fundamental icing research, as well as aviation testing and certification. The single-wavelength and single-pass PA absorption cell is calibrated for molar water vapor fractions with a two-pressure humidity generator integrated into the instrument. Laboratory calibration showed an estimated measurement accuracy better than 3.3 % in the water vapor mole fraction range of 510–12,360 ppm (5 % from 250–21,200 ppm) with a theoretical limit of detection (3 sigma) of 3.2 ppm. The hygrometer is examined in combination with a basic isokinetic evaporator probe (IKP) and sampling system designed for icing wind tunnel application, for which a general description of total condensed water content (CWC) measurement and uncertainties are presented. Despite the current limitation of the IKP to a hydrometeor mass flux below 90 g m−2 s−1, a CWC measurement accuracy better than 20 % is achieved by the instrument above a CWC of 0.14 g m−3 in cold air (−30 °C) with suitable background humidity measurement. Results of a comparison to the Cranfield University IKP instrument in freezing drizzle and rain show a CWC agreement of the two instruments within 20 %, which demonstrates the potential of PA hygrometers for water content measurement in atmospheric icing conditions.

Benjamin Lang et al.

 
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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Benjamin Lang et al.

Benjamin Lang et al.

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Short summary
This work describes the design, calibration and application of a hygrometer and sampling system, which have been developed and used for water content measurement in experimentally simulated atmospheric icing conditions with relevance in fundamental icing research, as well as aviation testing and certification. Together with a general description of water content measurement and accompanied uncertainties, results of a comparison to reference instruments in an icing wind tunnel are presented.