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

Lang, Benjamin; Breitfuß, Wolfgang; Schweighart, Simon; Breitegger, Philipp; Pervier, Hugo; Tramposch, Andreas; Klug, Andreas; Häßler, Wolfgang; Bergmann, Alexander

doi:10.5194/amt-14-2477-2021

Cited by 4 publications

(3 citation statements)

References 54 publications

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“…Splashing and bouncing effects, similar to those described by Korolev et al (2013) for an earlier, shallower version of the Nevzorov TWC cone, might occur on the 2.1 mm wide WCM-2000 TWC sensor. In line with these observations, a comparison of the WCM-2000 and the IKP shows that the LWC measurements of the IKP exceeded those of the WCM-2000 (Lang et al, 2021) in FZRA conditions even by as much as 65 %.…”

Section: Nevzorov Probe Measurements In Unimodal Sld Conditionssupporting

confidence: 75%

Icing wind tunnel measurements of supercooled large droplets using the 12 mm total water content cone of the Nevzorov probe

et al. 2022

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Abstract. Supercooled large droplet (SLD) icing can occur behind the protected surfaces of an aircraft and create severe aerodynamic disturbances, which represent a safety hazard for aviation. Liquid water content (LWC) measurements in icing conditions that contain SLDs require instruments that are able to sample unimodal and bimodal droplet size distributions with droplet diameters from 2 to 2000 µm. No standardized detection method exists for this task. A candidate instrument, which is currently used in icing wind tunnel (IWT) research, is the Nevzorov probe. In addition to the standard 8 mm total water content (TWC) collector cone, a novel instrument version also features a 12 mm diameter cone, which might be advantageous for collecting the large droplets characteristic of SLD conditions. In the scope of the two EU projects, SENSors and certifiable hybrid architectures for safer aviation in ICing Environment (SENS4ICE) and ICE GENESIS, we performed measurement campaigns in SLD icing conditions in IWTs in Germany, Austria and the USA. We obtained a comprehensive data set of measurements from the LWC sensor, the 8 mm cone sensor and the 12 mm cone sensor of the Nevzorov probe, and from the tunnel reference instrumentation. In combination with measurements of the particle size distribution, we experimentally derive a collision efficiency curve that is based on a suitable functional form for the new 12 mm cone for median volume diameters (MVDs) between 12 and 58 µm and wind tunnel speeds from 40 to 85 m s−1. Knowledge of this curve allows us to correct the LWC measurements of the 12 mm cone (LWC12) in particular for the inevitably high decrease in collision efficiency for small droplet diameters. In unimodal SLD conditions, with MVDs between 128 and 720 µm, LWC12 generally agrees within ±20 % with the tunnel LWC reference values from a WCM-2000 and an isokinetic probe. An increase in the difference between LWC12 and the WCM-2000 measurements at larger MVDs indicates better droplet collection properties of the 12 mm cone. Similarly, the favorable detector dimensions of the 12 mm cone explain a 7 % enhanced detection efficiency compared to the 8 mm cone; however this difference falls within the instrumental uncertainties. Data collected in various bimodal SLD conditions with MVDs between 16 and 534 µm and LWCs between 0.22 and 0.72 g m−3 also show an agreement within ±20 % between LWC12 and the tunnel LWC, which demonstrates the suitability of the Nevzorov sensor head with the 12 mm cone for measurements of LWC in Appendix O icing conditions.

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Section: Nevzorov Probe Measurements In Unimodal Sld Conditionssupporting

confidence: 75%

Icing wind tunnel measurements of supercooled large droplets using the 12 mm total water content cone of the Nevzorov probe

et al. 2022

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“…While those two instruments showed similar measurements of LWC in the supercooled liquid cloud condition (no ice crystals present), the multi-hot-wire probe recorded lower LWC values in ice crystal cloud conditions at approximately 60% [9]. To achieve more accurate measurements of TWC, analysis based on the existing experimental results and the development of other measurement devices is currently ongoing [88].…”

Section: ) Measurement On Ice Crystal Icingmentioning

confidence: 99%

A Review on the Current Status of Icing Physics and Mitigation in Aviation

2021

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Icing on an aircraft is the cause of numerous adverse effects on aerodynamic performance. Although the issue was recognized in the 1920s, the icing problem is still an area of ongoing research due to the complexity of the icing phenomena. This review article aims to summarize current research on aircraft icing in two fundamental topics: icing physics and icing mitigation techniques. The icing physics focuses on fixed wings, rotors, and engines severely impacted by icing. The study of engine icing has recently become focused on ice-crystal icing. Icing mitigation techniques reviewed are based on active, passive, and hybrid methods. The active mitigation techniques include those based on thermal and mechanical methods, which are currently in use on aircraft. The passive mitigation techniques discussed are based on current ongoing studies in chemical coatings. The hybrid mitigation technique is reviewed as a combination of the thermal method (active) and chemical coating (passive) to lower energy consumption.

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“…Freezing precipitation containing supercooled large drops (SLDs) with drop diameters in excess of 50 µm and convective mixed-phase and glaciated clouds with high mass concentrations of ice crystals, i.e., ice water content (IWC) up to several grams per cubic meter, constitute two particular meteorological environments associated with severe icing events (Politovich, 1989;Bernstein et al, 2000;Cober et al, 2001b;Riley, 1998).…”

Section: Introductionmentioning

confidence: 99%

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

Lang¹,

Breitfuß²,

Schweighart³

et al. 2020

Preprint

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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.

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

Cited by 4 publications

References 54 publications

Icing wind tunnel measurements of supercooled large droplets using the 12 mm total water content cone of the Nevzorov probe

Icing wind tunnel measurements of supercooled large droplets using the 12 mm total water content cone of the Nevzorov probe

A Review on the Current Status of Icing Physics and Mitigation in Aviation

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

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