Ice-Crystal Icing Accretion Studies at the NASA Propulsion Systems Laboratory

Struk, Peter M.; Agui, Juan H.; Ratvasky, Thomas P.; King, Michael C.; Bartkus, Tadas P.; Tsao, Jen-Ching

doi:10.4271/2019-01-1921

Cited by 11 publications

(12 citation statements)

References 27 publications

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“…A suite of intrusive probes were introduced, one at a time, into the flow just downstream of the facility's exit duct through a newly designed traversing system (see Ref. [4] for a description of the traversing system) that made possible multiple probe samplings without stopping the flow. These particular instruments were used to measure the cloud's ice/water content, particle size distribution, and the flow's total temperature and humidity level.…”

Section: Test Setup and Methodsmentioning

confidence: 99%

“…This is because of the potential to ingest ice crystals or liquid water at the probe's inlet and for ice to accrete on the probe's body, which can result in a contaminated probe measurement. There are a couple of techniques to mitigate against these effects, which for instance involve inlet selfheating [4] or a rearward facing inlet probe design [3]. Probes utilizing both techniques were used in the current experimental test campaign.…”

Section: Total Temperature Measurement and Calibrationmentioning

confidence: 99%

“…A series of new experiments were recently performed at PSL to study the ice accretion processes on a NACA 0012 airfoil, under controlled simulated icing cloud flows. More details of these experiments is provided in an accompanying paper by Struk et al [4]. As part of these tests, the flow's aerothermal and cloud characterization were performed utilizing multiple probes to determine ice/water content and its spatial distribution, ice crystal particle size distribution, melt ratio, total temperature, and humidity levels in the test section.…”

Section: Introductionmentioning

confidence: 99%

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Total Temperature Measurements in Icing Cloud Flows Using a Rearward Facing Probe

Agui

Struk

Bartkus

2019

SAE Technical Paper Series

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This paper reports on temperature and humidity measurements from a series of ice-crystal icing tunnel experiments conducted in June 2018 at the Propulsion Systems Laboratory at the NASA Glenn Research Center. The tests were fundamental in nature and were aimed at investigating the icing processes on a two-dimensional NACA0012 airfoil subjected to artificially generated icing clouds. Prior to the tests on the airfoil, a suite of instruments, including total temperature and humidity probes, were used to characterize the thermodynamic flow and icing cloud conditions of the facility. Two different total temperature probes were used in these tests which included a custom designed rearward facing probe and a commercial self-heating total temperature probe. The rearward facing probe, the main total temperature probe, is being designed to reduce and mitigate the contaminating effects of icing and ingestion of ice crystals and water droplets at the probe's inlet. The probe also serves as an air-sample inlet for a light absorption based humidity measurement. The paper includes a section which discusses total temperature and humidity measurement considerations, and another section which provides an analysis of the main probe's performance characteristics. A computational fluid dynamic model of the flow around the probe was also conducted to gain insight into the trajectory of the flow entering the probe inlet. The experiments included a series of tests in which the relative humidity of the facility flow was swept through with increasingly larger values. The data showed that the rearward facing probe can reasonably capture the flow's total temperature and humidity under mild to moderate icing conditions but can produce anomalous results under more intense icing conditions. The experimental data was also compared to an in-house developed thermodynamic model which takes into account the interaction of the main flow with the icing cloud. Comparison to the thermodynamic model showed that the rearward facing probe measured the predicted trends.

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Section: Test Setup and Methodsmentioning

confidence: 99%

Section: Total Temperature Measurement and Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Total Temperature Measurements in Icing Cloud Flows Using a Rearward Facing Probe

Agui

Struk

Bartkus

2019

SAE Technical Paper Series

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“…To better understand the physical mechanisms of ice crystal icing, experiments have been conducted at the National Aeronautics and Space Administration (NASA) Glenn Research Center. Experimental studies on the fundamentals of ice crystal icing physics were conducted at the NASA Propulsion Systems Laboratory (PSL) in 2016 [2] and 2018 [3]. Other fundamental physics studies conducted elsewhere [4][5][6][7][8][9][10][11][12] have investigated altitude scaling [8], mixed-phase sticking efficiency [9], particle size effects [10,11], and accretion angle effects [12] related to ice crystal icing.…”

Section: Introductionmentioning

confidence: 99%

“…A new addition to the model in this work addresses this icing surface temperature. Using ice growth rates, airfoil thermocouple measurements and test conditions from a companion paper by Struk et al [3], the thermodynamic model will be further assessed, providing values to the unknown parameters of the melt-dominated or freeze-dominated ice accretions. These fundamental icing physics experiments were conducted at the NASA PSL icing wind tunnel in June 2018 using a NACA 0012 airfoil.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Experimental Ice Accretion Data and Assessment of a Thermodynamic Model during Ice Crystal Icing

Bartkus

Tsao

Struk

2019

SAE Technical Paper Series

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This paper analyzes ice crystal icing accretion data and evaluates a thermodynamic ice crystal icing model, which has been previously presented, to describe the possible mechanisms of icing within the core of a turbofan jet engine. The model functions between two distinct ice accretions based on a surface energy balance: freeze-dominated icing and melt-dominated icing. Freeze-dominated icing occurs when liquid water (from melted ice crystals) freezes and accretes on a surface along with the existing ice of the impinging water and ice mass. This freeze-dominated icing is characterized as having strong adhesion to the surface. The amount of ice accretion is partially dictated by a freeze fraction, which is the fraction of impinging liquid water that freezes. Melt-dominated icing occurs as unmelted ice on a surface accumulates. This melt-dominated icing is characterized by weakly bonded surface adhesion. The amount of ice accumulation is partially dictated by a melt fraction, which is the fraction of impinging ice crystals that melts. Experimentally observed ice growth rates suggest that only a small fraction of the impinging ice remains on the surface, implying a mass loss mechanism such as splash, runback, bounce, or erosion. The fraction of mass loss must be determined in conjunction with the fraction of freezing liquid water or fraction of melting ice on an icing surface for a given ice growth rate. This mass loss parameter, however, along with the freeze fraction and melt fraction, are the only experimental parameters that are currently not measured directly. Using icing growth rates from ice crystal icing experiments, a methodology that has been previously proposed is used to determine these unknown parameters. This work takes ice accretion data from tests conducted by the National Aeronautics and Space Administration (NASA) at the Glenn Research Center in 2018 that examined the fundamental physics of ice crystal icing. This paper continues evaluation of the thermodynamic model from a previous effort, with additions to the model that account for sub-freezing temperatures that have been observed at the leading edge of the airfoil during icing. The predicted temperatures were generally in good agreement with measured temperatures. Other key findings include the total wet-bulb temperature being a good first order indicator of whether icing is freeze-dominated (sub-freezing values) or melt-dominated (above freezing). Maximum sticking efficiency values, the fraction of impinging mass that adheres to a surface, was calculated to be about 0.2, and retained this maximum value for a range of melt ratios (0.3 to 0.65 and possibly higher), which is defined as the ratio of liquid water content to total water content. Higher air velocities reduced the maximum sticking efficiency and shifted the icing regime to higher melt ratio values. Finally, the leading edge ice accretion angle was found to be related to ice growth (lower growth rates for smaller angles) and melt ratio (smaller melt ratios resulted in smaller angles, li...

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An enthalpy-based model for the physics of ice-crystal icing

Peters,

Shelton,

Tang

et al. 2024

J. Fluid Mech.

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Ice-crystal icing (ICI) in aircraft engines is a major threat to flight safety. Due to the complex thermodynamic and phase-change conditions involved in ICI, rigorous modelling of the accretion process remains limited. The present study proposes a novel modelling approach based on the physically observed mixed-phase nature of the accretion layers. The mathematical model, which is derived from the enthalpy change after accretion (the enthalpy model), is compared with an existing pure-phase layer model (the three-layer model). Scaling laws and asymptotic solutions are developed for both models. The onset of ice accretion, the icing layer thickness and solid ice fraction within the layer are determined by a set of non-dimensional parameters including the Péclet number, the Stefan number, the Biot number, the melt ratio and the evaporative rate. Thresholds for freezing and non-freezing conditions are developed. The asymptotic solutions present good agreement with numerical solutions at low Péclet numbers. Both the asymptotic and numerical solutions show that, when compared with the three-layer model, the enthalpy model presents a thicker icing layer and a thicker water layer above the substrate due to mixed-phased features and modified Stefan conditions. Modelling in terms of the enthalpy poses significant advantages in the development of numerical methods to complex three-dimensional geometrical and flow configurations. These results improve understanding of the accretion process and provide a novel, rigorous mathematical framework for accurate modelling of ICI.

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Ice-Crystal Icing Accretion Studies at the NASA Propulsion Systems Laboratory

Cited by 11 publications

References 27 publications

Total Temperature Measurements in Icing Cloud Flows Using a Rearward Facing Probe

Total Temperature Measurements in Icing Cloud Flows Using a Rearward Facing Probe

Analysis of Experimental Ice Accretion Data and Assessment of a Thermodynamic Model during Ice Crystal Icing

An enthalpy-based model for the physics of ice-crystal icing

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