A STUDY ON THE PHYSICS OF ICE ACCRETION IN A TURBOFAN ENGINE ENVIRONMENT

Numerous turbofan engine loss of thrust control events have led to a theory that ice is accreting on initially warmer than freezing internal engine hardware and affecting normal operation. The phenomenon is termed ice crystal icing. Previous ice crystal icing research on a simple airfoil empirically identified the effects of pressure, temperature and relative humidity on the equilibrium surface temperature and the characteristic ice that accretes. In these cases with freezing fraction and impinging particle temperature as experimental unknowns, the on-set of ice accretion on an initially warmer than freezing surface was found to correlate with a below freezing thermodynamic wet-bulb temperature. In the present work, a novel ice accretion model, based on a modified Tribus-Messinger (MTM) surface energy balance, is developed. Implementing the model, the effect on the equilibrium surface temperature and freezing fraction near the leading edge stagnation region of an airfoil operating in icing conditions is investigated by varying the parameters of ambient static pressure, ambient static temperature, relative humidity and impinging particle temperature. The previously identified effects of pressure, temperature and relative humidity are identified as well as a new impinging particle temperature effect. A below freezing adiabatic saturation temperature, analogous to the thermodynamic wet-bulb temperature is calculated and shown to correlate with the predicted onset of ice accretion. Implementing the MTM model to investigate the physics of the modified surface energy balance, the pressure, temperature, relative humidity and impinging particle temperature effects are shown to be coupled within the latent, convective and sensible energy terms of the modified balance. The model predicts the observed onset of accretion and characteristic ice that forms on the surface from two experimental test cases. Control of the onset of ice accretion for these cases is demonstrated by varying the inputs to the model. It is also shown that by changing the impinging particle temperature for a given test condition the onset and characteristic ice that accretes can be influenced and predicted. Since particle temperature influences the surface temperature the wet-bulb temperature alone may not always predict the onset of ice accretion.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

EMC - Mechanical Engineering

Grantor dc:publisher

Case Western Reserve University School of Graduate Studies

Year dc:date

2013

Author dc:creator

• Oliver, Michael James

Contributors dc:contributor

• Prahl, Joseph

• Mechanical Engineering
• Aerospace Engineering
• Physics
• Engineering
• ice crystal icing
• turbofan engine inclement weather operation
• appendix D
• loss of thrust control
• physics of ice accretion in a turbofan engine environment

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=case1363875844

OAI identifier oai:identifier

oai:etd.ohiolink.edu:case1363875844