Heat and mass transfer in two-phase flow around airfoils with aeronautical anti-ice systems.

Author(s)

Guilherme Araújo Lima da Silva

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2009-02-02

Examining board members

Otavio de Mattos Silvares; Pedro Carajilescov; Fernando Martini Catalano; Marcos de Mattos Pimenta; Euryale Jorge Godoy de Jesus Zerbine

• Advisor: Otavio de Mattos Silvares
• Field of knowledge: Engineering - Mechanical Engineering
• Location: Universidade de São Paulo. Biblioteca Central da Escola Politécnica

Abstract

It is required to prevent ice accretion on wings and horizontal stabilizers because it may cause aerodynamic performance degradation, weight increase, flight control difficulties and, in critical cases, may lead to operational safety margins reduction. When aircraft flies through clouds containnig supercooled water droplets, which are in metastable equilibrium, ice will form in all non-protected surfaces. Usually, anti-ice protection systems are designed, developed and certified with a support from a numerical tool. The present describes the development and implementation of a mathematical model for prediction of heat and mass transfer in two-phase flow around airfoils, which are equipped with thermal anti-ice system and operating in steady state regime. Under icing conditions, it is necessary to heat and control the temperature of the airfoil surface at leading edge region to prevent ice formation. The heating system balances the evaporative cooling effects, which are caused by the coupled heat and mass convection transfer, imposed by the air flow loaded with supercooled water droplets and the runback water flow around the airfoil. The present work implemented submodels to: 1) estimate airfoil surface wetness factor by adopting a liquid water film flow model as well as a rivulet formation and flow model; 2) evaluate laminar and turbulent boundary layers with pressure gradient and laminar-turbulent transition over nonisothermal and permeable airfoil surface by implementing differential boundary layer analysis and 3) predict the onset position and length of laminar-turbulent transition region. The present paper followed a validation and verification process during the numerical code development. All sub-models results were verified separately against experimental data before their inclusion in anti-ice model.The results of anti-ice model with selected submodels were validated against reference cases. The results were considered suficiently accurate when solving the film breakdown and rivulets formation by total mechanical energy method, compressible boundary layer by differential analysis and laminar-turbulent transition prediction by algebraic correlations, which considered pressure gradient and freestream turbulence level. (AU)

• FAPESP's process: 07/00419-0 - Heat and mass transfer in two-phase flow around airfoils with aeronautical anti-ice systems
• Grantee: Guilherme Araújo Lima da Silva
• Support type: Scholarships in Brazil - Doctorate