Analysis of the Heat Transfer Driving Parameters in Tight Rotor Blade Tip Clearances
| Autor: | Sergio Lavagnoli, Guillermo Paniagua, Cis G. De Maesschalck |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Convection
Engineering Materials science Adiabatic wall Convective heat transfer Thermodynamics Mechanical engineering 02 engineering and technology Heat transfer coefficient 01 natural sciences 010305 fluids & plasmas law.invention Physics::Fluid Dynamics Tip clearance 0203 mechanical engineering law 0103 physical sciences General Materials Science Critical heat flux Rotor (electric) business.industry Mechanical Engineering Thermal contact Mechanics Condensed Matter Physics Churchill–Bernstein equation 020303 mechanical engineering & transports Heat flux Mechanics of Materials Heat transfer business |
| Zdroj: | Volume 5B: Heat Transfer. |
| DOI: | 10.1115/gt2014-25291 |
| Popis: | Turbine rotor tips and casings are vulnerable to mechanical failures due to the extreme thermal loads they undergo during engine service. In addition to the heat flux variations during the engine transient operation, periodic unsteadiness occurs at every rotor passage, with amplitude dependent on the tip gap. The development of appropriate predictive tools and cooling schemes requires the precise understanding of the heat transfer mechanisms. The present paper analyses the nature of the overtip flow in transonic turbine rotors running at tight clearances and explores a methodology to determine the relevant flow parameters that model the heat transfer. Steady-state three-dimensional Reynolds-averaged Navier–Stokes (RANS) calculations were performed to simulate engine-like conditions considering two rotor tip gaps, 0.1% and 1%, of the blade span. At tight tip clearance, the adiabatic wall temperature is no longer independent of the solid thermal boundary conditions. The adiabatic wall temperature predicted with the linear Newton's cooling law was observed to rise to unphysical levels in certain regions within the rotor tip gap, resulting in unreliable convective heat transfer coefficients (HTCs). This paper investigates different approaches to estimate the relevant flow parameters that drive the heat transfer. A novel four-coefficient nonlinear cooling law is proposed to model the effects of temperature-dependent gas properties and of the heat transfer history. The four-parameter correlation provided reliable estimates of the convective heat transfer descriptors for the 1% tip clearance case, but failed to model the tip heat transfer of the 0.1% tip gap rotor. The present study allows experimentalists to retrieve information on the gap flow temperature and convective HTC based on the use of wall heat flux measurements. The use of nonlinear cooling laws is sought to improve the evaluation of the rotor heat transfer data while enhancing the understanding of tight-clearance overtip flows. |
| Databáze: | OpenAIRE |
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