Conjugated Heat Transfer Analysis of Heated Aeronautical Pitot Probes With Flight Tests Experimental Validation

摘要

A theoretical-experimental study of the conjugated heat transfer problem associated with the transient thermal behavior of a heated aeronautical Pitot tube is undertaken, including flight tests of experimental validation with the military aircraft A4 Skyhawk probe. The aim is to demonstrate the importance of accounting for the conduction-convection conjugation in more complex models that attempt to predict the thermal behavior of the anti-icing system of such sensors under adverse atmospheric conditions. The theoretical analysis involves the proposition of an improved lumped-differential model for heat conduction along the probe, approximating the transversal temperature gradients within the metallic and ceramic walls. The convective heat transfer problem in the external fluid is solved using the boundary layer equations for compressible flow, applying the Illingsworth variables transformation considering a locally similar flow. The nonlinear partial differential equations are solved using the Generalized Integral Transform Technique in the Mathematica v7.0 platform. The experimental analysis involves the use of thermocouples fixed to the surface of the Pitot tube and temperature measurements acquired by a data logger installed in the frontal cone of the airplane. The transient thermal behavior has been promoted by the A4 pilot through intermittent disconnection and reconnection of the Pitot probe heating system, which allowed for critical comparisons between the model and the actual flight thermal response of the Pitot tube structure.