| Popis: |
A novel experimental facility for the testing of modern high pressure nozzle guide vanes, the Annular Sector Heat Transfer Facility, is described in this thesis. Non- dimensionally similar conditions to a thermal paint test are reproduced, in a warm flow field, by the use of actual engine hardware, contoured sidewalls, and an innova- tive system of deswirl vanes in a five-passage annular sector cascade. External Mach and Reynolds numbers, inlet turbulence intensity, and coolant-to-mainstream pres- sure ratio are all matched to engine conditions. The test vanes are heavily cooled both internally (by convection and impingement) and externally (by film cooling). Detailed aerodynamic measurements are discussed, which demonstrate that a peri- odic, transonic, and highly engine-realistic flow is established in the cascade. High resolution full coverage maps of overall cooling effectiveness are presented, acquired on the vane surfaces at steady state conditions by wide-band liquid crys- tals and infrared thermography. Experimental measurements are then scaled to en- gine conditions by a new theoretical procedure, argued from first principles, which extends the principle of superposition to fully-cooled compressible flows. A newly- defined recovery temperature is proposed, which accounts for the redistribution of heat between the internal and external vane flows in a fully-integrated manner. This technique makes the results analogous to those of a thermal paint test, but allows for fundamental research and early and inexpensive cooling system validation. Overall cooling effectiveness measurements are complemented by those of the re- quired cooling flow capacity to achieve them, conducted in a second test rig commis- sioned during this research: the Flow Testing Facility. To conclude, the approach developed is applied to the global thermal assessment of the dendritic geometry, an innovative turbine cooling system. Experimental results show promising benefits over the baseline vane, especially in regions of low coolant-to-mainstream pressure margin. |
