Improvements On Conventional Transient Thermal Measurement On Turbine Blade

This thesis presents experimental and numerical studies to improve conventional transientthermal measurement technique in turbine blade research. As one of the most vulnerablecomponents in a gas turbine, turbine blade needs to stand extremely high temperature in highspeed and high pressure working environment. Heat transfer and cooling technology has been animportant area in turbine blade designs. Accurate and robust thermal measurement technique,especially under an engine realistic transonic condition, can be regarded as a foundation forturbine blade heat transfer research.In the present study, supported by the National Science Foundation of China, a tran-sonic wind tunnel system was developed in the Aero-Thermal Laboratory of the University ofMichigan-Shanghai Jiao Tong University Joint Institute. A testing platform for the transonicturbine blade tip heat transfer study has been designed, built, and commissioned for the frsttime in China. Many eforts in the present study have been made to ensure the flow quality inthis testing rig. Uniform flow distribution was achieved by specially designed difuser sectionwith distributor structure. A modular test section was designed for the linear cascade bladesto reach transonic condition. The infrared thermography technique was employed to obtaina detailed temperature history of the blade tip surface during the transient experiment. Toaccommodate the temperature variation of the mainstream flow during the blow-down run, athermal analysis technique, which utilizes the decreasing process of the flow temperature inthe experiment, was developed, validated, and applied to calculate the convective heat transfercoefcient.A novel numerical corner conduction correction technique for conventional transient heattransfer analysis was developed in the present study. The semi-infnite one dimensional conduc-tion assumption is commonly adopted in the data processing for most of the transient thermalexperimental studies. The present work demonstrated that the calculated heat transfer coef-fcient based on this one dimensional approach can have large errors where lateral conductionefects are signifcant, especially, near a corner of the solid domain. The problem could beaddressed by alternative full three dimensional numerical conduction analysis, which requiresextra experimental eforts to obtain the full thermal boundary conditions around corners. Thenew approach presented in this thesis is based on the recognition that a temperature time tracein a two dimensional situation is the result of the accumulated heat conduction from the nor-mal and lateral directions respectively. An equivalent semi-infnite one dimensional conduction temperature trace for a correct heat transfer coefcient can be generated by reconstructing andremoving the lateral conduction efect at each discrete time step. This corrected time traceshould then enable the standard one dimensional conduction analysis to be properly used toget the correct heat transfer coefcient. It has been demonstrated that the errors in near thecorner regions can be greatly reduced by the new corner correction method. The demonstratedvalidity together with the simplicity and robustness of this method make it a good candidatefor future applications in transient thermal experimental studies.