Techniques to quantify internal heat transfer of current and future effusion-cooled combustor walls

A requirement in the design and operation of gas turbines is to control the metal temperature of the combustor. One method by which this can be achieved is by passing compressor delivery air through arrays of cylindrical, angled effusion holes located in the combustor walls. However, recent advances in additive manufacturing technology have presented the opportunity to develop intricate effusion geometries that offer potential improvements in cooling performance compared to the current state-of-the-art. Much progress has been made in the development of experimental techniques to measure external heat transfer coefficients, film cooling effectiveness and overall cooling effectiveness in these complex effusion cooled walls. However, spatially resolved measurements of the internal convective heat transfer coefficient (HTC) are also required to fully explore the new design space. The research presented in this thesis has developed the capability to quantify these internal HTC distributions from transient convective heat transfer experiments at combustor-scaled near-atmospheric conditions employing thermochromic liquid crystals (TLCs) and 3D infrared (IR) thermography. The transient TLC technique has been improved by using a state-of-the-art imaging system and a new post-processingmethodology. These, along with fundamental research on the optical and ageing effects of multiple TLC films, have allowed to reduce and more accurately quantify the true measurement uncertainty of internal HTC distributions. For test specimens in which internal optical access is limited or not possible, such as for the study of surface roughness effects, a hybrid inverse-conduction technique comprising 3D IR thermography and transient heat transfer simulations has been developed to quantify internal HTCs. This technique is expected to play an important role in the design and development of low-cost additive-manufactured combustors for future aero-engines.