A transient liquid crystal thermography technique for gas turbine heat transfer measurements

This paper presents in detail the transient liquid crystal technique for co nvective heat transfer measurements. A historical perspective on the active development of liquid crystal techniques for convective heat transfer meas urement is also presented. The experimental technique involves using a ther mochromic liquid crystal coating on the test surface. The colour change tim e of the coating at every pixel location on the beat transfer surface durin g a transient test is measured using an image processing system. The heat t ransfer coefficients are calculated from the measured time responses of the se thermochromic coatings. This technique has been used for turbine blade i nternal coolant passage heat transfer measurements as well as turbine blade film cooling heat transfer measurements. Results can be obtained on comple x geometry surfaces if visually accessible. Some heat transfer results for experiments with jet impingement, internal cooling channels with ribs, flow over simulated TBC spallation, flat plate film cooling, cylindrical leadin g edge and turbine blade film cooling are presented for demonstration.