The Application of Thin Film Gauges on Flexible Plastic Substrates to the Gas Turbine Situation

Abstract

Thin film heat transfer gauges have been instrumented onto flexible plastic substrates which can be adhesively bonded to plastic or metal models. These new gauges employ standard analysis techniques to yield the heat flux to the model surface and have significant advantages over gauges fired onto machinable glass or those used with metal models coated with enamel. The main advantage is that the construction of the gauges is predictable and uniform, and thus calibration for thickness and geometric properties is not required. The new gauges have been used to measure the heat transfer to an annular turbine nozzle guide vane in the Oxford University Cold Heat Transfer Tunnel. Engine-representative Mach and Reynolds numbers were employed and the free-stream turbulence intensity at NGV inlet was 13%. The vanes were either precooled or preheated to create a range of different thermal boundary conditions. The gauges were mounted on both perspex and aluminium NGVs and the heat transfer coefficient was obtained from the surface temperature history using either a single layer analysis (for perspex) or double layer (for aluminium) analysis. The surface temperature and heat transfer levels were also measured using rough and polished liquid crystals under similar conditions. The measurements have been compared with computational predictions.

High Pressure Turbine Vane Annular Cascade Heat Flux and Aerodynamic Measurements With Comparisons to Predictions

“…Surface mounted thin-film heat flux gauges are platinum with copper leads. The gauges are fabricated on 50-micron polyirnide Upilex sheets using conventional photolithography techniques, Cue (1994), Guo et al (1995) and Jones (1995). Similar heat flux microsensors have also been developed by Vatell Corp. (Hager et al 1991).…”

Comparison of Thin Film Heat Flux Gauge Technologies Emphasizing Continuous-Duration Operation

“…Epstein et al [3,10] outlined the theory for double-sided heat flux gauges, followed by other practical studies on mid-span turbine heat transfer using the instrumentation with numerical post-processing schemes [12,13]. Since then, this technology has enabled the study of unsteady heat flux for turbine components in both the stationary [5,14,15] and rotating [15][16][17] reference frame of airfoils, in the tip region [18][19][20], and more, benefitting from a minimally intrusive design. Different types have been used [21][22][23][24], but all operate by solving the unsteady conduction equation through a substrate or substrates given a set of boundary conditions.…”

Endwall Heat Transfer and Aerodynamic Measurements in an Annular Cascade of Nozzle Guide Vanes

“…However, above free stream turbulence levels of 1-2% the transition is via a bypass mechanism and hence at the w e 0 E 0 large levels of turbulence in the tests reported here the gas to blade temperature ratio would have no influence. This has been demonstrated experimentally in the CHTT by measuring identical heat transfer coefficients for both precooled and preheated blades (Guo, Spencer, Lock, Jones and Harvey 1995). The tests therefore represent engine conditions well in that transition is not influenced and property effects may be taken into account.…”