Impact of Temperature Ratio on Overall Cooling Performance: Low-Order-Model-Based Analysis of Experiment Design

Abstract

This paper describes low-order-model-based analysis of the design of an experiment to be used for parametric studies of adiabatic film and overall cooling effectiveness for fully cooled systems (internal and film) under wide ranges of mainstream-to-coolant temperature ratio variation, in the range 0.50 < T0m/T0c < 2.30. The purpose is to improve understanding of—and validation of—the scaling process from typical rig conditions to engine conditions. We are primarily interested in the variation in overall effectiveness when the controlling non-dimensional groups change in a natural co-dependent way with changes in temperature ratio: that is, the practical situation of interest to engine designers. We distinguish this from the situation in which individual non-dimensional groups are varied in isolation: a situation that we believe is essentially impossible to meaningfully approximate in practice, despite a body of literature purporting to do the same. Design and commissioning data from a new high temperature (600 K) test facility is presented, with detailed uncertainty analysis. We show (using a low-order model) that a typical nozzle guide vane which at engine conditions (TR = 2.00) would have overall cooling effectiveness of 0.450, would be expected to have overall effectiveness of 0.418 at typical rig conditions (TR = 1.20). That is, typical scaling from engine-to-rig result is −7.1% and typical scaling from rig-to-engine is +7.7%. This result is important for first order estimation of overall cooling performance at engine conditions.