Abstract
A laboratory experimental method and an analysis technique are presented for evaluation of individual film-cooling row flow capacity characteristics. The method is particularly suited to complex systems such as hot section nozzle guide vanes (NGV) with lossy feed system characteristics. The method is believed to be both more accurate and more experimentally efficient than previous techniques. The new analysis technique uses an experimentally calibrated network model to represent the complex feed system and replaces the need for internal loss measurements, which are both demanding and inaccurate. Experiments are performed in the purpose-built University of Oxford Coolant Capacity Rig (CCR), a bench-top, blow-down type facility with atmospheric back-pressure. The design of the CCR is informed by the requirements to assess engine-scale film-cooled components rapidly, accurately, and precisely. Improvements in the experimental method include a differential mass flow rate measurement method (which eliminates the effect of leaks and minimizes the number of rows that must be blanked, ensuring that the internal coupling is as close as possible to the engine condition) and a variable bypass flow which ensures the mass flow measurement nozzle always operates within its calibrated range. We demonstrate the method using two high-pressure (HP) NGV designs: an engine part with relatively uncoupled (in terms of internal loss) cooling rows; and a laser-sintered part with highly coupled cooling rows. We show that the individual-row flow capacity of a high-pressure nozzle guide vane (HPNGV) can be evaluated in the CCR in a single day to a 2σ precision of approximately 0.5% and a 2σ accuracy (bias) of 0.6%. The importance of performing individual-row capacity measurements is demonstrated: failure to scale flow capacity on a row-by-row basis introduces an error of 30% in the engine situation.
Highlights
Precise prediction of coolant mass flow through individual film cooling rows is necessary to accurately predict part cooling effectiveness, overall capacity [1], and engine efficiency [2]
The purpose of this paper is to present a rapid and accurate laboratory experimental technique to measure individual-row coolant mass flow rate—or coolant flow capacity—of engine-scale turbine vanes at engine conditions
The technique is applicable to real engine components and laboratory proxies, which are increasingly used for high fidelity experimental assessment
Summary
Precise prediction of coolant mass flow through individual film cooling rows is necessary to accurately predict part cooling effectiveness, overall capacity [1], and engine efficiency [2]. The purpose of this paper is to present a rapid and accurate laboratory experimental technique to measure individual-row coolant mass flow rate—or coolant flow capacity—of engine-scale turbine vanes at engine conditions. The technique is applicable to real engine components and laboratory proxies (additive manufacturing), which are increasingly used for high fidelity experimental assessment. The technique is well suited to the mass flow rate range encountered for HPNGVs at laboratory conditions, allowing individual-row flow capacity measurements (of HPNGV) to be measured typically in a single day to a 2σ precision of ~0.3%. Laboratory experimental results are scaled to engine conditions using experimentally validated analytical tools which are described. Assessment of, for example, the onset of mainstream ingestion is possible using these tools
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