Session: 12-03 Experimental techniques and scaling

Paper Number: 124338

124338 - Biot Number Error in Low Temperature Inconel Overall Effectiveness Experiments 

In order to predict the performance of turbine materials at engine conditions, experiments are often performed at lower temperature laboratory conditions. In order to ensure the low-temperature, laboratory results accurately predict the engine temperature performance, several non-dimensional parameters must be matched. These include the Biot number, coolant warming factor, adiabatic effectiveness, and the ratio of internal to external heat transfer coefficients. In order to match the Biot number, the ratio of the thermal conductivity of the material to the thermal conductivity of the air in the laboratory experiments must be matched to the engine conditions. With traditional nickel super alloys such as Inconel, it is sometimes assumed that the Biot number error is negligible as Inconel’s thermal conductivity variation with temperature scales relatively closely with that of air. However, the thermal conductivity ratio does not scale perfectly and therefore some Biot number error does indeed exist, with the problem generally exacerbated at lower experimental temperatures. Based on its thermal conductivity, Ti-6Al-4V is predicted to allow a better simulation of Inconel at engine conditions than Inconel does at typical low temperature experimental conditions. In this research, we utilized identical models constructed of Ti-6Al-4V and Inconel 718 to evaluate the differences and therefore discern the degree of error in overall effectiveness that might occur through simply using the same nickel alloy part at low temperature experimental conditions. The overall effectiveness experiments were conducted at a range of advective capacity ratios and the overall effectiveness distributions were compared.

Presenting Author: Bailey Hopkins US Air Force

Presenting Author Biography: Bailey earned his masters degree at the Air Force Institute of Technology in 2023 and is now a research engineer at the Turbine Engine Division of the Air Force Research Laboratory.

Authors:

Bailey Hopkins US Air Force
Jacob Hughes US Air Force
Carol Bryant US Air Force Academy
James L. Rutledge Air Force Institute of Technology