An experimental and numerical investigation of the effect of aero gas turbine test facility aspect ratio on thrust measurement.

Abstract

This work describes the outcome of research program investigating thrust measurements in enclosed test facility for modern aero gas turbine engines. Literature work, experimental work and a description of Computational fluid dynamics simulation system have been developed to improve the accuracy of test bed thrust measurement. The key parameters covered in the research include test house size in relation to engine size. The effect of the distance of engine to detuner on the thrust correction factor was also investigated. The rule of loss mechanism within the test facility to include intake momentum drag, cradle drag, base drag, recirculation on loss and intake exhaust losses loss. The thrust correction factor prediction technique available in the open literature are compared with the result given by this research and conclusion are drawn. CFD predictions show that the biggest difference with experimental data is only 1 % in TCF for the largest test cell size. For the smallest test cell this difference increases to only 2%. These results in terms of accuracy are lower than what would normally be expected for general CFD work. The major contributions to thrust measurement technology include the following: 1. The research was able to ascertain that as engine size increases it will become more risky to rely on test bed results as giving an accurate prediction of static thrust. 2. The work has enabled confident prediction that test bed results can give test bed static thrust compared to free air testing with an accuracy of one half of 1%. 3. Using Fluent it has been possible to reproduce a comparable comparison with test bed results. This will give the user of the research a higher level of confidence in predicting thrust measurements for test beds whose size is small in comparison with engine size. 4. It is of course an ambition for all those working in the field to eliminate engine testing. However this is unachievable ambition. This research has shown the way to improve CFD prediction towards achieving this ambition. Finally detailed recommendations are given for continuation for this research program.