Experimental and Numerical Investigation of an Aggressive Intermediate Turbine Duct: Part 2−Flowfield under Off-Design Inlet Conditions

Paper in proceeding, 2008

Intermediate turbine ducts (ITD’s) are annular S-shaped channels used in turbofan engines to guide the flow between the small-radius high-pressure turbine and the large-radius lowpressure turbine. This paper is the second part of a two-part paper presenting the results of a combined experimental and computational investigation of the flow in an aggressive intermediate turbine duct. The first part of the paper focused on the flowfield under the ITD design conditions. This second part of the paper presents and analyses the flowfield and performance under two off-design conditions (i.e. lower and higher turbine load). The focus is on the changes of the flowfield for these conditions as the inlet flow angles differ from the design values (e.g. flow separation occurs in the duct for the lower turbine load case) and the effect of this change on the duct performance. Total pressure losses are seen to increase for both off-design cases, especially for the case with flow separation (lower turbine load). The static pressure recovery is also found to be lower for the case with flow separation while for the higher turbine load tested it remains almost unchanged. In addition, differences found between the measured and predicted performance parameters are discussed. The experimental study was performed in a large-scale, low-speed turbine facility. The CFD computations were performed for the same flow conditions and used boundary conditions based on the measured inlet plane.