| An experimental and numerical study of 2 gas turbine duct geometries was performed to examine both their stand-alone performance and their performance with the addition of an entraining diffuser. Both ducts included a circular-to-slot transition with a 90° bend with an outlet aspect ratio of 5. The outlet orientation of the ducts was altered from in-line (longitudinal) to perpendicular (transverse) when referenced to duct inlet axis.; Scale model tests were performed on a cold-flow wind tunnel and were numerically predicted using the realizable k-epsilon turbulence model within the commercial Navier-Stokes solver, Fluent. Investigations were performed at 0°, 20° and 40° of inlet swirl, similar to conditions experienced during engine operation.; The results showed a significant improvement in the reduction of losses and inlet back pressure as the outlet orientation was changed from longitudinal to transverse. Improvement in these areas was seen on both ducts by the addition of an entraining diffuser. As inlet swirl was added, an increase in back pressure, flow distortion and losses was observed in addition to a decrease in pressure recovery. For all tests associated with the longitudinal duct, the design provided insufficient diffusion to overcome losses and create positive pressure recovery. Insufficient diffusion was also observed when 40° of inlet swirl was introduced into the transverse duct.; The CFD simulations were able to predict general flow patterns, but generally could not correctly identify performance parameter values or trends, indicating that the using CFD as per the method of this study is beneficial in the preliminary design stage only. |
