Part of the life cycle of many industrial gas turbines often includes one or more performance uprates, typically defined by an increase in pressure ratio and/or firing temperature. In the process the hot section is usually only minimally modified due to cost and schedule limitations. As a result, the turbine section may operate at off-design with the last stage being most impacted. The exhaust system is thereby subjected to variations in inlet flow conditions, specifically the velocity and the flow angle, which adversely affect pressure recovery and impact overall engine performance. Similar variation in turbine exhaust inlet flow conditions arise for industrial two-shaft engines with power turbines operating at a wide range of speeds.
This paper describes studies completed using a quarter-scaled rig to assess the impact of turbine exit swirl and strut angular positioning on a turbine exhaust system that features an integral diffuser-collector. Advanced testing methods as well as flow visualization techniques are applied to ascertain exhaust performance for a range of inlet conditions aerodynamically matched to flow exiting an industrial gas turbine. Computational Fluid Dynamics (CFD) was extensively used to complement testing with the aim to ascertain the design phase and off-design performance prediction capability of modern day numerical tools.