Numerical Investigation of the NonUniform Flow Topography from TwinSilo Combustors and the Impact on Axial Turbine Performance From a Repowering Perspective

Abstract

From a repowering perspective, a clear understanding of the flow characteristics in older generation of industrial gas turbines operating with silo combustors is important. Nonuniform flow in the form of circumferential and radial pressure, temperature, velocity and approach angle variations can have a significant impact on the gas turbine stage performance and durability. This paper presents a comprehensive study of the underlying internal flow features involved in the birth of such nonuniformities from twinsilo combustors and their propagation through the 1st stage turbine of a Siemens v94.2 industrial gas turbine unit operated by a multimegawatt combined cycle powerplant. Results indicate a formation of strong vortical structures with circumferential flow angle deviations in the top and bottom sections of the turbine due to turning of the flow in the silo combustor. As a result, a drop in isentropic efficiency and power output equivalent to 2.65% points and 1.8 MW, respectively is observed at baseload compared to a reference straight hot gas path case. A more severe drop in isentropic efficiency of approximately 5.6% points is also observed at partload operation with a marginal reduction in the power output. A favorable validation with the available measured data is also achieved. The findings not only have implications for the turbine aerodynamic design, but also for combustor system design from a repowering perspective.