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.
