Abstract
Advances in computer-based optimization techniques can be used to enhance the efficiency of energy conversions processes, such as by reducing the aerodynamic loss in thermal power plant turbomachines. One viable approach for reducing this flow energy loss is by endwall contouring. This paper implements a design optimization workflow for the casing geometry of a 1.5 stage axial turbine, towards mitigating secondary flows. Two different parametric casing surface definitions are used in the optimization process. The first method is a new nonaxisymmetric casing design using a novel surface definition. The second method is an established diffusion design technique. The designs are tested on a three-dimensional axial turbine RANS model. Computer-based optimization of the surface topology is demonstrated towards automating the design process. This is implemented using Automated Process and Optimization Workbench (APOW) software. Kriging is used to accelerate the optimization process. The optimization and its sensitivity analysis give confidence that a good predictive ability is obtained by the Kriging surrogate model used in the prototype design process tested in this work. A flow analysis confirms the positive impact of the optimized casing groove design on the stage isentropic efficiency compared to the diffusion design and compared to the benchmark axisymmetric design.
Highlights
The demand for electrical energy is projected to continue rising at substantial rates, due to the world's population growth and increased industrial activities
As most electrical energy is currently produced in thermal power plants, advances in the design of thermal cycles and of their individual components are required to ensure that this energy supply remains sustainable and affordable
A variety of toolchains is used by axial turbine designers, in which the performance and the cost of the design are significantly affected by the parametrization and optimization stages in the workflow
Summary
The demand for electrical energy is projected to continue rising at substantial rates, due to the world's population growth and increased industrial activities. Series based curves in the streamwise and pitchwise directions to define profiled endwall shapes They demonstrated a clear reduction in secondary flows and an increase in turbine efficiency. The computer-based optimization of the shape-defining parameters is a key enabler of performing axial and radial turbine designs [13e16] and it is used in the design of non-axisymmetric endwalls. Stage axial turbine that are used for establishing a baseline CFD model of the passage flow Tip diameter Hub diameter Passage height, h Aspect ratio, h=s Blade number Tip clearance Midspan blade pitch, t Inlet flow angle measured from the axial plane Design rotational speed, q_
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