Abstract
A design optimization workflow for the casing of a 1.5 stage axial turbine is implemented through a novel endwall surface definition, towards improving the turbine efficiency. The new non-axisymmetric casing design compares favourably to an established diffusion design technique. The workflow uses an axial turbine three-dimensional Reynolds Averaged Navier-Stokes model built in OpenFOAM Extend 3.2 with the k-ω Shear Stress Transport turbulence closure. Computer-based optimization of the surface topology using a Kriging surrogate model automates the design process. The designs are optimized using the total pressure loss across the full stage as the target function. Axial turbine performance gains are obtained from the workflow, which persist both at the design condition and off-design. These gains are used to project the impact of equivalent design improvements to the power turbine of a representative Natural Gas liquefaction plant cycle. Cycle Coefficient of Performance enhancements between 2.05% and 2.923% are obtained, at design and at off design conditions. Implementing these performance improvements has the potential to reduce carbon dioxide emissions by 165.54 tonnes per year at design and by 108.18 tonnes per year at off design, in a representative Natural Gas liquefaction plant.
Highlights
Due to the world’s population growth and increased industrial activities, the demand for energy is increasing continuously and is projected to grow at a rising rate
This review focused on the non-axisymmetric endwall design as it is the more successful approach for reducing the secondary flows
A newly designed casing endwall with a guide groove was tested by Computational Fluid Dynamics (CFD) to improve the aerodynamic performance of a 1.5 stage axial turbine
Summary
Due to the world’s population growth and increased industrial activities, the demand for energy is increasing continuously and is projected to grow at a rising rate. The new casing design is introduced based on a novel surface definition method that draws from observations of the typical pattern of secondary flows over the turbine casing This is the first application of the current parametric casing design to the power turbines of a cryogenic plant. The commercial software Cycle–Tempo [24] is used to evaluate the change in the cycle performance from using power turbines with a new contoured casing This investigates the improvements in both the natural gas specific fuel consumption and the reduction in CO2 emissions that can be achieved by using axial turbines fitted with the optimized non-axisymmetric casing in this cryogenic cycle application
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