Inlet Velocity Profile Optimization of the Turbine 99 Draft Tube

Galván, Sergio; Reggio, Marcelo; Guibault, François

doi:10.1115/fedsm2013-16473

Cited by 6 publications

(9 citation statements)

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“…gradients, strong streamline curvature, swirl, and rotation, like the one in a draft tube. However, during an optimization process where fine details of flow characteristics are not required the standard turbulence model, κ − ε was confirmed as reliable and robust and able to study the effects of mildly swirling flow through the turbine draft tube [14]. These equations were solved using the commercial program FLUENT which is based on the Finite Volume Method and the pressure velocity coupling.…”

Section: Numerical Modelmentioning

confidence: 99%

Automatic shape optimization of a conical-duct diffuser using a distributed computing algorithm

Herrera

Galván

Camacho

et al. 2017

J Braz. Soc. Mech. Sci. Eng.

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overcome using a distributed computing evaluation established in a computational cluster. The methodology has allowed the location of the exact opening angle, improving approximately 1.2% the diffuser performance. A quantitative and qualitative analysis of the flow has been undertaken to understand how the optimum opening angle of a diffuser modifies the flow pattern to achieve the highest performance.

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Section: Numerical Modelmentioning

confidence: 99%

Automatic shape optimization of a conical-duct diffuser using a distributed computing algorithm

Herrera

Galván

Camacho

et al. 2017

J Braz. Soc. Mech. Sci. Eng.

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“…Such unfavorable flow results in considerable losses (amounted to 50% of the total) and significant local pressure drop leading to cavitation. 26 In conventional design practice, the meanline design concept is often used where the impeller is usually designed on the basis of energy transformation capacity from the hydraulic to mechanical without a consideration of exiting flow behavior, thus the vortex rope-like draft tube flow can occur even at design condition.…”

Section: Introductionmentioning

confidence: 99%

Swirling and cavitating flow suppression in a cryogenic liquid turbine expander through geometric optimization

Song

Sun

Wang

2015

Proceedings of the Institution of Mechanical Engineers, Part A:

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A single-stage cryogenic liquid turbine expander is developed as a replacement of Joule-Thompson valve in the internal compression air separation unit for energy-saving purpose. Flow analysis and optimization is conducted for the turbine expander. With the original geometry, static pressure drops gradually from the nozzle to impeller together with a 2.7 K temperature drop, which exhibits simultaneously a smooth throttling characteristic and cryogenic refrigeration effect. However, similar to the conventional hydraulic turbine, a vortex-rope is apparently formed around the draft tube centerline. It leads to considerable mechanical energy dissipation and, subsequently, a local pressure drop and temperature rise, which have made the turbine expander vulnerable to cavitation. The draft tube vortex swirling flow has been found to be sensitive to exit geometric shape of rotating impeller. To suppress the swirling flow and cavitation, design optimization of impeller geometric shape is further conducted with an efficient global optimization method developed by the authors, where in particular, an innovative optimization objective function and a simultaneous tuning of both impeller meridian profile and blade shape are incorporated. The former is a linear combination of the draft tube loss factor and normalized impeller exit static pressure. It depicts the draft tube swirling flow behavior and also captures somehow the cavitation flow physics. The latter permits a very flexible variation of the impeller geometry. Such a highly nonlinear problem is solved by the global optimization algorithm, in which the Kriging surrogate model is used but updated through adaptive sampling. It is demonstrated that with the optimized geometry, the vortex-rope like characteristics has diminished apparently and both scale and intensity of swirling region are reduced significantly. As a result, the low static pressure region has shrunk and the local temperature rise is reduced and, subsequently, the cavitation is effectively suppressed.

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“…(3). In [18][19] the high influence of the radial component on pressure distribution and pressure recovery was demonstrated computationally, in spite of the small magnitude of this velocity component.…”

Section: Inlet Velocity Profilementioning

confidence: 99%

“…However, the assembly of the optimization process represented a new challenge [18][19], since it was necessary to reduce the computational time of each simulation, to parameterize the inlet velocity profiles and to select the objective function to evaluate the draft tube performance.…”

Section: Introductionmentioning

confidence: 99%

Quantitative and qualitative analysis of the flow field development through T99 draft tube caused by optimized inlet velocity profiles

Galván

Reggio

Guibault

et al. 2015

International Journal of Fluid Machinery and Systems

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The effect of the inlet swirling flow in a hydraulic turbine draft tube is a very complex phenomenon, which has been extensively investigated both theoretically and experimentally. In fact, the finding of the optimal flow distribution at the draft tube inlet in order to get the best performance has remained a challenge. Thus, attempting to answer this question, it was assumed that through an automatic optimization process a Genetic Algorithm would be able to manage a parameterized inlet velocity profile in order to achieve the best flow field for a particular draft tube. As a result of the optimization process, it was possible to obtain different draft-tube flow structures generated by the automatic manipulation of parameterized inlet velocity profiles. Thus, this work develops a qualitative and quantitative analysis of these new draft tube flow field structures provoked by the redesigned inlet velocity profiles. The comparisons among the different flow fields obtained clearly illustrate the importance of the flow uniformity at the end of the conduit. Another important aspect has been the elimination of the re-circulating flow area which used to promote an adverse pressure gradient in the cone, deteriorating the pressure recovery effect. Thanks to the evolutionary optimization strategy, it has been possible to demonstrate that the optimized inlet velocity profile can suppress or mitigate, at least numerically, the undesirable draft tube flow characteristics. Finally, since there is only a single swirl number for which the objective function has been minimized, the energy loss factor might be slightly affected by the flow rate if the same relation of the axial-tangential velocity components is maintained, which makes it possible to scale the inlet velocity field to different operating points.

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Inlet Velocity Profile Optimization of the Turbine 99 Draft Tube

Cited by 6 publications

References 0 publications

Automatic shape optimization of a conical-duct diffuser using a distributed computing algorithm

Automatic shape optimization of a conical-duct diffuser using a distributed computing algorithm

Swirling and cavitating flow suppression in a cryogenic liquid turbine expander through geometric optimization

Quantitative and qualitative analysis of the flow field development through T99 draft tube caused by optimized inlet velocity profiles

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