Investigation of Flow Separation in a Diffuser of a Bulb Turbine

Duquesne, Pierre; Maciel, Yvan; Deschênes, Claire

doi:10.1115/1.4031254

Cited by 19 publications

(4 citation statements)

References 18 publications

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“…For diffusers, flow separation can induce blockage zones that decrease the pressure recuperation. For example, flow separation in hydraulics bulb turbines is suspected to induce an important and sudden drop-off of the efficiency curves with operating fluctuations near the best efficient point [3]. In other cases, the flow separation is not periodic in the diffuser and induces a non-periodic flow, as observed in a hydraulic turbine by [4] and in a centrifugal compressor by [5].…”

Section: Introductionmentioning

confidence: 99%

“…All in all, the skin-friction-lines analysis helps to pinpoint the origin of the flow separation at the wall to then ease the global 3D field examination. This technique is used in turbomachinery as well (for example, [3,4,10]), but according to the authors' knowledge, its adaptation for internal flow has not been clearly exposed yet. However, it is not straightforward.…”

Section: Introductionmentioning

confidence: 99%

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Topology Rule-Based Methodology for Flow Separation Analysis in Turbomachinery

Duquesne

Chanéac

Mondin

et al. 2022

IJTPP

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Boundary-layer flow separation is a common flow feature in many engineering applications. The consequences of flow separation in turbomachinery can be disastrous in terms of performance, stability and noise. In this context, flow separation is particularly difficult to understand because of its three-dimensional and confined aspects. Analyzing the skin friction lines is one key point to understanding and controlling this phenomenon. In the case of separation, the flow at the wall agglutinates around a manifold while the fluid from the boundary layer is ejected toward the flow away from the wall. The analysis of a three-dimensional separation zone based on topology is well addressed for a simple geometry. This paper aims at providing simple rules and methods, with a clear vocabulary based on mathematical background, to conduct a similar analysis with complex turbomachinery geometry (to understand a surface with a high genus). Such an analysis relies on physical principles that help in understanding the mechanisms of flow separation on complex geometries. This paper includes numerous typical turbomachinery surfaces: the stator row, vaneless diffuser, vaned diffuser, axial rotor and shrouded and unshrouded centrifugal impeller. Thanks to surface homeomorphisms, the generic examples presented can easily be converted into realistic shapes. Furthermore, classical turbomachinery problems are also addressed, such as periodicity or rotor clearance. In the last section, the proposed methodology is conducted on a radial diffuser of an industrial compressor. The flow at the wall is extracted from LES computations. This study presents the different closed separation zones in a high-efficiency operating condition.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Topology Rule-Based Methodology for Flow Separation Analysis in Turbomachinery

Duquesne

Chanéac

Mondin

et al. 2022

IJTPP

Self Cite

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“…They are also often succeeding 1 3 combustion chambers (Fishenden and Stevens 1977) in jet engines in the aeronautics and automotive industry. Diffusers are used in the form of draft tubes of hydro turbines such as bulb (Duquesne et al 2016), Kaplan (Daniels et al 2020) or Francis turbines (Zhang et al 2009). The industry's infatuation with optimising diffuser designs with the goal to minimise energy losses has led to a sea of experimental research in recent decades with the goal to further understand the key parameters affecting the diffuser efficiency.…”

Section: Introductionmentioning

confidence: 99%

Flow Separation Dynamics in Three-Dimensional Asymmetric Diffusers

Hajaali

Stoesser

2021

Flow Turbulence Combust

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The mean and instantaneous flow separation of two different three-dimensional asymmetric diffusers is analysed using the data of large-eddy simulations. The geometry of both diffusers under investigation is based on the experimental configuration of Cherry et al. (Int J Heat Fluid Flow 29(3):803–811, 2008). The two diffusers feature similar area ratios of $$\mathrm{AR}=4.8$$ AR = 4.8 and $$\mathrm{AR}=4.5$$ AR = 4.5 while exhibiting differing asymmetric expansion ratios of $$\mathrm{AER}=4.5$$ AER = 4.5 or $$\mathrm{AER}=2.0$$ AER = 2.0 , respectively. The Reynolds number based on the averaged inlet velocity and height of the inlet duct is approximately $${\textit{Re}}=10{,}000$$ Re = 10 , 000 . The time-averaged flow in both diffusers in terms of streamwise velocity profiles or the size and location of the mean backflow region are validated using experimental data. In general good agreement of simulated results with the experimental data is found. Further quantification of the flow separation behaviour and unsteadiness using the backflow coefficient reveals the volume portion in which the instantaneous reversal flow evolves. This new approach investigates the cumulative fractional volume occupied by the instantaneous backflow throughout the simulation, a power density spectra analysis of their time series reveals the periodicity of the growth and reduction phases of the flow separation within the diffusers. The dominating turbulent events responsible for the formation of the energy-containing motions including ejection and sweep are examined using the quadrant analysis at various locations. Finally, isourfaces of the Q-criterion visualise the instantaneous flow and the origin and fate of coherent structures in both diffusers.

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“…Nishi et al, used PIV to investigate internal flow structure of small axial hydro turbine [7]. Duquesne et al, investigated flow separation in a diffuser of bulb turbine using PIV [8]. Iliescu et al, measured velocity profiles in side draft-tube using PIV [9].…”

Section: Introductionmentioning

confidence: 99%

Study on the Application of Particle Image Velocimetry with Resin and Rhodamine B as Alternative Seeding Particles in Pico Hydro Cross Flow Hydro Turbine

Warjito

Wijaya

Budiarso

et al. 2021

ARFMTS

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One of the solutions to overcome the lack of electricity problem in rural area is Crossflow pico-scale hydropower. In improving cross-flow turbine performance, understanding fluid phenomena is needed. Particle image velocimetry (PIV) measurement is one of the methods used to visualize the fluid flow phenomena inside the turbine. Expensive price of seeding particle leads to find the solution for this PIV method. The objective of this study is to use a cheap seeding particle from cheaper materials, mainly resin and rhodamine B. Besides that, in this study, PIV measurement is compared to 2D computational fluid dynamics (CFD) with multiphase volume of fluid model. From the results, several phenomenon can be observed at both of the methods (PIV and CFD) such as separation in the blade tip. Therefore, this study showed that an inexpensive material resin and rhodamine B as a seeding particle has a potential and ability to represent flow inside pico-hydro cross-flow turbine.

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Investigation of Flow Separation in a Diffuser of a Bulb Turbine

Cited by 19 publications

References 18 publications

Topology Rule-Based Methodology for Flow Separation Analysis in Turbomachinery

Topology Rule-Based Methodology for Flow Separation Analysis in Turbomachinery

Flow Separation Dynamics in Three-Dimensional Asymmetric Diffusers

Study on the Application of Particle Image Velocimetry with Resin and Rhodamine B as Alternative Seeding Particles in Pico Hydro Cross Flow Hydro Turbine

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