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Modeling an axial t...
Modeling an axial turbine: a parametric study
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- Kranenbarg, Jelle, 1996- (author)
- Luleå tekniska universitet,Strömningslära och experimentell mekanik
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Jonsson, P P (author)
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Mulu, B G (author)
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Cervantes, M J (author)
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(creator_code:org_t)
- English.
- Related links:
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https://urn.kb.se/re...
Abstract
Subject headings
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- Numerical simulations of axial hydraulic turbines away from the best efficiency point are challenging. Especially previous studies show difficulties predicting the tangential velocity at part-load operating conditions where the swirl is high. Moreover, there is a lack of knowledge about the ability of eddy viscosity turbulence models to predict the runner inter-blades flow. Therefore, a parametric study is performed to address these points. Specifically, the effects of the blade clearance, blade angle, flow rate, and different turbulence models are studied on these issues. Results are analyzed by comparing the predicted axial and tangential velocity profiles and torque to experimentally obtained values. In addition, the physical phenomena responsible for head losses are studied in detail. Results show that the model can predict the flow relatively well at optimal flow conditions with low swirl but has problems at part load; the tangential velocity between the runner blades is underestimated by ~20%. The undervalued head losses are the root cause. They result in an overestimation of the axial velocity and an overestimation of the torque which is connected to the runner extracting too much swirl from the flow, hence the low tangential velocity. Furthermore, the blade clearance is found to be important as high-velocity jets that originate from the clearances affect the flow field, especially close to the hub. The torque prediction is also affected. Therefore, the clearance should be carefully measured during an experimental campaign, especially at the leading and trailing edge. A small modeling error of 0.5° in the blade angle and a change of 3% in the flow rate significantly affect the tangential velocity and torque prediction. The studied parameters must be considered carefully when building a numerical model. However, part of the deviation can also be explained by the insensitivity of eddy viscosity models to anisotropy, swirling flow with streamline curvature and runner mesh density.
Subject headings
- TEKNIK OCH TEKNOLOGIER -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)
Keyword
- Axial turbine
- swirling flow
- off design operation
- URANS
- parametric study
- blade clearance
- head losses.
- Strömningslära
- Fluid Mechanics
Publication and Content Type
- vet (subject category)
- ovr (subject category)
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