Performance Model of Archimedes Screw Hydro Turbines with Variable Fill Level

Lubitz, William David; Lyons, Murray; Simmons, Scott C.

doi:10.1061/(asce)hy.1943-7900.0000922

Cited by 72 publications

(62 citation statements)

References 9 publications

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“…Since the geometry of the screw is well-defined, the volume of water entrapped between the planes can be calculated by determining the volume of the region in the bucket beneath the observed fill level. This was done by numerical integration [7]. Once the volume of water in a bucket is known, the volumetric flow rate, an ideal version of the screw without a gap can be determined using the measured rotation speed of the screw.…”

Section: Methodsmentioning

confidence: 99%

Experimental Validation of Gap Leakage Flow Models in Archimedes Screw Generators

Kozyn

Lubitz

2015

Renewable Energy in the Service of Mankind Vol I

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Archimedes screw generators (ASGs) are a form of microhydro power generation that is increasingly being adopted as an alternative renewable energy source. ASGs operate efficiently, even as head approaches zero. A small gap must always exist between the trough and edge of the rotating screw flights to allow screw rotation. This leads to two categories of flow within the screw: the primary flow remains between the helical flights and causes screw rotation, while a secondary leakage flow occurs through the gaps at the screw edges. A high gap leakage flow reduces efficiency because this flow effectively bypasses the working parts of the screw and is lost. An accurate gap leakage model is an essential component of any ASG design model. Current gap leakage models are based on experience with Archimedes screw pumps or are derived from models assuming quasi-static flow through an opening. This experimental study measured the actual leakage flow in an operating laboratory-scale ASG. The fill heights within the buckets were measured using high-speed photography and used to determine bucket volume and therefore non-gap flow. The gap flow is determined based on the difference between the measured total flow through the system and the computed non-gap flow based on the measured fill height and screw speed. The uncertainty of the gap flow is relatively high, since it is calculated based on the difference between two variables with similar magnitude, one of which is calculated based on other measurements. The existing gap flow models did not accurately predict the experimental results. Gap flow was found to be dependent on screw rotation speed, with highest gap flows occurring at intermediate screw rotation speeds. Gap flow reduces to zero as screw rotation speed approaches the maximum possible speed. There is significant uncertainty in the existing gap flow models, and gap flow models constitute one of the largest sources of uncertainty when modeling the performance of ASGs.

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Section: Methodsmentioning

confidence: 99%

Experimental Validation of Gap Leakage Flow Models in Archimedes Screw Generators

Kozyn

Lubitz

2015

Renewable Energy in the Service of Mankind Vol I

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“…Hydropower development alters terrestrial and aquatic ecosystems, thereby impacting a multitude of ecological and biophysical processes and feedback mechanisms [43]. Moreover, with the continuous development of hydropower stations, the state support for small-scale hydropower stations is gradually increasing and water wheels and Archimedes screw have become the sustainable and economic technology, since their construction is simpler over turbines, their environmental impact is lower [47][48][49].…”

Section: Factors Analysis Of Sustainable Hydropower Developmentmentioning

confidence: 99%

Quantitative Evaluation of the Sustainable Development Capacity of Hydropower in China Based on Information Entropy

Liang

2018

Sustainability

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A sustainable hydropower development was developed by using the information entropy and the Brusselator principle and was applied to the hydropower data of China. Macro social economic and ecological environmental viewpoints were taken into account. The entropy change of each subsystem in a calendar year is analyzed to evaluate Chinese sustainable development capacity. It is found that the established model can effectively reflect the actual changes of sustainable development levels through the entropy change reaction system. Meanwhile, this model can demonstrate clearly how those indicators impact on the sustainable hydropower development and fill the absence of existing studies on sustainable hydropower development.

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“…Lower performances were found compared to an ASG with fixed trough, suggesting this diminution of performances is due to the friction between fluid and trough. About maximal ASG efficiencies in laboratory, Brada (1999) found results close to 80%; Lubitz, Lyons, and Simmons (2014) and Lashofer et al (2013) had results ranging between 80% and 90%, whereas field efficiencies are on the order of 75% on average. This could be attributable to the fact that rotation speeds are generally not optimal for a given discharge.…”

Section: V10 Released April 2015mentioning

confidence: 99%

“…Hence, it is hard to determine the screw performances for different flow rates at fixed rotational speed or vice-versa. Recently Lubitz et al (2014) proposed a model that takes into account the water fill level and the real screw geometry but friction losses are not included. Thus, by comparing their numerical and experimental results, the authors found a theoretical efficiency much higher than the experimental efficiency.…”

Section: V10 Released April 2015mentioning

confidence: 99%

Experimental investigation and performance analysis of Archimedes screw generator

Dellinger

Terfous²,

Garambois³

et al. 2016

Journal of Hydraulic Research

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Generation of renewable energy with Archimedes Screw Generators (ASG) transforming potential energy of a fluid flow into mechanical energy is a growing technology convenient for low-head hydraulic sites. This paper presents an improved theoretical model linking screw performances to screw geometry and flow conditions. This model takes into account leakages, friction losses and variable fill levels. The modeled values of torques and efficiencies are in fairly good agreement with experimental results obtained for a laboratory-scale screw. The downstream screw immersion is shown to impact ASG efficiency and an optimal level is determined. It is also found that fluid friction on screw is not negligible and a friction coefficient is calibrated experimentally. Interestingly, it is found that a single value is suitable for modeling performances under various flow conditions. Leakage phenomenon in under filling flow conditions and friction forces in complex turbulent flows could be further studied.

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Performance Model of Archimedes Screw Hydro Turbines with Variable Fill Level

Cited by 72 publications

References 9 publications

Experimental Validation of Gap Leakage Flow Models in Archimedes Screw Generators

Experimental Validation of Gap Leakage Flow Models in Archimedes Screw Generators

Quantitative Evaluation of the Sustainable Development Capacity of Hydropower in China Based on Information Entropy

Experimental investigation and performance analysis of Archimedes screw generator

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