Experimental optimization of a free vortex propeller runner for micro hydro application

Journal Article · Tue Sep 15 00:00:00 EDT 2009 · Experimental Thermal and Fluid Science

DOI:https://doi.org/10.1016/J.EXPTHERMFLUSCI.2009.04.007· OSTI ID:21212899

Singh, Punit; Nestmann, Franz ^[1]

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1. Institute for Water and River Basin Management (IWG), University of Karlsruhe, Kaiser Str. 12, D 76128 Karlsruhe (Germany)

The turbine technology for low head application in the micro hydro range has been vastly neglected despite niche available in scattered regions of valley flows as well as in wastewater canals and other energy recovery schemes, where the available head does not exceed 2 meters. The goal of this study is to develop hydraulically optimized propeller turbines for the micro hydro range with a particular focus on ease of manufacture. This paper presents a wide range of geometrical optimization steps carried out on a propeller runner, whose blades have been designed using the free vortex theory, and operating with a gross head from 1.5 to 2 m and discharge of approximately 75 l/s. It further illustrates 3 stages of geometrical modifications carried out on the runner with an objective of optimizing the runner performance. These modifications comprised of changes to the tip angles (both at the runner inlet and exit) as well as the hub angles (at the runner inlet) of the runner blades. The paper also presents an interesting theoretical methodology to analyze the effects of each optimization stage. This method looks at the relative changes to shaft power and discharge at constant head and speed and gives wonderful insight as to how the internal parameters like Euler shaft work and runner hydraulic losses are behaving with respect to each optimization stage. It was found that the performance of the runner was very sensitive to changes to exit tip angle. At two levels of modification, the discharge increased in the range of 15-30%, while shaft power increased in the range of 12-45%, thus influencing the efficiency characteristics. The results of the runner inlet tip modification were very interesting in that a very significant rise of turbine efficiency was recorded from 55% to 74% at the best efficiency point, which was caused by a reduced discharge consumption as well as a higher power generation. It was also found that the optimization study on a propeller runner has reasonably validated the estimates of the free vortex theory despite small deviations. The final runner configuration demonstrated a maximum efficiency of 74% ({+-}1.8%), which is very encouraging from the perspectives of micro hydro application. The paper concludes with recommendations of a series of optimization steps to increase the efficiency of the runner. It also recommends the attempt of Computational Fluid Dynamics both as a validation and optimization tool for future research on propeller runners. (author)

• OSTI ID: 21212899
• Journal Information: Experimental Thermal and Fluid Science, Vol. 33, Issue 6; Other Information: Elsevier Ltd. All rights reserved; ISSN 0894-1777
• Country of Publication: United States
• Language: English

Related Subjects

13 HYDRO ENERGY
TURBINES
OPTIMIZATION
EFFICIENCY
VORTICES
MODIFICATIONS
WASTE WATER
COMPUTERIZED SIMULATION
FLUID MECHANICS
PERFORMANCE
VALIDATION
ENERGY RECOVERY
POWER GENERATION
CONFIGURATION
TURBINE BLADES
RECOMMENDATIONS
LOSSES
VELOCITY
LOW-HEAD HYDROELECTRIC POWER PLANTS
Free vortex
Propeller runner
Exit tip angle
Inlet tip angle