Hydraulic performance prediction of a prototype four-nozzle Pelton turbine by entire flow path simulation

2018 ◽  
Vol 125 ◽  
pp. 270-282 ◽  
Author(s):  
Chongji Zeng ◽  
Yexiang Xiao ◽  
Yongyao Luo ◽  
Jin Zhang ◽  
Zhengwei Wang ◽  
...  
2016 ◽  
Vol 20 (8) ◽  
pp. 3441-3454 ◽  
Author(s):  
Anke Hildebrandt ◽  
Axel Kleidon ◽  
Marcel Bechmann

Abstract. By extracting bound water from the soil and lifting it to the canopy, root systems of vegetation perform work. Here we describe how root water uptake can be evaluated thermodynamically and demonstrate that this evaluation provides additional insights into the factors that impede root water uptake. We derive an expression that relates the energy export at the base of the root system to a sum of terms that reflect all fluxes and storage changes along the flow path in thermodynamic terms. We illustrate this thermodynamic formulation using an idealized setup of scenarios with a simple model. In these scenarios, we demonstrate why heterogeneity in soil water distribution and rooting properties affect the impediment of water flow even though the mean soil water content and rooting properties are the same across the scenarios. The effects of heterogeneity can clearly be identified in the thermodynamics of the system in terms of differences in dissipative losses and hydraulic energy, resulting in an earlier start of water limitation in the drying cycle. We conclude that this thermodynamic evaluation of root water uptake conveniently provides insights into the impediments of different processes along the entire flow path, which goes beyond resistances and also accounts for the role of heterogeneity in soil water distribution.


Author(s):  
S Sarkar

A method based on two-dimensional cascade theory is presented here to predict the characteristics of mixed flow impellers of high specific speed having a conical flow path. The theoretical characteristics are compared with the experimental results. Agreement is fairly good in the normal operating range, but some uncertainties exist in the assessment of appropriate slip factors and losses in the field of mixed flow rotor cascades, which need further studies. In the present case, the flow is assumed to be incompressible.


2014 ◽  
Vol 13 ◽  
pp. 28-35 ◽  
Author(s):  
Vishal Gupta ◽  
Ruchi Khare ◽  
Vishnu Prasad

Earlier only experimental techniques were used to predict the performance of turbines. With advanced numerical techniques and increase in processing power of computers, Computational Fluid Dynamics (CFD) has emerged as an effective tool for the performance prediction of Pelton hydraulic turbine involving multi-fluid  flow. Extensive work has been done for design optimization of reaction turbines using CFD. Now it is being extended for impulse turbines. The flow in reaction turbines involves only water as working medium, but in case of impulse turbines, water and air are working medium. The water jet issued from nozzle is surrounded by air and pressure around the jet and turbine is atmospheric. The performance of Pelton turbine depends upon the shape, size and quality of jet as well as shape of the buckets. In the present paper, the literature review on applications of CFD for performance prediction, design optimization of Pelton turbine have been discussed.DOI: http://dx.doi.org/10.3126/hn.v13i0.10042HYDRO NEPAL Journal of Water, Energy and EnvironmentIssue No. 13, July 2013Page: 28-35Uploaded date: 3/13/2014


Open Physics ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 285-304
Author(s):  
Chulin Yu ◽  
Youqiang Wang ◽  
Haiqing Zhang ◽  
Bingjun Gao ◽  
Yin He

Abstract Thermal performance prediction with high precision and low cost is always the need for designers of heat exchangers. Three typical design of experiments (DOE) known as Taguchi design method (TDM), Uniform design method (UDM), and Response surface method (RSM) are commonly used to reduce experimental cost. The radial basis function artificial neural network (RBF) based on different DOE is used to predict the thermal performance of two new parallel-flow shell and tube heat exchangers. The applicability and expense of ten different prediction methods (RBF + TDML9, RBF + TDML18, RBF + UDM, RBF + TDML9 + UDM, RBF + TDML18 + UDM, RBF + RSM, RBF + RSM + TDML9, RBF + RSM + TDML18, RBF + RSM + UDM, RSM) are discussed. The results show that the RBF + RSM is a very efficient method for the precise prediction of thermal-hydraulic performance: the minimum error is 2.17% for Nu and 5.30% for f. For RBF, it is not true that the more of train data, the more precision of the prediction. The parameter “spread” of RBF should be adjusted to optimize the prediction results. The prediction using RSM only can also obtain a good balance between precision and time cost with a maximum prediction error of 14.52%.


2015 ◽  
Vol 1 (1) ◽  
pp. 19 ◽  
Author(s):  
Azin Movahedi ◽  
Ali Delavari ◽  
Massoud Farahi

Using cascades and drops existing in flow path has a history of 3000 years. Particularly, Roman engineers employed stepped spillways with the same idea in several countries; however, there are few information about the hydraulic performance of aqueducts. Most of these channels have flat long cross sections with low torsions (variable slope) such that they can encompass cascade and steep spillways or dopshaft. Given that there are few studies conducted on dropshafts, the present paper attempted to discuss about such structures in flow path and water transmission lines as well as introducing the existing principles and relations and present, the obtained results of designing though Flow3D. The obtained error percentage was about 20% which is acceptable for numerical studies.


PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0253309
Author(s):  
Libin Tan ◽  
Yuejin Yuan ◽  
Man Zhang

In current research, the hydraulic performance prediction and optimization of an engine cooling water pump was conducted by computational fluid dynamic (CFD) analysis. Through CFD simulation, the pump head, shaft power and efficiency for the original pump at volume flow rate 25 L/min and impeller rotating speed 4231 r/min were 3.87 m, 66.7 W and 23.09% respectively. For improving hydraulic performance, an optimization study was carried out. After optimization, four potential optimized designs were put forward. The efficiency of the optimized design No.1 for engine cooling water pump was nearly 6% higher than that of the original pump model; and the head of the optimized design No.2 for engine cooling water pump was 9% higher than that of the original pump model. Under the condition of maintaining the pump head and considering comprehensive improvement effect, the optimized design No.3 was considered as the best design and selected as the test case for validating the optimum design. The hydraulic performance predictions for this optimum engine cooling water pump agreed well with experimental data at design condition with relative discrepancies of 2.9% and 5.5% for the pump head and pump efficiency, respectively. It proved that performance prediction calculation model and the automatic optimization model were effective. This research work can provide theoretical basis for the design, development and optimization of engine cooling water pump.


2011 ◽  
Vol 354-355 ◽  
pp. 599-603
Author(s):  
Xiao Xu Zhang ◽  
Si Qing Zhang ◽  
Li Xiang Zhang

Based on the good function for 3D modeling of Pro/E software, 3D geometry modeling for the entire flow passage of HLA351 which is the Francis turbine with long and short blades was realized by means of a series of methods of drawing from inside to outside, drawing from top to bottom, drawing lines from points, drawing surfaces from lines, and finally getting body from surfaces, so as to provide a reliable foundation for the future CFD calculation and performance prediction.


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