Jet quality and Pelton efficiency (original) (raw)
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In the course of refurbishment of the HPP Rothenbrunnen with three horizontal twin Pelton turbines the injectors were replaced and the internals within the casing were modified. The runners were not replaced. Thermodynamic efficiency measurements before and after refurbishment provided proof of an efficiency increase of up to 1.4 percent, an excellent result for such minimal modifications. In addition to efficiency measurements also flow visualizations were performed installing a camera and lightening system within the casing of the turbine. The visualizations clearly showed a reduction of the splashing water in the casing of the turbine and less jet dispersion.
Effect of Jet Length on the Performance of Pelton Turbine : Distance Between Nozzle Exit and Runner
2016
Pelton turbine is the most commonly used high head impulse turbine with low discharge. For obtaining highest power output from runner one of the most important parameter is quality of jet which strikes bucket tangentially. The quality of jet and its impact work depends on the distance between the nozzle exit and runner along with its angle of strike. In the present paper, the effect of distance between the nozzle outlet and the runner on performance of Pelton turbine is discussed with the help of numerical technique. It is found that that axial flow of water is more for least (100 mm) distance while the radially inward and outward flow is more for larger (150 mm) distance between nozzle and runner.
Effect of Jet Shape on Flow and Torque Characteristics of Pelton Turbine Runner
2014
In Pelton turbine, the energy carried by water is converted into kinetic energy by providing nozzle at the end of penstock. The shape of jet affects the force and torque on the bucket and runner of turbine. The nozzle of circular cross section is commonly used. In this paper attempt has been made to study the effect of four different jet shapes on the flow and torque characteristics of Pelton turbine runner through numerical simulation.
Effect of Discharge Coefficient on Performance of Multi Jet Pelton Turbine Model
The conversion of hydraulic energy into mechanical energy takes place in hydraulic turbines. Further this energy is converted to electrical energy with the help of generators and then supplied to consumer. With increasing demand, efficiency of every machine plays vital role. When water is stored at very high head, hydraulic energy can be converted efficiently into mechanical energy with the help of Pelton turbine. The performance of Pelton turbine at designed and off-design points is important. Performance of turbo-machines is generally evaluated before installation with the help of model testing at designed and off design regimes. Now-a-days with advanced computers and numerical techniques, Computational Fluid Dynamics (CFD) has emerged as boon for optimisation of turbo-machines. In present work, performance analysis of existing six jet Pelton turbine at design and off design discharge has been numerically carried out using Ansys-CFX. The efficiency results are compared with available model test result and found to have close comparison. The variation in pressure distribution, water velocity and water distribution have also been obtained and discussed.
Performance analysis of Pelton turbine under different operating conditions: An experimental study
Ain Shams Engineering Journal, 2022
In this article, an experimental work has been carried out to examine the effect of varying operating conditions on performance of Pelton turbine. The experiments have been performed for various nozzle jet diameters (d), volume flowrate (Q) and pressure head (H). The experimental results display that the rise in d leads to reduce the input power due to decrease in H. For a certain nozzle diameter, the results indicated that the maximum brake power increases with increasing in Q owing to increase the torque and consequently, the optimum operational condition can be achieved when using smaller d and higher Q. The best turbine performance has been found when using d = 9.5 mm and Q = 85 L/min owing to produce higher efficiency and cover large range of wheel speed. The maximum efficiency of nozzle diameters 9.5 mm, 10.5 mm, 11.5 mm and 12.5 mm have been found equal 35.5%, 33%, 29.2% and 21.6%, respectively. Hence, d has inversely effect on the turbine performance. The data clearly also indicate that d and Q have substantially influences on the power that generated by turbine. By recognizing the effects of related parameters, it is now possible to generate a higher electric power in hydroelectric power plants that operated by using Pelton turbine.
A reference pelton turbine - design and efficiency measurements
IOP Conference Series: Earth and Environmental Science, 2014
The Pelton turbine has been subject to a varying degree of research interest since the debut of the technology over a century ago. Despite its age there are gaps in the knowledge concerning the flow mechanisms effecting the flow through the turbine. A Pelton turbine has been designed at the Waterpower Laboratory at NTNU. This has been done in connection to a Ph.D. project focusing on the flow in Pelton turbine buckets. The design of the turbine has been conducted using in-house knowledge in addition to some comments from a turbine producer. To describe the geometry multiple Bézier curves were used and the design strategy aimed to give a smooth and continuous gradient along the main flow directions in the bucket. The turbine has been designed for the operational conditions of the Pelton test rig installed at the Waterpower Laboratory which is a horizontal single jet test rig with a jet diameter(ds) of 35 mm. The diameter(D) of the runner was set to 513 mm and the width(W) of a bucket 114 mm, leading to a D /W ratio of 4.5. Manufacturing of the turbine has been carried out in aluminium and the turbine has undergone efficiency testing and visual inspection during operation at a head of 70 m. The turbine did not performed as expected and the maximum efficiency was found to be 77.75%. The low efficiency is mainly caused by a large amount of water leaving the bucket through the lip and hence transferring close to zero of its energy to the shaft. The reason for the large lip loss is discussed and two possible causes are found; the jet is located too close to the lip, and the inner surface of the bucket does not lead the water away from the lip. The turbine geometry and all data from both measurements and simulations will be available upon request in an effort to increase the amount of available data concerning Pelton turbines. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Numerical prediction of Pelton turbine efficiency
IOP Conference Series: Earth and Environmental Science, 2010
This paper presents a numerical analysis of flow in a 2 jet Pelton turbine with horizontal axis. The analysis was done for the model at several operating points in different operating regimes. The results were compared to the results of a test of the model. Analysis was performed using ANSYS CFX-12.1 computer code. A k-ω SST turbulent model was used. Free surface flow was modelled by two-phase homogeneous model. At first, a steady state analysis of flow in the distributor with two injectors was performed for several needle strokes. This provided us with data on flow energy losses in the distributor and the shape and velocity of jets. The second step was an unsteady analysis of the runner with jets. Torque on the shaft was then calculated from pressure distribution data. Averaged torque values are smaller than measured ones. Consequently, calculated turbine efficiency is also smaller than the measured values, the difference is about 4 %. The shape of the efficiency diagram conforms well to the measurements.
Numerical prediction of efficiency and cavitation for a Pelton turbine
IOP conference series, 2019
The first part of the paper illustrates the setup and the methodologies adopted for the numerical analysis of the flow in a 6-jet Pelton turbine with vertical axis. At first, steady state simulations of flow in a distributor for three positions of needle stroke were performed. The results were used for the calculation of flow energy losses, analysis of jet quality and setting inlet boundary conditions for runner analysis. Runner analysis was done only for the maximal opening. The purpose of runner analysis for the model size was efficiency prediction. Numerical results were validated with the results from the test rig. Simulations for the prototype were done in order to check whether water sheets evacuating from the buckets impact the previous bucket and whether there is any interaction between the evacuating water sheets and the incoming jets. Analysis was done also for one nozzle operation. In the second part of the paper cavitation prediction for the prototype of a 2-jet Pelton turbine is presented. The problem, because of computational cost, was reduced to five runner buckets and one jet. A multiphase flow consists of water, air and water vapour. For cavitation pitting the vapour has to stick to the buckets and mass transfer from vapour to water has to happen in a very short time without the presence of air. With detailed analysis of numerical results it was concluded that in this case no cavitation pitting is expected.
Detailed Analysis of Flow in Two Pelton Turbines with Efficiency and Cavitation Prediction
International Journal of Fluid Machinery and Systems, 2019
This paper presents results of the numerical analysis of two Pelton turbines: a 6-jet turbine for middle head and a 2jet turbine for high head. For the 6-jet turbine losses in manifold, quality of the jets and turbine efficiency were predicted and validated with the experimental data. Additional improvement of accuracy of efficiency prediction was obtained with cavitation modelling. It was also checked that there was no interaction between the evacuating water sheets and the incoming jets. For a 2-jet turbine cavitation prediction was done. Small vapour cavity at the inner side and a larger one at the back side of the bucket were observed. Detailed analysis of cavitation and condensation processes showed that the conditions for cavitation pitting were not fulfilled.
Flow Visualization - a Diagnosis Tool for Pelton Turbines
A series of video sequences of the jet development taken within one of the Pelton turbines of the Moccasin power plant, California, were quantitatively analyzed and compared to the theoretical jet dimensions. The results showed considerable divergence of the jet before entering the buckets of the Pelton runner. In addition unsteady flow structures on the jets surface were observed. These result in suboptimal interaction with the runner and lead to reduced efficiency. One of the sources of the jet's poor flow quality was identified in the injector design. Subsequently the nozzle geometry was modified. Efficiency measurements before and after the modifications showed considerable enhancement of performance, verifying the diagnosis as well as corroborating the measures taken to improve jet quality.