An efficiency assessment analysis of a modified gravitational Pelton-wheel turbine (original) (raw)
Related papers
Flow in a Pelton Turbine Bucket: Numerical and Experimental Investigations
Journal of Fluids Engineering, 2006
The aim of the paper is to present the results of investigations conducted on the free surface flow in a Pelton turbine model bucket. Unsteady numerical simulations, based on the two-phase homogeneous model, are performed together with wall pressure measurements and flow visualizations. The results obtained allow defining five distinct zones in the bucket from the flow patterns and the pressure signal shapes. The results provided by the numerical simulation are compared for each zone. The flow patterns in the buckets are analyzed from the results. An investigation of the momentum transfer between the water particles and the bucket is performed, showing the regions of the bucket surface that contribute the most to the torque. The study is also conducted for the backside of the bucket, evidencing a probable Coanda interaction between the bucket cutout area and the water jet.
Numerical investigation of the interaction between jet and bucket in a Pelton turbine
This article presents the numerical investigation of the interaction between the jet and the bucket in a Pelton turbine. Unsteady numerical analyses were carried out on a single jet Pelton turbine installed in the north of Italy. A two-phase inhomogeneous model was used. Two different jet configurations were analysed and compared. In the first configuration, the interaction between the runner and an axial-symmetric jet characterized by a given velocity jet profile was investigated, whereas in the second configuration the runner was coupled with the needle nozzle and the final part of the penstock and the interaction between the jet and the bucket was analysed. A detailed analysis of the torque highlighted the influence of the shape of the water jet on the turbine losses and the influence of the stator on the efficiency of this type of hydraulic machines was shown. The numerical results were compared with the experimental data derived from the installation test of the turbine in order to validate the numerical analysis.
3 Hydraulic Turbines 3.1 INTRODUCTION
In a hydraulic turbine, water is used as the source of energy. Water or hydraulic turbines convert kinetic and potential energies of the water into mechanical power. The main types of turbines are (1) impulse and (2) reaction turbines. The predominant type of impulse machine is the Pelton wheel, which is suitable for a range of heads of about 150 -2,000 m. The reaction turbine is further subdivided into the Francis type, which is characterized by a radial flow impeller, and the Kaplan or propeller type, which is an axial-flow machine. In the sections that follow, each type of hydraulic turbine will be studied separately in terms of the velocity triangles, efficiencies, reaction, and method of operation.
Experimental investigation on impact of jet on flat and hemispherical vane
The objectives of the paper are to conduct an experimental investigation into the impact force generated by the impact of a jet of water on flat plate and hemispherical plate vanes to compare between experimental and theoretical forces which are exerted by the jet. The procedure for this experiment is to bring the weight cup in the initial position by applying weight when the flow rate is varied. It can be possible to repeat the same experiment by changing different target vanes. Moreover, the effect of water jet impact can be seen at a constant flow rate by changing the type of target vanes and applying different amounts of weights to bring the weight cup in the initial position. Here, the theoretical forces are depended upon weights applied on the weight cup and the experimental forces are depended on flow rate, nozzle exit velocity, impact velocity and shape of the vanes. Index terms-Impact of jet, flat vane, hemispherical vane, flow rate.
This paper presents the effect of head and bucket splitter angle on the power output of a pelton turbine (water turbine), to harmonize the gas turbine sector to enhance the power generation by the use of efficient Hydroelectric power generation systems. Analysis and simulation using experimental data were carried out on pelton turbine head conditions, high head and low flow with increased pressure delivered more energy on the bucket splitter which then generates a force in driving the wheel compared to the result obtained from low head and high flow operating conditions. A simulation program was developed using MatLab to simulate the force generated by the bucket as the water jet strikes the existing splitter angle (10 0 to 15 0) and predicted (1 0 to 25 0) splitter angles. Result shows that as volumetric flow rate was decreasing from 0.24 to 0.06 , as the volume of water decreases the pressure is increased. This increase in pressure influences the power delivered to the wheel by the jet of water. The jet of water causes the turbine speed to increase or decrease depending on the shape, size of bucket and the splitter which the jet strikes. The specific speed of the turbine increases and the shaft output also increases. It was equally noted that as the reservoir increases in elevation from 100m to 1000m, the hydraulic power in water fall (which is given a direction in a pipe line) increases the power delivered to the wheel from (4.4 to 5.05) x .
Head Loss Estimation for Water Jets from Flip Buckets
Water jet issued from flip bucket at the end of the spillway of a dam can be a threat for the stability and safety of the dam body due to subsequent scour at the impingement point. However, a strong jet from the flip bucket interacts with the surrounding air and develops into an aerated turbulent jet while the jet impact and scouring effect is reduced significantly. Aeration of the jet, at the same time, cause head losses along the trajectory. An experimental study is conducted to measure the trajectory lengths and investigate the effect of water depth in the river on the dynamic pressures acted on the river bed. The trajectory lengths with and without air entrainment are calculated using empirical equations and compared with the measurements. Head losses due to air entrainment are determined using the difference of the trajectory lengths with and without aeration, based on the projectile motion theory. Numerical simulation of the flow over the spillway, along the flip bucket and the jet trajectory is made and the results are compared with the experimental data. It is observed that trajectory lengths obtained from experiments, numerical simulation and empirical formulas are comparable with negligible differences. This allows us to combine alternate approaches to determine the trajectory lengths with and without air entrainment and estimate the head losses accordingly.
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.
Numerical flow analysis in a Pelton turbine bucket
The flow in the Pelton turbine bucket is three-dimensional, unsteady, turbulent, features a free surface, and is influenced by the rotation-induced forces. It is therefore difficult to investigate how the energy transfer takes place between the water flow and the buckets inner surface. The analysis of experimentally validated CFD results provides the opportunity to have a deep insight of the flow in the buckets. This paper presents the numerical investigations of the flow in a single bucket along a bucket period for an operating point close to the best efficiency of a 4-jet Pelton turbine model. The time history of the successive events occurring during the bucket period is first briefly presented. Then, the comparison of the pressure fields and the torque contribution for 5 different zones in the bucket is carried out. Significant discrepancies between the bucket pressure and torque distribution appear, highlighting that the regions, that are the most loaded in terms of mechanical strain, do not contribute the most to the bucket torque. This seems not to be related to the radial location of the bucket zones, but to the flow patterns, that are driven by the bucket design, and operating conditions. This study shows that an analysis of the bucket pressure and torque fields is paramount to quantitatively assess the effective energy transfer in the bucket.