Francis Type Research Articles

Water Turbine Guide Blades Effect of Quartz Sand on Abrasion Rate

Abstract Hydroelectric power plants with the aim of being used to generate electrical energy are mostly operated in areas with sedimentation content which can cause wear and tear on the components of the hydropower plant. This activity is emphasized to determine the effect of quartz sand on the rate of abrasion on the guide vanes of the Francis type water turbine. This activity was carried out using a water turbine guide blade abrasion test tool with a guide blade test object made of SUS 304 stainless steel material. The results are presented quantitatively and qualitatively, the greater the concentration and diameter of the quartz sand particles, the water pressure and the angle given at the same time, the greater the rate of abrasion that occurs in the francis type water turbine guide vane. The highest abrasion rate was 5.10 (g/cm2 x hour) in the angle variation test with a constant Q and a water: sand ratio of 70%: 30%.

Análisis del efecto de cavitación en una turbina hidráulica de tipo francis en condiciones de operación de la C.H. Chaglla

The performance of a hydropower plant depends on several parameters, i.e., the turbine type used, plant design, turbine classification, plant head, flow rate. All turbines are used for their best operation under the best level of efficiency with optimal values for their nominal head, water flow and turbine speed. However, under these conditions, the cavitation phenomenon occurs in the hydraulic turbine. It is only for the reason that the dynamic attribute of liquid flow becomes unstable with high pressure fluctuations. Cavitation is an unavoidable and unavoidable problem in hydraulic turbines. Cavitation destroys the performance of the turbines. When turbines operate at partial loads rather than their highest efficiency point, they experience cavitation to a greater extent. Francis turbines are designed to be operated in various conditions. The research objective was to analyze the cavitation occurrence in a Francis type turbine and how to minimize it, as a result a report was obtained on damages caused by the bubbles implosion on the surfaces of the turbine, especially in the impeller, at the exit waist edge of the intermediate zone in UG-1, present areas with cavitation wear between blade and blade 1-2. 3-4. 8-9. 11-12. 13-1. According to the inspection, the evolution of the cavitated areas is controlled and a slight detachment of material is observed, which does not compromise the useful life of the impeller. Likewise, for the impeller blades in the UG-2, cavitation wear areas occur between blade and blade 3-4. 9-10. 11-12; It is also controlled and slight material release is observed which does not compromise the useful life of the impeller. Regarding the wear of the blades in the impeller, we can indicate that in the UG2 there is 6.47 % accumulated wear, while in the UG1 there is 5.47 %. In the case of the guide vanes, the wear clearance with the highest incidence is in the UG2 with 0.692 mm of accumulated wear, while in the UG1 with 0.2595 mm.

Francis Type Turbine Runner Design and Comparison with Model Test Results

Cavitation wear and hydraulic efficiency decrease in hydroelectric power plants have frequently been the subject of various research and studies. A hydroelectric power plant built on the Kızılırmak River in Türkiye started operating in 1960 and has not been subjected to any large-scale rehabilitation work other than general maintenance until today. The power plant has 4 Francis-type turbines, each with a power of 32 MW. Due to cavitation wear of turbine runners over the years, performance loss, vibration, and noise problems have arisen. Moreover, the maximum turbine hydraulic efficiency, which was 92% in 1960, the year the power plant was commissioned, decreased to 87.9% according to the efficiency measurements carried out at the power plant in 2020. In this study, Computational Fluid Dynamics (CFD) analyses were accomplished with Reynolds averaged Navier Stokes (RANS) calculations for the redesign of the Francis-type turbine runner and finally checked by a model test according to IEC 60193. It was observed that the model test and CFD results were close to each other, especially at the best efficiency point. The maximum turbine hydraulic efficiency, which was calculated as 94.95% as a result of CFD analysis at the nominal head, was calculated as 95.19% by the model test. The x-blade shape created in the redesigned turbine runner blades ensured homogeneous pressure distribution and increased the hydraulic efficiency significantly.

Water hammer issues in refurbishment of a high-head hydropower plant equipped with Francis turbine

Refurbishment and upgrading of ageing hydropower plants contribute to increase of renewable energy share in modern electrical grid systems. The potential increase of discharge and flexibility of load variation may result in much higher dynamic loads on both refurbished and non-refurbished plant components during transient operating events. First, water hammer control strategies are outlined including operational scenarios, surge control devices, redesign of the pipeline components, or limitation of operating conditions. Water hammer models and solutions are briefly discussed in the light of their capability, availability and uncertainty. The core of the paper is devoted to investigations of water hammer effects in a high-head hydropower plant Piva, Montenegro which is currently in the final phase of refurbishment. The flow-passage system of the Piva HPP is comprised of the intake structure, followed by three parallel penstocks each with Francis type water turbine at the downstream end. The outlet part starts with three parallel draft tubes that are connected to a common lower orifice-type surge tank followed by tailrace tunnel and outlet structure. Computed and measured results for a selected emergency shut-down (ESD) of one turbine form full-load are compared and discussed. Then the validated computational model is used for simulation of ESDs for a wide operating range.

Experimental Francis Turbine Cavitation Performances of a Hydro-Energy Plant

An investigation is conducted on the Francis turbine’s cavitation characteristics and its influence on system hydraulic stability using two experimental methods, namely the flow visualization and acoustic emission methods. The investigated turbine is of Francis type with a 15-blade runner and has a specific speed of 202 rpm and a rated head of 30 m. Having tested the machine under a wide range of cavitation conditions, the gap cavitation is the earliest to develop as the cavitation coefficient gradually decreases and has no obvious effect on the machine’s external performance characteristics. The airfoil cavitation follows and causes the increase and decrease in machine flow rate and head, respectively, showing its drag reduction effect, where, at the same time, the pressure pulsation amplitude gets to its peak value. There is also the formation of constant cavitation zones and the involvement of an unsteady surge close to the wall of the draft tube’s cone. Pushing the cavitation coefficient to even lower values, there is the formation of an annular cavitation zone, accompanied by a sharp drop in cone pressure pulsation amplitudes while the former drag reduction effect disappears. The trend of noise is basically the same as that of pressure fluctuation, which confirms its trustworthiness when it comes to cavitation occurrence detection within Francis turbines.

The PICOHIDRO POWER ELECTRIC PLANT DESIGN IS EQUIPPED BY ELECTRONIC CONTROL SYSTEM (ECU)

Abstrak: There are many streams of water or rivers around us which are felt to be underutilized effectively. Therefore, it is necessary to develop Pico hydro technology as an alternative to power generation. Pico hydro usually produces low wattage so that it is not optimal for people to use in their daily lives. Therefore, the design of a power plant is designed that is equipped with an ECU control system as a water source control system that can produce greater electrical energy. The research method used is a pure experimental method to find out the results obtained are 300 watts by calculating the pressure sent to the ECU system. Technically, Pico hydro has several components in it, such as waterwheel water as a turbine, steering blade and generator. Pico hydro can be used as an alternative energy that utilizes the flow of water which can be used as an energy source. The Pico hydro generator used in this study is the Brantas River in Pendem Village, Karangploso District, Batu Malang City. With adequate water flow, using a Francis type water turbine, and using a 200Watt generator and controlled by the ECU system. From the test results obtained potential energy of 5880 (Nm), compressive energy of 2.107 (N/m2) pipe flow velocity (v) 7.668 (m/s) energy contained in water 45.67 (watts) Francis turbine efficiency 31.97% generator efficiency is 28.77% and the maximum power produced by a 200 watt generator is 29Volt

Unstable S-shaped characteristics of a pump-turbine unit in a lab-scale model

Unusual flow characteristics such as reverse flow, rotating stalls, flow recirculation, and stationary vortexes can induce high dynamic forces and torque variations on the entire system, creating a positive slope in the discharge-head curve. To avoid these problems, the present study investigates the hydrodynamic characteristics of a lab-scale model of a Francis type pump-turbine unit in the transition region. To verify the simulation, its results were compared with those of a laboratory-scale experiment performed over various operating ranges. The differences between the experimental and numerical speed, discharge, and torque factors were compared. The numerical analysis was well-matched the experimental tendencies in the overall operating and transition regions. The reliability of the simulations was within 4%. The unsteady RANS equations in the SAS–SST model were discretized for a detailed analysis of the pressure and internal flow characteristics. Under the runaway condition and low-discharge conditions, the frequency spectra of the pressure fluctuations were remarkable at low-frequency related to the rotating stall and blade passing frequency. These results represent a rotating stall with a frequency propagation of approximately 60% of the rotational speed of the runner. In case of the internal flow field, some blade loading distributions developed a positive shape while others developed a negative shape under the runaway condition. Although a rotating stall formed under the low-discharge condition, the form under this condition differed from that developed under runaway conditions, owing to backflow and the single stall cell.

Investigation of Mechanical Properties of Brass Francis Turbine Manufactured by Local Investment Casting Technique in Nepal

Most of the hydro turbines in Nepalese power plants are imported from foreign industries. Findings from the studies have shown that up to 60% of the 13,000 MW capacity hydropower projects under the survey stage in Nepal would need Francis type of turbine with unit size below 5 MW. To meet the demand for turbines, Nepal has imported turbines worth US$ 5,616,072. The imported turbines from foreign industries could not address local problems of Nepalese hydropower. In Nepal, due to the sediment-laden condition of rivers alternative design and manufacturing techniques of turbines are necessary. To provide the new manufacturing techniques of Francis turbine in Nepal local casting process can be a solution because metal casting is a hereditary profession in Nepal since ancient periods till now. Large-sized bronze cast bells that are placed in Nepalese temples were manufactured in ancient times without a proper theoretical study on them. This paper discusses the materials testing of investment cast and sand cast brass materials of 14 kW Francis runner of Turbine Testing Lab (TTL) for exploring the possibilities of manufacturing Francis turbine. Tensile, Compressive and Charpy impact tests were performed base on ASTM standards and also the microscopic study was conducted at Kathmandu university laboratory. These testing results can be helpful for further studies on alternate turbine manufacturing processes as well.

50MW급 프란시스 수차발전기 운영시 발생되는 진동 특성에 관한 연구

Vibration characteristics of the rotating machinery has been usually managed to facilitate the deterioration of the equipment and to prevent accident in advance. In a hydropower turbine, pressure pulsation characteristics to induce vibration is investigated during the model testing with a small scale model turbine for various operating conditions, and a prototype turbine is constructed to operate stably on the site. However, the model test has limitation that can’t be considered together with the vibration characteristics of a generator itself and of civil engineering structures for the building that support a turbine and a generator. Therefore, field tests of vibration for a hydroelectric power plant are carried out periodically, thereby maintaining reliability for safe operation of power generation facilities. In the study, the vibration of a Francis type hydroelectric power plant operated over 30 years and overhauled a year and a half ago was measured and its characteristics has been investigated. Displacement and velocity sensors were installed at appropriate positions to measure the vibration of the rotating shaft and bearing support of a turbine and a generator, and the vibration characteristics of a typical hydroelectric power plant have confirmed by analyzing the measurement results. The vibration characteristics of rotating shaft and non-rotating parts of the hydroelectric turbine have been analyzed to confirm the degree of aging of the plant. Vibration in the power plant building depending on the operating conditions was also measured to be large enough to sense, and its frequency characteristics were analyzed.

Numerical Study of a Pipe Extension Effect in Draft Tube on Hydraulic Turbine Performance

Draft tube of Francis type hydraulic turbine usually consists of: cone, elbow and diffuser. On the contrary, in some power stations an extra pipe should be added to the draft tube at the bottom of cone because of installation limitation. In this paper, this special case has been numerically studied. To this end CFD analysis was applied to simulate all parts of hydraulic turbine. A homogeneous multiphase model with Rayleigh-Plesset cavitation model was applied for presence of cavitation. The results reveal that the additional tube causes pressure drop and severe cavitation at the trailing edge of runner blades. Also, results showed that the efficiency reduces in comparison with original hill-diagram of model test in which this extension was not considered. With the removal of the extension tube, the efficiency increased significantly. The comparison of pressure recovery factors along draft tube, and theoretical investigation showed that the height of the draft tube is an important parameter and addition of an extra pipe will cause reduction in draft tube performance and increases the probability of occurrence of cavitation under the runner.

Numerical investigation of the effects of design parameters on hydraulic turbine guide vane design

Francis type hydraulic turbines that have a wide range of operating range for head and flow rates are commonly used in hydropower generation. Every power plant needs its custom designed turbine because the available head and flow rates, which are the main parameters to start the design process, are different for each plant. Guide vanes are the only movable parts of Francis turbines. They control the flow rate through the turbine. In this study, a generalized Computational Fluid Dynamics (CFD) aided design methodology is developed and applied to the design of the turbines of two different power plants. The effects of several parameters, including the shape of the guide vane profile, eccentricity, blade angles, overlapping percentage of the blades, number of guide vanes, and rotor-stator distance are examined. Results are investigated for each parameter in terms of flow physics and important outcomes are determined for turbine designers.

Microhydo potential in Gunung Pasang plantation Panti Jember East Java

Gunung Pasang plantation is located in Panti-Jember. The Gunung Pasang plantation actually already has a Francis type microhydro turbine with a power output of around 30 kW. However, this power is still too small when compared to energy needs in plantations which can reach 90 kW. The aim of this study is to find the potential of micro-hydro energy in the Gunung Pasang plantation as a reference for developing micro-hydro energy in the plantation. Potential studies are carried out by measuring the discharge using a current meter and measuring the difference of elevation using a automatic level and altimeter. The result of measurement of potential river flow discharge in the dry season is 0.202 cms. The difference in elevation measured at the first point is 54.19 meters and the second point is 113.09 meters. Microhydro power potential by taking a discharge 0.18 was calculated for the first point and the second as 69.61 kW and 145.27 kW, respectively. Utilisation of potential power in the second point was able to meet the electricity needs of the plantation. Economic feasibility analysis is needed if the micro hydro potential is to be developed.

Mini Hydropower Plant for Supporting the Renewable Resources at Madong, Toraja Utara Regency Sulawesi Selatan Province-Indonesia

Sulawesi Selatan is one of the provinces with high amount of electricality consumption. By the high amount of electricity consumption, electrical energy is needed to be provided. To provide the electricity we need the energy source. The river in Madong village, Toraja Utara Regency has the characteristic that potentially can be an energy source. To get the benefit from the Madong river, we need the study of designing and economic analysis. From analyzed data of the selected flood discharge (Q100) to be 488.55 m3.s-1 and the selected plant discharge (Q40) to be 13.18 m3.s-1. This hydropower was designed with a concrete and circle-shaped weir. There are the other components such as intake, feeder canal, settling basin, volume, headrace, fore bay and penstock. The penstock is using the welded steel material, with 2 m of diameter and 12 mm of thickness. Then, there is a tailrace that will transmit the water back to the river. The selected turbines are 2 units of Francis type, with the 12.59 MW power produced and 68.92 GWh energy produced in a year. The result of economic analysis, the project is feasible with BCR 1.29, NPV 135 Billion rupiahs, IRR 12.68%, and Payback period within 15.43 years.

Modeling Solid-State Phase Transformations of 13Cr-4Ni Steels in Welding Heat-Affected Zone

Fatigue damage is commonly encountered by operators of Francis type hydraulic turbine runners made of 13Cr-4Ni soft martensitic stainless steel. These large and complex welded casting assemblies are subjected to fatigue crack initiation and growth in the vicinity of their welded regions. It is well known that fatigue behavior is influenced by residual stresses and the microstructure. By including solid-state phase transformation models in welding simulations, phase distribution can be evaluated along with their respective volumetric change and their effect on residual stresses. Thus, it enables the assessment of welding process on fatigue crack behavior by numerical methods. This paper focuses on modeling solid-state phase transformations of 13Cr-4Ni soft martensitic stainless steel, used for manufacturing hydraulic turbine runners, occurring upon welding. It proposes to determine the material parameters of the models for both the austenitic and the martensitic transformation by nonisothermal dilatometry tests. The experiments are conducted in a quenching dilatometer with applied thermal conditions as experienced in the heat-affected zone of homogeneous welds. The activation energy and the kinetic parameters of the austenitic transformation from fully martensitic state are measured from the experimental results. The martensitic transformation modeling from a fully austenitic domain is also presented.

Development of wide operating range runner for Francis turbine upgrading

The proposed paper describes the upgrading procedure of the six units installed at HPP Stejaru in Romania in the sixties of the last century. The power plant is furnished with two identical 55 MW units and four identical 28 MW units. The scope of the upgrading was same for all units, to install new runner and wicket gate assembly into the existing spiral case and draft tube. The paper is focused especially on the procedure of the hydraulic design of the new Francis type runner due to demanding request for unusually wide range of operation for such type of turbine. The most challenging was the condition of adoption of wicket gate height, which was insufficient regarding specific speed of the new runner. The first CFD computations confirmed that the standard design of the runner was not able to fulfill the expected parameters. Therefore, the automatic mathematical designer driven optimization process was applied. The results of the optimization iteration process were confirmed during development tests and finally approved by additional acceptance tests carried out at the neutral laboratory as was required in tender specification. The performance features of the new turbine were found as excellent especially applicable for wide range of operation heads and outputs. Even in the marginal operation there are not expected any troubles with the cavitation or excessive pressure pulsations and turbine vibrations. The manufacturing process of the new components is now in the progress.

Air injection test on a Kaplan turbine: prototype - model comparison

Air injection is a very well-known resource to reduce pressure pulsation magnitude in turbines, especially on Francis type. In the case of large Kaplan designs, even when not so usual, it could be a solution to mitigate vibrations arising when tip vortex cavitation phenomenon becomes erosive and induces structural vibrations. In order to study this alternative, aeration tests were performed on a Kaplan turbine at model and prototype scales. The research was focused on efficiency of different air flow rates injected in reducing vibrations, especially at the draft tube and the discharge ring and also in the efficiency drop magnitude. It was found that results on both scales presents the same trend in particular for vibration levels at the discharge ring. The efficiency drop was overestimated on model tests while on prototype were less than 0.2 % for all power output. On prototype, air has a beneficial effect in reducing pressure fluctuations up to 0.2 ‰ of air flow rate. On model high speed image computing helped to quantify the volume of tip vortex cavitation that is strongly correlated with the vibration level. The hydrophone measurements did not capture the cavitation intensity when air is injected, however on prototype, it was detected by a sonometer installed at the draft tube access gallery.

Simulation-based design and optimization of Francis turbine runners by using multiple types of metamodels

In recent years, optimization started to become popular in several engineering disciplines such as aerospace, automotive and turbomachinery. Optimization is also a powerful tool in hydraulic turbine industry to find the best performance of turbines and their sub-elements. However, direct application of the optimization techniques in design of hydraulic turbines is impractical due to the requirement of performing computationally expensive analysis of turbines many times during optimization. Metamodels (or surrogate models) that can provide fast response predictions and mimic the behavior of nonlinear simulation models provide a remedy. In this study, simulation-based design of Francis type turbine runner is performed by following a metamodel-based optimization approach that uses multiple types of metamodels. A previously developed computational fluid dynamics-based methodology is integrated to the optimization process, and the results are compared to the results obtained from on-going computational fluid dynamics studies. The results show that, compared to the conventional methods such as computational fluid dynamics-based methods, metamodel-based optimization can shorten the design process time by a factor of 9.2. In addition, with the help of optimization, turbine performance is increased while cavitation on the turbine blades, which can be harmful for the turbine and reduce its lifespan, is reduced.

Failure analysis of runner blades in a Francis hydraulic turbine — Case study

Failure analysis of the moving blades in the runner of a 200MW Francis type hydraulic turbine is presented. Analysis consisted of the determination of the pressure on the blade surface using computational fluid dynamics (CFD), the calculation of the stress distribution in the turbine runner at different operating conditions using the finite element method, and a simplified fatigue analysis. Natural vibration modes in water and Von Kármán's vortex frequencies serve as reference. Results showed a large concentration of stresses in the T-joint between the blade and crown where the cracks originated. Finally, possible causes of the damage are discussed.

Determination of the Effect of the Angle of the Wicket Gate on Turbine Efficiency in Francis Type Turbines by CFD Analysis

Determination of the Effect of the Angle of the Wicket Gate on Turbine Efficiency in Francis Type Turbines by CFD Analysis

Prediction of Turbine Needed For Future Hydropower Projects in Nepal

As Nepal holds significant potential for a prosperous future market in hydropower and associated business developments, the Turbine Testing Lab (TTL) at Kathmandu University, Nepal has carried out a project that focuses on scientific studies to identify optimal turbine requirements for various hydropower projects. We collected and analyzed basic design data available from different sources to identify the turbine design specifications for the upcoming hydropower projects. As a result, we developed a computer program as a tool to support this work. Findings from the current studies have shown that up to 60% of the 13000 MW capacity hydropower projects under survey stage in Nepal would need Francis type of turbine with unit size below 5 MW. This finding is also supportive to establish a basis for developing turbine manufacturing and maintenance competence in Nepal from business perspectives.DOI: http://dx.doi.org/10.3126/hn.v14i0.11250HYDRO Nepal JournalJournal of Water, Energy and EnvironmentVolume: 14, 2014 JanuaryPage: 23-26