Reaction Turbines Research Articles

CAVITATION EROSION IN FRANCIS TURBINES

The phenomenon of secondary flow is a global problem that causes cavitation erosion in hydraulic equipment. Cavitation is a phenomenon of localised corrosion of the metal surface leading to instability and highly uneven flow behaviour with a consequent excessive noise, vibration, and decreased efficiency in Francis, Kaplan, and other turbines. Both Kaplan and Francis turbines are reaction turbines. Francis turbines (FT) are used worldwide due to their relatively compact design, high efficiency, and operation underwater at heights ranging from 100 to 300 m with an efficiency ranging from 90% to 95%. The article analyses the latest relevant research conducted by various researchers on different turbine components. The analysis shows that this type of erosion depends on flow characteristics, surface, and properties of the material eroding. Tools for design optimisation, cavitation erosion, and well-conducted experiments will provide results for identifying and reducing erosion. Although some researchers conducted experimental work to study the effect of cavitation erosion, literature on computational fluid dynamics (CFD) is very scarce. Over the past two decades, experts have been applying CFD methods to detect cavitation by examining areas where the pressure is below the vapour pressure with a single-phase model. Most studies do not consider the impact of cavitation bubbles on the flow field. However, these methods cannot provide detailed information, such as the impact of cavitation on efficiency or a more accurate prediction of the cavitation bubble size. Some researchers use cavitation inducers and some of the latest visualisation methods as experimental tools to study cavitation phenomena. In the last decade, a numerical methodology has been widely used in research and experiments, yielding significant results. Studying cavitation erosion in hydroelectric turbine systems presents a complex challenge for future research. Many parameters and features still require further investigation. All the discussed studies have established that cavitation phenomena require state-of-the-art equipment for their detection and visualisation. Moreover, more work is necessary for the numerical assessment of cavitation. Keywords: hydroelectric turbine, cavitation erosion, computational fluid dynamics.

Effect and mechanism of erosion in Pelton turbine and case studies—A review

Pelton turbines are widely used in hydropower stations located in mountainous regions, especially with water head drop of more than 2000 m. Due to the complex structure and working principle of the turbine, the flow is more complicated than reaction turbines, making the numerical simulation more difficult. The impulse action causes the occurrence of erosion phenomena in Pelton turbines, which will directly decrease the hydraulic efficiency and reduce the turbine's life. For investigating the erosion characteristics, computational fluid dynamics is widely used on variegated platforms according to their unique advantage. Thus, different platforms are introduced and compared in solving the multi-phase flow using a discrete element method or the other meshless methods. In addition, the erosion mechanism is studied and classified in different aspects such as impact angle and impact velocity. However, unlike the feasibility of numerical simulations, experimental work on the erosion mechanism is still challenging to reproduce. Furthermore, the state of experimental research is discussed by listing the various major facilities in operation and comparing their methods of experimental analysis. Case studies all over the world provide a very rich database of erosion patterns which would be highly useful in validation and verification of simulation and experimental results. Studies have shown that particle parameters, such as size, concentration, shape, velocity, and the interaction between particles and material surfaces, significantly impact the erosion of Pelton turbines. In response to this erosion, upgrading materials and implementing geometric optimization have proven to be effective strategies.

A System and Method for Retrieving Energy Potential through Irrigation Gate of an Agricultural Dependent Hydro Power Plant

The modern economics depends on the electrical energy and the share of decarburized electrical energy is the base of 2050 net zero emission targets. Non-fossil fuel and fossil fuel energy resources are the integral part of net zero energy system. The net zero emission activities are affected by increasing demand of electricity and its related CO2 emission in 2021. The contribution of 41.4% of renewable energy as compared to 56.8% of non-renewable energy in the year of 2023 at national level necessities attention of green sources of energy like solar, wind, hydro, waste to energy, small hydropower, etc. Hydropower is one of the reliable backbones of clean energy system which should be used effectively for power generation. The turbine dependent hydropower plant of 45-60 years old requires renovation, modernization, uprating and digitization (RMUD) to resolve socio-economic concerns and increasing demands. This scenario imposes the need of finding solution in existing hydropower plant than investing on new unit. Both high and low discharge should be potentially used for power generation to improve the capacity factor of the plant. Therefore, present work focusses on improving capacity factor of an existing agricultural dependent hydro power plants having reaction type turbine. Reaction turbines operates at high flow and low/medium head conditions. The operational conditions of low flow and low head for reaction turbines may lead to noise, vibration and directed to major catastrophic failure of turbines. There is a need of utilizing the energy potentials balancing power generation and irrigation even during low flow releases. Thus, this paper is an attempt to a design and develop a modified irrigation gate with sliding gate and mini hydropower system at the inlet of existing irrigation diversion gate. Stochastic nature of flows through different hydraulic structures is to be addressed by this modification. A case study of an irrigation dependent hydropower plant Dhom (2X1 MW), MAHAGENCO, Satara, Maharashtra having TWO irrigation gates have been considered. In addition to 2MW, the suggested design can generate 680kW by average irrigation releases of 2.47m3/sec through each gate. The suggested model can be used on any hydropower plant and canal locations.

Improved Operation and Method of a Reaction Turbine for Enhancing Net Head

In a reaction turbine, the amount of energy harnessed depends on discharge and net head. The two variables are mutually exclusive or in which one variable is dependent on another and in which the increase of head will decrease the flow required by the hydraulic turbine or vice versa. There is a need for improving the existing hydropower system and the method for enhancing the net head of a reaction turbine is essential. The present invention will hold the key in novelty during the design and excavation of tail race channel or for Renovation, Modernization and Uprating (RMU) of the existing old hydro power plants. The proper redesign of tail water channel, selecting suitable width, depth and by adopting flow regulating means will yield improve the net head substantially and thereby saving of discharge to an extent. The present invention enables to improve net head and saves discharge considerably, thereby enhancing the capacity factor of the hydro plant. The novelty and the innovation is granted an Indian patent for the method of enhancing the net head of a reaction turbines.

Experimental Investigation into Performance of Laval Nozzles for Reaction Turbines

Experimental Investigation into Performance of Laval Nozzles for Reaction Turbines

Optimization Design and Simulation Approach of an Axial Inward Flow Reaction Turbine Incorporating with Organic Rankine Cycle

The demand for sustainable and efficient energy conversion systems has led to the exploration of various turbines design and working fluids. This study focuses on the design and simulation investigation of an axial inward flow reaction turbine utilizing organic fluids as the working medium. Organic fluids have gained attention due to their favourable themodynamic properties and low environmental impact. The selection process for the working fluid takes into consideration factors such as temperature limitations fluids availability and efficiency. The design process begins with a thorough analysis of the fundamental principles govering inward flow reaction turbines. Fluids flow path, blade profiles, the interaction between the fluid and these blades are carefully studied. Design parameters such as specific spedd, specific diameter and specific speed coefficient are determind to ensure optimal turbine performance

Investigate air turbines performance for power generation by tidal waves in the river: A review

The phenomenon of climate change resulting from the increase of global warming has become one of the main problems facing the world. Where researchers and specialists have worked for many years to find a solution that reduces this phenomenon and limits its risks. Clean energy is likely an alternative to fossil fuel sources, which are the main source of global warming. One of the clean energy sources is ocean wave energy, which is a huge and untapped energy source, despite the possibility of extracting large amounts of energy from waves. This paper focuses on the study of deep-sea turbines and their results. A study was conducted on the capture chamber. The turbines are driven and generate electricity by using a wave energy harvesting system (oscillating water column). Reaction turbines (impulse and Wells turbines) are tested and evaluated for performance in an oscillating water column system. Reaction turbines have a narrow operating range, and higher peak efficiencies. In contrast, turbines that have a greater operating range and lower peak efficiency are impulse turbines. Wells stator turbine has the highest efficiency while a variable pitch axial impulse turbine has the widest operating range. Better efficiency possessed by turbines with optimized geometry than other turbines.

Mathematic Modelling of a Reversible Hydropower System: Dynamic Effects in Turbine Mode

Over the past few years, there has been significant interest in the importance of reversible hydro-pumping systems due to their favorable flexibility and economic and environmental characteristics. When designing reversible lines, it is crucial to consider dynamic effects and corresponding extreme pressures that may occur during normal and emergency operating scenarios. This research describes essentially the turbine operation, although various boundary elements are mathematically formulated and presented to provide an understanding of the system complexity. Different numerical approaches are presented, based on the 1D method of characteristics (MOC) for the long hydraulic circuit, the dynamic turbine runner simulation technique for the behavior of the power station in turbine mode and the interaction with the fluid in the penstock, and a CFD model (2D and 3D) to analyze the flow behavior crossing the runner through the velocity fields and pressure contours. Additionally, the simulation results have been validated by experimental tests on different setups characterized by long conveyance systems, consisting of a small scale of pumps as turbines (at IST laboratory) and classical reaction turbines (at LNEC laboratory). Mathematical models, together with an intensive campaign of experiments, allow for the estimation of dynamic effects related to the extreme transient pressures, the fluid-structure interaction with rotational speed variation, and the change in the flow. In some cases, the runaway conditions can cause an overspeed of 2–2.5 of the rated rotational speed (NR) and an overpressure of 40–65% of the rated head (HR), showing significant impacts on the pressure wave propagation along the entire hydraulic circuit. Sensitivity analyses based on systematic numerical simulations of PATs (radial and axial types) and reaction turbines (Francis and Kaplan types) and comparisons with experiments are discussed. These evaluations demonstrate that the full-load rejection scenario can be dangerous for turbomachinery with low specific-speed (ns) values, in particular when associated with long penstocks and fast guide vane (or control valve) closing maneuver.

Pilot study on renovation, modernization and uprating of agricultural dependent power plant

Hydro energy is one of the most valuable, rich, pliable inexhaustible energy resources in the world. Furtherance to the India’s commitment and pledge at Conference of the Parties (COP) 26 at Glasgow in 2021 calls to cut emissions to net zero by 2070, reduce the carbon emission by one billion tonnes by 2030 and improve the share of renewables in the energy mix to 50 % among others. Scientists and researchers needs to play a major role in achieving net zero emission to reduce the climate change impacts. In India, the share of hydro power is 34.1 % among the overall renewable energy of 150 GW. Hence, hydro power is an important area for Renovation, Modernization and Uprating (RMU) of the existing hydro capacities and it leads to limiting considerable carbon emission to an extent. This research paper focuses on storage reservoir where irrigation to hydro power water transfer is important. A balance of power generation and irrigation is at the highest priority attaining optimum social benefits. The reaction turbines are operated at high flow and low/medium head conditions for agricultural dependant power plant with consideration to Irrigation, drinking, flora and fauna. The restrictions imposed on the reaction turbines while operation under low load and low flow conditions leads to cavitation. The operation conditions under low flow and low load of reaction turbines may lead to noise, vibration and directed to major catastrophic failure of turbines. The likely outcome of same leads to considerable loss of energy generation. In addition to the above, a typical hydro power plant consumes 0.3 to 0.5 % of maximum power capacity as an internal load for lighting and other auxiliary systems. This paper emphasizes in utilizing the unused energy potential during the low and high water releases from irrigation dependent hydro power plant on renovation, modernization and uprating (RMU) of existing hydropower station. An irrigation dependent hydropower plant Dhom (2X1 MW), MAHAGENCO, Satara, Maharastra has been considered for study in order to use the available energy potential optimally. The improvement of capacity factor from 0.315 to 0.46 and additional power generation of 300 kW creates the opportunity to apply RMU in existing hydropower plant successfully.

Reformulation of the pressure-time method for application without flow rate cut-off

The paper presents a reformulation of the standard pressure-time method for flow rate measurement in closed conduits. According to the IEC 60041 standard, the method is used with turbines flow rate cut-off. Its current formulation requires complete closure of the turbine shut-off device, generally guide vanes for reaction turbines and valves for impulse turbines, which may cause wear and tear on the machine. Any leakage through the closed shut-off device also needs to be measured. In the present work, a new formulation of the pressure-time method is derived, extending the actual use. The newly formulated method allows the determination of the flow rate at any instant of time from a load variation and, thus, the initial, incremental, and final flow rate. The load variation may be positive or negative. Measurements of any leakage flow are eliminated. Numerical and experimental cases are used to assess the validity and applicability of the proposed formulation. The numerical results demonstrate the correctness of the derivation. The experimental results exemplify the applicability of the method. Limitations of the derived methodology are discussed.

Investigation of the performance and flow characteristics of two-phase reaction turbines in total flow geothermal systems

In a total flow geothermal system, the two-phase turbine can generate output power and recover fresh water for the water-deficient area. The performance of the two-phase turbine under various working conditions is significantly affected by operation parameters of the geothermal system. This paper presented performance evaluation methods of two-phase turbines, including one-dimensional (1D) method, two-dimensional (2D) method and three-dimensional (3D) method. The 1D method was a fast iteration approach and could reflect average flow parameters along the impeller channel. The 2D method included nonuniform effects in the rotational direction and the 3D method could derive the complete 3D flow in the channel using CFD methods. The three models were validated with experimental results under various rotational speeds. Compared with the 3D method, the 1D method and the 2D method could significantly reduce computational time. The performance of the two-phase reaction turbine was evaluated under various working conditions. A correction method based on 1D and 3D results was proposed to generate the performance map and evaluate the influence of operation parameters of the geothermal system on the turbine performance. Proposed methods and analysis can be widely used in the design, selection and operation of two-phase reaction turbines for various thermal systems.

Biomass cogeneration plants integrated into poultry slaughterhouses for reducing industry costs with energy

A technical and economic feasibility analysis was performed concerning biomass cogeneration to supply the thermal and electricity demands of poultry slaughterhouses. The analysis considers measured data referring to the annual energy consumption from an existing industry as well as the characteristics of equipment available in the Brazilian market. The cogeneration plant is equipped with a water tube steam generator and a condensing-extraction steam turbine in a Rankine cycle. Four different configurations were evaluated, including impulse and reaction turbines at two steam pressure/temperature levels (43 bar / 450 °C and 68 bar / 520 °C). A steady state full load operation is considered at cogeneration mode on the weekdays and at Rankine power plant mode on the weekends, when there is no process steam consumption. The technical analysis pointed out the reaction turbine at 68 bar / 520 ºC as the best alternative, leading to the highest overall efficiency. In addition, this plant configuration showed economic advantages represented by an Internal Rate of Return (IRR) of 21%, a Net Present Value (NPV) of US$ 10.93 million, and a payback time of 6 years, enabling a reduction on the industrial cost with energy in the slaughterhouse to 19 US$/ton of product (-30% in comparison to the base case). Finally, the calculated LCOE of 73 US$/MWh was lower than the current price of the electricity in the market, indicating potential economic feasibility of the proposed concept.

Investigation on rotor jet interference in a hydraulic reaction turbine for low head low flow water conditions

Abstract The focus of this paper is to investigate the issue of water jet interference, which is a common flaw in simple reaction turbines. When the turbine’s wall crosses the water jet coming from another nozzle, this is known as jet interference. The governing equations are also used to analyse the Z-Blade simple water reaction turbine for an ideal and practical example, based on the principles of mass-, impulses and energy conservation. Various evaluations of real and potential operating losses for low-head (3–5 m) and low-flow (3 L/s and below) water resources have been conducted. According to experimental data, the Z-Blade turbine Type B achieves the maximum rotational speeds at 450 rpm, followed by Type A at 400 rpm and Type C at 300 rpm. By performing parametric analysis via governing equations, the calculated non-interference speed is approximately twice that of the turbine’s maximum speed. Furthermore, as the turbine reaches its maximum rotational speed at the optimal length diameter, the turbine speed decreases without interference from the jet nozzle rotor. This resembles a phenomenon of non-interference rotor jet on Z-Blade turbine.

Review on numerical techniques applied in impulse hydro turbines

Abstract Impulse turbines are widely used in hydropower plants around the world due to their high efficiency in a larger operating range compared to reaction turbines. State of the art Pelton turbines can give over 90% efficiency at the designed operation load. However, there lies a possibility of improving the efficiency at off design condition for these turbines by optimizing the design of the nozzles, runner and/or housing. Prediction of the performance of the turbines by numerical techniques allows a quicker design optimization and at a much lower cost. In the case of impulse turbines, the use of CFD is limited by the complex nature of the flow, interaction of the jets, water/air mixture and interference of water after the impact on the successive buckets. Unlike reaction turbines, where the performances of the turbines could be studied through time-independent analysis to some extent, transient simulations are inevitable for the impulse turbines. Moreover, need for the multiphase models add to the overall complexities of CFD. Some recent development includes the use of Lagrangian scheme, which has reduced the computational efforts significantly. In the conventional Eulerian schemes, it is found that the numerical domains are usually simplified, either by using symmetry (half bucket) or rotational periodicity options. With the development of the computational capacity, some recent studies have also performed full turbine’s simulation, using nearly 50 million mesh elements. The design optimizations are performed on the shapes of the bucket, jet, deflectors as well as the turbine’s casings. However, validation of the numerical solutions remains a challenging topic with the quality of the mesh being used currently. Nevertheless, progresses in the numerical techniques and computing power within the last 15 years have strengthened the prospects of utilizing CFD and FEM as primary tools for validating and optimizing the design of the impulse turbines.

Comparison between fuzzy, neuro-fuzzy and neural network models to estimate the expansion of coffee berry borer in colombian coffee crops PDF XML Nychol Bazurto, Carlos Martinez, Helbert Eduardo Espitia 19-24 Comparative Analysis between a Discrete Spiral Chamber and a Continuous Spiral Chamber via ANSYS

Hydraulic turbines have been elements of utmost importance to meet the energy needs of communities worldwide. These are used with elements that improve the flow behavior of water to the turbine so that its energy benefits are improved. Spiral chambers are circular elements where their cross-section is constantly changing and are used in reaction turbines, such as Francis turbines. Their main function is to distribute evenly the fluid into the impeller inlet. This paper sought to use engineering simulation tools (ANSYS - CFX) to compare behavior and performance from a discreet continuous spiral chamber in a virtual environment under the same physical operating conditions, providing a comparative view of the performance present between the two manufacturing methods of spiral chambers

Design of a Pelton Turbine for a Specific Site in Malawi

Malawi's poor electrification rate can be improved through the maximum utilization of available renewable energy resources. Malawi has several rivers which can be utilized for electricity generation. However, most rivers such as Lichenya are not utilized to its full capacity. This paper presents the theoretical designing of a pelton turbine for Lichenya River in Malawi for maximum generation of electricity. Hydropower plants can either be impoundment, diversion or pumped storage type. The turbine used for any type of plant depends on the available head and river flow rate. The hydraulic turbines are classified into impulse turbines and reaction turbines. Pelton turbine is under impulse turbines and are usually associated with very high head and low discharges with low specific speeds. Additionally, Pelton turbine is simple to manufacture, are relatively cheap, and have good efficiency and reliability. The river flow data for Lichenya River were collected from the Ministry of Irrigation and Water Development in Malawi. The design flow of 3.2 m3/s for the river was determined form the data. The river is within the catchment area of 62.3 km2 and gross head of 304 m. The calculation of dimensions were carried out with the aid of EES software and spreadsheet. The designed turbine can generate 8067 kW of power with a turbine hydraulic efficiency of 95.4%. The detailed dimensions of the bucket, runner, penstock, and nozzle are presented. Therefore, this study can be the best guideline for further energy developments on Lichenya River in Malawi.

Stochastic modelling of cavitation erosion in Francis runner

Reaction turbines, of which Francis turbines, constitute a large proportion of low and medium head turbines installed in hydropower plants. Managing these machines represents a real challenge in terms of efficiency, competitiveness and demands on the energy market. Turbines runner blades exhibit loss of performance from damage due to several reasons. One common source of damage is erosion due to the cavitation phenomenon. Indeed, at a given operating region, rapid changes of velocity can create bubbles in the water flow due to local low pressures. When cavitation bubbles reach pressure recovery, they collapse and may induce wear or erosion in these regions. Even if this phenomenon has been intensively studied in the past decades, cavitation erosion is not fully understood as it is driven by several parameters such as flow dynamic, turbine design, environment, or material properties. Some of these parameters can be studied in laboratory to compare materials resistance between each other. This article aims to model the cavitation by a stochastic model using erosion experimental data observed in the laboratory. The benefit of such models is to consider both the uncertainties and natural fluctuations of the phenomenon. With the proposed framework, the study will highlight the differences observed in cavitation erosion experiments of two common materials used to manufacture Francis’s runners. This study is the first step in a project aiming at the prediction of turbines mass loss due to cavitation erosion on actual operating Francis turbines.

Numerical prediction of hydraulic performance in model and homologous prototype Pelton turbine

Pelton turbine is widely used in in utilizing the high water head resource. The multiphase flow in the Pelton turbine is too complex to be analysed detailed as the flow in the reaction turbines. So the hydraulic design of Pelton turbine was mainly based on the know-how. The homologous turbine model was the only way to verify its performance in the past. Although an efficiency scale-up equation for Pelton turbines had established in the IEC 60193 code, researches had shown different internal flow phenomena would influence the efficiency scale effects and lead to different efficiency scale for different turbine design. This paper simulates the internal flow of model and homologous prototype Pelton turbine at three relative needle strokes. Homogenous model and SST k-ω model will be adopted to simulate the unsteady two-phase flow in the rotating buckets. Unsteady simulation results would help to numerical investigate the scale effect of Pelton turbine.

Numerical analysis of a Pelton runner water sheet flow under super-high head

The hydraulic performance of Pelton turbine is different from reaction turbines due to its unsteady flow of rotating buckets with time and space. The water sheet flow in Pelton turbine is also very complex as the jet flow is often interacted with air and itself. This paper numerically investigates the dynamic hydraulic performance of a Pelton under super-high head. Unsteady numerical simulations were performed using SST k-ω. Two-phase homogeneous model and VOF were adopted to model he free surface flow. The evolution history of water sheet flow in the buckets were presented. The distribution of pressure coefficient on the bucket surface were also analysed. The results indicate that the development of water sheet flow on the bucket surface can be divided into three stages, corresponding to the output power variation process. This calculation can be used to illustrate the hydraulic mechanism of water sheet flow evolution.

Optimal design of air turbines for oscillating water column wave energy systems: A review

Oscillating water column wave energy harvesting system uses pneumatic power to run a turbine and generate power. Both reaction (mainly Wells turbine) and impulse type turbines are tested in oscillating water column system and the performances are investigated. Reaction turbines are easy to install, and the operating range is narrow and possesses higher peak efficiency. On the contrary, impulse turbines have the wider operating range and lower peak efficiency. Some of the key parameters for Wells turbine are solidity, tip clearance, and the hub-to-tip ratio. Significant performance improvement is possible by redesigning the turbines using optimization techniques. Till date, surrogate modeling and an automated optimization library OPAL are commonly used in optimization of oscillating water column air turbines. In this article, various types of oscillating water column turbines are reviewed, and optimization techniques applied to such turbines are discussed. The Wells turbine with guide vane has the maximum efficiency, whereas the axial-impulse turbine with pitch-controlled guide vane has the widest operating range. Turbines with optimized geometry have better overall performance than other turbines.