Water Conductor System Research Articles

Computational fluid dynamics based transient investigation of the penstock in a hydropower plant

Abstract Water hammer is a hydraulic transient phenomenon that occurs at hydropower plants (HPP) when the discharge is rapidly decreased or closed, which can damage the HPP components, mainly penstock. Sudden Pressure rise and collapse of water columns or cavity forms due to the low pressure may cause severe damage. Understanding transient flow behavior is necessary to prevent harmful pressure fluctuations and ensure power plant safety. The present 3D computational fluid dynamics (CFD) study is carried out to predict pressure fluctuations, the occurrence of any cavitation, and water column separation at critical locations in the water conductor system from the surge tank to the turbine inlet due to low pressure caused by the closing of the hydraulic turbine guide vane valve at downstream of the penstock. The hydraulic domain of the penstock, connecting the head race tunnel to the turbine inlet, is created as per the HPP UHL-III actual water conductor system elevations, bent bifurcations, and geometric sizes. Transient CFD simulations for different load rejection conditions were performed in the Ansys CFX by modifying the Unsteady Reynolds Average Navier’s Stoke equation (URANS), incorporating the elastic effect of penstock material, and considering the variable density of the water, taking the compressibility. Transient pressure in the penstock was recorded at various locations. Further, minimum pressure inside the flow domain that falls in the no-column separation zone was also obtained.

Model studies for desilting basin for Teesta-VI H.E. project, Sikkim – a case study

Desilting basins play an important role in run-of-river hydro power projects on Himalayan Rivers. These rivers carry huge amount of sediment with them, due to steep slopes and fragile geology of the region. The suspended sediment enters through the power intake and ultimately the power house. This causes heavy damage to the turbines and other under water parts. Therefore, desilting basins are provided to eliminate suspended sediment from the water conductor system. The design of desilting basin is verified on a physical model for 90% removal of suspended sediment coarser than 0.2 or 0.3 mm and efficacy of flushing tunnel below in transporting the settled sediment. Central Water and Power Research Station, Pune has conducted physical model studies for desilting basin for various hydro power projects in India and neighbouring countries. One such study, Hydraulic model studies for desilting basin for 500 MW Teesta-VI Hydro Electric Project, Sikkim is presented in this paper. Various design parameters such as length of desilting basin, length and bed slope of inlet transition, outlet transition, size of silt flushing tunnel, size and spacing of openings connecting main basin with silt flushing tunnel etc. were tested during the model studies. The results in terms of settling efficiency for 0.3 mm size particles were obtained.

Integration of small hydro turbines into existing water conduit of an irrigation dependent power plant – A case study

Hydro energy is one of the richest and most useful renewable energy sources in the world. In an irrigation-based storage reservoir, agricultural to hydro power water transfer is important. A tradeoff between irrigation and power generation is essential in order to achieve optimal social benefits. Most of the irrigation based hydro turbines employ the reaction type turbines due to the advantages of low/medium head and high discharge through the irrigation canals. The release of water through irrigation gates is affected during the lower release of water for irrigation, flora and fauna and drinking. The power units are of reaction type hydro turbines could not able to tap the energy during the lower release due to the restriction on operational limitations, the turbine may subject to cavitation and leads to noise and vibration causes subsequent fatal failure of parts and catastrophic accident on the plant. This condition leads to reasonable generation loss to the power generating units. A pilot study on Dhom (2x1 MW) irrigation dependent hydroelectric plant, Mahagenco, Satara, Maharastra has been conducted in order to tap the water during the lower release and flood scenario from the reservoirs. The modification has been suggested in the existing layout of penstock section at main inlet valve. This paper emphasizes on utilizing untapped energy by integrating small hydro turbine into the existing water conduit in an irrigation dependent hydro power plant. Incorporation of inline hydro power units with existing water conductor system would yield additional power generation of 2.592 Million units of energy per year. Further, the plant capacity factor could be increased from 0.315 to 0.463. The additional power generation can be used for internal loads of the power house.

Experimental and numerical investigations of water hammer analysis in pipeline with two different materials and their combined configuration

Water conductor system in hydro power plants experience water hammer or hydraulic transient events regularly and may cause damage of civil and mechanical components. Recently developed viscoelastic pipes such as Glass Reinforced Fibre Plastic (GRP) have been started in use to replace metallic pipes in hydro power and water supply plants. However, studies on combinations of metallic-viscoelastic pipeline behaviour for water hammer conditions are limited especially for varied diameter and combinations of different pipe materials. In this paper, the response of water hammer pressure in metallic-viscoelastic pipeline is investigated experimentally and numerically. Two different pipe materials i.e. Mild Steel (MS) and GRP and their metallic-viscoelastic pipe configuration was used to investigate and analyze the water hammer pressure generation and compared with pressure developed in single material pipeline. An experimental setup was designed and fabricated to carry out the water hammer test. The numerical simulation was carried out by using the method of characteristics (MOC). The GRP pipeline was found more effective to reduce the water hammer pressure and a combination of GRP + MS pipeline (GRP for initial reach having low pressure and MS for later reach having high pressure) in the plants, where GRP pipeline alone cannot be used due to manufacturing limitations of pressure and size, can be used to reduce transient pressure in the water conductor system.

Desilting Basin Efficiency Estimation for Run-of-River Small Hydropower Plants

Suspended sediment concentration and discharge are important factors affecting the operational reliability of run-of-river small hydro power (SHP) plants. Elimination of sediment transported with the flow across the turbines of run-of-river plants is therefore a critical issue for the sustainability of the SHP industry. Comprise of a small diversion weir throughout a stream, the SHP plants does not have space to pile sediments but should be able to divert the incoming bed loads to the river downstream. Sediments in the water entering through the turbines with extreme velocity erode the contact surfaces of turbine mechanisms which results in reduced hydraulic efficiency and increased maintenance cost. Subsequently, desilting basins have become an essential part of the water conductor system of run-of-river SHP to reduce the impact of damage due to suspended sediment. Desilting basins are devised as settling basins to settle sediments larger than a targeted size. They are constructed just after power intake and discharge is despatched through them before pass into the head race tunnel. This study is aimed to estimate the sediment removal efficiency of SHP desilting basins based on data recorded at the intake of a run-of-river SHP. Considering the hydrological variability, probabilistic approach was used to obtain mathematical function for the probability density of suspended sediment concentration (SSC) based on the recorded data.

Management of Hydropower Tunnels to Prevent Collapse and Remedial Measures

Tunnels are important structures in hydropower projects as they reduce the length of the water conductor system. However, tunnels also pose the possibility of collapse during construction which may cause significant time and cost overruns. Moreover, collapsing tunnels pose threats to workers and machinery. Systematic control and understanding of tunnel physics is key to preventing these dangers. In this paper, we explore the most effective means for constructing tunnels for hydropower projects.HYDRO Nepal JournalJournal of Water, Energy and EnvironmentIssue: 19Page: 31-37

Commentary on the Efficiency of Selected Structural Designs of Low Head Micro Hydraulic Power Plants

This article compares, first of all, structural designs of low head micro hydraulic power plants using Kaplan turbines. The authors have chosen this turbine class because siphon turbine systems suck the water up over the dams, can operate at temperatures below 0°C and are associated with less capital costs than turbine systems of other types. Besides it, mobile micro power plants can be easily assembled in a modular way and be installed on floating platforms thus providing appeal to a growing market niche. The authors discuss the issue of identity of possible structural designs of siphon micro hydraulic power plants in terms of their efficiency and selection of optimal pressure heads. They have developed a criterion of comparison of efficiency of various designs of siphon micro hydraulic power plants and provide evidence of virtual identity of selected structural designs with identical parameters in terms of efficiency. This criterion allowed them to make estimates in search for an optimal solution in terms of gross head (vertical distance between the highest and lowest water surface) versus net head (effective head available for power generation which is gross head less all the losses in the water conductor system including penstocks), which can be useful for designers of micro hydraulic power plants.

Sizing and Quantity Estimation for Desilting Tank of Small Hydropower Projects—An Analytical Approach

In small hydropower (SHP) projects, desilting tank is an important component, which protects the mechanical equipment specially turbine from the silt carried by the water conductor system. Desilting tanks are used in water treatment plants and hydropower channels to remove objectionable sediment of a specified size and quantity. Design of desilting tank requires evaluation of sediment removal efficiency over the range of sediment particle sizes. In the design of desilting tank, various combinations of width, depth, and length of the tank are possible to achieve desired silt removal efficiency. In the present study, an attempt has been made to develop correlations for sizing of desilting tank and estimation of quantities of various materials required in the construction of desilting tank. The results obtained were verified with the data collected on desilting tanks of recently developed SHP projects. The results are found within maximum error of ±12%. The correlation developed can be used for sizing and cost estimation of the desilting tank.

HYBRID MATHEMATICAL MODEL FOR SURGE ANALYSIS: A CASE STUDY

ABSTRACT Over the past few decades mathematical modeling technique is in vogue. A large number of water hammer cases have been analyzed using this technique, not only for simple systems but also for those with rather complex situations. The present analysis for a water conductor system having intermediate boundary condition such as pump behavior needed a hybrid mathematical model. The results of analyzing such system and comparing them with those obtained from the hydraulic scale model give more confidence in adoption of the mathematical technique.

TRANSITION FOR DESILTING BASIN WITH OPEN CHANNEL FLOW

ABSTRACT Desilting basin forms an integral part of the water conductor system of run-of-the- river schemes for hydro power generation while suspended sediment concentration is very high during monsoon. Transitions are provided to gradually reduce the velocity of flow entering into the basin. If transition is too long there is deposition of medium and coarse sediment on the bed of the transition itself. If transition is too short, there is uneven distribution of flow and higher turbulence. As such optimization of transition length, shape and bed slope is necessary to avoid deposition on the transition bed and more or less uniform distribution of flow entering into the desilting basin. As far open channel desilting basin is concerned inlet transition is very difficult to design due to substantial difference in depths on upstream and downstream of transition and also due to sub critical expansion. This objective could be achieved by providing a simple hump. The results of the hydraulic model studies conducted at CWPRS, Pune are discussed.

Total Quality Control Approch for Reduction in Percentage Repair for New Water Conductor System Khopoli

Total Quality Control Approch for Reduction in Percentage Repair for New Water Conductor System Khopoli

New Approach for Fabrication of Penstocks / Steel Liners for New Water Conductor System Khopoli by Modifying Joint Design

High tensile quenched and tempered steel, ASTM A517 GrF or Sumiten 780S, is used for fabrication of penstocks of hydroelectric power plants. In the workshops, submerged arc welding process is used for longitudinal as well as for circumferential joints. When plate thickness is 12-22 mm, usual practice to have single V/double V edge preparation with suitable ischolar_main face of about 2mm with SMAW ischolar_main backing. Such joint preparation takes longer for completing welding. Hence joint design was modified having single V from one side and having ischolar_main face of about 6 mm with zero gap between the plates without SMAW backing. Such modification of the weld design would improve productivity substantially with saving of weld metal. Paper describes successfully implementation of modification of joint design and saving achieved IN terms of man-hours and cost of the deposited weld metals.

Performance of Chhibro underground power house cavities after charging water conductor system - a case study : Mitra, S; Singh, B Proc International Symposium on Underground Engineering, New Delhi, 14–17 April 1988V1, P425–430. Publ Rotterdam: A A Balkema, 1988

Performance of Chhibro underground power house cavities after charging water conductor system - a case study : Mitra, S; Singh, B Proc International Symposium on Underground Engineering, New Delhi, 14–17 April 1988V1, P425–430. Publ Rotterdam: A A Balkema, 1988

Power for mysore

The Sharavathi Valley Project has been established to meet the ever-increasing power requirements of the State of Mysore in southwestern India. The project's dam, water conductor system, and surface station, as well as its transmission line, receiving station, and electric equipment, are described.