Papers by oblique shrestha
Materials Engineering eJournal, 2021
Several research studies have been conducted on the development of erosion-resistant alloys, coat... more Several research studies have been conducted on the development of erosion-resistant alloys, coatings, and optimized hydraulic design of components to overcome sediment erosion-induced problems in hydro turbines. This research work has attempted to investigate the erosion wear on CFT blades made up of different materials and coatings, using a modified version of Rotating Disc Apparatus (RDA). The main consideration in designing the RDA is to accelerate the rotating speed and the relative velocity to achieve rapid erosion results. The materials of blades used for the experiment were SUS304, SUS440C, SUS630, SCM440, and STD11. These test specimens were exposed to a high sediment concentration of 127000 ppm. From the calculated amount of erosion and erosion rate data that the rate of erosion exhibits a strong relationship to characteristics of the material, such as mechanical and chemical properties. The estimation further suggests that the coated specimens follow a similar trend as of...
Sediment erosion is the main challenge in the Nepalese hydro power Project. Water carries sand co... more Sediment erosion is the main challenge in the Nepalese hydro power Project. Water carries sand containing highly abrasive particle that is produced due to continuous uplift of the mountain ranges, cracks in rock and heavy rainfall. The water with erodent erodes the several components of the hydraulic turbine during operation time which decreases the life and efficiency of the plant. Sedimentation affect from high head Pelton and Francis turbine to low head Cross flow turbine (CFT) regardless to capacity of the plant. Several research works had been performed to identify the parameters that control the erosion rate and to develop mathematical model to estimate the effect on different components of hydraulic turbine. New design was introduced to reduce the effect of erosion on high head Francis turbine. Although there are plenty number research had been done and going on as well in Nepal, no traces is found which addresses the sediment effect in locally made Cross flow turbine. Theref...
The main objective of this study is to determine the effect of air layers on the performance of t... more The main objective of this study is to determine the effect of air layers on the performance of the crossflow turbine and the internal flow pattern in the turbine chamber. Two phase flow (air & water at 25o C), steady state with SST turbulence model was selected in the commercial CFD code ANSYS CFX 13.0 for the numerical simulation. The design parameters included 10 m head, 0.1 m/s flow rate and 642 rpm rotational speed. Different cases of airvents were selected varying the location and ratio between air and water during the numerical process. Insertion of air layer in the turbine passage shows some slight performance improvement in terms of output power and hence efficiency. Air layer introduction is known for its effectiveness on the suppression of recirculation zone and shock loss at the runner axis. Choice of location of air insertion vents and the ratio between air from suction pipe and water from the runner inlet also plays substantial role for the turbine performance.
Renewable Energy, 2017
In guide vane cascade of Francis turbine, highest acceleration occurs, which generates equivalent... more In guide vane cascade of Francis turbine, highest acceleration occurs, which generates equivalent amount of force for work done and erosion due to instantaneous change in flow dynamics. Hence in addition to runner vane, suitable selection of guide vane profile has equal importance. Usually, NACA defined hydrofoils are used for guide vanes. Numerous options are available, but selection of best one for optimum energy harness is important. Primarily, guide vane torque and turbine efficiency is prioritized. For the turbines operating in sediment laden water, pressure difference between two sides of guide vane and erosion resistivity are additional factors to be considered. This work was performed in the vicinity of guide vane profile selection for Francis turbines operating in sediment laden water. Computational analysis on turbine flow passage and experimental study with Rotating Disc Apparatus were performed in order to identify suitable profile. Unsymmetrical profiles were found to be better handling erosion maintaining consistency in turbine performance.
International Journal of Scientific Research in Science and Technology, 2021
The removal of surface material due to repeated impacts of sediment is known as sediment erosion.... more The removal of surface material due to repeated impacts of sediment is known as sediment erosion. This prominent phenomenon is found to exist on a run of the river types of hydro projects where the hydro turbines are exposed to sediment particles. It has drawn the attention of researchers, academic institutions, and hydropower developers to conduct research on this issue. Investigation of the problem at the site may require sophisticated equipment and sensors- set up for quantitative measurements. This process is time consuming and difficult as it is difficult to access the erosion location. Laboratory setup can be a solution to study and investigate erosion behaviour in well-controlled laboratory conditions. Among several erosion testing apparatuses, Rotating Disc Apparatus (RDA) has been used for the investigation of erosion as well as cavitation of hydro components, and to study the erosion resistivity of different materials. This device mainly consists of a rotating disc and an ...
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Papers by oblique shrestha