Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
7 results
Search Results
Item Dynamic voltage restorer (DVR) –areview(River Publishers editor@jgenng.com, 2018) Remya, V.K.; Parthiban, P.; Ansal, V.; Babu, B.Power quality (PQ) is gaining a great deal of importance as more sensitive loads are introduced into the utility grid. The degradation of product quality, damage of equipment and temporary shutdowns are the general issues associated with PQ problems in industries. Any mal-operation or damage of the industrial sensitive loads results in monetary losses disproportionately higher than the severity of the PQ issues. The evolution of power electronics technology replaced the traditional power quality mitigation methods with the introduction of Custom Power System devices (CUPS). The major power electronic controller based CUPS are DSTATCOM, DVR and UPQC. DVR is a pertinent solution for the economic losses caused by the PQ issues in the industries. Among the CUPS, DVR is the most cost-effective one. In the published literature, only a few papers correspond to the review of DVR technology. In this paper, a systematic review of published literature is conducted and a description is given on the design, standards and challenges in the DVR technology. A detailed survey is conducted on the published literature to address the various aspects and issues in the DVR system. This paper arrangement gives the working principle, structure, various topologies, compensation techniques, voltage sag detection methods and control methods of the DVR under different sections. The section “Challenges faced by the DVR” included in the manuscript can be useful for the researchers beginning their work in the domain of DVR. The simulation results using the sim power system tool of MATLAB/Simulink software are provided for analysis and comparison. © 2018 the Author(s). All rights reserved.Item Synthesis of Furans–Recent Advances(Bellwether Publishing, Ltd., 2019) Deepthi, A.; Babu, B.; Balachandran, A.L.[No abstract available]Item Synthesis of silver nanoparticles using medicinal Zizyphus xylopyrus bark extract(Springer Nature, 2015) Babu, B.; Devadiga, A.; Shetty K, V.K.; Saidutta, M.B.In the present paper, biosynthesis of silver nanoparticles using Zizyphus xylopyrus bark extract is reported. Z. xylopyrus bark extract is efficiently used for the biosynthesis of silver nanoparticles. UV–Visible spectroscopy showed surface plasmon resonance peaks in the range 413–420 nm confirming the formation of silver nanoparticles. Different factors affecting the synthesis of silver nanoparticles like methodology for the preparation of extract, concentration of silver nitrate solution used for biosynthesis and initial pH of the reaction mixture were studied. The extract prepared with 10 mM AgNO3 solution by reflux extraction method at optimum initial pH of 11, resulted in higher conversion of silver ions to silver nanoparticles as compared with those prepared by open heating or ultrasonication. SEM analysis showed that the biosynthesized nanoparticles are spherical in nature and ranged from 60 to 70 nm in size. EDX suggested that the silver nanoparticles must be capped by the organic components present in the plant extract. This simple process for the biosynthesis of silver nanoparticles using aqueous extract of Z. xylopyrus is a green technology without the usage of hazardous and toxic solvents and chemicals and hence is environment friendly. The process has several advantages with reference to cost, compatibility for its application in medical and drug delivery, as well as for large-scale commercial production. © 2014, The Author(s).Item Implementation of Single-Phase Two-Switch Midpoint Unidirectional Multilevel Converter System(Walter de Gruyter GmbH, 2018) Roy, P.R.; Parthiban, P.; Babu, B.This paper deals with implementation of a single-phase three level converter system under low voltage condition. The frequency of the switches is made constant and involves change in $-t-on}}$ton and $-t-off}}$toff duration. For this condition the pulse width modulation control scheme for a single phase three level rectifier is developed to improve the power quality. The hysteresis current control technique is adopted to bring forth three-level PWM on the dc side of the bridge rectifier and to achieve high power factor and low harmonic distortion. Based on the proposed control scheme, the line current is driven to follow the sinusoidal current command which is in phase with the supply voltage. By using three-level voltage pattern the blocking voltage of each power device is clamped to half of the dc link voltage. The simulation and experimental results of 20W converter under low input voltage condition are shown to verify the circuit performance. Open loop simulation and hardware tests are implemented by applying a low voltage of 15 V(rms) on the input side. © 2018 Walter de Gruyter GmbH, Berlin/Boston 2018.Item Computational investigation on secondary flows in a linear turbine cascade with tapered dual fence(Korean Society of Mechanical Engineers, 2019) Kiran, K.N.; Babu, B.; Anish, S.The focus of the present work is to minimize the secondary flow losses inside a linear turbine cascade by means of a novel design of streamwise dual fence. The leading edge and trailing edge of the fences have been modified so as to reduce the total pressure loss coefficient in the passage. The study has been carried out computationally based on RANS simulations with SST turbulence model. Numerous simulations have been undertaken with single fence and dual fence models and compared with the base case model. The dual fence model with tapered trailing edge exhibits significant loss reduction compared to the base case. A suitable fence height ratio (FHR) has been identified for the dual fence model. The FHR = 2 configuration reduces the secondary flow kinetic energy by 78 % within the blade passage and it reduces the exit angle deviation significantly throughout the span. Detailed flow field analysis has been carried out to understand the physical mechanism behind the loss reduction with dual fence models. It is observed that fence-1 breaks the pressure side leg of the horse shoe vortex at the beginning of their formation itself. The radial penetration of the suction side leg of the horse shoe vortex is restrained by fence-2. These combined effects prevent the formation and mixing of two prominent loss core regions thereby avoiding the accumulation of low energy fluid near the suction side of blade. © 2019, KSME & Springer.Item Metal free synthesis of 1-azaspiro[4.4]nonane-3-one system via reactions of nitrones with 1,1-disubstituted allenes(HeteroCorporation support@jhetchem.com, 2019) Amrutha, U.; Babu, B.; Prathapan, S.In the cycloaddition reaction between fluorenone N-aryl nitrones and 1,1-disubstituted allenes, the initially formed cycloadduct underwent facile [1,3] shift to give 1?-phenylspiro[fluorene-9,2?-pyrrolidin]-4?-ones. Although 1?-phenylspiro[fluorene-9,2?-pyrrolidin]-4?-ones are stable in solid state, a few of them underwent facile aerial oxidation in solution to give the corresponding 1?-phenylspiro[fluorene-9,2?-pyrrolidine]-4?,5?-diones in excellent overall yields. © 2019 Wiley Periodicals, Inc.Item Transient analysis of upstream wake inside turbine blade passage with purge flow(Elsevier Masson SAS 62 rue Camille Desmoulins Issy les Moulineaux Cedex 92442, 2020) Babu, B.; Anish, S.Secondary air bled from the compressor which bypasses the combustion chamber is used to seal the turbine components from incoming hot gas. Interaction of this secondary air (also known as purge flow) with the mainstream flow can alter the flow characteristics of turbine blade passage. This paper presents numerical investigation of interaction between ejected purge flow and mainstream flow in the presence of upstream disturbances/wakes. Steady as well as unsteady simulations are carried out using Reynolds Averaged Navier Stokes equations and SST turbulence model. The numerical results are validated with experimental measurements obtained at the blade exit region using an L shaped 5 hole probe and Scanivalve. Upstream wakes are generated by a circular cylinder, kept upstream of blade leading edge at different pitch-wise positions. For transient analysis cylinders are kept at stagnation line (STW) and middle of the blade passage (MW). The analysis reveals the interaction effects of two more additional vortices, viz. the cylinder vortex (Vc) and the purge vortex (Vp). Steady state analysis shows an increase in the underturning at blade exit due to the squeezing of the pressure side leg (PSL) of horse shoe vortex towards the pressure surface by the cylinder vortices (Vp). The unsteady analysis reveals the formation of filament shaped wake structures which breaks into smaller vortical structures at the blade leading edge for STW configuration. These filaments lead to the formation of additional pressure surface vortices. On the contrary, in MW configuration, the obstruction created by the purge flow causes the upper portion of cylinder vortices bend forward, creating a shearing action along the spanwise direction. In MW configuration, the horse shoe vortices generated from the upstream cylinder are broken by the purge vortex whereas in the STW configuration it slides over the purge vortex and move towards the suction surface under the influence of the pitchwise pressure gradient. © 2019 Elsevier Masson SAS