St Martins Engineering College

Secunderabad, India

St Martins Engineering College

Secunderabad, India

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Koppula S.B.,St Martins Engineering College
International Journal of Applied Engineering Research | Year: 2016

Literature review revealed that, advanced additive technologies used in today’s high-performance gear oils are capable of inducing the required reactions on the surfaces of gears and bearings, thus providing reliable damage protection even under severe operating conditions. In practice, industrial gears are often operated under lower oil temperatures than would normally be generated in a fully-loaded gearbox. Lower temperatures prevail, for instance, while a gearbox is being taken back into use after prolonged standstill, i. e. during the time it takes for the oil to heat up from ambient temperature to service temperature. Similarly, when a gearbox is being operated below its full load capacity, with reduced speed, or with frequent stop-and-go, the operating temperature of the oil will be lower than it would be under full load. Such applications require gear oils that reliably protect gears and rolling bearings against damage, not only at full load operating temperatures, but also at lower ones. The protection of gears in the gear box against high induced temperature requires careful consideration. Recent research as reported in literature review indicated that, addition of nano particles or particles of nano size (less than 100 micron size) have a great influence on the thermal properties like heat transfer rate, viscosity, friction factor of the lubricant etc and helps in improving the life of the lubricating oil and consequently life of the gear box. An attempt is made in this paper to review the current research on lubricating properties of lubricants and effect of adding nano additives on the performance of lubricants. Present study includes a review of literature on the heat transfer rate, viscosity, friction properties of lubricants etc with and without additives. The major contribution of present work is to review the current state of research in lubricating properties of lubricants used in gear boxes with special referenced to addition of nano particles in the lubricant and to make preliminary investigations on the effect of additives on thermal properties of lubricants used in gear boxes. © Research India Publications.

Vasantha Gowri N.,Chaitanya Bharathi Institute of Technology | Ramlinga Raju M.,Jawaharlal Nehru Technological University Kakinada | Singh B.P.,St Martins Engineering College
2014 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2014 | Year: 2014

The paper deals with the random movement of metallic particle in a high voltage transformer. A particle is assumed to be in the annular gap between HV winding and the press board cylinder nearest to HV winding, which is initially resting at the bottom portion of winding. Circulating oil induces movement in the gap and the particle starts moving in random direction depending on its shape and size. In order to generate a path of particle, Monte - Carlo simulation is performed by defining its velocity and random angle at every step of movement. The final results show the probability of striking the winding for a given velocity and angle. The transformer is assumed to be un-energized for computation. The probability of strike shows a definite trend with random angle assumed and velocity of movement generally encountered in Air Natural Forced Oil Cooling (ANFC) System. The results obtained may be helpful in determining the occurrence of partial discharge for an energized transformer. © 2014 IEEE.

Gowri N.V.,CBIT | Raju M.R.,Jawaharlal Nehru Technological University Kakinada | Singh B.P.,St Martins Engineering College
2015 North American Power Symposium, NAPS 2015 | Year: 2015

There are several reasons of failure of power transformers in a system. One of the reasons of failure is attributed to the presence and movement of metal particles in oil. These induce partial discharge due to high electrical stresses, in the transformer. In order to theoretically determine the probability of occurrence of partial discharges in a high voltage 220/132 kV autotransformer only HV winding area is modeled. A metal particle of a given size and L/R ratio is introduced at the bottom of HV winding between inner surface of winding and pressboard barrier. Under the influence of oil flow the particle moves randomly within a predefined set of solid angles. During its upward movement the trajectory of the particle is calculated. The particles during their upward movement have demonstrated three different attributes, viz. (a) the particle escapes without striking a high voltage disc. (b) It strikes a disc, however the electric stress induced by the particle at the disc does not exceed threshold voltage for PD to occur and (c) The disc struck by particle provides adequate stress for PD to occur. The present paper deals with the occurrence of PD using probabilistic method for different sizes of wire like particle. © 2015 IEEE.

Sridhar P.,Institute of Aeronautical Engineering | Singh B.P.,St Martins Engineering College
Turkish Journal of Electrical Engineering and Computer Sciences | Year: 2012

Insulation failure within the windings of a power transformer arises due to over voltages, under voltages, notches, glitches, etc. A widely used technique to detect these power transformer insulation failures during an impulse test is the comparison of neutral current waveforms. Any shift in the recorded waveforms between reduced and full voltage confirms the existence of a fault in the windings. Hence, a proper analysis of neutral current waveforms is necessary to assess the condition of the insulation of power transformer winding. In order to carry out a wave shape analysis, a 61 MVA, 11.5/230 kV generator transformer is used and faults are created in the disks of high-voltage windings at specific locations. Neutral currents are recorded by applying a 100 V, low-voltage impulse. Noise inherent in the neutral current during recordings is isolated using a biorthogonal wavelet and the denoised signals are analyzed using the Shannon wavelet for identification of a fault in the winding. © TÜBITAK.

Rajashekar M.,St Martins Engineering College | Venu Gopala Swamy I.V.,ACE Engineering College | Kumar T.A.,ACE Engineering College
Journal of Theoretical and Applied Information Technology | Year: 2011

The aim of this project is to model a six step discontinuous current mode inverter fed to a Permanent Magnet Synchronous Motor (PMSM) drive using MATLAB/SIMULINK. The dq-axis Voltage-Current and Torque relation in terms of machine parameters are used along with a six step 120 degree mode inverter and gate drive using MATLAB/SIMULINK. There is also a provision for easy changes to the machine parameters and gate drive inverter parameters at appropriate places. The various subsystems allow us to change the parameters like power supply data, phase angle advance, PMSM parameters such as stator resistance, inductance, number of poles, rotor magnet constant, Moment of Inertia of motor and damping constant etc. The above model finds its application in power electronics and drives laboratories. Simulation will be done for a phase angle advance of 30° and 45° for a six step discontinuous current mode inverter fed PMSM drive at no load. © 2005 - 2011 JATIT & LLS. All rights reserved.

Kumar P.,St Martins Engineering College | Kennady J.,Coimbatore Institute of Technology
Journal of Electroanalytical Chemistry | Year: 2016

A simple and viable electrodeposition technique has been implemented to fabricate nanocrystalline Ni-W electrodeposits from an alkaline citrate bath with variations of vanillin (additive) concentration. The optimization of additive in the bath was substantiated in terms of its corrosion resistance property (evaluated using Tafel polarization and electrochemical impedance spectroscopy). For alloys deposited in presence of additive (100 ppm) in the bath, resulted in low corrosion rate (C.R) and high charge transfer resistance (Rct). The enhanced corrosion resistance property (i.e. low C.R and high Rct) was deduced in terms of its homogenous surface morphology (using scanning electron microscope), reduction in crystalline size (using X-ray diffraction study), diminish in surface roughness value (using atomic force microscopy) as compared with that of electrodeposits obtained in the absence of additive. The inclusion of additive in the electrodeposits during electrodeposition, showed a major impact for its significant corrosion resistance property (C.R. − 0.12 mm/year and Rct-2177.83 Ω·cm2). With an increase in the additive concentration in the bath, the corrosion resistance of the Ni-W coating becomes inferior, due to its porous nature and relative decrease in its capacitive behavior at electrode/electrolyte (corrosive) interface. © 2016 Elsevier B.V.

Asokan R.,Indian Institute of Horticultural Research | Sharath Chandra G.,Indian Institute of Horticultural Research | Manamohan M.,Indian Institute of Horticultural Research | Krishna Kumar N.K.,National Bureau of Agriculturally Important Insects | Sita T.,St Martins Engineering College
Journal of Pest Science | Year: 2014

The cotton bollworm, Helicoverpa armigera is a highly polyphagous pest infesting a number of economically important crops, annually causing enormous crop losses. Management of this pest is challenging over the years due to various factors including development of resistance to wide spectrum of chemical insecticides. RNA interference (RNAi) has tremendous potential to combat insect pests. However, RNAi mediated silencing efficiency varies from gene to gene, hence successful RNAi mediated pest control requires selection of suitable target gene(s), which are effectively silenced by the exogenous delivery of cognate double-stranded RNA (dsRNA) through midgut. Therefore, we have evaluated the effect of two concentrations of dsRNA delivered through semi-synthetic diet in silencing five important genes, viz. glutathione-S-transferase, cytochrome P450 (both involved in detoxification of host allelochemicals); trypsin, chymotrypsin (both involved in digestion of proteins) and juvenile hormone acid methyl transferase (jhamt) (involved in larval metamorphosis). Extent of silencing was assessed by quantitative real-time PCR (qRT-PCR). Results revealed that above target genes were silenced variably, 20 μg dsRNA treatment having a more pronounced effect than 10 μg in reducing the transcript levels, larval, pupal weight, and pupation. Silencing of chymotrypsin had a more pronounced effect on larval and pupal weight compared to other target genes, while jhamt severely affected pupation. This study demonstrated that target genes have varied sensitivity to RNAi, chymotrypsin, and jhamt were shown to be suitable candidate genes that could be utilized for RNAi mediated management of H. armigera. © 2013 Springer-Verlag Berlin Heidelberg.

Sridhar P.,Institute of Aeronautical Engineering | Rao V.P.C.,Lords Institute of Engineering and Technology | Singh B.P.,St Martins Engineering College
2015 Conference on Power, Control, Communication and Computational Technologies for Sustainable Growth, PCCCTSG 2015 | Year: 2015

As the growth in comfort of the customers, demand is increasing in day to day electrical operations. At the same way problems related to the power system network due to short circuits also increasing. To overcome the short circuit problems, many devices like DVR and accurate control techniques established, among them the efficient device is Fault Current Limiter (FCL). The FCL reduces the short circuit faults and the electromagnetic stress over the associated devices as well as reduce implementation of bulky circuit breakers and also power distribution interruption. This concept proposes the utilization of the proposed FCL with analysis of power system network behavior and continuous power without interruption at PCC can have gallant power quality concerns. This paper shows the operation of a switch voltage controlled three phased FCL is planned for favorable merits with different types of fault as LG, LLG and LLLG by using Matlab/Simulink tool and results are conferred and simplified hardware prototype model is acquainted based on test system. © 2015 IEEE.

Srikanth D.V.,St Martins Engineering College | Sreenivasa Rao M.S.,JNTUH College of Engineering
Materials Today: Proceedings | Year: 2015

Abrasive jet machining also known as micro-abrasive blasting or pencil blasting is a non-traditional machining process in which the metal removal takes place due to high velocity abrasive particles. The abrasive particles are propelled by high velocity carrier gas (commonly air). This process is specially used for edge shapes and intricate shapes. The metal cutting or drilling is performed due to high impact of abrasive particles on the work surface. This machining technology proves good results when tool life is taken into consideration, given the fact that the abrasive material can be reused several times before abrasive particles lose their cutting effect. It is already proved that this technique is effectively adopted for polishing and deburring processes. The present study highlights the influence of different parameters of Abrasive jet machining like Pressure, SOD, Abrasive Flow Rate, on the Metal removal and Kerf width on Ceramic Tiles, the type of abrasive particle used for this experiments is Al2O3. The experiments are conducted according to TAGUCHI method of L9 orthogonal array and RSM, latter compared with the Results of ANOVA using STATGRAPHICS. © 2015 Elsevier Ltd.

Kishan N.,Osmania University | Jagadha S.,St Martins Engineering College
Thermophysics and Aeromechanics | Year: 2016

The paper presents an investigation of the influence of thermophoresis on MHD mixed convective heat and mass transfer of a viscous, incompressible and electrically conducting fluid along a vertical flat plate with radiation effects. The plate is permeable and embedded in a porous medium. To describe the deviation from the Darcy model the Forchheimer flow model is used. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing partial differential equations are transformed into a system of ordinary differential equations using similarity transformation. The nonlinear ordinary differential equations are linearized by using quasilinearization technique and then solved numerically by using implicit finite difference scheme. The numerical results are analyzed for the effects of various physical parameters such as magnetic parameter Ha, mixed convection parameter Rad /Ped, Reynolds number Red, radiation parameter R, thermophoretic parameter τ, Prandtl number Pr, and Schmidt number Sc. The heat transfer coefficient is also tabulated for different values of physical parameters. © 2016, Pleiades Publishing, Ltd.

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