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Nath S.K.,Indian Central Power Research Institute
Materials Evaluation | Year: 2016

This paper discusses the development of an ultrasonic time of flight diffraction-based inspection technique for sizing surface-breaking vertical cracks in complex geometry plant components like a solid steam turbine rotor with integral discs. A simple geometric model was developed. Specimens containing vertical notches simulating cracks in real-life rotors and holding devices for affixing the transmitter and receiver probes in plane and on opposite sides of the disc-like portion of the specimens were designed and fabricated. Experiments were conducted, and the results show that the inspection technique developed here can size such cracks with reasonable accuracy. The technique can be useful for insitu condition assessment and remaining life assessment of aged, in-service complex geometry plant components.

The variation of amplitude and transit time of the diffracted signal from the crack-tip in complex geometry components and their resulting effect on the probability of detection (POD) and probability of sizing (POS) was studied. The diffracted signal amplitude has been evaluated from the standard expressions for diffraction coefficient, spatial attenuation and the transit time from the respective mathematical models for both vertical and inclined cracks. The same parameters namely the signal amplitude and the transit time have been measured through experiments conducted on simulated test specimens. It has been observed that the analytical and experimental results compare well with each other. Based on this result the trend and shape (width of the transition zone) of the POD/POS curves can be predicted. © 2013 Elsevier B.V. All rights reserved.

Mandi R.P.,Indian Central Power Research Institute | Yaragatti U.R.,Indian National Institute of Engineering
International Journal of Electrical Power and Energy Systems | Year: 2014

This paper describes the results of energy efficiency enhancement in 23 numbers of 210 MW coal fired power plants spread over India. Energy efficiency improvement of major auxiliary equipment with different plant load factors are summarized here with improved performance. The effect of plant load factor on all major auxiliary equipment and improvement in performance of auxiliary equipment are discussed in this paper. Operation of the plant at improved plant load factor reduced the specific auxiliary power from 11.23% at 70% PLF to 8.74% at 100% PLF that reduced the net auxiliary power by 9.1 MU/year that is an equivalent reduction of CO2 emission by 9500 t/year. Optimizing the excess air, controlling the furnace ingress, enhanced energy efficiency of individual equipment by proper maintenance, etc., improves the plant capacity and reduces the overall auxiliary power by about 1.5-2.1% of gross energy generation i.e., equivalent CO2 reduction of 23,000-32,400 t/year and release an additional power of about 3.5 MW (for a typical one 210 MW power plant) into grid. © 2014 Elsevier Ltd. All rights reserved.

Nithya V.D.,Bharathiar University | Selvan R.K.,Bharathiar University | Kalpan D.,Indian Central Power Research Institute | Vasylechko L.,Lviv Polytechnic | Sanjeeviraj C.,Alagappa Chettiar College of Engineering And Technology
Electrochimica Acta | Year: 2013

Nanosized Bi2WO6 particles were successfully synthesized by sonochemical method with an objective to develop an inexpensive and eco-friendly electrode material for supercapacitors. The prepared materialwas subjected to various thermal, structural, morphological, compositional, electrical and electrochem-ical studies. Bi2WO 6 nanoparticle with homogeneous distribution was achieved through sonochemicalprocess. The lattice parameter and atomic positions of Bi 2WO6 structure were refined through Reitveldanalysis. The electrochemical performance of Bi2WO6 nanoparticles was investigated in various aqueouselectrolytes such as 1 M NaOH, 1 M LiOH, 1 M Na2SO4, 1 M KOH and 6 M KOH solutions. Among these,the material exhibited an enhanced electrochemical performance in KOH electrolyte due to its smallerhydration sphere radius, high ionic mobility and lower equivalent series resistance. The charge-dischargestudies rendered a specific capacitance of 608 F/g in 1 M KOH at a current density of 0.5 mA/cm2. Bi2WO6 exhibited an excellent coulombic efficiency and specific capacitance of around 304 F/g at 3 mA/cm2inthe potential range from -0.9 to 0.1 V vs Hg/HgO in 1 M KOH electrolyte. The above results assured thatBi2WO6 could be utilized as suitable negative electrode material for supercapacitor applications and 1 MKOH could be its desirable electrolyte. © 2013 Elsevier Ltd. All rights reserved.

Rudranna N.,Rashtreeya Vidyalaya College of Engineering | Rajan J.,Indian Central Power Research Institute
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2012

Corrosion of copper due to sulphur in oil has affected the performance of transformers. The fundamental processes governing corrosion of copper due to sulphur in oil are still not well understood. In this paper, the dielectric performance of paper oil insulation under conditions of copper sulphide is discussed based on changes in capacitance, Insulation resistance and Partial discharges. Electric field analysis using FEM and PD results are employed to develop an empirical model to predict PD inception of paper oil insulation when copper sulphide is present. A simple model is also proposed to explain progressive copper sulphide migration in paper insulation. The non-linear V-I characteristics of copper sulphide is discussed to explain the breakdown of paper¿oil insulation. © 1994-2012 IEEE.

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