Informatics Publishing Limited

Ipsita Das ¹, B. Nageshwar Rao ², J. Sundara Rajan ², S. Seetharamu ², V. V. Rao ¹

Affiliations
1 Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur, West Bengal - 721302, IN
2 Central Power Reseach Institute, Bangalore - 560080, IN

Abstract

HTS (High Temperature Superconducting) cable has the ability of transmitting electrical power over long distances in an economical way, with improved stability and reliability. HTS Cable also provides a compact and low-loss transmission power line, in comparison with the conventional cable made out of copper or aluminium. The use of HTS tapes facilitates the cable operations with liquid nitrogen cooling system. A wide variety of HTS Cables with various cooling arrangements have been designed and developed. Their performance has been tested to obtain various thermo-hydaraulic and electrical data by installing the cables of different lengths in transmission and distribution networks. This paper reviews the cryogenic cooling aspects of previous and ongoing projects on superconducting cables for electrical power transmission around the world.

Keywords

Cryogenic cooling system, HTS cable, liquid nitrogen, termination

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Rajashekar P. Mandi ¹, S. Seetharamu ², Udaykumar R. Yaragatti ³

Affiliations
1 Energy Efficiency & Renewable Energy Division, Central Power Research Institute, Bangalore – 560 080, IN
2 Director, Central Power Research Institute, Bangalore – 560 080, IN
3 National Institute of Technology Karnataka, Surathakal – 575 025, IN

Abstract

Primary Air Fans are the essential auxiliary equipment to provide the primary air to lift the pulverized coal from mills to carry to burners and also to provide partial air for combustion. This paper describes various techno-economical energy conservation measures for reducing the carbon emission by improving the performance of Primary Air fans in coal fired thermal power plants based on the energy conservation/audit study conducted in 28 numbers of 210 MW power plants in India. The best operating points for pressure gain, flow, pressure drop across hydrodynamic resistive elements, equipment efficiency, power input and specific energy consumption are simulated by using MATLAB and presented in this paper with case study to validate the results. Optimizing the pressure at PA fan discharge, control of excess air, pressure drop across APH and mills and maintaining the optimum primary air pressure at mills thereby to maintain appropriate coal-air pressure at burners will help in reduction of auxiliary power of PA fans. The implementation of energy conservation measures in a typical 210 MW coal fired thermal power plant reduce the overall auxiliary power of PA fans by 0.26 % of gross energy generation and also reduce the carbon emission by 4,056 t/year.

Keywords

Energy efficiency, carbon emission, primary air fans, excess air, auxiliary power, fan efficiency

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B. Gurudatt ¹, S. Seetharamu ², P. Sampathkumaran ³, Vikram Krishna ⁴

Affiliations
1 Professor, Dept of Mechanical Engg., Bangalore Institute of Technology, Bangalore-560004, IN
2 Additional Director, MTD, Central Power Research Institute, Bangalore-560080, IN
3 Joint Director, MTD, Central Power Research Institute, Bangalore-560080, IN
4 Research Associate, RSOP Project of CPRI (Govt. of India), Bangalore-560004, IN

Abstract

Vibration is the default state of all mechanical systems that causes them to possess a natural frequency. The significance of natural frequency cannot be emphasised enough, considering the fact that its study is essential in averting resonance which causes violent swaying motions and catastrophic failures in improperly constructed structures. In case of rotating structures, the study of natural frequency is incomplete without the understanding of spin softening. This paper presents an ANSYS based analysis to study natural frequency variation due to spin softening, but in a faster and more accurate way than conventional GUI-based ANSYS analysis. The conventional GUI based ANSYS procedure is a laborious time consuming process, with the user having to perform multiple iterations of model analysis involving different rotational velocities to examine the variation of natural frequencies of the system. Through this paper, a novel way has been suggested to bring down the time and effort involved in such a study by using an advanced ANSYS feature called ANSYS Parametric Design Language (APDL). The results obtained have been found to validate spin softening.

Keywords

Finite Element Method, ANSYS Parametric Design Language, Natural Frequency, Spin Softening, Vibrations, Nelson Rotor.

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M. Siddhartha Bhatt ¹, S. Seetharamu ¹, N. Rajkumar ¹

Affiliations
1 Central Power Research Institute, Bangalore, IN

Abstract

This paper presents a methodology for assessment of annual heat rate of a coal fired thermal power unit based on a snap shot test to which various factors contributing to annual effects are added. This method is successfully used in a number of stations and represents the Unit Heat Rate (UHR) and Station Heat Rate (SHR) fairly well. This method is not a substitute for measurement of heat rate by direct measurement of coal flow and energy generated and is applicable only where direct measurement of coal flow into an individual boiler by gravimetric feeders or belt weighers is not available. This method is superior to other methods in view of its total coverage of all effects and no annual factor which affects heat rate is left out. Hence it is popularly accepted by most thermal stations. This method is superior to backward computation of UHR from SHR by apportioning.

Keywords

Coal Fired Station, Unit Heat Rate, Station Heat Rate, Coal Quality Effects, Heat Rate Degradation, Cycling Losses, Stacking Losses, Make Up Losses Central Power. Station Heat Rate, Coal Quality Effects, Heat Rate Degradation, Cycling Losses, Stacking Losses, Make Up Losses Central Power.

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B. Suresha ¹, P. Sampathkumaran ², S. Seetharamu ², Kishore ³

Affiliations
1 Department of Mechanical Engineering, National Institute of Engineering, Mysore - 570 008, IN
2 Materials Technology Division, Central Power Research Institute, Bangalore - 560 080, IN
3 Department of Materials Engineering, Indian Institute of Science, Bangalore - 560 012, IN

Abstract

Woven fabric reinforced polymer composites are attracting the attention of material scientists in recent years in view of enhancement in physical and mechanical properties as well as ease in processing. Though woven fabric type and lay out of composite is known to control the properties, the information on the tribo-performance of the woven fabric reinforced vinyl ester composites in the literature is scanty. Hence, the present investigation focuses on the vinyl ester based composite reinforced with glass fibers in one case and carbon fibers in the other case. They were made by vacuum assisted resin transfer moulding process. Further, the samples were characterized for three-body abrasive wear behaviour using dry sand rubber wheel abrasion tester with two different abrasives (silica sand and quartz). The wear data revealed that the C-V composite showed lower abrasion loss compared to G-V composite. The scanning electron microscopic pictures depicting the worn surface features supported the wear data.

Keywords

Woven Fabric Reinforced Vinyl Ester Composites, Abrasives, Three-Body Abrasive Wear, Scanning Electron Microscopy.

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P. Sampathkumaran ¹, S. Seetharamu ¹, C. Ranganathaiah ², P. K. Pujari ³, Kishore ⁴

Affiliations
1 Materials Technology Division, Central Power Research Institute, Bangalore-560080, IN
2 Department of Studies in Physics, University of Mysore, Mysore-570006, IN
3 Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai-400085, IN
4 Department of Materials Engineering, Indian Institute of Science, Bangalore-560012, IN

Abstract

The wear-resistant high chromium (Cr: 16–19 %) iron alloyed with 5 % and 10 % manganese (Mn) was produced in metal and sand moulds by induction melting technique. The erosion resistance, hardness and microstructure were evaluated both in the as-cast and heat, treated conditions. The advanced nondestructive test (NDT) methods, namely Positron Lifetime Spectroscopy (PLS) and Doppler Broadening annihilation radiation (DBAR) studies, using variable energy positron beam were made use of to study the infl uence of metallurgical parameters on the defect sensitivity in the bulk and surface of the alloy. The data reveals that as the mould type is changed from metal to sand, the hardness decreases irrespective of the sample condition (i.e. as-cast or heat treated), whereas the erosion volume loss shows an increasing trend. The light and scanning electron microscopies give good support to these data fi ndings. It is observed that faster the cooling rate (metal mould), fi ner is the carbide size precipitation on the surface of the sample. The PLS data reveals that the defect size and its concentration are higher for sand mould alloy compared to metal mould. Reasons for lower erosion loss and fewer defects of smaller sizes in metal mould are attributed to faster heat transfer in the metal mould compared to the sand mould. Further, heat treatment of the samples yielded spherodization of carbides in the matrix and some of the defects seem to have been annealed out leaving only fewer defects of smaller size in the alloy. The S-parameter profi les of 10 % Mn both in AC and HT samples are almost identical indicating near absence of any modifi cation of defect structure near the surface following heat treatment in 10 % Mn sample, while 5 % Mn samples exhibit less defect concentration both at the surface as well as in bulk which agrees with the PLS results. Hence, the 5 % Mn bearing metal mould sample in the heat-treated condition is preferred choice as it shows higher hardness, lower erosion loss as well as least defect concentration with smaller defect sizes. Based on this investigation, a good correlation among erosion loss, DBA and PLS data has emerged.

Keywords

Cr–Mn cast iron, Metal mould, Sand mould, As-cast, Heat treatment, Hardness, Erosion, Positron lifetime spectroscopy, Doppler broadening spectroscopy.

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B. G. Prashantha ¹, M. S. Govinde Gowda ², S. Seetharamu ³, G. S. L. V. Narasimham ⁴

Affiliations
1 JSS Academy of Technical Education, Uttarahalli-Kengeri Road, Bangalore-560 060, IN
2 Alva’s Institute of Engineering & Technology, Mijar, Moodbidri, D.K.-574 225, IN
3 Materials Technology Division, Central Power Research Institute, Bangalore-560 080,, IN
4 Department of Mechanical Engineering, Indian Institute of Science, Bangalore-560 012,, IN

Abstract

The performance of the thermoacoustic refrigerator depends upon a very large number of parameters, and hence the components are optimized using linear thermoacoustic theory to restrict the number of variables by dimensionless normalization technique. Since the stack is considered as the heart of the thermoacoustic refrigerator, the stack design parameters are the most signifi cant parameters for the optimal overall performance. The stack optimization result shows that a decrease in stack length and center position from the loud speaker increases stack performance. Determination of optimum stack length and center position helps in designing the refrigerator and to provide adequate space for instrumentation in practical work. The cross-sectional area of the stack and hence the stack diameter is calculated for the required cooling load capacity which is considered as the basic parameter on which the design of other components depends. The effect of mean temperature of the gas has not received attention in the literature and hence the performance of the stack at higher mean temperature of the gas is theoretically evaluated. The improvement in the stack coeffi cient of performance COPS is reported compared to published experimental optimization studies at the design conditions considered in this paper, and the results are in good agreement with past established work.

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