Faculty Publications

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Publications by NITK Faculty

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    Failures Investigation of Marine Propellers in Corrosive Environments
    (Springer Nature, 2021) Mirashi, V.U.; Johnson, S.; Hegde, S.; Vijayan, V.; Cadambi, S.
    Marine corrosion failure of fishing boat propellers made of cast Nickel Aluminium Bronze were investigated. Specimens extracted from the corroded propellers were characterized by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The alloy comprises several Fe3Al (κ1, κ2, κ4), NiAl (κ3) type intermetallic precipitates and β’ martensite embedded in Cu-rich α-matrix. Transverse sections of the corroded region showed two distinct zones; a non-uniform top oxide layer and a partially corroded zone with selective corrosion of the β’ martensite which run parallel to the κ3 precipitates. From the microstructural analysis it is adjudged that the aggressive local corrosion of the matrix is preceded by cracking of the oxide by erosion, cavitation, etc., A slow growth of the oxide layer follows that reduces the corrosion rate. However, the corrosion cycle repeats on erosion or cracking of the oxide layer when the propeller is used in marine waters. Coupon specimens immersed in actual marine conditions is presented that supports the above theory. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Basic concepts of ultrasound and its effects on fuel processing
    (Bentham Science Publishers, 2023) Poddar, M.K.; Dikshit, P.K.; Chakma, S.
    Ultrasound-assisted technique is well-known for process intensification via chemical and physical changes under the influence of acoustic cavitation. Acoustic cavitation is the phenomenon of nucleation, growth, and collapse of cavitation bubbles into a liquid medium that augments the reaction kinetics and the final process yield. This chapter provides a fundamental and detailed understanding of the acoustic cavitation phenomenon. It includes the history and origin of the acoustic wave and its formation, the concept of cavitation bubbles, bubble nucleation and growth mechanism, cavitation effects, and its types. Numerous process parameters, such as applied frequency, intensity, temperature, dissolved gas content, etc., also directly or indirectly influence the cavitation threshold are also highlighted. Further, the ultrasound's physical and chemical effects involving various chemical and biochemical processes to enhance the process yield are also reviewed. The mode of generation of ultrasound energy and its measurement technique are also briefly discussed. Finally, an overview of modeling and simulation of radial motion of single bubble growth, its oscillation in both ultrasound-assisted and conventional systems, and bubble growth rate under rectified diffusion are also discussed in detail. © 2023 Bentham Science Publishers. All rights reserved.
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    Characterization of sealing ring cavitation in centrifugal pumps with water and viscous oil
    (Begell House Inc., 2010) Nair, K.G.; Ashok Babu, T.P.A.
    This research paper presents characterization of sealing ring cavitation in centrifugal pumps with water and viscous oil. The paper discusses development of theoretical formulation for sealing ring cavitation and simulation using software model along with experimental validation. The pump performance test results and its standard clearance for the sealing ring are used to simulate the theoretical model. The study is extended for pumps with SAE-30 lubricating oil. The simulation results present the variation of downstream pressure with different sealing ring dimensions in pumps. The value of downstream pressure determines the possibility of occurrence of cavitation at the clearance. The theoretical formulation developed is validated by using a venturi cavitation test set up. Clearances equivalent to various sealing ring dimensions are made at the test section using different hemispherical models. Theoretical formulation for downstream pressure at the clearance of venturi test section is derived using the test set up details and pump specification. The clearance cavitation coefficients as per K. K. Shelneves equation are obtained from theory as well as from experimentation and compared. The phenomena of cavitation damages the sealing ring which results a fall in performance of the pump. However this research work lead to the prediction of sealing ring cavitation in centrifugal pumps handling water and oil enabling the replacement of sealing ring before affecting cavitation damage. © 2010 Begell House, Inc.