Department of Mechanical Engineering

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Artificial intelligence (AI) and more specific subsets of AI such as machine learning (ML) and deep learning (DL) have become widely available in recent years. Open source software packages and languages have made it possible to implement complex AI based data analysis and modeling techniques on a wide range of applications. The application of these techniques can expedite existing models or reduce the amount of physical testing required. Two data sets were utilized to examine the effectiveness of multiple ML techniques to estimate experimental outcomes and to serve as a substitute for additional testing. To achieve this complex multi-variant regressions and neural networks were utilized to create estimating models. The first data sets of interest consist of a pool fire experiment that measured the flame spread rate as a function of initial fuel temperature for 8 different fuels, including Jet-A, JP-5, JP-8, HEFA-50, and FT-PK. The second data set consists of hot surface ignition data for 9 fuels including 4 alternative piston engine fuels for which properties were not available. When properties were not available multiple imputation by chained equations (MICE) was utilized to estimate fluid properties. 10 different ML techniques were implemented to analyze the data and R-squared values as high as 92% were achieved. © 2021, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

World University root node

AIAA Scitech 2021 Forum

Artificial intelligence application in combustion modeling

This work was carried out to bring out the differences in drop weight low velocity impact behavior of two quasi-isotropic (QI) laminates. These laminates were made of AS4/914 carbon fiber reinforced plastic (CFRP). The layup sequence chosen was [0/45/-45/90]2Sand [0//90/45/-45]2S.Two types of impactors were employed for the impact tests. One is a hemispherical-end and the other is of a conical-end. Coupon level specimens were supported on all four sides during the impact test. The impact energy was calculated for the laminates and the difference, as a comparison, in each case is presented. It has been observed that the layup sequence has a significant effect on the impact resistance of the laminates under hemispherical impactor. In the case of conical impactor, both the laminates were perforated while absorbing similar energy levels. © 2021 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

An experimental study on impact behavior of quasi-isotropic CFRP laminates

The National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. © 2021, The Author(s).

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Solar Physics

Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)

Void fraction distributions in helical coils of various diameters are computationally estimated with inlet mass flux, degree of subcooling and wall superheat as inputs. The heat flux wall partitioning method in wall boiling model is used for numerical simulations of subcooled forced convection boiling. The effect of input parameters on axial variation of void fraction is studied. The void fraction in axial direction starts increasing under the presence of subcooled liquid for a tube of large coil diameter. In comparison, the increase in void fraction in axial direction for a small coil diameter tube is less but the rise in liquid temperature is larger. The reasons of the deviations are ascertained by examining the phase distribution contours. The phase distribution is found to be different at constant vapor fraction values for varying mass flux and coil diameters. Empirical relations are given for estimating void fraction based on drift flux model. From the computational results, a correlation for estimating vapor quality for helical coil under varying conditions is proposed. A correction factor that accounts for the curvature effect is incorporated for evaluating distribution parameter and drift velocity. © 2021 Elsevier Ltd

International Journal of Heat and Mass Transfer

Void fraction in helical coils during flow boiling with inlet subcooling

The paper presents details of a unique experimental facility along with necessary accessories and instrumentation for testing steam turbine cascade blades in wet and nucleating steam. A steam turbine rotor tip cascade is chosen for flow investigations. Cascade inlet flow measurements show uniform conditions with dry air and steam and dry air mixture of different ratios. Exit flow surveys indicate that excellent flow periodicity is obtained. Blade surface static pressure and exit total pressure distributions are also presented with dry air and with steam and dry air mixture of different ratios as the working medium at an exit Mach number of 0.52. © 2021, The Author(s).

SN Applied Sciences

A linear cascade tunnel for flow investigations of steam turbine rotor tip blades in subsonic nucleating flows

Ladder frame structures are used as models for multistorey buildings. These periodic structures exhibit alternating propagating and attenuating frequency bands. Of the six different wave modes of propagation, two modes strongly attenuate at all frequencies. The other four modes have nonoverlapping stop band characteristics. Thus, it is challenging to isolate such structures when subjected to broadband, multimodal base excitation. In this study, we seek to synthesize a periodic ladder frame structure that has attenuation characteristics over the maximal range of frequencies for all the modes of wave propagation. We synthesize a unit cell of the periodic structure, which comprises two distinct regions having different inertial, stiffness, and geometric properties. The eigenvalues of the transfer matrix of the unit cell determines the attenuating or the nonattenuating characteristics of the structure. A novel pictorial presentation in the form of eigenvalue map is developed. This is used to synthesize the optimal unit cell. Also, design guidelines for suitable selection of the design parameters are presented. It is shown that a large finite periodic structure comprising a unit cell synthesized using the present approach has significantly better isolation characteristics in comparison to the homogeneous or any other arbitrarily chosen periodic structure. © 2021 American Society of Mechanical Engineers (ASME). All rights reserved.

Journal of Vibration and Acoustics, Transactions of the ASME

Broadband Seismic Isolation of Periodic Ladder Frame Structure

Alpha-tocopherol, a highly active form of the antioxidant vitamin E in humans, effectively scavenges free radicals and protects the cell membranes. The aim of our study was to enhance alpha-tocopherol production in sunflower cell suspension using elicitation, precursor addition and culture condition optimization. Among various elicitors and precursors studied, sodium chloride (50 mg/L) added as elicitor and phytol (50 mg/L) added as the precursor to an untransformed sunflower cell suspension, resulted in maximum productivity enhancement of alpha-tocopherol up to 2.3- and 1.9-fold, respectively compared to a control untransformed sunflower cell suspension (0.02 mg/L/d). In separate experiments, the volumetric productivity of alpha-tocopherol in the untransformed suspension was enhanced up to 2.1- fold (0.09 mg/L/d) under optimized conditions of light intensity (3500 lx), temperature (30 °C), initial pH (6.5) and inoculum size (6 g/L). We then extrapolated these strategies (elicitor and precursor addition, culture condition optimization) for implementation on a high alpha-tocopherol yielding metabolically engineered cell suspension overexpressing 4-hydroxyphenylpyruvate dioxygenase (TS4), which resulted in enhancement (1.9-, 1.45- and 2.72-fold respectively) in the volumetric productivity of alpha-tocopherol compared to the transformed cell suspension grown under control conditions (0.18 mg/L/d). Thus, integration of bioprocess optimization and metabolic engineering resulted in a multi-fold (up to 12-fold) enhancement in alpha-tocopherol productivity in comparison to the untransformed cells. Therefore, our study demonstrates that productivity enhancement strategies like bioprocess optimisation and metabolic engineering (developed separately in parallel) for a given system can be combined to achieve maximum productivity in lesser time and cost than a relay system of optimization in long-duration plant cell cultivations. © 2021, Society for Plant Biochemistry and Biotechnology.

Department Of Biotechnology

Journal of Plant Biochemistry and Biotechnology

Multi-fold enhancement in vitamin E (alpha-tocopherol) production via integration of bioprocess optimisation and metabolic engineering in cell suspension of sunflower

Prototype Fast Breeder Reactor (PFBR) has eight Steam Generators (SG) that transfers the heat from molten sodium to the water and converts the water into super-heated steam. SG is a shell and tube type counter flow heat exchanger, which has 547 steam tubes connecting the top and bottom headers of the SG. These steam tubes are surrounded by Sodium and water/steam will be flowing in the tubes. (i.e. sodium is present in the shell side and water/steam in the tube side). The water/steam pressure will be 172 bar and any breach in one of the tubes (due to crack) will eventually result in water coming in contact with sodium and leading to violent reaction. Hence, all mitigation efforts are to be taken proactively to isolate a degrading tube(s) through proper Pre-Service inspection (PSI) and In-Service inspections (ISI) using Remote Field Eddy Current technique (RFEC). Though PSI is a comprehensive inspection, ISI is generally carried out on 10% of the total heat transfer area, i.e. about 54 tubes, through periodic inspections. A two-axis robotic system called PFBR SG Inspection System (PSGIS) is used to position the probe/cable pusher end effector system to perform the tube inspection with RFEC probe. Since there is no straight forward scheme available to optimally choose the inspection sequence, Genetic Algorithm (GA) is used to optimize the tube inspection order to reduce the duty cycle and total inspection time. In this work, we have developed a genetically evolved optimal inspection algorithm to reduce overall inspection time and the results of the investigations are presented. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Optimal Path Planning of Steam Generator Tube Inspection System’s Robotic Manipulator Using Genetic Algorithm

Labyrinth seals are the most widely used non-contact-type turbine seals. The main design concern is to prevent the seal rub with the stator in the range of operating conditions and to control the system rotordynamics. This work aims at experimentally evaluating the effect of thermal growth of labyrinth seal on the leakage flow rates and effect on vibration characteristics of the system. An experimental seal test rig for teeth on rotor (TOR)-type straight labyrinth seal with four flat tip teeth has been developed. Constant clearance between seal and stator is maintained and tested at different speeds and temperatures by varying the inlet air pressure. Leakage results are compared for the seal for the range of operating conditions and for a given seal radial clearance. In addition, vibration data are measured at various locations to understand the influence of seal on the vibration characteristics of the rotor system. It is seen that flow leakage rate and vibration of system are influenced by the pressure difference and the temperature. © 2021, Springer Nature Singapore Pte Ltd.

Experimental Study of Temperature Effect on Labyrinth Seal Leakage and Vibration Characteristics of Rotor

A three-dimensional numerical investigation of airflow through heated fin-tube heat exchangers with winglet type vortex generators is performed for both inline and staggered arrangements of circular tubes. Heat transfer augmentation of such heat exchangers strongly depends on the mounting locations of the winglet pair corresponding to tubes. The present numerical study shows the effect of location of rectangular winglet pairs (RWPs) on thermal performance for both the arrangements. Among numerous considered RWP locations, all promising locations of RWPs are identified which give higher heat transfer enhancement with less flow loss. The effects of RWP locations on flow features and heat transfer are demonstrated by streamlines and Nusselt number contours respectively. Estimation of enhancement in heat transfer is achieved by Colburn's factor and flow loss is quantified from the measured pressure drop. The thermohydraulic effect is analyzed by using the thermal performance factor. Locations of RWPs, which are capable of producing higher thermal performance, have been optimized and found that upstream RWP location, i.e. ΔX = 2.0, ΔY = ±1.25 delivers higher heat transfer enhancement with maximum thermal performance factor value for both arrangements. Evaluation of secondary flow induced by RWPs is achieved by secondary flow intensity and is correlated with heat transfer. © 2020 Elsevier Ltd