Department of Mechanical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

Leakage characteristics, influenced by centrifugal and thermal radial growth are determined computationally for a generic rotating labyrinth seal used in the gas turbine secondary air system. Three seal locations, namely, R25, R50 and R75 are represented by means of varying the rotor radius mimicking different radial positions of the seal from the shaft axis. The combined influence of seal location and its radial (Centrifugal and thermal) growth on the leakage performance is investigated for a wide-ranging speeds from 1000 to 3000 rad/s, temperatures ranging from 200 to 450 °C and pressure ratios varying from 1.1 to 2.5, for a chosen initial clearance of 500 micron. A comparison of the effect of rotation and temperature gradient among different rotors shows that the radial growth and leakage flow rates significantly vary with the increasing radius. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

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Journal of Mechanical Science and Technology

Influence of combined radial location and growth on the leakage performance of a rotating labyrinth gas turbine seal

This paper presents a coordinated motion control scheme using a disturbance observer in task space for an autonomous underwater vehicle-manipulator system (UVMS). Since, the UVMS is kinematically redundant in nature, the proposed controller permits self-motion which can be utilized to perform power efficient trajectory tracking and at the same time it also assures that the system is able to track the given desired spatial trajectory with minimal errors (despite the presence of external disturbances, system uncertainties and internal noises). The performance of the proposed coordinated motion control of the UVMS is demonstrated numerically by simulating a few underwater tasks such as payload conveyance. The system's disturbance compensation capabilities are shown and the effects of external disturbances and parameter uncertainties on the station keeping performance are also analyzed. A comparative analysis on power consumption is presented to prove the effectiveness of the proposed scheme. © 2015 Elsevier Ltd. All rights reserved.

Ocean Engineering

Coordinated motion control in task space of an autonomous underwater vehicle-manipulator system

Cell membrane proteins, both bound and integral, are known to preferentially accumulate at membrane locations with curvatures favorable to their shape. This is mainly due to the curvature dependent interaction between membrane proteins and their lipid environment. Here, we analyze the effects of the protein-lipid bilayer interaction energy due to mismatch between the protein shape and the principal curvatures of the surrounding bilayer. The role of different macroscopic parameters that define the interaction energy term is elucidated in relation to recent experiment in which the lateral distribution of a membrane embedded protein potassium channel KvAP is measured on a giant unilamellar lipid vesicle (reservoir) and a narrow tubular extension-a tether-kept at constant length. The dependence of the sorting ratio, defined as the ratio between the areal density of the protein on the tether and on the vesicle, on the inverse tether radius is influenced by the strength of the interaction, the intrinsic shape of the membrane embedded protein, and its abundance in the reservoir. It is described how the values of these constants can be extracted from experiments. The intrinsic principal curvatures of a protein are related to the tether radius at which the sorting ratio attains its maximum value. The estimate of the principal intrinsic curvature of the protein KvAP, obtained by comparing the experimental and theoretical sorting behavior, is consistent with the available information on its structure. © 2015 The Royal Society of Chemistry.

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Soft Matter

Sorting of integral membrane proteins mediated by curvature-dependent protein-lipid bilayer interaction

This experimental work investigates the evaporation rates of liquids (water, ethanol) and the flow induced thereby for both pendant and sessile droplets in high density ambient gas (sulfur hexafluoride). The flow induced around an evaporating droplet is studied at ambient pressure, in a sealed glass chamber. A steel needle and aluminium substrate are used for the pendant and sessile droplet study, respectively. The evaporation rates of the droplets are measured using shadow imaging technique. Particle image velocimetry (PIV) technique is used to measure the flow induced around the evaporating droplet. This flow is observed for both water and ethanol droplets. The flow moves upward for both pendant and sessile droplets of ethanol. In case of water, the pendant droplet induces a flow which is initially upward, but with time, its direction changes downward. The evaporation-induced flow for a sessile droplet of water is however always in the upward direction. This indicates the relative role of thermal and solutal buoyancy in the genesis of the flow. Droplet surface temperatures are also measured and discussed in this paper. © 2015 International Conference on Liquid Atomization and Spray Systems. All rights reserved.

ICLASS 2015 - 13th International Conference on Liquid Atomization and Spray Systems

Experimental study of induced flow around evaporating droplets in a high density environment

Experiments are carried out on an evaporating pendant droplet and the flow induced around the droplet due to evaporation is studied for different ambient gases. A pendant drop of ethanol is formed on a steel needle in a closed chamber maintained at room temperature (301 K). The chamber is filled with a pure gas (nitrogen, oxygen, argon or carbon dioxide). The evaporating droplet causes a flow due to thermal buoyancy (due to the temperature difference caused by evaporative cooling) and solutal buoyancy (due to the difference in molecular weight between the evaporating liquid and surrounding gas). This flow around the evaporating droplet is characterized by using PIV (particle image velocimetry) technique. From these experiments, it is observed that the flow characteristics such as the velocity and penetration length of the flow changes depending upon the molecular weight of the ambient gas. It is observed that the flow penetrates significantly in case of a lower molecular weight gas (e.g. nitrogen) and the penetration decreases with increasing molecular. This, in turn, affects the evaporation rate of the suspended droplet. © 2015 International Conference on Liquid Atomization and Spray Systems. All rights reserved.

Study on flow induced by an evaporating pendant droplet in different gases

The real contact length during the grinding process is considered as an important subject for researchers, mainly because it reflects the intensity of the responses such as grinding forces and temperature generation. In order to measure and assess the real contact length, many experimental techniques and prediction models are available in the literature. Among all these models, the model developed by Rowe and Qi is being used widely by researchers because of its ability to make close predictions with real values. Rowe and Qi coined the term called roughness factor in their model. This factor varies with grinding environments and wheel-work material combinations. To decide it for a new environment, one has to do the laborious experimental work. In this article, the roughness factor has been analysed from the grinding temperature and the heat partition ratio point of view and expressed so that without experimental work prediction of the roughness factor can be done. For this, a new factor called as the thermal factor has been proposed based on the roughness factor modifications. Its good correlation with dimensionless temperature and heat partition ratio under different grinding environments have been presented and discussed in the current communication. It seems that the thermal factor can be helped in an easy and accurate prediction of the contact length during grinding operations. © 2014 Institution of Mechanical Engineers.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

A modified model for estimating the contact length in surface grinding

Nanofluid, fluid suspensions of nanometer sized particles are revolutionizing the field of heat transfer area. Addition of nano-particles to the base fluid also alters the lubricating properties by reducing the friction. In grinding process, friction between the abrasive grains and the workpiece is a key issue governing the main grinding output. It has a direct influence on grinding force, power, specific energy and wheel wear. Moreover, high friction force increases the heat generation and lead to thermal damage in the surface layer of the ground work. Hence, any effort towards the friction control will enhance the component quality significantly. In this study, nanofluid as metal working fluid (MWF) is made by adding 0.05, 0.1, 0.5 and 1% volume concentration of Al2O3 and CuO nano-particles to the water during the surface grinding of Ti-6Al-4V in minimum quantity lubrication (MQL) mode. Surface integrity of ground surface, morphology of the wheel, and chip formation characteristics are studied using surface profilometer, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and stereo zoom microscopy (SZM). Coefficient of friction was estimated On-Machine using the measured forces. The results showed that the type of nanoparticle and its concentration in base fluid and the MQL flow rate play a significant role in reducing friction. Application of nanofluid leads to the reduction of tangential forces and grinding zone temperature. The cooling effect is also evident from the short C-type chip formation. MQL application with Al2O3 nanofluid helps in effective flushing of chip material from the grinding zone, thereby solving the main problem during the grinding of Ti-6Al-4V. © 2014 Elsevier Ltd.

International Journal of Machine Tools and Manufacture

Performance evaluation of Ti-6Al-4V grinding using chip formation and coefficient of friction under the influence of nanofluids

The current work reports quantitative OH species concentration in the cavity of a trapped vortex combustor (TVC) in the context of mixing and flame stabilization studies using both syngas and methane fuels. Planar laser induced fluorescence (PLIF) measurements of OH radical obtained using a Nd:YAG pumped dye laser are quantified using a flat flame McKenna burner. The momentum flux ratio (MFR), defined as the ratio of the cavity fuel jet momentum to that of the guide vane air stream, is observed to be a key governing parameter. At high MFRs ∼4.5, the flame front is observed to form at the interface of the fuel jet and the air jet stream. This is substantiated by velocity vector field measurements. For syngas, as the MFR is lowered to ∼0.3, the fuel-air mixing increases and a flame front is formed at the bottom and downstream edge of the cavity where a stratified charge is present. This trend is observed for different velocities at similar equivalence ratios. In case of methane combustion in the cavity, where the MFRs employed are extremely low at ∼0.01, a different mechanism is observed. A fuel-rich mixture is now observed at the center of the cavity and this mixture undergoes combustion. On further increase of the cavity equivalence ratio, the rich mixture exceeds the flammability limit and forms a thin reaction zone at the interface with air stream. As a consequence, a shear layer flame at the top of the cavity interface with the mainstream is also observed. The equivalence ratio in the cavity also determines the combustion characteristics in the case of fuel-air mixtures that are formed as a result of the mixing. Overall, flame stabilization mechanisms have been proposed, which account for the wide range of MFRs and premixing in the mainstream as well.

Combustion Science and Technology

Quantitative OH Planar Laser Induced Fluorescence Diagnostics of Syngas and Methane Combustion in a Cavity Combustor

The current work reports optical diagnostic measurements of fuel-air mixing and vortex structure in a single cavity trapped vortex combustor (TVC). Specifically, the mixture fraction using acetone PLIF technique in the non-reacting flow and PIV measurements in the reacting flow are reported for the first time in trapped vortex combustors. The fuel-air momentum flux ratio, where the air momentum corresponds to that entering the cavity through a specially-incorporated flow guide vane, is used to characterize the mixing. The acetone PLIF experiments show that at high momentum flux ratios, the fuel-air mixing in the cavity is very minimal and is enhanced as the momentum flux ratio reduces, due to a favourable vortex formation in the cavity. Stoichiometric mixture fraction surfaces show that the mixing causes the reaction surfaces to shift from non-premixed to partially-premixed stratified mixtures. PIV measurements conducted in the non-reacting flow in the cavity further reinforce this observation. The scalar dissipation rates of mixture fraction were compared with the contours of RMS of fluctuating velocity and showed very good agreement. The regions of maximum mixing are observed to be along the fuel air interface. Reacting flow PIV measurements which differ substantially from the non-reacting cases primarily because of the heat release from combustion and the resulting gas expansion show that the vortex is displaced from the centre of the cavity towards the guide vane. Overall, the measurements show interesting features of the flow including the presence of the dual cavity structure and lead to a clear understanding of the underlying physics of the cavity flow highlighting the importance of the fuel-air momentum ratio parameter.

Experimental Thermal and Fluid Science

Optical diagnostics of fuel-air mixing and vortex formation in a cavity combustor

Friction coefficient between a circular-disk periphery and V-block surface was determined by introducing the concept of isotropic point (IP) in isochromatic field of the disk under three-point symmetric loading. IP position on the symmetry axis depends on active coefficient of friction during experiment. We extend this work to asymmetric loading of circular disk in which case two frictional contact pairs out of three loading contacts, independently control the unconstrained IP location. Photoelastic experiment is conducted on particular case of asymmetric three-point loading of circular disk. Basics of digital image processing are used to extract few essential parameters from experimental image, particularly IP location. Analytical solution by Flamant for half plane with a concentrated load, is utilized to derive stress components for required loading configurations of the disk. IP is observed, in analytical simulations of three-point asymmetric normal loading, to move from vertical axis to the boundary along an ellipse-like curve. When friction is included in the analysis, IP approaches the center with increase in loading friction and it goes away with increase in support friction. With all these insights, using experimental IP information, friction angles at three contact pairs of circular disk under asymmetric loading, are determined. © 2015 SPIE.