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

The present investigation has been made on the influence of temperature on the workability behavior, stresses and hardness of sintered Al-4%B4C at a strain rate of 0.1s-1 during upsetting. Al-4% B4C preforms were prepared with 90% of initial preform density and sintered at 550±10oC about 60 min. These sintered preforms were compressed in a hydraulic press at a strain rate of 0.1 s-1 until the initiation of the cracks appears on the free surface. The various stresses (σz, σθ, σm, σeff), formability stress index (β) and stress ratio parameters (σz/σeff, σm/σeff, σθ/σeff) were calculated and correlated with the true axial strain (Ez). Also the effect of different deformation temperatures on the hardness of Al-4%B4C preforms was studied in detail. © 2017 The Authors.

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Procedia Engineering

Influence of Temperature on the Workability and Hardness of Sintered Al-4%B4C in Upsetting Test

Simulations and exhaust measurements of temperature and pollutants in a syngas-fired model trapped vortex combustor for stationary power generation applications are reported. Numerical simulations employing Reynolds-averaged Navier-Stokes (RANS) and large eddy simulations (LES) with presumed probability distribution function (PPDF) model were also carried out. Mixture fraction profiles in the trapped vortex combustor (TVC) cavity for nonreacting conditions show that LES simulations are able to capture the mean mixing field better than the RANS-based approach. This is attributed to the prediction of the jet decay rate and is reflected on the mean velocity magnitude fields, which reinforce this observation at different sections in the cavity. Both RANS and LES simulations show close agreement with the experimentally measured OH concentration; however, the RANS approach does not perform satisfactorily in capturing the trend of velocity magnitude. LES simulations satisfactorily capture the trend observed in exhaust measurements which is primarily attributed to the flame stabilization mechanism. In the exhaust measurements, mixing enhancement struts were employed and their effect was evaluated. The exhaust temperature pattern factor was found to be poor for baseline cases, but improved with the introduction of struts. NO emissions were steadily below 3 ppm across various flow conditions, whereas CO emissions tended to increase with increasing momentum flux ratios (MFRs) and mainstream fuel addition. Combustion efficiencies ∼96% were observed for all conditions. The performance characteristics were found to be favorable at higher MFRs with low pattern factors and high combustion efficiencies.

Journal of Engineering for Gas Turbines and Power

Numerical and Experimental Studies on a Syngas-Fired Ultra Low NOx Combustor

Flame quenching by heat loss to a surface continues to be an active area of combustion research. Close wall temperature measurements in an isothermal wall-stabilized flame are reported in this work. Conventional N2-vibrational Coherent Anti-Stokes Raman Scattering (CARS) thermometry as close as 275 $\mu$m to a convex wall cooled with water has been carried out. The standard deviation of mean temperatures is observed to be $\sim$6.5% for high temperatures (>2000K) and $\sim$14% in the lower range (<500K). Methane/air and ethylene/air stoichiometric flames for various global strain rates based on exit bulk velocities are plotted and compared. CH* chemiluminescence is employed to determine the flame location relative to the wall. Flame locations are shown to move closer to the wall with increasing strain rates in addition to higher near-wall temperatures. Peak temperatures for ethylene are considerably higher ($\sim$250-300K) than peak temperatures for methane. Preheat zone profiles are similar for different strain rates across fuels. This work demonstrates close wall precise temperature measurments using CARS.

AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting

Temperature measurements in a wall stabilized steady flame using CARS

This article reports on the quantification of the heating induced by nanosecond repetitively pulsed (NRP) glow discharges on a lean premixed methane-air flame. The flame, obtained at room temperature and atmospheric pressure, has an M-shape morphology. The equivalence ratio is 0.95 and the thermal power released by the flame is 113 W. The NRP glow discharges are produced by high voltage pulses of 10 ns duration, 7 kV amplitude, applied at a repetition frequency of 10 kHz. The average power of the plasma, determined from current and voltage measurements, is 1 W, i.e., about 0.9% of the thermal power of the flame. Broadband vibrational coherent anti-Stokes Raman spectroscopy of nitrogen is used to determine the temperature of the flame with and without plasma enhancement. The temperature evolution in the flame area shows that the thermal impact of NRP glow discharges is in the uncertainty range of the technique, i.e., ±40 K.

Combustion Science and Technology

Investigation of Gas Heating by Nanosecond Repetitively Pulsed Glow Discharges Used for Actuation of a Laminar Methane-Air Flame

A generalised three-dimensional solver based on unstructured grid methodology has been developed for electrohydrodynamic flows. The Navier-Stokes equations with electrical field source term are solved in conjunction with the coupled electrical potential and ion charge density equations in a finite volume framework. An iterative boundary condition for updating the value of charge density on the discharge electrode is used while solving the electrical field equations. The solver is validated with available literature and the good agreement is found. © Springer India 2017.

Lecture Notes in Mechanical Engineering

Computation of flow coupled with the electric field on unstructured grid

In the present work for numerically investigating the interfacial flows, an algebraic Volume of Fluid technique has been implemented over hybrid unstructured meshes. Following the work of Dalal et al. (Numer Heat Transf Part B 54 (2):238–259, 2008 [2]), the governing equations are discretised by cell centered finite volume method wherein pressure-velocity coupling has been achieved by momentum interpolation due to Rhie and Chow (AIAA J 21:1525–1532, 1983 [12]). The binary fluid problem is represented by a single fluid formulation with a fluid property jump at the interface. Two schemes namely NVD based GAMMA scheme (Jasak, Int J Numer Meth Fluids 31:431–449, 1999 [7]) and Convergent and Universally Bounded Interpolation Scheme for the Treatment of Advection (CUBISTA) (Alves et al., Numer Heat Transf 49:19–42, 2006 [1]) has been incorporated into an in-house fully coupled Navier-Stokes solver. These schemes are validated with the published results of collapse of water column also known as dam break problem by Martin and Moyce (Math Phys Sci 244:312–324, 1952 [9]) and Rayleigh-Taylor instability (Tryggvason, J Comput Phys 75:253–282, 1988 [13]). The results are found to be in good agreement. © Springer India 2017.

A hybrid grid based algebraic volume of fluid method for interfacial flows

This paper addresses a 2PRP-2PPR planar parallel manipulator and, its implementation in the design and development of a new lower limb rehabilitation robot (LLRR). The difficulty and limitation of the existing mechanisms has been analysed and a new mechanism is proposed. Some limitation of the proposed manipulator, namely limited effective workspace, has also been overcome by gear arrangement to make it suitable for the application. The proposed mechanism is able to perform like a serial LLRR with the same clinical space with advantages of parallel manipulators like better accuracy, speed and stiffness. The proposed manipulator consist of a vertical planar parallel manipulator (2PRP-2PPR)which is driver mechanism and a lower limb orthosis which is driven and actuator-free mechanism has a RRR serial planar configuration, is designed to treat the patient in sitting/lying postures. Validation of the functional design and working of the proposed system has been done analytically by using the clinical gait pattern data. © Springer International Publishing Switzerland 2017.

Mechanisms and Machine Science

A 2PRP-2PPR planar parallel manipulator for the purpose of lower limb rehabilitation

This paper presents the development of a SMA (shape memory alloy) spring actuation based 3-dof (three degree of freedom) 3PRP (prismatic-rotary-prismatic) planar parallel manipulator where each limb (3 stands for three limbs) of the manipulator having PRP joint arrangement. The active prismatic actuators are made of SMA springs. This 3PRP planar parallel manipulator has a parallel structure including a fixed base and a moving platform (end-effector) and placed in xy plane. Base and the end-effector of the manipulator are linked together by three limbs consisting of prismatic-revolute-prismatic (PRP) joint arrangement in which each limb has one active prismatic joint made of SMA springs. Forward and inverse kinematic analysis of the 3PRP planar parallel manipulator has been studied. Suitability and usage of SMA spring based actuators replacing highly bulky prismatic actuators has been investigated. In addition, the detailed study of the actuation or deflection of the SMA springs in the application of driving the manipulator has been presented experimentally. From the experimental results, it is observed that the 3PRP manipulator associated with SMA spring based actuators has larger workspace to total area required ratio as all the three active prismatic actuators actuates properly and in same time. In overall, this paper shows the 3PRP planar parallel manipulator associated with SMA spring actuators is superior alternatives to conventional motion stages for high precise micro-positioning and tracking applications.

ACM International Conference Proceeding Series

Development of a planar 3prp parallel manipulator using shape memory alloy spring based actuators

A coupled theoretical and experimental study was undertaken to examine the impact of plate thickness, alloy strength and processing conditions on the susceptibility of tool failure in friction stir welding of AA7075 and AA7039. A three-dimensional steady-state heat transfer model was used to compute the temperature field in tool and workpiece alloy. The torque and traverse force, and the mechanical stresses on the tool were estimated analytically and validated with the corresponding experimentally measured results for a range of processing conditions. The propensity of the tool to failure was assessed by a durability factor, which was estimated as a ratio of tool material strength at the computed peak temperature and the resultant mechanical stress on the tool probe. The results showed that rise in welding speed, alloy strength and plate thickness could lead to increased mechanical stresses on tool probe, reduced durability factor and enhanced susceptibility of tool failure. The overall methodology was used successfully to provide the underlying basis for two reported practical examples of tool failures in friction stir welding. © 2016 Elsevier B.V.

Journal of Materials Processing Technology

Probing torque, traverse force and tool durability in friction stir welding of aluminum alloys

Friction hydro pillar processing (FHPP) is a novel technique to fill in crack-holes in thick-walled metal structures by an external stud and forming a solid-state bond between the stud and the metal substrate. During the process, the stud is rotated against the crack-wall to facilitate friction heating and flow of plasticized material for proper filling of the crack-hole. We present here a coupled experimental and numerical study on FHPP of ASTM A36 steel to understand the effect of processing conditions on the joint structure and properties. An axi-symmetric heat transfer analysis is carried out to compute the temperature field. The computed thermal cycles are used to estimate the hardness distribution across the joint. The estimated thermal cycles and hardness distribution are tested with the corresponding experimentally measured results. © 2017 Institute of Materials, Minerals and Mining. Published by Taylor & Francis on behalf of the Institute.