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

This study addresses the detailed modeling and simulation of the dynamic coupling between an underwater vehicle and manipulator system. The dynamic coupling effects due to damping, restoring, and inertial effects of an underwater manipulator mounted on an autonomous underwater vehicle (AUV) are analyzed by considering the actuator and sensor characteristics. A model reference control (MRC) scheme is proposed for the underwater vehicle-manipulator system (UVMS). The effectiveness of the proposed control scheme is demonstrated using numerical simulations along with comparative study between conventional proportional-integral-derivative (PID) control. The robustness of the proposed control scheme is also illustrated in the presence of external disturbances and parameter uncertainties. © 2013 Mohan Santhakumar.

Fulltext

Modelling and Simulation in Engineering

Investigation into the dynamics and control of an underwater vehicle-manipulator system

Aero-elastic excitation can result in excessive blade vibration, which can cause blades to fail in high cycle fatigue (HCF). A severe aero-elastic failure can result in a complete blade separation and loss of thrust and loss of a blade can mean the loss of an aircraft. The primary aeromechanical design concerns are blade flutter and forced vibration that need to be quantified at the early part of engine tests. This paper details the experimental investigation carried out on a transonic shroud-less low aspect ratio fan bladed disk that experienced subsonic/transonic stall flutter and forced vibration excitation. Experiments are performed on a full scale engine using tip timing sensors flush mounted on the fan casing to characterize the vibratory responses during flutter and forced vibration conditions during engine operation. Numerical simulations are performed using computational fluid dynamic (CFD) analysis. Blade natural frequencies and mode shapes are obtained from finite element (FE) modal analysis. The experimental data captured from engine tests are used to validate the predicted results. Copyright © 2013 by ASME.

World University root node

ASME 2013 Gas Turbine India Conference, GTINDIA 2013

Flutter and forced vibration characteristics of a turbo fan bladed disk rotor

Inspired by the Brazilian disk geometry we examine the utility of an edge cracked semicircular disk (ECSD) specimen for rapid assessment of fracture toughness of brittle materials using compressive loading. It is desirable to optimize the geometry towards a constant form factor F for evaluating KI. In this investigation photoelastic and finite element results for KI evaluation highlight the effect of loading modeled using a Hertzian. A Hertzian loading subtending 4° at the center leads to a surprisingly constant form factor of 1.36. This special case is further analyzed by applying uniform pressure over a chord for facilitating testing. © 2013 Elsevier Ltd.

Engineering Fracture Mechanics

Design and analysis of novel compression fracture specimen with constant form factor: Edge cracked semicircular disk (ECSD)

The dynamic analysis of wind turbine drive train is carried out in the present paper. Gear box dynamic modelling is challenging due to the complexity involved in mathematical formulation. The mathematical model is developed based on Lagrange's formulation. The aerodynamic torque which is applied as an external load is calculated from the empirical approach. The input wind fluctuation for simulation is modelled as an average magnitude of the wind which changes slowly in time and a sinusoidal variation of wind velocity is considered. The governing differential equations of motion are solved by an implicit Newmark time algorithm. The Eigen frequencies and Eigen vectors of the model are obtained. The responses of the system in time and frequency domain are also obtained.

20th International Congress on Sound and Vibration 2013, ICSV 2013

Dynamic analysis of drive train of a fixed speed wind turbine

High Cycle Fatigue (HCF) cracks generated by blade vibration are a common source of failure in gas turbine engines. In-situ detection of blade vibration helps operators avoid engine speeds that are critical and helps infer the initiation of cracks via a change in the resonance characteristics of blades. This paper presents the results of dynamic investigations carried out on a Low Pressure Turbine (LPT) rotor through numerical and experimental analyses. In order to meet the mechanical requirements during the development phase, a numerical tool based on finite element analysis (FEA) and an experimental tool based on non-intrusive measurement technique were used. The rotor stage was characterized from resonance perspective by measuring the blade vibration frequencies, amplitudes and the rotational speed of the rotor with small proximity sensors mounted around the turbine casing. The intention was to ensure that the blade design has no critical resonances that interfere with fundamental engine orders in the operating speed range of interest. A Campbell diagram generated using the measured resonances was in good agreement with the predictions. The vibration characteristics ascertained were amplitudes, frequencies, damping and static position of all blades for identifying the initiation of cracks. Detailed analyses were performed to identify the possible causes of failures by observing the anomalies in the blade vibration behaviour and examination of foiled blades.

Condition monitoring of turbine rotor blade on a gas Turbine engine

A computational methodology is proposed to predict the running clearance of a six-tooth straight-through rotating labyrinth seal numerically by taking into account both the centrifugal and thermal growths. Four different angular velocities ranging from 0 to 3000 rad/s are chosen to study the influence of rotation on the leakage flow rate. The detailed leakage flow fields and the structural deformations are presented. Further, different pressure ratios in the range of 1.1 to 2.5 have been investigated for a wide range of initial clearances. The methodology is validated against the available data in the literature. It is found out that there is a significant reduction in leakage flow rate by incorporating the radial growth for a particular operating condition. However, for a given initial clearance, the rotation has negligible effect on the reduction in the leakage flow rate, except at pressure ratios lower than 1.7. Further; the rotation has more prominent effect for smaller clearance values. Copyright © 2013 by ASME.

Proceedings of the ASME Turbo Expo

Performance analysis of a rotating labyrinth seal with radial growth

Rotors today are made highly flexible with ever increasing demand for higher speeds, and it is important to predict the rotor dynamic behaviour accurately. Supports play an important role and influence the magnitude of vibration in response to external forces. In the present study, frequency dependent polymeric support characteristics have been found by using a multi objective optimisation scheme for minimising the unbalanced response and maximising the stability limit speed. This is an improvement over the previous papers where a simple equally weighted sum of two objective functions was used. A novel hybrid of particle swarm optimisation (PSO) and augmented Lagrangian has been used here to find the global minima. Using appropriate constraints, the slope of the support characteristics versus frequency is restricted to realistic values. Rotor systems with rolling element bearings and plain cylindrical journal bearings are studied using this approach and higher stability limits are obtained. Copyright © 2013 Inderscience Enterprises Ltd.

International Journal of Structural Engineering

Multi-objective optimisation of support characteristics of rotor bearing systems

This paper presents computational work on the biogas early phase combustion in spark ignition (SI) engines using detailed chemical kinetics. Specifically, the early phase combustion is studied to assess the effect of various ignition parameters such as spark plug location, spark energy and number of spark plugs. An integrated version of the KIVA-3V and CHEMKIN codes was developed and used for the simulations utilizing detailed kinetics involving 325 reactions and 53 species. The results show that location of the spark plug and local flow field play an important role. A central plug configuration, which is associated with higher local flow velocities in the vicinity of the spark plug, showed faster initial combustion. Although a dual plug configuration shows the highest rate of fuel consumption, it is comparable to the rate exhibited by the central plug case. The radical species important in the initiation of combustion are identified and their concentrations are monitored during the early phase of combustion. The concentration of these radicals is also observed to correlate very well with the above-mentioned trend. Thus, the role of these radicals in promoting faster combustion has been clearly established. It is also observed that the minimum ignition energy required to initiate a self-sustained flame depends on the flow field condition in the vicinity of the spark plug. Increasing the methane content in the biogas has shown improved combustion. © 2012 American Chemical Society.

Energy & fuels

Full chemical kinetic simulation of biogas early phase combustion in SI engines

Syngas is being studied extensively as an effective alternate fuel for various applications in recent times. Syngas combustion offers significant challenges because of varying compositions and considerably low calorific values. Trapped vortex combustor (TVC) is an established design in gas turbine engine combustors utilizing the RQL (rich-burn quick-quench lean-burn) strategy for achieving stable combustion under various operating conditions and meeting stringent pollution norms at the same time. TVC design consists of a cavity in which a vortex is established where rich combustion takes place. The products then mix quickly with the main flow and then the ultra lean mixture undergoes combustion. Previous studies on methane combustion in TVC have shown that this concept helps to achieve a very wide operating range of equivalence ratios with low NOx and particulate emissions. A single cavity TVC rig is used to study the combustion and mixing phenomena. Preliminary experiments on syngas combustion in TVC have shown stable combustion even for very lean equivalence ratios ($\Phi$$\sim$0.1). However, the dynamics in the cavity seem to differ considerably from previous methane combustion studies. The flame is characterised by equivalence ratio which might mean that mixing in the cavity is minimal. To understand the cavity mixing, acetone PLIF has been employed. These results show that the fuel jet momentum plays a very important role in determining the mixing within the cavity. Fuel mixing increases with the increase in fuel jet momentum as also with the guide vane air momentum. Flame luminosity images do not show a flame at the center of the cavity possibly indicating a lack of cavity recirculation vortex. Further comparison between methane and syngas can be carried out by employing parameters like jet momentum ratio.

11th International Energy Conversion Engineering Conference

Experiments on stability of syngas combustion in a trapped vortex combustor

Previous studies on a single-cavity, compact trapped vortex combustor concept showed good flame stability for a wide range of flow conditions. However, achieving good mixing between cavity products and mainstream flow was still a major challenge. In the present study, a passive mixing enhancement strategy of using inclined struts along with a flow guide vane is presented and experimentally tested at atmospheric pressure conditions. Results show excellent mixing and consequently low values of the combustor exit pattern factor in the range of 0.1 and small flame lengths (5-7 times the main-duct depth). The pressure drop is small in the range of 0.35% and NOx levels of the order of 1-2 ppm are achieved. The flame stability is excellent and combustion efficiency is reasonable in the range of 96%. The effectiveness of the proposed strategy is explained on the basis of in-situ OH chemiluminescence images and prior numerical simulations of the resulting complex flow field. The flow guide vane is observed to lead to a counterclockwise cavity vortex, which is conducive to the rise of cavity combustion products along the inclined struts and subsequent mixing with the mainstream flow. {\textcopyright} 2013 Copyright Taylor & Francis Group, LLC.