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

In the present study, influence of microstructure on high temperature dry sliding wear behavior of nickel base hardfaced coating is discussed in detail. Using plasma transferred arc (PTA) welding process, coating of nearly 4 to 5. mm thickness was deposited on 316 L (N) stainless steel substrate without any defects. The as-deposited coating contains large quantity of precipitates (range from 100nm to 20μm in size) in the γ-nickel matrix which increased the hardness significantly. Sliding wear tests were carried out on the coating for different sliding distances at room temperature (RT) and also higher temperature (573. K, and 823. K). Results showed that the wear resistance of coating improved significantly with increase in test temperature, and the high wear resistance was observed at 823. K. The coating exhibited different operating wear mechanisms depending on sliding distances and also test temperature. The wear mechanisms were identified based on friction and wear values along with worn surface analysis. The operating wear mechanisms at 823. K are adhesion at shorter sliding distance and tribo-oxidation at longer sliding distance. © 2010 Elsevier B.V.

World University root node

Surface and Coatings Technology

The microstructure and high temperature wear performance of a nickel base hardfaced coating

Master of Engng dissertation. IISc Mechanical Engng

Theoretical and experimental analysis of cracked disks

In the present work, detailed laser-based diagnostic experiments were conducted to characterise the spray from low pressure 2-hole and 4-hole Port Fuel Injection (PFI) injectors. The main objective of the work included obtaining quantitative information of the spatio-temporal spray structure of such low-pressure gasoline sprays. A novel approach involving a combination of techniques such as Mie scattering, Granulometry, and Laser Sheet Dropsizing (LSD) was used to study the spray structure. The droplet sizes, distributions with time, Sauter Mean Diameters (SMD), droplet velocities, cone angles and spray tip penetrations of the sprays from the injectors were determined. The spray from these injectors is found to be `pencil like' and not dispersed as in high pressure sprays. The application of the above mentioned techniques provides two-dimensional SMD contours of the entire spray at different instants of time, with reasonable accuracy.

INTERNATIONAL JOURNAL OF SPRAY AND COMBUSTION DYNAMICS

Laser-based spatio-temporal characterisation of Port Fuel Injection (PFI) sprays

In the present study, PFI injectors which are suitable for small engines were characterized to study the effect of pressure on various spray parameters. Two plate-type PFI injectors were studied: one with two orifices and the other with four orifices. The nozzle orifice sizes were determined by microscopy. The fuel quantity injected at pressures of 200 kPa, 500 kPa and 800 kPa, were measured by collecting the fuel, for injection pulses of different durations. The spray structure of the PFI sprays was determined by shadowgraphy. A single pulsed Nd:YAG laser in conjunction with fluorescent diffuser optics was used as the light source for shadowgraphy. Backlit images of the spray were obtained at various times after the start of injection using a CCD camera. This was done for sprays at different pressures and different pulse durations. The spray angle and spray tip penetration were determined from the processed shadowgraphy images. The backlit images also showed insights into the development of the spray. It was observed that coalescence occurs, with liquid from the orifices merging early on to form a single core. Droplet sizes were determined at various times after the start of injection. Shadowgraphy on small regions of the spray (∼ 1.4 mm × 2.5 mm) was performed with backlighting with a pulsed laser and dye plates and a long focal length microscope attached to a CCD camera. The droplet size distributions and variation of Sauter mean diameter (SMD) with time were determined at different pressures and spray durations. The SMDs were found to reduce significantly when the pressure was changed from 200 kPa to 800 kPa, with values dropping from around 140-180 micron to around 80-100 micron. The 4-hole injector was found to give smaller droplet sizes than the two-hole injector at the same injection pressures. Copyright © 2010 SAE International and Copyright © 2010 SAE Japan.

SAE Technical Papers

Optical characterization of PFI Gasoline sprays: Effect of injection pressure

Electrochemical machining is a non conventional machining process, used for machining complicated shapes, high strength and high temperature materials. The selection of proper process parameters for electrochemical machining process is crucial to have the efficient and high quality output. In this study, the Taguchi method, a powerful tool for optimization is used to find the optimal machining parameters for electrochemical machining. Based on this technique, experiments were designed and conducted on Inconel 625 alloy to machine circular holes using electrochemical machining with NaCI solution as electrolyte and electrolyte grade copper as tool. An orthogonal array, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) were employed to investigate the optimum process parameters and their effect on the response parameters i. e. , material removal rate and overcut. Through this study not only the optimal machining parameters are obtained, but also the main process parameters that affect the machining performance in electrochemical machining are found. Conformation tests are also conducted to verify the experimental results.

16th International Symposium on Electromachining, ISEM 2010

Design and optimization of process parameters in electrochemical machining of inconel 625 alloy using Taguchi method

The problem of trajectory tracking control of an underactuated autonomous underwater robot (AUR) in a three-dimensional (3-D) space is investigated in this paper. The control of an underactuated robot is different from fully actuated robots in many aspects. In particular, these robot systems do not satisfy Brockett's necessary condition for feedback stabilization and no continuous time-invariant state feedback control law exists that makes a specified equilibrium of the closed-loop system asymptotically stable. The uncertainty of hydrodynamic parameters, along with the coupled, nonlinear dynamics of the underwater robot, also makes the navigation and tracking control a difficult task. The proposed hybrid control law is developed by combining sliding mode control (SMC) and classical proportional-integral-derivative (PID) control methods to reduce the tracking errors arising out of disturbances, as well as variations in vehicle parameters like buoyancy. Here, a trajectory planner computes the body-fixed linear and angular velocities, as well as vehicle orientations corresponding to a given 3-D inertial trajectory, which yields a feasible 6-d.o.f. trajectory. This trajectory is used to compute the control signals for the three available controllable inputs by the hybrid controller. A supervisory controller is used to switch between the SMC and PID control as per a predefined switching law. The switching function parameters are optimized using Taguchi design techniques. The effectiveness and performance of the proposed controller is investigated by comparing numerically with classical SMC and traditional linear control systems in the presence of disturbances. Numerical simulations using the full set of nonlinear equations of motion show that the controller does quite well in dealing with the plant nonlinearity and parameter uncertainties for trajectory tracking. The proposed controller response shows less tracking error without the usually present control chattering. Some practical features of this control law are also discussed. © 2010 Koninklijke Brill NV, Leiden and The Robotics Society of Japan.

Advanced Robotics

Investigations on the hybrid tracking control of an underactuated autonomous underwater robot

The dynamics and diagnostics of cracked rotors have been gaining importance in recent years. The present work deals with the detection of crack in rotor system and determination of crack parameters i.e., position of crack, depth of crack using Artificial Neural Networks (ANN). The detection of crack is based on the Continuous Wavelet Transform (CWT) plots with 1/3 and 1/2 critical peaks as the crack indicators. The input to the CWT is the transient data which is obtained from the cracked run-up rotor with stepped acceleration, which is encountered in real time situations during the operation of steam turbines, aero-engines etc. The amplitudes of sub-critical and critical peaks of the CWT plots are fed as input to the neural network to obtain the crack parameters. The new concept in the present work is that both qualitative and quantitative treatment has been applied to diagnose the system and by using a simple data modification technique the number of sensors have been deduced from 21 to 3 for a 20 element FEM rotor model. © KRISHTEL eMAGING SOLUTIONS PRIVATE LIMITED.

Advances in Vibration Engineering

Shaft crack identification using artificial neural networks and wavelet transform data of a transient rotor

Problem statement: Conventional Proportional-Integral-Derivative (PID) controllers exhibit moderately good performance once the PID gains are properly tuned. However, when the dynamic characteristics of the system are time dependent or the operating conditions of the system vary, it is necessary to retune the gains to obtain desired performance. This situation has renewed the interest of researchers and practitioners in PID control. Self-tuning of PID controllers has emerged as a new and active area of research with the advent and easy availability of algorithms and computers. This study discusses self-tuning (auto-tuning) algorithm for control of autonomous underwater vehicles. Approach: Self-tuning mechanism will avoid time consuming manual tuning of controllers and promises better results by providing optimal PID controller settings as the system dynamics or operating points change. Most of the self-tuning methods available in the literature were based on frequency response characteristics and search methods. In this study, we proposed a method based on Taguchi's robust design method for self-tuning of an autonomous underwater vehicle controller. The algorithm, based on this method, tuned the controller gains optimally and robustly in real time with less computation effort by using desired and actual state variables. It can be used for the Single-Input Single-Output (SISO) systems as well as Multi-Input Multi-Output (MIMO) systems without mathematical models of plants. Results: A simulation study of the AUV control on the horizontal plane (yaw plane control) was used to demonstrate and validate the performance and effectiveness of the proposed scheme. Simulation results of the proposed self-tuning scheme are compared with the conventional PID controllers which are tuned by Ziegler-Nichols (ZN) and Taguchi's tuning methods. These results showed that the Integral Square Error (ISE) is significantly reduced from the conventional controllers. The robustness of this proposed self-tuning method was verified and results are presented through numerical simulations using an experimental underwater vehicle model under different working conditions. Conclusion/Recommendations: By using this scheme, the PID controller gains are optimally adjusted automatically online with respect to the system dynamics or operating condition changes. This technique found to be more effective than conventional tuning methods and it is even very convenient when mathematical models of plants are not available. Computer simulations showed that the proposed method has very good tracking performance and robustness even in the presence of disturbances. The simple structure, robustness and ease of computation of the proposed method make it very attractive for real time implementation for controlling of underwater vehicle and it offers a chance to extend the same technique to the three dimensional vehicle tracking control as well. © 2010 Science Publications.

Journal of Computer Science

A self-tuning proportional-integral-derivative controller for an autonomous underwater vehicle, Based on Taguchi method

Modern rotating machinery is prone to fatigue cracks due to the severe working and continuously varying loading conditions. To avoid failure of the rotating systems due to these cracks, the system needs to be continuously monitored. The reliability of the machinery can be enhanced with the fault identification at the early stages of their occurrence. Model based methods are used for crack identification in rotating systems successfully. Model based methods are of different types. One of the methods, the equivalent loads minimization method is studied here. It has a limitation that the error in identified crack depth increases with decrease in number of measured vibrations. In the present work, the theoretical fault model loads used in least squares minimization algorithm are transformed using modal expansion to reduce error in the identified fault parameters. The crack is identified accurately even in the case of less number of measured vibrations. The method is applied for crack identification in a centrifugal pump rotor using transverse vibrations. The results presented are obtained purely from FEM simulations. Copyright © 2010 by ASME.

Proceedings of the ASME Turbo Expo

Model based shaft crack identification in rotating machinery

A methodology is developed for the analysis of diesel engine in-cylinder processes and combustion. Beginning from CAD data of the engine geometry, the methodology involves use of a commercial code AVL FIRE for simulation of suction stroke and an open-source code KIVA-3V for simulation of the closed-valve part of the diesel cycle. For this, an algorithm is first developed to map a generalised three-dimensional Computational Fluid Dynamics (CFD) solution from an unstructured mesh in AVL FIRE to a structured mesh in KIVA-3V to provide initial conditions for the closed-valve simulations. For simulation of diesel combustion process, an integrated KIVA-3V code is developed by incorporating two well-validated models into the standard code: the Shell hydrocarbon auto-ignition model for simulation of diesel auto-ignition under conditions of high temperature and pressure and the Characteristic-time model for simulation of subsequent diesel combustion. The integrated code is validated and calibrated against experimental pressure measurements in a naturally aspirated direct injection diesel engine. These tools are then used for exploring the potential of a constant-speed, turbocharged diesel engine towards emission reduction. The case study involves combustion simulations for exploring multiple injection strategy for the engine concerned. Copyright © 2010 Inderscience Enterprises Ltd.