Mechanical Engineering

Helical Savonius rotor shows better performance characteristics at maximum of rotor angle compare to other conventional Savonius Rotor. However studies related to the performance characteristics and measurement in flow physics is rigorous. Staying on the all aspects of this type problem, in this analysis paper, a Computational Fluid Dynamics 3-D analysis using Fluent was made to predict the performance of two-bucket helical Savonius rotor having height of 60 cm and diameter of 18 cm with bucket twist angle 45o. The bucket design was in such a way that it connected with top and bottom circular end. The k-ε turbulence model with second order upwind discretization scheme was adopted with standard wall condition. Power coefficients (Cp) at different tip speed ratios were evaluated for rotor angle variation from 0° to 180°.Moreover, analysis was taken out in complete cycle of rotation which effect on Cp. It was found to be positive at all rotor angles and higher values of Cp were obtained at rotor angles namely 45°, 90°, 225° and 270°, which would contribute maximum power production by the rotor. In addition to these, Flow Physics of rotor was studied using 3D Model for Contour Analysis with simulation graph between Static pressure and position as well as tangential velocity with position. It was analyzed  that (1)High concentrations of pressure and velocity near the chord ends have been observed from the dynamic pressure and velocity magnitude contours, which increase with the increase of rotor angles. (2)The highest dynamic pressure and velocity magnitude at the twisted chord ends are obtained for 900 rotor angle. (3)The helical Savonius rotor with 450 bucket twist at 900 rotor angle would ensure improved performance of the rotor as a whole during its power stroke in the clockwise direction by increasing the aerodynamic torque production of the rotor.

In this Paper numerical study with swept ramp injection in supersonic combustion of hydrogen has been presented. Coupled implicit scheme with finite rate chemistry model and K-ε Turbulence model have been used for modeling of supersonic combustion. The main issue in supersonic combustion is proper mixing within short burst of time. Because of the step on the top wall of the combustor, there exists an expansion fan generated just on the top wall at the entrance of the combustor, which is interacts with the oblique shock wave formed upstream of the combustor due to the shear layer deflecting into the core flow. The static pressures along the walls are normalized by the static pressure of the core flow. The present result is very promising and demonstrates that flamelet approach seems to be feasible to high-speed flows. The stagnation temperature in the combustion reaches up to 2830 k. Fluctuation in pressure and Mach number was due to shock train. © 2014 Elixir All rights reserved ART...

Supersonic turbulent flows in a rectangular duct are characterized by secondary flows in each of the four corners of the duct. These secondary flows comprise of two counter rotating vortices forcing the fluid towards the corner. The vortices are developed as a result of the Reynolds stress gradients which exist in each of the corners. Previous studies 1,2 have primarily used intrusive techniques such as Preston/pitot tubes and hot wire in order to study the secondary flows in the corners. However use of these techniques would substantially modify the flow in low aspect ratio rectangular channels. Thus, there is a need for non-intrusive measurements to study the evolution of corner vortices in such flows. In this study we present the experimental results of stereo particle image velocimetry conducted on a Mach 2.75 flow in a low aspect ratio rectangular channel. Data is recorded at multiple cross-section planes and analyzed to study the formation of corner vortices and their effects on the structure of the mean flow field. Results show that the corner vortices are formed in the corner and then convect away from it. There is a significantly strong secondary flow associated with the corner vortices possibly causing open flow separation. The vortices significantly modify the local variation of the skin friction coefficient.

Supersonic turbulent flows in a rectangular duct are characterized by secondary flows in each of the four corners of the duct. These secondary flows comprise of two counter rotating vortices forcing the fluid towards the corner. The vortices are developed as a result of the Reynolds stress gradients which exist in each of the corners. Previous studies1,2 have primarily used intrusive techniques such as Preston/pitot tubes and hot wire in order to study the secondary flows in the corners. However use of these techniques would substantially modify the flow in low aspect ratio rectangular channels. Thus, there is a need for non-intrusive measurements to study the evolution of corner vortices in such flows. In this study we present the experimental results of stereo particle image velocimetry conducted on a Mach 2.75 flow in a low aspect ratio rectangular channel. Data is recorded at multiple cross-section planes and analyzed to study the formation of corner vortices and their effects on the structure of the mean flow field. Results show that the corner vortices are formed in the corner and then convect away from it. There is a significantly strong secondary flow associated with the corner vortices possibly causing open flow separation. The vortices significantly modify the local variation of the skin friction coefficient.

The interaction between a swept shock and the secondary flows present in the corners of a supersonic channel flow is experimentally investigated. Such an interaction presents an additional type of unit problem different than the isolated fin-type swept shock/boundary layer interaction. Stereo PIV measurements were conducted perpendicular to the principal flow direction in order to capture the secondary flows characteristic of such an interaction. Various parameters, such as vorticity, probability of flow separation, separation strength and friction coefficient are evaluated. The region of strongest separation in the flowfield generated by a coupled 3D SBLI was found to be at the location of the interaction between the vortex induced by the swept shock and the corner vortex developed in the corner of the channel. In this study, we attempt at explaining the mechanisms responsible for the observed separation.

The present study focused on CFD assessment of small shell and tube heat exchanger (SSTHX). Computational modeling and domain are initially validated with the results available in the literature for mass flow rates of 0.5, 1, 2 kg/s. Further, the flow characteristics like heat transfer coefficient, pressure drop, isotherms and secondary flow are investigated for baffle orientation of 60 0 ,120 0 and 180 0 for mass flow rates of 0.5, 1, 2kg/s. It is observed that regarding heat transfer coefficient (h, w/m2-k) variation, 1200 baffle configuration comes out as the better option in comparison with 60 0 and 180 0 .

A concept in which a human being spins a flywheel by system similar to bicycle, the rotational kinetic energy is stored in the flywheel. Such an energy source is conceptualized as Human Powered Flywheel Motor (HPFM). It caters the need of electrical motor for processes which require power in the range 3 to 9 hp for very short duration of time. As the kinetic energy is drained continuously from the flywheel the output speed of Flywheel Motor decreases continuously which in turn runs a process unit. In this paper an attempt is made to develop and experimentally validate a Novel Gearbox for Human Powered Flywheel Motor which maintains the output speed considerably constant using automatic shifting of gear pinions using flyball governor .

Use of fossil fuels has increased environmental pollution, which is posing a threat to the environment. So research is going on for harnessing human power because it is one of the resources of renewable energy. This research paper presents mathematical modeling of a novel gearbox for the human powered flywheel motor for total time required to exhaust energy stored in a spinning flywheel when it coupled to process unit through a newly developed Novel Gear box.

A system similar to bicycle used to spin a flywheel by human power and the energy is stored in the flywheel as rotational kinetic energy. Such an energy source is conceptualized as Human Powered Flywheel Motor (HPFM). It can be substituted for electrical motor for transient processes. As the energy is drained continuously from the flywheel the output speed of Flywheel Motor decreases continuously which in turn runs a process unit. An instrumentation system was designed to measure performance of Novel Gearbox for Human Powered Flywheel Motor which maintain the output speed considerably constant using automatic shifting of cluster pinions by means of flyball governor. An attempt is made to develop instrumentation system for measuring rotational speed of various shafts and know the exact time of engagement and disengagement of sliding gear-pinion pairs of novel gearbox.

This paper presents dry turning performance of coated carbide Tool on 17-4PH stainless steel bright bar (Aerospace metal), which is high strength and extremely corrosion resistant. The presence of different alloying elements and their precipitation hardening makes it a difficult to machine material.17-4PH metal available at different properties based on heat treatment conditions. But the base metal coming from mill is 17-4PH condition A, which is having hardness of 35RC. Cutting Tool Insert (KCP10B) is a specially engineered cobalt enriched carbide grade with thick MTCVD-TiCN-Al2O3-TiOCN coating for maximum wear resistance. The input parameters considered for this experiment are Velocity (V), feed (F) and Depth of cut (d). In this study, the influence of cutting parameters are aimed when turning 17-4PH condition A SS bright bar with KCP10B tool on a CNC Lathe (Maxturn plus+) without coolants. It is …

A system similar to bicycle used to spin a flywheel by human power and the energy is stored in the flywheel as rotational kinetic energy. Such an energy source is conceptualized as Human Powered Flywheel Motor ( HPFM). It can be substituted for electrical motor for transient processes. As the energy is drained continuously from the flywheel the output speed of Flywheel Motor decreases continuously which in turn runs a process unit. An instrumentation system was designed to measure performance of Novel Gearbox for Human Powered Flywheel Motor which maintain the output speed considerably constant using automatic shifting of cluster pinions by means of flyball governor. An attempt is made to develop instrumentation system for measuring rotational speed of various shafts and know the exact time of engagement and disengagement of sliding gear-pinion pairs of novel gearbox.

This paper presents a general methodology for the offline planning of trajectory of a six axis serial robot along a specified path. The objective of trajectory planning is to minimise a cost function when subjected to joint angles, joint velocities, acceleration, jerks, torques and gripping force constraints by considering dynamic of the robot. A trigonometric spline is used to represent the trajectory. This non-linear constrained optimisation problem consists of 6 objectives, 67 constraints and 48 variables. The cost function is a weighted balance of travelling time, actuator torques, singularity avoidance, joint jerks, joint accelerations and gripping force. The optimisation problem is solved by using two methods, namely sequential quadratic programming and genetic algorithm. The proposed methodology is implemented for trajectory planning of six degree of freedom industrial robot and results obtained with two optimisation techniques are compared.

The eld of autonomous robotics is growing at a rapid rate. The trend to use increasingly more sensors in vehicles is driven both by legislation and consumer demands for higher safety and reliable service. Nowadays, robots are found everywhere, ranging from homes, hospitals to industries, and military operations. Autonomous robots are developed to be robust enough to work beside humans and to carry out jobs efciently. Humans have a natural sense of understanding of the physical forces acting around them like gravity, sense of motion, etc. which are not taught explicitly but are developed naturally. However, this is not the case with robots. To make the robot fully autonomous and competent to work with humans, the robot must be able to perceive the situation and devise a plan for smooth operation, considering all the adversities that may occur while carrying out the tasks. In this thesis, we present an autonomous mobile robot platform that delivers the package within the VNIT campus w...

Investigations of modal parameters for a mistuned packet of turbine blades due to lacing wire damage are reported using analytical and numerical studies with a simplified model. The turbine blade is assumed to be an Euler-Bernoulli beam connected with a lacing wire which is modeled as a mass less linear elastic spring. Thus, the blade is considered as a continuous system and lacing wire as a discrete system. The analytical results using Eigen value analysis are compared with numerical results obtained using commercial finite element package. In real life situation, though not reported in the literature, it is the failure of lacing wire that occurs quite often compared to the turbine blade and acts as precursor to the subsequent blade damage if it goes undetected. Therefore, studying the modal parameters of the grouped turbine blades in the context of lacing wire failure becomes important. The effect of variation of lacing wire location and stiffness indicative of damage resulting in the loss of stiffness on modal parameters is investigated. The study reveals a lot of fundamental understandings pertaining to dynamic behavior of grouped blades compared to the stand-alone blade under the influence of damaged lacing wire.