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Installation of Bulb Turbines in Small
Hydropower Plants: A Review
-- Sunil Kumar Singal, Anurag
Kumar and R P Saini
A large potential is available in the small hydropower schemes. There is a necessity to harness
this potential to meet the increasing rate of energy demand. Due to the growing economy and
population, demand of energy is increasing day by day. This increasing demand of electricity results in increase of
tariff rate and the present energy crisis. Previously, sufficient attention was not paid to low head
hydropower schemes due to higher cost. Now, to fill the gap between demand and supply of electricity, emphasis is
laid on the development of low head sites. Several low head turbines are available these days, out of
which, the bulb turbine is found to be the most suitable for such site conditions. Bulb turbine has a compact
form and good hydraulic features, resulting in lower civil structure cost and hydraulic losses compared to
other types of turbines employed under the similar site conditions. A lot of research work has been carried
out to improve the cavitation properties, to develop a coating for blade tip protection due to sand
erosion, investigation of bulb turbine characteristics during its operation in reversible regimes and to predict
the dynamic behavior of the bulb turbine. In the present paper, an effort has been made to present a
review of the technical and operational aspects of the bulb turbine.
© 2010 IUP. All Rights Reserved.
Modified Entry System
to Enhance the Performance of Stratified Solar Energy Storage
-- V V R L S Gangadhar, V Vasudeva Rao and K Mohan Rao
Thermal stratification in energy storage systems using water has been studied experimentally.
The experiments were conducted on two tanksone lined inside with rubber and the other lined with
fiber glassto study the effect of thermal conductivity of the lining material. The lining materials were
so chosen that they are able to withstand the presence of water and are easy to fabricate. The
experiments were carried out in both static and dynamic modes with the inlet of the hot water at the middle of
the tank. A distribution system is used to avoid the mixing of hot and cold fluids at the time of entry.
The nature of the thermal stratification and its dependence on temperature difference between hot and
cold fluids, inlet location, flow rate, thermal conductivity of the interior lining material and the
temperature variation in axial as well as radial directions were studied.
© 2010 IUP. All Rights Reserved.
Optimization of Fin Geometry
in the Internal Finned Tube
by Numerical Method
-- R Palanichamy, P Nagaraj and S Muthu Somasundaram
This paper presents a numerical simulation of laminar heat transfer in circular tube flows with
internal longitudinal fins using finite difference numerical code. Three types of fin models with three
different half-included angles have been considered. Two types of fluids (coolants), namely, water and engine
oil have been considered. Aluminium is considered the tube/fin material. The variation of thermal
conductivity of the tube materials, fluids and viscosity of the fluids with temperature is taken into account in
the solution procedure. The outer surface of the tube is exposed to constant heat flux. Steady, laminar flow
and heat transfer are assumed. It is ensured that fluids used in this study have a Reynolds number equal
to 1500. It is assumed that the flow of the fluid is completely developed locally, but undeveloped
while considering the thermal conditions. For the purpose of discretization of the governing equations,
the finite difference scheme is adopted. Each fluid has its own momentum equation and energy equation.
Both these equations of the fluid as well as the energy equation of the tube wall are solved repeatedly
and simultaneously.
© 2010 IUP. All Rights Reserved.
Numerical Analysis for Development
of Hertz Contact Stresses in Cylindrical Roller Bearing and Their
Distribution Using MATLAB
-- P H Darji and D P Vakharia
In rolling bearing analysis, Hertzian contact theory is used to compute local contact stresses.
Hertz's analysis is applied only to surface stresses caused by a concentrated force applied perpendicular to
the surface. Experimental evidence indicates that failure of rolling bearings in surface fatigue as caused by
the aforementioned load emanates from points below the surfaces. Therefore, it is of interest to
determine the magnitude of the subsurface stresses. The initiation and the propagation of the crack are
mainly effected by the stress distribution below the surfaces, especially the shear stress distribution.
Therefore, it is also important to analyze the stress condition below a contact surface and the depths where the
shear stress is the maximum. Hence, in the present work, a complete numerical analysis is carried out for
the calculation of subsurface stresses induced in the cylindrical roller bearing. Also a program is developed
in MATLAB to understand the distribution of stresses under the surface.
© 2010 IUP. All Rights Reserved.
Effect of Weld Pool Oscillation on
Mechanical Properties of Carbon Steel Weldments
-- S P Tewari
The influence of oscillation on mechanical properties of carbon steel welds was studied. The
workpieces were welded by clamping them on an oscillatory table, which was supported on two shafts mounted
on bearings. The table was rigidly coupled with a vibration exciter. After machining, the workpieces
were welded under stationary and oscillatory conditions by mounting two workpieces at a time on the
oscillatory table under different frequencies (0-400 Hz) and amplitudes (0-40 µm) of oscillations. The
oscillator/power amplifier was used to excite the electrodynamic vibration exciter at different frequencies
and amplitudes of oscillation. The frequencies and amplitudes of oscillation were measured with the help of
a vibration meter in conjunction with vibration pick-up. Test specimens for impact test, hardness test
and microstructure examination were made from the welded workpieces under stationary and
oscillatory conditions. The test specimens were tested for impact strength and hardness. Microstructure studies
were carried out on test specimens prepared for microstructure examination. Significant improvement
in impact strength and hardness of oscillatory-prepared welds was observed when compared with
these properties of stationary-prepared welds. Microstructure studies revealed that the grain structure is
fine for oscillatory-prepared weld when compared with stationary-prepared weld. Maximum
improvement in mechanical properties is obtained at 400 Hz-5 µm oscillatory condition of welding.
© 2010 IUP. All Rights Reserved.
Structural Comparison of In-Parallel Robotic Manipulators on the Basis of Compactness
-- A B Srinivasa Rao and A M K Prasad
Multi Degree of Freedom (DOF) planar kinematic chains can be considered for application as
parallel robots in view of their greater rigidity. A large number of distinct chains are available with the
same number of links and DOF for consideration as parallel structures. Hence, it becomes necessary to
know which of these chains more parallel so that the selection of these chains for the specified tasks like
workspace and rigidity becomes easy. A simple and logical method is presented in this paper to accomplish the
same. The measure of compactness developed in this paper enables comparison of distinct chains for
these characteristics.
© 2010 IUP. All Rights Reserved.
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