Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 227-236
Numerical simulation of supersonic
turbulent jets impinging on
an axisymmetric deflector
The objective of this work is to model under- and over-expanded turbulent compressible supersonic jets impinging on an axisymmetric jet deflector. The closure of the system of equations is achieved using a two-equation turbulence model with, an optional compressibility correction. A finite-volume discretization is carried out in spatial coordinates to compute inviscid and viscous flux vectors. A multistage Runge-Kutta time stepping scheme is used to obtain a steady state solution. The numerical algorithm is developed by taking into consideration structured grid arrangement. The numerical results are obtained for nozzle exit Mach number of 2.2 and 3.1, exit to ambient pressure ratio of 0.8 and 1.2, and at different distance from nozzle exit to the apex of the deflector. The numerical scheme is shown to be computationally fast, easy to program and efficient. The centre line pressure variation inside the jets differs in the presence of the jet deflector. The numerical results are compared with the available experimental data and are found to be in reasonably good agreement.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 237-249
Leak-before-break analysis of
shell-nozzle junction of steam generator
Investigations on
leak-before-break analysis of shell-nozzle junction of steam generator (SG) are
presented here. Steam generators are integral parts of the nuclear power
plants. So, to prevent the catastrophic failure of such components nowadays,
leak-before-break (LBB) concept is used. There are three levels of checking LBB
behavior, namely leve1 1,
level 2 and level 3. Level 1 is inherent in the design philosophy of ASME Sec.
III, which is normally followed in the pipe design. This paper describes level
2 and level 3 LBB analysis for SG shell-nozzle junction.
In level 2, crack propagation
analysis of surface crack at the most critical locations of SG shell-nozzle
junction was carried out, showing thereby, that crack growth is insignificant
during the complete one power plant life cycle. Crack propagation analysis was
conducted as defined in RCC-MR code. The methodology based on Paris law, which
needs evaluation of effective DK (DKeff) taking into account effect of plasticity and crack closure
coefficient, was used.
In level 3, through-wall leak size cracks (LSC) were postulated at the
most critical locations and crack instability analysis was carried out under
maximum credible loading conditions (e.g. earthquake). For crack instability
analysis, various steps namely determination of leakage area and leak size crack
(LSC) using leak-rate model, elastic-plastic fracture mechanics analysis (J-integral/tearing modulus approach) and
limit load analysis (twice elastic slope method) were carried out. For the
evaluation of critical load, elastic-plastic fracture mechanics analysis and
for the evaluation of limit load, limit load analysis were carried out. Since
no geometrical simplifications were possible for SG shell-nozzle junction,
complete three-dimensional non-linear finite element analysis was performed.
And, it has been proved that, because of postulated cracks, SG shell nozzle
junction would not fail in ductile tearing and plastic collapse under maximum
credible load that may act during a safe shutdown earthquake (SSE).
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 250-254
Lean-knock limits for dual-fuel
combustion of natural gas in diesel engine
The use of natural gas as energy source for internal combustion (IC)
engines has an attractive intuitive appeal due to its environmentally friendly
nature. Whilst successful commercialisation of this energy source, it requires
that it offers cost advantages over competing fuels. It has been considered as
potential source of fuel energy for compression ignition (CI) engines due to
its high octane value (RON 131) necessitating for the use of high compression
ratios. In this paper, the operating range (lean-knock limits) for dual-fuel
combustion of natural gas in an unmodified diesel engine has been investigated.
The factors influencing the knock and lean limits have been identified. The
delay period has been noted to feature in defining knock limit and high
concentrations of hydrocarbon (HC) in the exhaust. The cylinder pressure diagram
indicated longer ignition delay and reduced maximum peak cylinder pressure when
operating beyond these limits, with an increased pressure fluctuation.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 255-259
On improving the spectral purity
of the regenerated clock signal in a data clock ecovery circuit
The present paper reports a novel phase
locked loop (PLL) based clock recovery circuit, which makes use of a sample and
hold circuit to improve the spectral characteristics of the regenerated clock
signal. Experimental results are incorporated to verify the predicted operation
of the system.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 260-264
Determination of bus security
governed by sensitivity indicator in a reactive power constraint longitudinal
power supply (LPS) system
Degree of weakness of a bus in a longitudinal power supply (LPS) system,
governed by the reactive power sensitivity of the concerned bus being
investigated, simulations have been performed in order to exhibit the variation
of real and reactive power sensitivity with respect to bus voltages for
variations in load levels of that bus. The effects of Static Var Compensator
(SVC) application in capacitive as well as in inductive modes of operation on
the bus power sensitivities, the variation in corresponding margins of bus
power sensitivities, as well as on bus voltage magnitudes are reported here.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 265-268
Amplification and attenuation of
acoustic waves in silicon inversion layer of MOSFET structure
Calculations of electron-acoustic phonon interaction and phonon
absorption of Si(001) inversion layer have been studied at low temperature for
the MOSFET structure by using displaced Fermi-Dirac distribution function. The
strong dependence of normalized dc field on emission and absorption of phonons
has been analyzed. If the electron drift velocity is higher (smaller) than
sound velocity, phonon emission (absorption) takes place. The numerically
calculated phonon absorption shows a good agreement with the existing
experimental data. The dependence of layer thickness on scattering rate has
been discussed.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 269-274
Evaluation of intralaminar fracture toughness of angle ply
laminate
Intralaminar fracture toughness values of [0°]30, [45°]30 and [90°]30 carbon/epoxy laminates are
theoretically evaluated based on the well-known MCCI method corresponding to
the fracture loads obtained by testing C(T) specimens. Comparison of fracture
toughness of angle ply laminate, which is associated with both mode I and mode
II, show a very good agreement with the theoretical prediction. A new empirical relationship is developed to obtain the
intralaminar fracture toughness of an angle ply laminate from the corresponding value of the 0° laminate. The new formula is used to compare
fracture toughness of angle ply laminates available in literature for glass
epoxy Scotch ply 1002 laminate and a reasonably good agreement is observed
between the test data and the predictions. As a percentage of total fracture
toughness value, toughness due to mode II is maximum of 15.5% when fibre
orientation is 45°.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 275-281
Studies on the upgrading of Indian
ilmenites to synthetic rutile
A process based on solid state
reduction of iron oxide content of ilmenite with carbon in presence of alkali
carbonate catalysts followed by removal of iron content of reduced ilmenite by
rusting in NH4Cl solution has been investigated for upgrading the
Indian ilmenites (Quilon and Orissa grades) to synthetic rutile. The process
variables such as the temperature of reduction, presence of catalytic agents
during reduction and rusting conditions etc. were examined to obtain an
upgraded product containing ³ 92% TiO2. Whereas Quilon ilmenite
could be reduced with carbon at 950°C for 2 h in presence of 5% Na2CO3,
the reduction of Orissa ilmenite required a pre-oxidation treatment in air at
850°C followed by reduction with carbon at 1025°C for 4 h in presence of 5% K2CO3
catalyst. The upgraded rutile product containing 92-93% TiO2 was
obtained when reduced ilmenite was rusted in 1% NH4Cl solution at a pH of 4.5 and a temperature of 65°C.
Indian Journal of Engineering &
Materials Sciences
Vol.
9, August 2002, pp. 282-288
Influence of certain metal
ions on thermoluminescence of A2O-CaF2-B2O3
glasses
Thermoluminescence study on X-ray irradiated A2O - CaF2 -
B2O3 (where A=Li, Na and K) glasses has been carried out
in the temperature range 303-600 K. All these glasses exhibit a single TL glow
peak between 480-500 K; the study is further extended after these glasses are
doped with different conventional activating or killing ions (viz., Sn2+,
Ag+, Ce3+, Bi3+ and Cu2+) in small
concentration (0.2%). All these ions are observed to inhibit the TL light
output in these glasses. The trap depth parameters with the observed TL glow
curves have been evaluated using Chens formulae. The probable mechanism
responsible for quenching of thermoluminescence emission by dopant ions in
these glasses has been suggested.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 289-294
Organic/inorganic hybrid fibre
reinforced thermoplastic composites and their rheological properties
Kevlar and glass fibres have been used to reinforce linear low density
polyethylene (LLDPE) and the composite sheets of 0.8 mm thickness have been
obtained by using a compression molding technique. Dynamic viscoelastic
properties of non-hybrid and hybrid composites of various compositions are
evaluated at 200°C. Dynamic viscosity (η΄), storage modulus (G΄) and loss modulus (G΄΄) have been determined at
different angular frequencies (ω). Dynamic viscosity η΄
increases with reinforcements. G΄
and G΄΄ increase with
angular frequency (w) and reinforcement. Replacement of glass fibre
by Kevlar at constant loading of fibres in LLDPE, increases the value of G΄, G΄΄ and η΄.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 295-298
Effect of temperature on slip and
deformation twinning in Cd single-crystals
The temperature effect on slip and deformation twinning has been
investigated in Cd single-crystals in tension in the temperature range from
room temperature to 500 K. The observations of traces on the surfaces of the
crystals show that there are twinning and slip at room temperature. Above 430 K
slip takes place on the limited slip plane. On the other hand, as the
temperature increases deformation twinning occurs on some new twinning plane
after considerable slip, although deformation twinning is a common low
temperature mode of plastic deformation. It is shown that the multiplicity of
twinning systems aids deformation by twin rather than by slip in Cd
single-crystals at high temperatures.
Indian Journal
of Engineering & Materials Sciences
Vol. 9, August 2002, pp. 299-306
Sliding wear behaviour
of woven glass fibre reinforced polyester composites
The dry sliding wear behaviour of woven glass fibre reinforced polyester composites has been studied by using pin-on-disc machine. The friction and wear experiments have been conducted on three different orientation of glass fibre with respect to sliding direction. The coefficient of friction and wear of the composites at various applied load and sliding speeds have been determined. The lowest coefficient of friction and wear values observed for the fibres oriented in 0°-90° direction and highest are for normal-longitudinal (N-L) orientation. The applied load further increase the friction and wear of the composites for all orientations. The friction and wear behaviour have been dominated by a number of mechanisms. The wear of the fibres has been dominated by the fibre fracture. The fibres have been fractured because of bending of fibre due to dragging by the steel disc in the sliding direction. The microscopic observations of the worn surfaces revealed and supported the involved mechanism.