Abstract: In this paper, the mechanism of stratified liquids’ mixing in a cylinder is investigated. It is focused on the effects of Rayleigh-Taylor Instability (RTI) and rotation of the cylinder on liquid interface mixing. For miscible liquids, Planar Laser Induced Fluorescence (PLIF) technique is applied to record the concentration field for one liquid. Intensity of Segregation (IOS) is used to describe the mixing status. For immiscible liquids, High Speed Camera is adopted to record the development of the interface. The experiment of RTI indicates that it plays a great role in the mixing process, and meanwhile the large-scale mixing is triggered, and subsequently the span of the stripes decreases, showing that the mesoscale mixing is coming into being. The rotation experiments show that the spin-down process has a great role in liquid mixing, during which the upper liquid falls down rapidly along the wall and crashes into the lower liquid. During this process, a lot of interface instabilities are excited. Liquids mix rapidly in the spin-down process. It can be concluded that no matter what ways have been adopted to speed up liquid mixing, the fundamental reason is the interface instabilities which increase the area of the interface between liquids and increase the relative velocity of the two liquids.
Abstract: The breakage of bonding between sand particles and their dislodgment from the borehole wall are among the main factors resulting in a borehole failure in poorly cemented granular formations. The grain debonding usually precedes the borehole failure and it can be considered as a sign that the onset of the borehole collapse is imminent. Detecting the bonding breakage point and introducing an appropriate failure criterion will play an important role in borehole stability analysis. To study the influence of different factors on the initiation of sand bonding breakage at the borehole wall, a series of laboratory tests was designed and conducted on poorly cemented sand samples. The total absorbed strain energy per volume of material up to the point of the observed particle debonding was computed. The results indicated that the particle bonding breakage point at the borehole wall was reached both before and after the peak strength of the thick-walled hollow cylinder specimens depending on the stress path and cement content. Three different cement contents and two borehole sizes were investigated to study the influence of the bonding strength and scale on the particle dislodgment. Test results showed that the stress path has a significant influence on the onset of the sand bonding breakage. It was shown that for various stress paths, there is a near linear relationship between the absorbed energy and the normal effective mean stress.
Abstract: The utilization of pneumatic muscles in the actuation of industrial systems is still in its early stages, hence studies on the constructive solutions which include an assessment of their functional performance with a focus on one of the most important characteristics-energy efficiency are required. A quality indicator that adequately reflects the energy efficiency of an actuator is the energy-to-mass ratio. This ratio is computed in the paper for various types and sizes of pneumatic muscles manufactured by Festo, and is subsequently compared to the similar ratios determined for two categories of pneumatic cylinders.
Abstract: This paper presents the evaluation of performance (BSFC and BTE), combustion (Pmax) and emission (CO, NOx, HC and smoke opacity) parameters of karanja biodiesel in a single cylinder, four stroke, direct injection diesel engine by considering significant engine input parameters (blending ratio, compression ratio and load torque). Multi-objective optimization of performance, combustion and emission parameters is also carried out in a karanja biodiesel engine using hybrid RSM-NSGA-II technique. The pareto optimum solutions are predicted by running the hybrid RSM-NSGA-II technique. Each pareto optimal solution is having its own importance. Confirmation tests are also conducted at randomly selected few pareto solutions to check the authenticity of the results.
Abstract: A two-dimensional numerical study for flow past a square cylinder in presence of flat plate both at upstream and downstream position is carried out using the single-relaxation-time lattice Boltzmann method for gap spacing 0.5 and 1. We select Reynolds numbers from 80 to 200. The wake structure mechanism within gap spacing and near wake region, vortex structures around and behind the main square cylinder in presence of flat plate are studied and compared with flow pattern around a single square cylinder. The results are obtained in form of vorticity contour, streamlines, power spectra analysis, time trace analysis of drag and lift coefficients. Four different types of flow patterns were observed in both configurations, named as (i) Quasi steady flow (QSF), (ii) steady flow (SF), (iii) shear layer reattachment (SLR), (iv) single bluff body (SBB). It is observed that upstream flat plate plays a vital role in significant drag reduction. On the other hand, rate of suppression of vortex shedding is high for downstream flat plate case at low Reynolds numbers. The reduction in mean drag force and root mean square value of drag force for upstream flat plate case are89.1% and 86.3% at (Re, g) = (80, 0.5d) and (120, 1d) and reduction for downstream flat plate case for mean drag force and root mean square value of drag force are 11.10% and 97.6% obtained at (180, 1d) and (180, 0.5d).
Abstract: In this research, the effects of the engine parameters like compression ratios and steam injection on igniting timing and emission characteristics have been investigated numerically. The in-cylinder temperature and pressure at four different compression ratios have been compared with numerical results, and they show a good agreement with the published data. Two different fuels have been used in this study: Isooctane (IC8H18), and ethanol (C2H5OH). The increasing of the compression ratio (CR) advances the ignition timing, decreases the burn duration and increases the temperature and the pressure. The injection of water vapor lower than 40% decreased the peak temperature and slowed the combustion rate which leads to a lower NOx emission.
Abstract: The paper describes conceptual design, control strategies, and partial simulation for a new fully autonomous lower limb wearable exoskeleton system for human motion enhancement that can support its weight and increase strength and endurance. Various problems still remain to be solved where the most important is the creation of a power and cost efficient system that will allow an exoskeleton to operate for extended period without batteries being frequently recharged. The designed exoskeleton is enabling to decouple the weight/mass carrying function of the system from the forward motion function which reduces the power and size of propulsion motors and thus the overall weight, cost of the system. The decoupling takes place by blocking the motion at knee joint by placing passive air cylinder across the joint. The cylinder is actuated when the knee angle has reached the minimum allowed value to bend. The value of the minimum bending angle depends on usual walk style of the subject. The mechanism of the exoskeleton features a seat to rest the subject’s body weight at the moment of blocking the knee joint motion. The mechanical structure of each leg has six degrees of freedom: four at the hip, one at the knee, and one at the ankle. Exoskeleton legs are attached to subject legs by using flexible cuffs. The operation of all actuators depends on the amount of pressure felt by the feet pressure sensors and knee angle sensor. The sensor readings depend on actual posture of the subject and can be classified in three distinct cases: subject stands on one leg, subject stands still on both legs and subject stands on both legs but transit its weight from one leg to other. This exoskeleton is power efficient because electrical motors are smaller in size and did not participate in supporting the weight like in all other existing exoskeleton designs.
Abstract: The defect mode of two-dimensional phononic crystals with Archimedean tilings was explored in the present study. Finite element method and supercell method were used to obtain dispersion relation of phononic crystals. The simulations of the acoustic wave propagation within phononic crystals are demonstrated. Around the cavity which is created by removing several cylinders in the perfect Archimedean tilings, whispering-gallery mode (WGM) can be observed. The effects of the cavity geometry on the WGM modes are investigated. The WGM modes with high Q-factor and high cavity pressure can be obtained by phononic crystals with Archimedean tilings.
Abstract: A recently developed one-equation turbulence model
has been successfully applied to simulate turbulent flows with
various complexities. The model, which is based on the
transformation of the k-ε closure, is wall-distance free and equipped
with lagging destruction/dissipation terms. Test cases included shockboundary-
layer interaction flows over the NACA 0012 airfoil, an
axisymmetric bump, and the ONERA M6 wing. The capability of the
model to operate in a Scale Resolved Simulation (SRS) mode is
demonstrated through the simulation of a massive flow separation
over a circular cylinder at Re= 1.2 x106. An assessment of the results
against available experiments Menter (k-ε)1Eq and the Spalart-
Allmaras model that belongs to the single equation closure family is
made.
Abstract: Modeling of hydrogen fueled engine (H2ICE) injection system is a very important tool that can be used for explaining or predicting the effect of advanced injection strategies on combustion and emissions. In this paper, a common rail injection system (CRIS) is proposed for 4-strokes 4-cylinders hydrogen fueled engine with port injection feeding system (PIH2ICE). For this system, a numerical one-dimensional gas dynamic model is developed considering single injection event for each injector per a cycle. One-dimensional flow equations in conservation form are used to simulate wave propagation phenomenon throughout the CR (accumulator). Using this model, the effect of common rail on the injection system characteristics is clarified. These characteristics include: rail pressure, sound velocity, rail mass flow rate, injected mass flow rate and pressure drop across injectors. The interaction effects of operational conditions (engine speed and rail pressure) and geometrical features (injector hole diameter) are illustrated; and the required compromised solutions are highlighted. The CRIS is shown to be a promising enhancement for PIH2ICE.
Abstract: The present study focused on carrying out the creep analysis in an isotropic thick-walled composite cylindrical pressure vessel composed of aluminum matrix reinforced with silicon-carbide in particulate form. The creep behavior of the composite material has been described by the threshold stress based creep law. The values of stress exponent appearing in the creep law were selected as 3, 5 and 8. The constitutive equations were developed using well known von-Mises yield criteria. Models were developed to find out the distributions of creep stress and strain rate in thick-walled composite cylindrical pressure vessels under internal pressure. In order to obtain the stress distributions in the cylinder, the equilibrium equation of the continuum mechanics and the constitutive equations are solved together. It was observed that the radial stress, tangential stress and axial stress increases along with the radial distance. The cross-over was also obtained almost at the middle region of cylindrical vessel for tangential and axial stress for different values of stress exponent. The strain rates were also decreasing in nature along the entire radius.
Abstract: The complexity of scavenging by ports and its impact on engine efficiency create the need to understand and to model it as realistically as possible. However, there are few empirical scavenging models and these are highly specialized. In a design optimization process, they appear very restricted and their field of use is limited. This paper presents a comparison of two methods to establish and reduce a model of the scavenging process in 2-stroke diesel engines. To solve the lack of scavenging models, a CFD model has been developed and is used as the referent case. However, its large size requires a reduction. Two techniques have been tested depending on their fields of application: The NTF method and neural networks. They both appear highly appropriate drastically reducing the model’s size (over 90% reduction) with a low relative error rate (under 10%). Furthermore, each method produces a reduced model which can be used in distinct specialized fields of application: the distribution of a quantity (mass fraction for example) in the cylinder at each time step (pseudo-dynamic model) or the qualification of scavenging at the end of the process (pseudo-static model).
Abstract: Centrifugal-casting machine is used in manufacturing
special machine components like multi-layer journal bearing used in
all internal combustion engine, steam, gas turbine and air craft turboengine
where isotropic properties and high precisions are desired.
Moreover, this machine can be used in manufacturing thin wall hightech
machine components like cylinder liners and piston rings of IC
engine and other machine parts like sleeves, and bushes. Heavy-duty
machine component like railway wheel can also be prepared by
centrifugal casting. A lot of technological developments are required
in casting process for production of good casted machine body and
machine parts. Usually defects like blowholes, surface roughness,
chilled surface etc. are found in sand casted machine parts. But these
can be removed by centrifugal casting machine using rotating
metallic die. Moreover, die rotation, its temperature control, and good
pouring practice can contribute to the quality of casting because of
the fact that the soundness of a casting in large part depends upon
how the metal enters into the mold or dies and solidifies. Poor
pouring practice leads to variety of casting defects such as
temperature loss, low quality casting, excessive turbulence, over
pouring etc. Besides these, handling of molten metal is very
unsecured and dangerous for the workers. In order to get rid of all
these problems, the need of an automatic pouring device arises. In
this research work, a robot assisted pouring device and a centrifugal
casting machine are designed, developed constructed and tested
experimentally which are found to work satisfactorily. The robot
assisted pouring device is further modified and developed for using it
in actual metal casting process. Lot of settings and tests are required
to control the system and ultimately it can be used in automation of
centrifugal casting machine to produce high-tech machine parts with
desired precision.
Abstract: Biodiesel is widely investigated to solve the twin
problem of depletion of fossil fuel and environmental degradation.
The main objective of the present work is to compare performance,
emissions, and combustion characteristics of biodiesel derived from
cotton seed oil in a diesel engine with the baseline results of
petrodiesel fuel. Tests have been conducted on a single cylinder, four
stroke CIDI diesel engine with a speed of 1500 rpm and a fixed
compression ratio of 17.5 at different load conditions. The
performance parameters evaluated include brake thermal efficiency,
brake specific fuel consumption, brake power, indicated mean
effective pressure, mechanical efficiency, and exhaust gas
temperature. Regarding combustion study, cylinder pressure, rate of
pressure rise, net heat release rate, cumulative heat release, mean gas
temperature, mass fraction burned, and fuel line pressure were
evaluated. The emission parameters such as carbon monoxide, carbon
dioxide, un-burnt hydrocarbon, oxides of nitrogen, and smoke
opacity were also measured by a smoke meter and an exhaust gas
analyzer and compared with baseline results. The brake thermal
efficiency of cotton seed oil methyl ester (CSOME) was lower than
that of petrodiesel and brake specific fuel consumption was found to
be higher. However, biodiesel resulted in the reduction of carbon
dioxide, un-burnt hydrocarbon, and smoke opacity at the expense of
nitrogen oxides. Carbon monoxide emissions for biodiesel was higher
at maximum output power. It has been found that the combustion
characteristics of cotton seed oil methyl ester closely followed those
of standard petrodiesel. The experimental results suggested that
biodiesel derived from cotton seed oil could be used as a good
substitute to petrodiesel fuel in a conventional diesel without any
modification.
Abstract: This study investigated the effects of thermal
treatment on Tualang honey sample in terms of honey colour and
heat-induced small metabolites. The heating process was carried out
in a temperature controlled water batch at 90oC for 4 hours. The
honey samples were put in cylinder tubes with the dimension of 1 cm
diameter and 10 cm length for homogenous heat transfer. The results
found that the thermal treatment produced not only
hydroxylmethylfurfural, but also other harmful substances such as
phthalic anhydride and radiolytic byproducts. The degradation of
honey protein was due to the detection of free amino acids such as
cysteine and phenylalanine in heat-treated honey samples. Sugar
dehydration was also occurred because fragmented di-galactose was
identified based on the presence of characteristic ions in the mass
fragmentation pattern. The honey colour was found getting darker as
the heating duration was increased up to 4 hours. Approximately, 60
mm PFund of increment was noticed for the honey colour with the
colour change rate of 14.8 mm PFund per hour. Based on the
principal component analysis, the score plot clearly shows that the
chemical profile of Tualang honey was significantly altered after 2
hours of heating at 90oC.
Abstract: Rotary entrainment is a phenomenon in which the
interface of two immiscible fluids are subjected to external flux by
means of rotation. Present work reports the experimental study on
rotary motion of a horizontal cylinder between the interface of air and
water to observe the penetration of gas inside the liquid. Experiments
have been performed to establish entrainment of air mass in water
alongside the cylindrical surface. The movement of tracer and seeded
particles has been tracked to calculate the speed and path of the
entrained air inside water. Simplified particle image velocimetry
technique has been used to trace the movement of particles/tracers at
the moment they are injected inside the entrainment zone and
suspended beads have been used to replicate the particle movement
with respect to time in order to determine the flow dynamics of the
fluid along the cylinder. Present paper establishes a thorough experimental analysis of the
rotary entrainment phenomenon between air and water keeping in
interest the extent to which we can intermix the two and also to study
its entrainment trajectories.
Abstract: Unsteady flow and heat transfer from a circular
cylinder in cross-flow is studied numerically. The governing
equations are solved by using finite volume method. Reynolds
number varies in range of 50 to 200; in this range flow is considered
to be laminar and unsteady. Al2O3 nanoparticle with volume fraction
in range of 5% to 20% is added to pure water. Effects of adding
nanoparticle to pure water on lift and drag coefficient and Nusselt
number is presented. Addition of Al2O3 has inconsiderable effect on
the value of drags and lift coefficient. However, it has significant
effect on heat transfer; results show that heat transfer of Al2O3
nanofluid is about 9% to 36% higher than pure water.
Abstract: In this paper, the 2-D unsteady viscous flow around
two cam shaped cylinders in tandem arrangement is numerically
simulated in order to study the characteristics of the flow in turbulent
regimes. The investigation covers the effects of high subcritical and
supercritical Reynolds numbers and L/D ratio on total drag
coefficient. The equivalent diameter of cylinders is 27.6 mm The
space between center to center of two cam shaped cylinders is define
as longitudinal pitch ratio and it varies in range of 1.5< L/D
Abstract: A solution methodology without using integral
transformation is proposed to develop analytical solutions for
transient heat conduction in nonuniform hollow cylinders with
time-dependent boundary condition at the outer surface. It is shown
that if the thermal conductivity and the specific heat of the medium
are in arbitrary polynomial function forms, the closed solutions of the
system can be developed. The influence of physical properties on the
temperature distribution of the system is studied. A numerical
example is given to illustrate the efficiency and the accuracy of the
solution methodology.
Abstract: Particle size distribution, the most important
characteristics of aerosols, is obtained through electrical
characterization techniques. The dynamics of charged nanoparticles
under the influence of electric field in Electrical Mobility
Spectrometer (EMS) reveals the size distribution of these particles.
The accuracy of this measurement is influenced by flow conditions,
geometry, electric field and particle charging process, therefore by
the transfer function (transfer matrix) of the instrument. In this work,
a wire-cylinder corona charger was designed and the combined fielddiffusion
charging process of injected poly-disperse aerosol particles
was numerically simulated as a prerequisite for the study of a
multichannel EMS. The result, a cloud of particles with no uniform
charge distribution, was introduced to the EMS. The flow pattern and
electric field in the EMS were simulated using Computational Fluid
Dynamics (CFD) to obtain particle trajectories in the device and
therefore to calculate the reported signal by each electrometer.
According to the output signals (resulted from bombardment of
particles and transferring their charges as currents), we proposed a
modification to the size of detecting rings (which are connected to
electrometers) in order to evaluate particle size distributions more
accurately. Based on the capability of the system to transfer
information contents about size distribution of the injected particles,
we proposed a benchmark for the assessment of optimality of the
design. This method applies the concept of Von Neumann entropy
and borrows the definition of entropy from information theory
(Shannon entropy) to measure optimality. Entropy, according to the
Shannon entropy, is the ''average amount of information contained in
an event, sample or character extracted from a data stream''.
Evaluating the responses (signals) which were obtained via various
configurations of detecting rings, the best configuration which gave
the best predictions about the size distributions of injected particles,
was the modified configuration. It was also the one that had the
maximum amount of entropy. A reasonable consistency was also
observed between the accuracy of the predictions and the entropy
content of each configuration. In this method, entropy is extracted
from the transfer matrix of the instrument for each configuration.
Ultimately, various clouds of particles were introduced to the
simulations and predicted size distributions were compared to the
exact size distributions.