Abstract: Thermoacoustic instabilities in combustors have
remained a topic of investigation for over a few decades due to the
challenges it posses to the operation of low emission gas turbines.
For combustors burning liquid fuel, understanding the cause-andeffect
relationship between spray combustion dynamics and
thermoacoustic oscillations is imperative for the successful
development of any control methodology for its mitigation. The
paper presents some very unique operating characteristics of a
kerosene-fueled diffusion type combustor undergoing limit-cycle
oscillations. Combustor stability limits were mapped using three
different-sized injectors. The results show that combustor instability
depends on the characteristics of the fuel spray. A simple analytic
analysis is also reported in support of a plausible explanation for the
unique combustor behavior. The study indicates that high amplitude
acoustic pressure in the combustor may cause secondary breakdown
of fuel droplets resulting in premixed pre-vaporized type burning of
the diffusion type combustor.
Abstract: In this work, we suggested a new approach for the
control of a mobile robot capable of being a building block of an
intelligent agent. This approach includes obstacle avoidance and goal
tracking implemented as two different sliding mode controllers. A
geometry based behavior arbitration is proposed for fusing the two
outputs. Proposed structure is tested on simulations and real robot.
Results have confirmed the high performance of the method.
Abstract: One promising way to achieve low temperature
combustion regime is the use of a large amount of cooled EGR. In
this paper, the effect of injection timing on low temperature
combustion process and emissions were investigated via three
dimensional computational fluid dynamics (CFD) procedures in a DI
diesel engine using high EGR rates. The results show when
increasing EGR from low levels to levels corresponding to reduced
temperature combustion, soot emission after first increasing, is
decreased beyond 40% EGR and get the lowest value at 58% EGR
rate. Soot and NOx emissions are simultaneously decreased at
advanced injection timing before 20.5 ºCA BTDC in conjunction
with 58% cooled EGR rate in compared to baseline case.
Abstract: Collision is considered as a time-depended nonlinear
dynamic phenomenon. The majority of researchers have focused on
deriving the resultant damage of the ship collisions via analytical,
experimental, and finite element methods.In this paper, first, the
force-penetration curve of a head collision on a container ship with
rigid barrier based on Yang and Pedersen-s methods for internal
mechanic section is studied. Next, the obtained results from different
analytical methods are compared with each others. Then, through a
simulation of the container ship collision in Ansys Ls-Dyna, results
from finite element approach are compared with analytical methods
and the source of errors is discussed. Finally, the effects of
parameters such as velocity, and angle of collision on the forcepenetration
curve are investigated.
Abstract: Medical compression bandages are widely used in the
treatment of chronic venous disorder. In order to design effective
compression bandages, researchers have attempted to describe the
interface pressure applied by multi-layer bandages using mathematical
models. This paper reports on the work carried out to
compare and validate the mathematical models used to describe the
interface pressure applied by multi-layer bandages. Both analytical
and experimental results showed that using simple multiplication
of a number of bandage layers with the pressure applied by one
layer of bandage or ignoring the increase in the limb radius due to
former layers of bandage will result in overestimating the pressure.
Experimental results showed that the mathematical models, which
take into consideration the increase in the limb radius due to former
bandage layers, are more accurate than the one which does not.
Abstract: Skip cycle is a working strategy for spark ignition
engines, which allows changing the effective stroke of an engine
through skipping some of the four stroke cycles. This study proposes
a new mechanism to achieve the desired skip-cycle strategy for
internal combustion engines. The air and fuel leakage, which occurs
through the gas exchange, negatively affects the efficiency of the
engine at high speeds and loads. An absolute sealing is assured by
direct use of poppet valves, which are kept in fully closed position
during the skipped mode. All the components of the mechanism were
designed according to the real dimensions of the Anadolu Motor's
gasoline engine and modeled in 3D by means of CAD software. As
the mechanism operates in two modes, two dynamically equivalent
models are established to obtain the force and strength analysis for
critical components.
Abstract: In this study we focus on improvement performance
of a cue based Motor Imagery Brain Computer Interface (BCI). For
this purpose, data fusion approach is used on results of different
classifiers to make the best decision. At first step Distinction
Sensitive Learning Vector Quantization method is used as a feature
selection method to determine most informative frequencies in
recorded signals and its performance is evaluated by frequency
search method. Then informative features are extracted by packet
wavelet transform. In next step 5 different types of classification
methods are applied. The methodologies are tested on BCI
Competition II dataset III, the best obtained accuracy is 85% and the
best kappa value is 0.8. At final step ordered weighted averaging
(OWA) method is used to provide a proper aggregation classifiers
outputs. Using OWA enhanced system accuracy to 95% and kappa
value to 0.9. Applying OWA just uses 50 milliseconds for
performing calculation.
Abstract: The objective of this study is to determine the thermal comfort among worker at Malaysian automotive industry. One critical manual assembly workstation had been chosen as a subject for the study. The human subjects for the study constitute operators at Body Assembly Station of the factory. The environment examined was the Relative Humidity (%), Airflow (m/s), Air Temperature (°C) and Radiant Temperature (°C) of the surrounding workstation area. The environmental factors were measured using Babuc apparatus, which is capable to measure simultaneously those mentioned environmental factors. The time series data of fluctuating level of factors were plotted to identify the significant changes of factors. Then thermal comfort of the workers were assessed by using ISO Standard 7730 Thermal sensation scale by using Predicted Mean Vote (PMV). Further Predicted percentage dissatisfied (PPD) is used to estimate the thermal comfort satisfaction of the occupant. Finally the PPD versus PMV were plotted to present the thermal comfort scenario of workers involved in related workstation. The result of PMV at the related industry is between 1.8 and 2.3, where PPD at that building is between 60% to 84%. The survey result indicated that the temperature more influenced comfort to the occupants
Abstract: This paper describes the design and modeling
procedure of a novel 5-phase segment type switched reluctance motor
(ST-SRM) under simultaneous two-phase (bipolar) excitation of
windings. The rotor cores of ST-SRM are embedded in an aluminum
block as well as to improve the performance characteristics. The
magnetic circuit of the produced ST-SRM is constructed so that the
magnetic flux paths are short and exclusive to each phase, thereby
minimizing the commutation switching and eddy current losses in the
laminations. The design and simulation principles presented apply
primarily to conventional SRM and ST-SRM. It is proved that the
novel 5-phase switched reluctance motor under two-phase excitation
is superior among the criteria used in comparison. The purposed
model is particularly well suited for high torque and weight
constrained applications such as automobiles, aerospace and military
applications.
Abstract: This paper presents and discusses the numerical simulations of transient laminar natural convection cooling of high Prandtl number fluids in cubical cavities, in which the six walls of the cavity are subjected to a step change in temperature. The effect of the fluid Prandtl number on the heat transfer coefficient is studied for three different fluids (Golden Syrup, Glycerin and Glycerin-water solution 50%). The simulations are performed at two different Rayleigh numbers (5·106 and 5·107) and six different Prandtl numbers (3 · 105 ≥Pr≥ 50). Heat conduction through the cavity glass walls is also considered. The propsed correlations of the averaged heat transfer coefficient (N u) showed that it is dependant on the initial Ra and almost independent on P r. The instantaneous flow patterns, temperature contours and time evolution of volume averaged temperature and heat transfer coefficient are presented and analyzed.
Abstract: In countries with hot climates, air-conditioning forms
a large proportion of annual peak electrical demand, requiring
expansion of power plants to meet the peak demand, which goes
unused most of the time. Use of well-designed cool storage can offset
the peak demand to a large extent. In this study, an air conditioning
system with naturally stratified storage tank was designed,
constructed and tested. A new type of diffuser was designed and used
in this study. Factors that influence the performance of chilled water
storage tanks were investigated. The results indicated that stratified
storage tank consistently stratified well without any physical barrier.
Investigation also showed that storage efficiency decreased with
increasing flow rate due to increased mixing of warm and chilled
water. Diffuser design and layout primarily affected the mixing near
the inlet diffuser and the extent of this mixing had primary influence
on the shape of the thermocline. The heat conduction through tank
walls and through the thermocline caused widening of mixed volume.
Thermal efficiency of stratified storage tanks was as high as 90
percent, which indicates that stratified tanks can effectively be used
as a load management technique.
Abstract: Axial Flux Permanent Magnet (AFPM) Machines require effective cooling due to their high power density. The detrimental effects of overheating such as degradation of the insulation materials, magnets demagnetization, and increase of Joule losses are well known. This paper describes the CFD simulations performed on a test rig model of an air cooled Axial Flux Permanent Magnet (AFPM) generator built at Durham University to identify the temperatures and heat transfer coefficient on the stator. The Reynolds Averaged Navier-Stokes and the Energy equations are solved and the flow pattern and heat transfer developing inside the machine are described. The Nusselt number on the stator surfaces has been found. The dependency of the heat transfer on the flow field is described temperature field obtained. Tests on an experimental are undergoing in order to validate the CFD results.
Abstract: A measurement apparatus is designed and fabricated to
measure the effective thermal conductivity (keff) of a VIP (vacuum
insulation panel) core specimen under various vacuum states and
external loads. The apparatus consists of part for measuring keff, and
parts for controlling external load and vacuum condition. Uncertainty
of the apparatus is validated by measuring the standard reference
material and comparing with commercial devices with VIP samples.
Assessed uncertainty is maximum 2.5 % in case of the standard
reference material, 10 % in case of VIP samples. Using the apparatus,
keff of glass paper under various vacuum levels is examined.
Abstract: Nanofluids are novel fluids that are going to have an
important role in future industrial thermal device designs. Studies are
being predominantly conducted on the mechanism of these heat
transfers. The key to this attraction is in the increase in thermal
conductivity brought about by the Nanofluids compared with the
base fluid. Different models have been proposed for calculation of
effective thermal conduction that has been gradually modified. In this
investigation effect of nanolayer structure and Brownian motion of
particles are studied and a new modified thermal conductivity model
is proposed. Temperature, concentration, nanolayer thickness and
particle size are taken as variables and their effect are studied
simultaneously on the thermal conductivity of the fluids, showing the
concentration of the nanoparticles to affect the nanolayer thickness
which also affects the Brownian motion.
Abstract: This paper presents an experimental investigation using Acoustic Emission (AE) technology to monitor sand transportation in multiphase flow. The investigations were undertaken on three-phase (air-water-sand) flow in a horizontal pipe where the superficial gas velocity (VSG) had a range of between 0.2msˉ¹ to 2.0msˉ¹ and superficial liquid velocity (VSL) had a range of between 0.2msˉ¹ to 1.0msˉ¹. The experimental findings clearly show a correlation exists between AE energy levels, sand concentration, superficial gas velocity (VSG), and superficial liquid velocity (VSL).
Abstract: Vibration characteristics of subcooled flow boiling on
thin and long structures such as a heating rod were recently
investigated by the author. The results show that the intensity of the
subcooled boiling-induced vibration (SBIV) was influenced strongly
by the conditions of the subcooling temperature, linear power density
and flow velocity. Implosive bubble formation and collapse are the
main nature of subcooled boiling, and their behaviors are the only
sources to originate from SBIV. Therefore, in order to explain the
phenomenon of SBIV, it is essential to obtain reliable information
about bubble behavior in subcooled boiling conditions. This was
investigated at different conditions of coolant subcooling
temperatures of 25 to 75°C, coolant flow velocities of 0.16 to
0.53m/s, and linear power densities of 100 to 600 W/cm. High speed
photography at 13,500 frames per second was performed at these
conditions. The results show that even at the highest subcooling
condition, the absolute majority of bubbles collapse very close to the
surface after detaching from the heating surface. Based on these
observations, a simple model of surface tension and momentum
change is introduced to offer a rough quantitative estimate of the
force exerted on the heating surface during the bubble ebullition. The
formation of a typical bubble in subcooled boiling is predicted to
exert an excitation force in the order of 10-4 N.
Abstract: The aim of this paper is to compare the effectiveness and electrochemical behavior of typical oilfield corrosion inhibitors with previous oilfield corrosion inhibitors under the same electrochemical techniques to control preferential weld corrosion of X65 pipeline steel in artificial seawater saturated with carbon dioxide at a pressure of one bar. A secondary aim is to investigate the conditions under which current reversal takes place. A flow channel apparatus was used in the laboratory to simulate the actual condition that occurs in marine pipelines. Different samples from the parent metal, the weld metal and the heat affected zone in the pipeline steel were galvanically coupled. The galvanic currents flowing between the weld regions were recorded using zero-resistance ammeters and tested under static and flowing conditions in both inhibited and uninhibited media. The results show that a current reversal took place when 30ppm of both green oilfield inhibitors were present, resulting in accelerated weld corrosion.
Abstract: In this paper, an automated system is presented for
identification and separation of plastic resins based on near infrared
(NIR) reflectance spectroscopy. For identification and separation
among resins, a "Two-Filter" identification method is proposed that
is capable to distinguish among polyethylene terephthalate (PET),
high density polyethylene (HDPE), polyvinyl chloride (PVC),
polypropylene (PP) and polystyrene (PS). Through surveying effects
of parameters such as surface contamination, sample thickness, label
and cap existence, it was obvious that the "Two-Filter" method has a
high efficiency in identification of resins. It is shown that accurate
identification and separation of five major resins can be obtained
through calculating the relative reflectance at two wavelengths in the
NIR region.
Abstract: This paper describes reactive neural control used to
generate phototaxis and obstacle avoidance behavior of walking
machines. It utilizes discrete-time neurodynamics and consists of
two main neural modules: neural preprocessing and modular neural
control. The neural preprocessing network acts as a sensory fusion
unit. It filters sensory noise and shapes sensory data to drive the
corresponding reactive behavior. On the other hand, modular neural
control based on a central pattern generator is applied for locomotion
of walking machines. It coordinates leg movements and can generate
omnidirectional walking. As a result, through a sensorimotor loop this
reactive neural controller enables the machines to explore a dynamic
environment by avoiding obstacles, turn toward a light source, and
then stop near to it.
Abstract: Hydrocyclones flow field study is conducted by performing a parametric study. Effect of cone angle on deoiling hydrocyclones flow behaviour is studied in this research. Flow field of hydrocyclone is obtained by three-dimensional simulations with OpenFOAM code. Because of anisotropic behaviour of flow inside hydrocyclones LES is a suitable method to predict the flow field since it resolves large scales and model isotropic small scales. Large eddy simulation is used to predict the flow behavior of three different cone angles. Differences in tangential velocity and pressure distribution are reported in some figures.