Abstract: The design of high performance combustion chambers for turbojet engines is considered as one of the most challenges that face gas turbine designers, since the design approach depends on empirical correlations of data derived from the previous design experiences. The objective of this paper is to design a combustion chamber that suits the requirements of a micro-turbojet engine with 400 N output thrust and operates with kerosene as fuel. In this paper, only preliminary calculations related to the annular type of combustion chamber are explained in details. These calculations will cover the evaluation of reference quantities, calculation of required dimensions, calculation of air distribution and pressure drop, estimation of number and diameters for air admission holes, as well as aerodynamic considerations. The design process is then accompanied by analytical procedure using commercial CFD ANALYSIS tool; ANSYS 16 CFX software. After conducting CFD analysis, the design process will be then iterated in order to gain satisfactory results. It should be noted that the design of the fuel preparation and installation systems is beyond the scope of this work, and it will be discussed separately in another work.
Abstract: Cardiovascular diseases (CVDs) are the main cause of death globally. Most CVDs can be prevented by avoiding habitual risk factors. Separate from the habitual risk factors, there are some inherent factors in each individual that can increase the risk potential of CVDs. Vessel shapes and geometry are influential factors, having great impact on the blood flow and the hemodynamic behavior of the vessels. In the present study, the influence of bifurcation angle on blood flow characteristics is studied. In order to approach this topic, by simplifying the details of the bifurcation, three models with angles 30°, 45°, and 60° were created, then by using CFD analysis, the response of these models for stable flow and pulsatile flow was studied. In the conducted simulation in order to eliminate the influence of other geometrical factors, only the angle of the bifurcation was changed and other parameters remained constant during the research. Simulations are conducted under dynamic and stable condition. In the stable flow simulation, a steady velocity of 0.17 m/s at the inlet plug was maintained and in dynamic simulations, a typical LAD flow waveform is implemented. The results show that the bifurcation angle has an influence on the maximum speed of the flow. In the stable flow condition, increasing the angle lead to decrease the maximum flow velocity. In the dynamic flow simulations, increasing the bifurcation angle lead to an increase in the maximum velocity. Since blood flow has pulsatile characteristics, using a uniform velocity during the simulations can lead to a discrepancy between the actual results and the calculated results.
Abstract: Emergency Core Coolant Bypass (ECC Bypass) has been regarded as an important phenomenon to peak cladding temperature of large-break loss-of-coolant-accidents (LBLOCA) in nuclear power plants (NPP). A modeling scheme to address the ECC Bypass phenomena and the calculation of LBLOCA using that scheme are discussed in the present paper. A hydraulic form loss coefficient (HFLC) from the reactor vessel downcomer to the broken cold leg is predicted by the computational fluid dynamics (CFD) code with a variation of the void fraction incoming from the downcomer. The maximum, mean, and minimum values of FLC are derived from the CFD results and are incorporated into the LBLOCA calculation using a system thermal-hydraulic code, MARS-KS. As a relevant parameter addressing the ECC Bypass phenomena, the FLC to the break and its range are proposed.
Abstract: The aim of this study is to estimate the effect of blood flow through the coronary artery in human heart so as to assess the coronary artery disease.Velocity, wall shear stress (WSS), strain rate and wall pressure distribution are some of the important hemodynamic parameters that are non-invasively assessed with computational fluid dynamics (CFD). These parameters are used to identify the mechanical factors responsible for the plaque progression and/or rupture in left coronary arteries (LCA) in coronary arteries.The initial step for CFD simulations was the construction of a geometrical model of the LCA. Patient specific artery model is constructed using computed tomography (CT) scan data with the help of MIMICS Research 19.0. For CFD analysis ANSYS FLUENT-14.5 is used.Hemodynamic parameters were quantified and flow patterns were visualized both in the absence and presence of coronary plaques. The wall pressure continuously decreased towards distal segments and showed pressure drops in stenotic segments. Areas of high WSS and high flow velocities were found adjacent to plaques deposition.
Abstract: A butterfly valve is a quarter turn valve which is used to control the flow of a fluid through a section of pipe. Generally, butterfly valve is used in wide range of applications such as water distribution, sewage, oil and gas plants. In particular, butterfly valve with larger diameter finds its immense applications in hydro power plants to control the fluid flow. In-lieu with the constraints in cost and size to run laboratory setup, analysis of large diameter values will be mostly studied by computational method which is the best and inexpensive solution. For fluid and structural analysis, CFD and FEM software is used to perform large scale valve analyses, respectively. In order to perform above analysis in butterfly valve, the CAD model has to recreate and perform mesh in conventional software’s for various dimensions of valve. Therefore, its limitation is time consuming process. In-order to overcome that issue, python code was created to outcome complete pre-processing setup automatically in Salome software. Applying dimensions of the model clearly in the python code makes the running time comparatively lower and easier way to perform analysis of the valve. Hence, in this paper, an attempt was made to study the fluid-structure interaction (FSI) of butterfly valves by varying the valve angles and dimensions using python code in pre-processing software, and results are produced.
Abstract: Environmental performance of artisanal brick manufacture was studied by Lifecycle Assessment (LCA) methodology and Computational Fluid Dynamics (CFD) analysis in Mexico. The main objective of this paper is to evaluate the environmental impact during artisanal brick manufacture. LCA cradle-to-gate approach was complemented with CFD analysis to carry out an Environmental Impact Assessment (EIA). The lifecycle includes the stages of extraction, baking and transportation to the gate. The functional unit of this study was the production of a single brick in Chihuahua, Mexico and the impact categories studied were carcinogens, respiratory organics and inorganics, climate change radiation, ozone layer depletion, ecotoxicity, acidification/ eutrophication, land use, mineral use and fossil fuels. Laboratory techniques for fuel characterization, gas measurements in situ, and AP42 emission factors were employed in order to calculate gas emissions for inventory data. The results revealed that the categories with greater impacts are ecotoxicity and carcinogens. The CFD analysis is helpful in predicting the thermal diffusion and contaminants from a defined source. LCA-CFD synergy complemented the EIA and allowed us to identify the problem of thermal efficiency within the system.
Abstract: Mineral product, waste concrete (fine aggregates),
waste in the optical field, industry, and construction employ separators
to separate solids and classify them according to their size. Various
sorting machines are used in the industrial field such as those operating
under electrical properties, centrifugal force, wind power, vibration,
and magnetic force. Study on separators has been carried out to
contribute to the environmental industry. In this study, we perform
CFD analysis for understanding the basic mechanism of the separation
of waste concrete (fine aggregate) particles from air with a machine
built with a rotor with blades. In CFD, we first performed
two-dimensional particle tracking for various particle sizes for the
model with 1 degree, 1.5 degree, and 2 degree angle between each
blade to verify the boundary conditions and the method of rotating
domain method to be used in 3D. Then we developed 3D numerical
model with ANSYS CFX to calculate the air flow and track the
particles. We judged the capability of particle separation for given size
by counting the number of particles escaping from the domain toward
the exit among 10 particles issued at the inlet. We confirm that
particles experience stagnant behavior near the exit of the rotating
blades where the centrifugal force acting on the particles is in balance
with the air drag force. It was also found that the minimum particle
size that can be separated by the machine with the rotor is determined
by its capability to stay at the outlet of the rotor channels.
Abstract: This research presents the design and analysis of solar
air-conditioning systems particularly solar chimney which is a
passive strategy for natural ventilation, and demonstrates the
structures of these systems’ using Computational Fluid Dynamic
(CFD) and finally compares the results with several examples, which
have been studied experimentally and carried out previously. In order
to improve the performance of solar chimney system, highly efficient
sub-system components are considered for the design. The general
purpose of the research is to understand how efficiently solar
chimney systems generate cooling, and is to improve the efficient of
such systems for integration with existing and future domestic
buildings.
Abstract: Different designs of attenuator systems have been
studied in this research; new analysis have been done on existed
designs considering fibers effect on air flow; it was comprehended
that, at fibers presence, there is an air flow which agglomerates fibers
as a negative effect. So some new representations have been designed
and CFD analysis has been done on them. Afterwards, one of these
representations selected as the most optimum and effective design
which is brought in this paper.
Abstract: Nanofibers are effective materials which have
frequently been investigated to produce high quality air filters. As an
environmental approach our aim is to achieve nanofibers by melting.
In spun-bond systems extruder, spin-pump, nozzle package and
attenuator are used. Molten polymer which flows from extruder is
made steady by spin-pump. Regular melt passes through nozzle holes
and forms fibers under high pressure. The fibers pulled from nozzle
are shrunk to micron size by an attenuator; after solidification, they
are collected on a conveyor. In this research different designs of
attenuator system have been studied; and also CFD analysis has been
done on these different designs. Afterwards, one of these designs
tested and finally some optimizations have been done to reduce
pressure loss and increase air velocity.
Abstract: A computational fluid dynamics (CFD) model is
developed for rechargeable non-aqueous electrolyte lithium-air
batteries with a partial opening for oxygen supply to the cathode.
Multi-phase transport phenomena occurred in the battery are
considered, including dissolved lithium ions and oxygen gas in the
liquid electrolyte, solid-phase electron transfer in the porous
functional materials and liquid-phase charge transport in the
electrolyte. These transport processes are coupled with the
electrochemical reactions at the active surfaces, and effects of
discharge reaction-generated solid Li2O2 on the transport properties
and the electrochemical reaction rate are evaluated and implemented
in the model. The predicted results are discussed and analyzed in terms
of the spatial and transient distribution of various parameters, such as
local oxygen concentration, reaction rate, variable solid Li2O2 volume
fraction and porosity, as well as the effective diffusion coefficients. It
is found that the effect of the solid Li2O2 product deposited at the solid
active surfaces is significant on the transport phenomena and the
overall battery performance.
Abstract: This paper presents the findings from a numerical simulation of the flow in 37-rod fuel assembly models spaced by a double-wire trapezoidal wrapping as applied to the BREST-OD-300 experimental nuclear reactor. Data on a high static pressure distribution within the models, and equations for determining the fuel bundle flow friction factors have been obtained. Recommendations are provided on using the closing turbulence models available in the ANSYS Fluent. A comparative analysis has been performed against the existing empirical equations for determining the flow friction factors. The calculated and experimental data fit has been shown.
An analysis into the experimental data and results of the numerical simulation of the BREST-OD-300 fuel rod assembly hydrodynamic performance are presented.
Abstract: This work aims to present a numerical analysis of the natural gas which flows through a high-pressure pipeline and an orifice plate, through the use of CFD methods. The paper contains CFD calculations for the flow of natural gas in a pipe with different geometry used for the orifice plates. One of them has a standard geometry and a shape without any deformation and the other is deformed by the action of the pressure differential. It shows the behavior of natural gas in a pipeline using the velocity profiles and pressure fields of the gas in both models with their differences. The entire research is based on the elimination of any inaccuracy which should appear in the flow of the natural gas measured in the high-pressure pipelines of the gas industry and which is currently not given in the relevant standard.
Abstract: High-velocity oxygen fuel (HVOF) thermal spraying
uses a combustion process to heat the gas flow and coating material.
A computational fluid dynamics (CFD) model has been developed to
predict gas dynamic behavior in a HVOF thermal spray gun in which
premixed oxygen and propane are burnt in a combustion chamber
linked to a parallel-sided nozzle. The CFD analysis is applied to
investigate axisymmetric, steady-state, turbulent, compressible,
chemically reacting, subsonic and supersonic flow inside and outside
the gun. The gas velocity, temperature, pressure and Mach number
distributions are presented for various locations inside and outside
the gun. The calculated results show that the most sensitive
parameters affecting the process are fuel-to-oxygen gas ratio and
total gas flow rate. Gas dynamic behavior along the centerline of the
gun depends on both total gas flow rate and fuel-to-oxygen gas ratio.
The numerical simulations show that the axial gas velocity and Mach
number distribution depend on both flow rate and ratio; the highest
velocity is achieved at the higher flow rate and most fuel-rich ratio.
In addition, the results reported in this paper illustrate that the
numerical simulation can be one of the most powerful and beneficial
tools for the HVOF system design, optimization and performance
analysis.
Abstract: Wind catchers are traditional natural ventilation
systems attached to buildings in order to ventilate the indoor air. The
most common type of wind catcher is four sided one which is
capable to catch wind in all directions. CFD simulation is the perfect
way to evaluate the wind catcher performance. The accuracy of CFD
results is the issue of concern, so sensitivity analyses is crucial to
find out the effect of different settings of CFD on results. This paper
presents a series of 3D steady RANS simulations for a generic
isolated four-sided wind catcher attached to a room subjected to wind
direction ranging from 0º to 180º with an interval of 45º. The CFD
simulations are validated with detailed wind tunnel experiments. The
influence of an extensive range of computational parameters is
explored in this paper, including the resolution of the computational
grid, the size of the computational domain and the turbulence model.
This study found that CFD simulation is a reliable method for wind
catcher study, but it is less accurate in prediction of models with non
perpendicular wind directions.
Abstract: Generally flow behavior in centrifugal fan is observed
to be in a state of instability with flow separation zones on suction
surface as well as near the front shroud. Overall performance of the
diffusion process in a centrifugal fan could be enhanced by
judiciously introducing the boundary layer suction slots. With easy
accessibility of CFD as an analytical tool, an extensive numerical
whole field analysis of the effect of boundary layer suction slots in
discrete regions of suspected separation points is possible. This paper
attempts to explore the effect of boundary layer suction slots
corresponding to various geometrical locations on the impeller with
converging configurations for the slots. The analysis shows that the
converging suction slots located on the impeller blade about 25%
from the trailing edge, significantly improves the static pressure
recovery across the fan. Also it is found that Slots provided at a
radial distance of about 12% from the leading and trailing edges
marginally improve the static pressure recovery across the fan.
Abstract: Wind energy has been shown to be one of the most
viable sources of renewable energy. With current technology, the low
cost of wind energy is competitive with more conventional sources of
energy such as coal. Most blades available for commercial grade
wind turbines incorporate a straight span-wise profile and airfoil
shaped cross sections. These blades are found to be very efficient at
lower wind speeds in comparison to the potential energy that can be
extracted. However as the oncoming wind speed increases the
efficiency of the blades decreases as they approach a stall point. This
paper explores the possibility of increasing the efficiency of the
blades at higher wind speeds while maintaining efficiency at the
lower wind speeds. The design intends to maintain efficiency at
lower wind speeds by selecting the appropriate orientation and size
of the airfoil cross sections based on a low oncoming wind speed and
given constant rotation rate. The blades will be made more efficient
at higher wind speeds by implementing a swept blade profile.
Performance was investigated using the computational fluid
dynamics (CFD).
Abstract: In this paper, design, fabrication and coupled
multifield analysis of hollow out-of-plane silicon microneedle array
with piezoelectrically actuated microfluidic device for transdermal
drug delivery (TDD) applications is presented. The fabrication
process of silicon microneedle array is first done by series of
combined isotropic and anisotropic etching processes using
inductively coupled plasma (ICP) etching technology. Then coupled
multifield analysis of MEMS based piezoelectrically actuated device
with integrated 2×2 silicon microneedle array is presented. To predict
the stress distribution and model fluid flow in coupled field analysis,
finite element (FE) and computational fluid dynamic (CFD) analysis
using ANSYS rather than analytical systems has been performed.
Static analysis and transient CFD analysis were performed to predict
the fluid flow through the microneedle array. The inlet pressure from
10 kPa to 150 kPa was considered for static CFD analysis. In the
lumen region fluid flow rate 3.2946 μL/min is obtained at 150 V for
2×2 microneedle array. In the present study the authors have
performed simulation of structural, piezoelectric and CFD analysis
on three dimensional model of the piezoelectrically actuated
mcirofluidic device integrated with 2×2 microneedle array.
Abstract: It is well known that surface enhancements play an important role in augmenting the thermal performance of flat plate solar collector. In this paper, an attempt is made to explain in a comparative way the effect of surface geometry of solar collector having dimple geometry with that of a flat plate solar collector of the same size. A CFD analysis was carried out for the two cases, subjected to a constant heat flux of 600W/m2 and 1000W/m2. It can be inferred from the study that the absorber plate temperature shows a rise of average surface temperature of about 50C for the dimple solar collector when compared to a flat plate solar collector. Most importantly, the average exit water temperature shows a marked improvement of about 5.50C for a dimple solar collector as compared to that of a flat plate solar collector.
Abstract: In designing of condensers, the prediction of pressure
drop is as important as the prediction of heat transfer coefficient.
Modeling of two phase flow, particularly liquid – vapor flow under
diabatic conditions inside a horizontal tube using CFD analysis is
difficult with the available two phase models in FLUENT due to
continuously changing flow patterns. In the present analysis, CFD
analysis of two phase flow of refrigerants inside a horizontal tube of
inner diameter, 0.0085 m and 1.2 m length is carried out using
homogeneous model under adiabatic conditions. The refrigerants
considered are R22, R134a and R407C. The analysis is performed at
different saturation temperatures and at different flow rates to
evaluate the local frictional pressure drop. Using Homogeneous
model, average properties are obtained for each of the refrigerants
that is considered as single phase pseudo fluid. The so obtained
pressure drop data is compared with the separated flow models
available in literature.