scholarly journals The effect of bowl-in-piston geometry layout on fluid flow pattern

2011 ◽  
Vol 15 (3) ◽  
pp. 817-832 ◽  
Author(s):  
Zoran Jovanovic ◽  
Zlatomir Zivanovic ◽  
Zeljko Sakota ◽  
Miroljub Tomic ◽  
Velimir Petrovic
Keyword(s):  
Fluid Flow ◽  
Flow Pattern ◽  
Moving Objects ◽  
Three Dimensional ◽  
Exhaust Valve ◽  
Intake Valve ◽  
Combustion Chambers ◽  
Arbitrary Geometry ◽  
One Dimensional ◽  
Close Proximity

In this paper some results concerning the evolution of 3D fluid flow pattern through all four strokes in combustion chambers with entirely different bowl-in-piston geometry layouts ranging from ?omega? to ?simple cylinder? were presented. All combustion chambers i.e. those with ?omega? bowls, with different profiles, and those with ?cylinder? bowls, with different squish area ranging from 44% to 62%, were with flat head, vertical valves and identical elevation of intake and exhaust ports. A bunch of results emerged by dint of multidimensional modeling of nonreactive fluid flow in arbitrary geometry with moving objects and boundaries. The fluid flow pattern during induction and compression in all cases was extremely complicated and entirely three-dimensional. It should be noted that significant differences due to geometry of the bowl were encountered only in the vicinity of TDC. Namely, in the case of ?omega? bowl all three types of organized macro flows were observed while in the case of ?cylinder? bowl no circumferential velocity was registered at all. On the contrary, in the case of ?cylinder? bowl some interesting results concerning reverse tumble and its center of rotation shifting from exhaust valve zone to intake valve zone during induction stroke and vice-verse from intake valve zone to exhaust valve zone during compression were observed while in the case of ?omega? bowl no such a displacement was legible. During expansion the fluid flow pattern is fully controlled by piston motion and during exhaust it is mainly one-dimensional, except in the close proximity of exhaust valve. For that reason it is not affected by the geometry of the bowl.

scholarly journals Quasi-two-dimensional approximation for numerical simulation of flows in engine ducts

2019 ◽  
Author(s):  
V. Vlasenko ◽  
A. Shiryaeva
Keyword(s):  
High Speed ◽  
Fuel Injection ◽  
Three Dimensional ◽  
Preliminary Design ◽  
Two Dimensional ◽  
Combustion Chambers ◽  
New Approach ◽  
One Dimensional ◽  
Dimensional Approximation ◽  
3D Flows

New quasi-two-dimensional (2.5D) approach to description of three-dimensional (3D) flows in ducts is proposed. It generalizes quasi-one-dimensional (quasi-1D, 1.5D) theories. Calculations are performed in the (x; y) plane, but variable width of duct in the z direction is taken into account. Derivation of 2.5D approximation equations is given. Tests for verification of 2.5D calculations are proposed. Parametrical 2.5D calculations of flow with hydrogen combustion in an elliptical combustor of a high-speed aircraft, investigated within HEXAFLY-INT international project, are described. Optimal scheme of fuel injection is found and explained. For one regime, 2.5D and 3D calculations are compared. The new approach is recommended for use during preliminary design of combustion chambers.

On the Mathematical Modeling of Heat Transfer Characteristics of Turbulent Flames in Industrial Furnaces

2002 ◽  
Author(s):  
Essam E. Khalil
Keyword(s):  
Mathematical Modeling ◽  
Heat Transfer ◽  
Flow Pattern ◽  
Three Dimensional ◽  
Flow Regimes ◽  
Wall Heat Transfer ◽  
Governing Equations ◽  
Heat Transfer Characteristics ◽  
Combustion Chambers ◽  
Transfer Characteristics

The recent advances in numerical methods and the vast development of computers had directed the designers to better development and modifications to air flow pattern and heat transfer in combustion chambers. Extensive efforts are exerted to adequately predict the air velocity and turbulence intensity distributions in the combustor zones and to reduce the emitted pollution and noise abatement to ultimately produce quite and energy efficient combustor systems. The present work fosters mathematical modeling techniques to primarily predict what happens in three-dimensional combustion chambers simulating boiler furnaces, areo engines in terms of flow regimes and interactions. The present work also demonstrates the effect of chamber design and operational parameters on performance, wall heat transfer under various operating parameters. The governing equations of mass, momentum and energy are commonly expressed in a preset form with source terms to represent pressure gradients, turbulence and viscous action. The physical and chemical characteristics of the air and fuel are obtained from tabulated data in the literature. The flow regimes and heat transfer play an important role in the efficiency and utilization of energy. The results are obtained in this work with the aid of the three-dimensional program 3DCOMB; applied to axisymmetrical and three-dimensional complex geometry with and without swirl with liquid or gaseous fuels. The present numerical grid arrangements cover the combustion chamber in the X, R or Y and Z coordinates directions. The numerical residual in the governing equations is typically less than 0.001%. The obtained results include velocity vectors, turbulence intensities and wall heat transfer distributions in combusors. Examples of large industrial furnaces are shown and are in good agreement with available measurements in the open literature. One may conclude that flow patterns, turbulence and heat transfer in combustors are strongly affected by the inlet swirl, inlet momentum ratios, combustor geometry. Both micro and macro mixing levels are influential. The present modeling capabilities can adequately predict the local flow pattern and heat transfer characteristics in Complex combustors. Proper representation of the heat transfer and radiation flux is important in adequate predictions of large furnace performance.

scholarly journals Theoretical and Numerical Study of a Photovoltaic System with Active Fluid Cooling by a Fully-Coupled 3D Thermal and Electric Model

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 852 ◽  
Author(s):  
Antonio D’Angola ◽  
Diana Enescu ◽  
Marianna Mecca ◽  
Alessandro Ciocia ◽  
Paolo Di Leo ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Three Dimensional ◽  
Photovoltaic System ◽  
Power Gain ◽  
Fluid Flow Rate ◽  
Pv System ◽  
One Dimensional ◽  
Fluid Cooling ◽  
Fully Coupled

The paper deals with the three-dimensional theoretical and numerical investigation of the electrical performance of a Photovoltaic System (PV) with active fluid cooling (PVFC) in order to increase its efficiency in converting solar radiation into electricity. The paper represents a refinement of a previous study by the authors in which a one-dimensional theoretical model was presented to evaluate the best compromise, in terms of fluid flow rate, of net power gain in a cooled PV system. The PV system includes 20 modules cooled by a fluid circulating on the bottom, the piping network, and the circulating pump. The fully coupled thermal and electrical model was developed in a three-dimensional geometry and the results were discussed with respect to the one-dimensional approximation and to experimental tests. Numerical simulations show that a competitive mechanism between the power gain due to the cell temperature reduction and the power consumption of the pump exists, and that a best compromise, in terms of fluid flow rate, can be found. The optimum flow rate can be automatically calculated by using a semi-analytical approach in which irradiance and ambient temperature of the site are known and the piping network losses are fully characterized.

Laminar Flow Through a Circular Pipe With Side Inlets

2000 ◽  
Author(s):  
John A. Umina
Keyword(s):  
Fluid Flow ◽  
Laminar Flow ◽  
Three Dimensional ◽  
Medical Procedures ◽  
Straight Pipe ◽  
One Dimensional ◽  
Circular Tubes ◽  
Circular Pipes ◽  
Flow Through ◽  
Inlet Conditions

Abstract This study focuses on steady axisymmetric flows of a Newtonian incompressible fluid through circular pipes with side inlets. Circular tubes with a set of holes along their sidewalls are used in a number of medical procedures as straight catheters to transfer fluid into or out of the human body. We argue that all previous work on the analogous problem of flow through porous ducts is inapplicable to the problem of fluid flow through side holes of a straight pipe, due to unrealistic side inlet conditions. In this paper, we present a linear, quasi one-dimensional analysis to predict the flux of fluid that each inlet transfers based on hydraulic resistivities of both the inlets and the duct. We also perform numerical simulations to predict this inlet flux for a more complicated three-dimensional case. Finally, we show that a nonlinear analysis is necessary to determine the resistivities for this complicated flow.

Heat Transfer Characteristics of Turbulent Flames in Three-Dimensional Furnaces

2002 ◽  
Author(s):  
Essam E. Khalil
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Air Flow ◽  
Three Dimensional ◽  
Flow Regimes ◽  
Turbulent Flames ◽  
Shear Stresses ◽  
Governing Equations ◽  
Combustion Chambers ◽  
Local Flow

The recent advances in numerical methods and the vast development of computers have directed the designers to better development and modifications to air-flow pattern and heat transfer in combustion chambers. Extensive efforts are exerted to adequately predict the air velocity and turbulence intensity distributions in the combustor zones, and to reduce the air pollution and noise abatement to ultimately produce quite and energy efficient combustor systems. The present work utilizes mathematical modeling techniques to primarily predict what happens in three-dimensional combustion chambers simulating boiler furnaces, and areo engines in terms of flow regimes and interactions. The present work also demonstrates the effect of chamber design and operational parameters on performance, wall shear stresses, and vorticity under various operating parameters. The governing equations of mass, momentum and energy are commonly expressed in a preset form with source terms to represent pressure radients, turbulence and viscous action. The physical and chemical characteristics of the air and fuel are obtained from tabulated data in the literature. The flow regimes and heat transfer plays an important role in the efficiency and utilization of energy. The behavior was found to be strongly dependent on turbulent shear, mixing, blockage, wall conditions and location of fuel and air inlets. Eddies can be strong enough to have higher velocities typically near reactants supply openings. Excessive transverse flow velocities cause extra macromixing; the air flow regimes are complex and of three-dimensional nature; with the advance of computational techniques it is possible to accurately simulate three-dimensional flows. The results reported in this work were obtained with the aid of the three-dimensional program 3DCOMB; applied to axisymmetrical and three-dimensional complex geometry with and without swirl. The present numerical grid comprises, typically, 144000-grid node covering the combustion chamber volume in the X, R or Y and Z coordinates directions. The numerical residual in the governing equations typically less than 0.001%. A modified grid generation formula was proposed and incorporated in the present work. Examples of large industrial furnaces are shown and were in good agreement with available measurements in the open literature. One may conclude that flow patterns, turbulence and heat transfer in combustors are strongly affected by the inlet swirl, inlet momentum ratios, combustor geometry; both micro and macro mixing levels are influential. Greater tangential velocities and turbulence characteristics are demonstrated in situations with higher swirl intensities. The present modeling capabilities can adequately predict the local flow pattern and turbulence kinetic energy levels in complex combustors.

scholarly journals A Coupled 1D–3D Numerical Method for Buoyancy-Driven Heat Transfer in a Generic Engine Bay

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4156
Author(s):  
Blago Minovski ◽  
Lennart Löfdahl ◽  
Jelena Andrić ◽  
Peter Gullberg
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Fluid Flow ◽  
Thermal Management ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Flow Simulation ◽  
Transfer Coefficients ◽  
One Dimensional ◽  
The One

Energy efficient vehicles are essential for a sustainable society and all car manufacturers are working on improved energy efficiency in their fleets. In this process, an optimization of aerodynamics and thermal management is most essential. The objective of this work is to improve the energy efficiency using encapsulated heat generating units by focusing on predicting temperature distribution inside an engine bay. The overall objective is to make an estimate of the generated heat inside an encapsulation and consecutively use this heat for climatization purposes. The study presents a detailed numerical procedure for predicting buoyancy-driven flow and resulting natural convection inside a simplified vehicle underhood during thermal soak and cool-down events. The procedure employs a direct coupling of one-dimensional and three-dimensional methods to carry out transient one-dimensional thermal analysis in the engine solids synchronized with sequences of steady-state three-dimensional simulations of the fluid flow. The boundary heat transfer coefficients and averaged fluid temperatures in the boundary cells, computed in the three-dimensional fluid flow model, are provided as input data to the one-dimensional analysis to compute the resulting surface temperatures which are then fed back as updated boundary conditions in the flow simulation. The computed temperatures of the simplified engine and the exhaust manifolds during the thermal soak and cool-down period are in favorable agreement with experimental measurements. The present study illustrates the capabilities of the coupled thermal-flow methodology to conduct accurate and fast computations of buoyancy-driven heat transfer. The methodology can be potentially applied to design and analysis of multiple demand vehicle thermal management systems in hybrid and electrical vehicles.

Structure and function of neural networks in the retina

1988 ◽  
Vol 46 ◽  
pp. 26-27
Author(s):  
Peter Sterling
Keyword(s):  
Ganglion Cells ◽  
Three Dimensional ◽  
Structure And Function ◽  
Synaptic Connections ◽  
Visual Axis ◽  
One Dimensional ◽  
Cat Retina ◽  
Ultrathin Sections ◽  
And Function ◽  
Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

Exploring the Multidimensional Facets of Authoritarianism: Authoritarian Aggression and Social Dominance Orientation

2008 ◽  
Vol 67 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Stefano Passini
Keyword(s):  
Social Dominance ◽  
Factor Model ◽  
Three Dimensional ◽  
Social Dominance Orientation ◽  
Model Fit ◽  
Regression Analyses ◽  
One Dimensional ◽  
Confirmatory Factor ◽  
The One ◽  
Better Than

The relation between authoritarianism and social dominance orientation was analyzed, with authoritarianism measured using a three-dimensional scale. The implicit multidimensional structure (authoritarian submission, conventionalism, authoritarian aggression) of Altemeyer’s (1981, 1988) conceptualization of authoritarianism is inconsistent with its one-dimensional methodological operationalization. The dimensionality of authoritarianism was investigated using confirmatory factor analysis in a sample of 713 university students. As hypothesized, the three-factor model fit the data significantly better than the one-factor model. Regression analyses revealed that only authoritarian aggression was related to social dominance orientation. That is, only intolerance of deviance was related to high social dominance, whereas submissiveness was not.

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