Design and Analysis of a Planar 2-D Nozzle for a Small Jet-Engine

2007 ◽  
Author(s):  
Laura Moro´n ◽  
Mehdi Ghoreyshi ◽  
Afshin Banazdeh ◽  
Pericles Pilidis
Keyword(s):  
Aspect Ratio ◽  
Flow Characteristics ◽  
Performance Model ◽  
Test Case ◽  
Fighter Aircraft ◽  
Short Side ◽  
Thrust Vectoring ◽  
Jet Engine ◽  
Pressure Losses ◽  
Aspect Ratios

The thrust-vectoring in particular “Fluid” type is of increasing interest for the maneuverability and the agility of combat and fighter aircraft. This has been employed for different nozzles mainly axisymmetric and 2-dimensional. For the latter, the aspect ratio, i.e. the ratio of the long-to-short side of the nozzle has significant influence upon the exhaust and thrust-vectoring performance. The effectiveness of a high aspect-ratio nozzle in order to deflect the jet engine’s thrust has been demonstrated {Hiley, 1975} but, such large aspect ratios often causes increasing of the structure weight and internal pressure losses. Here, the design of a two-dimensional nozzle with respect to the thrust-loss factor of a small jet-engine is presented. Computational Fluid Dynamics (CFD) techniques were used in order to simulate the nozzle’s flow characteristics under various engine’s operating settings as well as different aspect-ratio designs. Computations results were obtained from the “Fluent” program. All developed models are 3-D and meshed by using “Gridgen” code. Moreover, the boundary conditions were obtained by using of the engine’s performance model developed in TURBOMATCH program. Also, the paper describes an experiment in order to predict the engine’s performance for a test case that has aspect ratio of 8.5. The CFD results were compared with experimental measurements. The results showed that nozzle with higher aspect-ratio results in larger pressure losses, while, its thrust discharge coefficient is not far from the moderate aspect-ratio nozzle.

Editorial on Future Jet Technologies

2014 ◽  
Vol 31 (4) ◽  
Author(s):  
Benjamin Gal-Or
Keyword(s):  
Flight Control ◽  
Landing Gear ◽  
Engineering Practice ◽  
Mobile Telecommunication ◽  
Fighter Aircraft ◽  
Thrust Vectoring ◽  
Jet Engine ◽  
Stealth Technology ◽  
Forced Landing ◽  
Expected Benefits

AbstractThe jet engine is the prime flight controller in post-stall flight domains where conventional flight control fails, or when the engine prevents catastrophes in training, combat, loss of all airframe hydraulics (the engine retains its own hydraulics), loss of one engine, pilot errors, icing on the wings, landing gear and runway issues in takeoff and landing and in bad-whether recoveries. The scientific term for this revolutionary technology is “jet-steering”, and in engineering practice – “thrust vectoring”, or “TV”.Jet-Steering in advanced fighter aircraft designs is integrated with stealth technology. The resulting classified Thrust-Vectoring-Stealth (“TVS”) technology has generated a second jet-revolution by which all Air-&-Sea-Propulsion Science and R&D are now being reassessed.ClassifiedOne, and perhaps a key conclusion presented here, means that bothMobile telecommunication of safe links between flyers and combat drones (“UCAVs”) at increasingly deep penetrations into remote, congested areas, can gradually be purchased-developed-deployed and then operated by extant cader of tens of thousandsWe also provide 26 references [17–43] to a different, unclassified technology that enhances TV-inducedExpected benefits include anti-terror recoveries from emergencies, like forced landing on unprepared runways or highways, or recoveries from all airframe-hydraulics-outs, asymmetric ice on wings, landing gear catastrophes, and recoveries from pilot errors and bad-whether incidents [Rule 9(7)].

scholarly journals Flow Characteristics of the Entrance Region with Roughness Effect within Rectangular Microchannels

Micromachines ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 30
Author(s):  
Haiwang Li ◽  
Yujia Li ◽  
Binghuan Huang ◽  
Tiantong Xu
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Stokes Equations ◽  
Critical Role ◽  
Flow Characteristics ◽  
Entrance Region ◽  
Working Fluid ◽  
Asymmetric Distribution ◽  
Rectangular Microchannels ◽  
Aspect Ratios

We conducted systematic numerical investigations of the flow characteristics within the entrance region of rectangular microchannels. The effects of the geometrical aspect ratio and roughness on entrance lengths were analyzed. The incompressible laminar Navier–Stokes equations were solved using finite volume method (FVM). In the simulation, hydraulic diameters ( D h ) ranging from 50 to 200 µm were studied, and aspect ratios of 1, 1.25, 1.5, 1.75, and 2 were considered as well. The working fluid was set as water, and the Reynolds number ranged from 0.5 to 100. The results showed a good agreement with the conducted experiment. Correlations are proposed to predict the entrance lengths of microchannels with respect to different aspect ratios. Compared with other correlations, these new correlations are more reliable because a more practical inlet condition was considered in our investigations. Instead of considering the influence of the width and height of the microchannels, in our investigation we proved that the critical role is played by the aspect ratio, representing the combination of the aforementioned parameters. Furthermore, the existence of rough elements obviously shortens the entrance region, and this effect became more pronounced with increasing relative roughness and Reynolds number. A similar effect could be seen by shortening the roughness spacing. An asymmetric distribution of rough elements decreased the entrance length compared with a symmetric distribution, which can be extrapolated to other irregularly distributed forms.

A Hyper-Ellipsoid Approach for Inverse Lack-of-Knowledge Uncertainty Quantification

2021 ◽  
Vol 7 (2) ◽  
Author(s):  
Norbert Ludwig ◽  
Fabian Duddeck ◽  
Marco Daub
Keyword(s):  
Uncertainty Quantification ◽  
Engine Performance ◽  
Computation Time ◽  
Solution Procedure ◽  
Performance Model ◽  
High Dimensional ◽  
System Response ◽  
Test Case ◽  
Jet Engine ◽  
Output Space

Abstract This paper presents a novel methodology to solve an inverse uncertainty quantification problem where only the variation of the system response is provided by a small set of experimental data. Furthermore, the method is extended for cases where the uncertainty of the response quantities is given by an incomplete set of statistical moments. For both cases, the uncertainty on the output space is represented by a minimum volume enclosing ellipsoid (MVEE). The actual inverse uncertainty quantification is conducted by identifying also a hyper-ellipsoid for the input parameters, which has an image on the output space that matches the MVEE as close as possible. Hence, the newly introduced approach is a contribution to the field of nonprobabilistic uncertainty quantification methods. Compared to literature, the new approach has often superior accuracy and especially an improved efficiency for high-dimensional problems. The method is validated first by an analytical test case and subsequently applied to a jet engine performance model, where this type of inverse uncertainty quantification has to be solved to allow for a consistent and integrated solution procedure. In both cases, the results are compared with an inverse method where the variability on the input side is quantified by a multidimensional interval. It can be shown that the hyper-ellipsoid approach is superior with respect to the computation time in high-dimensional problems encountered not only in jet engine design.

scholarly journals Wind Tunnel Testing on Start/Unstart Characteristics of Finite Supersonic Biplane Wing

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Hiroshi Yamashita ◽  
Naoshi Kuratani ◽  
Masahito Yonezawa ◽  
Toshihiro Ogawa ◽  
Hiroki Nagai ◽  
...  
Keyword(s):  
Mach Number ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Wind Tunnels ◽  
Wind Tunnel Testing ◽  
Ratio Model ◽  
Number Range ◽  
Aspect Ratios ◽  
Schlieren System

This study describes the start/unstart characteristics of a finite and rectangular supersonic biplane wing. Two wing models were tested in wind tunnels with aspect ratios of 0.75 (model A) and 2.5 (model B). The models were composed of a Busemann biplane section. The tests were carried out using supersonic and transonic wind tunnels over a Mach number range of0.3≤M∞≤2.3with angles of attack of 0°, 2°, and 4°. The Schlieren system was used to observe the flow characteristics around the models. The experimental results showed that these models had start/unstart characteristics that differed from those of the Busemann biplane (two dimensional) owing to three-dimensional effects. Models A and B started at lower Mach numbers than the Busemann biplane. The characteristics also varied with aspect ratio: model A (1.3<M∞<1.5) started at a lower Mach number than model B (1.6<M∞<1.8) owing to the lower aspect ratio. Model B was located in the double solution domain for the start/unstart characteristics atM∞=1.7, and model B was in either the start or unstart state atM∞=1.7. Once the state was determined, either state was stable.

scholarly journals Numerical Computations for Flow Patterns and Force Statistics of Three Rectangular Cylinders

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Hamid Rahman ◽  
Shams-ul-Islam ◽  
Waqas Sarwar Abbasi ◽  
Raheela Manzoor ◽  
Fazle Amin ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Flow Characteristics ◽  
Drag And Lift Coefficients ◽  
Aspect Ratios ◽  
Spacing Ratio ◽  
Drag And Lift ◽  
Rectangular Cylinders

In this work, numerical simulations are performed in order to study the effects of aspect ratio (AR) and Reynolds number (Re) on flow characteristics of three side-by-side rectangular cylinders for fixed spacing ratio ( g ), using the lattice Boltzmann method (LBM). The Reynolds number varies within the range 60 ≤ Re ≤ 180, aspect ratio is between 0.25 and 4, and spacing ratio is fixed at g  = 1.5. The flow structure mechanism behind the cylinders is analyzed in terms of vorticity contour visualization, time-trace analysis of drag and lift coefficients, power spectrum analysis of lift coefficient and variations of mean drag coefficient, and Strouhal number. For different combinations of AR and Re, the flow is characterized into regular, irregular, and symmetric vortex shedding. In regular and symmetric vortex shedding the drag and lift coefficients vary smoothly while reverse trend occurs in irregular vortex shedding. At small AR, each cylinder experiences higher magnitude drag force as compared to intermediate and large aspect ratios. The vortex shedding frequency was found to be smaller at smaller AR and increased with increment in AR.

Heat Transfer Analysis Of Nano-fluid Flow In A Converging Nozzle With Different Aspect Ratios

2017 ◽  
Vol 20 (4) ◽  
pp. 161-167 ◽  
Author(s):  
T. Sathish
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Aspect Ratio ◽  
Flow Rate ◽  
Flow Characteristics ◽  
Heat Transfer Analysis ◽  
Element Analysis ◽  
Frictional Loss ◽  
Nano Fluid ◽  
Aspect Ratios

The study evaluates the nanofluid using finite element analysis with base fluid (water) and seeding particles (Aluminum oxide). This is placed over a convergence channel consisting of varying aspect ratio that are evaluated quantitatively to enhance the heat transfer properties of the nanofluid.We have considered frictional loss characteristics that increases the flow of the fluid with Reynolds numbers varying from 100-2000 is compared.A baseline modeling is established using the methodology analysis for the fluid flow over a rectangular chamber that is designed in the form of a square duct of ratio 1:1. The analysis is carried out over the heat transfer and flow rate characteristics of the nanofluid that converges into the square ducts with different aspect ratio, is analyzed.The concentration of the nano fluid is maintained at the constant rate, which is used for studying the flow rate influence over different aspect ratios. The thermal and flow characteristics is analyzed in such situation and validated against other literatures to check the efficiency in the converging rectangular oxygen free copper channel.The simulation results shows an increase in temperature on the duct out and drop in temperature on the inlet walls of the tube.The pressure changes and shear stress along the walls of the chamber is not much noticed and it is constant throughout the entire chamber.

Numerical Study on Effect of Volume Fraction of Nanoparticles on Rayleigh-Bernard Convection in Different Enclosures

2014 ◽  
Vol 592-594 ◽  
pp. 945-950 ◽  
Author(s):  
S. Senthil Kumar ◽  
S. Karthikeyan
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Boussinesq Approximation ◽  
Working Fluid ◽  
Volume Fractions ◽  
Aspect Ratios ◽  
Fluid Flow Characteristics

Numerical investigations of Rayleigh-Bernard convection in enclosures of different modified bottom and top surfaces filled with Au-Water Nanofluid with different volume fractions are presented. This paper describes a numerical predication of heat transfer and fluid flow characteristics inside enclosures bounded by modified bottom and top surfaces and two periodic straight vertical walls. Simulations are carried out for a Rayleigh number of 6×104 and two aspect ratios (0.25 & 0.5) with working fluid as Au-Water Nanofluid and The same analyses are performed with the Nanofluid having Au nanoparticles of same size and different volume fraction of φ = 5%, 10%, 15% and 20 % in order to see the effect of Nanofluid volume fraction on heat transfer. The Boussinesq approximation is used in order to take density change effect in the governing equations. The study investigates the effect of the nanoparticles volume fraction, and the aspect ratio on the heat transfer. The results are presented in terms of isotherms, streamlines local and average surface Nusselt numbers. Results show that the flow and isotherms are affected by the geometry shape and by the presence of nanoparticles with different volume fractions. It is also shown that for a fixed value of aspect ratio, the convective heat transfer is decreased for the increase in volume fraction of Nanofluid.

Scaling of Flow Characteristics and Power Consumption With Profile Height for Miniature Centrifugal Fans

2007 ◽  
Author(s):  
P. A. Walsh ◽  
V. Egan ◽  
R. Grimes ◽  
E. Walsh
Keyword(s):  
Aspect Ratio ◽  
Power Consumption ◽  
Flow Rate ◽  
Scaling Laws ◽  
Flow Characteristics ◽  
Pressure Rise ◽  
Maximum Flow ◽  
Aspect Ratios ◽  
Low Profile ◽  
Centrifugal Fans

This paper addresses issues that relate to downscaling the height of centrifugal fans for application in low profile technologies, such as the cooling of portable power electronics. The parameters studied throughout the paper include flow rate, pressure rise and power consumption characteristics. The former two of these are measured using a fan characterization rig and the latter by directly measuring the power supplied to the fan. These are studied for fans ranging in diameter from 15 to 30mm and with profile heights ranging from 0.3mm to 15mm. It is found that all of the phenomena encountered are best described in terms of fan aspect ratio. Overall, the results show that the conventional scaling laws cannot be accurately applied when the blade profile alone is being scaled. Indeed the only parameter that was observed to be accurately predicted by the scaling laws was the pressure rise attainable but was only accurate for fan aspect ratios greater than 0.17. Below this, the measured pressure rise characteristics fell logarithmically toward zero. The results also showed that there is no advantage to using fans with aspect ratio greater than 0.3. This was because the maximum flow rate was achieved at this aspect ratio and decreased slightly as it was further increased. Overall, the scaling phenomena described throughout this paper are invaluable to designer of efficient low profile cooling solutions that are to incorporate such fans.

A Three-Dimensional Model for the Prediction of Shock Losses in Compressor Blade Rows

1983 ◽  
Author(s):  
Arthur J. Wennerstrom ◽  
Steven L. Puterbaugh
Keyword(s):  
Aspect Ratio ◽  
Three Dimensional ◽  
Leading Edge ◽  
Compressor Blade ◽  
Turbine Engines ◽  
Test Case ◽  
Three Dimensional Model ◽  
Aspect Ratios ◽  
Flow Effects ◽  
Shock Loss

A design trend evident in newly evolving aircraft turbine engines is a reduction in the aspect ratio of blading employed in fans, compressors, and turbines. As aspect ratio is reduced, various three-dimensional flow effects become significant which at higher aspect ratios could safely be neglected. This paper presents a new model for predicting the shock loss through a transonic or supersonic compressor blade row operating at peak efficiency. It differs from the classical Miller-Lewis-Hartmann normal shock model by taking into account the spanwise obliquity of the shock surface due to leading-edge sweep, blade twist, and solidity variation. The model is evaluated in combination with two test cases. Each was a low-aspect-ratio transonic stage which had exceeded its efficiency goals. Use of the revised shock loss model contributed 2.11 points to the efficiency of the first test case and 1.08 points to the efficiency of the second.

Head Loss and Flow Characteristics for Turning Flow Driven by Surface Tension Force Inside Open Microchannel

2004 ◽  
Author(s):  
Y. F. Chen ◽  
M. H. Chen ◽  
R. J. Yu ◽  
F. G. Tseng ◽  
Ching-Chang Chieng
Keyword(s):  
Surface Tension ◽  
Aspect Ratio ◽  
Flow Characteristics ◽  
Surface Tension Force ◽  
Head Loss ◽  
Front Velocity ◽  
Channel Height ◽  
Liquid Front ◽  
Aspect Ratios ◽  
Open Microchannel

Present study demonstrates the head loss and the flow characteristics as the open microchannel makes turns. The microchannels are of various aspect ratios of depth/width ranging from 0.5 to 2, and makes turns with different angles ranging from 60 to 120 degrees. The investigations are performed both by experiments and numerical simulations based on first principle equations. For the open channel system, the flow is mainly driven by surface tension under same pressure atmosphere. For liquid flow in open microchannel without turn, the liquid front velocity decreases but the interface area of liquid-gas increase as flow moves downstream. For turning flows, liquid front velocity is decreased firstly and then increased sharply at the turning point. Furthermore, the liquid front velocity can be increased for higher aspect ratio of channel height and width, and the effect of aspect ratio is significant up to aspect ratio between 1.0–1.5. Detailed flow characteristics as well as the head loss coefficient due to microchannel turning are discussed.

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