scholarly journals Design study of Coanda devices for transonic circulation control

2017 ◽  
Vol 121 (1243) ◽  
pp. 1368-1391 ◽  
Author(s):  
M. Forster ◽  
R. Steijl
Keyword(s):  
Deflection Angle ◽  
Operating Conditions ◽  
Radius Of Curvature ◽  
Circulation Control ◽  
Height Ratio ◽  
Attached Flow ◽  
Nozzle Shape ◽  
Control Devices ◽  
Coanda Jet ◽  
Control Surfaces

ABSTRACTCirculation control via blowing over Coanda surfaces at transonic freestream Mach numbers is investigated using numerical simulations. The performance and sensitivity of several circulation control devices applied to a supercritical aerofoil are assessed. Different Coanda devices were studied to assess the effect of Coanda radius-to-slot height ratio, nozzle shape and Coanda surfaces with a step. The range of operating conditions for which a supersonic Coanda jet remained attached at transonic freestream conditions were extended by increasing the radius of curvature at the slot exit for Coanda devices with a converging nozzle. Additional improvements were found by reducing the strength of shock boundary-layer interactions on the Coanda surface by expanding the jet flow using a converging-diverging nozzle and also by introducing a step between the Coanda surface and the nozzle exit. The performance when using a converging-diverging nozzle can be matched using a simple stepped Coanda device. It is shown that circulation control has the potential to match the performance of traditional control surfaces during regimes of attached flow at transonic speeds, up to an equivalent aileron deflection angle of 10°. In addition, lift augmentation ratios ΔCl/Cμof over 100 were achieved.

scholarly journals Sensitivity of Supersonic ORC Turbine Injector Designs to Fluctuating Operating Conditions

2015 ◽  
Author(s):  
Elio A. Bufi ◽  
Paola Cinnella ◽  
Xavier Merle
Keyword(s):  
Method Of Characteristics ◽  
Organic Rankine Cycle ◽  
Design Procedure ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Real Gas ◽  
Real Gas Effects ◽  
Nozzle Shape ◽  
Turbine Design ◽  
The Impact

The design of an efficient organic rankine cycle (ORC) expander needs to take properly into account strong real gas effects that may occur in given ranges of operating conditions, which can also be highly variable. In this work, we first design ORC turbine geometries by means of a fast 2-D design procedure based on the method of characteristics (MOC) for supersonic nozzles characterized by strong real gas effects. Thanks to a geometric post-processing procedure, the resulting nozzle shape is then adapted to generate an axial ORC blade vane geometry. Subsequently, the impact of uncertain operating conditions on turbine design is investigated by coupling the MOC algorithm with a Probabilistic Collocation Method (PCM) algorithm. Besides, the injector geometry generated at nominal operating conditions is simulated by means of an in-house CFD solver. The code is coupled to the PCM algorithm and a performance sensitivity analysis, in terms of adiabatic efficiency and power output, to variations of the operating conditions is carried out.

Heat Transfer in Radially Rotating Pin-Fin Channel at High Rotation Numbers

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Miin Liou ◽  
Tsun Lirng Yang ◽  
Guo Fang Hong
Keyword(s):  
Heat Transfer ◽  
Flow Region ◽  
Operating Conditions ◽  
Previous Attempt ◽  
Height Ratio ◽  
Pin Fin ◽  
Nusselt Numbers ◽  
Rotation Numbers ◽  
The Individual ◽  
Selection Of

Endwall heat transfer measurements for a radially rotating rectangular pin-fin channel with the width-to-height ratio (aspect ratio) of 8 are performed at the parametric conditions of 5000≤Re≤20,000, 0≤Ro≤1.4, and 0.1≤Δρ/ρ≤0.21. Centerline heat transfer levels along the leading and trailing endwalls of the rotating pin-fin channel are, respectively, raised to 1.77–3.72 and 3.06–5.2 times of the Dittus–Boelter values. No previous attempt has examined the heat transfer performances for the pin-fin channel at such high rotation numbers. A selection of experimental data illustrates the individual and interactive Re, Ro, and buoyancy number (Bu) effects on heat transfer. Spanwise heat transfer variations between two adjoining pin rows are detected with the averaged Nusselt numbers (Nu) determined. A set of empirical equations that calculates Nu values over leading and trailing endwalls in the developed flow region is derived to correlate all the heat transfer data generated by this study and permits the evaluation of interactive and individual effects of Re, Ro, and Bu on Nu. With the aid of the Nu correlations derived, the operating conditions with the worst heat transfer scenarios for this rotating pin-fin channel are identified.

Flowfield and Pressure Measurements in a Rotating Two-Pass Duct With Staggered Rounded Ribs Skewed 45Degrees to the Flow

2004 ◽  
Vol 128 (2) ◽  
pp. 340-348 ◽  
Author(s):  
Tong-Miin Liou ◽  
Y. Sian Hwang ◽  
Yi-Chen Li
Keyword(s):  
Friction Factor ◽  
Pressure Coefficient ◽  
Operating Conditions ◽  
Friction Loss ◽  
Main Stream ◽  
Pressure Measurements ◽  
Height Ratio ◽  
Mean Velocity ◽  
Square Duct ◽  
Pressure Distributions

Laser-Doppler velocimetry and pressure measurements are presented of the local velocity and wall pressure distributions in a rotating two-pass square duct with staggered ribs placed on the leading and trailing walls at an angle of 45deg to the main stream. The ribs were square in cross section with the radii of rounds and fillets to rib height ratios of 0.33. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number Ro ranged from 0 to 0.2. Results are documented in terms of the evolutions of both main flow and cross-stream secondary flow, the distributions of the pressure coefficient, and the variation of friction factor with Ro. For CFD reference, the periodic fully developed flow condition is absent for the present length of the rotating passage roughened with staggered 45deg ribs. In addition, the relationships between the regional averaged Nusselt number, transverse and convective mean velocity component, and turbulent kinetic energy are addressed. Using these relationships the general superiority of heat transfer enhancement of the staggered 45deg ribs arrangement over the in-line one can be reasonably illustrated. Simple expressions are obtained to correlate the friction factor with Ro, which are lacking in the published literature for passages ribbed with staggered 45deg ribs. The staggered 45deg ribs are found to reduce the friction loss to about 88%±1% of the in-line 45deg ribs for the rotating passage under the same operating conditions. The respective contributions of the angled ribs and passage rotation on the passage friction loss are identified.

Wire Stress Calculations in Helical Strands Undergoing Bending

1992 ◽  
Vol 114 (3) ◽  
pp. 212-219 ◽  
Author(s):  
M. Raoof ◽  
Y. P. Huang
Keyword(s):  
Theoretical Model ◽  
Axial Stress ◽  
Operating Conditions ◽  
Radius Of Curvature ◽  
Axial Component ◽  
Practical Applications ◽  
Bending Stresses ◽  
Parametric Studies ◽  
Steel Cables ◽  
The Individual

Steel cables play an important role in many offshore applications. In many cases, an understanding of the magnitude and pattern of bending stresses in the individual component wires of a bent strand is essential for minimizing the risk of their failure under operating conditions. Following previously reported experimental observations, a theoretical model is proposed for obtaining the magnitude of wire bending stresses in a multi-layered and axially preloaded spiral strand fixed at one end and subsequently bent to a constant radius of curvature. The individual wire bending stresses are shown to be composed of two components. The first component is the axial stress generated in the wires due to interwire/interlayer shear interactions between the wires in a bent cable, and the second component is associated with the wires bending about their own axes. Using the theoretical model, which includes the effects of interwire friction, parametric studies on a number of realistic helical strands with widely different cable (and wire) diameters and lay angles subjected to a range of practical mean axial loads, and subsequently bent to a range of radii of curvature with one end of the cable fixed against rotation, have been carried out. It is shown that for most practical applications, the axial component of wire stresses due to friction is much greater than the second component of bending stresses associated with the individual wires bending about their own axes.

2D Parametric Study Using CFD of a Circulation Control Inlet Guide Vane

2007 ◽  
Author(s):  
H. E. Hill ◽  
W. F. Ng ◽  
P. P. Vlachos ◽  
S. A. Guillot ◽  
D. Car
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Circulation Control ◽  
Trailing Edge ◽  
Pressure Losses ◽  
Supply Pressure ◽  
Edge Radius

Circulation control inlet guide vanes (IGVs) may provide significant benefits over current IGVs that employ mechanical means for flow turning. This paper presents the results of a two-dimensional computational study on a circulation control IGV that takes advantage of the Coanda effect for flow vectoring. The IGV in this study is an uncambered airfoil that alters circulation around itself by means of a Coanda jet that exhausts along the IGV’s trailing edge surface. The IGV is designed for an axial inlet flow at a Mach number of 0.54 and an exit flow angle of 11 degrees. These conditions were selected to match the operating conditions of the 90% span section of the IGV of the TESCOM compressor rig at the Compressor Aero Research Laboratory (CARL) located at Wright-Patterson AFB, the hardware that is being used as the baseline in this study. The goal of the optimization was to determine the optimal jet height, trailing edge radius, and supply pressure that would meet the design criteria while minimizing the mass flow rate and pressure losses. The optimal geometry that was able to meet the design requirements had a jet height of h/Cn = 0.0057 and a trailing edge Radius R/Cn = 0.16. This geometry needed a jet to inflow total pressure ratio of 1.8 to meet the exit turning angle requirement. At this supply pressure ratio the mass flow rate required by the flow control system was 0.71 percent of the total mass flow rate through the engine. The optimal circulation control IGV had slightly lower pressure losses when compared with a reference cambered IGV.

Numerical simulation of circulation control turbine cascade with Coanda jet and counter-flow blowing at high Mach numbers

2017 ◽  
Vol 121 (1243) ◽  
pp. 1239-1260 ◽  
Author(s):  
Y. Feng ◽  
Y. Song ◽  
F. Chen
Keyword(s):  
Guide Vane ◽  
Inlet Guide Vane ◽  
Circulation Control ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Suction Surface ◽  
Counter Flow ◽  
Flow Angle ◽  
High Mach ◽  
Coanda Jet

ABSTRACTThe performance of a circulation-control inlet guide vane that makes use of the Coanda effect was studied numerically in a high Mach number turbine cascade. The effect of different shapes (elliptic and circular) of the Coanda surface at the blade trailing edge was investigated by implementing both a Coanda jet and a counter-flow blowing. Under high subsonic flow conditions, with a total blowing ratio of 3% of the mainstream, the circulation control cascade can reach the same performance as the reference stator with a 13.5% reduction in the axial chord length, with minimal increase of the energy loss coefficient. The Coanda surfaces with small curvature are more efficient in entraining the mainstream flow, and they achieve better aerodynamic performance. The wall attachment of the Coanda jet is improved by employing counter-flow blowing, resulting in a slight increase of both the exit flow angle and the expansion ratio. Under supersonic flow conditions at the cascade exit, it is more difficult for the circulation control cascade to reach the appropriate flow turning due to a premature shock wave, which is absent in the original cascade until the very end of the suction surface.

Crater Geometry and Volume From Electro-Discharge Machined Surface Profiles by Data Dependent Systems

1980 ◽  
Vol 102 (4) ◽  
pp. 289-295 ◽  
Author(s):  
S. M. Pandit ◽  
K. P. Rajurkar
Keyword(s):  
Impulse Response Function ◽  
Surface Profile ◽  
Operating Conditions ◽  
Surface Generation ◽  
Radius Of Curvature ◽  
Regression Equations ◽  
Machining Time ◽  
Machined Surface ◽  
Depth Ratio ◽  
Single Discharge

This paper applies a recently developed methodology called Data Dependent Systems to model and analyse the process of Electro-Discharge Machined (EDM) surface generation. A first order stochastic differential equation is developed and physically interpreted from the EDM surface profile measurements under varying pulse duration and machining time. The impulse response function of this model is used to define a characteristic crater geometry. The depth and diameter to depth ratio of such a crater is determined and employed in deriving the radius of curvature and the volume. Experimental measurements are utilized to illustrate the development of regression equations and nomograms, useful in practice to obtain surfaces with desired geometry. It is shown that the depth diameter to depth ratio, and volume of the characteristic craters obtained from actual multiple discharge situation under operating conditions agree fairly well with the past single discharge physics investigations.

Pressure and Flow Characteristics in a Rotating Two-Pass Square Duct With 45° Angled Ribs

2003 ◽  
Author(s):  
Tong-Miin Liou ◽  
Guang-Yuan Dai
Keyword(s):  
Secondary Flow ◽  
Pressure Coefficient ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Laser Doppler Velocimeter ◽  
Main Stream ◽  
Height Ratio ◽  
Mean Velocity ◽  
Square Duct ◽  
Pressure Transducers

Measurements are presented of the local velocity and wall static-pressure distributions by using laser-Doppler velocimeter and pressure transducers, respectively, in a rotating two-pass square duct with ribs placed on the leading and trailing walls at an angle of 45° to the main stream. The ribs were square in cross-section and in a parallel mode of arrangement. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number Ro ranged from 0 to 0.2. Results are addressed in terms of the evolutions of both main flow and cross-stream secondary flow and the distributions of the pressure coefficient, which are lacking in the published literature for ducts ribbed with 45° ribs and under rotation. In addition, the relationships between the regional averaged Nusselt number, transverse and convective mean velocity component, and turbulent kinetic energy are documented. The 45° ribs are found to reduce the pressure loss to 60% of the 90° ribs for rotating duct under same operating conditions. For CFD reference, the fully developed flow condition is absent for the rotating ducts investigated. The measured evolution of complex secondary flow vortices is believed to be a challenge to numerical simulations.

scholarly journals Modeling of the operation of the reserve source of electric energy of railway traffic control devices

2018 ◽  
Vol 19 (12) ◽  
pp. 579-584
Author(s):  
Piotr Osa ◽  
Jerzy Wojciechowski ◽  
Marek Wójtowicz ◽  
Nikolai Osmolovskii
Keyword(s):  
Simulation Model ◽  
Traffic Control ◽  
Electric Energy ◽  
Power Source ◽  
Operating Conditions ◽  
Basic Part ◽  
Railway Traffic ◽  
Control Devices ◽  
Traffic Control Devices

The article presents issues related to the problem of modeling the work of a reserve source of electric energy for railway traffic control devices. The problems of srk devices and the construction and concept of powering them into electricity were outlined. The basic part presents a simulation model of the operation of a generator set, used as a reserve power source. Modifications of the model to work in the most important operating conditions are shown. The results of simulation calculations are presented.

A Simplified Method for Estimating the Properties of Thin Aerofoils Influenced by Jet

1960 ◽  
Vol 64 (593) ◽  
pp. 292-294
Author(s):  
Svetopolk Pivko
Keyword(s):  
Deflection Angle ◽  
Simple Procedure ◽  
Leading Edge ◽  
Inviscid Flow ◽  
Edge Region ◽  
Trailing Edge ◽  
First Case ◽  
Simplified Method ◽  
Attached Flow ◽  
Special Case

To predict the aerodynamical properties of a thin aerofoil, provided with a high velocity jet sheet in its trailing edge region, a simple procedure is proposed as follows. Two general separate cases concerned with the effect of a jet on an aerofoil are considered. In the first case, the jet is blown tangentially over the upper surface of the aerofoil, while in the second case, the jet is ejected at a deflection angle from the trailing edge. In this analysis a procedure which is similar to the classical Glauert treatment of thin aerofoils is applied.Consider first the special case of a thin aerofoil placed at zero incidence in a two-dimensional inviscid flow of velocity V0, with a jet emerging with an exit velocity V1 at distance x1 from the leading edge and blown tangentially over the upper surface of the aerofoil (Fig. 1). It is assumed that an effectively attached flow may be obtained.

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