Improvement of the Performance of Conical Diffusers by Vortex Generators

1974 ◽  
Vol 96 (1) ◽  
pp. 4-10 ◽  
Author(s):  
Y. Senoo ◽  
M. Nishi
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Area Ratio ◽  
Vortex Generators ◽  
Pressure Recovery ◽  
Divergence Angle ◽  
Recovery Coefficient ◽  
Conical Diffuser ◽  
Pressure Recovery Coefficient

Vortex generators, which consist of small blades, are applied to conical diffusers the divergence angles of which are 8, 12, 16, 20, and 30 deg, respectively. The area ratio of each diffuser is four. The experiment covers the influence of various parameters, such as the arrangement of blades, inlet boundary layer thickness, and location of vortex generators relative to the conical diffuser, on the pressure-recovery coefficient. The experiment shows that the vortex generators prevent the flow in a conical diffuser from separating up to a divergence angle of 16 deg, and that the pressure-recovery coefficient is approximately equal to that of conventional best conical diffusers.

Performance of a Diffuser with Fully-Developed Pipe Flow at Entry

1963 ◽  
Vol 67 (635) ◽  
pp. 733-733 ◽  
Author(s):  
P. Bradshaw
Keyword(s):  
Boundary Layer ◽  
Pipe Flow ◽  
Boundary Layer Thickness ◽  
Static Pressure ◽  
Pressure Coefficient ◽  
Mean Velocity ◽  
Recovery Coefficient ◽  
Conical Diffuser ◽  
Definition Of ◽  
Pressure Recovery Coefficient

Cockrell and Markland have found that the static-pressure recovery coefficient of a conical diffuser, which is well known to decrease as the (turbulent) boundary layer thickness at entry increases, actually rises again when the inlet boundary layer is so thick as to approximate to fully-developed pipe flow. It may be noted that this is not a consequence of the definition of the pressure coefficient because, for typical pipe flow velocity profiles, the pressure coefficient based on mean velocity, , is very nearly the same as that based on momentum flux .

Effect of the turning angle on the flow and performance characteristics of long S-shaped circular diffusers

2003 ◽  
Vol 217 (1) ◽  
pp. 29-41 ◽  
Author(s):  
R B Anand ◽  
L Rai ◽  
S N Singh
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Area Ratio ◽  
Secondary Flows ◽  
Performance Characteristics ◽  
Pressure Recovery ◽  
Recovery Coefficient ◽  
Turning Angle ◽  
And Performance ◽  
Pressure Recovery Coefficient

The effect of the turning angle on the flow and performance characteristics of long S-shaped circular diffusers (length-inlet diameter ratio, L/Di = 11:4) having an area ratio of 1.9 and centre-line length of 600 mm has been established. The experiments are carried out for three S-shaped circular diffusers having angles of turn of 15°/15°, 22.5°/22.5° and 30°/30°. Velocity, static pressure and total pressure distributions at different planes along the length of the diffusers are measured using a five-hole impact probe. The turbulence intensity distribution at the same planes is also measured using a normal hot-wire probe. The static pressure recovery coefficients for 15°/15°, 22.5°/22.5° and 30°/30° diffusers are evaluated as 0.45, 0.40 and 0.35 respectively, whereas the ideal static pressure recovery coefficient is 0.72. The low performance is attributed to the generation of secondary flows due to geometrical curvature and additional losses as a result of the high surface roughness (~0.5 mm) of the diffusers. The pressure recovery coefficient of these circular test diffusers is comparatively lower than that of an S-shaped rectangular diffuser of nearly the same area ratio, even with a larger turning angle (90°/90°), i.e. 0.53. The total pressure loss coefficient for all the diffusers is nearly the same and seems to be independent of the angle of turn. The flow distribution is more uniform at the exit for the higher angle of turn diffusers.

Performance of Conical Diffuser on Liquid Jet Gas Ejector

2014 ◽  
Vol 493 ◽  
pp. 145-150 ◽  
Author(s):  
Daru Sugati ◽  
Indarto ◽  
Purnomo ◽  
Sutrisno
Keyword(s):  
Void Fraction ◽  
Flow Rate ◽  
Rate Increase ◽  
Pressure Profile ◽  
Pressure Recovery ◽  
Liquid Jet ◽  
Recovery Coefficient ◽  
Final Value ◽  
Conical Diffuser ◽  
Pressure Recovery Coefficient

Liquid gas ejector uses liquid as the motive fluid and gas as the entrained fluid. The presence of gas in the liquid reduces the performance of the ejector, especially the diffuser. To observe the effect of entrained gas on the diffuser performance, a series of experiment was conducted.In this research, the motive flow rate was varied from 1.52 to 2.02 l/s and the entrained rate from 0.118 l/s to 0.944 l/s. Its effects on the pressure profile and pressure recovery were observed. If the entrained rate increase, the pressure of the throat upstream, as well as downstream, increase. In the diffuser, longer distance is needed for the pressure to reach its final value. Pressure recovery is mainly affected by void fraction. The higher the void fraction the lower the pressure recovery coefficient

scholarly journals Computational Characterization of a Rectangular Vortex Generator on a Flat Plate for Different Vane Heights and Angles

2019 ◽  
Vol 9 (5) ◽  
pp. 995 ◽  
Author(s):  
Iosu Ibarra-Udaeta ◽  
Iñigo Errasti ◽  
Unai Fernandez-Gamiz ◽  
Ekaitz Zulueta ◽  
Javier Sancho
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Stokes Equations ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Local Boundary ◽  
Passive Flow Control ◽  
Vortex Size

Vortex generators (VG) are passive flow control devices used for avoiding or delaying the separation of the boundary layer by bringing momentum from the higher layers of the fluid towards the surface. The Vortex generator usually has the same height as the local boundary layer thickness, and these Vortex generators can produce overload drag in some cases. The aim of the present study was to analyze the characteristics and path of the primary vortex produced by a single rectangular vortex generator on a flat plate for the incident angles of β = 10 ∘ , 15 ∘ , 18 ∘ and 20 ∘ . A parametric study of the induced vortex was performed for six VG heights using Reynolds average Navier–Stokes equations at Reynodls number R e = 27,000 based on the local boundary layer thickness, using computational fluid dynamics techniques with OpenFOAM open-source code. In order to determine the vortex size, the so-called half-life radius was computed and compared with experimental data. The results showed a similar trend for all the studied vortex generator heights and incident angles with small variations for the vertical and the lateral paths. Additionally, 0.4H and 0.6H VG heights at incident angles of β = 18 ∘ and β = 20 ∘ showed the best performance in terms of vortex strength and generation of wall shear stress.

Review: Effects of Inlet Conditions on Conical-Diffuser Performance

1981 ◽  
Vol 103 (2) ◽  
pp. 250-257 ◽  
Author(s):  
A. Klein
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Experimental Evidence ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Shape Parameter ◽  
Conical Diffuser ◽  
Free Discharge ◽  
Inlet Conditions ◽  
Different Sources

The available experimental evidence of the effects of inlet conditions on the performance of conical diffusers with a free discharge is reviewed. The effects of inlet boundary layer thickness blockage, inlet shape parameter, turbulence, and Reynolds number are discussed. It is shown that many of the inconsistencies between different sources of data are the result of nonturbulent approach flows. Graphs are presented as guidelines for diffuser design.

Numerical Investigation on Boundary Layer Flow Control with Vortex Generators

2013 ◽  
Vol 432 ◽  
pp. 351-357
Author(s):  
Guang Yuan Liu ◽  
Rui Bo Wang ◽  
Chang Rong Zhang ◽  
Feng Chen ◽  
Jiang Yu Xie ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Side Wall ◽  
Vortex Generator ◽  
Simulation Method ◽  
Vortex Generators ◽  
Layer Flow ◽  
Transonic Wind Tunnel

The numerical simulation method was adopted to analyze the effect on boundary layer thickness reduction of various vortex generator parameters. Results show that vortex generators are capable of reducing boundary layer thickness for about 66 percent, and the influence on centerline Mach number distributions is neglectable. Practicable vortex generators for 2.4m transonic wind tunnel half-model test section side wall are founded. Research results can be used for further applications of vortex generator in wind tunnel tests.

The Influence of Tabs on Different Area Ratio Short Annular Diffusers

2014 ◽  
Author(s):  
D. J. Cerantola ◽  
A. M. Birk
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Pressure Coefficient ◽  
Area Ratio ◽  
Back Pressure ◽  
Swirl Number ◽  
Inlet Flow ◽  
Flow Blockage

Square tabs were placed on the base of an ellipsoidal centre body in annular diffusers with length to inlet height of 12. Tests were completed with an inlet Reynolds number of 1 × 105, swirl number of 0.71, and inlet flow blockage of 0.02–0.04. Four outer walls were manufactured with area ratios of 1.61, 1.91, 2.73, and 6.18. The tabs with a projected height equivalent to the boundary layer thickness were effective at reducing the outlet distortion but at a pressure penalty for the three smaller diffusers. The largest diffuser improved back pressure coefficient 4.6% with four tabs providing a blockage of 4.7% over its bare diffuser but was 42% lower than that obtained by the AR = 2.73 diffuser with no tabs.

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