The Effects of Reynolds Number on the Efficiency of Centrifugal Compressor Stages

1985 ◽  
Vol 107 (2) ◽  
pp. 541-548 ◽  
Author(s):  
M. V. Casey
Keyword(s):  
Reynolds Number ◽  
Centrifugal Compressor ◽  
Width Ratio ◽  
Empirical Methods ◽  
Empirical Coefficient ◽  
Impeller Outlet ◽  
Wide Range ◽  
Reynolds Number Effects ◽  
Work Input ◽  
New Form

An analysis of the friction losses in a centrifugal compressor stage is used to suggest a new form of correction equation for the effect of Reynolds number on efficiency. This equation relates the effect of Reynolds number to the surface roughness, the impeller outlet width ratio and the work input coefficient. Systematic tests on a wide range of compressor stages are used to calibrate the single empirical coefficient in the equation. Despite its simplicity this equation provides more accurate predictions of the Reynolds number effects than existing empirical methods.

A New Appraisal of Reynolds Number Effects on Centrifugal Compressor Performance

1979 ◽  
Vol 101 (3) ◽  
pp. 384-392 ◽  
Author(s):  
F. J. Wiesner
Keyword(s):  
Reynolds Number ◽  
Centrifugal Compressor ◽  
Performance Test ◽  
Flow Coefficient ◽  
Performance Parameters ◽  
Empirical Methods ◽  
Reynolds Number Effects ◽  
Significant Performance ◽  
Compressor Performance ◽  
Overall Performance

This paper summarizes the results of an investigation into the effects of Reynolds number on the performance of centrifugal compressor stages, using a computer program for the detailed prediction of component and overall performance characteristics. This investigation included wide variation of stage geometries, speeds, and fluid conditions, resulting in diffuser inlet absolute Reynolds number variations over the range from 5 × 102 to 5 × 108. The computer results indicate that variations in Reynolds number and in relative roughness will produce variations in all significant performance parameters: the flow coefficient, the work coefficient, and the efficiency. Correlations of these results with various sources of test data on single and multistage centrifugal compressors produce very satisfactory comparisons. As a result of this study, improved empirical methods are recommended for making practical adjustments of compressor performance with variation in Reynolds number. These recommendations should be taken into account in the modernization of all centrifugal compressor performance test codes such as those formulated by ASME and ISO.

Modeling Reynolds-Number Effects in Wall-Bounded Turbulent Flows

1996 ◽  
Vol 118 (2) ◽  
pp. 260-267 ◽  
Author(s):  
R. M. C. So ◽  
H. Aksoy ◽  
S. P. Yuan ◽  
T. P. Sommer
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Reynolds Stress ◽  
Strain Tensor ◽  
Reynolds Numbers ◽  
Turbulence Statistics ◽  
Wide Range ◽  
Peak Shear Stress ◽  
Reynolds Number Effects ◽  
Near Wall

Recent experimental and direct numerical simulation data of two-dimensional, isothermal wall-bounded incompressible turbulent flows indicate that Reynolds-number effects are not only present in the outer layer but are also quite noticeable in the inner layer. The effects are most apparent when the turbulence statistics are plotted in terms of inner variables. With recent advances made in Reynolds-stress and near-wall modeling, a near-wall Reynolds-stress closure based on a recently proposed quasi-linear model for the pressure strain tensor is used to analyse wall-bounded flows over a wide range of Reynolds numbers. The Reynolds number varies from a low of 180, based on the friction velocity and pipe radius/channel half-width, to 15406, based on momentum thickness and free stream velocity. In all the flow cases examined, the model replicates the turbulence statistics, including the Reynolds-number effects observed in the inner and outer layers, quite well. Furthermore, the model reproduces the correlation proposed for the location of the peak shear stress and an appropriately defined Reynolds number, and the variations of the near-wall asymptotes with Reynolds numbers. It is conjectured that the ability of the model to replicate the asymptotic behavior of the near-wall flow is most responsible for the correct prediction of the Reynolds-number effects.

scholarly journals Experimental study of low Reynolds number effects on aerodynamics of smooth and sinusoidal leading-edge wings in the vicinity of the ground

2021 ◽  
Vol 15 (2) ◽  
pp. 8205-8218
Author(s):  
A. A. Mehraban ◽  
Mohammad Hassan Djavareshkian
Keyword(s):  
Reynolds Number ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Ground Clearance ◽  
Wide Range ◽  
Reynolds Number Effects ◽  
Low Reynolds ◽  
Stall Angle

Present study experimentally investigates the effects of ground clearance and Reynolds number on aerodynamic coefficients of smooth and sinusoidal leading-edge wings. Wind tunnel tests are conducted over a wide range of angles of attack from zero to 36 degrees, low Reynolds numbers of 30,000, 45,000 and 60,000, and also ground clearances of 0.5, 1 and ∞. Results showed that reduction of ground clearance and increment of Reynolds number cause the lift coefficient and the lift to drag ratio of both wings to be enhanced. Furthermore, the effects of Reynolds number and ground clearance on the smooth leading-edge wing are more than the sinusoidal leading-edge one. In addition, the sinusoidal leading-edge wing shows an excellent performance in the poststall region due to producing a higher lift and also by delaying the stall angle compared to the smooth leading-edge wing.

Radial Distributions of Temporal-Mean Peripheral Velocity and Pressure for Fully Developed Turbulent Flow in Curved Channels

1960 ◽  
Vol 82 (3) ◽  
pp. 528-536 ◽  
Author(s):  
A. W. Marris
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Rectangular Cross Section ◽  
Width Ratio ◽  
Curved Channels ◽  
Peripheral Velocity ◽  
Wide Range ◽  
Fully Developed Turbulent Flow ◽  
The Mean ◽  
Moving Fluid

Experimental results are presented for the radial distributions of pressure and peripheral velocity for the turbulent flow of water in two closed curved channels of rectangular cross section and large depth-to-width ratio. The traverses were taken at the equatorial section of the channel and sufficiently far around the curve for the effect of curvature on the mean motion to be fully established. The two channels employed had widely differing mean-radius-to-width ratios n. The data obtained for a wide range of flow rates in the channel with a larger n indicated that Reynolds similarity existed between the flows in this channel. These data are compared with the pressure and velocity profiles predicted by potential flow theory and with a semiempirical logarithmic velocity distribution. Results obtained for the channel with smaller n showed that at above a certain Reynolds number an anomaly occurred in the flow, manifesting itself as an unstable “belt” of faster moving fluid, which moved outward from the inner wall as the Reynolds number was increased. This effect, considered to be the consequence of upstream stall, was accompanied by an adverse longitudinal-pressure gradient at the inner wall of the channel. It appeared to be eliminated by the insertion of an upstream splitter vane.

PIV Investigation of Reynolds Number Effects on a Closed Channel Flow Over a Smooth Forward Facing Step

2014 ◽  
Author(s):  
Ebenezer E. Essel ◽  
Eric W. Thacher ◽  
Mark F. Tachie
Keyword(s):  
Reynolds Number ◽  
Reynolds Shear Stress ◽  
Step Height ◽  
Recirculation Region ◽  
Reattachment Length ◽  
Particle Image Velocimetry Technique ◽  
Freestream Velocity ◽  
Wide Range ◽  
Reynolds Number Effects ◽  
Forward Facing Step

This paper presents an experimental investigation of Reynolds number effects on the characteristics of separated and reattached flow over a smooth forward facing step. Particle image velocimetry technique was used to conduct detailed velocity measurement for a wide range of Reynolds numbers based on the step height and freestream velocity, 2040≤Reh≤8750. For each test case, the aspect ratio, AR = 21, ratio of boundary layer to step height, δ/h = 2.6 ± 0.2 and freestream turbulence level of 4% were kept constant. The results showed that the reattachment length increased monotonically with increasing Reynolds number for Reh < 6000, beyond which the reattachment length was independent of Reynolds number. In the recirculation region on top of the step, the Reynolds normal stresses were independent of Reynolds number but a higher Reynolds number increased the Reynolds shear stress in the region adjacent to the top of the step.

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