scholarly journals Secondary Flow Mixing Losses in a Centrifugal Impeller

1982 ◽  
Author(s):  
M. W. Johnson ◽  
J. Moore
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Centrifugal Impeller ◽  
Cross Sectional ◽  
Flow Measurements ◽  
Layer Separation ◽  
Flow Mixing ◽  
Rotating Impeller

Detailed flow measurements made in a 1-m dia shrouded centrifugal impeller running at 500 rpm are presented. All 3 mutually perpendicular components of relative velocity and rotary stagnation pressures were measured on 5 cross-sectional planes between the inlet and the outlet, using probes which were traversed within the rotating impeller passage. The reduced static pressures were also calculated from these flow measurements. The measurements were made for an impeller flow rate corresponding to approximately zero incidence at the blade leading edges. Shroud boundary layer separation and secondary flow were observed to lead to the formation of a wake in the suction-side/shroud corner region. It is concluded that the turbulent mixing associated with the shroud boundary layer separation and the strength of the secondary flow strongly influence the size and location of the wake respectively.

Secondary Flow Mixing Losses in a Centrifugal Impeller

1983 ◽  
Vol 105 (1) ◽  
pp. 24-32 ◽  
Author(s):  
M. W. Johnson ◽  
J. Moore
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Centrifugal Impeller ◽  
Cross Sectional ◽  
Flow Measurements ◽  
Layer Separation ◽  
Flow Mixing ◽  
Rotating Impeller

Detailed flow measurements made in a 1-m dia shrouded centrifugal impeller running at 500 rpm are presented. All three mutually perpendicular components of relative velocity and rotary stagnation pressures were measured on five cross-sectional planes between the inlet and the outlet, using probes which were traversed within the rotating impeller passage. The reduced static pressures were also calculated from these flow measurements. The measurements were made for an impeller flow rate corresponding to approximately zero incidence at the blade leading edges. Shroud boundary layer separation and secondary flow were observed to lead to the formation of a wake in the suction-side/shroud corner region. It is concluded that the turbulent mixing associated with the shroud boundary layer separation and the strength of the secondary flow strongly influence the size and location of the wake, respectively.

The Development of Wake Flow in a Centrifugal Impeller

1980 ◽  
Vol 102 (2) ◽  
pp. 382-389 ◽  
Author(s):  
M. W. Johnson ◽  
J. Moore
Keyword(s):  
Three Dimensional ◽  
Suction Side ◽  
Secondary Flows ◽  
Wake Flow ◽  
Centrifugal Impeller ◽  
Three Dimensional Flow ◽  
Cross Sectional ◽  
Flow Measurements ◽  
Compressor Impeller ◽  
Rotating Impeller

Three-dimensional flow, leading to the formation and the growth of a wake in a centrifugal impeller, has been studied. Results of flow measurements in a 1 m dia, shrouded, centrifugal compressor impeller running at 500 rpm are presented. Relative velocities and rotary stagnation pressures (p* = p + 1/2ρW2 − 1/2ρω2r2) were measured, on five cross-sectional planes between the inlet and outlet of the impeller, using pressure probes which were traversed within the rotating impeller passage. Particular attention was given to the convection of low p* fluid by secondary flows and to the formation of the wake in the shroud/suction-side corner region of the passage.

Design of a Low Solidity Flow-Controlled Stator With Coanda Surface in a High Speed Compressor

2008 ◽  
Author(s):  
Y. Guendogdu ◽  
A. Vorreiter ◽  
J. R. Seume
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
High Speed ◽  
Design Method ◽  
Active Flow Control ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Synthetic Jets ◽  
Layer Separation ◽  
Active Flow

Aerofoil active flow control has been attempted to increase the permissible loading of boundary layers in gas turbine components. Steady suction and blowing, pulsing and synthetic jets are all means to remove low energy flow, replace momentum deficits, or promote mixing to inhibit boundary layer separation. A curved surface near the trailing edge (“Coanda surface”) is another technique used to control aerofoil boundary layer separation. This paper presents the design of a stator with active flow control for a high speed compressor using a Coanda surface. The Coanda surface is located behind an injection slot on the aerofoil suction side of the first stage of a four-stage high speed research compressor. The design method and the present results are based on steady numerical calculations. The design intent is to reduce the number of vanes. This active flow control is used to maintain the flow exit angle of the reference stator despite the resulting increase in stator loading. It is shown that the solidity of the flow-controlled stator can be decreased by 25% with a blowing rate of 0.5% of the main mass flow.

An Investigation of the Flow Physics of Vane Clocking Using Unsteady Flow Measurements

2008 ◽  
Author(s):  
Nicole L. Key ◽  
Patrick B. Lawless ◽  
Sanford Fleeter
Keyword(s):  
Boundary Layer ◽  
Unsteady Flow ◽  
Leading Edge ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Flow Measurements ◽  
Rotor Wake ◽  
Efficiency Condition ◽  
Vane Clocking ◽  
Stage Efficiency

Vane clocking, the circumferential indexing of adjacent vane rows with similar vane counts, has been shown to affect stage efficiency in compressors and turbines. Steady flow measurements acquired in the embedded stage of the Purdue 3-Stage Compressor showed a change in stage efficiency with vane clocking, as discussed in a companion paper. The optimum efficiency condition at design loading occurred when the upstream vane wake impinged on the downstream vane, as had been reported by other vane clocking studies. However, at high loading, the impingement of the upstream vane wake triggered a vane suction side boundary layer separation and resulted in the worst efficiency condition. The objective of this research is to experimentally investigate the maximum and minimum efficiency clocking configurations with unsteady flow measurements to illuminate the flow physics associated with the measured changes in Stage 2 performance. Vane exit unsteady total pressure, velocity, and flow angle measurements were acquired at 50 pitchwise locations spanning one vane passage. Fourier decomposition is used to identify the impact of the upstream rotor wake on the shedding characteristics of the Stator 2 boundary layer and how the placement of the upstream vane wake affects this phenomenon. For the clocking configuration that located the Stator 1 wake at the leading edge of the Stator 2 vane at design loading, it dampened the boundary layer response to the fluctuating incidence associated with rotor wake chopping, leading to a reduction in the size of the structures shed in the Stator 2 vane wake. At the high loading condition, the placement of the Stator 1 wake at the leading edge of Stator 2 triggered a suction side boundary layer separation, resulting in an absence of the upstream rotor blade pass frequency in the spectrum measured in the Stator 2 wake.

scholarly journals The Effect of Backswept Blading on the Flow in a Centrifugal Compressor Impeller

1990 ◽  
Author(s):  
Talib Z. Farge ◽  
Mark W. Johnson
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Centrifugal Compressor ◽  
Boundary Layer Separation ◽  
Flow Fields ◽  
Similar Position ◽  
Layer Separation ◽  
Flow Generation ◽  
Compressor Impeller ◽  
Exit Analysis

A comparison is made between the flow in two impellers, one with radially ending blades and one with blades backswept by 30°. The two impellers have identical inducers. Measurements are made of the three velocity components and total pressures across five measurement stations within each impeller. The flow in the backswept impeller is dominated by a counter-clockwise vortex which reduces the severity of the shroud boundary layer separation and hence leads to a higher impeller efficiency. The wake is consequently smaller in the backswept impeller but adopts a similar position on the shroud surface at the impeller exit. Analysis of the secondary flow generation reveals the mechanisms responsible for the differences in the flow fields in the two impellers.

The boundary layer separation from streamlined surfaces and new ways of its prevention in diffusers

2017 ◽  
Author(s):  
Arkady Zaryankin ◽  
Andrey Rogalev ◽  
Ivan Komarov ◽  
V. Kindra ◽  
S. Osipov
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Separation ◽  
Layer Separation

scholarly journals Leading Edge Blowing to Mimic and Enhance the Serration Effects for Aerofoil

2021 ◽  
Vol 11 (6) ◽  
pp. 2593
Author(s):  
Yasir Al-Okbi ◽  
Tze Pei Chong ◽  
Oksana Stalnov
Keyword(s):  
Boundary Layer ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Boundary Layer Separation ◽  
Shear Instability ◽  
Vortical Flow ◽  
High Angle ◽  
High Angle Of Attack ◽  
Layer Separation ◽  
Aerodynamic Performances

Leading edge serration is now a well-established and effective passive control device for the reduction of turbulence–leading edge interaction noise, and for the suppression of boundary layer separation at high angle of attack. It is envisaged that leading edge blowing could produce the same mechanisms as those produced by a serrated leading edge to enhance the aeroacoustics and aerodynamic performances of aerofoil. Aeroacoustically, injection of mass airflow from the leading edge (against the incoming turbulent flow) can be an effective mechanism to decrease the turbulence intensity, and/or alter the stagnation point. According to classical theory on the aerofoil leading edge noise, there is a potential for the leading edge blowing to reduce the level of turbulence–leading edge interaction noise radiation. Aerodynamically, after the mixing between the injected air and the incoming flow, a shear instability is likely to be triggered owing to the different flow directions. The resulting vortical flow will then propagate along the main flow direction across the aerofoil surface. These vortical flows generated indirectly owing to the leading edge blowing could also be effective to mitigate boundary layer separation at high angle of attack. The objectives of this paper are to validate these hypotheses, and combine the serration and blowing together on the leading edge to harvest further improvement on the aeroacoustics and aerodynamic performances. Results presented in this paper strongly indicate that leading edge blowing, which is an active flow control method, can indeed mimic and even enhance the bio-inspired leading edge serration effectively.

On turbulent boundary-layer separation

1968 ◽  
Vol 32 (2) ◽  
pp. 293-304 ◽  
Author(s):  
V. A. Sandborn ◽  
C. Y. Liu
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Turbulent Boundary Layer ◽  
Analytical Study ◽  
Boundary Layer Separation ◽  
Mean Velocity ◽  
Laminar Separation ◽  
Layer Separation ◽  
Turbulent Separation ◽  
Separation Model

An experimental and analytical study of the separation of a turbulent boundary layer is reported. The turbulent boundary-layer separation model proposed by Sandborn & Kline (1961) is demonstrated to predict the experimental results. Two distinct turbulent separation regions, an intermittent and a steady separation, with correspondingly different velocity distributions are confirmed. The true zero wall shear stress turbulent separation point is determined by electronic means. The associated mean velocity profile is shown to belong to the same family of profiles as found for laminar separation. The velocity distribution at the point of reattachment of a turbulent boundary layer behind a step is also shown to belong to the laminar separation family.Prediction of the location of steady turbulent boundary-layer separation is made using the technique employed by Stratford (1959) for intermittent separation.

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