Deterministic Blade Row Interactions in a Centrifugal Compressor Stage

1992 ◽  
Vol 114 (2) ◽  
pp. 304-311 ◽  
Author(s):  
K. R. Kirtley ◽  
T. A. Beach
Keyword(s):  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Pressure Side ◽  
Compressor Stage ◽  
Trailing Edge ◽  
Tip Leakage ◽  
Centrifugal Compressor Stage ◽  
Blade Row

The three-dimensional viscous flow in a low-speed centrifugal compressor stage is simulated using an average passage Navier–Stokes analysis. The impeller discharge flow is of the jet/wake type with low-momentum fluid in the shroud-pressure side corner coincident with the tip leakage vortex. This nonuniformity introduces periodic unsteadiness in the vane frame of reference. The effect of such deterministic unsteadiness on the time mean is included in the analysis through the average passage stress, which allows the analysis of blade row interactions. The magnitude of the divergence of the deterministic unsteady stress is of the order of the divergence of the Reynolds stress over most of the span from the impeller trailing edge to the vane throat. Although the potential effects on the blade trailing edge from the diffuser vane are small, strong secondary flows generated by the impeller degrade the performance of the diffuser vanes.

scholarly journals Deterministic Blade Row Interactions in a Centrifugal Compressor Stage

1991 ◽  
Author(s):  
K. R. Kirtley ◽  
T. A. Beach
Keyword(s):  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Pressure Side ◽  
Compressor Stage ◽  
Trailing Edge ◽  
Tip Leakage ◽  
Centrifugal Compressor Stage ◽  
Blade Row

The three-dimensional viscous flow in a low speed centrifugal compressor stage is simulated using an average passage Navier-Stokes analysis. The impeller discharge flow is of the jet/wake type with low momentum fluid in the shroud-pressure side corner coincident with the tip leakage vortex. This nonuniformity introduces periodic unsteadiness in the vane frame of reference. The effect of such deterministic unsteadiness on the time-mean is included in the analysis through the average passage stress, which allows the analysis of blade row interactions. The magnitude of the divergence of the deterministic unsteady stress is of the order of the divergence of the Reynolds stress over most of the span, from the impeller trailing edge to the vane throat. Although the potential effects on the blade trailing edge from the diffuser vane are small, strong secondary flows generated by the impeller degrade the performance of the diffuser vanes.

Three-Dimensional Navier-Stokes Analysis of Turbine Rotor and Tip-Leakage Flowfield

1997 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The 3-D viscous flowfield in the rotor passage of a single-stage turbine, including the tip-leakage flow, is computed using a Navier-Stokes procedure. A grid-generation code has been developed to obtain embedded H grids inside the rotor tip gap. The blade tip geometry is accurately modeled without any “pinching”. Chien’s low-Reynolds-number k-ε model is employed for turbulence closure. Both the mean-flow and turbulence transport equations are integrated in time using a four-stage Runge-Kutta scheme. The computational results for the entire turbine rotor flow, particularly the tip-leakage flow and the secondary flows, are interpreted and compared with available data. The predictions for major features of the flowfield are found to be in good agreement with the data. Complicated interactions between the tip-clearance flows and the secondary flows are examined in detail. The effects of endwall rotation on the development and interaction of secondary and tip-leakage vortices are also analyzed.

Numerical Investigation of the Unsteady Flow Inside a Centrifugal Compressor Stage With Pipe Diffuser

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Daniel R. Grates ◽  
Peter Jeschke ◽  
Reinhard Niehuis
Keyword(s):  
Experimental Data ◽  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Measurement Techniques ◽  
Navier Stokes ◽  
Compressor Stage ◽  
Centrifugal Compressor Stage ◽  
Transonic Centrifugal Compressor ◽  
Computational Fluid Dynamics Cfd ◽  
The Subject

The subject of this paper is the investigation of unsteady flow inside a transonic centrifugal compressor stage with a pipe-diffuser by utilizing unsteady 3D Reynolds-averaged Navier–Stokes simulations (unsteady 3D URANS). The computational fluid dynamics (CFD) results obtained are compared with detailed experimental data gathered using various steady and unsteady measurement techniques. The basic phenomena and mechanisms of the complex and highly unsteady flow inside the compressor with a pipe-diffuser are presented and analyzed in detail.

Computations of bladerow stall inception in transonic flows

1999 ◽  
Vol 103 (1025) ◽  
pp. 317-324 ◽  
Author(s):  
L. He ◽  
J. O. Ismael
Keyword(s):  
Three Dimensional ◽  
Rotating Stall ◽  
Navier Stokes ◽  
Flow Conditions ◽  
Stall Inception ◽  
Tip Leakage ◽  
Blade Row ◽  
Inflow Condition ◽  
Shock Oscillation ◽  
Transonic Fan

Abstract A three-dimensional unsteady Navier-Stokes solver has been used to simulate stall inception in a single row ten passage segment of a transonic fan, the NASA rotor-67. At subsonic flow conditions, the 3D results illustrate a rotating stall inception with short scale part-span cells rotating at around 80% rotor speed, similar to that observed in some low speed experiments. However, at a supersonic relative inflow condition, the results show that an isolated blade row tends to stall in a one-dimensional breakdown pattern without first experiencing rotating stall. At near-stall conditions, significant self-excited unsteadiness is generated by the interaction between the tip-leakage vortex and the passage shock wave. Further computations for two-dimensional configurations indicate that it is possible to have a rotating pattern of instability in transonic blade rows associated with circumferential synchronised shock oscillation.

Identification of Acoustic Dipole Sources in a Propylene Centrifugal Compressor Stage

2010 ◽  
Author(s):  
Hongtao Tang ◽  
Datong Qi ◽  
Fuan Lu
Keyword(s):  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Dipole Source ◽  
Compressor Stage ◽  
Impeller Blade ◽  
Centrifugal Compressor Stage ◽  
Rotor Stator Interaction ◽  
Last Stage ◽  
Harmonic Components ◽  
Dipole Sources

Three-dimensional unsteady turbulent flow in a propylene centrifugal compressor stage was numerically studied in order to identify primary acoustic dipole sources. The investigated model is the last stage of a propylene compressor used in the megaton ethylene production. The leakage clearance between the impeller and diffuser was simplified and modeled to capture the rotor-stator interaction accurately. A series of sixth-order polynomials, the use of which significantly sped up the computation compared with directly using Helmholtz real gas equation as the gas model, were fitted with a relative error less than 0.03% based on the thermodynamic data of propylene obtained by the Helmholtz equation. According to Lowson’s equation, the root mean square of the partial derivative of static pressure with respect to time during two revolutions of the impeller was taken as the parameter to measure dipole source intensity. The spatial distribution and frequency characteristics of the dipole sources were also investigated intensively. As a result of the present study, the primary dipole source is located at the junction of the impeller and diffuser, and its intensity is dominated by the components at the impeller blade passing frequency (BPF) and its higher harmonics, which are induced by the strong rotor-stator interaction. The spectrum analysis downstream of the impeller indicates that the higher harmonic components of dipole sources attenuate faster than the BPF component along the streamwise direction, and it is the BPF that dominates the noise characteristic in the volute casing of the studied model.

scholarly journals Effect of the Unsteadiness on the Diffuser Flow in a Transonic Centrifugal Compressor Stage

2009 ◽  
Vol 2009 ◽  
pp. 1-11 ◽  
Author(s):  
N. Bulot ◽  
I. Trébinjac
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Centrifugal Compressor ◽  
Wake Flow ◽  
Pressure Waves ◽  
Pressure Side ◽  
Compressor Stage ◽  
Impeller Blade ◽  
Centrifugal Compressor Stage ◽  
Diffuser Flow

The study is focused on the analysis of the flow structure within the vaned diffuser of a transonic high-pressure centrifugal compressor stage. The analyzed time-dependent flow field comes from unsteady computations of the stage using a 3D Navier-Stokes code with a phase-lagged technique, at an operating point close to the design point. A good comparison with available experimental data allowed the use of CFD for investigating the details of the flow in order to assess the effect of the unsteadiness in the diffuser flow development. Applying various data processing techniques, it is shown that the unsteadiness is due to the jet and wake flow structure emerging from the radial impeller and to the pressure waves brought about by the interaction between the vane bow shock wave and the impeller blade. The interaction between the pressure waves and the vane pressure side boundary layer leads to a pulsating behavior of separated bubbles within the diffuser. The pressure waves are similar in shape and strength whatever the blade height. The observed change in the flow field from hub to tip is due to migration of the low momentum fluid contained in the wake toward the pressure side/hub corner.

Analysis of the flow in a transonic centrifugal compressor stage from choke to surge

2011 ◽  
Vol 225 (7) ◽  
pp. 919-929 ◽  
Author(s):  
I Trébinjac ◽  
N Bulot ◽  
N Buffaz
Keyword(s):  
Centrifugal Compressor ◽  
Suction Side ◽  
Bow Shock ◽  
Wake Flow ◽  
Pressure Waves ◽  
Pressure Side ◽  
Compressor Stage ◽  
Choked Flow ◽  
Centrifugal Compressor Stage ◽  
Transonic Centrifugal Compressor

Numerical and experimental investigations were conducted in a transonic centrifugal compressor stage composed of a backswept splittered unshrouded impeller and a vaned diffuser. Unsteady three-dimensional simulations were performed with the code elsA that solves the turbulent-averaged Navier–Stokes equations, at three operating points: choked flow, peak efficiency, and near surge. Numerical results were validated with experimental data coming from laser Doppler anemometry and unsteady pressure measurements. This article focuses on the change in flow structures when the operating point moves from choke to surge. The main changes in the impeller consist in an enlargement of the wake (of the jet-wake flow structure) and an increase in the exit time-averaged flow angle. Consequently, in the diffuser passage, the main flow trajectory moves towards the vane pressure side, and the boundary layer separation transfers from pressure side to suction side. The interaction between the vane bow shock wave and the impeller blade leads to pressure waves α+, which propagate in the diffuser passage. These pressure waves generate alternately opposite and favourable pressure gradients, which drive the boundary layers to periodic separation. From choke to surge, the intensity of the pressure waves α+ increases. The interaction also leads to subsonic pockets Г, which are torn out from the vane-leading edge bow shock and swept along the vane suction side. The induced change in the shock shape and location combined with the severe hub/suction side corner separation are thought to be at the origin of the surge inception.

scholarly journals Experimental Study of a 3D Wake Decay and Secondary Flows Behind a Rotor Blade Row of a Low Speed Compressor Stage

1996 ◽  
Author(s):  
A. S. Witkowski ◽  
T. J. Chmielniak ◽  
M. D. Strozik
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Secondary Flow ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Compressor Stage ◽  
Blade Row

Detailed measurements have been performed in a low pressure axial flow compressor stage to investigate the structure of the secondary flow field and the three-dimensional wake decay at different axial locations before and behind the rotor. The three dimensional flow field upstream and downstream of the rotor and on the centerline of the stator blade passage have been sampled periodically using a straight and a 90 degree triple-split fiber probe. Radial measurements at 39 radial stations were carried out at chosen axial positions in order to get the span-wise characteristics of the unsteady flow. Taking the experimental values of the unsteady flow velocities and turbulence properties, the effects of the rotor blade wake decay and secondary flow on the blade row spacing and stator passage flow at different operating conditions are discussed. For the normal operating point, the component of radial turbulent intensities in the leakage-flow mixing region is found to be much higher than the corresponding axial and tangential components. But for a higher value of the flow coefficient the relations are different.The results of the experiments show that triple-split fiber probes, straight and 90 degree measurements, combined with the ensemble average technique are a very useful method for the analysis of rotor flow in turbomachinery. Tip clearance vortex, secondary flow near the hub and radial flow in the wake, turbulent intensity and Reynolds stresses and also the decay of the rotor wakes can be obtained by this method.

Numerical study on the Effect of Interaction Vaned Diffuser with Impeller on the Performance of a Modified Centrifugal Compressor

2013 ◽  
Vol 30 (2) ◽  
pp. 113-121 ◽  
Author(s):  
L. H. Jawad ◽  
S. Abdullah ◽  
R. Zulkifli ◽  
W. M. F. W. Mahmood
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Internal Flow ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Centrifugal Compressor Stage ◽  
Compressor Impeller ◽  
Inlet Conditions

ABSTRACTThis paper is a numerical simulation that was made in the three-dimensional flow, carried out in a modified centrifugal compressor, having vaned diffuser stage, used as an auto-motive turbo charger. Moreover, the performance of the centrifugal compressor was dependent on the proper matching between compressor impeller and vaned diffuser, influencing significantly surge and the efficiency of centrifugal compressor stages. In addition, a modified compressor impeller, coupled with vane and vaneless diffuser, has been found to have similar internal flow patterns for both the vaneless and vaned diffuser design. The vaned diffuser effect has been paid particular attention in terms of better analysis where the diffuser was designed for high sub-sonic inlet conditions. Another aim of this research was to study and simulate the effect of vaned diffuser on the performance of a centrifugal compressor. The simulation was undertaken by using a commercial software, the so-called ANSYS CFX, to predict numerically the performance in terms of pressure ratio, poly tropic efficiency and mass flow rate for the centrifugal compressor stage. The results were generated from CFD and were analyzed for better understanding of the fluid flow through centrifugal compressor stage. Conclusively, it was observed that the effect of the vaned diffuser is to convert the kinetic energy into a high static pressure after analyzing the results of the simulation.

Detailed Performance Analysis of a Centrifugal Compressor Stage With Pipe Diffuser and Immerged Tandem Deswirler

2015 ◽  
Author(s):  
Johannes Schmidt ◽  
Philipp Schwarz ◽  
Benjamin Wilkosz ◽  
Peter Jeschke ◽  
Caitlin Smythe
Keyword(s):  
Centrifugal Compressor ◽  
Pipe Flow ◽  
Major Effect ◽  
Compressor Stage ◽  
Close Coupling ◽  
Centrifugal Compressor Stage ◽  
Surge Margin ◽  
Radial Extent ◽  
Blade Row ◽  
Inlet Geometry

Commonly, the pipe diffuser and deswirler are aerodynamically decoupled from each other to ensure better mixing of the inhomogeneous pipe flow before entering the deswirler and to prevent upstream effects of the deswirler bend and blading on the pipe diffuser. Close-coupling of these two components, however, can lead to a significantly lower radial extent of the stage, resulting in a decrease of stage weight and engine frontal area. The geometry investigated includes a centrifugal compressor stage with a compact diffusion system, including a pipe diffuser and tandem deswirler whose first blade row is immerged into the pipe diffuser. Stage and component performance of this compact configuration is compared to two different stage configurations with decoupled deswirlers. Performance maps and 1-D pressure build-up data show that the compact stage is able to reach efficiency and pressure build-up of the compared stages which contain the same impeller and same diffuser inlet geometry. The performance of one of the compared stages with significantly higher radial stage extent is even exceeded. However, a loss in surge margin of about 2% has been detected which seems to be the major problem in reducing stage size by close-coupling the deswirl system to the pipe diffuser, since this can have a major effect on the diffuser inlet pressure build-up.

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