Bowed Stators: An Example of CFD Applied to Improve Multistage Compressor Efficiency

1997 ◽  
Vol 119 (2) ◽  
pp. 161-168 ◽  
Author(s):  
H. D. Weingold ◽  
R. J. Neubert ◽  
R. F. Behlke ◽  
G. E. Potter
Keyword(s):  
Experimental Testing ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Substantial Improvement ◽  
Navier Stokes ◽  
Suction Surface ◽  
Stator Core ◽  
Corner Separation ◽  
Entire Flow ◽  
Multistage Compressor

Analysis of multistage compressor stator surface static pressure data reveals that the radial growth of suction surface corner separation prematurely separates core flow stator sections, limiting their pressure rise capability and generating endwall loss. Modeling of the stator flowfield, using a three-dimensional Euler analysis, has led to the development of “bowed” stator shapes, which generate radial forces that reduce diffusion rates in the suction surface corners, in order to delay the onset of corner separation. Experimental testing of the bowed stator concept in a three-stage research compressor has confirmed the elimination of suction surface corner separation, the resulting reduction of the endwall loss, and the increase in pressure rise capability of the stator core sections. This results in more robust pressure rise characteristics and substantially improved efficiency over the entire flow range of the compressor. The strong interaction effects of the bowed stator with the viscous endwall flowfield are shown to be predictable using a three-dimensional multistage Navier–Stokes analysis. This permits matching of the rotors to the altered stator exit profiles, in order to avoid potential stability limiting interactions. Application of bowed stators to a high bypass ratio engine eleven-stage high-pressure compressor has resulted in substantial improvement in efficiency, with no stability penalty.

Reduction of Compressor Stator Endwall Losses Through the Use of Bowed Stators

1995 ◽  
Author(s):  
Harris D. Weingold ◽  
Robert J. Neubert ◽  
Roy F. Behlke ◽  
Glen E. Potter
Keyword(s):  
Experimental Testing ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Cfd Modeling ◽  
Incident Flow ◽  
Suction Surface ◽  
Stator Core ◽  
Corner Separation ◽  
Entire Flow ◽  
Multistage Compressor

The growth of suction surface corner separation in multistage compressor stators is shown to limit the pressure rise capability of core flow stator sections, which would otherwise remain unseparated at the same incident flow. Three dimensional CFD modeling of the stator flowfield has led to the development of “bowed” stator shapes which are predicted to substantially delay the onset of suction surface corner separation. Experimental testing of the bowed stator concept in the exit stator of a three–stage research compressor has confirmed the elimination of suction surface corer separation, the resulting reduction of the endwall loss, and the increase in pressure rise capability of the stator core sections due to the elimination of the radial growth of the corner separation region. Application of bowed stators in all three stator rows of the research compressor has provided more robust characteristics and substantially improved efficiency over the entire flow range.

Numerical Simulation of Clocking Effect on Wake Transportation and Interaction in a 1.5-Stage Axial Turbine

2010 ◽  
Author(s):  
Wei Li ◽  
Hua Ouyang ◽  
Zhao-hui Du
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Leading Edge ◽  
Navier Stokes ◽  
Maximum Efficiency ◽  
Suction Surface ◽  
Navier Stokes Equations ◽  
Pressure Surface ◽  
Turbine Efficiency ◽  
Small Influence

To give insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has a very small influence on the turbine efficiency in this investigation. The efficiency difference between the maximum and minimum configuration is nearly 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passed through the mid-channel in the 2nd stator.

scholarly journals Three-Dimensional Boundary Layer on a Compressor Rotor Blade at Peak Pressure Rise Coefficient

1986 ◽  
Author(s):  
B. Lakshminarayana ◽  
P. Popovski
Keyword(s):  
Boundary Layer ◽  
Rotor Blade ◽  
Peak Pressure ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Layer Growth ◽  
Leakage Flow ◽  
Suction Surface ◽  
Compressor Rotor

A comprehensive study of the three-dimensional turbulent boundary layer on a compressor rotor blade at peak pressure rise coefficient is reported in this paper. The measurements were carried out at various chordwise and radial locations on a compressor rotor blade using a rotating miniature “V” configuration hot-wire probe. The data are compared with the measurement at the design condition. Substantial changes in the blade boundary layer characteristics are observed, especially in the outer sixteen percent of the blade span. The increased chordwise pressure gradient and the leakage flow at the peak pressure coefficient have a cumulative effect in increasing the boundary layer growth on the suction surface. The leakage flow has a beneficial effect on the pressure surface. The momentum and boundary layer thicknesses increase substantially from those at the design condition, especially near the outer radii of the suction surface.

Hydrodynamic Design of Pump Diffuser Using Inverse Design Method and CFD

2002 ◽  
Vol 124 (2) ◽  
pp. 319-328 ◽  
Author(s):  
Akira Goto ◽  
Mehrdad Zangeneh
Keyword(s):  
Design Method ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Inverse Design ◽  
Navier Stokes ◽  
Outer Diameter ◽  
Large Area ◽  
Suction Surface ◽  
Pump Stage ◽  
Inverse Design Method

A new approach to optimizing a pump diffuser is presented, based on a three-dimensional inverse design method and a Computational Fluid Dynamics (CFD) technique. The blade shape of the diffuser was designed for a specified distribution of circulation and a given meridional geometry at a low specific speed of 0.109 (non-dimensional) or 280 (m3/min, m, rpm). To optimize the three-dimensional pressure fields and the secondary flow behavior inside the flow passage, the diffuser blade was more fore-loaded at the hub side as compared with the casing side. Numerical calculations, using a stage version of Dawes three-dimensional Navier-Stokes code, showed that such a loading distribution can suppress flow separation at the corner region between the hub and the blade suction surface, which was commonly observed with conventional designs having a compact bowl size (small outer diameter). The improvements in stage efficiency were confirmed experimentally over the corresponding conventional pump stage. The application of multi-color oil-film flow visualization confirmed that the large area of the corner separation was completely eliminated in the inverse design diffuser.

Location Effect of Boundary Layer Suction on Compressor Hub-Corner Separation

2014 ◽  
Author(s):  
Ping-Ping Chen ◽  
Wei-Yang Qiao ◽  
Karsten Liesner ◽  
Robert Meyer
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Three Dimensional ◽  
Base Flow ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Corner Separation ◽  
Boundary Layer Suction

The large secondary flow area in the compressor hub-corner region usually leads to three-dimensional separation in the passage with large amounts of total pressure loss. In this paper numerical simulations of a linear high-speed compressor cascade, consisting of five NACA 65-K48 stator profiles, were performed to analyze the flow mechanism of hub-corner separation for the base flow. Experimental validation is used to verify the numerical results. Active control of the hub-corner separation was investigated by using boundary layer suction. The influence of the selected locations of the endwall suction slot was investigated in an effort to quantify the gains of the compressor cascade performance. The results show that the optimal chordwise location should contain the development section of the three-dimensional corner separation downstream of the 3D corner separation onset. The best pitchwise location should be close enough to the vanes’ suction surface. Therefore the optimal endwall suction location is the MTE slot, the one from 50% to 75% chord at the hub, close to the blade suction surface. By use of the MTE slot with 1% suction flow ratio, the total-pressure loss is substantially decreased by about 15.2% in the CFD calculations and 9.7% in the measurement at the design operating condition.

Numerical Flow Analysis in a Subsonic Vaned Radial Diffuser With Leading Edge Redesign

1999 ◽  
Vol 121 (1) ◽  
pp. 119-126 ◽  
Author(s):  
E. Casartelli ◽  
A. P. Saxer ◽  
G. Gyarmathy
Keyword(s):  
Static Pressure ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Leading Edge ◽  
Inverse Design ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Characteristic Lines ◽  
Design Software

The flow field in a subsonic vaned radial diffuser of a single-stage centrifugal compressor is numerically investigated using a three-dimensional Navier–Stokes solver (TASCflow) and a two-dimensional analysis and inverse-design software package (MISES). The vane geometry is modified in the leading edge area (two-dimensional blade shaping) using MISES, without changing the diffuser throughflow characteristics. An analysis of the two-dimensional and three-dimensional effects of two redesigns on the flow in each of the diffuser subcomponents is performed in terms of static pressure recovery, total pressure loss production, and secondary flow reduction. The computed characteristic lines are compared with measurements, which confirm the improvement obtained by the leading edge redesign in terms of increased pressure rise and operating range.

scholarly journals Effects of Stator Pressure Field on Upstream Rotor Performance

1999 ◽  
Author(s):  
M. B. Graf ◽  
E. M. Greitzer ◽  
F. E. Marble ◽  
O. P. Sharma
Keyword(s):  
Steady Flow ◽  
Pressure Field ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Flow Models ◽  
High Pressure Compressor ◽  
Rotor Stator Interaction ◽  
Rotor Loss

Effects of stator pressure field on upstream rotor performance in a high pressure compressor stage have been assessed using three-dimensional steady and time-accurate Reynolds-averaged Navier-Stokes computations. Emphasis was placed on: (1) determining the dominant features of the flow arising from interaction of the rotor with the stator pressure field, and (2) quantifying the overall effects on time averaged loss, blockage, and pressure rise. The time averaged results showed a 20 to 40% increase in overall rotor loss and a 10 to 50% decrease in tip clearance loss compared to an isolated rotor. The differences were dependent on the operating point and increased as the stage pressure rise, and amplitude of the unsteady back pressure variations, was increased. Motions of the tip leakage vortex on the order of the blade pitch were observed at the rotor exit in all the unsteady flow simulations; these were associated with enhanced mixing in the region. The period of the motion scaled with rotor flow-through time rather than stator passing. Three steady flow approximations for the rotor-stator interaction were assessed with reference to the unsteady computations: an axisymmetric representation of the stator pressure field, an inter-blade row averaging plane method, and a technique incorporating deterministic stresses and bodyforces associated with stator flow field. Differences between steady and unsteady predictions of overall rotor loss, tip region loss, and endwall blockage ranged from 5 to 50% of the time average, but the steady flow models gave overall rotor pressure rise and flow capacity within 5% of the time averaged values.

Three-Dimensional Viscous Flutter Analysis of Standard Configuration 10

2007 ◽  
Author(s):  
Paul J. Petrie-Repar ◽  
Andrew McGhee ◽  
Peter A. Jacobs
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Design Flow ◽  
Suction Surface ◽  
Corner Separation ◽  
Aerodynamic Damping ◽  
Flutter Analysis ◽  
Standard Configuration ◽  
Phase Angles ◽  
2D And 3D

The results of a three-dimensional (3D) viscous flutter analysis for a compressor stage, Standard Configuration 10, are presented. The unsteady flow simulations were performed by a 3D linearized Navier-Stokes flow solver using the Spalart and Allmaras turbulence model. Significant flow blockage due to corner separation at the hub on the suction surface was predicted by the steady-state 3D viscous simulation at a design condition. Corner separation was not predicted by 3D inviscid or two-dimensional (2D) viscous simulations. The corner separation was found to have a destabilizing effect and changed the nature of the unsteady flow. In fact, the 3D viscous simulations predicted negative aerodynamic damping for almost half of the inter-blade phase angles, while the 2D and 3D inviscid simulations predicted stable positive aerodynamic damping for all inter-blade phase angles. An off-design flow condition was also examined and significant differences between the 2D and 3D viscous simulations were found.

Evaluation of Compressor Blading With Blade End Slots and Full-Span Slots in a Highly Loaded Compressor Cascade

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Yumeng Tang ◽  
Yangwei Liu ◽  
Lipeng Lu
Keyword(s):  
Incidence Angle ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Main Flow ◽  
The Self ◽  
Flow Structures ◽  
Compressor Cascade ◽  
Corner Separation ◽  
High Incidence ◽  
Highly Loaded

Abstract Blade end slots were proposed to control corner separation in a highly loaded compressor cascade in our previous studies. This study focuses on the evaluation of compressor blading with blade end slots and full-span slots. First, the two-dimensional configuration performance is evaluated both for the datum and slotted profiles. The slotted configuration could effectively suppress separation, especially under positive incidence conditions when the separation is large. Thus, two three-dimensional blading with full-span slots and blade end slots (20% span height from the endwall) are compared. Results show that blading with full-span slots could effectively reduce the loss and enlarge pressure rise under relative high incidence angles, while blading with blade end slots could effectively reduce the loss and enlarge pressure rise above an incidence angle of −4 deg. Blading with slots alters the flow structures and reorganizes the flow in the blade end regions. The self-adaptive jets from the slots reenergize the low-momentum flow downstream and restrain its migration toward the mid-span, so that the corner separation is reduced and the performance is enhanced. The loss for the end slotted blade is lower than that of the full-span slotted blade under incidence angles within 4 deg. This is because the additional mixing loss of the jet and the main flow are caused by the full-span slots at the mid-span regions where the flow remains attached for the blade end slots.

Aeroelastic Instability in Transonic Fans

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Mehdi Vahdati ◽  
Nick Cumpsty
Keyword(s):  
Mass Flow ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Leading Edge ◽  
Operating Conditions ◽  
Mean Flow ◽  
Suction Surface ◽  
Blade Vibration ◽  
Stall Flutter ◽  
Fan Blade

This paper describes stall flutter, which can occur at part speed operating conditions near the stall boundary. Although it is called stall flutter, this phenomenon does not require the stalling of the fan blade in the sense that it can occur when the slope of the pressure rise characteristic is still negative. This type of flutter occurs with low nodal diameter forward traveling waves and it occurs for the first flap (1F) mode of blade vibration. For this paper, a computational fluid dynamics (CFD) code has been applied to a real fan of contemporary design; the code has been found to be reliable in predicting mean flow and aeroelastic behavior. When the mass flow is reduced, the flow becomes unstable, resulting in flutter or in stall (the stall perhaps leading to surge). When the relative tip speed into the fan rotor is close to sonic, it is found (by measurement and by computation) that the instability for the fan blade considered in this work results in flutter. The CFD has been used like an experimental technique, varying parameters to understand what controls the instability behavior. It is found that the flutter for this fan requires a separated region on the suction surface. It is also found that the acoustic pressure field associated with the blade vibration must be cut-on upstream of the rotor and cut-off downstream of the rotor if flutter instability is to occur. The difference in cut off conditions upstream and downstream is largely produced by the mean swirl velocity introduced by the fan rotor in imparting work and pressure rise to the air. The conditions for instability therefore require a three-dimensional geometric description and blades with finite mean loading. The third parameter that governs the flutter stability of the blade is the ratio of the twisting motion to the plunging motion of the 1F mode shape, which determines the ratio of leading edge (LE) displacement to the trailing edge (TE) displacement. It will be shown that as this ratio increases the onset of flutter moves to a lower mass flow.

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