Numerical Simulation of the Effects of Rotor-Stator Spacing and Wake/Blade Count Ratio on Turbomachinery Unsteady Flows

1995 ◽  
Vol 117 (4) ◽  
pp. 639-646 ◽  
Author(s):  
W.-S. Yu ◽  
B. Lakshminarayana
Keyword(s):  
Incompressible Flows ◽  
Unsteady Flows ◽  
Loss Coefficient ◽  
Navier Stokes ◽  
Frequency Effect ◽  
Row Spacing ◽  
Rotor Wake ◽  
Count Ratio ◽  
Reduced Frequency ◽  
Blade Row

A two-dimensional time-accurate Navier-Stokes solver for incompressible flows is used to simulate the effects of the axial spacing between an upstream rotor and a stator, and the wake/blade count ratio on turbomachinery unsteady flows. The code uses a pressure-based method. A low-Reynolds number two-equation turbulence model is incorporated to account for the turbulence effect. By computing cases with different spacing between an upstream rotor wake and a stator, the effect of the spacing is simulated. Wake/blade count ratio effect is simulated by varying the number of rotor wakes in one stator passage at the computational inlet plane. Results on surface pressure, unsteady velocity vectors, blade boundary layer profiles, rotor wake decay and loss coefficient for all the cases are interpreted. It is found that the unsteadiness in the stator blade passage increases with a decrease in the blade row spacing and a decrease in the wake/blade count ratio. The reduced frequency effect is dominant in the wake/blade count ratio simulation. The time averaged loss coefficient increases with a decrease in the axial blade row spacing and an increase in the wake/blade count ratio.

scholarly journals Wake Vorticity Decay and Blade Response in an Axial Compressor With Varying Axial Gap

1999 ◽  
Author(s):  
A. M. Wo ◽  
M. H. Chung ◽  
S. J. Chang ◽  
S. F. Lee
Keyword(s):  
Large Scale ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Rotor Wake ◽  
Blade Loading ◽  
Wake Interaction ◽  
Blade Row ◽  
Unsteady Force ◽  
Gap Spacing ◽  
Blade Row Interaction

This paper addresses the decay of rotor wake vorticity for a rotor/stator axial compressor, with the axial gap between blade rows being 10, 20 and 30 percent chord, and at both design and high loading levels. Experiments were conducted in a large-scale, low-speed axial compressor. Navier-Stokes calculations were also executed. Both data and Navier-Stokes results reveal that the decay of rotor wake vorticity increases substantially as the axial gap decreases; the decay for 10 percent gap is about twice that of 30 percent. Increased time-mean blade loading causes the vorticity decay to also increase, with this effect more pronounced for large axial gap than small. At the stator inlet mid-pitch location, the wake maximum vorticity for 10 and 30 percent chord gap cases being nearly the same (differ by 3.8%) at design loading. The corresponding stator unsteady force agrees within 5.2%. Variation of vorticity decay with axial gap is directly linked to the change in potential disturbance by the downstream stator on the rotor wake due to the change in gap spacing. This suggests that the stator potential disturbance causes the upstream rotor wake to decay at an increased rate which, in turns, results in a lowered level of stator response compared to that without this stator/wake interaction effect. Thus, in this context, blade row interaction is considered beneficial.

scholarly journals Numerical Simulations of Unsteady Cascade Flows

1993 ◽  
Author(s):  
Daniel J. Dorney ◽  
Joseph M. Verdon
Keyword(s):  
Numerical Simulations ◽  
Nonlinear Analysis ◽  
Unsteady Flows ◽  
Limited Range ◽  
Navier Stokes ◽  
Viscous Effects ◽  
Blade Vibration ◽  
Wide Range ◽  
Blade Row ◽  
Acoustic Excitations

A time-accurate Navier-Stokes analysis is needed for understanding the relative importance of nonlinear and viscous effects on the unsteady flows associated with turbomachinery blade vibration and blade-row noise generation. For this purpose an existing multi-blade-row Navier-Stokes analysis has been modified and applied to predict unsteady flows excited by entropic, vortical, and acoustic disturbances through isolated, two-dimensional blade rows. In particular, time-accurate, nonreflecting inflow and outflow conditions have been implemented to allow specification of vortical, entropic, and acoustic excitations at the inlet, and acoustic excitations at the exit, of a cascade. To evaluate the nonlinear analysis, inviscid and viscous numerical simulations were performed for benchmark unsteady flows and the predicted results were compared with analytical and numerical results based on linearized inviscid flow theory. For small amplitude unsteady excitations, the unsteady pressure responses predicted with the nonlinear analysis show very good agreement, both in the field and along the blade surfaces, with linearized inviscid solutions. Based on a limited range of parametric studies, it was also found that the unsteady responses to inlet vortical and acoustic excitations are linear over a surprisingly wide range of excitation amplitudes, but acoustic excitations from downstream produce responses with significant nonlinear content.

Numerical and Experimental Analysis of the Effect of Variable Blade Row Spacing in a Subsonic Axial Turbine

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
M. Restemeier ◽  
P. Jeschke ◽  
Y. Guendogdu ◽  
J. Gier
Keyword(s):  
Axial Flow ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Row Spacing ◽  
Test Rig ◽  
Jet Propulsion ◽  
Turbine Efficiency ◽  
Air Turbine ◽  
Blade Row ◽  
Flow Interactions

Numerical and experimental investigations have been performed to determine the effect of a variation of the interblade row axial gap on turbine efficiency. The geometry used in this study is the 1.5-stage axial flow turbine rig of the Institute of Jet Propulsion and Turbomachinery at Rhejnisch Westfalische Technische Hochshule (RWTH) Aachen University. The influence of the blade row spacing on aerodynamics has been analyzed by conducting steady and unsteady Reynolds-averaged Navier-Stokes (RANS) simulations as well as measurements in the cold air turbine test rig of the Institute. Both potential and viscous flow interactions, including secondary flow, were investigated. The results show an aerodynamic improvement of efficiency and favorable spatial distribution of secondary kinetic energy by reduction of the axial gap.

Numerical Simulations of Unsteady Cascade Flows

1994 ◽  
Vol 116 (4) ◽  
pp. 665-675 ◽  
Author(s):  
D. J. Dorney ◽  
J. M. Verdon
Keyword(s):  
Numerical Simulations ◽  
Nonlinear Analysis ◽  
Unsteady Flows ◽  
Limited Range ◽  
Navier Stokes ◽  
Viscous Effects ◽  
Blade Vibration ◽  
Wide Range ◽  
Blade Row ◽  
Acoustic Excitations

A time-accurate Navier–Stokes analysis is needed for understanding the relative importance of nonlinear and viscous effects on the unsteady flows associated with turbomachinery blade vibration and blade-row noise generation. For this purpose an existing multi-blade-row Navier–Stokes analysis has been modified and applied to predict unsteady flows excited by entropic, vortical, and acoustic disturbances through isolated, two-dimensional blade rows. In particular, time-accurate, non-reflecting inflow and outflow conditions have been implemented to allow specification of vortical, entropic, and acoustic excitations at the inlet, and acoustic excitations at the exit, of a cascade. To evaluate the nonlinear analysis, inviscid and viscous numerical simulations were performed for benchmark unsteady flows and the predicted results were compared with analytical and numerical results based on linearized inviscid flow theory. For small-amplitude unsteady excitations, the unsteady pressure responses predicted with the nonlinear analysis show very good agreement, both in the field and along the blade surfaces, with linearized inviscid solutions. Based on a limited range of parametric studies, it was also found that the unsteady responses to inlet vortical and acoustic excitations are linear over a surprisingly wide range of excitation amplitudes, but acoustic excitations from downstream produce responses with significant nonlinear content.

Unsteady Cavity Flows: Oscillatory Flat Box Flows

1975 ◽  
Vol 42 (3) ◽  
pp. 557-563 ◽  
Author(s):  
V. O’Brien
Keyword(s):  
Reynolds Number ◽  
Incompressible Flows ◽  
Stokes Number ◽  
Analytic Solutions ◽  
Length Ratio ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Cavity Flows ◽  
Navier Stokes Equation ◽  
Reduced Frequency

The oscillatory cavity flows reported here are extensions of previously studied steady closed rectangular cavity flows (box flows). The periodic laminar incompressible flows are characterized by three numerical parameters, peak Reynolds number, a reduced frequency (or Stokes number) and the height-to-length ratio of the cavity. Depending on the height-to-length ratio, flow fields are obtained by finite-difference solutions or analytic solutions of the Navier-Stokes equation. The central portion of a flat cavity contains an oscillatory parallel flow. Experimental measurements corroborate the theory. Stokes number dependency and particularly differences from the corresponding steady flow (whose Stokes number is zero) are illustrated.

Numerical solution of the reduced Navier-Stokes equations for internal incompressible flows

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1603-1614
Author(s):  
Martin Scholtysik ◽  
Bernhard Mueller ◽  
Torstein K. Fannelop
Keyword(s):  
Numerical Solution ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations

scholarly journals Numerical analysis of high-lift configurations with oscillating flaps

2021 ◽  
Author(s):  
Johannes Ruhland ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Separated Flow ◽  
Navier Stokes ◽  
Rotational Axis ◽  
High Lift ◽  
Hinge Point ◽  
Reduced Frequency ◽  
Flap Deflection ◽  
The Impact

AbstractThis study presents two-dimensional aerodynamic investigations of various high-lift configuration settings concerning the deflection angles of droop nose, spoiler and flap in the context of enhancing the high-lift performance by dynamic flap movement. The investigations highlight the impact of a periodically oscillating trailing edge flap on lift, drag and flow separation of the high-lift configuration by numerical simulations. The computations are conducted with regard to the variation of the parameters reduced frequency and the position of the rotational axis. The numerical flow simulations are conducted on a block-structured grid using Reynolds Averaged Navier Stokes simulations employing the shear stress transport $$k-\omega $$ k - ω turbulence model. The feature Dynamic Mesh Motion implements the motion of the oscillating flap. Regarding low-speed wind tunnel testing for a Reynolds number of $$0.5 \times 10^{6}$$ 0.5 × 10 6 the flap movement around a dropped hinge point, which is located outside the flap, offers benefits with regard to additional lift and delayed flow separation at the flap compared to a flap movement around a hinge point, which is located at 15 % of the flap chord length. Flow separation can be suppressed beyond the maximum static flap deflection angle. By means of an oscillating flap around the dropped hinge point, it is possible to reattach a separated flow at the flap and to keep it attached further on. For a Reynolds number of $$20 \times 10^6$$ 20 × 10 6 , reflecting full scale flight conditions, additional lift is generated for both rotational axis positions.

Aerodynamic Asymmetry Analysis of Unsteady Flows in Turbomachinery

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Kivanc Ekici ◽  
Robert E. Kielb ◽  
Kenneth C. Hall
Keyword(s):  
Harmonic Balance ◽  
Coupling Effect ◽  
Unsteady Flows ◽  
Unsteady Aerodynamic ◽  
Blade Row ◽  
Balance Technique ◽  
Turbomachinery Blades ◽  
Aerodynamic Asymmetry ◽  
Frequency Domain Approach ◽  
Harmonic Balance Technique

A nonlinear harmonic balance technique for the analysis of aerodynamic asymmetry of unsteady flows in turbomachinery is presented. The present method uses a mixed time-domain/frequency-domain approach that allows one to compute the unsteady aerodynamic response of turbomachinery blades to self-excited vibrations. Traditionally, researchers have investigated the unsteady response of a blade row with the assumption that all the blades in the row are identical. With this assumption the entire wheel can be modeled using complex periodic boundary conditions and a computational grid spanning a single blade passage. In this study, the steady/unsteady aerodynamic asymmetry is modeled using multiple passages. Specifically, the method has been applied to aerodynamically asymmetric flutter problems for a rotor with a symmetry group of 2. The effect of geometric asymmetries on the unsteady aerodynamic response of a blade row is illustrated. For the cases investigated in this paper, the change in the diagonal terms (blade on itself) dominated the change in stability. Very little mode coupling effect caused by the off-diagonal terms was found.

scholarly journals Navier-Stokes and Potential Calculations of Axial Spacing Effect on Vortical and Potential Disturbances and Gust Response in an Axial Compressor

1995 ◽  
Author(s):  
Meng-Hsuan Chung ◽  
Andrew M. Wo
Keyword(s):  
Lower Order ◽  
Spacing Effect ◽  
Axial Compressor ◽  
Interaction Effects ◽  
Moving Frame ◽  
Navier Stokes ◽  
Blade Row ◽  
Vortical Disturbance ◽  
Blade Row Interaction ◽  
Gust Response

The effect of blade row axial spacing on vortical and potential disturbances and gust response is studied for a compressor stator/rotor configuration near design and at high loadings using 2D incompressible Navier-Stokes and potential codes, both written for multistage calculations. First, vortical and potential disturbances downstream of the isolated stator in the moving frame are defined; these disturbances exclude blade row interaction effects. Then, vortical and potential disturbances for the stator/rotor configuration are calculated for axial gaps of 10%, 20%, and 30% chord. Results show that the potential disturbance is uncoupled; the potential disturbance calculated from the isolated stator configuration is a good approximation for that from the stator/rotor configuration for all three axial gaps. The vortical disturbance depends strongly on blade row interactions. Low order modes of vortical disturbance are of substantial magnitude and decay much more slowly downstream than do those of potential disturbance. Vortical disturbance decays linearly with increasing mode except very close to the stator trailing edge. For a small axial gap, lower order modes of both vortical and potential disturbances must be included to determine the rotor gust response.

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