Nonaxisymmetric Blade Row Interaction in Axial Turbomachines

1981 ◽  
Vol 103 (1) ◽  
pp. 201-209
Author(s):  
N. A. Mitchell
Keyword(s):  
Three Dimensional ◽  
Interaction Effects ◽  
Numerical Calculations ◽  
Relative Importance ◽  
Streamwise Vorticity ◽  
Wake Interaction ◽  
Blade Row ◽  
Blade Row Interaction

A three-dimensional nonaxisymmetric theory is presented to analyze the interaction effects due to wakes between two blade rows in an axial turbomachine. The relative importance of potential and wake interaction with varying row separations and the contribution to the flow of shed radial and shed streamwise vorticity from the first row are examined. Numerical calculations of turbine and compressor stages are presented to illustrate the theory.

scholarly journals Non-Axisymmetric Blade Row Interaction in Axial Turbomachines

1980 ◽  
Author(s):  
N. A. Mitchell
Keyword(s):  
Three Dimensional ◽  
Interaction Effects ◽  
Numerical Calculations ◽  
Relative Importance ◽  
Streamwise Vorticity ◽  
Wake Interaction ◽  
Blade Row ◽  
Blade Row Interaction

A three-dimensional non-axisymmetric theory is presented to analyze the interaction effects due to wakes between two blade rows in an axial turbomachine. The relative importance of potential and wake interaction with varying row separations and the contribution to the flow of shed radial and shed streamwise vorticity from the first row are examined. Numerical calculations of turbine and compressor stages are presented to illustrate the theory.

Analysis of Unsteady Blade Row Interaction Using Nonlinear Harmonic Approach

2000 ◽  
Author(s):  
T. Chen ◽  
P. Vasanthakumar ◽  
L. He
Keyword(s):  
Stokes Equations ◽  
Linear Time ◽  
Three Dimensional ◽  
Axial Flow ◽  
Interaction Effects ◽  
Navier Stokes ◽  
Linear Interaction ◽  
Blade Row ◽  
Non Linear ◽  
Blade Row Interaction

An efficient non-linear harmonic methodology has been developed for predicting unsteady blade row interaction effects in multistage axial flow compressors. Flow variables are decomposed into time averaged variables and unsteady perturbations, resulting in time averaged equations with deterministic stress terms depending on the unsteady perturbation. The non-linear interaction between the time averaged flow field and the unsteady perturbations are included by a simultaneous pseudotime integration approach, leading to a strongly coupled solution. The stator/rotor interface treatment follows a flux averaged characteristic based mixing plane approach and includes the deterministic stress terms due to upstream running potential disturbances and downstream running wakes, resulting in the continuous nature of all parameters across the interface. The basic computational methodology is applied to the three-dimensional Navier-Stokes equations and validated against several cases. Results show that this method is much more efficient than the non-linear time-marching methods while still modeling the nonlinear unsteady blade row interaction effects.

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.

Excess Streamwise Vorticity and Its Role in Secondary Flow

1987 ◽  
Vol 201 (6) ◽  
pp. 413-420 ◽  
Author(s):  
P W James
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Point Of View ◽  
Streamwise Vorticity ◽  
Three Dimensional Flow ◽  
Approximate Methods ◽  
Blade Row ◽  
Flow Through ◽  
Loss Term

The purpose of this paper is, firstly, to show how the concept of excess secondary vorticity arises naturally from attempts to recover three-dimensional flow details lost in passage-averaging the equations governing the flow through gas turbines. An equation for the growth of excess streamwise vorticity is then derived. This equation, which allows for streamwise entropy gradients through a prescribed loss term, could be integrated numerically through a blade-row to provide the excess vorticity at the exit to a blade-row. The second part of the paper concentrates on the approximate methods of Smith (1) and Came and Marsh (2) for estimating this quantity and demonstrates their relationship to each other and to the concept of excess streamwise vorticity. Finally the relevance of the results to the design of blading for gas turbines, from the point of view of secondary flow, is discussed.

Interaction Effects in a Transonic Turbine Stage

2000 ◽  
Author(s):  
J. W. Barter ◽  
P. H. Vitt ◽  
J. P. Chen
Keyword(s):  
Analytical Techniques ◽  
Interaction Effects ◽  
Phase Lag ◽  
Turbine Stage ◽  
Reflected Waves ◽  
Blade Row ◽  
Transonic Turbine ◽  
Unsteady Loading ◽  
Unsteady Pressure Measurements ◽  
Blade Row Interaction

A 3D, viscous, time-accurate code has been used to predict the time-dependent flowfield in a transonic turbine stage. Two analytical techniques are used to understand the unsteady physics. One technique takes into account interaction effects associated with reflected waves bouncing between blade rows while the other neglects them. Both techniques model the exact blade counts using phase-lag boundary conditions. The analytical techniques are validated by comparing to unsteady pressure measurements which have been made on the vane and blade surfaces at midspan. The analytical results are then used to understand the importance of interaction effects when the blade rows are close-coupled and when they are more widely spaced. The results show that interaction effects must be taken into account in order to accurately predict the unsteady loading on the upstream blade row. However, for the downstream blade row, interaction effects are second order and do not routinely need to be taken into account in the design process.

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.

A Three-Dimensional Linearized Euler Analysis of Classical Wake/Stator Interactions: Validation and Unsteady Response Predictions

2002 ◽  
Vol 1 (2) ◽  
pp. 137-163 ◽  
Author(s):  
D. Prasad ◽  
J.M. Verdon
Keyword(s):  
Three Dimensional ◽  
Phase Variation ◽  
Detailed Comparison ◽  
Numerical Results ◽  
Acoustic Response ◽  
Lifting Surface ◽  
Blade Row ◽  
Rotor Stator Interaction ◽  
Blade Row Interaction ◽  
Lifting Line

A comprehensive validation of the linearized Euler analysis, LINFLUX, for wake/blade row interaction is carried out. The flow configuration is that of the benchmark problem for rotor-stator interaction proposed at the Third Computational Aeroacoustics Workshop. It consists of an unstaggered, annular, flat-plate blade row excited by the vortical gusts associated with the wakes shed from an upstream rotor. The numerical results for the unsteady pressure responses of the stator are compared with semi-analytic lifting surface and lifting line solutions. The validation is first conducted for narrow-annulus flows, where the numerical results are shown to agree well with classical two-dimensional solutions over a range of frequencies. We then carry out a detailed comparison of the three-dimensional LINFLUX results with the lifting surface results of Namba and Schulten for a blade row with a hub-to-tip ratio of 0.5. This study encompasses gust excitation frequencies for which the stator responses vary from cut off to propagating, as well as gusts with varying degrees of spanwise variation. The numerical and semi-analytical analyses yield results for the stator pressure response, including the complex amplitudes of the propagating and least attenuated, evanescent, pressure modes that are in very good agreement. The effect of increasing the spanwise phase variation of the gust is generally, but not necessarily, to reduce the power associated with the acoustic response of the blade row. A comparison of the present numerical results with those obtained from a stripwise application of classical linear theory reveals that the latter approach can be erroneous and, therefore, of questionable applicability to realistic turbomachinery unsteady flows.

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