scholarly journals Analysis of Aerodynamically Induced Whirling Forces in Axial Flow Compressors

2000 ◽  
Vol 122 (4) ◽  
pp. 761-768 ◽  
Author(s):  
Z. S. Spakovszky
Keyword(s):  
System Analysis ◽  
Axial Flow ◽  
Tip Clearance ◽  
Design Tools ◽  
Mean Flow ◽  
Blade Loading ◽  
Force Prediction ◽  
Engine Design ◽  
Comparable Magnitude ◽  
Axial Flow Compressors

A new analytical model to predict the aerodynamic forces in axial flow compressors due to asymmetric tip-clearance is introduced. The model captures the effects of tip-clearance induced distortion (i.e., forced shaft whirl), unsteady momentum-induced tangential blade forces, and pressure-induced forces on the spool. Pressure forces are shown to lag the tip-clearance asymmetry, resulting in a tangential (i.e., whirl-inducing) force due to spool pressure. This force can be of comparable magnitude to the classical Alford force. Prediction and elucidation of the Alford force is also presented. In particular, a new parameter denoted as the blade loading indicator is deduced. This parameter depends only on stage geometry and mean flow and determines the direction of whirl tendency due to tangential blade loading forces in both compressors and turbines. All findings are suitable for incorporation into an overall dynamic system analysis and integration into existing engine design tools. [S0889-504X(00)01604-4]

scholarly journals Analysis of Aerodynamically Induced Whirling Forces in Axial Flow Compressors

2000 ◽  
Author(s):  
Z. S. Spakovszky
Keyword(s):  
System Analysis ◽  
Axial Flow ◽  
Tip Clearance ◽  
Design Tools ◽  
Mean Flow ◽  
Blade Loading ◽  
Force Prediction ◽  
Engine Design ◽  
Comparable Magnitude ◽  
Axial Flow Compressors

A new analytical model to predict the aerodynamic forces in axial flow compressors due to asymmetric tip-clearance is introduced. The model captures the effects of tip-clearance induced distortion (i.e. forced shaft whirl), unsteady momentum-induced tangential blade forces and pressure induced forces on the spool. Pressure forces are shown to lag the tip-clearance asymmetry, resulting in a tangential (i.e. whirl-inducing) force due to spool pressure. This force can be of comparable magnitude to the classical Alford force. Prediction and elucidation of the Alford force is also presented. In particular, a new parameter denoted as the blade loading indicator is deduced. This parameter depends only on stage geometry and mean flow and determines the direction of whirl tendency due to tangential blade loading forces in both compressors and turbines. All findings are suitable for incorporation into an overall dynamic system analysis and integration into existing engine design tools.

Performance prediction of axial flow compressors using stage characteristics and simultaneous calculation of interstage parameters

2001 ◽  
Vol 215 (1) ◽  
pp. 89-98 ◽  
Author(s):  
T. W. Song ◽  
T. S. Kim ◽  
J. H. Kim ◽  
S. T. Ro
Keyword(s):  
Gas Turbine ◽  
System Analysis ◽  
Axial Flow ◽  
Performance Estimation ◽  
Predicting Performance ◽  
Functional Formulation ◽  
Compressor Inlet ◽  
Multistage Compressors ◽  
And Performance ◽  
Axial Flow Compressors

A new method for predicting performance of multistage axial flow compressors is proposed that utilizes stage performance curves. The method differs from the conventional sequential stage-stacking method in that it employs simultaneous calculation of all interstage variables (temperature, pressure and flow velocity). A consistent functional formulation of governing equations enables this simultaneous calculation. The method is found to be effective, i.e. fast and stable, in obtaining solutions for compressor inlet and outlet boundary conditions encountered in gas turbine analyses. Another advantage of the method is that the effect of changing the angles of movable stator vanes on the compressor's operating behaviour can be simulated easily. Accordingly, the proposed method is very suitable for complicated gas turbine system analysis. This paper presents the methodology and performance estimation results for various multistage compressors employing both fixed and variable vane setting angles. The effect of interstage air bleeding on compressor performance is also demonstrated.

scholarly journals Analysis of Efficiency Sensitivity Associated With Tip Clearance in Axial Flow Compressors

1988 ◽  
Author(s):  
Ian N. Moyle
Keyword(s):  
Axial Flow ◽  
Tip Clearance ◽  
Design Parameters ◽  
Published Data ◽  
Constant Flow ◽  
Stage Design ◽  
Axial Compressors ◽  
Sensitivity Range ◽  
Loss Method ◽  
Axial Flow Compressors

The effects of tip clearance changes on efficiency in axial compressors are typically established experimentally. The ratio of change of efficiency with change of clearance gap varies significantly for different compressors in the published data. An analysis of this sensitivity range in terms of the blade and stage design parameters was initiated. The analysis revealed that the sensitivity range largely resulted from a derivation at constant flow of the efficiency decrement. It was also found that a generalized loss method of generating the sensitivities produced a much improved correlation of the change in efficiency with change in clearance over a variety of machines, configurations and speeds.

Rotor Whirl Forces Induced by the Tip Clearance Effect in Axial Flow Compressors

1993 ◽  
Author(s):  
Fredric Ehrich
Keyword(s):  
Experimental Data ◽  
Tangential Force ◽  
Axial Flow ◽  
Tip Clearance ◽  
Aircraft Engines ◽  
Peak Efficiency ◽  
Compressor Rotor ◽  
Strong Resemblance ◽  
Gas Turbine Compressor ◽  
Axial Flow Compressors

Abstract It is now widely recognized that destabilizing forces, tending to generate forward rotor whirl, are generated in axial flow turbines as a result of the non-uniform torque induced by the non-uniform tip-clearance in a deflected rotor — the so called Thomas/Alford force (Thomas, 1958 and Alford, 1965). It is also recognized that there will be a similar effect in axial flow compressors, but qualitative considerations cannot definitively establish the magnitude or even the direction of the induced whirling forces — that is, if they will tend to forward or backward whirl. Applying a “parallel compressor” model to simulate the operation of a compressor rotor deflected radially in its clearance, it is possible to derive a quantitative estimate of the proportionality factor β which relates the Thomas/Alford force in axial flow compressors (i.e., the tangential force generated by a radial deflection of the rotor) to the torque level in the compressor. The analysis makes use of experimental data from the GE Aircraft Engines Low Speed Research Compressor facility comparing the performance of three different axial flow compressors, each with four stages (typical of a mid-block of an aircraft gas turbine compressor) at two different clearances (expressed as a percent of blade length) — CL/L = 1.4% and CL/L = 2.8%. It is found that the value of β is in the range of +0.27 to −0.71 in the vicinity of the stages’ nominal operating line and +0.08 to −1.25 in the vicinity of the stages’ operation at peak efficiency. The value of β reaches a level of between −1.16 and −3.36 as the compressor is operated near its stalled condition. The final result bears a very strong resemblance to the correlation obtained by improvising a normalization of the experimental data of Vance and Laudadio (1984) and a generic relationship to the analytic results of Colding-Jorgensen (1990).

scholarly journals Three-Dimensional Performance Prediction of Multistage Axial Flow Compressors With a Repeating Stage Model

1999 ◽  
Author(s):  
Y. G. Li ◽  
A. Tourlidakis ◽  
R. L. Elder
Keyword(s):  
Performance Prediction ◽  
Static Pressure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Correction Method ◽  
Tip Clearance ◽  
Stage Model ◽  
Inlet Velocity ◽  
Average Value ◽  
Axial Flow Compressors

In this paper, a method for the performance prediction of multistage axial flow compressors through a steady, three-dimensional, multi-block Navier-Stokes solver is presented. A repeating stage model has been developed aiming at the simplification of the required global aerodynamic boundary conditions for the simulation of the rear stages of multistage axial compressors where only mass flow rate and exit average static pressure are required. The stage inlet velocity distribution is fixed to be equal to the one calculated at the stage exit and the exit static pressure distribution is fixed to have the same shape to that at inlet but maintain its own average value. A mixing plane approach is used to exchange information between neighbouring blade rows which allows both radial and circumferential variations at both sides of the interface. A pressure correction method with the standard k–ε turbulence model is used in combination with Stone’s two step procedure for the solution of the algebraic system of the discretised equations. A global iteration is carried out in order to establish the physical consistency between the blade rows. A combination of two structured grid blocks for the rotor blade row, one for the main passage and a second for the modelling of the tip clearance, is used for a detailed representation of the leakage flows. Computational results from two methods, the first by using the repeating stage model and the second by setting stage inlet velocity profile, are presented from the analysis of the third stage of the four-stage Cranfield Low Speed Research Compressor (LSRC). Good agreements with the experimental data are obtained in terms of total pressure, static pressure and velocity distributions at the inlet, exit and interface planes proving that the repeating stage model is a very economical and accurate alternative to the very expensive complete multistage simulations.

Influence of Tip Clearance on the Turbulent Aerodynamics of Axial Flow Fan under off Design Conditions

2012 ◽  
Vol 232 ◽  
pp. 223-227
Author(s):  
Praveen Kumar Akula ◽  
Balbir Singh ◽  
M. Manikandan ◽  
G. Srinivas
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Tip Clearance ◽  
Field Energy ◽  
Mean Flow ◽  
Compressor Aerodynamics ◽  
Mass Flow Rates ◽  
Paper Work ◽  
The Mean ◽  
Varying Mass

Compressor is a dynamic machine with complicated 3d aerodynamics. Dynamics creates an uncertain environment and induces the flow with instabilities, resulting in reduced performance. Motion being circumferential, flow is also subjected to rotational accelerations. Added to these complications are the tip gap and related vortex aerodynamics in the tip region, which also influence the passage flow of the rotor and thus complicates the flow field. The result of these implications is the generation of the turbulence in the flow field. Turbulence is a fluctuating characteristic of the flow, which extracts its energy from the mean flow field. Energy consumed by the turbulent nature of flow is a waste. Therefore it is very much important to understand about the influence of the turbulence and related kinetic energy compressor aerodynamics. In this paper work is presented to understand about the turbulence under such varying geometry conditions of flow, as well as blade. Results of nature of the turbulence and its growth are discussed for varying mass flow rates and different tip gaps of acceptable range.

End-Wall and Profile Losses in a Low-Speed Axial Flow Compressor Rotor

1986 ◽  
Vol 108 (1) ◽  
pp. 22-31 ◽  
Author(s):  
B. Lakshminarayana ◽  
N. Sitaram ◽  
J. Zhang
Keyword(s):  
Axial Flow ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Blade Loading ◽  
Pressure Losses ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Profile Losses ◽  
Flow Compressor ◽  
End Wall

The blade-to-blade variation of relative stagnation pressure losses in the tip region inside the rotor of a single-stage, axial-flow compressor is presented and interpreted in this paper. The losses are measured at two flow coefficients (one at the design point and the other at the near peak pressure rise point) to discern the effect of blade loading on the end-wall losses. The tip clearance losses are found to increase with an increase in the pressure rise coefficient. The losses away from the tip region and near the hub regions are measured downstream. The losses are integrated and interpreted in this paper.

Sign in / Sign up

Export Citation Format

Share Document