Optimal Design of Rotor Blades for an Axial Compressor Using the Gradient Based Method

2018 ◽  
pp. 498-509
Author(s):  
Hyung-Jin Kim ◽  
Hyeon-Jae Noh ◽  
Youn-Jea Kim
Keyword(s):  
Optimal Design ◽  
Axial Compressor ◽  
Rotor Blades ◽  
Gradient Based

Aerodynamic-Rotordynamic Interaction in Axial Compression Systems—Part I: Modeling and Analysis of Fluid-Induced Forces

2003 ◽  
Vol 125 (3) ◽  
pp. 405-415
Author(s):  
Ammar A. Al-Nahwi ◽  
James D. Paduano ◽  
Samir A. Nayfeh
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Essential Element ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Analytical Models ◽  
Modeling And Analysis ◽  
Equal Importance ◽  
Consistent Treatment

This paper presents a first principles-based model of the fluid-induced forces acting on the rotor of an axial compressor. These forces are primarily associated with the presence of a nonuniform flow field around the rotor, such as that produced by a rotor tip clearance asymmetry. Simple, analytical expressions for the forces as functions of basic flow field quantities are obtained. These expressions allow an intuitive understanding of the nature of the forces and—when combined with a rudimentary model of an axial compressor flow field (the Moore-Greitzer model)—enable computation of the forces as a function of compressor geometry, torque and pressure-rise characteristics, and operating point. The forces predicted by the model are also compared to recently published measurements and more complex analytical models, and are found to be in reasonable agreement. The model elucidates that the fluid-induced forces comprise three main contributions: fluid turning in the rotor blades, pressure distribution around the rotor, and unsteady momentum storage within the rotor. The model also confirms recent efforts in that the orientation of fluid-induced forces is locked to the flow nonuniformity, not to tip clearance asymmetry as is traditionally assumed. The turning and pressure force contributions are shown to be of comparable magnitudes—and therefore of equal importance—for operating points between the design point and the peak of the compressor characteristic. Within this operating range, both “forward” and “backward” rotor whirl tendencies are shown to be possible. This work extends recent efforts by developing a more complete, yet compact, description of fluid-induced forces in that it accounts for all relevant force contributions, both tangential and radial, that may influence the dynamics of the rotor. Hence it constitutes an essential element of a consistent treatment of rotordynamic stability under the action of fluid-induced forces, which is the subject of Part II of this paper.

Cold Blade Profile Generation Methodology for Compressor Rotor Blades Using FSI Approach

2017 ◽  
Author(s):  
Kirubakaran Purushothaman ◽  
Sankar Kumar Jeyaraman ◽  
Ajay Pratap ◽  
Kishore Prasad Deshkulkarni
Keyword(s):  
Aspect Ratio ◽  
Rotor Blade ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Blade Profile ◽  
Interaction Technique ◽  
Compressor Rotor ◽  
Blade Shape ◽  
Blade Geometry

This paper describes a methodology for obtaining correct blade geometry of high aspect ratio axial compressor blades during running condition taking into account of blade untwist and bending. It discusses the detailed approach for generating cold blade geometry for axial compressor rotor blades from the design blade geometry using fluid structure interaction technique. Cold blade geometry represents the rotor blade shape at rest, which under running condition deflects and takes a new operating blade shape under centrifugal and aerodynamic loads. Aerodynamic performance of compressor primarily depends on this operating rotor blade shape. At design point it is expected to have the operating blade shape same as the intended design blade geometry and a slight mismatch will result in severe performance deterioration. Starting from design blade profile, an appropriate cold blade profile is generated by applying proper lean and pre-twist calculated using this methodology. Further improvements were carried out to arrive at the cold blade profile to match the stagger of design profile at design operating conditions with lower deflection and stress for first stage rotor blade. In rear stages, thermal effects will contribute more towards blade deflection values. But due to short blade span, deflection and untwist values will be of lower values. Hence difference between cold blade and design blade profile would be small. This methodology can especially be used for front stage compressor rotor blades for which aspect ratio is higher and deflections are large.

Quick Start of an Industrial Gas Turbine Engine Through the Development of “Silent Start” VGV Schedule

2020 ◽  
Author(s):  
Senthil Krishnababu ◽  
Vili Panov ◽  
Simon Jackson ◽  
Andrew Dawson
Keyword(s):  
Guide Vane ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Rotor Blades ◽  
Start Time ◽  
Turbine Engine ◽  
High Pressure Ratio ◽  
Compressor Map ◽  
Industrial Gas Turbine

Abstract In this paper, research that was carried out to optimise an initial variable guide vane schedule of a high-pressure ratio, multistage axial compressor is reported. The research was carried out on an extensively instrumented scaled compressor rig. The compressor rig tests carried out employing the initial schedule identified regions in the low speed area of the compressor map that developed rotating stall. Rotating stall regions that caused undesirable non-synchronous vibration of rotor blades were identified. The variable guide vane schedule optimisation carried out balancing the aerodynamic, aero-mechanical and blade dynamic characteristics gave the ‘Silent Start’ variable guide vane schedule, that prevented the development of rotating stall in the start regime and removed the non-synchronous vibration. Aerodynamic performance and aero-mechanical characteristics of the compressor when operated with the initial schedule and the optimised ‘Silent Start’ schedule are compared. The compressor with the ‘Silent Start’ variable guide vane schedule when used on a twin shaft engine reduced the start time to minimum load by a factor of four and significantly improved the operability of the engine compared to when the initial schedule was used.

Geometrical Variability Modelling of Axial Compressor Blisk Aerofoils and Evaluation of Impact on the Forced Response Problem

2020 ◽  
Author(s):  
Marco Gambitta ◽  
Arnold Kühhorn ◽  
Sven Schrape
Keyword(s):  
Computational Models ◽  
Axial Compressor ◽  
Principal Component ◽  
Forced Response ◽  
Rotor Blades ◽  
Civil Aviation ◽  
Mode Shapes ◽  
Stochastic Representation ◽  
Compressor Blades ◽  
Multiple Variable

Abstract The present work focuses on the effect of the manufacturing geometrical variability on the high-pressure compressor of a turbofan engine for civil aviation. The deviations of the geometry over the axial compressor blades are studied and modeled for the representation in the computational models. Such variability is of particular interest for the forced response problem, where small deviations of the geometry from the ideal nominal model can cause significant differences in the vibrational responses. The information regarding the geometrical mistuning is extracted from a set of manufactured components surface scans of a blade integrated disk (blisk) rotor. The optically measured geometries are parameterized, defining a set of opportune variables to describe the deviations. The dimension of the variables domain is reduced using the principal component analysis approach and a reconstruction of the modeled geometries is performed for the implementation in CFD and FEM solvers. The generated model allows a stochastic representation of the variability, providing an optimal set of variables to represent it. The aeroelastic analyses considering geometry based mistuning is carried out on a test-rig case, focusing on how such variability can affect the modal forcing generated on the blades. The force generated by the unsteady pressure field over the selected vibrational mode shapes of the rotor blades is computed through a validated CFD model. The uncertainty quantification of the geometrical variability effect on the modal forcing is performed employing Monte Carlo methods on a reduced model for the CFD solution, based on a single passage multi-blade row setup. The amplitude shift of the unsteady modal forcing is studied for different engine orders. In particular the scatter of the main engine orders forcing amplitudes for the manufactured blades can be compared with the nominal responses to predict the possible amplification due to the geometrical variability. Finally the results are compared to a full assembly computational model to assess the influence of multiple variable blades.

scholarly journals Experimental Assessment of Fouling Effects in a Multistage Axial Compressor

2020 ◽  
Vol 197 ◽  
pp. 11007
Author(s):  
Nicola Casari ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Alessio Suman ◽  
Alessandro Vulpio
Keyword(s):  
Gas Turbine ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Small Scale ◽  
Performance Loss ◽  
Machine Performance ◽  
Internal Surfaces ◽  
Analysis Package ◽  
Multistage Axial Compressor

The study of the adhesion of micro sized particles to gas turbine internal surfaces, commonly known as gas turbine fouling, has gained increasing attention in the last years due to its dramatic effect on machine performance and reliability. On-field fouling analysis is mostly related to visual inspections during overhaul and/or programmed stops, which are performed, in particular, when gas turbine performance degradation falls under predetermined thresholds. However, these analyses, even if performed in the most complete as possible way, are rarely (or never) related to the conditions under which the gas turbine contamination takes place since the affecting parameters are difficult or even impossible to be adequately monitored. In the present work, a small scale multistage axial compressor is used to experimentally simulate the fouling phenomenon. The test rig allows the accurate control of the most relevant operating parameters which influence the fouling phenomenon. The compressor performance loss due to particle contamination has been quantitatively assessed. Soot particles appear stickier, especially in the presence of high humidity, and represent the most harmful operating conditions for the compressor unit. The deposits on the stator vanes and the rotor blades have been detected and post-processed, highlighting the most affected regions of each compressor stage employing an image analysis package tool.

Aerodynamic-Rotordynamic Interaction in Axial Compression Systems: Part I — Modeling and Analysis of Fluid-Induced Forces

2002 ◽  
Author(s):  
Ammar A. Al-Nahwi ◽  
James D. Paduano ◽  
Samir A. Nayfeh
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Essential Element ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Analytical Models ◽  
Modeling And Analysis ◽  
Equal Importance ◽  
Consistent Treatment

This paper presents a first principles-based model of the fluid-induced forces acting on the rotor of an axial compressor. These forces are primarily associated with the presence of a nonuniform flow field around the rotor, such as that produced by a rotor tip clearance asymmetry. Simple, analytical expressions for the forces as functions of basic flow field quantities are obtained. These expressions allow an intuitive understanding of the nature of the forces and—when combined with a rudimentary model of an axial compressor flow field (the Moore-Greitzer model)—enable computation of the forces as a function of compressor geometry, torque and pressure-rise characteristics, and operating point. The forces predicted by the model are also compared to recently published measurements and more complex analytical models, and are found to be in reasonable agreement. The model elucidates that the fluid-induced forces comprise three main contributions: fluid turning in the rotor blades, pressure distribution around the rotor, and unsteady momentum storage within the rotor. The model also confirms recent efforts in that the orientation of fluid-induced forces is locked to the flow nonuniformity, not to tip clearance asymmetry as is traditionally assumed. The turning and pressure force contributions are shown to be of comparable magnitudes—and therefore of equal importance—for operating points between the design point and the peak of the compressor characteristic. Within this operating range, both “forward” and “backward” rotor whirl tendencies are shown to be possible. This work extends recent efforts by developing a more complete, yet compact, description of fluid-induced forces in that it accounts for all relevant force contributions, both tangential and radial, that may influence the dynamics of the rotor. Hence it constitutes an essential element of a consistent treatment of rotordynamic stability under the action of fluid-induced forces, which is the subject of Part II of this paper.

Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall: Part II — Evaluation of Approaches

2003 ◽  
Author(s):  
L. G. Fre´chette ◽  
O. G. McGee ◽  
M. B. Graf
Keyword(s):  
Structural Parameters ◽  
Axial Compressor ◽  
Coupled System ◽  
Rotating Stall ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Theoretical Evaluation ◽  
Axial Compressors ◽  
Spatial Modes ◽  
Control Authority

A theoretical evaluation was conducted delineating how aeromechanical feedback control can be utilized to stabilize the inception of rotating stall in axial compressors. Ten aeromechanical control methodologies were quantitatively examined based on the analytical formulations presented in the first part of this paper (McGee et al, 2003a). The maximum operating range for each scheme is determined for optimized structural parameters, and the various schemes are compared. The present study shows that the most promising aeromechanical designs and controls for a class of low-speed axial compressors were the use of dynamic fluid injection. Aeromechanically incorporating variable duct geometries and dynamically re-staggered IGV and rotor blades were predicted to yield less controllability. The aeromechanical interaction of a flexible casing wall was predicted to be destabilizing, and thus should be avoided by designing sufficiently rigid structures to prevent casing ovalization or other structurally-induced variations in tip clearance. Control authority, a metric developed in the first part of this paper, provided a useful interpretation of the aeromechanical damping of the coupled system. The model predictions also show that higher spatial modes can become limiting with aeromechanical feedback, both in control of rotating stall as well as in considering the effects of lighter, less rigid structural aeroengine designs on compressor stability.

An improved formulation for optimizing rocker-bogie suspension rover for climbing steps

2019 ◽  
Vol 233 (18) ◽  
pp. 6538-6558 ◽  
Author(s):  
Sam Noble ◽  
K Kurien Issac
Keyword(s):  
Nonlinear Programming ◽  
Optimal Design ◽  
Local Minimum ◽  
Single Step ◽  
Optimal Solutions ◽  
Performance Parameters ◽  
Smooth Functions ◽  
Gradient Based ◽  
Wheel Radius ◽  
Better Than

We address the problem of improving mobility of rovers with rocker-bogie suspension. Friction and torque requirements for climbing a single step were considered as performance parameters. The main contribution of the paper is an improved formulation for rover optimization using smooth functions, which enables use of powerful gradient based nonlinear programming (NLP) solvers for finding solutions. Our formulation does not have certain shortcomings present in some earlier formulations. We first formulate the problem of determining optimal torques to be applied to the wheels to minimize (a) friction requirement, and (b) torque requirement, and obtain demonstrably optimal solutions. We then formulate the problem of optimal design of the rover itself. Our solution for climbing a step of height two times the wheel radius is 13% better than that of the nominal rover. This solution is verified to be a local minimum by checking Karush–Kuhn–Tucker conditions. Optimal solutions were obtained for both forward and backward climbing. We show that some earlier formulations cannot obtain optimal solutions in certain situations. We also obtained optimal design for climbing steps of three different heights, with a friction requirement which is 15% lower than that of the nominal rover.

Stall Inception and Development Process Due to Tip Leakage Flow in Axial Compressor Rotor Blades Row

2014 ◽  
Vol 30 (3) ◽  
pp. 307-313 ◽  
Author(s):  
R. Taghavi-Zenou ◽  
S. Abbasi ◽  
S. Eslami
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Compressor ◽  
Leading Edge ◽  
Rotor Blades ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Compressor Rotor

ABSTRACTThis paper deals with tip leakage flow structure in subsonic axial compressor rotor blades row under different operating conditions. Analyses are based on flow simulation utilizing computational fluid dynamic technique. Three different circumstances at near stall condition are considered in this respect. Tip leakage flow frequency spectrum was studied through surveying instantaneous static pressure signals imposed on blades surfaces. Results at the highest flow rate, close to the stall condition, showed that the tip vortex flow fluctuates with a frequency close to the blade passing frequency. In addition, pressure signals remained unchanged with time. Moreover, equal pressure fluctuations at different passages guaranteed no peripheral disturbances. Tip leakage flow frequency decreased with reduction of the mass flow rate and its structure was changing with time. Spillage of the tip leakage flow from the blade leading edge occurred without any backflow in the trailing edge region. Consequently, various flow structures were observed within every passage between two adjacent blades. Further decrease in the mass flow rate provided conditions where the spilled flow ahead of the blade leading edge together with trailing edge backflow caused spike stall to occur. This latter phenomenon was accompanied by lower frequencies and higher amplitudes of the pressure signals. Further revolution of the rotor blade row caused the spike stall to eventuate to larger stall cells, which may be led to fully developed rotating stall.

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