Design Of Axial Flow Compressors Research Articles

Sensitivity of Weighing Functions in Genetic Algorithm for Efficiency and Pressure Ratio Optimization in Transonic Axial Flow Compressor

Axial flow compressor design is a multi-objective problem with objectives such as maximization of efficiency, total pressure ratio, mass flow rate and minimization of weight. In this work, validated meanline design process is integrated with genetic algorithm to optimize the compressor design. Fitness function used to evaluate effectiveness of candidate design solutions is arithmetic summation of combination of objective functions and respective weighing functions. Objective functions considered are pressure ratio, efficiency and operating margin in terms of De-Haller Number and Diffusion Factor. The summation of all the weighing functions is unity in all the iterations carried out. Weighing functions of the objective functions used in fitness function dictate the performance. Sensitivity study of weighing functions for multi-objective fitness function has been conducted for the intended mass flow and total pressure ratio. Effect of sensitivity of weighing functions in multi-objective fitness function on efficiency and pressure ratio in transonic axial flow compressor design is studied and discussed. The study carried out shows maximum value of weighing function does not yield maximum value of the objective function. Design trial of weighing function combination of (0.3 pressure ratio and 0.3 efficiency) yields an optimum pressure ratio of 1.588 and 88.1% efficiency for optimized fitness function. The iterative data generated is useful for assigning weighing function value based on design requirement.

Improved criteria for stall-free preliminary design of axial compressor of aero gas turbine engines

A worldwide effort has been devoted to developing highly efficient and reliable gas turbine engines. There exist many prominent factors in the development of these engines. One of the most important features of the optimal design of axial flow compressors is satisfying the allowable range for various parameters such as flow coefficient, stage loading, the degree of reaction, De-Haller number, etc. But, there are some applicable cases that the mentioned criteria are exceeded. One of the most famous parameters is De-Haller number, which according to literature data should not be kept less than 0.72 in any stage of the axial compressor. A deep insight into the current small- or large-scale axial flow compressors shows that a discrepancy will occur among design criterion for De-Haller number and experimental measurements in which the De-Haller number is less than the design limit but no stall or surge is observed. In this paper, an improved formulation is derived based on one-dimensional modeling for predicting the stall-free design parameter ranges especially stage loading, flow coefficient, etc. for various combinations. It was found that the current criterion is much more accurate than the De-Haller criterion for design purposes.

Three-Dimensional Tailored Vibration Response and Flutter Control of High-Bypass Shroudless Aeroengine Fans

A new reduced-order design synthesis technology has been developed for vibration response and flutter control of cold-stream, high-bypass ratio, shroudless, aeroengine fans. To simplify the design synthesis (optimization) of the fan, a significant order reduction of the mechanical response and stiffness-shape design synthesis has been achieved. The assumed cyclic symmetric baseline fan is modeled as a cascade of tuned, shroudless, arbitrarily shaped, wide-chord laminated composite blades, each with a reduced order of degrees of freedom using a three-dimensional (3D) elasticity spectral-based energy model (McGee et al., 2013, “A Reduced-Order Meshless Energy Model for the Vibrations of Mistuned Bladed Disks—Part I: Theoretical Basis, ASME J. Turbomach., in press; Fang et al., 2013, “A Reduced-Order Meshless Energy Model for the Vibrations of Mistuned Bladed Disks—Part II: Finite Element Benchmark Comparisons, ASME J. Turbomach., in press). The uniqueness of the mechanical analysis is that the composite fan was modeled as a “meshless” continuum, consisting of nodal point data to describe the arbitrary volume. A stationary value of energy within the arbitrarily shaped composite fan annulus was achieved using an extended spectral-based Ritz procedure to obtain the dynamical equations of motion for 3D free vibration response of a rotating composite high-bypass fan. No additional kinematical constraints (as in beam, plate, or shell theories) were utilized in the 3D elasticity-based energy formulation. The convergence accuracy of the spectral-based 3D free vibration response predictions was nearly one percent upper-bounds on the exact mechanical response of the baseline composite fan, particularly in the lowest five modes studied closely in this work, as typically seen with spectral-based Ritz procedures employed in the analysis. The spectral-based 3D predictions was validated against those predicted using a general purpose finite element technology widely used by industry. In off-design operation, the frequency margins of the lower flex-torsion modes of a fan may be dangerously close to integral-order resonant and empirical stall flutter boundaries. For a given baseline composite fan, it is proposed that to reduce the likelihood of resonant response and flutter on a Campbell diagram, design analysts can efficiently unite the newly developed reduced-order 3D spectral-based energy reanalysis within a novel reduced-order spectral-based Kuhn–Tucker optimality design synthesis procedure to fairly accurately restructure the Campbell diagram of a composite high-bypass ratio fan using stiffness optimization (by means of proper choices of angle-ply orientations of the blade laminates) and mass-balancing (shape) optimization (by way of blade thickness variation tuning of the lower aerodynamic loading portion of the blades between the dovetail root section and the midradial height section of the composite fan annulus). Fan design optima is summarized that (1) achieves multiple frequency margins and satisfies multiple empirical stall flutter constraints, (2) controls the twist-flex vibratory response in the lowest (fundamental) mode, and (3) ensures the mechanical strength integrity of the optimized angle-ply lay-up under steady centrifugal tension and gas bending stresses. Baseline and optimally restructured Campbell diagrams and design sensitivity calculations are presented, comparing optimum solution accuracy and validity of the proposed reduced-order spectral-based design synthesis technology against optimum solutions generated from open-source nonlinear mathematical programming software (i.e., NASA’s general-purpose sequential unconstrained minimization technique, Newsumt-A) (Miura and Schmit, Jr., 1979, ”NEWSUMT–A, Fortran Program for Inequality Constrained Function Minimization—Users Guide,“ NASA CR-159070). Design histories of fan stiffness and mass balancing (or shape) along with nondimensional constraints (i.e., frequency margins, reduced frequencies, twist-flex vibratory response, first-ply failure principal stress limits, and dovetail-to-midblade height thickness distribution) show that a proper implementation of fan stiffness tailoring (via symmetric angle-ply orientations) and mass-balancing (thickness) optimization of the fan assembly produces a feasible Campbell diagram that satisfies all design goals. An off-design analysis of the optimized fan shows little sensitivity to twist-flex coupling response and flutter with respect to small variability or errors in optimum design construction. Industry manufacturing processes may introduce these small errors known as angle-ply laminate construction misalignments (Graham and Guentert, 1965, “Compressor Stall and Blade Vibration,” Aerodynamic Design of Axial-Flow Compressors, Chap. XI, NASA SP-36; Meher-Hornji, 1995, “Blading Vibration and Failures in Gas Turbines, Part A: Blading Dynamics and the Operating Environment,” ASME Paper 95-GT-418; Petrov et al., 2002, “A New Method for Dynamic Analysis of Mistuned Bladed Disks Based on the Exact Relationship Between Tuned and Mistuned Systems,” ASME J. Eng. Gas Turbines Power, 124(3), pp. 586–597; Wei and Pierre, 1990, “Statistical Analysis of the Forced Response of Mistuned Cyclic Assemblies,” ASME J. Eng. Gas Turbines Power, 28(5), pp. 861–868; Wisler, 1988, “Advanced Compressor and Fan Systems,” GE Aircraft Engines, Cincinnati, Ohio (also 1986 Lecture to ASME Turbomachinery Institute, Ames Iowa)).

An Axial Flow Compressor for Operation With Humid Air and Water Injection

The first steps of the turbomachinery design usually rely on numerical tools based on inviscid formulation with corrections using loss models to account for viscous effects, secondary flows, tip clearances, and shock waves. The viscous effects are accounted for using semi-empirical correlations especially assembled for the chosen airfoils and range of operating conditions. Fast convergence and good accuracy are required from such design procedures. There are successful models that produce very accurate performance prediction. Among the methodologies commonly used, the streamline curvature (SLC) is used since those characteristics and the most important properties can be calculated reasonably well at any radial positions, assisting other more complex analysis programs. The SLC technique is, therefore, well suited for the design of axial flow compressors for reasons such as quick access to vital flow properties at the blade edges from which actions may be taken to improve its performance at the design stage. This work reports the association of a SLC computer program and commercial software for comparison purposes, as well as for grid generation required by a full 3D, turbulent Navier–Stokes computer program used for flow calculation in the blade passages. Application to a high performance three-stage axial flow compressor with inlet guide vane demonstrates the methodology adopted. The SLC program is also capable of calculating the compressor performance with humid air and water injection at any axial position along the compressor. The influence of water injection at different axial positions, water particle diameter, and temperature of water particles were studied for different humid air conditions. The positions of the evaporating water particles were calculated using their thermophysical and dynamic properties along the compressor.

Experimental evaluation of pumpjet propulsor for an axisymmetric body in wind tunnel

Design of a Pump Jet Propulsor (PJP) was undertaken for an underwater body with axisymmetric configuration using axial flow compressor design techniques supported by Computational Fluid Dynamics (CFD) analysis for performance prediction. Experimental evaluation of the PJP was carried out through experiments in a Wind Tunnel Facility (WTF) using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP), residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle in water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.

Review of Fluid Mechanics and Thermodynamics of Turbomachinery, 5th Edition, by S. L. DixonFluid Mechanics and Thermodynamics of TurbomachineryElsevier Butterworth Heinemann0-7506-7870-4$49.95

Turbomachinery is encountered in numerous applications of modern technology, playing a dominant role in electric power generation steam and gas turbines, hydraulic turbines ; constituting the core of the jet engine, the most widely used aircraft propulsor today; and being employed in numerous other applications in the form of pumps, blowers, and compressors. This book provides a good overview of the design and operational characteristics of all types of turbomachinery. It mainly deals with the fluid mechanics and thermodynamic aspects of turbomachinery operation, while it provides basic information on technological issues, with glimpses of structural elements, control, and materials. This book, the fifth edition of a book that was first published about 40 years ago, has undergone substantial revision to bring the text up-to-date and give the reader a view of not only the standard principles but also state-of-the-art developments and problems. The present edition goes further from the traditional “closed” turbomachines by including a chapter on wind turbines, a type of device that is employed today in environmentally friendly electrical power generation. The book is divided into 10 chapters. Chapter 1 gives an introduction to turbomachinery and the derivation of the basic performance parameters by using dimensional analysis. Chapter 2 briefly reviews the basic fluid dynamic and thermodynamics laws that govern turbomachinery operation. The key concept of efficiency is introduced; and its different expressions for compressors, turbines, and nozzles are presented. Diffuser performance is also discussed. Compressor and turbine cascades are analyzed in Chapter 3, including semiempirical correlations for blade design and analysis. Axial flow turbine operation theory is given in Chapter 4. Basic design features are discussed, and the discussion goes further into some more specialized subjects, such as blade stresses and blade cooling. A substantial discussion is devoted to the Wells turbine, a special turbine used for renewable energy applications. Axial-flow compressor design features and operation are covered in Chapter 5, including a discussion on stall and surge phenomena and their control. Some basic notions of threedimensional flows in axial turbomachines are given in Chapter 6.

Axial flow compressor design†

The purpose of this paper is to set out some of the basic principles and rules associated with the design of axial flow compressors, principally for aero-engines, as well as the practical constraints that are inevitably present. The thrust is primarily on the aerodynamic design but this cannot be divorced from the mechanical aspects and so some of these are touched upon but are not gone into so deeply. The paper has been written from the point of view of the designer and tries to cover most of the points that need to be considered in order to produce a successful compressor. The emphasis has been on the theory behind the design process and on minimizing the reliance on empirical rules. However, because of the complexity of the flow, some empiricism still remains.

Axial Flow Compressor Design Optimization: Part II—Throughflow Analysis

A new technique is presented for the design optimization of an axial-flow compressor stage. The procedure allows for optimization of the complete radial distribution of the geometry, since the variables chosen to represent the three-dimensional geometry of the stage are coefficients of suitable polynomials. Evaluation of the objective function is obtained with a throughflow calculation, which has acceptable speed and stability qualities. Some examples are given of the possibility to use the procedure both for redesign and, together with what was presented in Part I, for the complete design of axial-flow compressor stages.

Axial Flow Compressor Design Optimization: Part I—Pitchline Analysis and Multivariable Objective Function Influence

The design of an axial flow compressor stage has been formulated as a nonlinear mathematical programming problem with the objective of minimizing the aerodynamic losses and the weight of the stage, while maximizing the compressor stall margin. Aerodynamic as well as mechanical constraints are considered in the problem formulation. A method of evaluating the objective function and constraints of the problem with a pitchline analysis is presented. The optimization problem is solved by using the penalty function method in which the Davidon-Fletcher-Powell variable metric minimization technique is employed. Designs involving the optimization of efficiency, weight of the stage, and stall margin are presented and the results discussed with particular reference to a multivariable objective function.

Classroom Analysis and Design of Axial Flow Compressors Using a Streamline Analysis Model

Article Classroom Analysis and Design of Axial Flow Compressors Using a Streamline Analysis Model was published on December 1, 1987 in the journal International Journal of Turbo & Jet-Engines (volume 4, issue 3-4).

Blade Design of Axial-Flow Compressors by the Method of Optimal Control Theory—Physical Model and Mathematical Expression

In the design of compressor blades we put forward an optimization flow-type problem which enables the designers to consider the optimization of specified performance index of the flow-type characteristics, such as that of work or efficiency of a compressor stage. The method of the diffusion factor flow-type design (DFFTD), presented by the authors [1], is taken here as a physical model. On the basis of optimal control theory a mathematical model of the optimal flow-type problem has been established and further recast into a typical form of optimal control problem with free initial conditions, terminal constraints, and state variable inequality constraints.

Blade Design of Axial-Flow Compressors by the Method of Optimal Control Theory—Application of Pontryagin’s Maximum Principles, a Sample Calculation and Its Results

Using the continual transformation technique [3] and the augmented penalty function method, the typical optimal control problem with various constraints proposed in the paper [2] has been converted to a new equivalent optimal control problem with no constraint. This enables the application of Pontryagin ’s maximum principle. Further, by means of the conjugate gradient method an example of the calculation is shown and the corresponding program is developed. A satisfactory optimal diffusion factor distribution has been obtained.

Numerical design of transonic cascades

The method developed by Bauer, Garabedian, and Korn (“Supercritical wing Sections,” Springer-Verlag, Berlin 1975) for the design of wing sections that exhibit shock-free flow at high subsonic speeds has been applied to the problem of cascade design. A cascade is a periodic distribution of two-dimensional blade cross sections that serves as a basis for the design of axial flow compressors and turbines. Those aspects of the design procedure that are used for both airfoil and cascade design are reviewed briefly in this paper. Emphasis has been placed on the differences between airfoil and cascade design. In particular, the form of the singular solution in the hodograph plane is different in the two cases.

Study of Casing Treatment Effects in Axial Flow Compressors

The phenomenon of surge in an axial flow compressor has long eluded the analytical fluid dynamist. In the recent years, a growing degree of improvement and sophistication in the design of axial flow compressors to achieve higher pressure ratios has resulted in increasingly narrow domains of stable operation. A search for improving stability margins revealed the importance of the blade tip region and casing treatments. The authors have approached the problem by both experimental and analytical methods. The results are mutually confirming. Important new inroads have been made in understanding the flow in the blade tip region, operation of casing treatments and the mechanism of the onset of surge. Some significant conclusions in the selection and design of casing treatments and their effects on the stability margin are presented and explained on the basis of experimental and theoretical results.

Paper 6: Recent Developments in the Aerodynamic Design of Axial Flow Compressors

Work on subsonic compressors is reviewed and traditional British and American methods of design are compared. Transonic compressors are now well established and recent progress, demonstrating the necessity for properly shaped blades in machines having high tip speeds, is examined. Advances in the computer-aided design of turbomachinery are described: these include the ‘Matrix through-flow’ and ‘Streamline curvature’ methods of calculating the meridional flow. Experimental results give preliminary confirmation of a method of annulus wall boundary layer prediction. Finally, current and future developments are discussed and an attempt is made to describe how an axial flow compressor may be designed a decade hence.

Recent Progress in Aerodynamic Design of Axial-Flow Compressors in the United States

This paper reviews recent trends in the United States in the aerodynamic design of axial-flow compressor components. A summary of design procedures used prior to 1955 is followed by discussion of subsequent improvements in the flow model, the velocity-diagram selection problem and methods for the selection or design of optimum blading. Recent investigations concerned with off-design performance, Reynolds number, scale and blade aspect ratio, and the influence that these investigations have had on design technique are considered. In conclusion, some important current problems in the design of axial-flow compressors are outlined.

An Improved Axial Flow Compressor Design

In using the method of stage stacking to compute the off-design performance of multi-stage axial compressors, it has been observed that the limitation on performance at speeds above the design speed has been set by the stall and the choke points of the rear stages(1). Thus if the rear stages can absorb a wide range of mass flows between stalled conditions and choked conditions, a better performance could be obtained.Compressor stages using low stagger blades will absorb a large range of mass flow between stalled and choked condition; but because of the high axial velocity involved in their use, they tend to be unsuitable for low pressure stages because of the high Mach number obtained. In the higher pressure stages the increased gas temperature will lower the Mach number for the same velocity and give more efficient operation.

Sweep and Dihedral Effects in Axial-Flow Turbomachinery

An approximate method for including the effects of sweep and dihedral when designing axial-flow turbomachinery blading is presented. Blades are said to have sweep when the flow direction is not perpendicular to the spanwise direction, and dihedral when the blade surface is not normal to the surface of an end wall. It is shown that blade cross sections should be cut by sectioning surfaces that are tangent to the axisymmetric stream surfaces of the meridional flow, but that these cross sections should be viewed by looking parallel to the axis (stacking line) of the blade. When this is done the observed blade shapes and flow angle distributions are most nearly comparable to those obtained from two-dimensional cascade experiments and analyses. This approach is found to be inadequate at the blade ends, however, and an analytical method is presented which yields a wall correction for blade rows of semi-infinite span. For all practical variations of the parameters involved in the design of axial-flow compressors and turbines, the wall correction can be conveniently calculated from a set of approximate formulas presented in this paper. The importance of an adequate axisymmetric solution (method not presented herein) as the first step in the analysis is pointed out; many of the effects of sweep and dihedral are traceable to the skewness of the force and thickness-blockage fields of the axisymmetric model. Finally, the paper summarizes the blading design procedure and applies the present work within the framework of the overall design. As an example, the method is used to design a swept cascade; previously reported test results for a similar cascade tend to substantiate the validity of the design procedure, but experimental results for a direct comparison with the theory are not available.

Annulus Wall Boundary Layers in Axial Compressor Stages

An analytical and experimental study is made of the development of secondary vorticities through the successive blade rows of a turbomachine. Whereas in cascade experiments the streamwise vorticity is usually zero at entry to the cascade, in the turbomachine this vorticity is in general nonzero and must be taken into account in the calculation of the secondary vorticity at exit from a blade row. In the calculation of boundary layer velocity profiles through an axial flow compressor stage, the variations in the exit air angles from the rows are computed first, from estimates of the secondary vorticities. There will always be overturning at the exit from the guide vane tip section, but tracing of the vorticity vectors through the machine shows that there may be underturning at rotor and stator tip. The exit air angles obtained from the analysis of these secondary flows may be used, together with actuator disk theory, to calculate axial velocity profiles in the boundary layers. It is suggested that this method of calculating the flow in the regions near the annulus walls should be used in the design of axial flow compressors.

Noise Characteristics from Axial Flow Compressors

The conventional methods of design of axial flow compressors usually consider the losses introduced by the generation of noise to be of negligible magnitudes and therefore ignore them entirely in a study of compressors. As a result, there is scant information on the relation between the noise level and the performance properties of compressors. In the present paper an attempt is made at working out the basis of a method of evaluation of the noise characteristics from compressors. The method makes considerable use of the experimental findings of Beranek and Rudmose on noise due to airplane propellers. The analysis presented here considers the noise to be generated by a number of point sources of equal magnitudes but of random phase. The resultant intensity level of these point sources (presumed to be located at the tip of the compressor blades) is calculated on a statistical basis. The expected noise level is given as a function of blade tip speed, clearance between blades and stator case, number of blades and the power expended in driving the compressor.