Performance Calculation of a Multi-Stage Axial Compressor through a Semi-Empirical Modelling Framework

A mean-line compressor performance calculation method is presented that covers the entire operating range, including the choked region of the map. It can be directly integrated into overall engine performance models, as it is developed in the same simulation environment. The code materializing the model can inherit the same interfaces, fluid models, and solvers, as the engine cycle model, allowing consistent, transparent, and robust simulations. In order to deal with convergence problems when the compressor operates close to or within the choked operation region, an approach to model choking conditions at blade row and overall compressor level is proposed. The choked portion of the compressor characteristics map is thus numerically established, allowing full knowledge and handling of inter-stage flow conditions. Such choking modelling capabilities are illustrated, for the first time in the open literature, for the case of multi-stage compressors. Integration capabilities of the 1D code within an overall engine model are demonstrated through steady state and transient simulations of a contemporary turbofan layout. Advantages offered by this approach are discussed, while comparison of using alternative approaches for representing compressor performance in overall engine models is discussed.

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Transonic Axial Compressors Loss Correlations: Part I — Analysis and Update of Loss Models

Volume 2A: Turbomachinery ◽

10.1115/gt2020-14713 ◽

2020 ◽

Author(s):

Marco Manfredi ◽

Fabrizio Fontaneto

Keyword(s):

Axial Compressor ◽

Reduced Order ◽

Axial Compressors ◽

Analysis And Design ◽

Main Driver ◽

Validity Range ◽

Loss Models ◽

Generation Mechanisms ◽

Semi Empirical ◽

System Designs

Abstract The quest for greener, more efficient aircraft engines is the main driver for the development of innovative compression system designs. Reduced order design tools rely nevertheless on semi-empirical loss models, whose validity range is often not net or in general not verified. The present work aims at defining a set of loss correlations, which could readily be employed in the analysis and design process of modern transonic axial compressors. In part I, the main entropy generation mechanisms are described together with a review of the most commonly employed modelling approaches. Selected loss models are then deeper investigated and updated to increase both their range of validity and the accuracy of their predictions. In Part II, the effectiveness of the investigated models will be tested for one specific low aspect ratio axial compressor stage.

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Simplified Method for Flow Analysis and Performance Calculation Through an Axial Compressor

Volume 1: Turbomachinery ◽

10.1115/84-gt-250 ◽

1984 ◽

Cited By ~ 1

Author(s):

Hubert Miton ◽

Youssef Doumandji ◽

Jacques Chauvin

Keyword(s):

Equations Of Motion ◽

Computing Time ◽

Flow Analysis ◽

Axial Compressor ◽

Computation Method ◽

Duct Flow ◽

Axial Compressors ◽

Flow Through ◽

And Performance ◽

Performance Calculation

This paper describes a fast computation method of the flow through multistage axial compressors of the industrial type. The flow is assumed to be axisymmetric between the blade rows which are represented by actuator disks. Blade row losses and turning are calculated by means of correlations. The equations of motion are linearized with respect to the log of static pressure, whose variation along the radius is usually of limited extent for the type of machines for which the method has been developed. In each computing plane (i.e. between the blade rows) two flows are combined: a basic flow with constant pressure satisfying the mass flow requirements and a perturbation flow fulfilling the radial equilibrium condition. The results of a few sample calculations are given. They show a satisfactory agreement with a classical duct flow method although the computing time is reduced by a factor five. The method has also been coupled with a surge line prediction calculation.

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Progress in semi-empirical modelling of main-sequence stellar chromospheres

Symposium - International Astronomical Union ◽

10.1017/s0074180900083571 ◽

1996 ◽

Vol 176 ◽

pp. 547-555

Author(s):

E.R. Houdebine

Keyword(s):

Main Sequence ◽

Radiation Transfer ◽

Research Programme ◽

Significant Progress ◽

Wave Dissipation ◽

Empirical Modelling ◽

Spectral Signatures ◽

Outer Atmosphere ◽

Semi Empirical

We present the results of a long term research programme on the outer atmospheres of main-sequence dwarfs. Combining NLTE-radiation transfer calculations with high resolution spectroscopic observations have led to significant progress in understanding chromospheric physical properties and spectral signatures. We emphasize that in order to unravel the extremely complex physics of the outer atmosphere and its energy source, magnetic field and acoustic wave dissipation, one must isolate the influence of all stellar parameters.

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On the Application of Frequency-Domain Methods to Multistage Turbomachinery

Volume 2B: Turbomachinery ◽

10.1115/gt2015-42936 ◽

2015 ◽

Cited By ~ 4

Author(s):

Laura Junge ◽

Graham Ashcroft ◽

Peter Jeschke ◽

Christian Frey

Keyword(s):

Frequency Domain ◽

Time Domain ◽

Harmonic Balance ◽

Axial Compressor ◽

Harmonic Balance Method ◽

Nonlinear Frequency ◽

Solution Quality ◽

Multi Stage ◽

Frequency Domain Methods ◽

Blade Row

Due to the relative motion between adjacent blade rows the aerodynamic flow fields within turbomachinery are normally dominated by deterministic, periodic phenomena. In the numerical simulation of such unsteady flows (nonlinear) frequency-domain methods are therefore attractive as they are capable of fully exploiting the given spatial and temporal periodicity, as well as capturing or modelling flow nonlinearity. Central to the efficiency and accuracy of such frequency-domain methods is the selection of the frequencies and the circumferential modes to be resolved in simulations. Whilst trivial in the context of the simulation of a single compressor- or turbine-stage, the choice of solution modes becomes substantially more involved in multi-stage configurations. In this work the importance of mode scattering, in the context of the unsteady aerodynamic field, is investigated and quantified. It is shown that scattered modes can substantially impact the unsteady flow field and are essential for the accurate modelling of wake propagation within multistage configurations. Furthermore, an iterative approach is outlined, based on the spectral analysis of the circumferential modes at the interfaces between blade rows, to identify the dominant solution modes that should be resolved in the adjacent blade row. To demonstrate the importance of mode scattering and validate the approach for their identification the unsteady blade row interaction within a 4.5 stage axial compressor is computed using both the harmonic balance method and, based on a full annulus midspan simulation, a time-domain method. Through the inclusion of scattered modes it is shown that the solution quality of the harmonic balance results is comparable to that of the nonlinear time-domain simulation.

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Numerical simulation of the non-uniform flow in a full-annulus multi-stage axial compressor with the harmonic balance method

Advances in Mechanical Engineering ◽

10.1177/1687814019897213 ◽

2020 ◽

Vol 12 (3) ◽

pp. 168781401989721 ◽

Cited By ~ 1

Author(s):

Haiou Sun ◽

Meng Wang ◽

Zhongyi Wang ◽

Song Wang ◽

Franco Magagnato

Keyword(s):

Flow Field ◽

Harmonic Balance ◽

Axial Compressor ◽

Harmonic Balance Method ◽

Internal Flow ◽

Uniform Flow ◽

Experimental Results ◽

Balance Method ◽

Operating Characteristics ◽

Multi Stage

To improve the understanding of unsteady flow in modern advanced axial compressor, unsteady simulations on full-annulus multi-stage axial compressor are carried out with the harmonic balance method. Since the internal flow in turbomachinery is naturally periodic, the harmonic balance method can be used to reduce the computational cost. In order to verify the accuracy of the harmonic balance method, the numerical results are first compared with the experimental results. The results show that the internal flow field and the operating characteristics of the multi-stage axial compressor obtained by the harmonic balance method coincide with the experimental results with the relative error in the range of 3%. Through the analysis of the internal flow field of the axial compressor, it can be found that the airflow in the clearance of adjacent blade rows gradually changes from axisymmetric to non-axisymmetric and then returns to almost completely axisymmetric distribution before the downstream blade inlet, with only a slight non-axisymmetric distribution, which can be ignored. Moreover, the slight non-axisymmetric distribution will continue to accumulate with the development of the flow and, finally, form a distinct circumferential non-uniform flow field in latter stages, which may be the reason why the traditional single-passage numerical method will cause certain errors in multi-stage axial compressor simulations.

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Flow Characteristics of a Novel Centrifugal Compressor Design

Volume 2D: Turbomachinery ◽

10.1115/gt2016-58103 ◽

2016 ◽

Author(s):

Shashank Mishra ◽

Shaaban Abdallah ◽

Mark Turner

Keyword(s):

Centrifugal Compressor ◽

Pressure Ratio ◽

Flow Characteristics ◽

Axial Compressor ◽

Low Pressure ◽

Flow Path ◽

Optimization Techniques ◽

Single Stage ◽

Multi Stage ◽

Compressor Design

Multistage axial compressor has an advantage of lower stage loading as compared to a single stage. Several stages with low pressure ratio are linked together which allows for multiplication of pressure to generate high pressure ratio in an axial compressor. Since each stage has low pressure ratio they operate at a higher efficiency and the efficiency of multi-stage axial compressor as a whole is very high. Although, single stage centrifugal compressor has higher pressure ratio compared with an axial compressor but multistage centrifugal compressors are not as efficient because the flow has to be turned from radial at outlet to axial at inlet for each stage. The present study explores the advantages of extending the axial compressor efficient flow path that consist of rotor stator stages to the centrifugal compressor stage. In this invention, two rotating rows of blades are mounted on the same impeller disk, separated by a stator blade row attached to the casing. A certain amount of turning can be achieved through a single stage centrifugal compressor before flow starts separating, thus dividing it into multiple stages would be advantageous as it would allow for more flow turning. Also the individual stage now operate with low pressure ratio and high efficiency resulting into an overall increase in pressure ratio and efficiency. The baseline is derived from the NASA low speed centrifugal compressor design which is a 55 degree backward swept impeller. Flow characteristics of the novel multistage design are compared with a single stage centrifugal compressor. The flow path of the baseline and multi-stage compressor are created using 3DBGB tool and DAKOTA is used to optimize the performance of baseline as well novel design. The optimization techniques used are Genetic algorithm followed by Numerical Gradient method. The optimization resulted into improvements in incidence and geometry which significantly improved the performance over baseline compressor design. The multistage compressor is more efficient with a higher pressure ratio compared with the base line design for the same work input and initial conditions.

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AN EMPIRICAL MODELLING FRAMEWORK FOR FORECASTING FREIGHT TRANSPORTATION

Transport ◽

10.3846/16484142.2014.930927 ◽

2014 ◽

Vol 29 (2) ◽

pp. 185-194 ◽

Cited By ~ 6

Author(s):

Hakan Güler

Keyword(s):

Gross Domestic Product ◽

Survey Data ◽

Freight Transportation ◽

Statistical Techniques ◽

Regression Analyses ◽

Iterative Techniques ◽

Gravity Method ◽

Empirical Modelling ◽

Modelling Framework ◽

Modelling Methods

This paper presents a framework which includes empirical modelling methods to estimate freight transportation between defined zones. In this method, observed origin and destination matrices for each type of freight are constituted based on the link counts and the roadside truck survey data. The gravity method is selected to estimate origin and destination matrices by using observed link flows, gross domestic product by provinces and interzonal distances. Advanced statistical techniques and regression analyses are used to estimate the coefficients of the gravity method. The final freight transportation matrix is calibrated with the link flows data by using iterative techniques. The developed method was applied to find the origin and destination matrix of the total freight transportation in Turkey and successful results were obtained.

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Interception of radionuclides by planophile crops: A simple semi-empirical modelling approach in case of nuclear accident fallout

Environmental Pollution ◽

10.1016/j.envpol.2020.115308 ◽

2020 ◽

Vol 266 ◽

pp. 115308

Author(s):

A. Cristina ◽

R. Samson ◽

N. Horemans ◽

M. Van Hees ◽

J. Wannijn ◽

...

Keyword(s):

Nuclear Accident ◽

Empirical Modelling ◽

Semi Empirical ◽

Modelling Approach

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Structure and Propagation of Rotating Stall in a Single- and a Multi-Stage Axial Compressor

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

10.1115/99-gt-452 ◽

1999 ◽

Cited By ~ 2

Author(s):

H. M. Saxer-Felici ◽

A. P. Saxer ◽

F. Ginter ◽

A. Inderbitzin ◽

G. Gyarmathy

Keyword(s):

Numerical Solutions ◽

Equations Of Motion ◽

Axial Compressor ◽

Rotating Stall ◽

Water Model ◽

Two Stage ◽

Additional Information ◽

Driving Mechanisms ◽

Multi Stage ◽

Stall Cells

The structure and propagation of rotating stall cells in a single- and a two-stage subsonic axial compressor is addressed in this paper using computational and experimental analysis. Unsteady solutions of the 2-D inviscid compressible (Euler) equations of motion are presented for one operating point in the fully-developed rotating stall regime for both a single- and a two-stage compressor. The inviscid assumption is verified by comparing the single-stage 2-D in viscid/compressible solution with an equivalent 2-D viscous (Navier-Stokes) result for incompressible flow. The structure of the rotating stall cell is analyzed and compared for the single- and two-stage cases. The numerical solutions are validated against experimental data consisting of flow visualization and unsteady row-by-row static pressure measurements obtained in a four-stage water model of a subsonic compressor. The CFD solutions supply a link between the observed experimental features and provide additional information on the structure of the stall flow. Based on this study. supporting assumptions regarding the driving mechanisms for the propagation of fully-developed rotating stall cells and their structure are postulated. In methodical respect the results suggest that the inviscid model is able to reproduce the essentials of the flow physics associated with the propagation of fully-developed, full-span rotating stall in a subsonic axial compressor.

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