Theoretical Study of Flow Instabilities and Inlet Distortions in Axial Compressors

1982 ◽  
Vol 104 (3) ◽  
pp. 715-721 ◽  
Author(s):  
P. Ferrand ◽  
J. Chauvin
Keyword(s):  
Theoretical Study ◽  
Rotating Stall ◽  
Time Dependent ◽  
Flow Instabilities ◽  
Axial Compressors ◽  
Independent Variables ◽  
Servo Mechanism ◽  
Dependent Variables ◽  
Multistage Compressors ◽  
Method Of Evaluation

This paper describes a method of evaluation of the single and multistage compressors response to steady and unsteady inlet distortions. It allows also the evaluation of the appearance of unstable regimes and their characterization (rotating stall and surge). It is based on a linearized approach using mean line calculations. The compressor is considered as a series of vaned and vaneless spaces, and the corresponding equations are solved by use of Fourier series for time independent variables and by Laplace’s transform for time-dependent variables. An analogy between the compressor’s response and a servo-mechanism is developed, using Nyquist’s diagram. Results are compared with experimental data which prove the validity of the approach. A parametric study indicates which parameters can be modified to improve the flow stability.

Theoretical Study of Flow Instabilities and Inlet Distortions in Axial Compressors

1981 ◽  
Author(s):  
P. Ferrand ◽  
J. Chauvin
Keyword(s):  
Theoretical Study ◽  
Rotating Stall ◽  
Time Dependent ◽  
Flow Instabilities ◽  
Axial Compressors ◽  
Independent Variables ◽  
Servo Mechanism ◽  
Dependent Variables ◽  
Multistage Compressors ◽  
Method Of Evaluation

This paper describes a method of evaluation of the single and multistage compressors response to steady and unsteady inlet distortions. It allows also the evaluation of the appearance of unstable regimes and their characterization (rotating stall and surge). It is based on a linearized approach using mean line calculations. The compressor is considered as a serie of vaned and vaneless spaces, and the corresponding equations are solved by use of Fourier series for time independent variables and by Laplace’s transform for time dependent variables. An analogy between the compressor’s response and a servo-mechanism is developed, using Nyquist’s diagram. Results are compared with experimental data which prove the validity of the approach. A parametric study indicates which parameters can be modified to improve the flow stability.

Numerical Simulation of Flow Instabilities in High Speed Multistage Compressors

2010 ◽  
Author(s):  
Huan Zhang ◽  
Jun Hu ◽  
Baofeng Tu ◽  
Zhiqiang Wang
Keyword(s):  
High Speed ◽  
Rotating Stall ◽  
Flow Instabilities ◽  
Two Dimensional ◽  
Duct Flow ◽  
Disk Model ◽  
Stall Inception ◽  
Axial Compressors ◽  
Multistage Compressors ◽  
The Stability

In the present paper, a nonlinear multi “actuator disk” model is proposed to analyze the dynamic behavior of flow instabilities, including rotating stall and surge, in high speed multistage axial compressors. The model describes the duct flow fields using two dimensional, compressible and unsteady Euler equations, and accounts for the influences of downstream plenum and throttle in the system as well. It replaces each blade row of multistage compressors with a disk. For numerical calculations, the time marching procedure, using MacCormack two steps scheme, is used. The main purpose of this paper is to predict the mechanism of two dimensional short wavelength rotating stall inception, the interaction between blade rows in high speed multistage compressors and the influence of rotating inlet distortion on the stability. It has been demonstrated that the model has the ability to predict those phenomena, and the results show that some system parameters have a strong effect on the stall features as well. Results for a five stage high speed compressor are analyzed in detail, and comparison with the experimental data demonstrates that the model and calculating results are reliable.

Detection of Precursor Waves Announcing Stall in Two 3-Stage Axial Compressors

1998 ◽  
Author(s):  
F. Grauer ◽  
W. Volgmann ◽  
H. Stoff ◽  
T. Breuer
Keyword(s):  
Pressure Fluctuations ◽  
Safety Margin ◽  
Stability Limit ◽  
Rotating Stall ◽  
Time Dependent ◽  
Axial Compressors ◽  
Performance Map ◽  
Fourier Transform Methods ◽  
The Stability ◽  
Stall Control

Rotating stall and surge limit the operating range of a compressor towards low throughflow and high pressure in the performance map. Usually a safety margin must be observed to prevent the compressor from entering unintentionally aerodynamic instabilities. As the range of highest performance and efficiency lies in the vicinity of the stability limit, efforts concentrate on recognizing imminent onset of unstable operation prior to its occurrence. The present investigation centers on means of detecting information about onsetting instability from signals of pressure fluctuations in two transonic medium-pressure axial compressors of 3 stages. Fourier-transform-methods as well as artificial neural networks are applied for the data reduction of the time-dependent pressure signals. The methods of investigation presented here detected stall precursors announcing the onset of instability. Some of them seem appropriate to be used in connection with active stall control.

scholarly journals Stalled Flow Performance for Axial Compressors: I — Axisymmetric Characteristic

1984 ◽  
Author(s):  
S. G. Koff ◽  
E. M. Greitzer
Keyword(s):  
Flow Model ◽  
Flow Characteristic ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Reversed Flow ◽  
Axial Compressors ◽  
Point Pressure ◽  
Multistage Compressors ◽  
Entire Flow ◽  
Stagger Angle

A study of stalled flow performance of multistage compressors is presented. A new compressor characteristic is developed, describing the axisymmetric pumping performance over the entire compressor flow range, including reversed flow. This axisymmetric characteristic is required in any current rotating stall model. It is possible for the axisymmetric performance to rise above the measured stall point pressure rise, thus indicating greater unstalled pressure rise potential. In this context, the axisymmetric characteristic in forward flow is viewed as paralleling diffuser performance. A simple two-dimensional reversed flow model is presented, and is shown to be in reasonable agreement with available high backflow compressor data. The model predicts that the blade stagger angle greatly influences the reversed flow characteristic. Calculations are carried out using the rotating stall model of Moore and the axisymmetric characteristic developed herein, and a technique is suggested for estimating the axisymmetric curve over the entire flow range.

scholarly journals Prediction of Small Rotating Stall in Axial Compressors Using Actuator Disc Theory

1985 ◽  
Author(s):  
K. Mathioudakis
Keyword(s):  
Experimental Data ◽  
Perturbation Analysis ◽  
Theoretical Study ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Mean Flow ◽  
Axial Compressors ◽  
Blade Row ◽  
Rotating Reference Frame ◽  
Actuator Disc

A theoretical study of the development of rotating stall in axial compressors is presented. A small perturbation analysis is used for this purpose. The compressor is considered as a series of vaneless spaces and blade rows. The axisymmetric mean flow is of the free vortex type and blade rows are represented as actuator discs. The perturbations are three dimensional and steady with respect to a rotating reference frame. For high hub-tip ratio annuli the transfer relations for the perturbations are expressed in a matrix form. This formulation allows the prediction of the occurrence and development of rotating stall in single or multiple blade row configurations. The results of the prediction compare favourably with experimental data.

scholarly journals Stalled Flow Performance for Axial Compressors: II — Rotating Stall Characteristic

1984 ◽  
Author(s):  
S. G. Koff
Keyword(s):  
Rotating Stall ◽  
Flow Mode ◽  
Thin Shells ◽  
System Behavior ◽  
Stall Inception ◽  
Compression System ◽  
Axial Compressors ◽  
System Parameters ◽  
Multistage Compressors ◽  
The Impact

This paper describes a study of stalled flow performance of multistage compressors. The study is focused on the performance in rotating stall, in particular, the impact on stall inception and stall recovery. It is argued that the recovery point measured in post-stall compressor tests results from a compression system instability, rather than from an unstable rotating stall flow. If so, recoverability from rotating stall may be improved by altering system parameters. Furthermore, the full-span rotating stall characteristic is extrapolated beyond the measured recovery point. On this basis, the compressor stall point is viewed as a bifurcation, where a change in flow mode exists, perhaps analogous to the critical point in the axial compression of thin shells. An application for the extended rotating stall characteristic is in a model of transient compression system behavior.

ANALISA PENGARUH IKLIM ORGANISASI DAN KOMPETENSI TERHADAP KINERJA PEGAWAI PT HUTAMA KARYA

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Erik Wardhana, MM.
Keyword(s):  
Organizational Climate ◽  
Employee Performance ◽  
Sampling Technique ◽  
Simple Random Sampling ◽  
Free Variable ◽  
Independent Variables ◽  
Dependent Variables ◽  
Correlational Approach ◽  
Survey Research Methods ◽  
The Relationship

This study entitled "Analysis of Effect of Climate Organization and Competence Againt Employee PT. Hutama Karya ". The purpose of this study was to obtain information on the relationship between the free variable that organizational climate (X1) and competence (X2) with the dependent variable is employee performance (Y), either partially or simultaneously, This study used survey research methods with the correlational approach and predictive, which aims for the relationship and influence between independent and dependent variables. The sampling technique can be done randomly (simple random sampling) of 852 employees, which is considered to resprentatif is 89 people. And to solve problems, to analyze and examine the relationship and influence between the independent variables on the dependent variable used models kausalistik through regression analysis with SPSS 14.0

PENGARUH PERSONAL BACKGROUND, POLITICAL BACKGROUND DAN PENGEATAHUAN DEWAN TENTANG ANGGARAN TERHADAP PERAN DPRD DALAM PENGAWASAN KEUANGAN DAERAH

2008 ◽  
Author(s):  
Yesi Mutia Basri ◽  
Rosliana Rosliana
Keyword(s):  
Multivariate Analysis ◽  
Significant Influence ◽  
Political Activity ◽  
Primary Data ◽  
Financial Control ◽  
Independent Variables ◽  
Dependent Variables ◽  
Political Background ◽  
Activity Dependent

This research aim to examine the influence of personal background, political background, and council budget knowledge towards the role of DPRD on region financial control. This research is motivated by the fact that individual background will effect to individual behavior on political activity. Dependent variables in this research are personal background, political background, and council budges knowledge towards the role of DPRD on region financial control Independent variables are the role of DPRD on region financial control in planning, implementing, and responsibility steps. The data in this research consist of primary data that taken from questionnaires distributed directly to respondents. The collected are from 34 Respondents that members of DPRD at Pekanbaru. Hypothesis of this research are examine by using Multivariate Analysis of Variances (MANOVA). The result of this research HI personal background political background and budget knowledge have significant influence toward the role of DPRD on region financial control in planning steps.H2 personal background, politico I background and budget knowledge have no significant influence toward the role of DPRD on region financial control in Implementing steps. H3 personal background political background and budget knowledge have no significant influence toward the role of DPRD on region financial control in Controlling steps.

scholarly journals Weight Feedback-Based Harmonic MDG-Ensemble Model for Prediction of Traffic Accident Severity

2021 ◽  
Vol 11 (11) ◽  
pp. 5072
Author(s):  
Byung-Kook Koo ◽  
Ji-Won Baek ◽  
Kyung-Yong Chung
Keyword(s):  
Traffic Accidents ◽  
Average Rate ◽  
Modern Society ◽  
Rate Of Change ◽  
Weighted Voting ◽  
Independent Variables ◽  
Dependent Variables ◽  
Accident Severity ◽  
Harmonic Average ◽  
Bagging Method

Traffic accidents are emerging as a serious social problem in modern society but if the severity of an accident is quickly grasped, countermeasures can be organized efficiently. To solve this problem, the method proposed in this paper derives the MDG (Mean Decrease Gini) coefficient between variables to assess the severity of traffic accidents. Single models are designed to use coefficient, independent variables to determine and predict accident severity. The generated single models are fused using a weighted-voting-based bagging method ensemble to consider various characteristics and avoid overfitting. The variables used for predicting accidents are classified as dependent or independent and the variables that affect the severity of traffic accidents are predicted using the characteristics of causal relationships. Independent variables are classified as categorical and numerical variables. For this reason, a problem arises when the variation among dependent variables is imbalanced. Therefore, a harmonic average is applied to the weights to maintain the variables’ balance and determine the average rate of change. Through this, it is possible to establish objective criteria for determining the severity of traffic accidents, thereby improving reliability.

scholarly journals A Student’s Guide to the Classification and Operationalization of Variables in the Conceptualization and Design of a Clinical Study: Part 1

2021 ◽  
Vol 43 (2) ◽  
pp. 177-179 ◽  
Author(s):  
Chittaranjan Andrade
Keyword(s):  
Clinical Study ◽  
Significant Relationship ◽  
Research Experience ◽  
Process Variables ◽  
Know How ◽  
Independent Variables ◽  
Cause And Effect ◽  
Confounding Variables ◽  
Dependent Variables ◽  
The Relationship

Students without prior research experience may not know how to conceptualize and design a study. This article explains how an understanding of the classification and operationalization of variables is the key to the process. Variables describe aspects of the sample that is under study; they are so called because they vary in value from subject to subject in the sample. Variables may be independent or dependent. Independent variables influence the value of other variables; dependent variables are influenced in value by other variables. A hypothesis states an expected relationship between variables. A significant relationship between an independent and dependent variable does not prove cause and effect; the relationship may partly or wholly be explained by one or more confounding variables. Variables need to be operationalized; that is, defined in a way that permits their accurate measurement. These and other concepts are explained with the help of clinically relevant examples.

Sign in / Sign up

Export Citation Format

Share Document