An Iterative Method for Blade Profile Loss Model Adaptation Using Streamline Curvature

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Vassilios Pachidis ◽  
Pericles Pilidis ◽  
Ioannis Templalexis ◽  
Luca Marinai
Keyword(s):  
Experimental Data ◽  
Flow Analysis ◽  
Public Domain ◽  
Model Adaptation ◽  
Blade Profile ◽  
Loss Model ◽  
Streamline Curvature ◽  
Through Flow ◽  
Loss Models ◽  
Profile Loss

The various incidence, deviation, and loss models used in through-flow analysis methods, such as streamline curvature, are nothing more than statistical curve fits. A closer look at public domain data reveals that these statistical correlations and curve fits are usually based on experimental cascade data that actually display a fairly large scatter, resulting in a relatively high degree of uncertainty. This usually leads to substantial differences between the calculated and actual performances of a given gas turbine engine component. Typically, matching calculated results from a through-flow analysis against experimental data requires the combination of various correlations available in the public domain, through a very tedious, complex, and time consuming “trial and error” process. This particular study supports the view that it might actually be much more time effective to “adopt” a given loss model against experimental data through an iterative, physics-based approach, rather than try to identify the best combination of available correlations. For example, the well-established “Swan’s model” for calculating the blade profile loss factor in subsonic and transonic axial flow compressors depends strongly on approximate correlations for calculating the blade wake momentum thickness, and therefore represents such a case. This study demonstrates this by looking into an iterative approach to blade profile loss model adaptation that can provide a relatively simple and quick, but also physics-based way of “calibrating” profile loss models against available experimental data for subsonic applications. This paper presents in detail all the analysis necessary to support the above concept and discusses Swan’s model in particular as an example. Finally, the paper discusses the performance comparison of a two-dimensional, streamline curvature compressor model against experimental data before and after the adaptation of that particular loss model. This analysis proves the potential of the simulation strategy presented in this paper to “adopt” a given loss model against experimental data through an iterative, physics-based approach.

An Iterative Method for Blade Profile Loss Model Adaptation Using Streamline Curvature

2007 ◽  
Author(s):  
Vassilios Pachidis ◽  
Pericles Pilidis ◽  
Ioannis Templalexis ◽  
Luca Marinai
Keyword(s):  
Experimental Data ◽  
Axial Flow ◽  
Public Domain ◽  
Performance Comparison ◽  
Model Adaptation ◽  
Blade Profile ◽  
Loss Model ◽  
Streamline Curvature ◽  
Loss Models ◽  
Profile Loss

The various incidence, deviation and loss models used in through-flow analysis methods, such as Streamline Curvature, are nothing more than statistical curve fits. A closer look at public domain data reveals that these statistical correlations and curve fits are usually based on experimental cascade data that actually display a fairly large scatter, resulting in a relatively high degree of uncertainty. This usually leads to substantial differences between the calculated and actual performances of a given gas turbine engine component. Typically, matching calculated results from a throughflow analysis against experimental data requires the combination of various correlations available in the public domain, through a very tedious, complex and time consuming ‘trial and error’ process. This particular study supports the view that it might actually be much more time-effective to “adopt” a given loss model against experimental data through an iterative, physics-based approach, rather than try to identify the best combination of available correlations. For example, the well-established “Swan’s model” for calculating the blade profile loss factor in subsonic and transonic axial flow compressors depends strongly on approximate correlations for calculating the blade wake momentum thickness, and therefore represents such a case. This study demonstrates this by looking into an iterative approach to blade profile loss model adaptation that can provide a relatively simple and quick, but also physics-based way of ‘calibrating’ profile loss models against available experimental data for subsonic applications. This paper presents in detail all the analysis necessary to support the above concept and discusses Swan’s model in particular as an example. Finally, the paper discusses the performance comparison of a two-dimensional, Streamline Curvature compressor model against experimental data before and after the adaptation of that particular loss model.

Development of an Experimental Correlation for Transonic Turbine Flow

1987 ◽  
Vol 109 (2) ◽  
pp. 246-250 ◽  
Author(s):  
F. Martelli ◽  
A. Boretti
Keyword(s):  
Experimental Data ◽  
Operating Conditions ◽  
Geometric Parameters ◽  
Blade Profile ◽  
Profile Losses ◽  
Experimental Correlation ◽  
Transonic Turbine ◽  
The Relationship ◽  
Profile Loss ◽  
Correlation Procedure

Optimization of transonic turbine bladings over a broad range of operating conditions calls for better understanding of the relationship between blade profile loss and cascade geometric parameters. In fact, many of the experimental correlations published to date have failed to take into due consideration transonic effects, while others have considered far too few of the numerous geometric parameters affecting profile loss in transonic flows. Through examination of the experimental data gathered by some 20 authors regarding the effects of the most significant blading geometric parameters on profile losses, a loss correlation procedure has been developed. The procedure is especially advantageous in that it allows continuous updating as new experimental data become available.

New Profile Loss Model for Improved Prediction of Transonic Axial Flow Compressor Performance in Choking Region

2015 ◽  
Author(s):  
Sangjo Kim ◽  
Donghyun Kim ◽  
Kuisoon Kim ◽  
Changmin Son ◽  
Myungho Kim ◽  
...  
Keyword(s):  
Performance Prediction ◽  
Incidence Angle ◽  
Axial Flow ◽  
Operating Conditions ◽  
Loss Model ◽  
Axial Flow Compressor ◽  
Compressor Performance ◽  
Loss Models ◽  
Flow Compressor ◽  
Profile Loss

New off-design profile loss models have been developed by performing thorough investigations on compressor performance prediction using one-dimensional stage-stacking approach and three-dimensional computational flow dynamics (CFD) results. Generally, a loss model incorporating various compressor geometry and operating conditions is required to predict the performance of various types of compressors. In this study, three sets of selected loss models were applied to predict axial flow compressor performance using stage-stacking approach. The results were compared with experimental data as well as CFD results. The comparison shows an interesting observation in choking region where the existing loss models cannot capture the rapid decrease in pressure and efficiency while CFD predicted the characteristics. Therefore, an improved off-design profile loss model is proposed for better compressor performance prediction in choking region. The improved model was derived from the correlation between the normalized total loss and the incidence angle. The choking incidence angle, which is a major factor in determining the off-design profile loss, was derived from correlations between the inlet Mach number, throat width-to-inlet spacing ratio, and minimum loss incidence angle. The revised stage-stacking program employing new profile loss model together with a set of loss models was applied to predict a single and multistage compressors for comparison. The results confirmed that the new profile loss model can be widely used for predicting the performance of single and multistage compressor.

A Centrifugal Compressor Flow Analysis Employing a Jet-Wake Passage Flow Model

1977 ◽  
Vol 99 (1) ◽  
pp. 141-147 ◽  
Author(s):  
J. H. G. Howard ◽  
C. Osborne
Keyword(s):  
Centrifugal Compressor ◽  
Curve Fitting ◽  
Flow Model ◽  
Flow Analysis ◽  
Stagnation Pressure ◽  
Centrifugal Impeller ◽  
Experimental Measurements ◽  
Suction Surface ◽  
Streamline Curvature ◽  
Through Flow

The streamline curvature through-flow analysis of a centrifugal impeller passage flow has been modified to include a flow model with a wake on the suction surface. With this model, empirically determined or measured impeller conditions can be matched without requiring a distributed stagnation pressure loss within the passage. Its use in impeller design is presented and comparison with experimental measurements from two impellers illustrate the utility of this approach. A brief discussion of experience with the associated forms of curve fitting and streamline smoothing required for the analysis solution is included.

scholarly journals Extended Windage Loss Models for Gas Bearing Supported Spindles Operated in Dense Gases

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Kévin Rosset ◽  
Jürg Schiffmann
Keyword(s):  
Experimental Data ◽  
Turbulent Flow ◽  
High Speed ◽  
Skin Friction Coefficient ◽  
Air Gap ◽  
Operating Pressure ◽  
Rotating Disks ◽  
Loss Model ◽  
Flow Loss ◽  
Loss Models

Abstract Generic models are proposed to evaluate the skin friction coefficient acting on enclosed rotating disks and cylinders under various flow regimes. In particular, a model taking into account the inner radius of the disk is developed. The models are compared with experimental data obtained from coast-down tests of a high-speed spindle supported on gas lubricated bearings, operated in air and in halocarbon R245fa at various pressures. The windage losses are first computed considering state-of-the-art laminar flow loss models in the gas bearings and an experimentally validated laminar-turbulent flow loss model in the air gap. This reference approach predicts the air data with a good accuracy (deviation less than 5%) but underestimates the organic fluid data by up to 36%. This deviation is considerably reduced (max 6.8%) when applying the proposed multiflow regime loss model for enclosed rotating disks to the thrust bearing. Finally, the proposed laminar-turbulent flow loss model for enclosed rotating cylinders is simultaneously applied to the journal bearings and the air gap. A peak deviation of 6.5% is maintained among all test cases when setting the critical Taylor number to an artificial value (67) instead of the theoretical value (41.1) characterizing the onset of growth of Taylor vortices. Taking into account the uncertainties on the bearing clearances, as well as on the operating pressure and temperature, a ±10% agreement with the experimental data is obtained.

An Integrated Throughflow Method for the Performance Analysis of Variable Cycle Compression Systems

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Baojie Liu ◽  
Shaofeng Jia ◽  
Xianjun Yu
Keyword(s):  
Experimental Data ◽  
Performance Analysis ◽  
Minimum Loss ◽  
Matching Problems ◽  
Compression System ◽  
Streamline Curvature ◽  
Control Rules ◽  
Component Matching ◽  
Loss Models ◽  
Streamline Curvature Method

Abstract A streamline curvature method based integrated throughflow analysis approach is newly developed to deal with component matching problems of variable cycle compression systems. The construction of variable cycle compression system is modularly modelled in the procedure. Splitting and confluent flow are elaborately disposed. A numerical method based on the “streamline floating” character of streamline curvature method is developed to model the function of forward variable area bypass injector. Moreover, extensive models used in the throughflow calculations, including minimum loss incidence, deviation and loss models were assessed, selected and modified. Finally, code validations were conducted on three representative traditional compressors, i. e. NASA rotor 67, NASA stage 37 and a custom-designed low-speed repeating four-stage compressor. Both the predicted overall characteristics and spanwise profiles agree reasonably well with the experimental data. The validated procedure was finally used to sketch the performance maps of a double bypass compression system under two different control rules, i. e. the first bypass throttling and the second bypass throttling. The results show some aspects of the difficulties and complications in operating a variable cycle compression system, and meanwhile, demonstrate the superiority of the newly developed integrated throughflow method.

The Uniqueness of Turbomachinery Flow Calculations Using the Streamline Curvature and Matrix Through-Flow Methods

1971 ◽  
Vol 13 (6) ◽  
pp. 376-379 ◽  
Author(s):  
H. Marsh
Keyword(s):  
Mach Number ◽  
Flow Pattern ◽  
Iterative Procedure ◽  
Flow Analysis ◽  
Alternative Procedure ◽  
Streamline Curvature ◽  
Through Flow ◽  
The Matrix ◽  
Uniqueness Of The Solution ◽  
Flow Through

When calculating the flow through turbomachines by an iterative procedure, it is assumed that on each cycle of iteration there is only one solution for the flow pattern. The uniqueness of the solution obtained by the method of streamline curvature is examined and a set of Mach number conditions are derived which are sufficient to ensure that the flow pattern is unique. The Mach number limitations are the same as those which are necessary to avoid ambiguity in the matrix through-flow analysis. An alternative procedure is then described in which the solution for the flow pattern is always unique.

A Shock Loss Model for Supersonic Compressor Cascades

1999 ◽  
Vol 121 (1) ◽  
pp. 28-35 ◽  
Author(s):  
G. S. Bloch ◽  
W. W. Copenhaver ◽  
W. F. O’Brien
Keyword(s):  
Mach Number ◽  
Boundary Layer Separation ◽  
Navier Stokes ◽  
Flow Angle ◽  
Loss Model ◽  
Viscous Profile ◽  
Loss Models ◽  
Profile Loss ◽  
Shock Loss ◽  
Good Agreement

Loss models used in compression system performance prediction codes are often developed from the study of two-dimensional cascades. In this paper, compressible fluid mechanics has been applied to the changes in shock geometry that are known to occur with back pressure for unstarted operation of supersonic compressor cascades. This physics-based engineering shock loss model is applicable to cascades with arbitrary airfoil shapes. Predictions from the present method have been compared to measurements and Navier–Stokes analyses of the LO30-4 and L030-6 cascades, and very good agreement was demonstrated for unstarted operation. A clear improvement has been demonstrated over previously published shock loss models for unstarted operation, both in the accuracy of the predictions and in the range of applicability. The dramatic increase in overall loss with increasing inlet flow angle is shown to be primarily the result of increased shock loss, and much of this increase is caused by the detached bow shock. For a given Mach number, the viscous profile loss is nearly constant over the entire unstarted operating range of the cascade, unless a shock-induced boundary layer separation occurs near stall. Shock loss is much more sensitive to inlet Mach number than is viscous profile loss.

Empirical path loss models at 433 MHz in Himalayan snow for health monitoring

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Rajesh Kumar Garg ◽  
Surender Kumar Soni
Keyword(s):  
Experimental Data ◽  
Health Monitoring ◽  
Path Loss ◽  
Sensor Nodes ◽  
Wireless Sensor ◽  
Third Order ◽  
Wireless Sensor Nodes ◽  
Loss Model ◽  
Content Type ◽  
Loss Models

Purpose The purpose of this paper is to investigate the effect of snow on the radio link performance of wireless sensor nodes in Indian Himalayan conditions and to propose empirical path loss models for radio wave propagation. Design/methodology/approach At the remote test site, one source and three listening wireless sensor nodes were deployed at frequency of 433 MHz. The path loss models are derived from experimental data collected during the period of snowfall and clear weather conditions. Linear, exponential, second and third-order polynomials path loss models have been investigated along with experimental data. Findings With the help of curve fitting and goodness-of-fit tests, it is found that path loss can be modelled through third-order polynomial equation during the snowfall period. However, if sensor is buried, the acceptable path loss model is exponential. Similarly, for unified modelling requirement, exponential path loss model over linear can be a preferred choice. Originality/value Results show that path loss can be estimated priori for deciding optimum transmission energy in wireless sensor network. Presented work is usable in extending the lifetime of health monitoring devices buried in snowy environment.

The Effects of Wake Mixing on Compressor Aerodynamics

1990 ◽  
Author(s):  
Robert P. Dring ◽  
David A. Spear
Keyword(s):  
Experimental Data ◽  
Secondary Flow ◽  
Flow Analysis ◽  
Strong Impact ◽  
Corner Separation ◽  
Pressure Distributions ◽  
Through Flow ◽  
Compressor Aerodynamics ◽  
Airfoil Flow

A methodology based on wake mixing has been developed that enables more accurate predictions of compressor airfoil pressure distributions when the airfoil is operating downstream of an airfoil row that has strong wakes. The methodology has an impact on through–flow analysis, on airfoil–to–airfoil flow analysis, and on the interpretation of experimental data. It is demonstrated that the flow in the endwall region is particularly sensitive to mixing due to the strong wakes caused by the secondary flow and corner separation that commonly occur in this region. It is also demonstrated that wake mixing can have a strong impact on both airfoil incidence and deviation as well as on loading. Differences of up to 13° and 30% in loading are demonstrated.

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