In-Engine Measurements of Temperature Rises in Axial Compressor Shrouded Stator Cavities

2002 ◽  
Author(s):  
Leo V. Lewis
Keyword(s):  
Temperature Rise ◽  
Mechanical Design ◽  
Rotational Velocity ◽  
Axial Compressor ◽  
Labyrinth Seals ◽  
Aerodynamic Efficiency ◽  
Axial Compressors ◽  
Higher Temperature ◽  
Mass Flows ◽  
Aero Engines

Although many axial compressors in large aero engines use shrouded stators to retain aerodynamic efficiency, the temperature rises generated within the stator well cavities can be detrimental to the mechanical design of the disc rim or the shroud itself. These temperature rises are poorly understood and have not been widely reported. This paper presents the temperature measurements from the HP compressor stator wells of full size development engine tests, concentrating on two particular tests for the majority of its information. It is shown how standard formulae for windage and mass flows on rotor discs and in labyrinth seals can, if suitably factored, explain the observed temperatures in the first test. Inferences are drawn regarding the windage losses in the compressor, in kW, and swirl velocities, as fractions of the disc rim rotational velocity, in the stator wells. The second test is used to demonstrate the significant further temperature rise which can be caused at the front stage of the compressor by forward leakage: further analysis shows that the temperature rise is dependent on the number of stages of axial disc rim fixings behind the first stage, and that this mechanism can produce higher temperature rises than those due to windage.

Approximate Three-Dimensional Flow Theory for Axial Turbo-Machines

1963 ◽  
Vol 14 (2) ◽  
pp. 125-142 ◽  
Author(s):  
W. T. Howell
Keyword(s):  
Velocity Profile ◽  
Temperature Rise ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Three Dimensional Flow ◽  
Axial Compressors ◽  
Dimensional Flow ◽  
The Subject ◽  
Work Done

SummaryThe subject of three-dimensional flow in axial compressors and turbomachines has been extensively studied since 1945. This paper gives a means of calculating the approximate three-dimensional flow in an axial compressor by giving expressions for the slope of the velocity profile as a function of the axial co-ordinate. These expressions bring out the rôle of the ratio of stage inlet annulus height to stage length in the three-dimensional flow in these machines. The effect of the three-dimensional flow on the stage temperature rise at mean radius is discussed by introducing a work done factor.

Impact of Variable-Geometry Stator Hub Leakage in a Low Speed Axial Compressor

1998 ◽  
Author(s):  
Wendy S. Barankiewicz ◽  
Michael D. Hathaway
Keyword(s):  
Mechanical Design ◽  
Axial Compressor ◽  
Leading Edge ◽  
Operating Conditions ◽  
Variable Geometry ◽  
Turning Angle ◽  
Blade Loading ◽  
Axial Compressors ◽  
The Impact ◽  
Variable Stator

The impact of hub leakage flow associated with the clearance gaps of hub-shrouded variable-geometry stator rows in axial compressors is investigated experimentally. The objectives of this work are to investigate the sensitivity of performance to chordwise leakage location and to provide guidance for the mechanical design of variable stator hub trunions. Although blade loading near the hub is increased when leakage occurs at the leading edge, losses also increase for both design and off-design operating conditions. Leading edge leakage also causes a greater spanwise variation in absolute turning angle over the first 20% of span from the hub. Results show that for a moderately separated stator, the optimum leakage configuration features trailing edge leakage with the leading edge sealed. This confirms the current practice of most engine companies in placing the hub trunion at the blade leading edge.

Three-Dimensional Flows and Loss Reduction in Axial Compressors

1987 ◽  
Vol 109 (3) ◽  
pp. 354-361 ◽  
Author(s):  
Y. Dong ◽  
S. J. Gallimore ◽  
H. P. Hodson
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tracer Gas ◽  
Suction Surface ◽  
Axial Compressors ◽  
Small Clearance ◽  
Oil Flow ◽  
Stator Blade ◽  
Flow Compressor

Measurements have been performed in a low-speed high-reaction single-stage axial compressor. Data obtained within and downstream of the rotor, when correlated with the results of other investigations, provide a link between the existence of suction surface–hub corner separations, their associated loss mechanisms, and blade loading. Within the stator, it has been shown that introducing a small clearance between the stator blade and the stationary hub increases the efficiency of the stator compared to the case with no clearance. Oil flow visualizaton indicated that the leakage reduced the extensive suction surface–hub corner separation that would otherwise exist. A tracer gas experiment showed that the large radial shifts of the surface streamlines indicated by the oil flow technique were only present close to the blade. The investigation demonstrates the possible advantages of including hub clearance in axial flow compressor stator blade rows.

Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

2000 ◽  
Vol 124 (1) ◽  
pp. 140-146 ◽  
Author(s):  
V. Schramm ◽  
K. Willenborg ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Experimental Investigations ◽  
Labyrinth Seals ◽  
Numerical Predictions ◽  
Flow Through ◽  
Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-ε turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

Numerical Investigation of a Cantilevered Compressor Stator at Varying Clearance Sizes

2015 ◽  
Author(s):  
Chengwu Yang ◽  
Xingen Lu ◽  
Yanfeng Zhang ◽  
Shengfeng Zhao ◽  
Junqiang Zhu
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
High Flow ◽  
Leakage Flow ◽  
Streamwise Direction ◽  
Stall Margin ◽  
Axial Compressors ◽  
Pressure Surface ◽  
The Impact ◽  
Highly Loaded

The clearance size of cantilevered stators affects the performance and stability of axial compressors significantly. Numerical calculations were carried out using the commercial software FINE/Turbo for a 2.5-stage highly loaded transonic axial compressor, which is of cantilevered stator for the first stage, at varying hub clearance sizes. The aim of this work is to improve understanding of the impact mechanism of hub clearance on the performance and the flow field in high flow turning conditions. The performance of the front stage and the compressor with different hub clearance sizes of the first stator has been analyzed firstly. Results show that the efficiency decreases as clearance size varies from 0 to 3% of hub chordlength, but the operating range has been extended. For the first stage, the efficiency decreases about 0.5% and the stall margin is extended. The following analysis of detailed flow field in the first stator shows that the clearance leakage flow and elimination of hub corner separation is responsible for the increasing loss and stall margin extending respectively. The effects of hub clearance on the downstream rotor have been discussed lastly. It indicates that the loss of the rotor increases and the flow deteriorates due to increasing of clearance size and hence the leakage mass flow rate, which mainly results from the interaction of upstream leakage flow with the passage flow near pressure surface. The affected region of rotor passage flow field expands in spanwise and streamwise direction as clearance size grows. The hub clearance leakage flow moves upward in span as it flows toward downstream.

Experimental Investigation on the Rubbing Process of Labyrinth Seals Considering the Material Combination

2020 ◽  
Author(s):  
Lisa Hühn ◽  
Oliver Munz ◽  
Corina Schwitzke ◽  
Hans-Jörg Bauer
Keyword(s):  
Turbine Blades ◽  
Design Guidelines ◽  
Operating Conditions ◽  
Contact Forces ◽  
Experimental Investigations ◽  
Process Data ◽  
Labyrinth Seals ◽  
Material Combination ◽  
Higher Temperature ◽  
And Control

Abstract Labyrinth seals are used to prevent and control the mass flow rate between rotating components. Due to thermally and mechanically induced expansions during operation and transient flight maneuvers, a contact, the so-called rubbing process, between rotor and stator cannot be excluded. A large amount of rubbing process data concerning numerical and experimental investigations is available in public literature as well as at the Institute of Thermal Turbomachinery (ITS). The investigations were carried out for different operating conditions, material combinations, and component geometries. In combination with the experiments presented in this paper, the effects of the different variables on load due to rubbing are compared, and discussed with the focus lying on the material combination. The influence of the material on the loads can be identified as detailed as never before. For example, the contact forces in the current experiments are higher due to a higher temperature resistance of Young’s modulus. The analysis will also be based on the rubbing of turbine blades. Design guidelines are derived for labyrinth seals with improved properties regarding tolerance of rub events. Based on the knowledge obtained, guidelines for designing reliable labyrinth seals for future engines are discussed.

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

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.

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

1984 ◽  
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.

scholarly journals Radial Transport and Momentum Exchange in an Axial Compressor

1992 ◽  
Author(s):  
Robert P. Dring
Keyword(s):  
Secondary Flow ◽  
Diffusion Model ◽  
Turbulent Diffusion ◽  
Flow Model ◽  
Axial Compressor ◽  
Momentum Exchange ◽  
Radial Transport ◽  
Axial Compressors ◽  
Mixing Coefficient ◽  
Spanwise Location

The objective of this work was to examine radial transport in axial compressors from two perspectives. The first was to compare the mixing coefficient based on a secondary flow model (using measured radial velocities) with that based on a turbulent diffusion model. The second was to use measured airfoil pressure forces and momentum changes to assess the validity of the assumption of diffusive radial transport which is common to both models. These examinations were carried out at both design and off-design conditions as well as for two rotor tip clearances. In general it was seen that radial mixing was strongest near the hub and that it increased dramatically at near-stall conditions. It was also seen that radial transport could cause large differences (≈ 100%) between the force on an airfoil and the change in momentum across the airfoil at the same spanwise location.

scholarly journals Considerations on Axial Compressor Bleed for Sub-Idle Performance Models

2020 ◽  
Author(s):  
Ferran Roig Tió ◽  
Luis E. Ferrer-Vidal ◽  
Hasani Azamar Aguirre ◽  
Vassilios Pachidis
Keyword(s):  
Flow Analysis ◽  
Axial Compressor ◽  
Engine Performance ◽  
Analysis Tool ◽  
Performance Models ◽  
Performance Modelling ◽  
Start Up ◽  
Considerable Impact ◽  
Aero Engines ◽  
Analytical Approaches

Abstract The trend towards increased bypass ratio and reduced core size in civil aero-engines puts a strain on ground-start and relight capability, prompting renewed interest in sub-idle performance modelling. While a number of studies have looked at some of the broad performance modelling issues prevalent in this regime, the effects that bleed can have on sub-idle performance have not been addressed in the literature. During start-up and relight, the unknown variation in bleed flows through open handling bleed valves can have a considerable impact on the compressor’s operating line. This paper combines experimental, numerical and analytical approaches to look at the effect that sub-idle bleed flows have on predicted start-up operating lines, along with their effect on compressor characteristics. Experimental whole-engine data along with a purpose-built core-flow analysis tool are used to assess the effect of bleed model uncertainty on engine performance models. An experimental rig is used to assess the effects of reverse bleed on compressor characteristics and measurements are compared against numerical results. Several strategies for the generation of sub-idle maps including bleed effects are investigated.

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