The stability of a rigid rotor supported on radial tilting pad journal bearings is analysed. This
study has been tackled both for small unbalance values by linearising the equations of
motion, and also in the case where, because of the high unbalance value, the rotor axis
describes orbits with an amplitude such that the system&#39;s non-linearity cannot be ignored. In
both cases the system&#39;s stable operation maps have been obtained and verified through
numerical integration of the differential equations of motion.

Stefano  Pagano

Ernesto  Rocca

Michele  Russo

Riccardo  Russo

Instability Threshold of a Rigid Rotor-Tilting Pad
Journal Bearings System

The review traces the development of composite shafts in varied applications. The different
theoretical and experimental aspects of dynamics of composite shafts, under investigation for
the past two decades, are reviewed and the state of the art discussed including possible future
developments.

S. P. Singh

H. B. H. Gubran

K. Gupta

Developments in Dynamics of Composite Material Shafts

Reliable efficiency calculation of high-subsonic and transonic compressor stages requires a
detailed and accurate prediction of the flow field within these stages. Despite the tremendous
progress in turbomachinery computational fluid mechanics, the compressor designer still
uses different loss correlations to estimate the total pressure losses and thus the efficiency of
the compressor stage. The new shock loss model and the modified diffusion factor, developed
in Part I, were implemented into a loss calculation procedure. In this part, correlations
for total pressure loss, profile loss, and secondary loss coefficients are presented, using the
available experimental data. Based on the profile loss coefficients, correlations were also
established for boundary layer momentum thickness. These correlations allow the compressor
designer to accurately estimate the blade losses and therefore the stage efficiency.

M. T. Schobeiri

Advanced Compressor Loss Correlations, Part II: Experimental Verifications

Reliable efficiency calculation of high-subsonic and transonic compressor stages requires a
detailed and accurate prediction of the flow field within these stages. Despite the tremendous
progress in turbomachinery computational fluid mechanics, the compressor designer still
uses different loss correlations to estimate the total pressure losses and thus the efficiency of
the compressor stage. A new loss model is presented in this article. Special attention is paid
to the shock and profile losses, since they contribute significantly to the total pressure loss
balance, specifically for transonic compressor stages. A new shock loss model is presented
that calculates the shock position and the shock total pressure losses. The available experimental
data were used to establish new loss correlations that account for experimental
findings.

Advanced Compressor Loss Correlations, Part I: Theoretical Aspects

A commercial CFD code is used to compute the flow field within the first stage impeller of
a two stage axial flow pump. The code solves the 3-D Reynolds Averaged Navier Stokes
equations in a rotating cylindrical coordinate system using a standard <mml:math alttext="$k - \varepsilon $" id="E1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>k</mml:mi><mml:mo>−</mml:mo><mml:mi>ε</mml:mi></mml:mrow></mml:math> turbulence model. Stage design parameters are, rotational speed 870 rpm, 
flow coefficient <mml:math alttext="$\phi = 0.12$" id="E2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>φ</mml:mi><mml:mo>=</mml:mo><mml:mn>0.12</mml:mn></mml:math>, head coefficient <mml:math alttext="$\psi = 0.06$" id="E3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ψ</mml:mi><mml:mo>=</mml:mo><mml:mn>0.06</mml:mn></mml:math>, and specific speed 2.86 (8070 US). Results from the study include
relative and absolute velocities, flow angles, and static and total pressures. Comparison is
made to measured data available for the same impeller at two planes, one upstream of the
impeller and the other downstream. The comparisons are for circumferentially averaged
results and include axial and tangential velocities, impeller exit flow angle, static pressure,
and total pressure. Results of this study show that the computational results closely match
the shapes and magnitudes of the measured profiles, indicating that CFD can be used to
accurately predict performance.

Steven M. Miner

3-D Viscous Flow Analysis of an Axial Flow Pump
Impeller

This paper presents a technique for quantifying the wear or damage of gear teeth in a
transmission system. The procedure developed in this study can be applied as a part of either
an onboard machine health-monitoring system or a health diagnostic system used during
regular maintenance. As the developed methodology is based on analysis of gearbox vibration
under normal operating conditions, no shutdown or special modification of operating
parameters is required during the diagnostic process.The process of quantifying the wear or damage of gear teeth requires a set of measured
vibration data and a model of the gear mesh dynamics. An optimization problem is formulated
to determine the profile of a time-varying mesh stiffness parameter for which the model
output approximates the measured data. The resulting stiffness profile is then related to the
level of gear tooth wear or damage.The procedure was applied to a data set generated artificially and to another obtained
experimentally from a spiral bevel gear test rig. The results demonstrate the utility of the
procedure as part of an overall health-monitoring system.

F. K. Choy

R. J. Veillette

V.  Polyshchuk

M. J. Braun

R. C. Hendricks

Quantification of Gear Tooth Damage by Optimal
Tracking of Vibration Signatures

The paper discusses dynamic effects occurring in machinery rotors supported in bearings and
pedestals with laterally different characteristics. In the considered rotor model the anisotropy
of radial stiffness and tangential (&#8220;cross&#8221;) stiffness components are included. Within certain
ranges of the rotative speed the support anisotropy leads to the specific, excited-by-unbalance
rotor lateral synchronous vibrations in a form of backward (reverse) precession. In
addition, one section of the rotor may precess backward, while the other section simultaneously
precesses forward. Experimental results illustrate this phenomenon. The analytical
model of the system is based on multimode modal approach. It is also shown in this paper
that greatly enhanced information for machine malfunction diagnostics can be obtained by
simulated rotation of the XY transducer system observing rotor lateral vibration. This simulated
rotation can be accomplished by the machine diagnostic data acquistion and processing
system. The data processing also includes extraction of forward and backward components
of elliptical orbits filtered to one frequency, and the filtered orbit major axis magnitude and
its angular orientation.Numerical examples, field data, and experimental results performed on a rotor rig illustrate
applications.

Agnes  Muszynska

Charles T. Hatch

Donald E. Bently

Dynamics of Anisotropically Supported Rotors

The purpose of the present work was twofold: first, to determine if a length scale existed that
would cause the greatest augmentation in stagnation region heat transfer for a given turbulence
intensity and second, to develop a prediction tool for stagnation heat transfer in the
presence of free stream turbulence. Toward this end, a model with a circular leading edge
was fabricated with heat transfer gages in the stagnation region. The model was qualified in
a low turbulence wind tunnel by comparing measurements with Frossling&#39;s solution for
stagnation region heat transfer in a laminar free stream. Five turbulence generating grids
were fabricated; four were square mesh, biplane grids made from square bars. Each had
identical mesh to bar width ratio but different bar widths. The fifth grid was an array of fine
parallel wires that were perpendicular to the axis of the cylindrical leading edge. Turbulence
intensity and integral length scale were measured as a function of distance from the grids.
Stagnation region heat transfer was measured at various distances downstream of each grid.
Data were taken at cylinder Reynolds numbers ranging from 42,000 to 193,000. Turbulence
intensities were in the range 1.1 to 15.9 percent while the ratio of integral length scale to
cylinder diameter ranged from 0.05 to 0.30. Stagnation region heat transfer augmentation
increased with decreasing length scale. An optimum scale was not found. A correlation was
developed that fit heat transfer data for the square bar grids to within &#177;4%. The data from
the array of wires were not predicted by the correlation; augmentation was higher for this
case indicating that the degree of isotropy in the turbulent flow field has a large effect on
stagnation heat transfer. The data of other researchers are also compared with the correlation.

G. James Van Fossen

Chan Y. Ching

Measurements of the Influence of Integral Length Scale on Stagnation Region Heat 
Transfer

T-100 is a multipurpose small power unit developed by Sundstrand Power Systems (USA).
An extensive research programme was launched for the detailed tests of the rig components
including inlet protection system, Compressor stage, Combustor and the Turbine stage. Turbomachinery
Group at Cranfield was involved in the study of the Turbine unit used in this
programme. From the design point of view, detailed aerodynamics in these small units are of
great interest especially where high velocities and narrow passages are involved. Experimental
study was carried out to investigate the flow in the region between the nozzle guide vanes
and the turbine rotor entry. The main concern was to find out how the nozzle guide vane flow
was modified by the rotor and how the rotor flow was affected by the nozzle guide vanes.
Laser measurements were taken at these positions for various flow conditions. An other area
which needs considerable attention is downstream of the turbine rotor where the turning of
flow and mixing process make the situation very complicated. Laser studies were undertaken
in that region and to gain more confidence on laser results, a Cobra pressure probe was
traversed at these stations. This paper describes various steps undertaken to obtain laser
results within the machine. At the end typical laser results have been presented and discussed.

Sohail H. Zaidi

Robin L. Elder

Flow Studies using Laser Anemometry Technique in a
Small Power Unit Radial Inflow Turbine

Three-dimensional flow measurements using LDV system were obtained in the exit region of
a radial inflow turbine at an off-design operating condition. The measurements reveal a
complex flow pattern near the tip region at the rotor exit due to the interaction of the tip
clearance flow. The effect of the rotor on the exit flow field is observed in the proximity of
the rotor exit. Steady axisymmetric, compressible, turbulent flow computations with a two
equation turbulence model were performed using the PARC code for the meridional flow in
the radial turbine exit region. The computational results obtained in the meridional plane are
compared with the experimental results, which are correlated to the rotor blade rotation in
the exit region of the radial turbine.A version of this paper was presented at the 30th AIAA/ASME/SAE/ASEE Joint Propulsion
Conference, Indianapolis, Indiana, Paper no. AIAA-94-3075.

D. M. Murugan

W. Tabakoff

A. Hamed

Flow Measurements and Flow Analysis in the Exit
Region of a Radial Turbine

Heat transfer to a rotating disk is measured for a wide range of Reynolds number values in
the laminar, transitional and turbulent flow regimes. Measurements are performed by making
use of the heated-thin-foil technique and by gauging temperature maps with an infrared
scanning radiometer. The use of the IR radiometer is advantageous on account of its relatively
good spatial resolution and thermal sensitivity and because it allows one to perform
measurements down to very low local Reynolds numbers. Data is obtained on three disks,
having an external diameter varying from 150mm to 450mm; the smallest disk is used only
to measure the adiabatic wall temperature and can rotate up to 21,O00rpm. Heat transfer
results are presented in terms of Nusselt and Reynolds numbers based on the local radius and
show a substantial agreement with previous experimental and theoretical analyses. Transition
to turbulent flow is found at about <mml:math alttext="$Re = 250,000$" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>R</mml:mi><mml:mi>e</mml:mi><mml:mo>=</mml:mo><mml:mn>250</mml:mn><mml:mo>,</mml:mo><mml:mn>000</mml:mn></mml:mrow></mml:math>. A discussion about the role played by the adiabatic wall temperature is also 
included.

G.  Cardone

T.  Astarita

G. M. Carlomagno

Heat Transfer Measurements on a Rotating Disk

About this journal

International Journal of Rotating Machinery publishes original research articles as well as review articles on all types of rotating machinery employing gas, vapor, particle, liquid, and their mixtures (including slurry) as the working substances.

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Chief Editor, Professor Amano, is based at the University of Wisconsin–Milwaukee and his research concentrates on the enhancement of energy production using wind, biomass, alternate fuels, and fossil energy sources.

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International Journal of Rotating Machinery - Table of contents 1997

International Journal of Rotating Machinery | Hindawi

title

International Journal of Rotating Machinery publishes original research articles as well as review articles on all types of rotating machinery employing gas, vapor, particle, liquid, and their mixtures (including slurry) as the working substances.

description

International Journal of Rotating Machinery

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International Journal of Rotating Machinery