bluuebunny/crossref_metadata_2025 huggingface dataset:
General Influence Coefficient Algorithm in Balancing of Rotating Machinery
Authors: Yu Xiaoping
Published: March 2007

The General Influence Coefficient Algorithm (GICA), developed in this article, is a new calculation method for Influence Coefficients (ICs) with a general formula. Compared to the traditional calculation method, GICA can solve the ICs′ calculation task when the group of trial weights are installed on the rotor each time, the trial weights are retained on the rotor systems, or there is redundant trial balancing data, when even part of the ICs is known. GICA is also a powerful tool for refining the ICs from redundant balancing data or historical balancing data and serves as a general algorithm. With the general matrix formula, GICA is ready to be applied in a computer‐aided balancing system as the key part of calculation software. Examples in industry are also presented to demonstrate the aplication of this new algorithm.
Pressure Drop Distribution in Smooth and Rib Roughened Square Channel with Sharp 180° Bend in the Presence of Guide Vanes
Authors: Rao.D Venkata Ratna , Prabhu S. V.
Published: March 2007

An experimental investigation is carried out to study the effect of several turn treatments like single guide vane (short and long) and multiple guide vanes on the pressure drop distribution in smooth and rib roughened square channels with a sharp 180° bend. The sharp 180° turn is obtained by dividing a rectangular passage into two square channels using a divider wall with a rounded tip at the location where the
flow negotiates the turn. In rib roughened channels, ribs are configured on the top and bottom surfaces in a symmetric arrangement with an angle of 90° to the mainstream flow. Rib height‐to‐hydraulic diameter ratio (e/D) is maintained constant at 0.14 with a constant pitch‐to‐rib height ratio (P/e) of 10. The pressure drop distribution normalized with the mainstream fluid dynamic pressure head is presented for the outer surfaces. Results suggest that 90° multiple guide vanes result in the decrease of overall pressure drop by around 40% in smooth square channels. However, a reduction in overall pressure drop by only 15% is achievable through guide vanes in rib roughened square channels.
Rotordynamic Stability Case Studies
Authors: De Choudhury Pranabesh
Published: March 2007

In this article case studies are presented involving rotordynamic instability of modern high‐speed turbomachinery relating the field data to analytical methods. The studies include oil seal related field problems, instability caused by aerodynamic cross‐coupling in high‐pressure, high‐speed compressors, and hydrodynamic bearing instability resulting in subsynchronous vibration of a high‐speed turbocharger.
It has been shown that the analytical tools not only help in problem diagnostics, but also aid in problem resolution. Examples are presented showing how analytical methods,
when appropriately applied, can solve rotordynamic instability and result in stable rotor system.
Global Dynamics of Shaft Lines Rotating in Surrounding Fluids Application to Thin Fluid Films
Authors: Lornage David , Jacquet-Richardet Georges
Published: March 2007

While often sufficiently accurate, approaches using rotor dynamics and bladed disc dynamics are not adapted to the study of certain important cases, i.e., when observing wheel/shaft coupling or when fluid elements are strongly coupled with local structural deformations. The approach proposed here is a step toward a global model of shaft lines. The whole flexible wheel/shaft assembly and the influence of specific fluid film elements are considered in a full threedimensional model. A modal projection associated with a grid located at the interface of the fluid and structural domains provides an efficient and adaptable coupling. The equations governing the whole system are solved within a
time marching procedure which alternatively considers the equations of fluid and structure. The technique chosen is applied to two different test cases. The first is composed of
a disc and a thin‐walled shaft mounted on a hydrodynamic bearing. The second is intended for studying a more realistic structure composed of a shaft and a wheel coupled with a fluid film between the wheel and a casing. These applications make it possible to identify trends related to fluid effects and couplings between the flexible structural parts.
Limits for the Use of Auto‐Balancing
Authors: Olsson Karl-Olof
Published: March 2007

The principle for autobalancing by the use of balls running freely in a ring concentric with the rotor center has been known for a long time. However, only in recent times has it been used in real machinery, such as grinding machines and laundry machines. By the increased need for higher precision, it is likely to come into use more frequently in the future. This means that it is important to know its application
possibilities better. By using a time averaging technique, it has been possible to find analytical solutions to a number of problems. This article deals with; (1) the case of a rotor
with anisotropic bearings and damping, where precise conditions for possible balancing are presented; (2) influence from inaccuracy of balancing ring and a rotor with longitudinal
extension and thus having not only a point mass but also a moment of inertia; and (3) using two balancing planes to allow both static and dynamic balancing.
Cavitation Effects on the Stability of a Submerged Journal Bearing
Authors: Sawicki Jerzy T. , Rao T. V. V. L. N.
Published: March 2007

A computational procedure for the mechanism of shear between the liquid sublayer and air cavity in the cavitation zone of a submerged journal bearing is presented here. Using the mass conservation principle, Elrod′s universal equation is modified to take into consideration the shear of the air cavity in the cavitation region. Results of steady state and transient response for the submerged journal bearing using the present approach are compared with the universal equation based on the striated flow in the cavitation region. At steady state, the angular extent of cavitation region predicted by the present approach is higher than that predicted by Elrod′s model and the limit cycle journal transient response using the present approach predicts higher eccentricity
ratios.
Transverse Crack Modeling and Validation in Rotor Systems Including Thermal Effects
Authors: Bachschmid N. , Pennacchi P. , Tanzi E. , Audebert S.
Published: March 2007

In this article, a model is described that allows one to simulate the static behavior of a transversal crack in a horizontal rotor, under the action of the weight and other possible static loads and the dynamical behavior of the rotating cracked shaft. The crack “breaths,” i.e., the mechanism of opening and closing of the crack, is ruled by the stress acting on the cracked section due to the external loads; in a rotor the stress is time‐depending with a period equal to the period of rotation, thus the crack “periodically breaths.” An original simplified model is described that allows cracks of different shape to be modeled and thermal stresses to be taken into account, since they may influence the opening and closing mechanism. The proposed method has been validated using two criteria. Firstly, the crack “breathing” mechanism, simulated with the model, has been compared with the results obtained by a nonlinear 3‐D FEM calculation and a good agreement in the results has been observed. Secondly, the proposed model allows the development of the equivalent cracked beam. The results of this model are compared with those obtained by the above‐mentioned 3‐D FEM. There is a good agreement in the results, of this case as well.

Therefore, the proposed crack model and equivalent beam model can be inserted in the finite beam element model used for the rotor dynamical behavior simulation—the obtained equations have time‐depending coefficients, but they can be integrated in the frequency domain by using the harmonic balance method. The model is suitable for finite beam elements with six degrees of freedom per node, in order to account also for torsion vibrations and coupling between torsion and flexural vibrations.
An Experimental Investigation on Transpiration Cooling Part II: Comparison of Cooling Methods and Media
Authors: Wang J. H. , Messner J. , Stetter H.
Published: March 2007

This article attempts to provide a cooling performance comparison of various mass transfer cooling methods and different cooling media through two experiments. In the first experiment, pressurized air was used as a cooling medium
and two different circular tubes were used as specimens. One is made of impermeable solid material with four rows of discrete holes to simulate film cooling, and the other consists
of sintered porous material to create a porous transpiration cooling effect. The natures of transpiration cooling and film cooling including leading and trailing edge injection cooling
were compared. This experiment found that by using a gaseous cooling medium, transpiration cooling could provide a higher cooling effect and a larger coolant coverage
than film cooling in the leading stagnation region, and on the side of the specimen at the same coolant injection flow rates; but in the trailing stagnation region, the traditional coolant
injection method through discrete film holes might be better than transpiration cooling, especially for turbine blades with thin trailing edges. In the second experiment, the cooling effects of gaseous and liquid media on the same porous tube′s surface were compared. This experiment showed that the porous areas cooled using gaseous and liquid cooling media were almost identical, but the cooling effect of liquid evaporation
was much higher than that of gaseous cooling, especially in the leading and trailing stagnation regions of turbine blades. This important discovery makes it possible to solve
the stagnation region problems in turbine blade cooling.
Recent Studies in Turbine Blade Cooling
Authors: Han Je-Chin
Published: March 2007

Gas turbines are used extensively for aircraft propulsion,
land‐based power generation, and industrial applications.
Developments in turbine cooling technology play a critical
role in increasing the thermal efficiency and power output of
advanced gas turbines. Gas turbine blades are cooled internally
by passing the coolant through several rib‐enhanced
serpentine passages to remove heat conducted from the outside
surface. External cooling of turbine blades by film cooling
is achieved by injecting relatively cooler air from the
internal coolant passages out of the blade surface in order
to form a protective layer between the blade surface and
hot gas‐path flow. For internal cooling, this presentation focuses
on the effect of rotation on rotor blade coolant passage
heat transfer with rib turbulators and impinging jets. The
computational flow and heat transfer results are also presented
and compared to experimental data using the RANS
method with various turbulence models such as k‐ε, and
second‐moment closure models. This presentation includes
unsteady high free‐stream turbulence effects on film cooling
performance with a discussion of detailed heat transfer coef‐
ficient and film‐cooling effectiveness distributions for standard
and shaped film‐hole geometry using the newly developed
transient liquid crystal image method.
On the Development of Two‐Dimensional Wakes within Curved Channels: Experimental and Theoretical Investigation
Authors: Schobeiri M. T. , Pappu K. , John J.
Published: March 2007

The development of a wake flow downstream of a cylindrical rod within a curved channel under zero streamwise pressure
gradient is theoretically and experimentally investigated. The measured asymmetric wake quantities such as the mean velocity
and turbulent fluctuations in longitudinal and lateral directions as well as the turbulent shear stress are transformed from the
probe coordinate system into the curvilinear wake eigen‐coordinate system. For the transformed nondimensionalized velocity
defect and the turbulent quantities, affine profiles are observed throughout the flow regime. Based on these observations and
using the transformed equations of motion and continuity, a theoretical framework is established that generally describes the
two‐dimensional curvilinear wake flow. The theory also describes the straight wake as a special case, for which the curvature
radius approaches infinity. To demonstrate the general validity of theory, experimental results pertaining to curved wake as
well as straight wake flows are compared with the developed theory.
Flow‐Excited Turbine Rotor Instability
Authors: Dimarogonas Andrew D. , Gomez-Mancilla Julio C.
Published: March 2007

The problem of steam whirl is one of the technological limits that now prohibit the development of power‐generating
turbomachinery substantially above GW. Due to steam flow, self‐excited vibrations develop at high loads in the form of
stable limit cycles that, at even higher loads, deteriorate to chaotic vibration of high amplitude.A mathematical model is developed for stability analysis and for the development of a rational stability criterion to be
used at the design stage. The bearing nonlinearity is introduced in the form of high‐order coefficients of a Taylor expansion of
the perturbation forces for fixed‐arc slider bearings and employing nonlinear pad functions for the tilting pad bearings. The
flow excitation is introduced in the form of follower force gradients related to the flow and the power generated.The study of the stable and unstable limit cycles, and the stability of the system in the large, beyond the linear analysis
currently utilized, is done analytically for the De Laval rotor and numerically with finite element analysis of typical
turbomachinery rotors.The range of loads for which limit cycles exist was found to be substantial. This is important for the operation of
large machinery because such cycles permit the operation at loads much higher than the ones that correspond to the onset
of instability of the linearized system. The conditions for the limit cycle deterioration into chaotic orbit are investigated.
Analytical expressions have been obtained for the different stability thresholds for the De Laval rotor.
Comparison of Different Actuator Concepts forApplications in Rotating Machinery
Authors: Ulbrich Heinz
Published: March 2007

Considerable improvements of machines can be expected in the near future through the use ofelectronics in combination with
control techniques. A key position will be held by the actuator systems that finally have to accomplish the controlled energy
transfer according to the objectives. For rotating machine parts this is usually done via the bearings. Basically, there are two
possibilities to transmit the controlled forces; contact free via magnetic fields (magnetic bearings) or the traditional way via
conventional bearings. To realize the regulating actions multiple physical effects can be employed. In this paper some of the
promising types of actuators and their advantages and disadvantages will be discussed, as well as how effectively to use these
active elements under different objectives. Questions concerning the practical realizations will be given high priority.
Modal Testing of Rotors with Fluid Interaction
Authors: Muszynska Agnes
Published: March 2007

Modal testing of rotating structures has specific aspects, and it requires a specialized approach. Classical modal testing when
applied to active (rotating) structures does not provide complete results. These aspects, and specific application of sweep
frequency circular input force perturbation testing of rotors rotating in fluid environment, are discussed in this paper.Emphasis is placed on nonsynchronous perturbation ofshafts rotating at a constant rotative speed. The results are presented in
the direct and quadrature dynamic stiffness versus perturbation frequency formats, which permits the separation ofcomponents
for easy evaluation. This perturbation technique provided new results: 1) identification of solid/fluid interaction modes;
2) identification of fluid dynamic forces in lightly loaded bearings and seals; and 3) multimode identification of rotor systems.
Results of several laboratory rig experiments, the identification algorithm, and data processing techniques are discussed. A
comparison with other testing methods is given.
Influence of Rotation on Heat Transfer from a Two‐Pass Channel with Periodically Placed Turbulence and Secondary Flow Promoters
Authors: Dutta S. , Han J.-C. , Zhang Y.-M.
Published: March 2007

In a stationary duct, ribs placed at an angle oblique to the main flow direction are more effective in heat transfer enhancement
than the ribs placed perpendicular to the flow. Obliquely placed ribs, besides tripping the boundary layer, produce secondary
flow patterns to increase heat transfer from the surfaces. Ducts rotating about an axis perpendicular to their own also develop
secondary flows. These two secondary flows, produced by oblique ribs and rotation, interact with each other and develop
a new heat transfer pattern that is different from those produced by oblique ribs or by rotation alone. This paper uses two
types of rib configurations (60∘ parallel ribs and 60∘ staggered ribs) as turbulence and secondary flow promoters. The local
and surface averaged Nusslt numbers are presented for both stationary and rotating conditions. This experimental study is
conducted on a two‐pass square channel with two opposite rib roughened surfaces (leading and trailing sides). All the walls
are maintained at the same temperature. The heat transfer results in a rotating condition show that the 60∘ staggered ribs are
more effective in the first pass but the 60∘ parallel ribs do better in the second pass.
Evaluation of Seal Effects on the Stabilityof Rotating Fluid Machinery
Authors: Iwatsubo T. , Sheng B. C.
Published: March 2007

The stability of typical rotating fluid machinery such as single ahd multi‐stage pumps is evaluated by using the finite element
method. The individual contribution of the impellers, bearings and seals to the stability and the dynamic interactions of these
fluid elements are examined. Various types of bearings and seals, such as annular smooth, parallel grooved and damper seals,
are compared for better rotor stability. The effect of the operating conditions on the stability is also investigated. The results
show that rotor stability can be easily improved by replacing the unstable fluid elements.
Identification Procedures as Tools for Fault Diagnosisof Rotating Machinery
Authors: Seibold Susanne , Fritzen Claus-Peter
Published: March 2007

System identification procedures offer the possibility to correct erroneous models, based on measurement data. Recently,
this conventional field of application is being extended to fault detection and system diagnosis. In contrast to conventional
approaches, identification procedures try to establish an unequivocal relation in between the damage and specific mechanical
parameters, based on a suitable model. Furthermore, they can be employed during normal operation of the machinery. In
this paper, several identification procedures on the basis of the Extended Kalman Filter are introduced and employed for
model‐based fault detection. Their feasability is proved by several examples. First, it is shown that the crack depth of a
simulated Jeffcott‐rotor can be calculated correctly. Then, the procedures are utilized to determine the crack depth of a rotor
test rig. Finally, it is proved that identification procedures can be employed for the determination of unbalances without
having to apply test masses.
Analysis of Vibration Characteristics for a Rotor‐Bearing System Using Distributed Spring and Damper Model
Authors: Han D. C. , Choi S. H. , Lee Y. H.
Published: March 2007

In this paper, we modelled the journal beatings as distributed springs and dampers to investigate the influence of beating
width on the vibration characteristics of a rotor‐beating system. A quadratic function is used as a shape function for
hydrodynamic journal bearings. And a trapezoidally or a quadratically distributed model is used as a shape function for
hydrostatic journal bearings. A finite element method is applied for analyzing the vibration characteristics of a rotor‐bearing
system.Dimensionless governing equations are derived for a uniform rotor supported by two journal bearings, which are
modelled as point supported or distributed springs and dampers. For these models, natural frequencies for various beating
length ratios and stiffness ratios between the bearing and the shaft are calculated and compared with each other. Then the
stability limits of a rotor supported by two cylindrical journal beatings are calculated for the point supported or distributed
springs and dampers.
Rotordynamic Coefficients of Long StaggeredLabyrinth Gas Seals
Authors: Kwanka K. , Ortinger W.
Published: March 2007

Experimental and theoretical investigations concerning a long staggered labyrinth gas seal are presented. Accurate static
measurements help to assess the influence of the entry swirl, the rotational speed and the pressure difference on the
conservative and the nonconservative force. For a better understanding of the phenomena the forces in each cavity are
investigated. A coupling between the circumferencial flow and the axial flow in the cavity is revealed. The theoretical results
are obtained by a one‐volume bulk‐flow theory which is essentially based on the momentum equation in circumferencial
direction and therefore neglects some effects caused by the axial flow. The experimental results are compared to calculated
results.
Modelling Turbine Vibration in Termsif its Load Variation
Authors: Chalko T. J. , Li D. X.
Published: March 2007

This paper is based on a case history of a 650 MW turbine‐generator, which changed its vibration significantly every time
when a change of its thermal/electrical load was made. Significant changes of vibration amplitude and phase distribution
along the shaft indicated the contribution of different modes of vibration. Interestingly, vibration of other identical units
manufactured by the same manufacturer were not sensitive to load variation. A vibration monitoring system, relying on
observing slow trends in vibration data, was not able to interpret the significant vibration changes. In particular, it was not
clear, whether or not there was a fault in the system and whether or not the unit was safe to operate. The paper presents
problem modelling, analysis and the explanation for vibration changes. Presented analysis explains that vibration changes
were not associated with the fault in the system but they were a natural response of the system to parameter change.
Viscous Flow and Dynamic Stall Effects on Vertical‐Axis Wind Turbines
Authors: Allet A. , Paraschivoiu I.
Published: March 2007

The present paper describes a numerical method, aimed to simulate the flow field of vertical‐axis wind turbines, based on the solution of the steady, incompressible, laminar Navier‐Stokes equations in cylindrical coordinates. The flow equations, written in conservation law form, are discretized using a control volume approach on a staggered grid. The effect of the spinning blades is simulated by distributing a time‐averaged source terms in the ring of control volumes that lie in the path of turbine blades. The numerical procedure used here, based on the control volume approach, is the widely known
“SIMPLER” algorithm. The resulting algebraic equations are solved by the TriDiagonal Matrix Algorithm (TDMA) in the r‐ and z‐directions and the Cyclic TDMA in the 0‐direction. The indicial model is used to simulate the effect of dynamic stall at low tip‐speed ratio values. The viscous model, developed here, is used to predict aerodynamic loads and performance for the Sandia 17‐m wind turbine. Predictions of the viscous model are compared with both experimental data and results from the CARDAAV aerodynamic code based on the Double‐Multiple Streamtube Model. According to the experimental
results, the analysis of local and global performance predictions by the 3D viscous model including dynamic stall effects shows a good improvement with respect to previous 2D models.
Aerodynamic Analysis Models for Vertical‐AxisWind Turbines
Authors: Brahimi M. T. , Allet A. , Paraschivoiu I.
Published: March 2007

This work details the progress made in the development of aerodynamic models for studying Vertical‐Axis Wind Turbines (VAWT′s) with particular emphasis on the prediction of aerodynamic loads and rotor performance as well as dynamic stall
simulations. The paper describes current effort and some important findings using streamtube models, 3‐D viscous model, stochastic wind model and numerical simulation of the flow around the turbine blades. Comparison of the analytical results
with available experimental data have shown good agreement.
Prediction of Heat Transfer For Turbulent Flow in Rotating Radial Duct
Authors: Tekriwal P.
Published: March 2007

The objective of the current modeling effort is to validate the numerical model and improve upon the prediction of heat
transfer in rotating systems. Low‐Reynolds number turbulence model (without the wall function) has been employed for three‐dimensional heat transfer predictions for radially outward flow in a square cooling duct rotating about an axis perpendicular to its length. Computations are also made using the standard and extended high‐Reynolds number kturbulence models (in conjunction with the wall function) for the same flow configuration. The results from all these models are compared with experimental data for flows at different rotation numbers and Reynolds number equal to 25,000. The results show that the low‐Reynolds number model predictions are not as good as the high‐Re model predictions with the wall function. The wall function formulation predicts the right trend of heat transfer profile and the agreement with the data is within 30% or so for flows at high rotation number. Since the Navier‐Stokes equations are integrated all the way to wall
in the case of low‐Re model, the computation time is relatively high and the convergence is rather slow, thus rendering the low‐Re model as an unattractive choice for rotating flows at high Reynolds number.

The extended k‐ε turbulence model is also employed to compute heat transfer for rotating flows with uneven wall temperatures and uniform wall heat flux conditions. The comparison with the experimental data available in literature shows that the predictions on both the leading wall and the trailing wall are satisfactory and within 5‐25% agreement.
Experimental Investigation of Steady and UnsteadyFlow Field Downstream of an Automotive TorqueConverter Turbine and Stator
Authors: Marathe B. V. , Lakshminarayana B.
Published: March 2007

The objective of this investigation is to understand the steady and the unsteady flow field at the exit of an automotive torque converter turbine and stator with a view towards improving it′s performance. A high frequency response five‐hole probe was
designed and built to measure the three‐dimensional steady and unsteady flow fields. The measurements were conducted in a stationary frame of reference and the data were processed to derive the flow properties in the relative (turbine) frame of reference. The experimental data were processed in the frequency domain by spectrum analysis and in temporal‐spatial domain by ensemble averaging technique. The data show that the flow field is highly unsteady with high unresolved unsteadiness (approx. 17‐21% of mean value) and significant blade‐to‐blade periodic component approx. 6% of mean
value). The unresolved unsteadiness and periodic unsteadiness increase with an increase in the radius from the shell to the core whereas the aperiodic unsteadiness does not show any systematic variation with the radius. The experimental data reveal the presence of a low momentum region near the core due to possible flow separation and reattachment inside the turbine passage. Data also show the presence of strong secondary flow near the core and weak secondary flow near the shell at the exit of the turbine. These secondary flows generate high levels of turbulence. A comparison of the flow properties
upstream and downstream of the stator in the stationary frame of reference indicate the presence of high losses near the core due to high turbulence levels and large secondary flows, and high losses near the shell due to possible corner separation near
the shell suction surface inside the stator blade passage. The unsteadiness in the flow properties upstream of the stator is high. The rms value of the unsteady total velocity is approx. 20% of the steady state value. Periodic and aperiodic unsteadiness were also found significant.
Evaluation of Seal Effects on the Stability of RotatingFluid Machinery
Authors: Iwatsubo T. , Sheng B. C.
Published: March 2007

The stability of typical rotating fluid machinery such as single and multi‐stage pumps is evaluated by using the finite element method. The individual contribution of the impellers, bearings and seals to the stability and the dynamic interactions of these
fluid elements are examined. Various types of bearings and seals, such as annular smooth, parallel grooved and damper seals, are compared for better rotor stability. The effect of the operating conditions on the stability is also investigated. The results show that rotor stability can be easily improved by replacing the unstable fluid elements.
Secondary Flow Phenomena in Rotating RadialStraight Pipes
Authors: Cheng K. C. , Wang Liqiu
Published: March 2007

Flow visualization results for secondary flow phenomena near the exit of a rotating radial‐axis straight pipe (length ࡁ = 82 cm, inside diameter d = 3.81 cm, ࡁ/d 21.52) are presented to study the stabilizing (relaminarization) and destabilizing
(early transition from laminar to turbulent flow) effects of Coriolis forces for Reynolds numbers Re = 500 ∼ 4,500 and rotating speeds n = 0 ∼ 200 rpm. The flow visualization was realised by smoke injection method. The main features of the
transition phenomena are disclosed for Re = 1,500 and 4,500. The observed secondary flow patterns are found to be quite different from those obtained by theoretical or numerical analysis with one pair of symmetric and steady counter‐rotating
vortices. The practical implications of the visualization study are pointed out.
A Numerical Analysis on Flow and Heat Transfer inthe Entrance Region of an Axially Rotating Pipe
Authors: Torii Shuichi , Yang Wen-Jei
Published: March 2007

A numerical study is performed to investigate turbulent flow and heat transfer characteristics in the entrance region of a pipe rotating around its axis. Various different k‐ε turbulence models are employed whose function consists of the Richardson
number in the e model to take swirling into account. The axial rotation of the pipe suppresses thermal development and causes a substantial decrease in the Nusselt number along the flow. It is disclosed from the study that an increase in the
rotation rate induces a reduction in the velocity gradient, turbulent kinetic energy and Reynolds stress in the vicinity of the wall and a substantial deformation of these radial profiles in the downstream direction. It results in both a suppression of
the thermal development and an attenuation in the Nusselt number along the flow.
A Numerical Study on Turbulent Couette Flow andHeat Transfer in Concentric Annuli by Means ofReynolds Stress Turbulence Model
Authors: Torii Shuichi , Yang Wen-Jei
Published: March 2007

A numerical study is performed to investigate fluid flow and heat transfer characteristics in a concentric annulus with a slightly heated inner core moving in the flow direction and a stationary, insulated outer cylinder. Emphasis is placed on the
effect of inner core movement on the flow structures, i.e. the normal components of the Reynolds stress and its off‐diagonal one. A Reynolds stress turbulence model is employed to obtain these turbulence quantities. The governing boundary‐layer equations are discretized by means of a control volume finite‐difference technique and numerically solved using the marching procedure. It is found from the study that (i) the streamwise movement of the inner core causes an attenuation in the normal Reynolds stresses, although the inherent anisotropy is maintained and the appreciable turbulence remains, (ii)
the Reynolds stress in the inner wall region is substantially diminished due to the inner core movement, resulting in a decrease in the heat transfer performance, and (iii) an increase in the velocity ratio of the moving inner core of the fluid flow induces a decrease in the Nusselt number as well as the Reynolds stress in the region near the inner core.
Impeller Flow Field Laser Velocimeter Measurements
Authors: Brozowski L. A. , Ferguson T. V. , Rojas L.
Published: March 2007

Development of Computational Fluid Dynamics (CFD) computer codes for complex turbomachinery affords a complete three‐dimensional (3‐D) flow field description. While significant improvements in CFD have been made due to improvements in computers, numerical algorithms, and physical modeling, a limited experimental database for pump CFD code validation exists.

Under contract (NAS8‐38864) to the National Aeronautics and Space Administration (NASA) at Marshall Space Flight Center (MSFC) a test program was undertaken at Rocketdyne to obtain benchmark data for typical rocket engine pump
geometry. Nonintrusive velocity data were obtained with a laser two‐focus velocimeter. Extensive laser surveys at the inlet and discharge of a Rocketdyne‐designed impeller were performed. Static pressures were measured at key locations to provide boundary conditions for CFD code validation.
Prandtl Number Effects on Mixed ConvectionBetween Rotating Coaxial Disks
Authors: Soong Chyi-Yeou
Published: March 2007

Prandtl number characterizes the competition of viscous and thermal diffusion effects and, therefore, is an influential factor in thermal‐fluid flows. In the present study, the Prandtl number effects on non‐isothermal flow and heat transfer between two
infinite coaxial disks are studied by using a similarity model for rotation‐induced mixed convection. To account for the buoyancy effects, density variation in Coriolis and centrifugal force terms are considered by invoking Boussinesq approximation and a linear density‐temperature relation. Co‐rotating disks (Ω2 = Ω1) and rotor‐stator system (Ω1 ≠ Ω2 = 0) are considered to investigate the free and mixed convection flows, respectively. For Reynolds number, Re, up to 1000 and the buoyancy parameter, B=βΔT, of the range of |B| ≤ 0.05, the flow and heat transfer characteristics with Prandtl numbers of 100, 7, 0.7, 0.1, and 0.01 are examined. The results reveal that the Prandtl number shows significant impact on the fluid flow and heat transfer performance. In the typical cases of mixed convection in a rotor‐stator system with |B| = 0.05, the effects in buoyancy‐opposed flows B = 0.05 are more pronounced than that in buoyancy‐assisted ones.
Film Cooling from Two Staggered Rows of Compound Angle Holes at High Blowing Ratios
Authors: Ligrani Phillip M. , Lee Joon Sik
Published: March 2007

Experimental results are presented which describe the development and structure of flow downstream of two staggered rows of film‐cooling holes with compound angle orientations at high blowing ratios. These film cooling configurations are important because they are frequently employed on the first stage of rotating blades of operating gas turbine engines. With this configuration, holes are spaced 3d apart in the spanwise direction, with inclination angles of 24 degrees, and angles of orientation of 50.5 degrees. Blowing ratios range from 0.5 to 4.0 and the ratio of injectant to freestream density is near 1.0. Results show that spanwise averaged adiabatic effectiveness, spanwise‐averaged iso‐energetic Stanton number ratios, surveys of streamwise mean velocity, and surveys of injectant distributions change by important amounts as the blowing ratio increases. This is due to injectant lift‐off from the test surface just downstream of the holes which becomes more pronounced as blowing ratio increases.
Experimental Investigation of the Flow Field in a Multistage Axial Flow Compressor
Authors: Lakshminarayana B. , Suryavamshi N. , Prato J. , Moritz R.
Published: March 2007

The nature of the flow field in a three stage axial flow compressor, including a detailed survey at the exit of an embedded stator as well as the overall performance of the compressor is presented and interpreted in this paper. The measurements include area traverse of a miniature five hole probe (1.07 mm dia) downstream of stator 2, radial traverses of a miniature five hole probe at the inlet, downstream of stator 3 and at the exit of the compressor at various circumferential locations, area traverse of a low response thermocouple probe downstream of stator 2, radial traverses of a single sensor hot‐wire probe at the inlet, and casing static pressure measurements at various circumferential and axial locations across the compressor at the peak efficiency operating point. Mean velocity, pressure and total temperature contours as well as secondary flow contours at the exit of the stator 2 are reported and interpreted. Secondary flow contours show the migration of fluid particles toward the core of the low pressure regions located near the suction side casing endwall corner.
Effect of Upstream Wake on Shower‐Head Film Cooling
Authors: Chen Ping-Hei , Miao Jr-Ming
Published: March 2007

The present study aims to investigate the effect of an upstream wake on the convective transport phenomena over a turbine blade with shower‐head film cooling. A naphthalene sublimation technique was implemented to obtain the detailed mass
transfer distributions on both suction and pressure surfaces of the test blade. All mass transfer runs were conducted on a blowing‐type wind tunnel with a six‐blade linear cascade. The leading edge of the test blade was drilled with three rows of equally spaced injection holes. The upstream wake was simulated by a circular bar with the same diameter as that of the trailing edge of the test blade.

The test condition was fixed at Re = 397,000, M = 0.8, and Tu = 0.4% and upstream wakes were generated at four different locations ahead of the blade cascade. Measured results show that there is a difference in mass transfer rate from the case without upstream wake. This difference is greater on the suction side than on the pressure side. The difference results from the interaction between the wake flow that is induced by the upstream wake and the injection flows that are ejected from the multi‐rows of injection holes on the test blade. It was also found that the location of upstream wake generation significantly affects the mass transfer distributions on both surfaces of test blade.
Influence of Bearing Defects on Dynamical Behavior of An Elastic Shaft
Authors: Bonneau Olivier , Frêne Jean
Published: March 2007

A study of an elastic rotor supported by two defect bearings is presented. The bearing behavior must be considered non‐linear because of the defect effects. The rotor is modelled by typical beam finite element including effects such as gyroscopic effect. The dynamic behavior is analysed using an unsteady time integration procedure. A modal technique is used to reduce the number of degrees of freedom. Results show that the bearing defects introduce supplementary critical speeds. The linear approach is unable to show the supplementary critical speeds which are obtained only by using non linear
analysis.
Heat Transfer Measurements on a Rotating Disk
Authors: Cardone G. , Astarita T. , Carlomagno G. M.
Published: March 2007

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 Re = 250, 000. A discussion about the role played by the adiabatic wall temperature is also
included.
Estimation of Alignment and Transverse Load inMulti‐Bearing Rotor System
Authors: Chalko Tom J. , Li Dong-Xu
Published: March 2007

The paper presents a method for estimation of a multi‐bearing machine alignment on the
basis of measured eccentricities of the shaft in machine bearings. The method uses a linear
FEM model of the rotor and the non‐linear models of machine bearings. In the presented
example, the non‐linear models of hydrodynamic bearings are used, but it is shown, that the
method could be easily applied to other types of bearings. In addition to the alignment
estimation, the method allows to estimate the unknown static load in the transverse direction,
reduced to the equivalent load at one or two selected nodes on the shaft. Verification of the
method is presented using the model of a machine with vertical shaft supported in three
pressurised hydrodynamic bearings. The method is suitable for monitoring of alignment and
transverse load during the machine operation.
Investigation about Electrorheological Squeeze FilmDamper Applied to Active Control of Rotor Dynamic
Authors: Pecheux Benjamin , Bonneau Olivier , Frêne Jean
Published: March 2007

Electrorheological (ER) fluids, discovered in 1947 by W. WINSLOW, are concentrated suspensions
of solid particles in an oily base liquid. Exposed to a strong electric field, their
resistance to flow increases very greatly and this change is progressive, reversible and occurs
very rapidly. Nowadays, ER fluids, made of lithium salt and fluorosilicon got rid of their old
abrasive characteristics and are able to provide a good interface between electronics and
mechanical components. A bibliographical study on ER fluids and ER technology has been
carried out. The aim of this study is adapting ER technology to Squeeze Film Damper. In
order to provide an active control on a flexible rotating shaft so as to command the whole
shaft/bearings device in case of high rotating speed or heavy load trouble. Results of numerical
computation of a shaft bearing assembly with a Squeeze Film Damper using negative
ER fluid are showed in order to see the possibility of avoiding critical speeds by natural
frequency shifting. A technical study of ER Squeeze Film Damper design is also presented,
taking into account ER fluid properties and ER technology requirements.
Internal Damper Characteristics of Rotor System withSubmerged ER Fluid Journal Bearing
Authors: Jang Siyoul , Tichy John A.
Published: March 2007

Electro‐Rheological (ER) fluid behavior is similar to Bingham fluid’ s. Only when the shear
stress magnitude of ER fluid exceeds the yield stress, Newtonian flow results. Continuous
shear strain rate equation about shear stress which simulates Bingham‐like fluid shows
viscosity variations. Shear yield stress is controlled by electric fields. Electric fields in
circumferential direction around the journal are also changeable because of gap distance.
These values make changes of spring and damping coefficients of journal bearings compared
to Newtonian flow case. Implicit viscosity variation effects according to shear strain rates of
fluid are included in generalized Reynolds′ equation for submerged journal bearing. Fluid
film pressure and perturbation pressures are solved using switch function of Elord′s algorithm
for cavitation boundary condition. Spring and damping coefficients are obtained for
several parameters that determine the characteristics of ER fluids under a certain electric
field. From these values stability region for simple rotor‐bearing system is computed. It is
found that there are no big differences in load capacities with the selected electric field
parameters at low eccentric region and higher electric field can support more load with
stability at low eccentric region.
Quantification of Gear Tooth Damage by OptimalTracking of Vibration Signatures
Authors: Choy F. K. , Veillette R. J. , Polyshchuk V. , Braun M. J. , Hendricks R. C.
Published: March 2007

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.
Advanced Compressor Loss Correlations, Part I: Theoretical Aspects
Authors: Schobeiri M. T.
Published: March 2007

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.
Developments in Dynamics of Composite Material Shafts
Authors: Singh S. P. , Gubran H. B. H. , Gupta K.
Published: March 2007

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.
Hysteresis in Oil Flow through a Rotating Tubewith Twin Exit Branches
Authors: Cheng Sun-Wen , Yang Wen-Jei
Published: March 2007

Oil enters a horizontal rotating tube through a radially‐attached duct at one end. The tube
with the other end closed is attached with radial twin exit branches permitting oil to exit into
open air. Air begins to enter through one of the two branches into the tube when its rotational
speed reaches certain critical values. An experimental study is performed to investigate this
air‐oil two‐phase flow behavior. Both the tube and the branches are transparent to allow
illumination and flow visualization during spin‐up and spin‐down processes. The branch‐totube
diameter ratio, rotational speed, and oil flow rate are varied. Changes in oil flow rates
are measured as a function of rotational speed. A comparison is made between cases of a
varying total oil flow rate due to rotation effects and a constant one under control. It is
disclosed that cavitation in oil flow is induced by air entering the branches opposite to the
ejecting oil flow. Subsequently air bubbles progress in the tube. The origin of this intrusion
depends on the hydraulic head loss of the piping system. This study can be applied to oil
lubrication analysis of rotating machinery, such as automotive transmission lines.