bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Factors Influencing the StructuralVibration in Ball Bearings
Authors: Mehra Kapil , Farhang Kambiz , Datta Jayanta 
Published: March 2007

Hertzian equation for elastic contact is utilized along with lumped parameter approach to obtain the equations that govern the structural vibration of ball bearings. The lumped parameter formulation is obtained by treating various elements with mass lumped at their centers of gravity and the contact as nonlinear springs with nonlinear spring rates.Effects of preload, ball rotational speed, and damping are studied using the formulation. It is found that in the presence of preload, irrespective of the load magnitude, contact is maintained with both the inner and the outer races. Hence, responses obtained with and without the check for ball/inner race and ball/outer race interferences are identical. In addition, no appreciable change is observed in the responses when the preload value is varied from 1 to 10 N. At high speed of operation, the balls are found to maintain contact with the outer ring, whereas intermittent contact with the inner ring occurs for brief periods of time. Introduction of lubricant is found to dampen the oscillations considerably.
Flow Structures Inside a Rotor‐Stator Cavity
Authors: Geis T. , Ebner J. , Kim S. , Wittig S. 
Published: March 2007

This paper describes an experimental investigation initiated to determine the threedimensional flow field inside the rim seal cavity of a double‐shrouded rotor‐stator
system. Thereby, the effects caused by perturbances in the rotor wall were additionally
examined. The objective of this work is to provide detailed information about the
mechanisms that can promote elevated temperature levels in the high pressure section of
a gas turbine. Both ingested hot gas and windage heating generated at the rotor‐stator
interface can severely affect the material temperatures and thus considerably increase
the thermal load of the rotating parts.The flow velocities were measured by means of an advanced LDV system capable of providing phase‐resolved data. The flow field was determined for two different rotorstator combinations. One of the rotor disks contained small rectangular cavities, located at the disk rim and arranged uniformly in’ the circumferential direction. These elements
are referred to as the shank cavities of the rotor disk.The mechanical torque was measured to demonstrate the influence of these elements
on the windage power. The measurements were performed at operating conditions that
are typical for aero‐engines. It is shown that a perturbed rotor surface can raise the drag
notably. The experiments were conducted in a high speed test rig at rotational Reynolds
numbers up to Reϕ ≈ 4.2*106. The data were plotted as the dimensionless moment coefficient cM and correlated with Reϕ and the dimensionless cooling flow rate cw.
Model Based Fault Identification in Rotor Systemsby Least Squares Fitting
Authors: Markert Richard , Platz Roland , Seidler Malte 
Published: March 2007

In the present paper a model based method for the on‐line identification of malfunctions in rotor systems is proposed. The fault‐induced change of the rotor system is taken into account by equivalent loads which are virtual forces and moments acting on the linear undamaged system model to generate a dynamic behaviour identical to the measured
one of the damaged system.By comparing the equivalent loads reconstructed from current measurements to the
pre‐calculated equivalent loads resulting from fault models, the type, amount and
location of the current fault can be estimated. The identification method is based on
least squares fitting algorithms in the time domain. The quality of the fit is used to find
the probability that the identified fault is present.The effect of measurement noise, measurement locations, number of mode shapes
taken into account etc., on the identification result and quality is studied by means of
numerical experiments. Finally, the method has also been tested successfully on a real
test rig for some typical faults.
Fluid Flow and Heat Transfer in an InternalCoolant Passage
Authors: Shih Tom I.-P. , Lin Yu-Liang , Stephens Mark A. 
Published: March 2007

Computations were performed to study the three‐dimensional flow and heat transfer in a U‐shaped duct of square cross section with inclined ribs on two opposite walls under rotating and non‐rotating conditions. Two extreme limits in the Reynolds number (25,000 and 350,000) were investigated. The rotation numbers investigated are 0, 0.24, and 0.039. Results show rotation and the bend to reinforce secondary flows that align with it and to retard those that do not. Rotation was found to affect significantly the flow and heat transfer in the bend even at a very high Reynolds number of 350,000 and a very low Rotation number of 0:039. When there is no rotation, the flow and heat transfer in the bend were dominated by rib‐induced secondary flows at the high Reynolds number limit and by bend‐induced pressure‐gradients at the low Reynolds number limit. Long streaks of reduced surface heat transfer occur in the bend at locations where streamlines from two contiguous secondary flows merge and then flow away from the surface. The location and size of these streaks varied markedly with Reynolds and rotation numbers.This computational study is based on the ensemble‐averaged conservation equations of mass, momentum (compressible Navier‐Stokes), and energy. Turbulence is modelled by the low‐Reynolds shear‐stress transport (SST) model of Menter. Solutions were generated by using a cell‐centered, finite‐volume method, that is based on second‐order accurate flux‐difference splitting and a diagonalized alternating‐direction implicit scheme with local time‐stepping and V‐cycle multigrid.
Recontouring of Jet Engine Compressor Bladesby Flow Simulation
Authors: Hönen Herwart , Panten Matthias 
Published: March 2007

In modern jet propulsion systems the core engine has an essential influence on the total engine performance. Especially the high pressure compressor plays an important role in this scheme. Substantial factors here are losses due to tip clearance effects and
aerodynamic airfoil quality. During flight operation the airfoils are subject to wear and
tear on the leading edge. These effects cause a shortening of the chord length and the
leading edge profiles become deformed. This results in a deterioration of the engine
efficiency performance level and a reduced stall margin.The paper deals with the re‐contouring of the leading edges of compressor airfoils
by application of a new developed method for the profile definition. The common
procedure of smoothing out the leading edges manually on a wheel grinding machine
can not provide a defined contour nor a reproducible result of the overhaul process. In
order to achieve optimized flow conditions in the compressor blade rows, suitable
leading edge contours have to be defined for the worn airfoils. In an iterative process
the flow behavior of these redesigned profiles is checked by numerical flow simulations
and the shape of the profiles is improved. The following machining of the new defined
leading edge contours is achieved on a grinding station handled by an appropriately
programmed robot.
Deflections and Strains in Cracked Shafts Due to Rotating Loads: A Numerical and Experimental Analysis
Authors: Bachschmid Nicolò , Tanzi Ezio 
Published: March 2007

In this article the deflections of a circular cross‐section beam presenting a transverse crack of varying depths caused by various loads (bending, torsion, shear, and axial loads) are analyzed with the aid of a rather refined three‐dimensional model that takes into account the nonlinear contact forces in the cracked area. The bending and shear loads are applied in several different angular positions in order to simulate a rotating load on a fixed beam or, by changing the reference system, a fixed load on a rotating beam. Torsion and axial loads are fixed with respect to the beam.Results obtained for the rotating beam can then be used for the analysis of cracked horizontal‐axis heavy rotors in which the torsion is combined with the bending load. The effect of friction is also considered in the cracked area. The characteristic “breathing” behavior of the cracked area was analyzed and compared to that obtained with a rather simple one‐dimensional model. The differences in results with respect to those based on fracture mechanics are emphasized. In order to highlight the effect of the presence of the crack, the deflections of the uncracked beam loaded with the same loads were subtracted from the deflections of the cracked beam.Finally, a cracked specimen was extensively analyzed by means of several strain gauges to study the strain distribution on the outer surface around the crack in various loading conditions. Consistent pre‐stresses were found, and they influence the breathing behavior. The experimental results were compared with those obtained using the onedimensional linear model.
Darmstadt Rotor No. 2, II: Design of Leaning Rotor Blades
Authors: Bergner Jörg , Hennecke Dietmar K. , Hoeger Martin , Engel Karl 
Published: March 2007

For Darmstadt University of Technology′s axial singlestage transonic compressor rig, a new three‐dimensional aft‐swept rotor was designed and manufactured at MTU Aero Engines in Munich, Germany. The application of carbon fiber–reinforced plastic made it possible to overcome structural constraints and therefore to further increase the amount of lean and sweep of the blade. The aim of the design was to improve the mechanical stability at operation that is close to stall.To avoid the hazard of rubbing at the blade tip, which is found especially at off‐design operating conditions close to the stability limit of the compression system, aft‐sweep was introduced together with excessive backward lean.This article reports an investigation of the impact of various amounts of lean on the aerodynamic behavior of the compressor stage on the basis of steady‐state Navier‐Stokes simulations. The results indicate that high backward lean promotes an undesirable redistribution of mass flow and gives rise to a basic change in the shock pattern, whereas a forward‐leaning geometry results in the development of a highly back‐swept shock front. However, the disadvantage is a decrease in shock strength and efficiency.
Partial Compensation of Unbalance by Oneand Two‐Plane Automatic Balancing Devices
Authors: Ryzhik Boris , Duckstein Henner , Sperling Lutz 
Published: March 2007

This article presents an analysis of several aspects of one‐ and two‐plane automatic balancing devices of rigid rotors. The effect of partial compensation of unbalance and the decreasing of vibrations in the region beyond the first critical
speed is studied analytically and confirmed by the results of computer simulations. The possibility of partial unbalance compensation is very important considering application of
autobalancing devices to rotors with a large polar moment of inertia.Among the most important practical applications of devices are centrifuges, hand power tools, washing machines, and optical disk drives.
Development of a Three‐Dimensional Geometry Optimization Method for Turbomachinery Applications
Authors: Kämmerer Steffen , Mayer Jürgen F. , Stetter Heinz , Paffrath Meinhard , Wever Utz , Jung Alexander R. 
Published: March 2007

This article describes the development of a method for optimization of the geometry of three‐dimensional turbine blades within a stage configuration. The method is based on flow simulations and gradient‐based optimization techniques.
This approach uses the fully parameterized blade geometry as variables for the optimization problem. Physical parameters such as stagger angle, stacking line, and
chord length are part of the model. Constraints guarantee the requirements for cooling, casting, and machining of the blades.The fluid physics of the turbomachine and hence the objective function of the optimization problem are calculated by means of a three‐dimensional Navier‐Stokes solver especially designed for turbomachinery applications. The gradients required for the optimization algorithm are computed by numerically solving the sensitivity equations. Therefore, the explicitly differentiated Navier‐Stokes equations are incorporated
into the numerical method of the flow solver, enabling the computation of the sensitivity equations with the same numerical scheme as used for the flow field solution.This article introduces the components of the fully automated optimization loop and their interactions. Furthermore, the sensitivity equation method is discussed and several
aspects of the implementation into a flow solver are presented. Flow simulations and sensitivity calculations are presented for different test cases and parameters. The validation
of the computed sensitivities is performed by means of finite differences.
The Pre‐Stall Behavior of a 4‐Stage Transonic Compressor and Stall Monitoring Based on Artificial Neural Networks
Authors: Methling Frank-Oliver , Stoff Horst , Grauer Frank 
Published: March 2007

Current research concerned with the aerodynamic instability
of compressors aims at an extension of the operating
range of the compressor towards decreased massflow. In
practice, a safety margin is maintained between operating
point and stability limit to prevent the compressor from going
into stall and surge. In this article, we analyze the behavior
of a 4‐stage transonic axial compressor before entering
the unstable range and present an approach to identifying incipient
surge and stall using artificial neural networks. This
method is based on measurements of the unsteady static wall
pressure in front of the first rotor.Analyzing the static pressure signals by using the Fast
Fourier Transform shows that peripheral disturbances
(modal waves) can only be identified in a small range close
to nominal speed (at 95%). At lower speeds (60 to 80% of
nominal speed), the investigated compressor flow enters instability
by spike‐type stall.Monitoring stability over the entire speed range of the compressor relies on artificial neural networks using the unsteady wall pressure signal. In the present case, artificial neural networks show to be the most useful tool to indicate approaching instability. The method works reliably for both types of instabilities, spike‐type stall as well as modal waves.
An Integrated Flow Analysis System for theRecalculation of Hydraulic Machinery Bladings
Authors: Haas H. , Riedel N. , Watzelt Ch. , Fernandez A. , Schilling R. 
Published: March 2007

The present paper deals with the recalculation of hydraulic machinery bladings. By combining numerical tools for the geometrical description of the bladings, mesh generation, different CFD flow models (Q3D Euler, 3D Euler, Navier‐Stokes)
and post‐processing a highly efficient integrated flow analysis system is obtained.The capability of the developed software package is shown by recalculating water turbine runners of different specific speeds, a semi‐axial and a radial centrifugal impeller. The results of the flow computations are compared to each other and to existing measurements.
Flow Measurements and Flow Analysis in the ExitRegion of a Radial Turbine
Authors: Murugan D. M. , Tabakoff W. , Hamed A. 
Published: March 2007

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.
Dynamics of Anisotropically Supported Rotors
Authors: Muszynska Agnes , Hatch Charles T. , Bently Donald E. 
Published: March 2007

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 (“cross”) 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.
Analytic Creep Durability of Rotating Uniform Disks
Authors: Nyashin Yuriy , Shishlyaev Victor 
Published: March 2007

Turbine disks of aircraft engines in operation are subjected to alternating thermocyclic deformation under high temperatures. Operation gives rise to sufficiently high stresses and subsequent creep damaging effects.In this paper we suggest an approach for describing creep rupture of a simple rotating disk due to the accumulation of creep induced microdefects. The dissipated energy of the creep deformation is considered as the measure of material damage.The lifetime of the disk can be predicted on the basis of this approach. Both crack initiation and damage propagation to complete rupture of a disk are calculated. The analytic
results can be compared to known experimental data. The derived algorithm can be
applied to estimate the lifetime of real machinery components when creep deformations are
dominant.
Turbulence Amplification with Incidence at the Leading Edge of a Compressor Cascade
Authors: Hobson Garth V. , Wakefield Bryce E. , Roberts William B. 
Published: March 2007

Detailed measurements, with a two‐component laser‐Doppler velocimeter and a thermal anemometer were made near the suction surface leading edge of controlled‐diffusion airfoils in cascade. The Reynolds number was near 700,000, Mach number equal to 0.25, and freestream turbulence was at 1.5% ahead of the cascade.It was found that there was a localized region of high turbulence near the suction surface leading edge at high incidence. This turbulence amplification is thought to be due to the interaction of the free‐shear layer with the freestream inlet turbulence. The presence of the local high turbulence affects the development of the short laminar separation bubble that forms very near the suction side leading edge of these blades. Calculations indicate that the local high levels of turbulence can cause rapid transition in the laminar bubble allowing it to reattach as a short “non‐burst” type.The high turbulence, which can reach point values greater than 25% at high incidence, is the reason that leading edge laminar separation bubbles can reattach in the high pressure gradient regions near the leading edge. Two variations for inlet turbulence intensity were measured for this cascade. The first is the variation ofmaximum inlet turbulence with respect to inlet‐flow angle; and the second is the variation of leading edge turbulence with respect to upstream distance from the leading edge of the blades.
Experimental Investigation of Steady and UnsteadyFlow Field Upstream and Downstream of anAutomotive Torque Converter Pump
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 pump with a view towards improving its performance. The measurements were conducted in a stationary frame of reference using a high frequency response five‐hole probe and the data were processed to derive the flow properties in the relative (pump) frame of reference. The experimental data were processed at three different operating conditions: maximum efficiency point, design point and near‐stall point. The unsteady values of flow properties (pressure, velocity and flow angles) were divided into five components: mean, periodic, blade aperiodic, revolution aperiodic and unresolved components.The velocity profiles indicate zones of separation near the core region at speed ratio (SR) 0.8. This zone is transported to the shell region at SR 0.065 due to the presence of a strong secondary vortex. The secondary vortex (weak) for the SR 0.8 rotates anti‐clockwise, and is located only near core‐wake region. The secondary vortex (strong) at SR 0.065 rotates clockwise, and encompasses the entire passage. The unsteady flow data show that unresolved and periodic components dominate the unsteadiness at the pump exit. The overall aperiodicity is negligible and is dominated by the blade aperiodic component.
Transition to Fluid‐Induced Limit CycleSelf‐Excited Vibrations of a Rotor andInstability Threshold “Hysteresis”
Authors: Muszynska Agnes 
Published: March 2007

The transient process which starts at the instability threshold of a rotor rotating in a fluid environment, and ends up in the limit cycle of self‐excited vibrations known as fluid whirl or fluid whip, is discussed in this paper. A one‐lateral‐mode, isotropic, nonlinear model of the rotor with fluid interaction allows for exact particular solutions and an estimation of the transient process. The fluid interacting with the rotor is contained in a small radial clearance area, such as in bearings, seals, or rotor‐to‐stator clearances, and its effects are represented by fluid film radial stiffness, damping, and fluid inertia rotating at a different angular velocities.The effects of fluid damping and fluid inertia circumferential velocity ratios on the rotor startup and shutdown instability threshold differences are also discussed.
On the Development of Viscous Solvers for Computationof Transient Flows in Turbomachines
Authors: Wiedermann Alexander , Miyagawa Kazuyoshi , Eguchi Tsuyoshi 
Published: March 2007

This paper focuses on development and validation of a viscous solver for the computation of unsteady flows in turbomachinery blade rows and stages consisting of rotors and stators. The code has been evolved from steady‐state single flow solvers developed by Wiedermann based on time‐marching finite difference schemes. A two‐equation eddy viscosity model is applied, and the wall boundary conditions are determined by the y+‐distance of the first grid line away from the wall. For the solution of transient flow fields the original time‐stepping algorithm is replaced by a time‐accurate scheme.The emphasis of the code validation will be on blade‐row interaction in a complete
turbomachinery stage. A 3‐D example will be discussed and those parameters evaluated
which are important for actual blading design.