Application of Lund’s Stability Analysis Program in Design of Modern Turbomachinery

2003 ◽  
Vol 125 (4) ◽  
pp. 471-476 ◽  
Author(s):  
Pranabesh De Choudhury
Keyword(s):  
Stability Analysis ◽  
High Speed ◽  
Analytical Tool ◽  
Gas Pressure ◽  
Operating Conditions ◽  
Analysis Program ◽  
Gas Density ◽  
High Speeds ◽  
Design And Manufacture

The analytical tool developed by Lund has aided in the design and manufacture of modern turbomachinery operating at relatively high speeds, under severe operating conditions, with high gas pressure, and gas density. The purpose of this paper is to show, by means of selected problems, as a practicing engineer in the design of high speed turbomachinery, how the methods developed by Lund aided in the design and problem diagnostics of such turbomachinery.

Application of Lund’s Stability Analysis Program in Design of Modern Turbomachinery

2001 ◽  
Author(s):  
Pranabesh De Choudhury
Keyword(s):  
Stability Analysis ◽  
High Speed ◽  
Analytical Tool ◽  
Gas Pressure ◽  
Operating Conditions ◽  
Analysis Program ◽  
Gas Density ◽  
High Speeds ◽  
Design And Manufacture

Abstract The analytical tool developed by Lund has aided in the design and manufacture of modern turbomachinery operating at relatively high speeds, under severe operating conditions, with high gas pressure, and gas density. The purpose of this paper is to show, by means of selected problems, as a practicing engineer in the design of high speed turbomachinery, how the methods developed by Lund aided in the design and problem diagnostics of such turbomachinery.

Angular Contact Ball Bearings: Track Position at High Speeds

1969 ◽  
Vol 184 (1) ◽  
pp. 351-370
Author(s):  
K. C. Falcon ◽  
C. Andrew
Keyword(s):  
High Speed ◽  
Contact Angles ◽  
Operating Conditions ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Test Rig ◽  
Outer Race ◽  
High Speeds ◽  
Surface Displacements ◽  
Lubricant Flow

The track position of the balls on the outer race of an angular contact bearing of the series and size used on the main shaft of aero gas turbine engines was measured in a test rig. The test rig was capable of simulating the operating conditions of the bearing with respect to axial load, inner race speed and high lubricant flow rates. The contact angle, defined by the track position, was deduced from the measurement of sub-surface displacements in the race using a number of small transducers embedded therein. The resulting contact angles were compared with values predicted from a number of unconfirmed theories in current use. At conditions of high speed and low load the correlation is poor; an over-estimation of the cage speed, arising from the false assumption that gross ball slip does not occur, gives rise to an over-estimation of the changes of contact angles from their nominal values.

Static and dynamic characteristics and stability analysis of high-speed water-lubricated hydrodynamic journal bearings

2021 ◽  
pp. 135065012110270
Author(s):  
Bo Xu ◽  
Hun Guo ◽  
Xiaofeng Wu ◽  
Yafeng He ◽  
Xiangzhi Wang ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Load Capacity ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Inertia Effect ◽  
Static And Dynamic Characteristics ◽  
Damping Coefficients ◽  
Stiffness And Damping

The purpose of this paper is to analyze the influence of turbulent, inertia, and misaligned effects on the static and dynamic characteristics and stability of high-speed water-lubricated hydrodynamic journal bearings. Based on the Navier–Stokes equation, the mixing-length theory, and the essential assumption that the velocity profile is not strongly affected by inertia force, the fluid lubrication model with turbulent, inertia, and misaligned effects is established, and then the stability analysis of bearings is carried out based on the equation of motion with four degrees of freedom. The model is solved by the finite difference method and the numerical results are compared under different operating conditions. The results show that the turbulent effect greatly increases the load capacity, power consumption, stiffness and damping coefficients, and stability of bearings, and the inertia effect significantly increases the volume flow rate of bearings, and the misaligned effect increases the load capacity, stiffness and damping coefficients, and stability of bearings. In high rotary speed and moderate eccentricity ratios, the influence of the inertia effect on the load capacity, stiffness coefficients, and stability cannot be neglected.

Dynamic Characterization of Tilting Pad Journal Bearings From Component and System Level Testing

2012 ◽  
Author(s):  
Adolfo Delgado ◽  
Mirko Librashi ◽  
Giuseppe Vannini
Keyword(s):  
Stability Analysis ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Operating Conditions ◽  
Logarithmic Decrement ◽  
Experimental Results ◽  
System Level ◽  
Component Level ◽  
Force Coefficients ◽  
Tilting Pad

The dynamic response of a direct lube, 5-pad, rocker-back pivot tilting pad bearing is characterized in a controlled motion (component level) test rig, and in a spin bunker (full system level) using a dummy rotor mounted on two identical bearings. In the component level test, the force coefficients (stiffness, damping, mass) are identified from pseudorandom excitations using a 2-DOF model. N-DOF system including the pad motions has been shown to yield frequency dependent coefficients that warrant the use of asynchronous coefficients for stability analysis in centrifugal compressors. However, experimental results showed that the real part of the dynamic stiffness is well represented as a constant stiffness and mass coefficients while the imaginary part yields a constant damping coefficient (i.e. frequency independent). In the system level test, a dedicated dummy rotor (representative of a high speed centrifugal compressor rotor) is excited by a magnetic shaker throughout a frequency range covering the rotor modes of interest while spinning at constant speed. From the rotor harmonic response the damping of each mode is extracted using a curve-fitting method based on a 1-DOF model for a given set of speeds. The dummy rotor test provides reference values for system logarithmic decrement and further validates the component level test results. The logarithmic decrement prediction using identified bearing force coefficients are in good agreement with the experimental results. In addition, using for prediction identified coefficients in a classical K-C-M or synchronous K-C form yields similar results (within 15%). This indicates that for the given bearing geometry (clearance, offset and size) and operating conditions, synchronously reduced force coefficients are adequate for stability analysis. Comparison of the identified force coefficients with results from commercially available code yielded reasonable agreement on direct coefficients while some discrepancies are highlighted on the cross-coupled coefficients.

Fourth Paper: A New Design of Angular Contact Ball Race

1970 ◽  
Vol 185 (1) ◽  
pp. 382-393 ◽  
Author(s):  
D. J. Haines ◽  
M. J. Edmonds
Keyword(s):  
High Speed ◽  
Operating Conditions ◽  
Approximate Analysis ◽  
Full Extent ◽  
Operating Range ◽  
Contact Points ◽  
High Speeds ◽  
New Race ◽  
Outer Contact ◽  
Ball Motion

The work reported in the second and third papers revealed that under high speed operating conditions significant slide occurs at the contact points. The full extent of the present limitations became apparent in 1967 and led in that year to the new race design. In this design the balls contact the outer track at two points simultaneously instead of the conventional one point. An approximate analysis of race behaviour is presented which indicates that when the new bearing is driven from the inner track the ball motion is controlled at this track over most of the operating range. This fact and the retention of the inner, and the major outer contact positions, at points close to their static positions result in improvements in performance of up to 30 per cent at high speeds.

Effect of Design Changes in Railway Catenary-Pantograph Systems on Power Collection at High Speed

1968 ◽  
Vol 90 (4) ◽  
pp. 680-689
Author(s):  
R. T. Gray ◽  
S. Levy ◽  
J. A. Bain ◽  
E. J. Leclerc
Keyword(s):  
Contact Force ◽  
High Speed ◽  
Operating Conditions ◽  
Department Of Transportation ◽  
High Speeds ◽  
Design Changes ◽  
Force Variation ◽  
Suitable System ◽  
The U.S

Using a GE-635 computer program developed for the U.S. Department of Transportation, a study has been made of the effect of changes in the catenary-pantograph system on the quality of power collection at high speeds. The study explored the effect of: (a) Sag between towers, (b) pantograph spacing, (c) stiffness of the tower support, (d) damping and stiffness of the pantograph, (e) stiffness of the contact spring, (f) dropper stiffness, (g) dropper spacing. It was found that all of these have a significant effect on the constancy of the contact force between catenary and pantograph. By proper choice of system constants, the contact force variation can be substantially reduced. A basis is provided for selecting suitable system constants for a given range of operating conditions.

Quasi-static and dynamic analyses of thin-webbed high-speed gears: Centrifugal effect influence

2019 ◽  
Vol 233 (21-22) ◽  
pp. 7282-7291
Author(s):  
B Guilbert ◽  
P Velex ◽  
P Cutuli
Keyword(s):  
Finite Elements ◽  
High Speed ◽  
Operating Conditions ◽  
Centrifugal Effect ◽  
High Speeds ◽  
Load Distributions ◽  
Lumped Parameter ◽  
Dynamic Analyses ◽  
Gear Geometry

The objective of this paper is to analyse the effect of centrifugal effects on thin-rimmed/-webbed gears. To this end, an original hybrid gear model is used, which combines lumped parameter elements, finite elements and condensed sub-structures along with a mortar-based mesh interface aiming at coupling mismatched models. It is shown that due to gear body flexibility, centrifugal effects can strongly modify geometry and, consequently, tooth load distributions at high speeds. The possibility to counterbalance these effects by introducing profile and lead modification is investigated. It is finally shown that for the effective tooth design, both thin-rimmed gear geometry and operating conditions must be accounted for.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

RED CUT COBALT

Alloy Digest ◽  
1980 ◽  
Vol 29 (8) ◽  
Keyword(s):  
Fracture Toughness ◽  
Cast Iron ◽  
High Speed ◽  
Elevated Temperatures ◽  
High Speed Steel ◽  
Heat Treating ◽  
High Speeds ◽  
Red Hardness ◽  
Nonferrous Alloys ◽  
Cutting Point

Abstract RED CUT COBALT steel is made by adding 5% cobalt to the conventional 18% tungsten -4% chromium-1% vanadium high-speed steel. Cobalt increases hot or red hardness and thus enables the tool to maintain a higher hardness at elevated temperatures. This steel is best adapted for hogging cuts or where the temperature of the cutting point of the tool in increased greatly. It is well adapted for tools to be used for reaming cast-iron engine cylinders, turning alloy steel or cast iron and cutting nonferrous alloys at high speeds. This datasheet provides information on composition, physical properties, and hardness as well as fracture toughness. It also includes information on forming, heat treating, and machining. Filing Code: TS-367. Producer or source: Teledyne Vasco.

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