Surface Roughness Effects in High-Speed Hydrodynamic Journal Bearings

1997 ◽  
Vol 119 (4) ◽  
pp. 776-780 ◽  
Author(s):  
H. Hashimoto
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Reynolds Equation ◽  
Computation Time ◽  
Experimental Results ◽  
Roughness Effects ◽  
Modified Reynolds Equation ◽  
Nonlinear Simultaneous Equations ◽  
Theoretical Results ◽  
Good Agreement

This paper describes an applicability of modified Reynolds equation considering the combined effects of turbulence and surface roughness, which was derived by Hashimoto and Wada (1989), to high-speed journal bearing analysis by comparing the theoretical results with experimental ones. In the numerical analysis of modified Reynolds equation, the nonlinear simultaneous equations for the turbulent correction coefficients are greatly simplified to save computation time with a satisfactory accuracy under the assumption that the shear flow is superior to the pressure flow in the lubricant films. The numerical results of Sommerfeld number and attitude angle are compared with the experimental results to confirm the applicability of the modified Reynolds equation in the case of two types of bearings with different relative roughness heights. Good agreement was obtained between theoretical and experimental results.

An Assessment of the Value of Theory in Predicting Gas-Bearing Performance

1961 ◽  
Vol 83 (2) ◽  
pp. 195-200 ◽  
Author(s):  
S. Cooper
Keyword(s):  
Steady State ◽  
Slip Velocity ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Experimental Methods ◽  
Experimental Results ◽  
Theoretical Investigations ◽  
Gas Bearing ◽  
Theoretical Results

The object of the paper is to indicate the value of theoretical investigations of hydrodynamic finite bearings under steady-state conditions. Methods of solution of Reynolds equation by both desk and digital computing, and methods of stabilizing the processes of solution, are described. The nondimensional data available from the solutions are stated. The outcome of an attempted solution of the energy equation is discussed. A comparison between some theoretical and experimental results is shown. Experimental methods employed and some difficulties encountered are discussed. Some theoretical results are given to indicate the effects of the inclusion of slip velocity, stabilizing slots, and a simple case of whirl.

On the effects of two-dimensional Reynolds roughness in hydrodynamic lubrication

1978 ◽  
Vol 364 (1716) ◽  
pp. 89-106 ◽  
Keyword(s):  
Surface Roughness ◽  
Numerical Computation ◽  
Autocorrelation Function ◽  
Reynolds Equation ◽  
Hydrodynamic Lubrication ◽  
The Other ◽  
Roughness Height ◽  
Two Dimensional ◽  
Roughness Effects ◽  
Dimensional Surface

The hydrodynamic lubrication of rough surfaces is analysed with the Reynolds equation, whose application requires the roughness spacing to be large, and the roughness height to be small, compared with the thick­ness of the fluid film. The general two-dimensional surface roughness is considered, and results applicable to any roughness structure are obtained. It is revealed analytically that two types of term contribute to roughness effects: one depends on the shape of the autocorrelation function and the other does not. The former contribution was neglected by previous workers. The numerical computation of an example shows that these two contributions are comparable in magnitude.

scholarly journals Prediction of Tool Lifetime and Surface Roughness for Nickel-Based Waspaloy

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Shao-Hsien Chen ◽  
Chung-An Yu
Keyword(s):  
Surface Roughness ◽  
Tool Wear ◽  
High Speed ◽  
Cutting Speed ◽  
High Strength ◽  
Cutting Parameters ◽  
Experimental Results ◽  
Predictive Values ◽  
Actual Surface ◽  
Wide Range

In recent years, most of nickel-based materials have been used in aircraft engines. Nickel-based materials applied in the aerospace industry are used in a wide range of applications because of their strength and rigidity at high temperature. However, the high temperatures and high strength caused by the nickel-based materials during cutting also reduce the tool lifetime. This research aims to investigate the tool wear and the surface roughness of Waspaloy during cutting with various cutting speeds, feed per tooth, cutting depth, and other cutting parameters. Then, it derives the formula for the tool lifetime based on the experimental results and explores the impacts of these cutting parameters on the cutting of Waspaloy. Since the impacts of cutting speed on the cutting of Waspaloy are most significant in accordance with the experimental results, the high-speed cutting is not recommended. In addition, the actual surface roughness of Waspaloy is worse than the theoretical surface roughness in case of more tool wear. Finally, a set of mathematical models can be established based on these results, in order to predict the surface roughness of Waspaloy cut with a worn tool. The errors between the predictive values and the actual values are 5.122%∼8.646%. If the surface roughness is within the tolerance, the model can be used to predict the residual tool lifetime before the tool is damaged completely. The errors between the predictive values and the actual values are 8.014%∼20.479%.

Calculation of Surface Roughness Effects on Air-Riding Seals

2002 ◽  
Author(s):  
C. Guardino ◽  
J. W. Chew ◽  
N. J. Hills
Keyword(s):  
Surface Roughness ◽  
Compressible Flows ◽  
Reynolds Equation ◽  
Incompressible Flows ◽  
Numerical Solutions ◽  
Cfd Analysis ◽  
Roughness Effects ◽  
Stationary Wall ◽  
Comparative Results ◽  
Effect Of Surface

The effects of surface roughness on air-riding seals are investigated here using the Rayleigh-pad as an example. Both incompressible and compressible flows are considered using both CFD analysis and analytical/numerical solutions of the Reynolds equation for various 2D or 3D roughness patterns on the stationary wall. A ‘unit-based’ approach for incompressible flows has also been employed and is shown to be computationally much less expensive than the full-geometry solution. Results are presented showing the effect of surface roughness on the net lift force. The effects of varying the Reynolds number are demonstrated, as well as comparative results for static stiffness.

Analysis of Thermal Effects in Hydrodynamic Bearings

1986 ◽  
Vol 108 (2) ◽  
pp. 219-224 ◽  
Author(s):  
R. Boncompain ◽  
M. Fillon ◽  
J. Frene
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Effects ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Heat Transfer Equation ◽  
Reversed Flow ◽  
Theoretical Results ◽  
Generalized Reynolds Equation ◽  
Good Agreement

A general THD theory and a comparison between theoretical and experimental results are presented. The generalized Reynolds equation, the energy equation in the film, and the heat transfer equation in the bush and the shaft are solved simultaneously. The cavitation in the film, the lubricant recirculation, and the reversed flow at the inlet are taken into account. In addition, the thermoelastic deformations are also calculated in order to define the film thickness. Good agreement is found between experimental data and theoretical results which include thermoelastic displacements of both the shaft and the bush.

Effect of housing surface roughness on the performance of a centrifugal compressor for turbocharger: Experimental and numerical study

2021 ◽  
pp. 146808742110475
Author(s):  
Ealumalai Karunakaran ◽  
Sanket Mulye ◽  
Jawali Maharudrappa Mallikarjuna
Keyword(s):  
Surface Roughness ◽  
Numerical Analysis ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Numerical Study ◽  
Experimental Results ◽  
Wall Turbulence ◽  
Low Flow ◽  
Pressure Losses ◽  
Compressor Performance

Centrifugal compressor plays a vital role in the performance of a turbocharger. The compressor contains an impeller and housing, including the vaneless diffuser and a volute. The high-speed flow from the impeller is diffused in the diffuser and volute, before being delivered to the engine. Hence, the housing flow characteristics affect the compressor performance and operating range. Generally, housing has noticeable surface roughness, especially in the volute. This study evaluates the effect of the volute surface roughness on the compressor performance by experimental and numerical analysis. The experiments are conducted for three different volute surface roughness levels to measure the overall compressor pressure ratio and efficiency. The uncertainty in the efficiency for experimental results is within ±0.5% pts. Also, steady-state numerical simulations are performed to analyse the flow mechanisms causing pressure losses. Then, a numerical analysis is done to understand the effect of roughness of the diffuser hub and shroud walls on the compressor performance. From the experimental results, it is found that the increase in the roughness level of the volute from the smooth surface by circa 900% and 1400% shows a significant reduction in the compressor efficiency at the design speed (N) and off-design speeds (0.87 and 1.13 N). The reductions of efficiency are about 0.5%–1% pts at the near surge point, 1%–1.5% pts at the peak efficiency point and 2%–2.5% pts at the near choke flow point. The CFD analyses show significantly higher near-wall turbulence and wall shear resulting in additional pressure losses. Also, it is found that the pressure losses are more sensitive to roughness of the diffuser shroud-wall than that of the hub-wall. On the other hand, the diffuser hub-wall roughness increases the radial momentum in the diffuser passage which suppress the flow separation at low flow rates.

Selection of Scuffing-Resistant Materials Under Lubricated, High-Speed Sliding

1988 ◽  
Vol 140 ◽  
Author(s):  
J. J. Au ◽  
M. W. Corcoran ◽  
J.-Y. Yung
Keyword(s):  
High Speed ◽  
Experimental Results ◽  
Wear Tests ◽  
Selection Of ◽  
Good Agreement

AbstractThe scuffing resistance of materials under lubricated high-speed sliding was analyzed based on the thermalelastic instability (TEl) model. The model was used to select and rank scuffing-resistant materials.The scuffing resistance was also determined experimentally by the Falex 6 thrust washer wear tests. There was good agreement between the experimental results and the analytical predictions.

Pressure Broadening of the Microwave Absorption Lines of Oxygen

1973 ◽  
Vol 51 (22) ◽  
pp. 2329-2331 ◽  
Author(s):  
Y. Yamamoto ◽  
M. Cattani
Keyword(s):  
Microwave Absorption ◽  
Quadrupole Moment ◽  
Microwave Spectrum ◽  
The Self ◽  
Experimental Results ◽  
Dispersion Interactions ◽  
Pressure Broadening ◽  
Line Widths ◽  
Theoretical Results ◽  
Good Agreement

We calculate the line widths for the self-broadening of the microwave spectrum of oxygen taking into account simultaneously quadrupole–quadrupole and dispersion interactions. Our theoretical results are compared with the more recent experimental results. A good agreement is obtained between them if the oxygen quadrupole moment is taken as Q = 1.21 ± 0.05 D Å.

A Study on the Parameters in Hard Turning of High Speed Steel

2018 ◽  
Vol 5 (2) ◽  
pp. 1-12
Author(s):  
Krishnaraj Vijayan ◽  
N. Gouthaman ◽  
Tamilselvan Rathinam
Keyword(s):  
Surface Roughness ◽  
Tool Wear ◽  
High Speed ◽  
Hard Turning ◽  
White Layer ◽  
High Speed Steel ◽  
Cutting Parameters ◽  
Experimental Results ◽  
Depth Of Cut ◽  
Contributing Factors

The objectives of hard turning of high speed steel (HSS-M2 Grade) are to investigate the effect of cutting parameters on cutting force, tool wear and surface integrity. This article presents the experimental results of heat treated high speed steel machined in a CNC lathe using cubic boron nitride (CBN) tools. Turing experiments were carried out using central composite design (CCD) method. From the experiments the influence of cutting parameters and their interactions on cutting forces, temperature and surface roughness (Ra) were analyzed. Following this, multi response optimization was done to find the best combination of parameters for minimum force, minimum temperature and minimum surface roughness. The experimental results showed that the most contributing factors were feed followed by depth of cut and spindle speed. A white layer formed during hard turning was also analyzed by scanning electron microscope (SEM) and the results showed that it was greatly influenced by the speed and depth of cut. Tool wear was experiments were conducted at the optimum cutting conditions and it was noted that the tool satisfactorily performed up to 10 minutes at dry condition.

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