scholarly journals Friction-Factor Data for Flat-Plate Tests of Smooth and Honeycomb Surfaces

1992 ◽  
Vol 114 (4) ◽  
pp. 722-729 ◽  
Author(s):  
T. W. Ha ◽  
Dara W. Childs
Keyword(s):  
Flat Plate ◽  
Friction Factor ◽  
Smooth Surface ◽  
Factor Model ◽  
Test Apparatus ◽  
Cell Width ◽  
Plate Test ◽  
Friction Factors ◽  
Line Flow ◽  
Factor Data

Friction-factors for honeycomb surfaces are measured with a flat plate tester. The flat plate test apparatus is described and a method is discussed for determining the friction-factor experimentally. The friction-factor model is developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction-factor are plotted for smooth surface and twelve-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressure, and 5,000 to 130,000 range of the Reynolds number. The optimum geometries for the maximum friction-factor are found as a function of cell width to cell depth and clearance to cell width ratios.

Annular Honeycomb-Stator Turbulent Gas Seal Analysis Using a New Friction-Factor Model Based on Flat Plate Tests

1994 ◽  
Vol 116 (2) ◽  
pp. 352-359 ◽  
Author(s):  
T. W. Ha ◽  
D. W. Childs
Keyword(s):  
Experimental Data ◽  
Mach Number ◽  
Flat Plate ◽  
Friction Factor ◽  
Factor Model ◽  
Model Analysis ◽  
Test Results ◽  
Plate Test ◽  
Rotordynamic Coefficients ◽  
Leakage Characteristics

A new empirical friction-factor model for honeycomb surfaces based on flat plate test results has been developed as a function of Mach number and dimensionless pressure and honeycomb geometry variables. A rotordynamic analysis for centered, turbulent-annular-honeycomb-stator seals has been developed incorporating the new empirical friction-factor model for honeycomb-stator surfaces. The results of the new analysis in predicting the rotordynamic and leakage characteristics have been compared to: (a) Moody’s friction-factor model analysis, and (b) experimental data for short (L/D = 1/6, 25.4 mm long) seal. The comparisons show that the new honeycomb friction-factor model greatly improves the predictions of leakage and rotordynamic coefficients compared to Moody’s friction-factor model, especially, for direct and cross-coupled stiffness.

Test Results for Liquid “Damper” Seals Using a Round-Hole Roughness Pattern for the Stators

1999 ◽  
Vol 121 (1) ◽  
pp. 42-49 ◽  
Author(s):  
Dara W. Childs ◽  
Patrice Fayolle
Keyword(s):  
Friction Factor ◽  
Round Hole ◽  
Test Results ◽  
Partial Explanation ◽  
Rotordynamic Coefficients ◽  
Stiffness Coefficients ◽  
Friction Factors ◽  
Direct Stiffness ◽  
Factor Data ◽  
Pressure Driven Flow

Test results are reviewed for two annular liquid seals (L = 34.9 mm; D = 76.5 mm) at two clearances (.1 and .12 mm). The seal stators use hole-pattern-roughened stators that are identical except for hole depths of .28 and 2.0 mm. Tests are conducted at three speeds out to 24,600 rpm and three pressures out to 68 bars. Test data consist of leakage rates and rotordynamic coefficients at centered and eccentric positions with static eccentricity ratios out to 0.5. Test results are consistent with expectations in regard to the reduction of cross-coupled stiffness coefficients due to stator roughness. However, the measured direct stiffness coefficients were unexpectedly low. A partial explanation for these results is provided by measured friction factor data which show an increase in the friction factors for pressure-driven flow with an increase in clearance. A prediction model for rotordynamic coefficients, incorporating the friction-factor data, predicted a substantial loss in direct stiffness but could not explain the very low (or negative) values that were measured. The model did explain the measured drop in cross coupled stiffness (k) and provides an alternative explanation to observed reductions in k values; specifically, an increase in the friction factor with increasing clearance causes a reduction in k irrespective of any parallel reduction in the average circumferential velocity.

Hydrodynamic Characteristics of Crossflow over MEMS-Based Pillars

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Ali Koşar ◽  
Brandon Schneider ◽  
Yoav Peles
Keyword(s):  
Friction Factor ◽  
Hydrodynamic Characteristics ◽  
Flow Conditions ◽  
Pin Fin ◽  
Aspect Ratios ◽  
Friction Factors ◽  
Wide Range ◽  
Hydrodynamic Processes ◽  
Factor Data ◽  
Key Parameter

A parametric study was performed to reveal the hydrodynamic processes controlling crossflow over MEMS-based micro pin fin devices. Pressure drop experiments were conducted and used to obtain friction factors on a wide range of micro pin fin devices for various flow conditions and geometrical configurations, including pin fin height-to-diameter aspect ratios, spacings, and shapes. The acquired data suggests that the device geometry is the key parameter dictating friction factor trends and magnitude along with the Reynolds number. Additionally, friction factor data has shown that correlations based on experimental results performed on conventional scale tube bundles do not accurately predict the trends under working conditions pertaining to microfluidic systems.

Experimental Investigations on Friction Factors of Gaseous Flow Through a Micro-Tube With Smooth Surface

2017 ◽  
Author(s):  
Takayuki Shigeishi ◽  
Chungpyo Hong ◽  
Yutaka Asako
Keyword(s):  
Friction Factor ◽  
Smooth Surface ◽  
Gas Flow ◽  
Experimental Investigations ◽  
Adiabatic Wall ◽  
Choked Flow ◽  
Friction Factors ◽  
Wide Range ◽  
Flow Through ◽  
Local Pressures

The purpose of the present study is to experimentally investigate flow characteristics on semi-local friction factors of nitrogen gas flow through a micro-tube with a smooth surface. The experiments were performed using a glass micro-tube with 266 μm in diameter and 120 mm in length. Three static pressure holes are drilled on the wall near the micro-tube outlet at intervals of 5 mm, and the local pressures were measured with the outlet discharged into the atmosphere. The local values of Mach number, temperature and friction factor were obtained from the measured local pressures. The result in the wide range of Reynolds number was also obtained, including the choked flow. Darcy friction factor and Fanning friction factor obtained under the assumptions of both a Fanno flow (adiabatic wall) and an Isothermal flow were compared with empirical correlations in the literature and numerical results.

Measurement and Prediction of Rough Wall Effects on Friction Factor—Uniform Roughness Results

1988 ◽  
Vol 110 (4) ◽  
pp. 385-391 ◽  
Author(s):  
W. F. Scaggs ◽  
R. P. Taylor ◽  
H. W. Coleman
Keyword(s):  
Friction Factor ◽  
Roughness Element ◽  
Discrete Element ◽  
Turbulent Pipe Flow ◽  
Number Range ◽  
Flow Friction ◽  
Friction Factors ◽  
Roughness Model ◽  
Factor Data ◽  
Good Agreement

The results of an experimental investigation of the effects of surface roughness on turbulent pipe flow friction factors are presented and compared with predictions from a previously published discrete element roughness model. Friction factor data were acquired over a pipe Reynolds number range from 10,000 to 600,000 for nine different uniformly rough surfaces. These surfaces covered a range of roughness element sizes, spacings and shapes. Predictions from the discrete element roughness model were in very good agreement with the data.

Flat Plate Honeycomb Seals Friction Factor Analysis

2014 ◽  
Author(s):  
Mirko Micio ◽  
Cosimo Bianchini ◽  
Daniele Massini ◽  
Bruno Facchini ◽  
Alberto Ceccherini ◽  
...  
Keyword(s):  
Flat Plate ◽  
Friction Factor ◽  
Geometrical Parameters ◽  
Leakage Flow ◽  
Test Rig ◽  
Cell Width ◽  
High Rotational Speed ◽  
Experimental Campaign ◽  
Honeycomb Seals ◽  
Secondary Air

Among the various type of seals used in gas turbine secondary air system to guarantee sufficient confinement of the main gas path, honeycomb seals well perform in terms of enhanced stability and reduced leakage flow. Due to the large amount of honeycomb cells typically employed in real seals, it is generally convenient to treat the sealing effect of the honeycomb pack as an increased distributed friction factor on the plain top surface. That is why this analysis is focused on a simple configuration composed by a honeycomb facing a flat plate. In order to evaluate the sealing performance of such honeycomb packs, an experimental campaign was carried out on a stationary test rig where the effects of shaft rotation are neglected. The test rig was designed to analyze different honeycomb geometries so that a large experimental database could be created to correlate the influence of each investigated parameter. Honeycomb seals were varied in terms of hexagonal cell dimension and depth in a range that well represents actual honeycomb packs employed in industrial compressors. For each geometry five different clearances were tested. This work reports the findings of such experimental campaign whose results were analyzed in order to guide actual seals design and effective estimates of shaft loads. Static pressure measurements reveal that the effects of investigated geometrical parameters on friction factor well correlate with a corrected Mach number based on the cell depth. The presence of acoustic effects in the seals was further investigated by means of hot wire anemometry. Acoustic forcing due to flow cavity interaction was found to be characterized by a constant Strouhal number based on cell width. Numerical simulations helped in the identification of system eigenmodes and eigenfrequencies providing an explanation to the friction factor enhancement triggered at a certain flow speed. Finally the generated dataset was tested comparing the predicted leakage flow with experimental data of actual seals (with high pressure and high rotational speed) showing a very good agreement.

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