Performance characteristics of spiral-groove and shrouded rayleigh step profiles for high-speed non-contacting gas seals

Wear ◽  
1969 ◽  
Vol 14 (2) ◽  
pp. 147
1969 ◽  
Vol 91 (1) ◽  
pp. 60-68 ◽  
Author(s):  
H. S. Cheng ◽  
V. Castelli ◽  
C. Y. Chow

Current methods in gas lubrication have been used in this paper to analyze the gas-film characteristics in a high-speed, face-type gas seal. Detailed analyses are presented for two different surface geometries, the spiral-groove-orifice seal and the shrouded Rayleigh step seal. Results are presented in three parts. The first part shows the performance of a spiral-groove seal without the orifices, and also the difference in performance when the grooves are located at the high pressure, low pressure, or both sides. The second part gives typical performance of a nonparallel film profile for the spiral-groove-orifice seal as well as for the shrouded Rayleigh step seal. In the last part, a comparison is made between the two seal geometries on their tolerance to coning or dishing under a constant seal load.


Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5490
Author(s):  
Elliot P. Lam ◽  
Caroline D. Sunderland ◽  
John G. Morris ◽  
Laura-Anne M. Furlong ◽  
Barry S. Mason ◽  
...  

The study examined whether the performance characteristics of male university field hockey players differed when the match format was 2 × 35 min halves compared to 2 × 2 × 17.5 min quarters. Thirty-five male university field hockey players (age 21.2 ± 3.0 years, height 1.81 ± 0.07 m, body mass 75.1 ± 8.9 kg), competing at national level in the UK, were monitored over 52 matches played across the 2018–2019 (2 × 35 min halves) and 2019–2020 (2 × 2 × 17.5 min quarters) seasons using 15 Hz Global Positioning System units and heart rate monitors. Total distance, high-speed running distance (≥15.5 km·h−1), accelerations (≥2 m·s−1), decelerations (≤−2 m·s−1), average heart rate and percentage of time spent at >85% of maximum heart rate were recorded during both match formats. Two-level random intercept hierarchal models (Match—level 1, Player—level 2) suggested that the change in format from 2 × 35 min halves (2018–2019 season) to 2 × 2 × 17.5 min quarters (2019–2020 season) resulted in a reduction in total distance and high-speed running distance completed during a match (by 221 m and 120 m, respectively, both p < 0.001). As no significant cross-level interactions were observed (between season and half), the change from 35 min halves to 17.5 min quarters did not attenuate the reduced physical performance evident during the second half of matches (total distance: −235 m less in second half; high-speed running distance: −70 m less in second half; both p < 0.001). Overall, the findings suggest that the change in match format did alter the performance characteristics of male university field hockey players, but the quarter format actually reduced the total distance and high-speed running distance completed during matches, and did not attenuate the reduction in performance seen during the second half of matches.


2021 ◽  
Vol 37 ◽  
pp. 522-531
Author(s):  
Haiyin Cao ◽  
Yu Huang ◽  
Youmin Rong ◽  
Hao Wu ◽  
Minghui Guo

Abstract In this study, the influence of inlet pocket size on the static performance of non-Newtonian lubricated hole-entry hybrid journal bearings is theoretically analyzed. The oil film of the bearing is discretized into a nonuniform mesh containing the geometric characteristics of the oil inlet pocket, and the inlet pocket is treated as a micro-oil recess. The Reynolds equation is solved by the finite element method based on Galerkin's techniques, and a new solution strategy to solve the recess/pocket pressure is proposed. The power-law model is used to introduce the non-Newtonian effect. The results show that the static performance characteristics of this type of bearing are greatly affected by the pocket size at both zero speed and high speed.


Author(s):  
A. Doukelis ◽  
K. Mathioudakis ◽  
K. Papailiou

The performance of a high speed annular compressor cascade for different clearance gap sizes, with stationary or rotating hub wall is investigated. Five hole probe measurements, conducted at the inlet and outlet of the cascade, are used to derive blade performance characteristics, in the form of loss and turning distributions. Characteristics are presented in the form of circumferentially mass averaged profiles, while distributions on the exit plane provide information useful to interpret the performance of the blading. Static pressure distributions on the surface of the blades as well as inside the tip clearance gap have also been measured. A set of four clearance gap sizes, in addition to zero clearance data for the stationary wall, gives the possibility to observe the dependence of performance characteristics on clearance size, and establish the influence of rotating the hub. Overall performance is related to features of the tip clearance flow. Increasing the clearance size is found to increase losses in the clearance region, while it affects the flow in the entire passage. Wall rotation is found to improve the performance of the cascade.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yuan Chen ◽  
Hao Shang ◽  
Xiaolu Li ◽  
Yuntang Li ◽  
Bingqing Wang ◽  
...  

Purpose The purpose of this paper is to investigate the influence rule and mechanism of three degrees of freedom film thickness disturbance on the transient performance of spiral groove, upstream pumping spiral groove dry gas seal (UP-SDGS) and double-row spiral groove dry gas seal (DR-SDGS). Design/methodology/approach The transient performance of spiral groove, UP-SDGS and DR-SDGS are obtained by solving the transient Reynolds equation under different axial and angular disturbance coefficients. The transient and steady performance of the above-mentioned DGSs are compared and analyzed. Findings The film thickness disturbance has a remarkable impact on the sealing performance of DGS with different structures and the calculation deviations of the leakage rate of the UP-DGS will increase significantly if the film thickness disturbance is ignored. The axial and angular disturbance jointly affect the film thickness distribution of DGS, but there is no significant interaction between them on the transient sealing performance. Originality/value The influence mechanism of axial disturbance and angular disturbance on the transient performance of typical SDGSs behavior has been explained by theory. Considering small and large disturbance, the interaction between axial disturbance and angular disturbance on the transient performance have been studied.


1995 ◽  
Vol 32 (04) ◽  
pp. 258-266
Author(s):  
Charles M. Lee

ABSTRACT This paper presents a review of some parametric interrelationships between size, weight, hull proportions, propulsion power, and craft speed of modern, monohull, planing-type, marine craft. Parametric relationships are presented in terms related to lifting-surface theory rather than in more conventional "naval architectural" terms such as hull volume coefficients and area coefficients. The scope of the paper includes a brief review of the technical approach used to accomplish the analysis and typical results of the work. Charts which provide a means for approximation of power/ performance relationships are also presented. Performance estimates derived by means of the charts are compared with data derived from the careful and thorough testing of several full-size craft.


Author(s):  
Daisuke Sakota ◽  
Kazuki Kondo ◽  
Ryo Kosaka ◽  
Masahiro Nishida ◽  
Osamu Maruyama

Abstract This work investigates the plasma skimming effect in a spiral groove bearing within a hydrodynamically levitated centrifugal blood pump when working with human blood having a hematocrit value from 0 to 40%. The present study assessed the evaluation based on a method that clarified the limitations associated with such assessments. Human blood was circulated in a closed-loop circuit via a pump operating at 4000 rpm at a flow rate of 5 L/min. Red blood cells flowing through a ridge area of the bearing were directly observed using a high-speed microscope. The hematocrit value in the ridge area was calculated using the mean corpuscular volume, the bearing gap, the cross-sectional area of a red blood cell, and the occupancy of red blood cells. The latter value was obtained from photographic images by dividing the number of pixels showing red blood cells in the evaluation area by the total number of pixels in this area. The plasma skimming efficiency was calculated as the extent to which the hematocrit of the working blood was reduced in the ridge area. For the hematocrit in the circuit from 0 to 40%, the plasma skimming efficiency was approximately 90%, meaning that the hematocrit in the ridge area became 10% as compared to that in the circuit. For a hematocrit of 20% and over, red blood cells almost completely occupied the ridge. Thus, a valid assessment of plasma skimming was only possible when the hematocrit was less than 20%.


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