scholarly journals Impact of Leakage Inlet Swirl Angle in a Rotor–Stator Cavity on Flow Pattern, Radial Pressure Distribution and Frictional Torque in a Wide Circumferential Reynolds Number Range

2020 ◽  
Vol 5 (2) ◽  
pp. 7
Author(s):  
Tilman Raphael Schröder ◽  
Hans-Josef Dohmen ◽  
Dieter Brillert ◽  
Friedrich-Karl Benra
Keyword(s):  
Reynolds Number ◽  
Radial Pressure ◽  
Cavity Flow ◽  
Frictional Torque ◽  
Leakage Flow ◽  
Test Rig ◽  
Axial Thrust ◽  
Number Range ◽  
Swirl Angle ◽  
Through Flow

In the side-chambers of radial turbomachinery, which are rotor–stator cavities, complex flow patterns develop that contribute substantially to axial thrust on the shaft and frictional torque on the rotor. Moreover, leakage flow through the side-chambers may occur in both centripetal and centrifugal directions which significantly influences rotor–stator cavity flow and has to be carefully taken into account in the design process: precise correlations quantifying the effects of rotor–stator cavity flow are needed to design reliable, highly efficient turbomachines. This paper presents an experimental investigation of centripetal leakage flow with and without pre-swirl in rotor–stator cavities through combining the experimental results of two test rigs: a hydraulic test rig covering the Reynolds number range of 4 × 10 5 ≤ R e ≤ 3 × 10 6 and a test rig for gaseous rotor–stator cavity flow operating at 2 × 10 7 ≤ R e ≤ 2 × 10 8 . This covers the operating ranges of hydraulic and thermal turbomachinery. In rotor–stator cavities, the Reynolds number R e is defined as R e = Ω b 2 ν with angular rotor velocity Ω , rotor outer radius b and kinematic viscosity ν . The influence of circumferential Reynolds number, axial gap width and centripetal through-flow on the radial pressure distribution, axial thrust and frictional torque is presented, with the through-flow being characterised by its mass flow rate and swirl angle at the inlet. The results present a comprehensive insight into the flow in rotor–stator cavities with superposed centripetal through-flow and provide an extended database to aid the turbomachinery design process.

scholarly journals Experimental Investigation of Centrifugal Flow in Rotor–Stator Cavities at High Reynolds Numbers >108

2021 ◽  
Vol 6 (2) ◽  
pp. 13
Author(s):  
Tilman Schröder ◽  
Sebastian Schuster ◽  
Dieter Brillert
Keyword(s):  
Reynolds Number ◽  
Pressure Distribution ◽  
Radial Pressure ◽  
Reynolds Numbers ◽  
Axial Thrust ◽  
Number Range ◽  
High Reynolds Numbers ◽  
Reynolds Number Range ◽  
Through Flow ◽  
High Reynolds

The designers of radial turbomachinery need detailed information on the impact of the side chamber flow on axial thrust and torque. A previous paper investigated centripetal flow through narrow rotor–stator cavities and compared axial thrust, rotor torque and radial pressure distribution to the case without through-flow. Consequently, this paper extends the investigated range to centrifugal through-flow as it may occur in the hub side chamber of radial turbomachinery. The chosen operating conditions are representative of high-pressure centrifugal compressors used in, for example, carbon capture and storage applications as well as hydrogen compression. To date, only the Reynolds number range up to Re=2·107 has been investigated for centrifugal through-flow. This paper extends the range to Reynolds numbers of Re=2·108 and reports results of experimental and numerical investigations. It focuses on the radial pressure distribution in the rotor–stator cavity and shows the influence of the Reynolds number, cavity width and centrifugal mass flow rate. It therefore extends the range of available valid data that can be used to design radial turbomachinery. Additionally, this analysis compares the results to data and models from scientific literature, showing that in the higher Reynolds number range, a new correlation is required. Finally, the analysis of velocity profiles and wall shear delineates the switch from purely radial outflow in the cavity to outflow on the rotor and inflow on the stator at high Reynolds numbers in comparison to the results reported by others for Reynolds numbers up to Re=2·107.

LP Turbine Reynolds Lapse Phenomena: Time Averaged Area Traverse and Multistage CFD

2010 ◽  
Author(s):  
Matthias Ku¨rner ◽  
Carsten Schneider ◽  
Martin G. Rose ◽  
Stephan Staudacher ◽  
Jochen Gier
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Reynolds Numbers ◽  
Test Rig ◽  
Propulsion Systems ◽  
Number Range ◽  
Second Stage ◽  
Number Variation ◽  
Aero Engines ◽  
Lp Turbine

The new LP turbine test rig “ATRD” at the Institute of Aircraft Propulsion Systems (ILA) at Stuttgart University has been used to study the detailed effects of Reynolds number variation. The two-stage LP turbine has been developed in a cooperation of ILA and MTU Aero Engines GmbH. Changes in the turbine characteristics are discussed. Five hole probe area traverse data has been acquired at exit from each row of aerofoils across a broad range of Reynolds numbers, over 88,000 down to 35,000. The experimental data is supported by multi-row steady CFD predictions. The behaviour of wakes, loss cores and secondary deviations is identified across the Reynolds number range. The present study is focusing on the effects of Reynolds number variation on the vane of the second stage.

The Effect of Rotary Arms on Corotating Disk Flow

1995 ◽  
Vol 117 (2) ◽  
pp. 259-262 ◽  
Author(s):  
John Girard ◽  
Scott Abrahamson ◽  
Kevin Uznanski
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Radial Flow ◽  
Disk Drives ◽  
Number Range ◽  
Reynolds Number Range ◽  
Through Flow ◽  
Dominant Feature ◽  
Flow Visualizations ◽  
The Impact

This investigation studied the impact of rotary style arms on the flow between corotating disks contained by a stationary cylindrical enclosure. Both ventilated and nonventilated hub configurations were considered. The particular geometry used represents a simplified model for common disk drives. Flow visualizations were performed over the Reynolds number range of 3.4 × 104 to 3.4 × 105. The arms were observed to dramatically alter the flow field and to produce an azimuthal pressure gradient throughout the flow field. The dominant feature of the flow between two disks was the arm wake. Moreover, an exchange of fluid across the shroud opening, which provided arm access, was observed. Arm effects became stronger as the arm tips were positioned closer to the hub. The combination of arms and radial through flow was studied over a similar Reynolds number range. In this case, the flow field remained dominated by arm effects, although some effects arising from the radial flow were observed.

Leakage and Frictional Characteristics of Turbulent Helical Flow in Fine Clearance

1973 ◽  
Vol 95 (4) ◽  
pp. 493-497 ◽  
Author(s):  
E. Bilgen ◽  
R. Boulos ◽  
A. C. Akgungor
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Tangential Velocity ◽  
Helical Flow ◽  
Frictional Torque ◽  
Empirical Equations ◽  
Pressure Gradients ◽  
Test Rig ◽  
Seal Design ◽  
Concentric Cylinders

The leakage and frictional characteristics of helical flow in concentric cylinders with fine clearance have been studied for the ratio of clearance to radius from 0.0006 to 0.0127 and the ratio of length to clearance from 20 to 750. The Reynolds number based on the axial velocity was from zero to 104 and the Reynolds number based on the radius and tangential velocity was from 103 to 3 × 105. These geometrical and kinematical conditions are usually encountered in the seal design of turbomachines. The leakage and the frictional torque have been measured with a 20 in. dia test rig for various pressure gradients and different rotational speeds of the inner cylinder. The case of zero pressure gradient has also been included. The experimental data and those published in the literature have been analyzed and correlated in the form of empirical equations.

Prediction in Rotor-Stator Cavities at High Reynolds Numbers up to Re ≈ 2·108: Towards a New Parametric Model

2020 ◽  
Author(s):  
Tilman Raphael Schröder ◽  
Sebastian Schuster ◽  
Dieter Brillert
Keyword(s):  
Radial Pressure ◽  
Reynolds Numbers ◽  
Friction Torque ◽  
Frictional Torque ◽  
Lower Efficiency ◽  
Axial Thrust ◽  
Wrong Prediction ◽  
Turbulence Effects ◽  
High Reynolds ◽  
Cfd Analyses

Abstract Side chambers of centrifugal turbomachinery resemble rotor–stator cavities. The flow in these cavities develops complex patterns which substantially influence the axial thrust on the shaft and the frictional torque on the rotor. Axial thrust caused by the flow pattern in side chambers accumulates in multistage single shaft radial compressors where it is often balanced by a single axial bearing. Miscalculation of axial thrust may lead to axial loads significantly higher than predicted or even undefined load situations which may cause early bearing failure. Likewise, a wrong prediction of friction losses may lead to lower efficiency than originally intended. Current models for axial thrust and friction torque are limited to circumferential Reynolds numbers of Re ≤ 107. New models are needed for modern high-pressure centrifugal compressors which reach circumferential Reynolds numbers up to Re = 109. The rotor–stator cavity flow model by Kurokawa and Sakuma [16] for merged boundary layers is analysed. It is based on the assumptions of axisymmetric and time invariant flow. Functional forms of the mean tangential and radial velocity and the surface stress vectors on the rotor and stator are assumed. Reynolds averaging is applied to consider turbulence effects in the model. The modelling assumptions are compared with detailed RANS CFD analyses at Reynolds numbers of 4 · 106 ≤ Re ≤ 2 · 108 to investigate their accuracy. Based on these CFD results, a way towards a high Reynolds number model is presented, providing prediction of disc torque, radial pressure distribution and axial thrust in rotor–stator cavities.

Telemetric Heat Transfer Coefficient Measurements in an Open Rotor-Stator System Air Gap at up to 8500 rpm

2018 ◽  
Author(s):  
Benjamin Heinschke ◽  
Wieland Uffrecht ◽  
Stefan Odenbach ◽  
Volker Caspary
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Air Gap ◽  
Test Rig ◽  
Axial Fan ◽  
Rotating Disc ◽  
Number Range ◽  
Open Rotor

This contribution presents the experimental results of telemetric heat transfer measurements on the rotor side of an open rotor-stator system air gap with various rotational speeds and rotor-stator distances. For the heat transfer measurements, the local over-temperature method is used, which is based on the analysis of the non-stationary temperature rise of small heated structures at the rotor surface. Additionally, experiments on a second test rig, a flat plate connected with an axial fan, are conducted for the streamwise calibration of the sensors. The measurement program is composed of eight rotational speeds n between 76 and 8,558 rpm at five gap distances s in the range from 1.5 mm to 25 mm at eight radial sensor positions r between 46 and 188 mm. Overall the test rig installation is equivalent to a rotational Reynolds number range Rer from 1,085 to 2,040,000. An evaluation and interpretation of the results shows that the characteristic correlation between the Reynolds number and the Nusselt number is similar to that used for the turbulent flow at a free rotating disc. The variation of the gap distance leads to a constant offset in the heat transfer coefficient, which becomes significantly higher with small distances.

scholarly journals Influence of Seal Cavity Leakage Flow on Compressor Performance Investigated with a Circumferentially Averaged Method

2021 ◽  
Vol 11 (2) ◽  
pp. 780
Author(s):  
Dong Liang ◽  
Xingmin Gui ◽  
Donghai Jin
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Interaction Mechanism ◽  
Main Flow ◽  
Leakage Flow ◽  
Destructive Effect ◽  
Through Flow ◽  
Compressor Performance ◽  
Overall Performance ◽  
Flow Blockage

In order to investigate the effect of seal cavity leakage flow on a compressor’s performance and the interaction mechanism between the leakage flow and the main flow, a one-stage compressor with a cavity under the shrouded stator was numerically simulated using an inhouse circumferentially averaged through flow program. The leakage flow from the shrouded stator cavity was calculated simultaneously with main flow in an integrated manner. The results indicate that the seal cavity leakage flow has a significant impact on the overall performance of the compressor. For a leakage of 0.2% of incoming flow, the decrease in the total pressure ratio was 2% and the reduction of efficiency was 1.9 points. Spanwise distribution of the flow field variables of the shrouded stator shows that the leakage flow leads to an increased flow blockage near the hub, resulting in drop of stator performance, as well as a certain destructive effect on the flow field of the main passage.

Vortex shedding from a circular cylinder in moderate-Reynolds-number shear flow

1980 ◽  
Vol 101 (4) ◽  
pp. 721-735 ◽  
Author(s):  
Masaru Kiya ◽  
Hisataka Tamura ◽  
Mikio Arie
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Shear Flow ◽  
Vortex Shedding ◽  
Transverse Velocity ◽  
Number Range ◽  
Uniform Shear ◽  
Reynolds Number Range ◽  
Moderate Reynolds Number ◽  
Shear Parameter

The frequency of vortex shedding from a circular cylinder in a uniform shear flow and the flow patterns around it were experimentally investigated. The Reynolds number Re, which was defined in terms of the cylinder diameter and the approaching velocity at its centre, ranged from 35 to 1500. The shear parameter, which is the transverse velocity gradient of the shear flow non-dimensionalized by the above two quantities, was varied from 0 to 0·25. The critical Reynolds number beyond which vortex shedding from the cylinder occurred was found to be higher than that for a uniform stream and increased approximately linearly with increasing shear parameter when it was larger than about 0·06. In the Reynolds-number range 43 < Re < 220, the vortex shedding disappeared for sufficiently large shear parameters. Moreover, in the Reynolds-number range 100 < Re < 1000, the Strouhal number increased as the shear parameter increased beyond about 0·1.

Heat Transfer for High Aspect Ratio Rectangular Channels in a Stationary Serpentine Passage With Turbulated and Smooth Surfaces

2013 ◽  
Author(s):  
Matthew A. Smith ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios ◽  
Parallel Configuration

Heat transfer distributions are presented for a stationary three passage serpentine internal cooling channel for a range of engine representative Reynolds numbers. The spacing between the sidewalls of the serpentine passage is fixed and the aspect ratio (AR) is adjusted to 1:1, 1:2, and 1:6 by changing the distance between the top and bottom walls. Data are presented for aspect ratios of 1:1 and 1:6 for smooth passage walls and for aspect ratios of 1:1, 1:2, and 1:6 for passages with two surfaces turbulated. For the turbulated cases, turbulators skewed 45° to the flow are installed on the top and bottom walls. The square turbulators are arranged in an offset parallel configuration with a fixed rib pitch-to-height ratio (P/e) of 10 and a rib height-to-hydraulic diameter ratio (e/Dh) range of 0.100 to 0.058 for AR 1:1 to 1:6, respectively. The experiments span a Reynolds number range of 4,000 to 130,000 based on the passage hydraulic diameter. While this experiment utilizes a basic layout similar to previous research, it is the first to run an aspect ratio as large as 1:6, and it also pushes the Reynolds number to higher values than were previously available for the 1:2 aspect ratio. The results demonstrate that while the normalized Nusselt number for the AR 1:2 configuration changes linearly with Reynolds number up to 130,000, there is a significant change in flow behavior between Re = 25,000 and Re = 50,000 for the aspect ratio 1:6 case. This suggests that while it may be possible to interpolate between points for different flow conditions, each geometric configuration must be investigated independently. The results show the highest heat transfer and the greatest heat transfer enhancement are obtained with the AR 1:6 configuration due to greater secondary flow development for both the smooth and turbulated cases. This enhancement was particularly notable for the AR 1:6 case for Reynolds numbers at or above 50,000.

Hydrodynamic Loading on Macro-Roughened Cylinders of Various Aspect Ratios

1989 ◽  
Vol 111 (3) ◽  
pp. 214-222 ◽  
Author(s):  
A. Theophanatos ◽  
J. Wolfram
Keyword(s):  
Offshore Structures ◽  
Water Tank ◽  
Fluid Loading ◽  
Test Rig ◽  
Test Program ◽  
Number Range ◽  
Marine Fouling ◽  
Aspect Ratios ◽  
The Uk ◽  
Regular Arrays

This paper describes experiments which comprise part of the UK joint SERC/industry-sponsored program on fluid loading. The experiments have been undertaken in a novel test rig which accelerates a cylinder from rest to a constant velocity in a still water tank and cover the Reynolds number range 105 to 106. Results are presented for 30 cylinders ranging in diameter from 150 mm to 400 mm. The test program comprised: (a) cylinders with different distributions of marine growth (mussels and kelp) and artificial roughness at low surface cover; (b) fully sand/gravel-roughened cylinders with aspect ratios (L/D) from 3.75 to 10 and relative roughness (k/D) up to 0.025; (c) cylinders covered in regular arrays of pyramids at (k/D) up to 0.1. Based on the results, some tentative conclusions are drawn about the estimation of the effect of marine fouling on the fluid loading of offshore structures.

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