Analysis of a Rotating Disk System with Axial Cooling Air

2017 ◽  
Vol 34 (2) ◽  
pp. 217-229 ◽  
Author(s):  
Z. Jiao ◽  
S. Fu ◽  
T. Kawakubo ◽  
S. Ohuchida ◽  
H. Tamaki
Keyword(s):  
Flow Rate ◽  
Rotating Disk ◽  
Disk Surface ◽  
Air Cooling ◽  
Disk System ◽  
Rotating Speed ◽  
Cooling Flow ◽  
Disk Rotation ◽  
Eddy Viscosity Model ◽  
Cooling Air

AbstractIn this article, a series of simulations of a rotating disk system with air cooling is introduced. These simulations are performed with the realizable k-ε eddy-viscosity model. Computational results illustrate the effect of the cooling air and disk rotation on the temperature of the disk surface. The maximum rotating disk speed reaches about 78300 rpm and the range of Reynolds numbers based on rotation speed is from about 0.7 × 106 to 3 × 106. The present work shows that the flow structure in the gap, which is on the opposite side of the cooling air, is rather similar to different cooling air flows. The temperature goes up as the rotating speed increases. The temperature in this gap will first decrease when the cooling air increases under lower mass flow rate. But when the cooling air continues to increase, the temperature will rise up indicating the existence of an optimum value of the cooling flow rate.

scholarly journals Effect of Cooling Flow on the Operation of a Hot Rotor-Gas Foil Bearing System

2012 ◽  
Author(s):  
Keun Ryu ◽  
Luis San Andrés
Keyword(s):  
Thermal Management ◽  
Flow Rate ◽  
System Integration ◽  
Damping Ratio ◽  
Temperature Drop ◽  
Test System ◽  
The Body ◽  
Air Cooling ◽  
Cooling Flow ◽  
Management Procedures

Gas foil bearings (GFBs) operating at high temperature rely on thermal management procedures that supply needed cooling flow streams to keep the bearing and rotor from overheating. Poor thermal management not only makes systems inefficient and costly to operate but could also cause bearing seizure and premature system destruction. This paper presents comprehensive measurements of bearing temperatures and shaft dynamics conducted on a hollow rotor supported on two first generation GFBs. The hollow rotor (1.36 kg, 36.51 mm OD and 17.9 mm ID) is heated from inside to reach an outer surface temperature of 120°C. Experiments are conducted with rotor speeds to 30 krpm and with forced streams of air cooling the bearings and rotor. Air pressurization in an enclosure at the rotor mid span forces cooling air through the test GFBs. The cooling effect of the forced external flows is most distinct when the rotor is hottest and operating at the highest speed. The temperature drop per unit cooling flow rate significantly decreases as the cooling flow rate increases. Further measurements at thermal steady state conditions and at constant rotor speeds show that the cooling flows do not affect the amplitude and frequency contents of the rotor motions. Other tests while the rotor decelerates from 30 krpm to rest show that the test system (rigid-mode) critical speeds and modal damping ratio remain nearly invariant for operation with increasing rotor temperatures and with increasing cooling flow rates. Computational model predictions reproduce the test data with accuracy. The work adds to the body of knowledge on GFB performance and operation and provides empirically derived guidance for successful rotor-GFB system integration.

scholarly journals Effect of Cooling Flow on the Operation of a HotRotor-Gas Foil Bearing System

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Keun Ryu ◽  
Luis San Andrés
Keyword(s):  
Thermal Management ◽  
Flow Rate ◽  
System Integration ◽  
Damping Ratio ◽  
Temperature Drop ◽  
Test System ◽  
The Body ◽  
Air Cooling ◽  
Cooling Flow ◽  
Management Procedures

Gas foil bearings (GFBs) operating at high temperature rely on thermal management procedures that supply needed cooling flow streams to keep the bearing and rotor from overheating. Poor thermal management not only makes systems inefficient and costly to operate but could also cause bearing seizure and premature system destruction. This paper presents comprehensive measurements of bearing temperatures and shaft dynamics conducted on a hollow rotor supported on two first generation GFBs. The hollow rotor (1.36 kg, 36.51 mm OD and 17.9 mm ID) is heated from inside to reach an outer surface temperature of 120 °C. Experiments are conducted with rotor speeds to 30 krpm and with forced streams of air cooling the bearings and rotor. Air pressurization in an enclosure at the rotor mid span forces cooling air through the test GFBs. The cooling effect of the forced external flows is most distinct when the rotor is hottest and operating at the highest speed. The temperature drop per unit cooling flow rate significantly decreases as the cooling flow rate increases. Further measurements at thermal steady state conditions and at constant rotor speeds show that the cooling flows do not affect the amplitude and frequency contents of the rotor motions. Other tests while the rotor decelerates from 30 krpm to rest show that the test system (rigid-mode) critical speeds and modal damping ratio remain nearly invariant for operation with increasing rotor temperatures and with increasing cooling flow rates. Computational model predictions reproduce the test data with accuracy. The work adds to the body of knowledge on GFB performance and operation and provides empirically derived guidance for successful rotor-GFB system integration.

Ingress Determination by Means of Laser Light Scattering Inside a Rotor-Stator System

1999 ◽  
Author(s):  
T. Geis ◽  
A. Wiebelt ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Light Scattering ◽  
Laser Light ◽  
Scattered Light ◽  
Rotating Disk ◽  
Ambient Air ◽  
Laser Light Scattering ◽  
New Technique ◽  
Disk System ◽  
Cooling Flow ◽  
Purge Flow

A new method based on laser light scattering was developed to detect a radial inflow of gas inside a rotating-disk system. Ambient air was seeded with small particles that followed the flow. Once entering the wheel space between rotor and stator, these particles crossed a laserbeam emitted by an At+-Laser. The scattered light was detected by a photomultiplier whose electrical output signal was finally processed in a data acquisition system. The signal intensity thereby indicated the strength of ingress. The measuring technique was adapted to a shrouded rotor-stator system in a quiescent environment and an experimental investigation was conducted to determine the minimum cooling flow rate necessary to just prevent ingress (Cw,min) for several seal clearance ratios and two different rotor disk geometries. The results were correlated to the disk rotational Reynolds number and compared with data yielded by applying a pressure criterion. With the rotating disk being 0.5m in diameter and spinning at max. 10000rpm, rotational Reynolds numbers up to 3.8×106 were achieved. The results show an expected behaviour for the seal clearance variation and an unexpected behaviour for the two disk geometries. Compared to the new technique, the pressure criterion underestimates the minimum purge flow. Additional experiments were conducted for a single seal configuration to demonstrate the new method’s capability to acquire the sealing effectiveness. The results are intriguing but also show that further investigations must be conducted to establish this new technique.

Experimental Investigation on the Condensation Efficiency of Humid Air in a Cross-Flow Condenser

2013 ◽  
Author(s):  
Hojin Ahn ◽  
Burhan Gul ◽  
Yavuz Sahin ◽  
Onur Hartoka
Keyword(s):  
Flow Rate ◽  
Single Channel ◽  
Cross Flow ◽  
Condensation Process ◽  
Mixture Flow ◽  
Flow Rates ◽  
Cooling Flow ◽  
Cooling Air Flow ◽  
Cooling Air ◽  
Heat Released

The condensation of steam in the presence of air has been investigated experimentally in the cross-flow flat-plate single-channel condenser. In particular, the condensation efficiency which is defined by the ratio of heat released during the condensation process (the amount of latent heat) to the total heat extracted from the mixture of vapor and non-condensable gas (the sum of latent and sensible heats) is examined as a function of the air-steam mixture temperature and humidity at inlet and the flow rates of the air-steam mixture and cooling air. The preliminary results are obtained with the operating condition of the air-steam mixture flow at 70°C and 80, 85 and 90% relative humidity at inlet. The most notable result is that the condensation efficiency evidently decreases with the increase of the cooling air flow rate. With both mixture and cooling flow rates kept constant, the condensation efficiency increases, as expected, with the increasing air-steam mixture humidity at the inlet. On the other hand, the air-steam mixture flow rate appears to have little effect on the condensation efficiency.

Experimental Analysis of Varied Vortex Reducer Configurations for the Internal Air System of Jet Engine Gas Turbines

2008 ◽  
Author(s):  
Andre´ Gu¨nther ◽  
Wieland Uffrecht ◽  
Erwin Kaiser ◽  
Stefan Odenbach ◽  
Lothar Heller
Keyword(s):  
Flow Rate ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Engine Performance ◽  
Internal Cooling ◽  
Test Rig ◽  
Rotating Speed ◽  
Pressure Losses ◽  
Cooling Flow ◽  
Air System

The continuous improvement of engine performance, combined with strict environmental and safety regulations and the reduction of time and cost of new products, is the major goal of the turbomachinery industry. Particular attention is being focused on the reduction of internal losses and weight, associated with the internal air system. The cooling air is normally bled by holes in the rotor from the main flow of the HP compressor, transported radially inwards towards the shaft and further transferred to the hot parts of the engine. The radial inflow creates vortices induced by the core rotation ratio, which create very high pressure losses and restrict the maximum cooling flow rate. The pressure loss depends strongly on the rotating speed and the mass flow rate. The vortex reducer prevents the development of vortices and therefore reduces the pressure loss. A key area of concern is to optimize the pressure loss concurrent with the use of new light weight or easy to manufacture configurations of vortex reducers. The material presented in this paper describes an experimental study, concentrating on a two cavity test rig for different internal cooling flow concepts. The test rig has steel discs, operating at engine representative flow and temperature conditions and permits several flow and heating modes with axial or/and radial flow configurations. The present work investigates the fluid flow for different vortex reducer configurations at different rotational speeds and its influence on the pressure loss. Particular attention was paid to the influence of size and location of the tubes. The experimental setup and the results concerning the pressure losses for the different configurations are presented.

Fabrication and Characterization of Nife Thin Film Composition Modulated Alloys

1996 ◽  
Vol 451 ◽  
Author(s):  
S. D. Leith ◽  
D. T. Schwartz
Keyword(s):  
Rotation Rate ◽  
Stripping Voltammetry ◽  
Rotating Disk ◽  
Oscillation Period ◽  
Rotating Disk Electrode ◽  
Disk Rotation ◽  
Rate Oscillation ◽  
Composition And Structure ◽  
Spatially Periodic

ABSTRACTDescribed are results showing that an oscillating flow-field can induce spatially periodic composition variations in electrodeposited NiFe films. Flow-induced NiFe composition modulated alloys (CMA's) were deposited on the disk of a rotating disk electrode by oscillating the disk rotation rate during galvanostatic plating. Deposit composition and structure were investigated using potentiostatic stripping voltammetry and scanning probe microscopy. Results illustrate a linear relationship between the composition modulation wavelength and the flow oscillation period. CMA's with wavelengths less than 10 nm can be fabricated when plating with a disk rotation rate oscillation period less than 3 seconds.

Effect of pre-swirl nozzle closure modes on unsteady flow and heat transfer characteristics in a pre-swirl system of aero-engine

2021 ◽  
pp. 095441002110191
Author(s):  
Gaowen Liu ◽  
Zhao Lei ◽  
Aqiang Lin ◽  
Qing Feng ◽  
Yan Chen
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Temperature Drop ◽  
Thermodynamic Characteristics ◽  
Circumferential Direction ◽  
Temperature Changes ◽  
Air Supply ◽  
Cooling Air

The pre-swirl system is of great importance for temperature drop and cooling air supply. This study aims to investigate the influencing mechanism of heat transfer, nonuniform thermodynamic characteristics, and cooling air supply sensitivity in a pre-swirl system by the application of the flow control method of the pre-swirl nozzle. A novel test rig was proposed to actively control the supplied cooling air mass flow rate by three adjustable pre-swirl nozzles. Then, the transient problem of the pre-swirl system was numerically conducted by comparison with 60°, 120°, and 180° rotating disk cavity cases, which were verified with the experiment results. Results show that the partial nozzle closure will aggravate the fluctuation of air supply mass flow rate and temperature. When three parts of nozzles are closed evenly at 120° in the circumferential direction, the maximum value of the nonuniformity coefficient of air supply mass flow rate changes to 3.1% and that of temperature changes to 0.25%. When six parts of nozzles are closed evenly at 60° in the circumferential direction, the maximum nonuniformity coefficient of air supply mass flow rate changes to 1.4% and that of temperature changes to 0.20%. However, different partial nozzle closure modes have little effect on the average air supply parameters. Closing 14.3% of the nozzle area will reduce the air supply mass flow rate by 9.9% and the average air supply temperature by about 1 K.

Effect of Active Modulation of Through-Casing Coolant Injection on Turbine Efficiency

2017 ◽  
Author(s):  
Brian M. T. Tang ◽  
Marko Bacic ◽  
Peter T. Ireland
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Total Pressure ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Turbine Efficiency ◽  
Coolant Injection ◽  
Cooling Air

This paper presents a computational investigation into the impact of cooling air injected through the stationary over-tip turbine casing on overall turbine efficiency. The high work axial flow turbine is representative of the high pressure turbine of a civil aviation turbofan engine. The effect of active modulation of the cooling air is assessed, as well as that of the injection locations. The influence of the through-casing coolant injection on the turbine blade over-tip leakage flow and the associated secondary flow features are examined. Transient (unsteady) sliding mesh simulations of a one turbine stage rotor-stator domain are performed using periodic boundary conditions. Cooling air configurations with a constant total pressure air supply, constant mass flow rate and actively controlled total pressure supply are assessed for a single geometric arrangement of cooling holes. The effects of both the mass flow rate of cooling air and the location of its injection relative to the turbine rotor blade are examined. The results show that all of the assessed cooling configurations provided a benefit to turbine row efficiency of between 0.2 and 0.4 percentage points. The passive and constant mass flow rate configurations reduced the over-tip leakage flow, but did so in an inefficient manner, with decreasing efficiency observed with increasing injection mass flow rate beyond 0.6% of the mainstream flow, despite the over-tip leakage mass flow rate continuing to reduce. By contrast, the active total pressure controlled injection provided a more efficient manner of controlling this leakage flow, as it permitted a redistribution of cooling air, allowing it to be applied in the regions close to the suction side of the blade tip which more directly reduced over-tip leakage flow rates and hence improved efficiency. Cooling air injected close to the pressure side of the rotor blade was less effective at controlling the leakage flow, and was associated with increased aerodynamic loss in the passage vortex.

Partial Admission, Axial Impulse Type Turbine Design and Partial Admission Radial Turbine Test for SCO2 Cycle

2017 ◽  
Author(s):  
Hyungki Shin ◽  
Junhyun Cho ◽  
Young-Jin Baik ◽  
Jongjae Cho ◽  
Chulwoo Roh ◽  
...  
Keyword(s):  
Axial Force ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Small Diameter ◽  
Volume Flow ◽  
Working Fluid ◽  
Rotating Speed ◽  
Turbo Generator ◽  
Partial Admission ◽  
Reduce Development Time

Power generation cycle — typically Brayton cycle — to use CO2 at supercritical state as working fluid have been researched many years because this cycle increase thermal efficiency of cycle and decrease turbomachinery size. But small turbomachinery make it difficult to develop proto type Supercritical Carbon dioxide (S-CO2) cycle equipment of lab scale size. KIER (Korea Institute of Energy Research) have been researched S-CO2 cycle since 2013. This paper is about 60kWe scale and sub-kWe class turbo generator development for applying to this S-CO2 cycle at the lab scale. A design concept of this turbo-generator is to use commercially available components so as to reduce development time and increase reliability. Major problem of SCO2 turbine is small volume flow rate and huge axial force. High density S-CO2 was referred as advantage of S-CO2 cycle because it make small turbomachinery possible. But this advantage was not valid in lab-scale cycles under 100kW because small amount volume flow rate means high rotating speed and too small diameter of turbine to manufacture it. Also, high inlet and outlet pressure make huge axial force. To solve these problem, KIER have attempt various turbines. In this paper, these attempts and results are presented and discussed.

Heat Transfer and Pressure Drop in a Converging Pedestal Array With Exit Area Variation

2018 ◽  
Author(s):  
L. W. Soma ◽  
F. E. Ames ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Rate ◽  
Film Cooling ◽  
Reynolds Numbers ◽  
Flow Path ◽  
Internal Cooling ◽  
Channel Measurements ◽  
Trailing Edge ◽  
Cooling Air

The trailing edge of a vane is one of the most difficult areas to cool due to a narrowing flow path, high external heat transfer rates, and deteriorating external film cooling protection. Converging pedestal arrays are often used as a means to provide internal cooling in this region. The thermally induced stresses in the trailing edge region of these converging arrays have been known to cause failure in the pedestals of conventional solidity arrays. The present paper documents the heat transfer and pressure drop through two high solidity converging rounded diamond pedestal arrays. These arrays have a 45 percent pedestal solidity. One array which was tested has nine rows of pedestals with an exit area in the last row consistent with the convergence. The other array has eight rows with an expanded exit in the last row to enable a higher cooling air flow rate. The expanded exit of the eight row array allows a 30% increase in the coolant flow rate compared with the nine row array for the same pressure drop. Heat transfer levels correlate well based on local Reynolds numbers but fall slightly below non converging arrays. The pressure drop across the array naturally increases toward the trailing edge with the convergence of the flow passage. A portion of the cooling air pressure drop can be attributed to acceleration while a portion can be attributed to flow path losses. Detailed array static pressure measurements provide a means to develop a correlation for the prediction of pressure drop across the cooling channel. Measurements have been acquired over Reynolds numbers based on exit flow conditions and the characteristic pedestal length scale ranging from 5000 to over 70,000.

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