Numerical investigation of subsynchronous vibration in floating ring bearings

Floating ring bearings are popular among turbochargers due to their simplicity and reliability. The disappearance of subsynchronous vibration with the increase of shaft speed in a low oil-supplied pressure floating ring bearing is reported by Hatakenaka and Yanai. This finding may help eliminate the noise and decrease the loss of turbochargers. This work aims to explain this phenomenon in the low oil-supplied floating ring bearing using computational fluid dynamic. Steady computational fluid dynamic calculation is conducted to validate the effect of air entrainment. Transient computational fluid dynamic calculation method with mesh motion method is established. The subsynchronous vibration of the shaft can be obtained by discrete Fourier transform analysis. The results are validated by comparing them with those in the literature. It is found that the disappearance of the subsynchronous vibration is the result of the change in lubricant properties caused by the air entrainment.

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Numerical Investigation of the Flow around a Feather Shuttlecock with Rotation

Proceedings ◽

10.3390/proceedings2020049028 ◽

2020 ◽

Vol 49 (1) ◽

pp. 28

Author(s):

John Hart ◽

Jonathan Potts

Keyword(s):

Reynolds Number ◽

Wind Tunnel ◽

Drag Coefficient ◽

Numerical Investigation ◽

Computational Fluid Dynamic ◽

High Reynolds Number ◽

Fluid Dynamic ◽

Flow Structures ◽

Drag Forces ◽

High Reynolds

This paper presents the first scale resolving computational fluid dynamic (CFD) investigation of a geometrically realistic feather shuttlecock with rotation at a high Reynolds number. Rotation was found to reduce the drag coefficient of the shuttlecock. However, the drag coefficient is shown to be independent of the Reynolds number for both rotating and statically fixed shuttlecocks. Particular attention is given to the influence of rotation on the development of flow structures. Rotation is shown to have a clear influence on the formation of flow structures particularly from the feather vanes, and aft of the shuttlecock base. This further raises concerns regarding wind tunnel studies that use traditional experimental sting mounts; typically inserted into this aft region, they have potential to compromise both flow structure and resultant drag forces. As CFD does not necessitate use of a sting with proper application, it has great potential for a detailed study and analysis of shuttlecocks.

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Investigation of Air-Oil Distribution of Low Oil-Supplied Pressure Grooved Ring Floating Ring Bearing

Volume 7B: Structures and Dynamics ◽

10.1115/gt2018-75887 ◽

2018 ◽

Author(s):

Wang Yan ◽

Li Yuhong

Keyword(s):

Thermal Effect ◽

Fluid Dynamic ◽

Great Influence ◽

Air Entrainment ◽

Simulation Method ◽

Speed Ratio ◽

Good Prediction ◽

Shaft Speed ◽

Entrainment Effect ◽

Cfd Method

Oil lubricated floating ring bearings (FRBs) are popular among the passenger vehicle turbochargers. Air entrainment occurs in the inner film of the FRB under low oil-supplied pressure. Air entrainment has great impact on the bearing performance. Experiments reported that FRB with a circumferential groove on the ring shows lower ring-to-shaft speed and improved stabilizing capacity at high shaft speed. This study aims to construct the numerical simulation method to predict the multiphase flow in the grooved ring (GR) FRB. Computational fluid dynamic (CFD) method is adopted to obtain the bearing performance considering air entrainment. CFD calculation can obtain detailed air entrainment results that experiment cannot provide. Calculation results are compared with the experimental results to validate the proposed CFD method. Analysis shows the great influence of grooved ring on the air entrainment. Air entrainment contributes to the decrease of the ring-to-shaft speed ratio in the GR FRB. The proposed CFD calculation considering air entrainment can give good prediction of the ring rotation speed under different shaft speed. Besides, detailed analysis of the effective viscosity indicates that outer film is mainly affected by thermal effect. Inner film is affected by both thermal effect and air entrainment effect, where latter is more predominant.

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Numerical investigation of a nanofluidic heat exchanger by employing computational fluid dynamic

Journal of Thermal Analysis and Calorimetry ◽

10.1007/s10973-020-10355-0 ◽

2020 ◽

Author(s):

Dongtao Hu ◽

Jing Wang ◽

Qi Tang

Keyword(s):

Heat Exchanger ◽

Numerical Investigation ◽

Computational Fluid Dynamic ◽

Fluid Dynamic

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Laser Optical Flow Measurements and Computational Fluid Dynamic Calculation of Spray Tower Hydrodynamics

Chemical Engineering Research and Design ◽

10.1205/cherd.04071 ◽

2005 ◽

Vol 83 (5) ◽

pp. 492-507 ◽

Cited By ~ 8

Author(s):

C. Weiss ◽

U. Wieltsch

Keyword(s):

Optical Flow ◽

Computational Fluid Dynamic ◽

Fluid Dynamic ◽

Dynamic Calculation ◽

Flow Measurements ◽

Spray Tower

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Ignition, lift-off, and soot formation studies in n-dodecane split injection spray-flames

International Journal of Engine Research ◽

10.1177/1468087417700778 ◽

2017 ◽

Vol 18 (10) ◽

pp. 1077-1087 ◽

Cited By ~ 8

Author(s):

Ahmed Abdul Moiz ◽

Khanh D Cung ◽

Seong-Young Lee

Keyword(s):

Numerical Simulation ◽

Computational Fluid Dynamic ◽

Soot Formation ◽

Fluid Dynamic ◽

Mixture Fraction ◽

Air Entrainment ◽

Flame Stabilization ◽

Propagation Mechanism ◽

Constant Density ◽

Lift Off

A close-coupled double injection strategy with two 0.5-ms injections separated by a 0.5-ms dwell is implemented. Studies are performed in a constant volume pre-burn type combustion vessel over two ambient temperatures (900 and 800 K) at constant density (22.8 kg/m3) with 15% O2 by volume in the ambient. The aim of this work is to investigate the establishment and dependence of ignition delay and flame stabilization on the ambient temperature conditions especially for the main injection, and thereby investigating eventual soot production. Simultaneous schlieren and planar laser -induced fluorescence experiments as well as three-dimensional Reynolds-averaged numerical simulation computational fluid dynamic modeling with chemical kinetics in every computational fluid dynamic cell were performed. It was observed experimentally that at 900 K, the second injection is injected in a high-temperature combustion recessed ambient of the first injection whereas at 800 K it is injected in a low temperature, possibly reactive species environment. It was found from Reynolds-averaged numerical simulation modeling that combustion recession at 900 K in the present case entails rich presence of hydroxyl radical species and also the ambient of 800 K is source of reactive radicals like peroxides, leading to acceleration of main ignition. Flame stabilization of the second injection occurs closer to the injector due to short ignition delays with flame being sustained in the fuel–air premixing zone. Flame stabilization of the second injection was found to follow a premixed flame propagation mechanism. Investigation in mixture fraction and temperature space of pilot-main spray combustion revealed that the lower lift-off of main results in lower air-entrainment which causes richer ignition of main resulting in quicker and higher soot formation. The effect of the second injection in enhancing the oxidation of soot from the first injection by inducing enhanced mixing was also revealed.

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