A Self-Starting Hydrodynamic Gas Bearing

An experimental self-starting hydrodynamic gas bearing was designed, built, and tested. This bearing operates on the principle that the bearing is started and stopped hydrostatically by means of an air supply which is generated by the bearing itself. For this purpose, a portion of the self-starting bearing is executed as a herringbone grooved bearing, which performs as a pump, charging a reservoir during hydrodynamic operation of the bearing. The reservoir air supply generated by the herringbone bearing is used for hydrostatic operation of the bearing during starts and stops. Starting and stopping of the experimental bearing was demonstrated using the air supply generated by the herringbone bearing. An equation was derived for the mass flow rate of the herringbone bearing pump.

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

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/09544100211019145 ◽

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.

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Modeling of the Transient Response for Compressible Air Cushion Vehicles (ACV)

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.152-154.560 ◽

2012 ◽

Vol 152-154 ◽

pp. 560-567 ◽

Cited By ~ 1

Author(s):

Ahmed S. Sowayan ◽

Khalid A. Alsaif

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Settling Time ◽

The Self ◽

Design Stage ◽

Transient Time ◽

Bernoulli’S Equation ◽

Air Cushion ◽

Air Cushion Vehicles

A model for compressible Air Cushion Vehicles (ACV) is presented. In this model the compressible Bernoulli's equation and the Newton's second law of motion are used to predict the dynamic behavior of the heave response of the ACV in both time and frequency domains. The mass flow rate inside the air cushion of this model is assumed to be constant. The self excited response and the cushion pressure of the ACV is calculated to understand the behavior of the system in order to assist in the design stage of such systems. It is shown in this study that the mass flow rate and the length of the vehicle's skirt are the most significant parameters which control the steady state behavior of the self excited oscillations of the ACV. An equation to predict the transient time of the oscillatory response or the settling time in terms of the system parameters of the ACV is developed. Based on the developed equations, the optimum parameters of the ACV that lead to minimum settling time are obtained.

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Permeability and Inertial Coefficients of Porous Media for Air Bearing Feeding Systems

Journal of Tribology ◽

10.1115/1.2768068 ◽

2007 ◽

Vol 129 (4) ◽

pp. 705-711 ◽

Cited By ~ 16

Author(s):

G. Belforte ◽

T. Raparelli ◽

V. Viktorov ◽

A. Trivella

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Darcy’S Law ◽

Darcy's Law ◽

Flow Rates ◽

Mass Flow Rates ◽

Thrust Pad ◽

Gas Bearing ◽

Forchheimer’S Law

In porous resistances, Darcy’s law provides a good approximation of mass flow rate when the differences between upstream and downstream pressures are sufficiently small. In this range, the mass flow rates are proportional to the porous resistance’s permeability. For gas bearings, the pressure difference is normally higher, and it is known experimentally that the mass flow rates are lower than would result from Darcy’s law. Forchheimer’s law adds an inertial term to Darcy’s law and, when an appropriate coefficient is selected for this term, provides a good approximation of flow rates for the same applications even with the highest pressure differences. This paper presents an experimental and theoretical investigation of porous resistances used in gas bearing and thrust pad supply systems. The porous resistances considered in the investigation were made by sintering bronze powders with different grain sizes to produce cylindrical inserts that can be installed in bearing supply devices. The paper describes the test setup and experimental results obtained for: (i) mass flow rate through single porous resistances at different upstream and downstream pressures and (ii) mass flow rate and pressure distribution on a pneumatic pad featuring the same porous resistances. The theoretical permeability of the chosen porous resistances was calculated, and the results from setup (i) were then used to obtain experimental permeability and to determine the inertial coefficients. The results, which are expressed as a function of the Reynolds number, confirmed the validity of using Forchheimer’s law. The mass flow rates from setup (ii) were compared to those from setup (i) at the same pressure differentials across the resistance.

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Assessment of Porous Type Gas Bearings: Measurements of Bearing Performance and Rotor Vibrations

Volume 7B: Structures and Dynamics ◽

10.1115/gt2016-57876 ◽

2016 ◽

Cited By ~ 3

Author(s):

Luis San Andrés ◽

Travis A. Cable ◽

Yong Zheng ◽

Oscar De Santiago ◽

Drew Devitt

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Load Capacity ◽

Gas Bearings ◽

Rotor Spinning ◽

Supply Pressure ◽

Seizure Event ◽

Flow Drag ◽

Gas Bearing

Gas bearings are an attractive means of load support for rotating machinery due to their low mechanical power losses and dispensing of expensive lubrication systems. A subset of gas bearing technology, porous type gas bearings utilize a porous material as a means of feeding externally pressurized gas (typically air) to the bearing clearance region. When compared to typical orifice type hydrostatic bearings, porous bearings distribute pressurized gas more uniformly into the film clearance, thus resulting in a higher load capacity for similar flow rates [1]. The majority of the literature on porous type gas bearings focuses on the numerical evaluation of cylindrical bushings, yet experimental data on their performance is scant. As a follow up to Ref. [2], the paper presents an analysis of measurements of flow, drag torque and rotordynamic response of a large (100 mm OD, ∼275 N) rotor supported on two tilting pad (five-pad) porous journal bearings (specific load∼19 kPa). Measurements of air mass flow into the bearings, with and without the rotor in place, show that the film clearance offers little restriction. The mass flow rate is proportional to the supply pressure and lead to an estimated permeability coefficient. In operation with various levels of supply pressure and with the rotor spinning to 8 krpm (133 Hz, surface speed ∼42 m/s), several rotordynamic response tests (masses up to 6.9 gram) show the rotor amplitude of synchronous response is proportional to the mass imbalance; hence demonstrating the system is linear. Finally, rotor speed coast down tests from 8 krpm show that the bearings offer little drag friction; and increasing the supply pressure gives to lesser drag. The measurements verify the pair of gas bearings support effectively the rigid rotor with little expense in mass flow rate delivered to them. Most importantly, while operating at 10 krpm with a large added imbalance, the system survived a seizure event with little damage to the rotor and bearings, both restored to a near pristine condition after a simple cleaning procedure.

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Analisis Kinerja Sistem Kompresor Udara Botol Angin Sebagai Sumber Pembangkit Generator Di Laboratorium Engine Hall Politeknik Ilmu Pelayaran Makassar

Jurnal Sinergi Jurusan Teknik Mesin ◽

10.31963/sinergi.v19i1.2734 ◽

2021 ◽

Vol 19 (1) ◽

pp. 25

Author(s):

Syahrisal Syahrisal

Keyword(s):

Mass Flow Rate ◽

Output Power ◽

Mass Flow ◽

Flow Rate ◽

Quantitative Method ◽

Compressed Air ◽

Auxiliary Equipment ◽

Air Mass ◽

Air Compressor ◽

Air Supply

The compressed air supply device on the ship is auxiliary equipment used for starting the engine. The purpose of this study is to analyze the performance of the air compressor as a generator source in the Engine Hall laboratory. This study seeks to determine the performance of the compressor sistem as a generator drive in the Engine Hall Laboratory and the efficiency of the compressor sistem. The methodology used in this research is a quantitative method by calculating the performance of the compressor sistem as a generator, including compressors and wind bottles. The conclusion of this study is that the smaller the pressure exerted when compressing the air into the wind bottle, the smaller the mass of air that enters the wind bottle, likewise the greater the pressure exerted during compression, the greater the mass that enters the wind bottle (202, 65 kPa with an air mass of 1.0393 kg and 2431.8 kPa with an air mass of 12.162 kg). The smaller the pressure exerted when compressing the air to the wind bottle, the greater the mass flow rate of air in the tube (202.65 kPa with an air mass flow rate of 0.0297 kg/sec and 2431.8 kPa with an air mass flow rate of 0.0115 kg / sec). The greater the sistem output power, the greater the efficiency of the compressor sistem and the smaller the sistem output power, the smaller the efficiency of the compressor sistem (1000 Watt with an efficiency of 26.311% and 218 Watt with an efficiency of 5.742%).

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