Damn the Experts and Full Speed Ahead

A simulation program for transient analysis of the start-up procedure of heavy duty gas turbines for power generation has been constructed. Unsteady one-dimensional conservation equations are used and equation sets are solved numerically using a fully implicit method. A modified stage-stacking method has been adopted to estimate the operation of the compressor. Compressor stages are grouped into three categories (front, middle, rear), to which three different stage characteristic curves are applied in order to consider the different low-speed operating characteristics. Representative start-up sequences were adopted. The dynamic behavior of a representative heavy duty gas turbine was simulated for a full start-up procedure from zero to full speed. Simulated results matched the field data and confirmed unique characteristics such as the self-sustaining and the possibility of rear-stage choking at low speeds. Effects of the estimated schedules on the start-up characteristics were also investigated. Special attention was paid to the effects of modulating the variable inlet guide vane on start-up characteristics, which play a key role in the stable operation of gas turbines.

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HORMONE STUDIES WITH THE ULTRACENTRIFUGE

Journal of Experimental Medicine ◽

10.1084/jem.68.1.1 ◽

1938 ◽

Vol 68 (1) ◽

pp. 1-16 ◽

Cited By ~ 7

Author(s):

James A. Chiles ◽

Aura E. Severinghaus

Keyword(s):

Compressed Air ◽

Maximum Speed ◽

Driving Mechanism ◽

Air Bearing ◽

Centrifugal Field ◽

Air Turbine ◽

Full Speed ◽

Short Time ◽

Centrifuge Rotor

1. An ultracentrifuge is described in which the rotor is driven by a compressed air turbine, and is spun in an evacuated chamber to minimize friction and heating. The rotating parts are supported by a cushion of air in an air bearing. 2. The centrifuge rotor holds 10 test tubes inclined at 45° to the axis, and has a capacity of 55 cc. It is operated at a maximum speed of 51,000 R.P.M., which develops at the top of the fluid column in the test tubes a centrifugal field of over 100,000 times gravity, and at the bottom of the fluid column a field of over 200,000 times gravity. 3. By means of a reverse turbine, the rotor can be brought to a stop from full speed in a relatively short time. 4. A precession damping device is described, which effectively damps the precession and wobbling of the rotor that usually occurs at certain speeds in machines of this type. 5. A relatively long section of shaft is used between the centrifuge rotor and lower bearings. This prevents vibrations from being appreciably transmitted through the shaft to the lower bearings and driving mechanism, and results in a negligible wear on the bearings. 6. The driving mechanism is designed so that the positions of its parts are adjustable, and so that the driving mechanism may be dismantled without disturbing these adjustments.

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Speed Sensorless Control of Synchronous Reluctance Motor At Full Speed Range

10.1109/cieec50170.2021.9510684 ◽

2021 ◽

Author(s):

Bao Zhenfeng ◽

Wei Sun ◽

Dong Jiang

Keyword(s):

Sensorless Control ◽

Speed Sensorless ◽

Synchronous Reluctance Motor ◽

Reluctance Motor ◽

Speed Range ◽

Full Speed

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Entrainment of Air at the Transoms of Full-Scale Surface Ships

Journal of Ship Research ◽

10.5957/jsr.2015.59.1.49 ◽

2015 ◽

Vol 59 (01) ◽

pp. 49-65

Author(s):

Eric J. Terrill ◽

Genevieve R.L. Taylor

Keyword(s):

Initial Conditions ◽

Air Entrainment ◽

Full Scale ◽

Far Field ◽

Two Phase ◽

Cfd Models ◽

Surface Ship ◽

Full Speed ◽

Bubbly Wake ◽

Scale Surface

We report on the results from a series of full-scale trials designed to quantify the air entrainment at the stern of an underway vessel. While an extremely complex region to model air entrainment due to the confluence of the breaking transom wave, bubbles from the bow, turbulence from the hull boundary layer, and bubbles and turbulence from propellers, the region is a desirable area to characterize and understand because it serves as the initial conditions of a ship's far-field bubbly wake. Experiments were conducted in 2003 from R/V Revelle and 2004 from R/VAthena II using a custombuilt conductivity probe vertical array that could be deployed at the blunt transom of a full-scale surface ship to measure the void fraction field. The system was designed to be rugged enough to withstand the full speed range of the vessels. From the raw timeseries data, the entrainment of air at speeds ranging from 2.1 to 7.2 m/s is computed at various depths and beam locations. The data represent the first such in-situ measurements from a full-scale vessel and can be used to validate two-phase ship hydrodynamic CFD codes and initialize far-field, bubbly wake CFD models.

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