Plants, Poisonous (Animals)

Larrea, Manuel Ignacio San Andrés; Larrea, María Dolores San Andrés; Fernàndez, Cèsar

doi:10.1016/b978-0-12-386454-3.00462-0

Cited by 3 publications

(5 citation statements)

References 7 publications

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“…The larger the area of the hysteresis loop, the larger the bearing ability to dissipate mechanical energy. MMFBs also show the same structural characteristics, i.e., stiffness hardening and large material damping capability [22].…”

Section: A Brief Review Of the Literature On Gas Foil Bearingsmentioning

confidence: 96%

“…Earlier work [22] reports that a MMFB will creep over time. Clearly, thicker meshes and with a lesser material compactness will show this undesirable behavior.…”

Section: The Test Bearings: a Metal Mesh Foil Bearing And A Bump-typementioning

confidence: 97%

“…specifications of the two test bearings. San Andrés et al [22] constructed the first prototype of a MMFB (L = D = 28.0 mm) using a 20% compact Copper mesh ring made of 0.3 mm diameter wires. The test MMFB [8], as depicted in Fig.…”

Section: A Brief Review Of the Literature On Gas Foil Bearingsmentioning

confidence: 99%

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A Metal Mesh Foil Bearing and a Bump-Type Foil Bearing: Comparison of Performance for Two Similar Size Gas Bearings

Andrés

Chirathadam

2012

Journal of Engineering for Gas Turbines and Power

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Gas bearings in oil-free microturbomachinery for gas process applications and power generation (<400 kW) must be reliable and inexpensive, ensuring low drag power and thermal stability. Bump-type foil bearings (BEBs) and overleaf-type foil bearings are in use in specialized applications, though their development time (design and prototyping), exotic materials, and excessive manufacturing cost still prevent their widespread usage. Metal mesh foil bearings (MMEBs), on the other hand, are an inexpensive alternative that use common materials and no restrictions on intellectual property. Laboratory testing shows that prototype MMEBs perform similarly as typical BEBs, but offer significantly larger damping to dissipate mechanical energy due to rotor vibrations. This paper details a one-to-one comparison of the static and dynamic forced performance characteristics of a MMEB against a BEB of similar size and showcases the advantages and disadvantages of MMEBs. The bearings for comparison are a generation I BEB and a MMEB, both with a slenderness ratio LID = 1.04. Measurements of rotor lift-off speed and drag friction at start-up and airborne conditions were conducted for rotor speeds to 70 krpm and under identical specific loads (WILD = 0.06 to 0.26 bar). Static load versus bearing elastic deflection tests evidence a typical hardening nonlinearity with mechanical hysteresis, the MMEB showing two to three times more material damping than the BEB. The MMEB exhibits larger drag torques during rotor start-up, and shut-down tests though bearing lift-off happens at lower rotor speeds (~15 krpm). As the rotor becomes airborne, both beatings offer very low drag friction coefficients, ^0.03 for the MMEB and 0.04 for the BEB in the speed range 20-40 krpm. With the bearings floating on ajournai spinning at 50 krpm, the MMEB dynamic direct force coefficients show little frequency dependency, while the BEB stiffness and damping increases with frequency . The BEB has a much larger stiffness and viscous damping coefficients than the MMEB. However, the MMEB material loss factor is at least twice as large as that in the BEB. The experiments show that the MMEB, when compared to the BEB, has a lower drag power and earlier lift-off speed and with dynamic force coefficients having a lesser dependency on whirl frequency excitation.

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Section: A Brief Review Of the Literature On Gas Foil Bearingsmentioning

confidence: 96%

“…Earlier work [22] reports that a MMFB will creep over time. Clearly, thicker meshes and with a lesser material compactness will show this undesirable behavior.…”

Section: The Test Bearings: a Metal Mesh Foil Bearing And A Bump-typementioning

confidence: 97%

See 1 more Smart Citation

A Metal Mesh Foil Bearing and a Bump-Type Foil Bearing: Comparison of Performance for Two Similar Size Gas Bearings

Andrés

Chirathadam

2012

Journal of Engineering for Gas Turbines and Power

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“…An earlier MMFB [7] evidenced sag over time, after several dismantling and reassembly operations; thus resulting in the deterioration of its physical properties. The current study did not investigate the effect of extended exposure of MMFB to high temperature environment or any related material creep over time.…”

Section: Air Inletmentioning

confidence: 99%

“…San Andrés et al [4,7,8] report the static and dynamic performance characteristics of MMFBs operating at rotor speed as high as 60 krpm and with a maximum applied specific load of 46 kPa in experiments conducted at room temperature. The prototype bearings display performance comparable to a similar size, generation I, bump type foil bearing, albeit with a higher mechanical energy dissipation ability (more damping).…”

Section: Introductionmentioning

confidence: 99%

Measurements of Rotordynamic Response and Temperatures in a Rotor Supported on Metal Mesh Foil Bearings

Chirathadam

Andrés

2013

Journal of Engineering for Gas Turbines and Power

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Gas bearings in power generation microturbomachinery (MTM) and for automotive turbocharger applications must demonstrate adequate thermal management without performance degradation while operating in a harsh environment. The paper presents rotor surface temperatures and rotordynamic measurements of a rigid rotor supported on a pair of metal mesh foil bearings (MMFBs) (L = 38.1 mm, D = 36.6 mm). In the tests, to a maximum rotor speed of 50 krpm, an electric cartridge heats the hollow rotor over several hours while a steady inlet airflow rate at^lóOLImin cools the bearings. In the tests with the heater set to a high temperature (max. 200 °C), the rotor and bearing OD temperatures increase by 70 °C and 25 °C, respectively. Most rotor dynamic responses do not show a marked difference for operation under cold (ambient temperature) or hot rotor conditions. A linear rotordynamics structural model with predicted MMFB force coefficients delivers rotor response amplitudes in agreement with the measured ones for operation with the rotor at ambient temperature. There are marked differences in the peak amplitudes when the rotor crosses its (rigid body) critical speeds. The test bearings provide lesser damping than predictions otherwise indicate. Waterfalls of rotor motion show no sub synchronous whirl frequency motions; the rotor-bearing system being stable for all operating conditions. The measurements demonstrate that MMFBs can survive operation with severe thermal gradients, radial and axial, and with little rotordynamic performance changes when the rotor is either cold or hot. The experimental results, accompanied by acceptable predictions of the bearings dynamic forced performance, promote further MMFBs as an inexpensive reliable technology for MTM.

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Distribution of Poisonous Plants in Biomes of the Southern Far East of Russia

Dikareva,

Rumyantsev,

Soldatov

et al. 2023

GES

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Poisonous plants are a collective group of plants of various systematic categories that contain phytotoxins that pose a potential danger to humans and animals. A number of publications both in Russia and abroad are devoted to the problem of patterns of distribution of plants hazardous to human health in connection with environmental factors. This work is a continuation of research into the spread of plants dangerous to humans in Russia. The aim of this work is ecological and geographical analysis of poisonous plants distribution in biomes of the Far East in Russia. Resulted from the research work on the territory of the far-eastern biomes of Russia we revealed 87 the most toxic vascular plant species that belong to 21 plant families. Some of the most poisonous plants of the Russian flora are plants of the genus Aconitum, of the family (Ranunculaceae). About 70 species of this genus grow in Russia, of which 40 are found only in the Far East, since this territory is considered the center of botanical diversity of the genus in question. The cartographical analysis showed that the highest number of poisonous plant species could be found in the south-east regions – in Primorye, the basin of Ussuri river, in the lower and middle course of the river Amur. Based on a map of Russian biomes, optimal habitats for poisonous plants were identified. Maximum number of Aconitum species, as the most poisonous genus of Russian flora, is in the mountain biomes and in the plain forest-steppe biomes in the Amur basin. The types of ecosystems with the maximum abundance and diversity of poisonous plants have been identified. The species richness distribution shows the concentration of poisonous plant species in small mountain biomes and in arid-like biomes. Correlation analysis of relationships between the number of plant species and climatic factors revealed the significant closeness of the correlation with the average annual air temperature (0,66). Maximum correlation closeness appeared to be between number of poisonous plant species per 10 000 km2 and total number of vascular plants per 10 000 km2 (0,81).

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Plants, Poisonous (Animals)

Cited by 3 publications

References 7 publications

A Metal Mesh Foil Bearing and a Bump-Type Foil Bearing: Comparison of Performance for Two Similar Size Gas Bearings

A Metal Mesh Foil Bearing and a Bump-Type Foil Bearing: Comparison of Performance for Two Similar Size Gas Bearings

Measurements of Rotordynamic Response and Temperatures in a Rotor Supported on Metal Mesh Foil Bearings

Distribution of Poisonous Plants in Biomes of the Southern Far East of Russia

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