External friction of cermet powders in the low-pressure region

1969 ◽  
Vol 8 (7) ◽  
pp. 577-580
Author(s):  
M. V. Mal'tsev ◽  
A. N. Nikolaev
Keyword(s):  
Low Pressure ◽  
External Friction ◽  
Pressure Region

Unprecedented CO2 adsorption behaviour by 5A-type zeolite discovered in lower pressure region and at 300 K

2021 ◽  
Author(s):  
Akira Oda ◽  
Suguru Hiraki ◽  
Eiji Harada ◽  
Ikuka Kobayashi ◽  
Takahiro Ohkubo ◽  
...  
Keyword(s):  
Pressure Range ◽  
Co2 Adsorption ◽  
Low Pressure ◽  
Lower Pressure ◽  
Dft Studies ◽  
Adsorption Behaviour ◽  
Zeolite Sample ◽  
Pressure Region ◽  
Type Zeolite ◽  
Efficient Adsorbent

The NaCaA-85 zeolite sample which works as an efficient adsorbent for CO2 at RT and in low pressure range was found and its specificity is nicely explained by the model composed of CO2 pinned by two types of Ca2+ ions through far-IR and DFT studies.

Exploration of Characteristics Governing Dynamics of Whirlwinds: Application to Dust Devils

2017 ◽  
Vol 72 (8) ◽  
pp. 763-778
Author(s):  
Sanjay Kumar Pandey ◽  
Jagdish Prasad Maurya
Keyword(s):  
Physical Phenomenon ◽  
Radial Pressure ◽  
Buffer Zone ◽  
Vertical Gradient ◽  
Azimuthal Velocity ◽  
Low Pressure ◽  
Dust Devils ◽  
Growth And Survival ◽  
Pressure Region ◽  
Upward Direction

AbstractIt is intended to model mathematically an ideal whirlwind which characterises this geo-physical phenomenon and eventually helps us decode the inherent dynamics. A dense cylindrical aerial mass is taken into consideration surrounding a rarer aerial region in order to keep a radial favourable gradient of pressure to sustain a rotational motion. It has been concluded that the whirlwind will survive as long as the low pressure region exists. The vertical pressure gradient also plays an equally important role. Since it is not connected to any cloud and the axial velocity is in the vertically upward direction, the momentary vertical gradient of pressure is required for its growth and survival. Horizontal ambient winds that rush towards low pressure zone, crush the air in the buffer zone, and turn vertically upward may also take the dust carried with them visibly to some height. It is considered that the angular azimuthal velocity varies within the annulus. An inference is that no whirlwind without a low pressure region within it can survive. This may be termed as the fundamental characteristic of whirlwind. It is further concluded that if the radial pressure difference between the outermost and innermost layers is larger, the whirlwind is thicker and consequently, it will last longer. Moreover, another conclusion arrived at is that the angular velocity will vanish if the inner radius is zero.

High Density Cascaded Arc Produced Plasma Expanding in a Low Pressure Region

2004 ◽  
Vol 44 (56) ◽  
pp. 496-502
Author(s):  
R. P. Dahiya ◽  
N. Kumari ◽  
V. P. Veremiyenko ◽  
G. J. van Rooij ◽  
B. de Groot ◽  
...  
Keyword(s):  
Low Pressure ◽  
High Density ◽  
Pressure Region

An Explanation for Flow Features of Spike-Type Stall Inception in an Axial Compressor Rotor

2012 ◽  
Author(s):  
Kazutoyo Yamada ◽  
Hiroaki Kikuta ◽  
Ken-ichiro Iwakiri ◽  
Masato Furukawa ◽  
Satoshi Gunjishima
Keyword(s):  
Flow Structure ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Leading Edge ◽  
Low Pressure ◽  
Stall Inception ◽  
Compressor Rotor ◽  
Pressure Region ◽  
Casing Pressure ◽  
Edge Separation

The unsteady behavior and three-dimensional flow structure of spike-type stall inception in an axial compressor rotor have been investigated by experimental and numerical analyses. Previous studies have revealed that the test compressor falls into a mild stall after emergence of a spike, in which multiple stall cells, each consisting of a tornado-like vortex, are rotating. However, the flow mechanism from the spike onset to the mild stall remains unexplained. The purpose of this study is to describe the flow mechanism of a spike stall inception in a compressor. In order to capture the transient phenomena of spike-type stall inception experimentally, an instantaneous casing pressure field measurement technique was developed, in which 30 pressure transducers measure an instantaneous casing pressure distribution inside the passage for one blade pitch at a rate of 25 samplings per blade passing period. This technique was applied to obtain the unsteady and transient pressure fields on the casing wall during the inception process of the spike stall. In addition, the details of the three-dimensional flow structure at the spike stall inception have been analyzed by a numerical approach using the detached-eddy simulation (DES). The instantaneous casing pressure field measurement results at the stall inception show that a low-pressure region starts traveling near the leading edge in the circumferential direction just after the spiky wave was detected in the casing wall pressure trace measured near the rotor leading edge. The DES results reveal the vortical flow structure behind the low-pressure region on the casing wall at the stall inception, showing that the low-pressure region is caused by a tornado-like separation vortex resulting from a leading-edge separation near the rotor tip. A leading-edge separation occurs near the tip at the onset of the spike stall and grows to form the tornado-like vortex connecting the blade suction surface and the casing wall. The casing-side leg of the tornado-like vortex generating the low-pressure region circumferentially moves around the leading-edge line. When the vortex grows large enough to interact with the leading edge of the next blade, the leading-edge separation begins to propagate, and then, the compressor falls into a stall with decreasing performance.

Modification of the Density-Pressure Relationship due to the Internal Friction and Cohesion of a Powder Mass Undergoing Closed Die Compaction

2009 ◽  
Vol 409 ◽  
pp. 334-337
Author(s):  
Miriam Kupková
Keyword(s):  
Experimental Data ◽  
Internal Friction ◽  
Low Pressure ◽  
Density Dependent ◽  
Pressure Region ◽  
Powder Mass ◽  
Die Compaction

The existing density-pressure laws for a powder undergoing die compaction fit experimental data very well except for the low-pressure end of curves for some materials (SiC, Al2O3). To improve this, density - pressure relationship was modified by considering the internal friction and cohesion. For constant internal friction and vanishing cohesion, the modified relationship became mathematically equivalent to the existing one. For density-dependent friction, the modified and original relationships were able to provide nearly the same densities at medium and higher pressures but slightly different values at the low-pressure region.

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