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Total pressure

About: Total pressure is a research topic. Over the lifetime, 5199 publications have been published within this topic receiving 66658 citations.


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TL;DR: In this paper, the surface structure of a precision forged blade was engraved in two 0.3mm-thick sheets of copper with the above-mentioned enlarging factor, which was applied as inlays to the pressure and suction side to avoid additional effects due to thickening of the blade contour.
Abstract: A highly loaded compressor cascade, which features a chord length ten times larger than in real turbomachinery, is used to perform an investigation of the influence of technical surface roughness. The surface structure of a precision forged blade was engraved in two 0.3-mm-thick sheets of copper with the above-mentioned enlarging factor (Leipold and Fottner, 1996). To avoid additional effects due to thickening of the blade contour, the sheets of copper are applied as inlays to the pressure and suction side. At the high-speed cascade wind tunnel, the profile pressure distribution and the total pressure distribution at the exit measurement plane were measured for the rough and the smooth blade for a variation of inlet flow angle and inlet Reynolds number. For some interesting flow conditions, the boundary layer development was investigated with laser-two-focus anemometry and one-dimensional hot-wire anemometry. At low Reynolds numbers and small inlet angles, a separation bubble is only slightly reduced due to surface roughness. The positive effect of a reduced separation bubble is overcompensated by a negative influence of surface roughness on the turbulent boundary layer downstream of the separation bubble. At high Reynolds numbers, the flow over the rough blade shows a turbulent separation leading to high total pressure loss coefficients. The laser-two-focus measurements indicate a velocity deficit close to the trailing edge, even at flow conditions where positive effects due to a reduction of the suction side separation have been expected. The turbulence intensity is reduced close downstream of the separation bubble but increased further downstream due to surface roughness. Thus the rear part of the blade but not the front part reacts sensitively on surface roughness.

41 citations

Journal ArticleDOI
TL;DR: In this paper, the optimum fabrication conditions for SiC-whisker-reinforced Si{sub 3}N{sub 4} composite ceramics were determined.
Abstract: Thermodynamic equilibria were calculated to determine optimum fabrication conditions for SiC-whisker-reinforced Si{sub 3}N{sub 4} composite ceramics. Results of calculations indicate that pressureless sintering in a nitrogen atmosphere of 0.1 MPa may be performed at temperatures up to 2,123 K (1,850{degree}C) without whisker or matrix degradation. In addition, gas pressure sintering at temperatures up to 2,373 K (2,100{degree}C) requires a nitrogen pressure of 1 to 10 MPa. Hot isostatic pressing (total pressure {ge} 100 MPa) at 2,273 K (2,000{degree}C) can yield undegraded composite materials only when the nitrogen partial pressure in a gas mixture with an inert gas is kept between 1 to 10 MPa.

40 citations

Journal ArticleDOI
TL;DR: The mass flux of RDE can be estimated using the maximum mass flux as mentioned in this paper of the injection Laval nozzle along the head end, which is not influenced by the total pressure, the mode of propagation, or the number of detonation waves.
Abstract: As the injection total pressure increases, the flow field in the combustion chamber of rotating detonation engine (RDE) becomes complicated and the detonation wave becomes unstable. When the total pressure is high enough, the detonation oscillates periodically and alternates between strong and weak. Under the same injection conditions, no oscillation is observed in two-wave RDE, and the two detonation waves propagate stably in the combustion chamber. The choking ratio of the injection Laval nozzle along the head end is not influenced by the total pressure, the mode of propagation, or the number of detonation waves. And thus the mass flux of RDE can be estimated using the maximum mass flux of the injection Laval nozzle. The specific impulse and thrust of RDE show overall growth as total pressure increases. However, they oscillate with the unstable detonation wave in one-wave RDE at high total pressure.

40 citations

Journal ArticleDOI
TL;DR: In this article, a dynamic model for the activity of Poas Volcano, Costa Rica, is proposed, which leads to the assumption that the kinetic and thermal energies are proportional to the depth at which the mechanical equilibrium is disturbed.
Abstract: A dynamic model for the activity of Poas Volcano, Costa Rica, is proposed. Data collected during a three-year period show that the volcanic processes occur within a small hydrothermal system. Heat is supplied by a magma body in the conduit and is transferred to the surface by fluid convection. Within a given volume of rock, pore pressure builds up due to the upward motion of fluids and the increase in vapor pressure when the temperature rises above the boiling point. Ultimately, the system becomes unstable when the pore pressure overcomes the total pressure. This leads to the assumption that the kinetic and thermal energies are proportional to the depth at which the mechanical equilibrium is disturbed. Laboratory experiments were performed by heating samples of the crater lake deposits. The preliminary results of these experiments show significant analogies with the low-energy activity of the volcano. Following this model we estimated that a phreatic explosion which reaches 200 m in height (comparable to the one observed by Francis et al. in 1978) originates at a depth of 70 m and a temperature of 180° C; these values agree with those reported in the literature. In addition, “magmatic” sulfur, which partitions into the rising hydrothermal fluids, reacts at lower temperature and higher $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{f} O_2$$ to produce pockets of liquid sulfur in the conduit deposits and the lava dome. These pockets are subsequently erupted forming the pyroclastic sulfur.

40 citations

Journal ArticleDOI
TL;DR: In this article, the heat transfer of R407C and the pressure drop of R410A during flow boiling in a horizontal microfin tube were investigated and a new method for deriving correlations was shown.

40 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202316
202225
2021127
2020147
2019153
2018128