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Diffuser (thermodynamics)

About: Diffuser (thermodynamics) is a research topic. Over the lifetime, 6731 publications have been published within this topic receiving 54738 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a valveless micropump excited by a piezoelectric actuator for medical applications was designed and analyzed using ANSYS software to investigate the effects of the geometrical dimensions on the micropumps characteristics and its efficiency.
Abstract: We designed a valveless micropump excited by a piezoelectric actuator for medical applications. The complete electric–fluid–solid coupling model is built upon using ANSYS software (Canonsburg, PA) to investigate the behaviors of the micropump. The effects of the geometrical dimensions on the micropump characteristics and its efficiency are analyzed. The simulation results show that there is an optimal thickness of the piezoelectric layer to obtain a large pump flow, and that this optimal thickness is affected by the material and the thickness of the pump membrane. To enhance the performance of the micropump, some important diffuser parameters, such as the diffuser length, the diffuser angle, and the neck width, should be optimized. However, the variations of the diffuser’s geometrical dimensions do not affect the optimal thickness of the piezoelectric layer.

60 citations

Patent
29 Jun 1993
TL;DR: In this article, an axial flow turbomachine is provided having a diffuser that directs the flow of working fluid from a turbine exit to an exhaust housing having a bottom opening, thereby turning the flow 90° from the axial to radial direction.
Abstract: An exhaust system for an axial flow turbomachine is provided having a diffuser that directs the flow of working fluid from a turbine exit to an exhaust housing having a bottom opening, thereby turning the flow 90° from the axial to radial direction In the exhaust housing, the flow exiting at the top of the diffuser turns 180° from the vertically upward direction to the downward direction The strength of the vortex formed in the exhaust housing as a result of this turning is minimized by orienting the outlet of an outer exhaust flow guide portion of the diffuser so that it lies in a plane that makes an angle with a plane perpendicular to the turbine axis As a result, the minimum axial length of the outer flow guide occurs at a location remote from the exhaust housing outlet and the maximum axial length occurs at a location proximate the opening, thereby crowding the vortex against a radially extending baffle in the exhaust housing

60 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present an analysis of the performance of micronozzle/diffusers and report on the fabrication and testing of a micronoezzel/diffuser.
Abstract: In this paper, we present an analysis of the performance of micronozzle/diffusers and we report on the fabrication and testing of a micronozzle/diffuser. We have found that the pressure loss coefficient for the nozzle/diffuser decreases with the Reynolds number. At a given Reynolds number, the pressure loss coefficient for the nozzle is higher than that of the diffuser due to a considerable difference in the momentum change. We find that the nozzle/diffuser length has little influence on the pressure loss coefficient. At a fixed volumetric flow rate, we encounter a 'minimum' phenomenon of the pressure loss coefficient versus nozzle/diffuser depth. This is related to the interactions of velocity change and friction factor. In this work, we find good agreement between the measured data and the predicted results, except for a diffuser having an opening angle of 20°. This is because of the presence of flow separation. The departure of this case from the prediction is due to the separation phenomenon in a diffuser with a larger angle.

60 citations

Journal ArticleDOI
TL;DR: In this paper, the Kolmogorov velocity scale was introduced to account for the nearwall and low-Reynolds-number effects of turbulent energy and its dissipation rate.
Abstract: We propose a new turbulence model which is modified from the low-Reynolds-number k-e model developed by Nagano and Tagawa. The main improvement is made by the introduction of the Kolmogorov velocity scale, ue≡(νe)1/4, instead of the friction velocity uτ, to account for the nearwall and low-Reynolds-number effects. We have also reevaluated the model constants in the transport equations of the turbulent energy and its dissipation rate. With these modifications, it is shown that the present model predicts quite successfully a diffuser flow with a strong adverse pressure gradient and the separating and reattaching flows downstream of a backward-facing step.

60 citations

Patent
Bradley W. Smith1
14 Dec 1992
TL;DR: In this article, a gas generator includes a chamber in which inert gas under high pressure is stored, a diffuser chamber, and a chamber containing a pyrotechnic heater and initiator.
Abstract: A gas generator includes a chamber in which inert gas under high pressure is stored, a diffuser chamber, and a chamber containing a pyrotechnic heater and initiator. Upon receiving an electrical signal the initiator fires igniting the pyrotechnic charge. As pressure in the combustion chamber of the pyrotechnic heater rises and exceeds the storage chamber pressure, a plug in a shoulder covering the pyrotechnic nozzle orifice is unseated, subsequently rupturing a thin metal sealing diaphragm since the latter is unsupported for a pressure differential in this direction. Hot gas and particles from the burning pyrotechnic heat the stored gas causing a rapid pressure rise in the storage chamber. When the storage chamber pressure exceeds the structural capability of a thin metal disc between the diffuser and storage chambers, it ruptures allowing the heated gas to vent through the diffuser orifices into the air bag assembly.

59 citations


Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20224
2021156
2020186
2019216
2018236
2017263