scispace - formally typeset
Search or ask a question
Topic

Diffuser (thermodynamics)

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


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, a design procedure based on a one-dimensional simulation is presented for an ejection refrigeration system, where heat exchangers are included in the calculation, accounting for temperature differences between the fluids and for pressure losses.

35 citations

Journal ArticleDOI
TL;DR: In this paper, a numerical investigation is presented to characterize the transient behaviors of microdiffuser pumps, and the authors provide design guidelines to make more efficient use of micro diffuser pumps in various microscopic applications.
Abstract: In this study, a numerical investigation is presented to characterize the transient behaviors of microdiffuser pumps. The motivation of the present work is to clarify the scaling and dynamic effects on the flow rectification of microdiffuser pumps. Two primary parameters, half angle (θ = 5° to 55°) and excitation frequency (f = 1 Hz to 1000 Hz), are considered. A time-dependent sinusoidal pressure with fixed pressure amplitude is applied at the inlet as the boundary condition. Different from previous investigations and despite the corresponding low Reynolds numbers, circulation is observed for all tested half angles and excitation frequencies. The persistence of the backflow helps to augment flow rectification since the vortical structures block a portion of the diffuser and prevent the through flow from decelerating. Contrary to past claims, diffusers with larger half angles show better rectification effects for 5° ≤ θ ≤ 35°. For θ > 35°, the net flow rate is nearly independent of the half angle. The computational results also yield that the net flow rate is independent of excitation frequency for f 25 Hz. Hence, the role of excitation frequency is classified into three different regimes by the Roshko number: frequency independent regime (Ro 2). An essential contribution of this study is that it provides design guidelines for microdiffuser pumps, further expanding the knowledge of flow rectification properties to make more efficient use of microdiffuser pumps in various microscopic applications.

35 citations

Proceedings ArticleDOI
01 Jan 2008
TL;DR: In this paper, the effect of cross-flow on diffuser hole performance was investigated and the dominating mechanisms that determine the flow field within the diffuser holes were identified. But the authors did not consider the effects of flow in the coolant passage.
Abstract: Cooling holes in real gas turbine applications are prevalently exposed to cross-flow in the coolant passage. The majority of the studies available in literature do not consider the effects of flow in the coolant passage. Our own studies however reveal that especially diffuser holes are very susceptible in respect to cross-flow at the hole entrance, if the orientation of the cross-flow is perpendicular to the symmetry plane of the cooling hole. The effect of coolant cross-flow will be discussed in detail. The superordinate target is to identify the dominating mechanisms, which determine the flow field within the diffuser hole and hence limit the potential of cooling performance augmentation. For this reason a fan-shaped hole with 14° expansion angle will be compared to a simple cylindrical hole. Both holes have a length-to-diameter ratio of 6 and an inclination angle of 30°. The comparison will be performed by means of experimentally gained discharge coefficients, local and laterally averaged adiabatic film cooling effectiveness, and heat transfer coefficients. Numerical simulations of the cooling flow will support the interpretation of the experimental results.Copyright © 2008 by ASME

35 citations

Patent
23 Jul 1969
TL;DR: In this article, the authors describe a Turbomachine with two coaxially-arranged ROTATABLE GUIDE VANES through which the fluid flows in succ succession.
Abstract: A CENTRIFUGAL FLUID-FLOW TURBOMACHINE HAS DIFFUSER PROVIDED WITH TWO COAXIALLY ARRANGED ROWS OF ROTATABLE GUIDE VANES THROUGH WHICH THE FLUID FLOWS IN SUCCESSION. THE PIVOT AXES OF THE VANES OF SAID TWO ROWS ARE DISPLACEABLE IN RELATION TO ONE ANOTHER IN THE CIRCUMFERENTIAL DIRECTION OF THE ROWS.

35 citations

Journal ArticleDOI
TL;DR: In this article, an internal layer was found in the turbulent flow through an asymmetric planar diffuser using large-eddy simulation; they discuss five issues relevant to the internal layer: definition and identification, conditions for occurrence, connection with its outer flow, similarity with other equilibrium flows, and growth.
Abstract: We report an internal layer found in the turbulent flow through an asymmetric planar diffuser using large-eddy simulation; we discuss five issues relevant to the internal layer: definition and identification, conditions for occurrence, connection with its outer flow, similarity with other equilibrium flows, and growth. The present internal layer exists in a region with stabilized positive skin friction downstream of a sharp reduction. The streamwise pressure gradient changes suddenly from slightly favourable to strongly adverse at the diffuser throat, and relaxes in a prolonged mildly adverse region corresponding to the skin friction plateau. Development of the internal layer into the outer region is slow, in contrast to the internal layers previously identified from certain external boundary-layer flows where the sudden change in streamwise pressure gradient is from strongly adverse to mildly favourable. Signatures of the internal layer include an inflectional point in the wall-normal profiles of streamwise turbulence intensity, and a well-defined logarithmic slope in the mean streamwise velocity underneath a linear distribution extending to the core region of the diffuser. Some of these characteristics bear a certain resemblance to those existing in the C-type of Couette–Poiseuille turbulent flows. Frequency spectrum results indicate that application of strong adverse pressure gradient at the diffuser throat enhances the low-frequency content of streamwise turbulent fluctuations. Inside the internal layer, the frequency energy spectra at different streamwise locations, but with the same wall-normal coordinate, nearly collapse. Two-point correlations with streamwise, wall-normal and temporal separations were used to examine connections between fluctuations inside the internal layer and those in the core region of the diffuser where the mean streamwise velocity varies linearly with distance from the wall. Galilean decomposition of instantaneous velocity vectors reveals a string of well-defined spanwise vortices outside the internal layer. The internal layer discovered from this study provides qualified support for a conjecture advanced by Azad &

35 citations


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