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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.


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Proceedings ArticleDOI
26 Sep 2005
TL;DR: In this paper, a two-dimensional, mixed compression, two-ramp supersonic inlet was designed to maximize total pressure recovery and match the mass flow demand of the engine.
Abstract: *† This paper provides a method of preliminary design for a two-dimensional, mixed compression, two-ramp supersonic inlet to maximize total pressure recovery and match the mass flow demand of the engine. For an on-design condition, the total pressure recovery is maximized according to the optimization criterion, and the dimensions of the inlet in terms of ratios to the engine face diameter are calculated. The optimization criterion is defined such that in a system of (n-1) oblique shocks and one normal shock in two dimensions, the maximum shock pressure recovery is obtained when the shocks are of equal strength. This paper also provides a method to estimate the total pressure recovery for an off-design condition for the specified inlet configuration. For an off-design condition, conservative estimation of the total pressure recovery is given so that performance of the engine at the off-design condition can be estimated. To match the mass flow demand of the engine, the second ramp angle is adjusted and the open/close schedule of a bypass door is determined. The effects of boundary layer are not considered for the supersonic part of the inlet, however friction and expansion losses are considered for the subsonic diffuser. Nomenclature α = Angle of attack j β = The installation angle of the j th ramp γ = The ratio of specific heats j δ = The flow deflection angle of the j th shock (j th ramp half angle) d θ = The half expansion angle of the subsonic diffuser j θ = The shock wave angle of the j th shock * A = The cross section area of flow tube at throat where the flow is sonic j A = The cross section area of flow at j th station point 54 AR = The ratio of inlet cross section areas at station points 5 and 4 5 d = The engine diameter at station point 5 (engine face) 6 d = The engine diameter at station point 6 (fan face) H = Flight altitude c h , 0 h = The captured freestream flow tube height i h = The height of inlet at the entry, measured perpendicular to the flight direction j h = The height of j

51 citations

Patent
Hisanori Toyoshima1, Fumio Jyoraku1, Yoshitaro Ishii1, Yukiji Iwase1, Sato Shigenori1 
23 Feb 1990
TL;DR: In this article, an electric blower has an electric motor, a centrifugal impeller rotating by the driving of the electric motor and a diffuser, and an end bracket for separating the motor from the impeller, and a sound absorbing material is arranged in the discharge air flow return passage to absorb sounds from discharging air flow.
Abstract: An electric blower has an electric motor, a centrifugal impeller rotating by the driving of the electric motor, an end bracket for separating the electric motor from the centrifugal impeller, and a diffuser. The diffuser includes a plurality of diffuser vanes arranged near the outer periphery of the centrifugal impeller, and a flat plate portion which extends between the centrifugal impeller and the end bracket for supporting the diffuser vanes. The flat plate portion has a plurality of guide vanes formed on an opposite surface thereof from the diffuser vanes. A passage is defined by the end bracket, the flat plate portion and the guide vanes so as to return the air flow, discharged from the centrifugal impeller through the diffuser vanes, inwardly of the blower. The end bracket is formed in a substantially convex shape so as to extend away from the flat plate portion of the diffuser, with the end bracket extending from a central portion toward its periphery, thereby defining an opening area of the discharge air flow return passage. A sound absorbing material is arranged in the discharge air flow return passage to absorb sounds from the discharging air flow.

51 citations

Journal ArticleDOI
TL;DR: This study examines the influence of the diffuser on the overall LEV-VAD performance and concludes that the acceptable results of the computational simulations and experimental testing encourage final prototype manufacturing for acute and chronic animal studies.
Abstract: Thousands of adult cardiac failure patients may benefit from the availability of an effective, long-term ventricular assist device (VAD). We have developed a fully implantable, axial flow VAD (LEV-VAD) with a magnetically levitated impeller as a viable option for these patients. This pump's streamlined and unobstructed blood flow path provides its unique design and facilitates continuous washing of all surfaces contacting blood. One internal fluid contacting region, the diffuser, is extremely important to the pump's ability to produce adequate pressure but is challenging to manufacture, depending on the complex blade geometries. This study examines the influence of the diffuser on the overall LEV-VAD performance. A combination of theoretical analyses, computational fluid (CFD) simulations, and experimental testing was performed for three different diffuser models: six-bladed, three-bladed, and no-blade configuration. The diffuser configurations were computationally and experimentally investigated for flow rates of 2-10 L/min at rotational speeds of 5000-8000 rpm. For these operating conditions, CFD simulations predicted the LEV-VAD to deliver physiologic pressures with hydraulic efficiencies of 15-32%. These numerical performance results generally agreed within 10% of the experimental measurements over the entire range of rotational speeds tested. Maximum scalar stress levels were estimated to be 450 Pa for 6 L/min at 8000 rpm along the blade tip surface of the impeller. Streakline analysis demonstrated maximum fluid residence times of 200 ms with a majority of particles exiting the pump in 80 ms. Axial fluid forces remained well within counter force generation capabilities of the magnetic suspension design. The no-bladed configuration generated an unacceptable hydraulic performance. The six-diffuser-blade model produced a flow rate of 6 L/min against 100 mm Hg for 6000 rpm rotational speed, while the three-diffuser-blade model produced the same flow rate and pressure rise for a rotational speed of 6500 rpm. The three-bladed diffuser configuration was selected over the six-bladed, requiring only an incremental adjustment in revolution per minute to compensate for and ease manufacturing constraints. The acceptable results of the computational simulations and experimental testing encourage final prototype manufacturing for acute and chronic animal studies.

51 citations

Journal ArticleDOI
TL;DR: In this article, the authors present microfabrication and characterization of truly 3D diffuser/nozzle structures in silicon using chemical vapor deposition (CVD), reactive ion etching (RIE), and laser-assisted etching.
Abstract: We present microfabrication and characterization of truly three-dimensional (3-D) diffuser/nozzle structures in silicon. Chemical vapor deposition (CVD), reactive ion etching (RIE), and laser-assisted etching are used to etch flow chambers and diffuser/nozzle elements. The flow behavior of the fabricated elements and the dependence of diffuser/nozzle efficiency on structure geometry has been investigated. The large freedom of 3-D micromachining combined with rapid prototyping allows one to characterize and optimize diffuser/nozzle structures.

50 citations


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