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US4098073A Expired / Lapsed US ⏱️ 0.0 years remaining

Fluid flow diffuser

Assignee: Rolls Royce PLC
•
Filing: 1977-03-21
•
Granted: 1978-07-04
•
Expires: 1997-03-21
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Abstract

Abstract Fluid flow diffuser has a first divergent duct connected by a sudden enlargement of flow area to a second divergent duct. The enlargement is defined by a fence situated downstream of the downstream end of the first duct. The top of the fence is on a flow perimeter intermediate between the downstream end of the first duct and the upstream end of the second duct, the latter end being defined by the bottom of the fence. An opening defined by the downstream end of the first duct and by the top of the fence gives access to a chamber connected to a pressure less than that at latter downstream end thereby to generate a vortex having a surface bridging the opening and assisting transition of flow from the first duct to the top of the fence. A second vortex formed immediately downstream of the fence assists transition of flow from the top of the fence to the surface of the second duct. The first duct has a rate of divergence low enough to avoid boundary separation. The second duct has a rate of divergence greater than at boundary layer separation would normally occur. The arrangement described avoids boundary layer separation in the second duct and leads overall to a relative reduction in the length of the diffuser for a given rate of diffusion or a relative increase in the rate of diffusion for a given diffuser length.

Inventors

  • 👤 Richard Cyril Adkins
  • 👤 James Oswald Yost

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-31 00:20
CPC Classifications
F; F23; F23R; F23R3/00; F23R3/02; F01; F01D; F01D25/00; F01D25/30; F04; F04D; F04D29/00; F04D29/66; F04D29/68; F04D29/681; F04D29/682; Y; Y10; Y10S; Y10S415/00; Y10S415/914

Claims Analysis

Total Claims: 5
Claim 1
Independent Claim 214 words
Fluid flow diffuser comprising a first and a second divergent duct connected in flow series, the first duct being divergent at a rate less than that at which boundary layer separation occurs, the upstream end of the second duct having a flow perimeter substantially larger than the flow perimeter of the downstream end of the first duct thereby to define a sudden enlargement of flow area between the ducts wherein the sudden enlargement is defined by a fence situated downstream of the downstream end of the first duct, the bottom of the fence defines the upstream end of the second duct, the top of the fence is situated at a flow perimeter intermediate between those of the adjacent ends of the two ducts, a chamber is provided at the outside of the first duct at the downstream end thereof, an opening having access to said chamber is defined between the downstream end of the first duct and the top of the fence, means are provided for reducing the static pressure in the chamber to below that at the end of the first duct thereby to facilitate the formation of a vortex in the chamber, and the second duct has a rate of divergence greater than that at which boundary layer separation would normally occur.
Claim 2
Dependent Claim 214 words
Fluid flow diffuser comprising a first and a second divergent duct connected in flow series, the first duct being divergent at a rate less than that at which boundary layer separation occurs, the upstream end of the second duct having a flow perimeter substantially larger than the flow perimeter of the downstream end of the first duct thereby to define a sudden enlargement of flow area between the ducts wherein the sudden enlargement is defined by a fence situated downstream of the downstream end of the first duct, the bottom of the fence defines the upstream end of the second duct, the top of the fence is situated at a flow perimeter intermediate between those of the adjacent ends of the two ducts, a chamber is provided at the outside of the first duct at the downstream end thereof, an opening having access to said chamber is defined between the downstream end of the first duct and the top of the fence, means are provided for reducing the static pressure in the chamber to below that at the end of the first duct thereby to facilitate the formation of a vortex in the chamber, and the second duct has a rate of divergence greater than that at which boundary layer separation would normally occur.
Claim 3
Dependent Claim 44 words
Diffuser according to claim 1 wherein the chamber is connected to a location in the first duct at a point where the static pressure in the first duct is sufficiently low for the purpose of facilitating said formation of a vortex in the chamber.
Claim 4
Dependent Claim 37 words
Diffuser according to claim 1 in combination with a gas generator having a free power turbine having an exhaust duct comprising said first duct of the diffuser and said diffuser constituting an exhaust system for the turbine.
Claim 5
Dependent Claim 51 words
Diffuser according to claim 1 in combination with a gas turbine engine having an axial flow compressor having an annular delivery duct comprising said first duct of the diffuser, and wherein the second duct of the diffuser has an outlet into an air casing surrounding a combustion chamber of the engine.

References Cited (Backward Citations)

GB580841A Cited
US2841182A Cited
US3000401A Cited
US3216455A Cited
DE1264360B Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1981-07-03 1982-01-02 1982-07-04 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1985-07-03 1986-01-02 1986-07-04 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1989-07-03 1990-01-02 1990-07-04 $7700.00 Window Closed / Lapsed

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