| Ventilation channels in an afterburner chamber confluence sheet -> Monitor Keywords |
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Ventilation channels in an afterburner chamber confluence sheetRelated Patent Categories: Power Plants, Reaction Motor (e.g., Motive Fluid Generator And Reaction Nozzle, Etc.), Having AfterburnerVentilation channels in an afterburner chamber confluence sheet description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050274114, Ventilation channels in an afterburner chamber confluence sheet. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The invention relates to aviation turbomachines, in particular for military use, and that include afterburner chambers presenting an upstream diffuser. [0002] More precisely, the invention relates to an aviation bypass turbomachine having an afterburner chamber and including, upstream from said afterburner chamber: a diffuser defined by a confluence sheet placed inside a casing, said casing and said confluence sheet defining between them an annular channel for a cold secondary flow, upstream fuel injectors being disposed at the inlet to said diffuser, and flame-catchers being disposed downstream from said injectors, the confluence sheet presenting, in the radial plane containing said injectors and the radial plane containing the flame-catchers, two bends so as to flare downstream in order to slow down the primary flow downstream from said injectors. BACKGROUND OF THE INVENTION [0003] That type of turbomachine including a short diffuser between the injectors and the flame-catchers is characterized by a small bypass ratio seen from the rear body. The secondary flow serves in particular to cool the parts situated downstream from the injectors and must be used effectively for this purpose. [0004] Conversely, the primary flow coming from the low pressure turbine is flowing at a high rate. It is on this flow that the performance of the engine relies for the most part. Consequently, it must be subjected to a minimum amount of head losses and must be as uniform as possible in temperature and speed. For this purpose, the afterburner chamber diffuser constituted by the confluence sheet serves to slow down the primary flow upstream from the flame-catchers and to channel it so that, downstream, it occupies the entire volume of the afterburner chamber. This function, which is known as a "diffusion" function since it is accompanied by an increase in static pressure, needs to take place without unwanted turbulence forming along the stream, since such turbulence or backflow leads to losses that can cause the fuel coming from the upstream injectors to self-ignite. [0005] In afterburner chambers having a large dilution ratio, the primary flow and a portion of the secondary flow meet and mix. Conversely, when the dilution ratio is small, the fraction of the secondary flow available for mixing at the downstream end of the confluence sheet is small once all of the flows needed for ventilation have been taken off. The confluence sheet therefore needs to be flared so that the primary flow occupies the full extent of the afterburner chamber. If the sheet is not properly shaped, backflow occurs in the vicinity of the confluence sheet between the plane of the injectors and the plane of the flame-catchers. This backflow is particularly encouraged when the amount of gyration at the outlet form the low pressure turbine is large. [0006] A risk of backflow thus appears in the vicinity of a highly diffusing confluence sheet associated with a large amount of gyration in the primary flow. This backflow is predicted by numerical 3D simulation of the flow. It appears in the primary flow at the concave bend of the confluence sheet, where the sheet provides an indentation suitable for a pocket of backflow. [0007] Furthermore, at the junction between the convex bend portion and the concave bend portion of the confluence sheet temperature and temperature gradients are excessive. Steep temperature gradients are due to the convection of the cold secondary flow which blows against the outside surface of the sheet and the hot primary flow which blows against its inside surface. [0008] In order to eliminate turbulence, it would naturally be possible to modify the shape of the confluence sheet by lengthening the diffuser axially, but that solution increases the size of the engine. OBJECTS AND SUMMARY OF THE INVENTION [0009] An object of the invention is to decrease the risk of backflow and the temperature gradients without changing the shape and the length of the diffuser. [0010] According to the invention, this object is achieved by the fact that an annular scoop is provided around the upstream portion of said confluence sheet in order to extract a flow of air from the cold flow, this extracted flow of air being injected tangentially into the primary flow via a plurality of channels formed in the wall of the confluence sheet between the scoop and said diffuser. [0011] These channels serve firstly to cool the confluence sheet by convection, and secondly to create a film of cooling air along the confluence sheet where it is subjected to radiation from the flame in the afterburner chamber. This reduces the temperature of the structure, and also leads to a reduction in the infrared signature of the solid portions at the end of the chamber. The axial flow of cooling air along the wall of the confluence sheet also makes it possible to expel the flow disturbance from this zone. [0012] Preferably, the channels that open out circumferentially in the wake of the injectors are of a section that is significantly greater than that of the other channels. [0013] The greater flow of air coming from these wider channels serves to blow away the backflow. [0014] Advantageously, the scoop is defined on the inside by a shell surrounding the upstream section of the diffuser, and on the outside by the upstream portion of a sheet which, downstream of the shell, forms the middle zone and the downstream zone of the confluence sheet that are cooled by the flow of air injected via the channels. BRIEF DESCRIPTION OF THE DRAWINGS [0015] Other advantages and characteristics of the invention will appear on reading the following description made by way of example and with reference to the accompanying drawings, in which: [0016] FIG. 1 is a half-section on a plane containing the axis of symmetry of the upstream portion of the rear body of an aviation turbomachine of the invention fitted with a diffuser upstream from a post-combustion chamber; and [0017] FIG. 2 is a perspective view of the inside shell defining the upstream section of the diffuser. MORE DETAILED DESCRIPTION [0018] In FIG. 1, reference 1 designates the upstream portion of the rear body of an aviation turbomachine of axis X, presenting a diffuser 2 downstream from the low pressure turbine and upstream from an afterburner chamber. [0019] The diffuser 2 is defined by a confluence sheet 3 situated radially inside a casing 4, the casing 4 and the confluence sheet 3 defining between them an annular channel 5 in which there flows a cold secondary flow F2. Continue reading about Ventilation channels in an afterburner chamber confluence sheet... Full patent description for Ventilation channels in an afterburner chamber confluence sheet Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Ventilation channels in an afterburner chamber confluence sheet patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Ventilation channels in an afterburner chamber confluence sheet or other areas of interest. ### Previous Patent Application: Steam temperature control system, method of controlling steam temperature and power plant using the same Next Patent Application: Method and apparatus for prevention of compressor stall and combustion flameout in a turbine engine Industry Class: Power plants ### FreshPatents.com Support Thank you for viewing the Ventilation channels in an afterburner chamber confluence sheet patent info. IP-related news and info Results in 0.16321 seconds Other interesting Feshpatents.com categories: Qualcomm , Schering-Plough , Schlumberger , Seagate , Siemens , Texas Instruments , 174 |
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