US-20260126174-A1 - NOZZLE FOR FEEDING AIR AND LIQUID FUEL INTO A COMBUSTION CHAMBER, AND ENGINE

US20260126174A1US 20260126174 A1US20260126174 A1US 20260126174A1US-20260126174-A1

Abstract

A nozzle for feeding air and liquid fuel into a combustion chamber, has a nozzle main body aligned along an axis, and includes a first air duct running on and/or around the axis, a fuel duct, annularly encircling the first air duct and having a downstream end portion running axially-radially in a direction of the axis in a flow direction, and a second air duct, annularly encircling the fuel duct. The fuel duct has a fuel outlet opening at an adjoining substantially axially aligned film applicator surface having a downstream trailing edge, wherein the film applicator surface surrounds the first air duct at the downstream end. Fuel atomization is improved by a length of the film applicator surface between the fuel outlet opening and the trailing edge being between a factor of 5-6 times a height of the end portion of the fuel duct.

Inventors

Gregor Christoffer Gebel
Carsten Clemen
Thomas Dörr

Assignees

ROLLS-ROYCE DEUTSCHLAND LTD & CO KG

Dates

Publication Date: 20260507
Application Date: 20251024
Priority Date: 20241105

Claims (10)

1 . A nozzle for feeding air and liquid fuel into a combustion chamber, in particular of an engine of an aircraft, having a nozzle main body aligned along a nozzle longitudinal axis, in which the following are arranged: at least one first air duct running on and/or around the nozzle longitudinal axis, at least one fuel duct, which is arranged radially on the outside, in particular in an annularly encircling manner, around the first air duct and has a downstream end portion running axially-radially in the direction of the nozzle longitudinal axis in the direction of flow, and at least one second air duct, which is arranged radially on the outside, in particular in an annularly encircling manner, around the fuel duct, wherein the fuel duct emerges by means of a fuel outlet opening at an adjoining, at least substantially axially aligned film applicator surface having a downstream trailing edge, wherein the film applicator surface surrounds the first air duct at the downstream end, wherein a length of the film applicator surface between the fuel outlet opening and the trailing edge is between a factor of 5 and 6, preferably a factor of 5.5, times a height of the end portion of the fuel duct.
2 . The nozzle according to claim 1 , wherein the film applicator surface is inclined axially-radially at an angle of between 5° and 15° to the nozzle longitudinal axis in such a way that it runs in the direction of the nozzle longitudinal axis in the direction of flow.
3 . The nozzle according to claim 1 , wherein the downstream end portion is inclined axially-radially at an angle of between 25° and 35° to the nozzle longitudinal axis in such a way that it runs in the direction of the nozzle longitudinal axis in the direction of flow.
4 . The nozzle according to claim 1 , wherein the outlet area of the fuel outlet opening is aligned orthogonally to the nozzle longitudinal axis, or orthogonally to a central longitudinal plane of the end portion, or between these two alignments.
5 . The nozzle according to claim 1 , wherein a flank extending radially between an inner radius and an outer radius, aligned at least substantially orthogonally to the nozzle longitudinal axis, and upstream of the film applicator surface is arranged between the first air duct and the fuel duct, axially at the position of the fuel outlet opening, between the first air duct and the fuel outlet opening, said flank having a height of between 0.15 mm and 0.25 mm.
6 . The nozzle according to claim 5 , wherein the trailing edge is positioned radially between the inner radius and the outer radius.
7 . The nozzle according to claim 1 , wherein a flank aligned at least substantially orthogonally to the nozzle longitudinal axis and downstream of the film applicator surface is arranged axially at the position of the trailing edge, said flank having a height of up to 0.2 mm, e.g. between 0.1 mm and 0.2 mm.
8 . The nozzle according to claim 1 , wherein two air ducts, within each of which a swirl generator is preferably arranged, are arranged radially on the outside, in particular in an annularly encircling manner, around the fuel duct, said air ducts being offset radially relative to one another, e.g. being arranged coaxially with one another, at least in some section or sections.
9 . The nozzle according to claim 8 , wherein the two air ducts each have a downstream end portion for entry into the combustion chamber which is aligned axially-radially in the direction of the nozzle longitudinal axis.
10 . An engine having at least one nozzle according to claim 1 .

Description

This application claims priority to German Patent Application 102024132232.2 filed Nov. 5, 2024, the entirety of which is incorporated by reference herein. The invention relates to a nozzle for feeding air and liquid fuel into a combustion chamber, in particular of an engine of an aircraft, according to the preamble of Claim 1, and to an engine. A nozzle of this kind, which, according to its principle of operation, belongs to the category of air-jet atomizer nozzles, is specified in DE 10 2017 218 529 A1. In this case, an annular fuel duct is arranged around a central air duct, and two radially offset annular air guide ducts are in turn arranged around the annular fuel duct. When the fuel emerges onto the film applicator surface, the fuel film is transported in the direction of the trailing edge by the passing air from the central air duct and, after flowing out between the central air flow and one of the outer air flows, is atomized into fine droplets. Another nozzle of this kind is known from U.S. Pat. No. 9,423,137B2. In the case of this known nozzle for adding liquid fuel to a combustion chamber, there is a plurality of radially offset fuel ducts, via which fuel is added to different air ducts. Other nozzles for feeding air and liquid fuel into a combustion chamber are known from US 2014/0241871 A1, US 2020/0141582 A1, US 2022/0099290 A1, US 2016/0047315 A1 and US 2010/0229556A1 . Tests by means of high resolution flow simulations have shown that the process by which the fuel flows off the film applicator surface is in part subject to periodic fluctuations. These fluctuations consist, on the one hand, in the build-up and collapse of fuel waves due to the interaction with the air flowing over at the fuel outlet opening. In this way, large liquid filaments of flow can form as the fuel leaves the trailing edge, and, further downstream, these break down into relatively large droplets. On the other hand, fluctuations occur due to occupation of the film applicator surface by waves of fuel emerging from the fuel outlet opening. Owing to the fluctuations in the fuel mass flow and the resulting droplet size distribution, pressure fluctuations/thermoacoustics associated with the flame dynamics may occur, and there may be a negative effect on the formation of pollutants within the combustion chamber. It is the underlying object of the invention to provide a nozzle for stable operation of a combustion chamber with low levels of pollutants, as well as an engine that can be operated in a stable manner with low levels of pollutants. For the nozzle, the invention is achieved by the features of Claim 1, and for the engine by the features of Claim 10. In the case of the nozzle, it is envisaged that a length of the film applicator surface between the fuel outlet opening and the trailing edge is a factor of 5 to 6, preferably a factor of 5.5, times a height of the end portion of the fuel duct. The fuel duct is preferably of annularly encircling design, at least within the end portion. In the present context, height refers to the (possibly maximum) distance between a radially inner wall surface and a radially outer wall surface of the end portion, obtained orthogonally to a central longitudinal plane extending centrally between these two walls. The height within the end portion is preferably at least substantially constant in the direction of flow (e.g. apart from transitional portions, such as after the transition of the fuel duct from the axial portion to the end portion). In particular, the nozzle is of at least substantially rotationally symmetrical design, wherein the length of the film applicator surface is preferably constant, forming an annular surface encircling the nozzle longitudinal axis. The film applicator surface is arranged adjacent to the first air duct to enable an air flow flowing through the first air duct to flow over it, preferably in its entirety. The relatively long film applicator surface allows increased transfer of momentum from the air flow within the first air duct to the fuel film as compared with the prior art. The fuel film is subject to greater acceleration and reaches the trailing edge at a higher flow velocity (relative to the nozzle body). When it reaches the trailing edge, the fuel film has a smaller radial thickness. This contributes to the formation of the relatively small fuel ligaments when the fuel separates from the trailing edge, thereby reducing or preventing accumulation of fuel from the overall mass flow at a single outlet opening. Wave formation or fluctuations in the fuel mass flow are significantly reduced, this being associated with more uniform combustion with significantly increased stability and reduced pollutant emissions, especially reduced soot formation. Another positive effect on fuel atomization is achieved if the film applicator surface is inclined axially-radially at an angle (in particular a constant angle) of between 5° and 15° to the nozzle longitudinal axis i