DE102013018146B4 - Injection element for a rocket combustion chamber - Google Patents

Abstract

Injection element for a rocket combustion chamber, which has an at least largely rotationally symmetrical central body (2) with a first, inner swirl element (3) with a first, inner outlet opening (4) and with a second, outer swirl element (5) with an outlet opening (4 ) comprises coaxial, second, outer outlet opening (6) for receiving and injecting a respective fuel component into a combustion chamber, the first, inner swirl element (3) and the second, outer swirl element (5) each being designed to supply a fuel component with a swirl acted upon, the fuel components discharged from the first and second outlet openings (4, 6) mixing in the combustion chamber, characterized in that an outlet edge circumference (7) of the outer outlet opening (6) has a contour which, compared to a circular basic shape of the outer Outlet opening is enlarged.

Description

The invention relates to an injection element for a rocket combustion chamber, which has an at least largely rotationally symmetrical central body with a first, inner swirl element with a first, inner outlet opening and with a second, outer swirl element with a second, outer outlet opening coaxial with the first outlet opening for receiving and injecting a comprises respective fuel component in a combustion chamber, so that the fuel components discharged from the first and second outlet openings mix thoroughly in the combustion chamber.

Injection elements are used to introduce propellants into the rocket combustion chamber and prepare the mixture. There are different types of injection elements. In rocket engines, either single or dual fuel injectors are used. In the case of the latter, which are used to supply two fuel components for reaction in the rocket combustion chamber, a coaxial design is generally used. Swirl elements are preferably used, especially when using storable fuels. The structure and mode of operation of different types of injection elements are known from the prior art.

For example, the EP 2 172 636 A2 an injection element for a rocket combustion chamber with a largely rotationally symmetrical central body with a first, inner swirl element with a first, inner outlet opening and with a second, outer swirl element with a second, outer outlet opening coaxial with the first outlet opening for receiving and injecting a respective fuel component into a combustion chamber includes. The design of the outlet openings is not described in more detail.

The EP 1 689 996 B1 discloses an injection element for a rocket combustion chamber which comprises two coaxially arranged outlet openings, with third outlet openings being provided in the form of bores for forming a cooling liquid film layer, which are also arranged coaxially with the first and second outlet openings. The bores end in an annular gap in the outer element and are inclined in two planes in order to inject the fuel with a swirl into the combustion chamber.

The US 6 502 385 B2 discloses a tri-coaxial injector wherein a flow of fuel is split and injected into the combustion chamber via two coaxial outlet openings.

In the case of the injection element of US 2012/0261497 A1, spiral-shaped outlet openings are provided in order to inject two fuel components with a swirl into the rocket combustion chamber.

Particularly in the area of engines that use storable fuels, the increased ignition delay times make it necessary to introduce additional measures for more intensive mixing of the fuels. For this purpose, primarily coaxial elements with at least one twist are used.

Swirl elements lead to the formation of a hollow liquid cone, which enables accelerated droplet formation at the element outlet. When using double swirl elements (i.e. both fuel components are injected into the rocket combustion chamber with a swirl), there are certain geometric restrictions when using storable fuels, which do not allow the hollow cones that are formed to interact at an optimal interaction angle. However, this has a decisive influence on the mixture preparation and thus the overall behavior of the system.

In order to enable the angles to interact in the desired manner, injection elements with an undercut (so-called recess) are used. In such injection elements, the outlet opening or edge of the inner swirl element is retracted downstream with respect to the outlet opening or edge of the outer swirl element in order to enable a geometric overlap of the hollow cones generated by the two swirl elements. This can lead to the formation of an intermediate layer consisting of hot gas (partial reaction of the fuels in the contact area) between the cones, which prevents further rapid reaction of the fuel components and thus also influences the degree of burnout and the low-frequency behavior.

From the DE 101 30 355 A1 an injection element is known which splits a fuel flow fed to a combustion chamber and injects the two partial flows separately into the combustion chamber. For this purpose, a torque is impressed on the fuel flow supplied in the injection element with a swirler and the swirled fuel flow is split into a primary hollow cone flow and a secondary hollow cone flow and into the combustion chamber with different injection angles by means of a flow divider, a primary outlet channel and a secondary outlet channel injected. The outlet edges of the primary outlet channel and the secondary outlet channel are circular.

From the US 7 137 254 B1 is known in coaxial injectors, in which at least the contour of the outlet edge circumference of an inner outlet opening has bulges.

The EP 0 619 456 A1 discloses a multiple vortex generator fuel delivery system for a combustor in which the vortex generators are of different heights.

RU 2 497 011 C1 discloses a jet nozzle with a hollow tip having an axial channel. At its outlet end, the tip has protrusions and depressions which are arranged alternately. A socket is also provided. There is a gap between the socket and the outlet end of the tip. Hydrogen is introduced into a combustion zone through the gap between the tip and the liner. The shape or cross section of the tip is intended to change the cross section of the jet. The cross-section of the beam should be changed from a round cross-section to a cross-section in the form of a "four-pointed star" through the tip.

It is therefore the object of the present invention to specify an injection element for a rocket combustion chamber of a rocket engine in which sufficient interaction of the fuel pairing takes place without the formation of the separating hot gas intermediate layer. In particular, storable propellants should be able to be used in the rocket engine.

This object is achieved by an injection element according to the features of claim 1. Advantageous refinements result from the dependent claims.

The invention creates an injection element for a rocket combustion chamber, which has an at least largely rotationally symmetrical central body with a first, inner swirl element with a first, inner outlet opening and with a second, outer swirl element with a second, outer outlet opening coaxial to the first outlet opening for receiving and injecting a each fuel component in a combustion chamber, wherein the first, inner swirl element and the second, outer swirl element are each designed to act on a fuel component with a swirl, so that the fuel components discharged from the first and second outlet openings mix in the combustion chamber. The injection element is characterized in that the outlet edge circumference of the outer outlet opening has a contour which is enlarged compared to a circular basic shape of the outer outlet opening.

This enables an improved, more intensive mixing of the fuel components, since the enlarged outer outlet opening results in an enlargement of the contact surface of the fuel components.

In addition, the undesired intermediate layer described above, consisting of hot gas, between the spray fractions of the fuel components generated by the first and the second swirl element can be avoided, which results in the intended increase in efficiency.

In one embodiment, the contour of the outlet edge circumference of the outer outlet opening can be undulating. Compared to the basic shape of the circular path, the waves can e.g. run outwards. The waves can be generated by drilling holes in the area of the circular path. The axes of the bores preferably run obliquely relative to a longitudinal axis of the central body. The axes of the bores can intersect at a common point on the longitudinal axis of the central body. The axes of the bores can alternatively describe a circle in a plane which is arranged perpendicular to the longitudinal axis of the central body. The diameter of this circle can correspond to or differ from the diameter of the circular path.

Alternatively or additionally, the contour of the outlet edge circumference of the outer outlet opening can be formed, starting from a basic shape of the outer outlet opening, with a number of largely radially outwardly extending polygons, in particular rectangles. The polygons can be created, e.g. by milling or laser processing, by making slots in the area of the circular path. The longitudinal axes of the slots preferably run obliquely relative to a longitudinal axis of the central body. The longitudinal axes of the slots can intersect at a common point on the longitudinal axis of the central body. The longitudinal axes of the slots can alternatively describe a circle in a plane which is arranged perpendicular to the longitudinal axis of the central body. The diameter of this circle can correspond to or differ from the diameter of the circular path.

When using polygons or rectangles, the basic shape can be the circular path or the wave-shaped contour. In the latter case, this means that the polygons or rectangles are more or less superimposed on the waveform or that waves alternate with polygons or rectangles. The shape can be realized by making appropriate holes and slots in the central body.

The distance between two adjacent waves and / or polygons can be regular over the circumference of the outer outlet opening. Alternatively, the distance between two adjacent waves and / or polygons can be irregular over the circumference of the outer outlet opening. Which shape of the outlet opening is most suitable depends on the geometry of the injection element and can be determined through experiments and / or simulations.

According to a further embodiment, the shape, in particular the size, of the waves and / or polygons can vary over the circumference of the outer outlet opening. Which shape or size of the outlet opening is most suitable depends on the geometry of the injection element and can be determined through experiments and / or simulations. The swirl of the fuel component introduced into the swirl chamber can be generated, for example, by arranging bores running tangentially.

The outer swirl element can comprise, downstream, the essentially cylindrical swirler space in which the fuel component expelled by the outer swirl element is caused to swirl. Due to the imprinting of the twist in the cylindrical area of the element, the liquid follows the wave-shaped or slotted contour at the outlet, which leads to increased instability of the hollow cone and thus to a faster break-up of the hollow cone, which thereby breaks up into droplets more quickly.

The outer swirl element can have a transition section between the swirl chamber and the outer outlet opening, in which there is a continuous transition from the cylindrical shape of the swirl chamber to the contour of the outer outlet opening, which is larger than the circular path. The transition from the cylindrical shape in the upper area to the corrugated edge or slot edge on the injection element takes place continuously over the circumference, whereby the axial length and shape of this transition area can be varied according to the task. While maintaining the acting centrifugal forces, generated by the tangential supply of the media, this leads to a double fan in the injection of the fuel component via the outer swirl element.

According to a further embodiment, the swirl space can taper at the end facing the transition section. As a result of the additional reduction in the swirl chamber diameter in the tapering section, the circumferential speed of the rotational movement of the fuel component to be injected can be increased further, which further improves the efficiency.

According to a further embodiment, the outer swirl element can comprise an undercut, i.e. a so-called recess, so that the first, inner outlet opening is retracted downstream in the direction of the longitudinal axis opposite the second, outer outlet opening. This ensures a geometric overlap of the hollow cones generated by the first and the second swirl element.

• 1 den prinzipiellen Aufbau einer ersten Ausführungsform eines erfindungsgemäßen Doppeldrall-Einspritzelementes in einer perspektivischen Schnittansicht mit wellenförmiger Gestaltung der Austrittskante einer äußeren Auslassöffnung;
• 2 das Einspritzelement aus 1 in einer perspektivischen Darstellung;
• 3 den prinzipiellen Aufbau einer zweiten Ausführungsform eines erfindungsgemäßen Doppeldrall-Einspritzelementes in einer perspektivischen Schnittdarstellung mit geschlitzter Gestaltung der Austrittskante der äußeren Auslassöffnung und schematischer Darstellung der Flüssigkeitsverteilung des äußeren Elementes hinter der Austrittskante;
• 4 die schematische Umfangsverteilung der durch ein äußeres Drallelement eingespritzten (flüssigen) Treibstoffkomponente sowie die Zuordnung von Schlitzen der äußeren Auslassöffnung zu dem Spritzbild; und
• 5a bis 5c das prinzipielle Einspritzbild des inneren Bereiches der äußeren Auslassöffnung eines äußeren Drallelementes, das Spritzbild der durch die Schlitze der äußeren Auslassöffnung bedingten Strahlen sowie das das Gesamteinspritzbild des in 4 gezeigten Einspritzelements.

The invention is described in more detail below using exemplary embodiments in the figures. Show it:

• 1 the basic structure of a first embodiment of a double swirl injection element according to the invention in a perspective sectional view with a wave-shaped design of the outlet edge of an outer outlet opening;
• 2 the injection element off 1 in a perspective view;
• 3 the basic structure of a second embodiment of a double swirl injection element according to the invention in a perspective sectional view with a slotted design of the outlet edge of the outer outlet opening and a schematic illustration of the liquid distribution of the outer element behind the outlet edge;
• 4th the schematic circumferential distribution of the (liquid) fuel component injected through an outer swirl element and the assignment of slots in the outer outlet opening to the spray pattern; and
• 5a to 5c the basic injection pattern of the inner area of the outer outlet opening of an outer swirl element, the spray pattern of the jets caused by the slots in the outer outlet opening and the overall injection pattern of the in 4th injection element shown.

In the following, identical and functionally identical elements are provided with the same reference symbols.

1 shows in a perspective sectional view the basic structure of an injection element according to the invention 1 according to a first embodiment.

The injection element 1 includes a central body 2 , which is largely rotationally symmetrical. The central body 2 comprises a first, inner swirl element 3 and a second, external one Swirl element 5 . The first, inner swirl element 3 is in a cylindrical element space 17th circumferentially with tangential openings 19th Mistake. The tangential openings 19th form inlet openings of the first, inner swirl element 3 out. The element space 17th opens downstream into a narrowing flow channel 18th in the area of a hot gas plate 16 a first, inner outlet or outlet opening 4th includes. One from the exhaust port 4th The fuel component injected into a combustion chamber (not shown) has approximately the shape of a hollow cone.

The second, outer swirl element 5 is coaxial with the first, inner swirl element 3 arranged. It comprises an annular element space 20th , the circumferential with tangential openings 22nd is provided. The element space 20th provides a swirler room 8th in a transition section 9 the element space tapers 20th (see the reference number 10 ) and finally opens into an annular flow channel 21st that is the flow channel 18th circulates. The flow channel 21st includes in the area of the hot gas plate 16 a second, outer outlet or outlet opening 6th . One from the exhaust port 6th The fuel component injected into the combustion chamber also has roughly the shape of a hollow cone.

The tangential openings 19th , 22nd ( 3 ) ensure that the in the element rooms 17th , 20th introduced (in particular storable) fuel components are subjected to a twist. As a result of the narrowing or tapering, the peripheral speed of the relevant fuel components is additionally increased.

The outlet opening 4th can opposite the outlet opening 6th downstream, ie in the direction of the central body 2 , be withdrawn, whereby a mixing of the two fuel components can be improved.

An enlargement of the contact surface of the two fuel components in the combustion chamber is achieved by the shape of the outlet edge circumference according to the invention 7th the second, outer outlet opening ensured. The trailing edge circumference 7th has a contour that is enlarged compared to a circular path by an irregular shape. This ensures, in particular in connection with the through the tangential openings 22nd caused swirl, to an increased instability of the second outlet opening 6th generated hollow cone.

In a first embodiment, which in the 1 and 2 is the trailing edge perimeter 7th wavy. The size and spacing of the waves can be the same or different. The undulating course can be achieved by making appropriate holes in the central body 2 in the area of the outlet opening 6th be generated. The axes of the bores preferably run obliquely relative to a longitudinal axis of the central body 2 . The axes of the bores can intersect, for example, at a common point on the longitudinal axis of the central body. The holes preferably end before the taper 10 of the flow channel 21st , the transition from the cylindrical shape to the trailing edge perimeter 7th takes place continuously. The axial length and shape of this transition area can be varied depending on the task.

In the in the 3 to 5 The second embodiment shown is the trailing edge circumference 7th provided with rectangular slots, which are introduced by milling or other methods in the area of the second outlet opening, which has the basic shape of a circle. The longitudinal axes of the slots preferably run obliquely relative to a longitudinal axis of the central body 2 . The longitudinal axes of the slots can be at a common point on the longitudinal axis of the central body 2 to cut. The number and shape of the slots can in principle be chosen as desired. As in the first embodiment mentioned above, the transition to the exit contour takes place continuously.

The 3 and 4th show a possible design variant as well as its influence on the spray pattern. The 5a to 5c illustrate the fluid preparation with the aid of the injection states of the outer swirl element shown schematically. Here shows 5a the remaining hollow cone portion of the outer element, while in 5b the beam portion caused by the slots is shown schematically. 5c shows the overall injection pattern of the outer swirl element. It can be clearly seen that the enlarged contour of the second, outer outlet opening compared to a circular path due to an irregular shape leads to an increased instability of the second outlet opening 6th emerging hollow cone, which enables the improved mixing of the fuel components.

List of reference symbols

1

Injection element

2

Central body

3

first, inner swirl element

4th

first, inner outlet opening

5

second, outer swirl element

6th

second, outer outlet opening

7th

Trailing edge circumference

8th

Swirl space

9

Transition section

10

rejuvenation

11

wave

12

slot

13

Spray distribution

14th

inner spray portion

15th

external spray portion

16

Hot gas plate

17th

Element space

18th

Flow channel

19th

tangential opening

20th

Element space

21st

Flow channel

22nd

tangential opening

Claims (11)

Injection element for a rocket combustion chamber, which has an at least largely rotationally symmetrical central body (2) with a first, inner swirl element (3) with a first, inner outlet opening (4) and with a second, outer swirl element (5) with an outlet opening (4 ) comprises coaxial, second, outer outlet opening (6) for receiving and injecting a respective fuel component into a combustion chamber, the first, inner swirl element (3) and the second, outer swirl element (5) each being designed to supply a fuel component with a swirl acted upon, the fuel components discharged from the first and second outlet openings (4, 6) mixing in the combustion chamber, characterized in that an outlet edge circumference (7) of the outer outlet opening (6) has a contour which, compared to a circular basic shape of the outer Outlet opening is enlarged. Injection element after Claim 1 , characterized in that the contour of the outlet edge circumference (7) of the outer outlet opening (6) is undulating. Injection element after Claim 1 or 2 , characterized in that the contour of the outlet edge circumference (7) of the outer outlet opening (6) is based on a basic shape of the outer outlet opening (6) with a number of largely radially outwardly extending polygons, in particular rectangles. Injection element after Claim 3 , characterized in that the basic shape is the circular path or the wave-shaped contour. Injection element according to one of the Claims 2 to 4th , characterized in that the distance between two adjacent waves and / or polygons is regular over the circumference of the outer outlet opening (6). Injection element according to one of the Claims 2 to 4th , characterized in that the distance between two adjacent waves and / or polygons over the circumference of the outer outlet opening (6) is irregular. Injection element according to one of the Claims 2 to 6th , characterized in that the shape, in particular the size, of the waves and / or polygons varies over the circumference of the outer outlet opening (6). Injection element according to one of the preceding claims, characterized in that the outer swirl element (5) comprises a substantially cylindrical swirl chamber (8) downstream, in which the fuel component ejected by the outer swirl element (5) is swirled. Injection element after Claim 8 , characterized in that the outer swirl element (5) between the swirl chamber and the outer outlet opening (6) has a transition section (9) in which a continuous transition from the cylindrical shape of the swirl chamber to the contour of the outer outlet opening (which is enlarged compared to the circular path) 6) takes place. Injection element after Claim 8 or 9 , characterized in that the swirl space (8) tapers at the end facing the transition section (9). Injection element according to one of the preceding claims, characterized in that the outer swirl element (5) comprises an undercut.

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