DE102023003416A1 - Combustion device and method for combustion - Google Patents

Abstract

Proposed is a combustion device for stabilizing combustion for hybrid rocket engines with an injection element (1) for an oxidizer, having a pre-combustion chamber (4) and a main combustion chamber (3), wherein an impact element (2) for the oxidizer is arranged between the pre-combustion chamber (4) and the main combustion chamber (3), and a method for combustion.

Description

The invention relates to a combustion device for hybrid rocket engines and a method for combustion of fuel.

State of the art

Combustion devices for hybrid rockets are well known. Hybrid rockets use a rocket engine to generate thrust, in which solid fuel is combined with a liquid oxidizer. The advantages of hybrid rockets are their simpler construction and their inherent safety.

Such hybrid rocket engines (HTW) are used, for example, for sounding rockets or orbital launch vehicles. They are operated in particular with a liquid oxidizer (LOX, N2O, H2O2) and solid fuel (HTPB, paraffin, HDPE, plastics, etc.). For reliable and stable combustion, it is necessary that the liquid oxidizer is atomized and vaporized before it can react with the fuel. This typically happens in the front area of the combustion chamber at an injector outlet in the so-called pre-combustion chamber (VBK) and/or before the oxidizer reaches the fuel block. The vaporization is made possible by the corresponding heat input from the combustion of additional fuel in the pre-combustion chamber. Known solutions are often based on additional devices that supply heat. Examples of this are, for example, additional heaters (hybrid or solid propellant) or injection of pyrophoric liquids (TEA/TAB). However, these are disadvantageous because they increase the complexity and also the price, and they reduce the security aspect of the HTW.

The WO 2017/142590 A1 for example, discloses a "hybrid rocket engine with integrated oxidizer tank". The hybrid rocket engine consists of a solid propellant element and an oxidizer tank containing an oxidizer. The solid propellant element adjoins and at least partially delimits a combustion chamber in which the solid propellant and oxidizer are combusted to generate the thrust of the hybrid rocket engine. The oxidizer tank is at least partially located in the combustion chamber, but may also be entirely located in the combustion chamber. The oxidizer tank may be protected by an insulating material, which may also serve as a structural material that can withstand the pressure of the oxidizer. The insulating material and the fuel material may be polymer-based materials as well as different materials with different properties, e.g. by different additives to the same polymer material. The fuel element and the oxidizer tank may be manufactured by additive manufacturing processes, e.g. by adding different materials in different places.

The disadvantage of the known combustion devices is that if the oxidizer does not evaporate sufficiently and is sometimes too cold, the oxidizer interacts with the flame front on the fuel and combustion instabilities arise. These manifest themselves in strong fluctuations in the combustion chamber pressure and the thrust of the HTW. This reduces the performance and stable, safe operation is sometimes not possible. Typically, low-frequency instabilities are obtained, sometimes in combination with acoustic instabilities (various eigenmodes of the combustion chamber) or dynamic couplings with the oxidizer delivery system.

The object of the invention is therefore to provide a combustion device which avoids these disadvantages of the prior art and stabilises the combustion.

disclosure of the invention

The invention is disclosed by the features of the main claim. Embodiments and developments are the subject of the further claims following the main claim.

A combustion device for stabilizing combustion for hybrid rocket engines and a method for burning a fuel are disclosed. The combustion device has a combustion chamber design that enables simple and reliable atomization of the oxidizer. The oxidizer is arranged on several elements. This arrangement can be circular, for example. Propellant or fuel is injected as an oxidizer in liquid form, in particular in the axial direction, into the combustion chamber.

The oxidizer hits a solid surface at the end of the combustion chamber, from which a large part of the fuel is deflected and then redirected into the combustion chamber. This occurs by hitting an impact element built into the combustion chamber, which is designed in particular as a plate. A pre-combustion chamber and a main combustion chamber are formed. The impact element is in particular perpendicular to the flow direction of the oxidizer between the pre-combustion chamber and the main combustion chamber. The The impact element can also be angled to the flow direction and/or be provided with shapes such as pockets or edges that increase the backflow of the oxidizer into the combustion chamber. In this case, the oxidizer is largely atomized into many droplets by the impact.

The diversion also dramatically increases the residence time of the oxidizer in the pre-combustion chamber, which further improves the vaporization and reaction of the oxidizer. The vaporization is supported by additional fuel in the combustion chamber, which reacts with the oxidizer and vaporizes it. The fuel is decomposed and vaporized on the one hand by the heat of combustion in the combustion chamber, but on the other hand also partially by mechanical impact and erosion by the oxidizer. The type of fuel used in the combustion chamber is not primarily decisive.

The combustion device according to the invention has the advantage that the disclosed combustion device for stabilizing combustion is generally applicable, in particular to various types of injectors for hybrid rocket engines (showerhead, impingement, swirl) and also various oxidizers.

Further advantages and advantageous embodiments of the invention can be taken from the following description of the figures, the drawings and the claims.

• 1 zeigt einen Längsschnitt durch eine Vor- und eine Hauptbrennkammer einer Verbrennungsvorrichtung und
• 2 zeigt eine alternative Ausbildung der Verbrennungsvorrichtung im Längsschnitt.

An embodiment of the solution according to the invention is explained in more detail below using the attached schematic drawings. It shows:

• 1 shows a longitudinal section through a pre- and a main combustion chamber of a combustion device and
• 2 shows an alternative design of the combustion device in longitudinal section.

In 1 a combustion device 100 is shown. The combustion device 100 has in particular a single injection element 1. One or more injection elements 1 can be arranged. With the injection element 1, an oxidizer in liquid form is injected at the liquid injection A. The oxidizer strikes an impact element 2. The impact element 2, also referred to as an “impingement device”, has an area 5 as an impact element for a solid fuel. The impact element 2 with the area 5 forms a pre-combustion chamber 4 and a main combustion chamber 3, between which the impact element 2 with the area 5 is arranged. The oxidizer can strike the impact element 2 and/or the area 5, whereby the oxidizer is atomized and also deflected. This increases the residence time and at the same time improves combustion. The solid fuel can also be present due to backflow from a main combustion chamber 3.

In this embodiment, the liquid or partially gaseous oxidizer is injected in an axial direction and moves along a flow line E in the direction of the impact element 2. When it hits the area 5, it hits an impact point B, which acts as the primary atomization area. This causes the flow of the oxidizer to be diverted along a dashed line. This results in heat absorption and vaporization or evaporation C. The now diverted, atomized into droplets and partially vaporized oxidizer then flows past the impact element 2 into the main combustion chamber 3, with the oxidizer then being in a fully gaseous phase D. A granular solid fuel is present in the main combustion chamber 3. In addition, there is the converted oxidizer from the pre-combustion chamber 4, with the oxidizer now being in fully gaseous form. Solid fuel can also be fed into the pre-combustion chamber 4. This can be done from the outside or centrally. There is the possibility of reaction with oxygen O ₂ in the pre-combustion chamber 4.

2 shows a further embodiment of the combustion device. The impact point B of the area of the impact element for solid fuel 5 on the impact element 2 is formed in a different shape and has beveled areas with corners. At these beveled areas with the corners, the oxidizer is deflected differently from the flow line E at the impact points B than in 1 The deflection can, for example, take place in two directions of movement shown in dashed lines, where the heat absorption C can take place. These two directions of movement of the oxidizer flows meet and flow as in the 1 atomized into droplets and partially evaporated past the impact element 2 into the main combustion chamber 3, whereby the oxidizer is then formed in a fully gaseous phase D.

All features presented in the description, the following claims and the drawings can be essential to the invention both individually and in any combination with one another.

list of reference symbols

1

injection element

2

impact element

3

main combustion chamber

4

pre-combustion chamber

5

Solid fuel impact element area

100

combustion device

A

liquid injection

B

impact point

C

heat absorption

D

full-throttle phase

E

flow line oxidizer

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• WO 2017/142590 A1 [0004]

Claims (13)

Combustion device (100) for stabilizing combustion for hybrid rocket engines with an injection element (1) for an oxidizer, having a pre-combustion chamber (4) and a main combustion chamber (3), characterized in that an impact element (2) for the oxidizer is arranged between the pre-combustion chamber (4) and the main combustion chamber (3). Combustion device (100) according to claim 1 , characterized in that the impact element (2) serves to deflect the oxidizer. Combustion device (100) according to one of the Claims 1 or 2 , characterized in that the impact element (2) is formed perpendicular to a flow direction E of the oxidizer between the pre-combustion chamber (4) and the main combustion chamber (3). Combustion device (100) according to one of the Claims 1 or 2 , characterized in that the impact element (2) is angled to the flow direction E of the oxidizer. Combustion device (100) according to one of the Claims 1 or 2 , characterized in that the impact element (2) has pockets or edges, whereby the backflow of the oxidizer into the combustion device is increased. Combustion device (100) according to one of the preceding claims, characterized in that the impact element (2) has a region (5) for the impact of a solid fuel. Combustion device (100) according to one of the preceding claims, characterized in that the deflection of the oxidizer by the impact element (2) increases the residence time of the oxidizer in the pre-combustion chamber (4), whereby the evaporation and reaction of the oxidizer is improved. Combustion device (100) according to one of the preceding claims, characterized in that an intermediate space is formed between the impact element (2) and a casing of the combustion device (100), through which the displaced and vaporized oxidizer can be passed into the main combustion chamber (3), the oxidizer then being formed in a fully gaseous phase D. Method for combustion of fuel in a combustion device (100) according to one of the Claims 1 until 8 , characterized in that a liquid oxidizer is injected at at least one injection element (1) in an axial direction and moves along a flow line E in the direction of the impact element (2). Procedure (100) according to claim 9 , characterized in that the oxidizer, when it strikes the region (5) of the impact element (2), strikes an impact point B which acts as a primary atomization region, thereby diverting the flow of the oxidizer within the pre-combustion chamber (4). Method according to one of the Claims 9 or 10 , characterized in that the evaporation of the oxidizer is assisted by the addition of additional fuel in the pre-combustion chamber (4), which reacts with the oxidizer and evaporates it, wherein the fuel is decomposed and evaporated on the one hand by the heat of combustion in the combustion chamber and/or at least partially by mechanical impact and erosion at the impact element (2) with the area of the impact element for the solid fuel (5). Method according to one of the Claims 9 until 11 , characterized in that the deflection of the flow of the oxidizer results in heat absorption and vaporization C of the oxidizer. Method according to one of the Claims 9 until 12 , characterized in that in the further course the oxidizer, which is now deflected, atomized into droplets and partially vaporized, flows past the impact element (2) into the main combustion chamber (3), wherein the oxidizer is then formed in a fully gaseous phase D.

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