DE4429860A1 - Injection system for hybrid rocket engines - Google Patents

Abstract

The invention relates to an injection system for hybrid rocket engines which permits the use of medium sized hybrid rockets. The injection system consists of a single vertical feed pipe which is suspended in the interior of an internal burner and is provided with a multiplicity of holes (bores), as a result of which the oxidiser (oxidant, oxidising agent) is injected directly onto the surface of the solid-propellant unit. The more such holes that are provided, the better the mixing of the fuel and oxidiser and the more complete the combustion. For the purpose of protection against the high combustion temperatures, the vertical pipe is advantageously likewise coated with a solid whose gradual combustion is allowed for.

Description

State of the art

Almost all rockets in use today are chemical in nature. Chemical Rocket engines generate their thrust by burning a suitable fuel a suitable oxidizer. The energy released here serves to accelerate the Combustion products against the direction of flight, creating propulsion (thrust). The technical goal is to maximize the gas outlet velocity. Limiting factors in The performance of a chemical rocket engine is particularly the energy content of fuels, the molecular weight of the combustion products, the efficiency of the combustion as well as some technical factors (e.g. pressure and temperature resistance of the combustion chamber). Chemical rocket engines can be roughly divided into solid and rocket Liquid engines.

In the solid fuel engine, fuel and oxygen carrier are intimately mixed. Solid-state engines are structurally simple, but are hardly used in the burning process adjustable and potentially explosive. In addition, the attainable outflow speeds are due to the high molecular weight of the combustion products and the low energy content of the Limited fuels.

Liquid engines do not have these limitations. This is where the oxidizer and fuel (e.g. H₂ and O₂) before liquid. However, liquid engines are structurally complex, especially through the necessary cooling measures on the combustion chamber.

So-called hybrid rockets occupy an intermediate position. Here is the one component (usually the Fuel) solid, the other liquid before.

The solid fuel tank and combustion chamber are identical in hybrid rockets. Mostly as a hollow cylinder solid that is carried out, inside which the combustion takes place (internal burner), protects at the same time the combustion chamber against temperature and Print. The liquid component (the oxidizer) is usually over a kind of shower head on the top End of the combustion chamber (and additionally injected into an existing afterburner). Polyethylene (possibly mixed with Aluminum powder to increase performance) proposed. PE burns high energy and delivers light combustion products.

The hybrid engine thus combines the advantages of the solid engine (simple design, inexpensive fuels) with the advantages of the liquid engine (controllability, high Performance). It also contributes to safety as it cannot explode. The Fuel blocks are safe to use and can be stored indefinitely. Last but not least these reasons, the hybrid engine (as a relatively late development in rocket technology) predicted a great future.  

Criticism of the state of the art

Hybrid engines have so far only been used experimentally in small and low-thrust engines used. When used in large engines, the injection systems have proven themselves after State of the art as limiting factors of engine efficiency, especially in the lower part there is no or insufficient contact between the fuel block Fuel and oxidizer instead. This makes combustion inefficient, the right thing Mixing ratio of the components to one another cannot be guaranteed Fuel evaporates unburned etc. It is therefore necessary to construct an injection system which spread the oxidizer evenly over the focal surface.

invention

The invention relates to a particularly simple injection system for hybrid rocket engines, in which the liquid component ( 1 ) (usually the oxidizer in the form of liquid oxygen) is fed through a downpipe ( 2 ) which is suspended in the combustion chamber of an internal burner ( 3 ) . This downpipe has a large number of bores ( 4 ) through which the oxidizer exits the combustion chamber and is sprayed onto the opposite solid. The more such channels are provided, the more uniform the contact between the oxidizer and the fuel and the more efficient the combustion. The downpipe itself is also coated with solid to protect against the high combustion temperatures ( 3 ). It is accepted that this coating is lost during the combustion process.

The inflow of the oxidizer to the downpipe is sensibly controlled by a valve.

In a particularly simple version of a hybrid rocket, the pressurized gas-powered one Mount the oxidizer tank of the combustion chamber directly. In the course of the ignition process, the inflow released to the downpipe via a simple space membrane. The burning process would then be however not controllable (it could only be done by depressurizing the oxygen tank be canceled), similar to a solid-state engine

The above Injection system is particularly suitable for combustion chambers that are not too high (otherwise the injected oxidizer no longer reaches the opposite solid wall.

benefits

The injection system described above enables the structurally simple (and thus cost-effective) technical implementation of medium-sized hybrid rockets (e.g. upper stages, Apogee motors) with their advantages described in detail above and without the disadvantage incomplete and therefore inefficient combustion of the fuel.

Claims (1)

Injection system for hybrid rocket engines, characterized in that the liquid component is sprayed directly and over the entire combustion surface onto the solid to be burned through a single downpipe which is suspended in the center of the combustion chamber of an internal burner and is provided with a large number of small bores.