IL309595A

IL309595A - Use of a rocket propellant, drive device with a rocket propellant and underwater transport device

Info

Publication number: IL309595A
Application number: IL309595A
Authority: IL
Original assignee: Deutsches Zentrum F?R Luft Und Raumfahrt E V
Priority date: 2021-09-26
Filing date: 2022-08-30
Publication date: 2024-02-01
Also published as: EP4405580B1; EP4405580C0; EP4405580A1; WO2023046426A1

Description

WO 2023/046426 1 PCT/EP2022/0740 DLR-4177 WO 2022-08- Description Title Use of a rocket propellant, drive device with a rocket propellant and underwater transport device Prior art The invention relates to the use of a rocket propellant, a drive device with a rocket propellant, and an underwater transport device.

Gel-like fuels and the applications thereof are described, for example, in the articles "An Overview of Investigations on Gel Fuels for Ramjet Applications" by H K Ciezki and B Natan, International Symposium on Airbreathing Engines, ISABE 2005, Munich, September 2005, "Theoretical approaches on the influence of non-linear material properties of gel propellants on the flow in injectors" by H K Ciezki et al, 33rd International Annual Conference of ICT, Karlsruhe, 2002, or "The status of gel propellants in year 2000" by B Natan and S Rahimi, in Combustion of Energetic Materials, Editors K K Kuo, L DeLuca, Boca Raton, 2001, or B Natan et al "Gel propellants," Progress in Energy and Combustion Science, Volume 83, March 2021.

DE 102005030437 B4 describes measures for reducing the viscosity of fuel gels in rocket engines.

Unlike solid or liquid rocket propellants, gel-like fuels for rocket drives allow for improved storage capacity and handling.

Disclosure of the Invention One object is to specify a drive device in which a gel-like rocket propellant is used.

Another object is to specify an underwater transport device with a drive device in which a gel-like rocket propellant is used.

WO 2023/046426 2 PCT/EP2022/0740 DLR-4177 WO 2022-08- Another object of the invention is to specify a use of a gel-like rocket propellant.

The objects are achieved by the features of the independent claims. Favorable embodiments and advantages of the invention result from the further claims, the description, and the drawing.

In the following, the term "propellant" refers both to monergolic propellants and diergolic propellants, wherein tripropellant (triergolic) systems or other higher systems should also be included.

In general, rocket propellants that do not require separate ignition, but are self-sustaining in terms of their reaction, are referred to as hypergolic.

Furthermore, the term "engine" includes both an engine with a rocket engine mode and an engine with a ramjet engine mode, as well as an engine with a ramjet-rocket engine mode.

According to one aspect of the invention, a drive device for an underwater device is proposed, comprising at least one tank with a gel-like rocket propellant consisting of at least one fuel gel and an oxidizer gel, with a combustion chamber ending in a thrust nozzle.

Advantageously, a thrust-regulated drive device can be created which is capable of achieving high speeds underwater. In particular, speeds are possible that induce cavitation or super-cavitation around the underwater transport device. The underwater transport device in this case can move through the water practically surrounded by a gas bubble, which is particularly hydrodynamically efficient.

The proposed drive device has the advantageous feature of being particularly compact in size. This means that minimal dimensions for an underwater transport device having a drive device of this kind not exceeding 10 meters, in particular from 4 to 6 meters, or even shorter in certain small versions, can be achieved. Of course, larger underwater transport devices, such as submarines, for example, can also be operated using a drive device WO 2023/046426 3 PCT/EP2022/0740 DLR-4177 WO 2022-08- of this kind. It is also conceivable for multiple drive devices to be used which are combined to drive an underwater transport device of this kind.

The drive device can be advantageously designed as a ramjet engine with a diergolic gel dual-mode gas generator comprising fuel gel and an oxidizer gel (also referred to as a ramjet-rocket engine). The gas generator represents a unit in which the fuel tank, oxidizer tank, control valves for fuel and oxidizer, injector head, optional igniter, and a pre-combustion chamber with a primary combustion zone in which the primary combustion process takes place, are integrated.

Advantageously, a thrust-regulated drive device can be created which can achieve high speeds underwater and exhibit high operational safety due to the gel-like propellant.

Alternatively, instead of a gel dual-mode gas generator, a drive device with gel dual-mode fuel injection can be provided, in which the injector head with an optional igniter is located in the combustion chamber.

A diergolic gel dual-mode gas generator or gel dual-mode fuel injection for the fuel gel and oxidizer gel can be advantageously positioned upstream of the thrust nozzle. This allows for a compact design.

Advantageously, separate control valves for the supply of fuel gel and for the supply of oxidizer gel to the combustion chamber can be operated independently of one another. This enables a favorable fuel-to-oxidizer ratio to be set, depending on the operational mode of the underwater transport device.

Advantageously, the propellant made up of fuel gel and the oxidizer gel can be arranged in separate tanks. In particular, one of the tanks can concentrically surround the other tank. This results in a very compact design. Other tank configurations, such as side-by-side or behind one another, are also possible. The tank configuration can be advantageously adapted to the space available within the underwater transport device.

WO 2023/046426 4 PCT/EP2022/0740 DLR-4177 WO 2022-08- A piston actuation unit can be advantageously arranged to actuate pistons in the at least one tank. In particular, the piston actuation unit may include a pressure generation unit and a pressure chamber.

The pistons can be advantageously actuated with high pressure. For this purpose, the piston actuation unit may have a pressure generation unit and a pressure chamber in operative communication with the pistons. Other actuating methods for actuating the pistons, such as mechanical force transmission or the like, are also optionally possible. This can be advantageously selected based on the specific application of the underwater transport device in each case. The pressure on the pistons exceeds the pressure in the combustion chamber in this case.

The combustion chamber may advantageously comprise an injector head, at least one primary combustion zone, and a mixing zone. In particular, a secondary combustion zone can be arranged between the primary combustion zone and the mixing zone. The secondary combustion zone is particularly advantageous when metal additives are present in the fuel gel. A gas conduit may also be arranged between the combustion chamber and the expansion section of the nozzle, allowing for the placement of control devices in the rear part of the underwater transport device.

At least one water inlet may be advantageously present in at least one zone of the combustion chamber. Optionally, at least one water inlet may be present in the secondary combustion zone or in both the secondary combustion zone and in the mixing zone.

Through the water inlet into the secondary combustion zone or into the secondary combustion zone and into the mixing zone, particularly effective combustion of the propellant, and in particular of the metallic components thereof, when the propellant contains a metal additive, can be achieved, resulting in high thrust. The use of water in ramjet engine mode (also known as ramjet mode) allows for the conservation of oxidizer (gel) and thereby increases the range. 30 WO 2023/046426 5 PCT/EP2022/0740 DLR-4177 WO 2022-08- The use of a gel-like rocket propellant to drive an underwater transport device is particularly advantageous in providing a thrust-regulated, operationally safe drive unit for an underwater transport device which allows high speeds to be achieved.

Advantageously, at least one water inlet into the secondary combustion zone and/or the mixing zone may be adjustable using a water inlet actuator, depending on the speed of the underwater transport device. In this way, the thrust of the drive device can be adjusted, in addition to the independent adjustment of the mass flow of fuel gel and oxidizer gel, by adjusting the mass flow rate of water into the combustion chamber. The water inlet actuator may be a simple inlet valve that either fully opens or fully closes the water inlet. Optionally, the water inlet actuator may be controllable continuously or in multiple stages. A water inlet actuator may be provided at one or multiple water inlets into the combustion chamber or somewhere upstream of the water inlet region in the water supply channel. In addition or alternatively, water distribution actuators can also be used in branches of the water supply.

The drive device used advantageously has particularly compact dimensions. This means that minimal dimensions for an underwater transport device having a drive device of this kind not exceeding 10 meters, in particular from 4 to meters, or even shorter can be achieved. Of course, larger underwater transport devices can also be operated using a drive device of this kind. It is also conceivable for multiple drive devices to be used which are combined to drive an underwater transport device of this kind.

According to another aspect of the invention, an underwater transport device is proposed with a drive device according to the invention, wherein the drive device is designed as a ramjet engine with a diergolic gel dual-mode gas generator or gel dual-mode fuel injection with fuel gel and oxidizer gel for drive with a diergolic rocket propellant.

Advantageously, the proposed underwater transport device with a thrust-regulated drive device of this kind can achieve high speeds underwater. In 30 WO 2023/046426 6 PCT/EP2022/0740 DLR-4177 WO 2022-08- particular, speeds are possible that induce cavitation or super-cavitation around the underwater transport device. This means that the underwater transport device can move through the water practically surrounded by a gas bubble, which is particularly hydrodynamically efficient.

Advantageously, the underwater transport device can be equipped with separate control valves for the supply of fuel gel and for the supply of oxidizer gel to a combustion chamber of the drive device that can be operated independently of one another.

Another aspect of the invention relates to the use of gel-like, diergolic rocket propellant comprising a fuel gel and an oxidizer gel as a propellant for driving an underwater transport device.

The term "propellant" refers both to monergolic propellants and diergolic propellants, wherein triergolic systems or other higher systems should also be included.

A monergolic rocket propellant may be a single propellant species or a mixture of various species that is self-sustaining in terms of their reaction. A diergolic rocket propellant typically consists of a fuel and an oxidizer. Both of these may be a single species of fuel and oxidizer or a combination of multiple species thereof.

The use of gel-like rocket propellant for driving an underwater transport device is particularly advantageous in providing a thrust-regulated, operationally safe drive unit for an underwater transport device which is capable of achieving high speeds.

Gels are non-Newtonian fluids, the rheological behavior of which is shear rate-dependent and/or strain rate-dependent and thixotropic. While there is no strict definition of a gel, a good approximation of it is as a medium that has a colloidal structural network forming a continuous matrix that completely permeates the liquid phase.

WO 2023/046426 7 PCT/EP2022/0740 DLR-4177 WO 2022-08- Based on gel-like propellant, thrust-regulated engines can be provided. These mean that in underwater applications the speed of the underwater transport device can be advantageously controlled. In particular, small, compact engines can be constructed. Gel-like propellants behave similarly to solid propellants under normal environmental conditions, making them easy to store and handle. Under shear stress influence caused by the delivery pressure in the geometry of the delivery lines and the injector head, they become flowable; this enables flow rate control to be implemented, which in turn allows thrust control. Furthermore, gel-like propellants, unlike solid propellants, allow for multiple shutdowns and multiple ignition. Gel-like propellants can be handled relatively safely and can achieve high insensitivity to leaks, for example.

By comparison to these, while solid propellants are storable and easy to handle, once ignited their combustion cannot be stopped and, typically, corresponding engines are also not controllable, or only with exceptional difficulty and effort, and even then, only to a limited extent. Liquid propellant engines, on the other hand, are controllable, but they are highly sensitive to leaks and require significant effort in terms of delivery. Drive devices based on gel-like propellants allow the positive properties of solid drives and liquid drives to be combined.

A gel-like fuel can be achieved by gelling a fuel. Gelling agents are typically organic substances such as cellulose derivatives, pectin, starch, agar, gelatin, etc., or inorganic or low-reactivity particles. These particles can mainly be located in the submicron range, such as pyrogenic silica (Aerosil, Cabosil, etc.), nanoparticles of aluminum (e.g. ALEX), or carbon nanotubes (CNT).

A particular advantage of gel-like rocket propellants is the possibility of being able to use more environmentally friendly substances, thereby avoiding dangerous and aggressive components like hydrazine and derivatives thereof, N2O4 (NTO), or HNO3. Gel-like rocket propellants of this kind are also referred to as "green" propellants in the literature. Another advantage is the long-term storability of gel-like propellants when components are excluded that exhibit autocatalytic processes, are otherwise chemically unstable, or should not be stored for extended periods at ambient temperature and ambient pressure WO 2023/046426 8 PCT/EP2022/0740 DLR-4177 WO 2022-08- without some consideration and pressure, such as N2O that must be stored under pressure.

Further advantages of gel-like propellants include their insensitivity to accidental ignition, resistance to impact, electrical discharge, sedimentation of metal particles in the propellant, for example, evaporation and sloshing of the propellant.

The gel-like propellant may advantageously comprise at least one fuel gel. In particular, the propellant may comprise the fuel gel and an oxidizer gel.

It may also be a combination of various fuels, at least one of which is in gel form, or a combination of various oxidizers, at least one of which is in gel form.

The fuel gel may advantageously contain at least one metal additive, in particular a water-reactive metal additive.

In particular, the metal additive may include metal particles, in particular magnesium particles and/or aluminum particles, and/or metal hydride, in particular aluminum hydride and/or lithium hydride. The metal additive advantageously allows for an increase in the thrust of the underwater transport device.

The propellant, as a fuel gel, may advantageously contain at least one hydrocarbon, in particular n-heptane and/or kerosene. Other hydrocarbons are also conceivable. Mixtures of hydrocarbons, at least one being in gel form, can also be used.

The propellant can advantageously include at least one oxidizer gel, in particular hydrogen peroxide and/or ionic liquids based on ammonium dinitramide and/or hydroxylammonium nitrate. Other oxidizers are also possible. Mixtures of oxidizers, with at least one being in gel form, can also be used.

Drawing WO 2023/046426 9 PCT/EP2022/0740 DLR-4177 WO 2022-08- Further advantages are derived from the following description of the drawings. Exemplary embodiments of the invention are depicted in the figures. The figures, the description, and the claims contain numerous features in combination. A person skilled in the art will also consider the features individually and combine them into further meaningful combinations.

The drawings show the following by way of example: Fig. 1 schematically shows a longitudinal section through an engine with a monergolic fuel gel according to the prior art; Fig. 2 schematically shows a longitudinal section through a diergolic dual- mode gel engine according to an exemplary embodiment of the invention with fuel and oxidizer; Fig. 3 schematically shows a longitudinal section through a diergolic dual-mode gel engine according to an exemplary embodiment of the invention with a gas generator containing fuel and oxidizer; Fig. 4 shows a basic course of mass flows of fuel gel, oxidizer gel, and water in various operating modes with an initial acceleration phase, travel phase, and final acceleration phase with open water supply during the travel phase and the final acceleration phase in an engine according to an exemplary embodiment of the invention; Fig. 5 shows a basic course of mass flows of fuel gel, oxidizer gel, and water in various operating modes with an initial acceleration phase, travel phase, and final acceleration phase with open water supply only during the travel phase in an engine according to an exemplary embodiment of the invention.

Claims

WO 2023/046426 20 PCT/EP2022/0740 DLR-4177 WO 2022-08- Claims

1. A drive device for an underwater device, comprising at least one tank with a gel-like rocket propellant consisting of at least one fuel gel and an oxidizer gel , with a combustion chamber ending in a thrust nozzle, wherein at least one water inlet into the secondary combustion zone and/or the mixing zone is adjustable using a water inlet actuator, depending on the speed of the underwater transport device.

2. The drive device as claimed in claim 1, wherein a diergolic gel dual-mode gas generator or a gel dual-mode fuel injection for the fuel gel and the oxidizer gel is positioned upstream of the thrust nozzle.

3. The drive device as claimed in claim 1 or 2, comprising separate control valves for the supply of fuel gel and for the supply of oxidizer gel to the combustion chamber that can be operated independently of one another.

4. The drive device as claimed in any one of the preceding claims, wherein the propellant made up of fuel gel and the oxidizer gel are arranged in separate tanks, in particular wherein one of the tanks concentrically surrounds the other of the tanks.

5. The drive device as claimed in any one of the preceding claims, wherein a piston actuation unit to actuate pistons is arranged in the at least one tank, in particular, wherein the piston actuation unit includes a pressure generation unit and a pressure chamber.

6. The drive device as claimed in any one of the preceding claims, wherein the combustion chamber comprises an injector head, at least one primary combustion zone, and a mixing zone.

7. The drive device as claimed in claim 6, wherein a secondary combustion zone is arranged between the primary combustion zone and the mixing zone. WO 2023/046426 21 PCT/EP2022/0740 DLR-4177 WO 2022-08-

8. The drive device as claimed in any one of the preceding claims, wherein at least one water inlet is present in at least one zone of the combustion chamber.

9. An underwater transport device with a drive device as claimed in one of the preceding claims, wherein the drive device is designed as a ramjet engine with a diergolic gel dual-mode gas generator or gel dual-mode fuel injection with fuel gel and oxidizer gel for drive with a diergolic rocket propellant.

10. The underwater transport device as claimed in claim 9, with separate control valves for the supply of fuel gel and for the supply of oxidizer gel to a combustion chamber of the drive device that can be operated independently of one another.

11. The use of gel-like, diergolic rocket propellant comprising a fuel gel and an oxidizer gel as a propellant for driving an underwater transport device as claimed in claim 9 or 10.

12. The use as claimed in claim 11, wherein the fuel gel contains at least one metal additive, in particular a water-reactive metal additive.

13. The use as claimed in claim 12, wherein the metal additive includes metal particles, in particular magnesium particles and/or aluminum particles, and/or metal hydride, in particular aluminum hydride and/or lithium hydride.

14. The use as claimed in any one of claims 11 to 13, wherein the propellant, as a fuel gel, contains at least one hydrocarbon, in particular n-heptane and/or kerosene.

15. The use as claimed in any one of claims 11 to 14, wherein the propellant includes at least one oxidizer gel, in particular hydrogen peroxide and/or ionic liquids based on ammonium dinitramide and/or hydroxylammonium nitrate.