Injector of an over-enriched fuel-and-air mixture to the combustion chamber of internal combustion engines

Abstract

The invention relates to a fuel injector for injecting an over-enriched fuel and air mixture to the combustion chamber of an internal combustion engine, is characterised in that it comprises: a hydrocarbon liquid fuel spray nozzle, at least one supply of a gaseous carrier, a fuel mixing and evaporation chamber and an injector nozzle to the engine combustion chamber (C.C.), configured such that, during operation, liquid fuel is supplied and heated and compressed gaseous carrier are supplied to the fuel mixing and evaporation chamber of this injector through the spray nozzle, where they are mixed and evaporated as a result of elevated temperature, and the mixture of evaporated fuel with a hot gaseous carrier with low oxygen content thus formed reaches the combustion chamber (C.C.), through the outlet, wherein the gaseous carrier is air or, alternatively, flue gas, at elevated pressure and temperature and having a composition that prevents the initiation of flame combustion, and the gaseous carrier has oxygen content low enough to prevent the initiation of combustion, even under conditions of elevated pressure and temperature.

Claims

1. A fuel injector for injecting an over-enriched fuel and air mixture to the combustion chamber of an internal combustion engine, characterised in that it comprises a hydrocarbon liquid fuel spray nozzle (1), at least one supply of a gaseous carrier (2), a fuel mixing and evaporation chamber (3) and an injector nozzle (4) to the engine combustion chamber (C.C.), configured such that, during operation, liquid fuel is supplied and heated and compressed gaseous carrier (2) are supplied to the fuel mixing and evaporation chamber (3) of this injector through the spray nozzle (1), where they are mixed and evaporated as a result of elevated temperature, and the mixture of evaporated fuel with a hot gaseous carrier with low oxygen content thus formed reaches the combustion chamber (C.C.), through the outlet (4), wherein the gaseous carrier is air or, alternatively, flue gas, at elevated pressure and temperature and having a composition that prevents the initiation of flame combustion, and the gaseous carrier has oxygen content low enough to prevent the initiation of combustion, even under conditions of elevated pressure and temperature.

2. The injector according to claim 1, wherein a gaseous carrier comprising air/oxidant, flue gas, air and flue gas, vapour, an addition thereof or a combination of all the components, is mixed in the injector chamber (3) with heated fuel.

3. The injector according to claim 1, wherein the injection of fuel (1) into the mixing chamber (3) is arranged coaxially relative to the symmetry axis of the mixing chamber, while the intake of the gaseous carrier (2) is arranged axially, tangentially or radially relative to the lateral surface of the mixing chamber (3).

4. The injector according to claim 1, wherein when the intake duct of the gaseous carrier (2) to the mixing chamber (3) is coaxial relative to said mixing chamber, the fuel supply duct is radially introduced to the gaseous carrier supply duct (2) and the fuel is injected coaxially relative to the air flow axis.

5. The injector according to claim 1, wherein the injector is located before the combustion chamber in an internal combustion engine, so that the process of evaporation of liquid fuel is transferred to the injector, from where a rich gaseous mixture is pressed into the combustion chamber.

6. The injector according to claim 1, wherein the injector chamber (3) is large enough to allow complete evaporation of the fuel and to allow preliminary fuel decomposition reactions to take place, in particular with the oxygen or water vapour contained in the carrier.

7. The injector according to claim 1, wherein the oxygen concentration in the gaseous carrier is low enough to prevent the initiation of combustion.

8. The injector according to claim 1, wherein the composition of the mixture in the injector is therefore outside the combustibility range, which prevents flame from being initiated in the injector system, but gives rise to the initiation of preliminary reactions of fuel decomposition.

9. The according to claim 1, wherein the amount of oxygen in the injector supplied to the chamber (3) is low enough to prevent the initiation of the combustion process, but high enough to promote the decomposition process of the evaporated fuel to the extent preventing the formation of carbon deposits.

10. The injector according to claim 1, wherein the fuel supplied to the injector is pre-heated.

11. The injector according to claim 1, wherein pressure in the supply system is high enough to ensure appropriate injection of the evaporated and partly decomposed fuel to the engine combustion chamber.

12. The injector according to claim 1, wherein it its operation is continuous in nature, especially in turbine or jet engines or RDEs (Rotating Detonation Engines).

13. The injector according to claim 1, wherein it is pulsed, especially in piston engines or for PDEs (Pulsed Detonation Engines).

14. The injector according to claim 1, characterised in that it comprises 1 or multiple supply ducts of the gaseous carrier (2).

15. The injector according to claim 14, wherein if at least two or more intake ducts of the gaseous carrier (2) are implemented, then said ducts (2) are selected from any ducts comprising axial, tangential or radial supply (2) relative to the lateral surface of the mixing chamber (3).

Description

[0027] The invention will now be presented in greater detail in a preferred embodiment in reference to the accompanying drawings, in which:

[0028] FIG. 1A-FIG. 1E are diagrams of an injector of an over-enriched continuous combustible mixture of the invention, wherein: FIG. 1A is a general diagram, FIG. 1B illustrates an exemplary method of supplying a gaseous carrier producing turbulence, FIG. 10 illustrates an exemplary method of concurrent supply of a gaseous carrier, FIG. 1D illustrates an exemplary method of perpendicular supply of a gaseous carrier, FIG. 1E illustrates an exemplary method of supplying a gaseous carrier through two channels, namely a concurrent and perpendicular channels.

[0029] FIG. 2A and FIG. 2B are comparison of flames: FIG. 2A the flame generated when the fuel is combusted with the fuel injected directly into the space where the combustion takes place without prior evaporation and mixing; and FIG. 2B the flame generated when combusting an over-enriched fuel and air mixture supplied to the combustion chamber using the injector of the invention.

[0030] FIG. 3A and FIG. 3B illustrate an exemplary distribution of injector nozzles at the inlet of can (FIG. 3A) and ring (FIG. 3B) combustion chambers with continuous operation of turbine, jet or detonation engines (RDEs). On the left: cylindrical inlets of injectors, on the right, diaphragm injector inlets.

[0031] The letters on the above drawings denote the following: [0032] 1injector of hydrocarbon liquid fuel; [0033] 2gaseous carrier supply; [0034] 3mixing chamber; [0035] 4injector nozzle; [0036] C. C. combustion chamber, and the arrow indicates the direction.

PREFERRED EMBODIMENT OF THE INVENTION

[0037] The essence of the invention is explained in the example shown in FIG. 1, where liquid fuel 1 and the heated and compressed gaseous carrier, e.g. air or flue gas 2, are supplied to the mixing chamber 3, where they are mixed and fuel is evaporated. The gaseous carrier should have oxygen content low enough to prevent the initiation of combustion, even under conditions of elevated pressure and temperature. The mixture of evaporated fuel with a hot gaseous carrier with low oxygen content reaches, through the outlet 4, the combustion chamber C.C., where together with the air from the combustion chamber it forms a gas and steam combustible mixture.

[0038] FIG. 1A through FIG. 1E are schematic representation of two embodiments of an injector with a pre-mixing and evaporation chamber.

[0039] Layouts FIG. 1A, FIG. 1B and FIG. 1D relate to an injector with a pre-mixing chamber, wherein the shape of the mixing chamber is axisymmetric, e.g. cylindrical with a conically tapered end, through which products flow to the combustion chamber. In this embodiment, the injection of fuel into the mixing chamber is arranged coaxially relative to the symmetry axis of the mixing chamber, while the intake of the gaseous carrier, e.g. air, is arranged tangentially or radially relative to the lateral surface of the mixing chamber. Accordingly, the gaseous carrier flowing into the mixing chamber forms a turbulence which contributes to better mixing of the fuel and forms a boundary layer in the proximity of the inner side of the lateral walls of the mixing chamber, which prevents fuel particles from contacting the heated walls of the chamber and prevents the deposition of drops of fuel and e.g. formation of slag.

[0040] This simple construction also makes it easy to produce elements for the design of the injector of the invention, so that materials that are more difficult to process can be used to construct it while maintaining low production costs.

[0041] Layout FIG. 10 shows a different embodiment of the injector with the pre-mixing chamber of the invention, also axisymmetric in shape, different in that the intake duct of the gaseous carrier to the mixing chamber is coaxial relative to the mixing chamber. The fuel supply duct is radially introduced to the air supply duct, for example at a 90 angle, and the fuel is injected coaxially relative to the air flow axis. In this embodiment, there is a jet/at the cross-section of the mixing chamber inlet, in the middle of which there is fuel, which is ring-like surrounded by a gaseous carrier, e.g. air. As a result, the gaseous carrier separates the fuel particles from the walls of the mixing chamber. The further part of the mixing chamber can be made analogously to the example of layouts FIG. 1A and FIG. 1B, i.e. can be conically tapered.

[0042] In both embodiments, the gaseous carrier supplied to the mixing chamber is compressed and heated to promote mixing with fuel and evaporation of drops thereof. Carriers can include air, flue gas, water vapour and mixtures thereof, especially of air and flue gas.

[0043] In terms of the safe operation of the injector, the key issue is to ensure the right proportions of mixing the fuel with the gaseous carrier which contains an oxidant. In order to prevent ignition, the control system of the fuel and gaseous carrier supply maintains the fuel concentration in the mixture above the upper combustibility limit, so that the resulting mixture injected into the combustion chamber is over-enriched. This allows, provided there is an appropriate amount of the oxidant in the combustion chamber, for accelerating the combustion process and to control the shape and length of the flame with greater precision than before.

[0044] FIG. 2A is a photograph depicting an exemplary combustion process with liquid fuel being injected into the combustion chamber that has not been previously evaporated or mixed with a gaseous carrier that contains the oxidant. The flame starts only at some distance from the injector and it is of a considerable length. Its shape is rather chaotic; because of the turbulence of the flow in the combustion chamber single tongues of fire can move in different directions or even separate from the central flame. The combustion process of this type is very difficult to control and stimulates local overheating of flue gases, which promotes the formation of noxious substances, e.g. nitrogen oxides or soot.

[0045] Now, FIG. 2B illustrates the combustion process when pre-mixed and evaporated fuel is supplied to the combustion chamber from the injector of the invention. The flame is clearly shorter than the one shown in FIG. 2A and it starts immediately at the injector outlet. The shape and dimensions of the flame can be virtually freely controlled by modifying the injection pressure, the amount of oxidant in the combustion chamber and the shape of the injection nozzle. Moreover, the flame has a homogeneous structure and is free of overheated zones, so that the temperature of the flame can be controlled in order to prevent the formation of noxious substances, e.g. soot or nitrogen oxides.

[0046] The composition of the mixture in the injection system should be within a concentration range to prevent the combustion process (above the upper combustibility limit), but promoting the preliminary decomposition of fuel components, which, following the injection into the combustion chamber, will allow for rapid formation of the combustible mixture and, as a result, rapid combustion. Preferably, the Air to Fuel ratio ranges from 0.1 to approx. 0.4. In the instances shown in FIG. 2A and FIG. 2B, the composition of the mixture is the same: the air to fuel ratio is =0.35.

[0047] Rapid formation of the combustible mixture is of particularly importance when feeding detonation engines, in which case the time to form a combustible (detonating) mixture is very short. Injectors can be pulsed (e.g. in piston engines or for PDEs), or continuous (e.g. in turbine, jet or RDE engines).

[0048] The injectors can be single or multiple (e.g. distributed evenly at the perimeter of the engine chamber). The proposed injection system of evaporated fuel with a small amount of air or flue gas sensitizes the mixture being formed in the combustion chamber to the process of initiating and maintaining the combustion/detonation process.

[0049] The invention discloses an injection system of evaporated fuel and even of fuel that is partially decomposed in a gaseous carrier (by a small amount of air/oxidant, flue gas, air and flue gas, steam, an addition thereof or a combination of all the components) at elevated temperature and elevated pressure, having a composition that prevents the initiation of the combustion process in the injection system, but allowing for the process of evaporation and preliminary preparation/decomposition of the dose being injected to the combustion chamber/detonation chamber.

[0050] The amount of oxygen in the gaseous carrier supplied to the mixing chamber of the injector should be low enough to prevent the initiation of the combustion process, but high enough to promote the decomposition process of the evaporated fuel to the extent preventing the formation of carbon deposits.

[0051] The preliminary decomposition of fuel may also be promoted by fuel vapours reacting with hot water vapour (the reaction of carbohydrates with water vapour with mainly involve the formation of carbon oxide and dioxide, methane and hydrogen).