Method for introducing microwave energy into a combustion chamber of a combustion engine and combustion engine

Abstract

A method for introducing microwave energy into a combustion chamber of a reciprocating internal combustion engine with at least one cylinder with a cylinder head in which the microwaves reach the combustion chamber through a microwave window, wherein the microwaves are run about a circumference of the combustion chamber and radially injected into the combustion chamber through at least a portion of a combustion chamber wall functioning as a microwave window. The method and the internal combustion engine facilitate a precise control of a beginning of a space ignition of a fuel air mix in the combustion chamber so that an optimum low emission combustion of a fuel is achieved with an efficiency that is higher compared to conventional reciprocating piston combustion engines. In general the invention provides safe ignition of lean fuel air mixtures.

Claims

1. A method for injecting microwave energy into a combustion chamber of a reciprocating internal combustion engine with at least one cylinder with a cylinder head, comprising the steps: running microwaves though at least one annular hollow conductor cavity arranged at a circumference of a combustion chamber; and radially injecting the microwaves into the combustion chamber through at least a portion of a combustion chamber wall functioning as a microwave window, wherein the combustion chamber wall separates the combustion chamber from the at least on annular hollow conductor cavity and is made from a solid temperature stable material which is permeable for the microwaves, wherein the at least one annular hollow conductor cavity includes at least one opening oriented towards the combustion chamber, and wherein the at least one annular hollow conductor cavity is integrated into an engine block of the reciprocating internal combustion engine.

2. The method according to claim 1, wherein the microwaves are injected into the combustion chamber at an angle of 45 at an end of the at least one annular hollow conductor cavity so that the microwaves that are injected into the combustion chamber an angle of 45 at an end of the at least one annular hollow conductor cavity do not interfere with microwave energy injected in a forward direction.

3. The method according to claim 1, wherein the microwaves are injected from the annular hollow conductor cavity through a circumferential gap extending between the annular hollow conductor cavity and the combustion chamber wall, or through a circumferential gap extending between the annular hollow conductor cavity and the combustion chamber wall which circumferential gap increases in size with a length of a path of the microwave in the annular hollow conductor cavity, or through a plurality of intermediary spaces which increase in size with the length of the path of the microwave in the annular hollow conductor cavity and which are arranged perpendicular to a propagation direction of the microwaves between the annular hollow conductor cavity and the combustion chamber wall, or through a combination thereof.

4. The method according to claim 1, wherein the microwaves are injected with a frequency of 25 GHz to 90 GHz.

5. The method according to claim 1, wherein the microwaves are introduced in impulse packets, and wherein the impulse packets are maintained after an ignition of a fuel air mix has already been performed.

6. The method according to claim 1, wherein the microwaves are injected as a function of an angular position of a crank shaft.

7. An internal combustion engine, comprising: at least one cylinder with a cylinder head and a piston in which microwaves are injected through a microwave window into a combustion chamber, wherein the combustion chamber includes a combustion chamber wall which functions as a microwave window at least in portions, and wherein the combustion chamber wall is enveloped by at least one circumferential annular hollow conductor cavity with at least one feed for the microwave and at least one outlet opening for the microwave which outlet opening is oriented towards the combustion chamber wall, wherein the combustion chamber wall separates the combustion chamber from the at least on annular hollow conductor cavity and is made from a solid temperature stable material which is permeable for the microwaves, and wherein the at least one annular hollow conductor cavity is integrated into an engine block of the reciprocating internal combustion engine.

8. The internal combustion engine according to claim 7, wherein a face wall that is oriented at an angle of 45 relative to the at least one annular hollow conductor cavity and an outlet opening in a direction towards the combustion chamber wall are arranged at an end of the at least one annular hollow conductor cavity.

9. The internal combustion engine according to claim 7, wherein a circumferential gap extending between the at least one annular hollow conductor cavity and the combustion chamber wall, a circumferential gap extending between the at least one annular hollow conductor cavity and the combustion chamber wall which circumferential gap increases in size with a length of a path of the microwave in the at least one annular hollow conductor cavity, or a plurality of intermediary spaces which advantageously increase in size with the length of the path of the microwave in the at least one annular hollow conductor cavity and which are arranged perpendicular to a propagation direction of the microwave between the at least one annular hollow conductor cavity and the combustion chamber wall, or a combination thereof is provided.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is subsequently can be described in more detail with reference to schematic drawing figures. Additional features of the invention can be derived from the subsequent description in combination with the patent claims and the appended drawing figures, wherein.

(2) FIG. 1A illustrates an embodiment with annular injection wherein a gap towards the combustion chamber has constant width over a circumference in a schematic top view of a detail of a reciprocating piston internal combustion engine without cylinder head;

(3) FIG. 1B illustrates a sectional view along the line A-A of FIG. 1a with cylinder head;

(4) FIG. 2A illustrates a representation similar to FIG. 1 for a ring injection with a gap increasing over a length of the annular path in a schematic top view without cylinder head;

(5) FIG. 2B illustrates a sectional view along the line A-A of FIG. 2A with a cylinder head

(6) FIG. 2C illustrates a sectional view along the line B-B in FIG. 2B;

(7) FIG. 3A illustrates a representation according to FIG. 2 with ring injection with individual bars offset from one another in a schematic top view without cylinder head (FIG. 3A);

(8) FIG. 3B illustrates a sectional view along the line A-A of FIG. 3A with a cylinder head; and

(9) FIG. 3C illustrates a sectional view along the line B-B of FIG. 3B.

DETAILED DESCRIPTION OF THE INVENTION

(10) In the subsequently described figures the invention is illustrated in an exemplary manner based on various embodiments. Identical or like elements in the individual figures are provided with identical reference numerals.

(11) The figures illustrate a schematic detail of an internal combustion engine 1 with a cylinder head 2 and an engine block 3. The engine block 3 includes a cylinder 4 with a piston 5 that is moveable therein and a combustion chamber 6 partially arranged in the cylinder head 2 above the cylinder 4. A schematically indicated inlet 7 for the fuel air mix leads into the combustion chamber 6. Outlets for the exhaust gas are not illustrated since the outlets can be configured in ways that are well known to a person skilled in the art. The schematically indicated cylinder head 2 with a central inlet 7 for the fuel air mixture can certainly also have additional spark plugs or outlets for the exhaust gases. The spark plugs can be particularly configured microwave spark plugs that are described in the co-owned application EP 15 157 298.9. An additional inner wall 8 is provided in the cylinder 4. The additional wall is made from a material that is suitable for a function of a microwave window. This can be for example a ceramic material, advantageously with a high level of purity, sapphire glass or another suitable material.

(12) In FIG. 1A an annular hollow conductor cavity 9 extends in the engine block 3 about the inner wall 8 wherein the annular hollow conductor cavity includes a annular cavity wall 12 with equal height over the entire circumference towards the inner wall 8, so that a gap 11 is formed through which the microwave supplied through the microwave feed 10 reaches the combustion chamber 6 through the inner wall 8 that is being used as microwave window. As described supra injecting the microwaves into the combustion chamber 6 generates ignition cores for a space ignition of the fuel air mix introduced through the inlet into the combustion chamber 6. FIGS. 1A and 1B illustrate the arrangement of the individual components. In the embodiment according to FIG. 1A the microwave feed 10 is illustrated as a tangential feed wherein this feed can also be provided radially or at an intermediary angle.

(13) FIG. 2 illustrates a similar embodiment wherein the annular cavity wall 12 decreases in height over the length of the path along the inner wall 8 and thus forms a gap 11 that becomes larger and larger in size. As evident from FIG. 2A the annular cavity wall 12 terminates before reaching the face wall 14 so that an opening 13 over an entire height of the annular hollow conductor cavity 9 is obtained. The microwave feed 10 in this embodiment is selected so that the face wall 14 is formed which has the consequence that the microwaves are reflected back by the annular hollow conductor cavity 9 as little as possible but so that they are introduced into the combustion chamber 6 at an angle instead. FIG. 2C illustrates the facts described supra in a different view.

(14) FIG. 3 illustrates an embodiment in which the microwave feed is configured tangential in turn and the annular hollow conductor cavity 9 is continuous like in the embodiment of FIG. 1 and not interrupted like in the embodiment according to FIG. 2. The annular cavity wall 12 in this embodiment is made from individually offset bars 15 so that the microwave introduced through the microwaves feed 10 can reach the combustion chamber 6 through the intermediary spaces 16 between the bars 15 through the inner wall 8 acting as a microwave window In the embodiment the bars 15 have the same width and height and the intermediary space 16 between the individual bars is equal in size. The height as well as the width of the bars 15 as well as the width of the intermediary space 16 can be varied according to the application.

(15) In the illustrated embodiments the annular hollow conductor cavity 9 is arranged in the engine block 3 about the cylinder 4. It is also possible to configure the annular hollow conductor cavity 9 in a cylinder head 2 that is increased in height.

(16) The engine blocks are made from a typical material, typically metal, wherein the material can be selected according to the application. The boundary for the microwaves in the illustrated hollow conductor cavities is certainly made from metal, wherein additional measures can be taken in order to optimize conductivity, for example by surface coating with a highly electrically conductive material.