EP3101268B1 - Microwave pulsed ignition generator for a combustion engine - Google Patents

Description

The invention relates to a microwave pulse ignition generator for triggering the combustion of an ignitable fuel-air mixture in a combustion chamber of an engine, with at least one arranged outside the combustion chamber pulsable microwave source and one of the at least one microwave source leading to the combustion chamber microwave waveguide, and with a pulse generator control for the at least a microwave source with which at least the wavelength, the pulse duration, the pulse spacing, the pulse amplitude and / or the modulation of the microwave radiation is adjustable.

In the prior art, ignition systems for internal combustion engines are known, which supply the necessary for triggering the combustion of a fuel-air mixture in a combustion chamber of the engine initial energy based on high-voltage induced sparks. Ignition devices for internal combustion engines are also known from the prior art, in which the initial energy required for igniting the explosion of the fuel-air mixture is supplied by means of high-frequency energy waves, in particular microwaves.

Due to ever stricter legal standards for exhaust emissions and the increasing demand for lower fuel consumption of engines, The improvement of the efficiency of internal combustion engines is an important aspect in engine development. Achieving these goals is only possible with the use of microwave ignition, which significantly increases the spatial extent, the energy released and the duration of the ignition compared with the conventional spark plug so that a more homogeneous and complete combustion is possible. The state of the art of microwave ignition is exemplified in the publication DE 103 56 916 A1 directed.

From the DE 103 56 916 A1 It is known to effect a space ignition in a combustion chamber of an internal combustion engine by means of microwave energy in order to better ignite and burn the combustion of the fuel introduced via a fuel-air mixture. The known device for igniting the combustion of the fuel in the combustion chamber has a microwave source arranged outside the combustion chamber and a microwave window connected to the microwave source, wherein the microwave radiation can be coupled into the combustion chamber via the microwave window so that the coupled-in microwave radiation is distributed from the combustion chamber Fuel is absorbable. As a result of the absorption of energy into the fuel due to the absorption, the combustion is distributed in a large volume in the combustion chamber and can be ignited essentially simultaneously. For this purpose, the microwave radiation in the form of one or more microwave pulses of short duration and high energy coupled, with a power of the microwave pulses between 1 and 70 kW, preferably for the ignition more microwave pulses are used with different power and / or different pulse duration. This Mikrowellenzündvorrichtung comprises a single microwave source per combustion chamber, which is operable by a controlled pulse high voltage power supply. As a microwave source, for example, a magnetron, klystron, gyrotron, a traveling wave tube or the like is provided. These require a complex pulse high-voltage power supply to convert the usual on-board vehicle voltage of 12 or 24 V in the operating voltage for the microwave source. Furthermore The associated microwave sources are of large design and also heavy, technically sensitive and expensive.

DE102011116340A1 describes a device for carrying high frequency microwaves in a high pressure vessel. The device can be used both for the irradiation of energy in high-pressure reactors or for the ignition of combustible gas / air mixtures, such as in internal combustion engines. Based on the above-mentioned prior art, the present invention seeks to propose a way to optimize at least the same ignition power of the microwave pulses, the size, weight and / or reliability of the Mikrowellenzündvorrichtung, ie in particular to provide the necessary components in a housing , which is simply fastened to a cylinder wall laterally surrounding the combustion chamber or to a cylinder head closing off at the top of the combustion chamber, wherein at the same time the microwave hollow conduit is coupled to the combustion chamber. The invention is also based on the object to provide an internal combustion engine with a correspondingly optimized Mikrowellenzündanlage.
This object is achieved by a Mikrowellenpulszündgenerator with the features of independent claim 1 and by an internal combustion engine with the features of the independent claim 15. Further advantageous embodiments can be found in the dependent claims.
According to the invention, the microwave pulse ignition generator has at least two microwave sources and at least one hollow line coupling section in the microwave hollow line, with microwave feed lines each leading from the microwave sources to the hollow line coupling section and the hollow line coupling section being connectable to the combustion chamber via a microwave discharge. The microwave feed lines, the waveguide coupling section and the microwave discharge are formed hollow inside. The ignition power of the microwave pulse ignition generator according to the invention is dependent on the number of microwave sources used and on the strength of the pulsed supply voltage which provides the microwave control for the operation of the microwave sources. The proposed waveguide coupling section allows merging, ie, bundling of the respective microwaves emanating from the microwave sources without significant loss of power.

Thus, a large and heavy microwave source can be easily replaced by a number of smaller microwave sources, wherein the ignition performance of the microwave pulse ignition generator advantageously remains unchanged or can be increased. In particular, the size and number of the smaller microwave sources can be selected and arranged relative to one another in such a way that the overall size and the total weight of the microwave pulse ignition generator can be significantly reduced in comparison with a single strong microwave source. In addition, smaller and thus less radiation microwave sources usually require a reduced operating voltage, so that the pulse generator control can be performed correspondingly weaker, lighter and thus smaller.

The two or more microwave sources of the microwave pulse ignition generator according to the invention are preferably connected directly to the hollow line coupling section, from which the microwave discharge leads to the combustion chamber, wherein the microwave feed lines can run in a straight line and / or bent. However, the invention also includes that with a larger number of microwave sources used, these are guided indirectly to the hollow line coupling section connected to the combustion chamber, i. the microwave radiation from at least two of the provided microwave sources upstream of this hollow duct coupling section, which has the microwave discharge leading to the combustion chamber, brought together via at least one further upstream waveguide coupling section and only then connected to the waveguide coupling section having the microwave derivative.

Preferably, the microwave sources used are semiconductor emitters. Such semiconductor microwave sources are usually small, light, easy to handle, insensitive to interference and easy to control. In addition, they require no complex control, since they can be operated with a relatively small DC voltage, in particular with the battery voltage. In addition, such semiconductor emitters are cost effective in procurement and processing.

The waveguide coupling portion may extend in any direction and in any arbitrary form. In a preferred embodiment of the invention, the waveguide coupling section is straight, wherein the microwave feed lines open laterally into the waveguide coupling section, to which the microwave outlet adjoins the outlet side. In this case, the microwave derivative, which leads to the combustion chamber of the engine, run straight, curved or curved.

Preferably, the microwave feed lines open in the axial direction and / or in the circumferential direction in the hollow line coupling sections offset from one another. The offset is favorably chosen such that the microwaves from the various microwave feed lines after entering the waveguide coupling section do not or as little as possible mutually influence each other, resulting in a reduction of the intensity of the respective microwave radiation. Preferably, the offset is formed such that in the waveguide coupling section results in an amplification of the intensity of the microwave radiation, which is derived by the microwave derivative. In this case, the microwave derivative preferably extends straight to the waveguide coupling section, i. the microwave dissipation includes concentrically arranged directly to the waveguide coupling section.

In a preferred embodiment of the microwave pulse ignition generator according to the invention, one or more of the microwave feed lines opens into the hollow line coupling section at an acute angle. In one embodiment of the invention, one of the microwave feeders also opens axially aligned in the waveguide coupling section. The coaxial alignment of one of the microwave feed line to the rectilinear waveguide coupling section simplifies the entry of the microwave radiation of the associated microwave source into the waveguide coupling section. Advantageously, the microwaves are not changed in their propagation direction, polarization and / or intensity, for example by deflection or scattering. In the laterally opening in the rectilinear waveguide coupling section Mikrowellenzuleitungen is defined as the acute angle between the central axis of the respective microwave feed line and the central axis of the Hohlleitungskoppelabschnittes such that the microwave radiation enters the waveguide coupling section in the direction of microwave dissipation. The acute entry angle into the waveguide coupling section is preferably identical in all microwave feed lines. The incoming microwave radiation is thus changed only slightly in the respective propagation direction, which leads to the fact that the phase relationship of the laterally entering microwaves to each other is substantially maintained. In particular, all microwaves entering at the side have microwaves with respect to the microwaves entering the waveguide coupling section at the end face and the same phase relation to one another before and after entry into the waveguide coupling section.

In an advantageous embodiment of the invention, in each case one microwave inlet is arranged at a transition of the microwave feed lines to the hollow line coupling section and only one microwave outlet is arranged at a transition of the hollow line coupling section to the microwave discharge. The microwave inlets and / or the microwave outlet can be designed as simple openings or closed by means of a window having optical means, for example for beam shaping, beam steering or beam polarization.

In the waveguide coupling section, the microwaves of the intended microwave sources, which in particular preferably temporally and / or spatially coherently propagate towards each other, are superimposed to amplified microwave radiation entering the microwave output of the waveguide coupling section and coupled into the combustion chamber for ignition of the fuel-air mixture becomes. Thus, in the case of the interference of the microwaves which have entered the waveguide coupling section, no total or partial extinction of the microwave radiation occurs, it must be ensured that the microwaves entering the waveguide coupling section have either different polarization directions and / or no excessive phase offset. Different polarization directions can For example, be achieved by provided at the microwave inputs polarization filter. Such filters are expensive and naturally reduce the radiation intensity of the passing microwaves, which is unfavorable.

Therefore, in an advantageous embodiment of the invention, a phase shift of typically 360 ° after passing through the microwave inlets is provided in the waveguide coupling section. This can be technically particularly simple and inexpensive to achieve, since in the pulse generator control no frequency modulator for the modulation of microwaves is necessary. Due to this special phase offset, the wave crests and the wave troughs of the respective microwaves are substantially congruent, so that the interference automatically results in an amplification of the microwave radiation up to the microwave discharge. For this purpose, the microwave inlets along the waveguide coupling section are preferably arranged at a distance from each other which is a whole multiple of the wavelength of the unmodulated microwave radiation. Since the microwaves are preferably millimeter or centimeter waves, the corresponding distances of the microwave inputs to one another can be easily realized. The respective distance is the distance of the central axis of the microwave inputs to one another. In addition, an overmodulation over the frequency of the microwaves may be provided, which reduces a possible partial extinction of the microwave radiation.

In preferred embodiments of the microwave ignition pulse generator according to the invention, the pulse generator control has an electrolytic power capacitor as energy store and / or at least one EMC filter, wherein the pulse generator control is preferably operable with an operating voltage of 12 V or an integral multiple thereof. By the electrolytic power capacitor, a sufficient power supply of the pulsed microwave source is ensured. The at least one EMC filter reliably prevents or at least reduces the emission of interference pulses by the pulse generator control and / or microwave sources essential. By virtue of the fact that the pulse generator control can be operated with an operating voltage which is normal in motor vehicles, the microwave pulse ignition generator according to the invention is particularly suitable for the use of motor-driven means of locomotion.

In a specific preferred embodiment of the invention, the microwave sources, the microwave feeders, the waveguide coupling section, the microwave discharge and the pulse generator control are arranged together in a metallic well-heat generator housing, wherein the microwave feed lines, the waveguide coupling section and the microwave discharge are preferably formed integrally with the generator housing. As a result, a particularly compact design of the proposed microwave pulse ignition generator is provided, which can be arranged by its small space requirement in each means of locomotion to the internal combustion engine near the combustion chamber. Preferably, the generator housing also has integrated cooling channels through passage of a coolant. Thus, the sensitive components of the microwave pulse ignition generator according to the invention, such as the microwave sources and the pulse generator control for a long life sufficiently tempered, i. be cooled. The generator housing is for example a diecast part, which is preferably made of aluminum.

In a preferred embodiment, the generator housing has a connection flange for attachment to a cylinder head or a cylinder wall of the internal combustion engine, which terminate the combustion chamber, wherein the connection flange is preferably round and has a thread and / or a bayonet lock. The connecting flange with the fastening means provided therefor allows a quick and easy attachment outside of the internal combustion engine. The intended connection flange can also be deviating, with suitable connection means to the motor being present in each case.

The internal combustion engine according to the invention with at least one combustion chamber for combustion of a fuel-air mixture and with a Mikrowellenzündsystem for igniting the combustion of the fuel-air mixture has a Mikrowellenpulszündgenerator, as described above, as Mikrowellenzündsystem. The term fuel-air mixture also includes a fuel-oxygen mixture, since the essential component of air for combustion is the oxygen required for this purpose. The fuel is high energy density liquid or gaseous fuel whose chemical energy is converted to motive power by combustion in internal combustion engines, such as in gasoline or diesel engines, gas turbines, rocket engines, or other internal combustion engines. Such motor drives can be provided for driving any means of transportation or stationary use for the operation of any stationary mechanical devices. Possible designs of the internal combustion engine according to the invention are reciprocating engines, rotary piston engines or turbine engines. In this context, fuel is to be understood as meaning, in particular, a substance which is used to drive a means of locomotion or to operate a stationary machine. Particularly common is the term fuel in the field of shipping, aerospace. This includes the usual term for land vehicles fuel.

Figur 1

den Aufbau eines erfindungsgemäßen Verbrennungsmotors mit einem Mikrowellenpulszündgenerator pro Brennraum, in schematischer Darstellung;

Figur 2

den Mikrowellenpulszündgenerator mit Hohlleitungskoppelabschnitt aus Figur 1 in einer vergrößerten Schnittdarstellung; und

Figur 3

den Hohlleitungskoppelabschnitt aus Figur 2 in einer vergrößerten Ausschnittdarstellung.

The invention will be explained in more detail with reference to an embodiment shown in the drawing. Further features of the invention will become apparent from the following description of the embodiment in conjunction with the claims and the accompanying drawings. The individual features of the invention may be implemented on their own or in several different embodiments of the invention. Show it:

FIG. 1

the construction of an internal combustion engine according to the invention with a microwave pulse ignition generator per combustion chamber, in a schematic representation;

FIG. 2

the Mikrowellenpulszündgenerator with waveguide coupling section FIG. 1 in an enlarged sectional view; and

FIG. 3

the waveguide coupling section FIG. 2 in an enlarged detail view.

FIG. 1 schematically shows the structure of a designed as a reciprocating engine according to the invention internal combustion engine 1. It is only a single cylinder 2 of the internal combustion engine 1 shown. The cylinder 2 has, as usual, a combustion chamber 3, which is bounded by a movable piston 4, a cylinder 5 and a cylinder head 6. On the cylinder head 6, a microwave pulse ignition generator 7 according to the invention is arranged centrally. This is provided for triggering the combustion of an ignitable fuel-air mixture in the combustion chamber 3, which is not shown in the figure. The microwave pulse ignition generator 7 comprises at least two microwave sources 8, at least one microwave waveguide 9 leading to the combustion chamber and a pulse generator controller 10 for the at least two microwave sources 8 with which at least the wavelength, the pulse duration, the pulse spacing, the pulse amplitude and / or the modulation of the microwave radiation can be set , The components of the microwave pulse ignition generator 7 are in the FIG. 1 only partially and incompletely represented. The FIG. 2 shows the microwave pulse ignition generator 7 in an enlarged view, with all the essential components of the microwave pulse ignition generator 7 are completely shown. The microwave sources 8, the microwave hollow conduit 9 and the pulse generator control 10 are arranged in a generator housing 11, which has a round connection flange 12 for fixing to the cylinder head 6. The connecting flange 12 carries on its outer circumference a connecting thread with which the Mikrowellenpulszündgenerators 7 similar to a spark plug in a provided on the cylinder head 6 internal thread can be screwed.

Of the FIG. 2 it can be seen that the microwave pulse ignition generator 7 has in its center 13 a plurality of microwave sources 8 which are connected to a hollow line coupling section 15 of the microwave hollow line 9, in each case microwave feed lines 14 lead from the microwave sources 8 to the hollow line coupling section 15 and to the hollow line coupling section 15 on the outlet side a microwave discharge line 16 connects, which is connectable or connected to the combustion chamber 3. To the pulse generator controller 10 lead from the outside electrical connection lines and from the pulse generator controller 10 to the microwave sources 8 each electrical connection lines, which in the FIG. 2 are not visible. The illustrated waveguide coupling section 15 is straight, with all the microwave feed lines 14 open laterally except for one into the waveguide coupling section 15, to which the microwave discharge line 16 adjoins the outlet side centrically. The microwave discharge 16 extends in a straight line to the hollow line coupling section 15 and leads without twisting to the combustion chamber 3 of the cylinder 2.

Again FIG. 3 clearly shows, extend laterally into the hollow line coupling section 15 Mikrowellenzuleitungen 14 at an acute angle to the waveguide coupling section 15 and corresponding to the Hohlleitungskoppelabschnitt 15. Furthermore, one of the Mikrowellenzuleitungen 14 opens axially aligned at the microwave lead 16 remote end into the waveguide coupling section 15th At the ends of the microwave feed lines 14 remote from the waveguide coupling section 15, a microwave source 8 is arranged in each case. The microwave feed lines 14, the waveguide coupling section 15 and the microwave discharge line 16 form the hollow microwave waveguide 9 of the microwave pulse ignition generator 7. This is designed to be very smooth inside and preferably polished.

At a transition of the microwave feed lines 14 to the hollow line coupling section 15, a microwave inlet 17 is arranged in each case and a single microwave outlet 18 is arranged at a transition of the hollow line coupling section 15 to the microwave discharge line 16. The intended microwave inlets 17 are distributed uniformly along the waveguide coupling section 15 at a distance from each other which is a whole multiple of the wavelength of the microwave radiation.

The in the FIG. 2 schematically illustrated pulse generator control 10 has an electrolytic power capacitor, not shown in the drawing from energy storage and a likewise not shown EMC filter. The pulse generator controller 10 is operated with an operating voltage of 12 V. That in the FIG. 2 Fully shown generator housing 11, in which the microwave sources 8, the microwave feeders 14, the waveguide coupling section 15, the microwave line 16 and the pulse generator control 10 are arranged together, is made of a good heat conductive metallic material, preferably made of aluminum. The intended microwave feed lines 14, the waveguide coupling section 15 and the microwave discharge line 16 are formed integrally with the generator housing 11, preferably as bores. In addition, 11 cooling channels 19 are introduced for the passage of a coolant, not shown in the drawing in the generator housing.

Claims (15)

1. A microwave pulsed ignition generator (7) for initiating the combustion of an ignitable fuel-air mixture in a combustion space (3) of a motor (1) with at least one pulseable microwave source (8) arranged outside the combustion space (3) and a microwave wave guide (9) leading from the at least one microwave source (8) to the combustion space (3) and with a pulse generator controller (10) for the at least one microwave source (8), with which at least the wavelength, the pulse duration, the pulse spacing, the pulse amplitude and/or the modulation of the microwave radiation is adjustable, characterised by at least two microwave sources (8) and at least one waveguide coupling section (15) in the microwave waveguide (9), wherein respective microwave supply lines (14) lead from the microwave sources (8) to the waveguide coupling section (15) and the waveguide coupling section (15) is connectable to the combustion space (3) via a microwave discharge (16).
2. A microwave pulsed ignition generator as claimed in Claim 1 characterised in that the microwave sources (8) are semiconductor emitters.
3. A microwave pulsed ignition generator as claimed in Claim 1 or 2, characterised in that the waveguide coupling section (15) is straight and the microwave supply lines (14) into the waveguide coupling section (15), to which the outlet of the microwave discharge (16) is connected, discharge laterally and at the end.
4. A microwave pulsed ignition generator as claimed in Claim 3, characterised in that the microwave discharge (16) extends in a straight line to the waveguide coupling section (15).
5. A microwave pulsed ignition generator as claimed in Claim 3 or 4, characterised in that one or more of the microwave supply lines (14) discharge into the waveguide coupling section (15) at an acute angle.
6. A microwave pulsed ignition generator as claimed in Claim 3 or 4, characterised in that one of the microwave supply lines (14) discharges into the waveguide coupling section (15) axially aligned.
7. A microwave pulsed ignition generator as claimed in one of the preceding Claims 3 to 6, characterised in that arranged at a transition of the microwave supply lines (14) to the waveguide coupling section (15) there is a respective microwave inlet (17) and arranged at a transition of the waveguide coupling section (15) to the microwave discharge (16) there is a microwave outlet (18).
8. A microwave pulsed ignition generator as claimed in Claim 7, characterised in that the microwave inlets (17) are arranged along the waveguide coupling section (13) at a spacing from one another, which is a whole number multiple of the wavelength of the microwave radiation.
9. A microwave pulsed ignition generator as claimed in one of the preceding claims, characterised in that the pulse generator controller (10) includes an electrolyte power capacitor as a power store and/or at least one EMV filter.
10. A microwave pulsed ignition generator as claimed in one of the preceding claims, characterised in that the pulse generator controller (10) is operable with an operating voltage of 12 volts or a whole number multiple thereof.
11. A microwave pulsed ignition generator as claimed in one of the preceding claims, characterised in that the microwave sources (8), the microwave supply lines (14), the waveguide coupling section (15), the microwave discharge (16) and the pulse generator controller (10) are arranged together in a metallic, good thermally conductive generator housing (11), wherein the microwave supply lines (14), the waveguide coupling section (15) and the microwave discharge (16) are constructed integrally with the generator housing (11).
12. A microwave pulsed ignition generator as claimed in Claim 11, characterised in that the generator housing (11) includes cooling passages (19) for conducting a cooling medium.
13. A microwave pulsed ignition generator as claimed in Claim 11 or 12, characterised in that the generator housing (11) includes a connecting flange (12) for fastening to a cylinder head (6) or a cylinder wall (5) of the motor (1), which border the combustion space (3), wherein the connecting flange (12) is preferably of round construction and includes a screwthread and/or a bayonet lock.
14. A microwave pulsed ignition generator as claimed in one of the preceding Claims 11 to 13, characterised in that the generator housing (11) is a diecasting, preferably of aluminium.
15. A combustion engine (1) with at least one combustion space (3) for the combustion of a fuel-air mixture and with a microwave ignition system for igniting the combustion, characterised in that the microwave ignition system includes a microwave pulsed ignition generator (7) as claimed in one of the preceding Claims 1 to 14.

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