US20080022992A1

US20080022992A1 - Window device, diagnosis system for combustion processes, and combustion chamber

Info

Publication number: US20080022992A1
Application number: US11/891,299
Authority: US
Inventors: Claus Wahl
Original assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV
Current assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV
Priority date: 2005-02-22
Filing date: 2007-08-09
Publication date: 2008-01-31
Also published as: DE102005009285B3; WO2006089703A1; EP1851482A1

Abstract

A window device for a space laden with carbon-containing particles, in particular, for a combustion space, comprising at least one optically transparent window element, is proposed, the at least one window element having a coating comprising an oxidation catalyst material for degradation of carbon-containing window contaminations.

Description

This application is a continuation of international application number PCT/EP2006/001524 filed on Feb. 21, 2006.
The present disclosure relates to the subject matter disclosed in international application number PCT/EP2006/001524 of Feb. 21, 2006 and German application number 10 2005 009 285.3 of Feb. 22, 2005 which are incorporated herein by reference in their entirety and for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to a window device for a space laden with carbon-containing particles, in particular, for a combustion space, comprising at least one optically transparent window element.
It may prove necessary to observe combustion processes. Window devices of the kind described at the outset are required for this.

SUMMARY OF THE INVENTION

In accordance with the present invention, a window device is provided, which can be employed in a simple way.
In accordance with an embodiment of the invention, the at least one window element has a coating comprising an oxidation catalyst material for degradation of carbon-containing window contaminations.
Carbon-containing particles such as soot particles may settle on the at least one window element of the window device, or a layer of tar may also form on the at least one window element. The transparency is thereby impaired, and, in the worst case, observation of the space is no longer possible, i.e., the window device no longer fulfills its function.
In accordance with the invention, a coating consisting of an oxidation catalyst material for carbon is provided. Carbon can thereby be catalytically oxidized to volatile constituents, in particular, during the combustion of hydrocarbons, so that window contaminations can be chemically degraded. A self-cleaning effect for the corresponding window device is thereby provided, whereby the observability is, in turn, ensured.
With the solution according to the invention, for example, direct combustion processes can be observed by means of, for example, a diagnosis system. By virtue of the self-cleaning effect, a high degree of reliability is ensured in a quantitative evaluation of the observation. The results of the analysis can then also be used, for example, for controlling the combustion.
The window device according to the invention may be provided as a separate device. It may also be, for example, part of an optical diagnosis system, which, for example, comprises one or more light guides. In this case, a light guide may constitute a window element, and the coating is then disposed on the light guide.
In particular, the oxidation catalyst material is so selected that window contaminations are degradable above a limit temperature. At high temperatures from approximately 600° C. to 700° C., carbon-containing window contaminations such as layers of soot and layers of tar usually decompose by themselves. Such deposits on windows can also be degraded at lower temperatures by means of an oxidation catalyst material. In particular, deposits of carbon-containing material on windows are degradable above a temperature of from approximately 300° C. to 450° C.
The oxidation catalyst material comprises, in particular, a material from the 8^thsubgroup of the Periodic Table. The coating may consist of such a material, or further materials may be present in the coating. It is also possible for the coating to comprise different oxidation catalyst materials.
In particular, the coating comprises platinum. Platinum acts as an oxidation catalyst material, by means of which carbon can be chemically transformed into volatile constituents. The coating may be formed from platinum or comprise platinum.
For example, the coating is made from platinum or platinum-rhodium.
It is also conceivable for, for example, yttrium or palladium to be used as oxidation catalyst material.
It may, for example, also be provided that the oxidation catalyst material comprises cerium oxide (CeO₂). The coating may be entirely or partially made from cerium oxide. It is expected that the ignition temperature of soot will be reduced to 300° C. to 350° C. by cerium oxide as oxidation catalyst material.
The coating can be produced in a simple way by vapor-depositing. A thickness of the coating in the nanometer range or submicrometer range can thereby be produced, which has a sufficient oxidation catalyst property and, on the other hand, does not impair the transparency of the window element to any considerable degree.
It may be advantageous for the coating to be subjected to a temperature treatment. This may possibly ensure better adhesion of the corresponding coating; for example, the coating is sintered.
In particular, the coating forms a surface of the at least one window element, i.e., the coating on the window element faces outwards (so that it can face into the combustion space).
It is then expedient for the coating to face towards the inside area of the space laden with carbon-containing particles so as to be able to degrade window contaminations coming from the inside area.
In accordance with the invention, a coating with a material from the 8^thsubgroup of the Periodic Table and, in particular, a platinum coating or platinum-containing coating, or a coating with cerium oxide, is used on an optically transparent window element for degradation of deposits of carbon-containing material on windows.
In accordance with the invention, a diagnosis system for combustion processes is provided, which comprises at least one optical sensor and one or more window devices according to the invention. By means of the window device with the at least one optically transparent window element, electromagnetic signals can be coupled out and fed to an optical sensor for detection. The coupling-out of signals is ensured by the solution according to the invention.
The solution according to the invention may, for example, be formed on a light guide, or a window device may be provided, which is disposed in front of a light guide.
The solution according to the invention may be employed, in particular, in conjunction with a diagnosis system as described in DE 199 01 795 A1 and in U.S. Pat. No. 6,487,899.
Furthermore, in accordance with the invention, a combustion chamber with a combustion space, having at least one window device according to the invention, may be provided.
The combustion space of such a combustion chamber can be observed by means of the at least one window device, with no mechanical cleaning of the window device being required or the cleaning intervals for the mechanical cleaning be considerably prolongable.
The following description of preferred embodiments serves in conjunction with the drawings to explain the invention in more detail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of an embodiment of a combustion chamber which is provided with an embodiment of a window device according to the invention;
FIG. 2 shows a schematic representation of an embodiment of a diagnosis system which is disposed on a combustion chamber; and
FIG. 3 shows an enlarged detail of the diagnosis system according to FIG. 2 in a sectional view.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of a window device according to the invention, designated by 10 in FIG. 1, comprises a window element 12 which is optically transparent. The window element 12 is made, for example, of quartz glass.
The window element 12 is, for example, in the form of a window pane with flat surfaces 14, 16 spaced apart in parallel relation to each other.
The window element 12 is held, for example, on a frame 18. By means of this frame 18, the window device 10 is seated on a combustion chamber 20. The frame 18 is fixed to a combustion chamber wall 22 and held in this wall.
The combustion chamber 20 comprises a combustion space 24 which is laden with carbon-containing particles such as soot particles. The carbon-containing particles result from the combustion (indicated by reference numeral 26) of, for example, hydrocarbons.
The carbon-containing particles may form a deposit on the window element 12. Soot deposits, tar deposits, etc. may settle on the window element 12. The optical transparency is thereby impaired.
In accordance with the invention, a coating 28 facing towards the combustion chamber 24 is provided on the window element 12. This coating 28 contains an oxidation catalyst material or is formed by an oxidation catalyst material, by means of which carbon is catalytically oxidizable to volatile components. Carbon deposits on the window element 12 can thereby be disintegrated without any mechanical cleaning of the window element 12 being required for maintaining the optical transparency.
In particular, the coating 28 is formed by platinum or platinum-rhodium, or the coating contains platinum or platinum-rhodium as oxidation catalyst material.
It is, for example, also possible for the coating 28 to be formed by cerium oxide (CeO₂) or for the coating to contain cerium oxide as oxidation catalyst material.
In particular, the oxidation catalyst material is vapor-deposited onto the window element 12 to produce the coating 28. The coating 28 forms a surface of the window element 12, which faces into the combustion space 24.
It may be provided that after its application, a coating is subjected to a temperature treatment in order to ensure better adhesion of the thus modified coating 28.
The thickness of the coating lies in the nanometer range (with a thickness of a few nanometers) or in the submicrometer range. The thickness of the coating should be comparable to the wavelength of light and, in particular, it should be smaller.
By virtue of the solution according to the invention, contaminations of the window element 12 can be degraded at least above certain temperatures, so that no mechanical cleaning is required. For example, it is thus possible for carbon-containing contaminations on the window element 12 to be degraded above a temperature of from approximately 300° C. to 450° C.
A window device according to the invention with one or more coated window elements can be disposed directly on a combustion chamber 20. It is also possible for one or more corresponding window devices to be disposed at a space such as, for example, a flue space, which is in communication with a combustion chamber 20.
For example, it may also be provided that a diagnosis system for combustion processes is provided with one or more window devices according to the invention.
An example of a diagnosis system for combustion processes is shown schematically in FIG. 2 and designated there in its entirety by 30. It comprises one or more diagnosis elements 32 insertable in a combustion space 34 in order to detect electromagnetic radiation occurring in the combustion chamber. The combustion space 34 is enclosed by a combustion chamber wall 36. The diagnosis system 30 comprises, in particular, one or more optical sensors.
The diagnosis element 32 is, for example, in the form of a spark plug and has the usual spark plug elements and functions. For example, a screw-in member 38 is provided, which is screwable into a threaded bore 40 of the combustion chamber wall 36 and carries an earth electrode 42 on its side facing the combustion space 34. Such an earth electrode 42 is usually bent. The screw-in member 38 comprises an external thread 39.
Inserted in the screw-in member 38 is a ceramic member 44 which insulates a high-voltage electrode 46 extending through the ceramic member 44 from the screw-in member 38. The high-voltage electrode 46 projects with a front end 48 over the ceramic member 44 and is seated at a defined distance from the earth electrode 42 so as to be able to generate the ignition spark.
The ceramic member 44 is provided with a number of through-holes 50 (FIG. 3), which extend from an end portion 52 of the ceramic member 44 that is remote from the screw-in member 38 to a front end portion 54 of the ceramic member 44 that tapers conically in relation to the screw-in member 38 and projects into the combustion space 34, and through this end portion 54 to an opening 56 on the combustion chamber side, which preferably lies close to the end 48 of the high-voltage electrode 46 at its combustion chamber side and in the region of a conical surface 58 of the front end portion 54. The conical surface 58 preferably extends conically in relation to an axis 60 which, at the same time, is the center axis of the high-voltage electrode 46.
Inserted in each of the through-holes 50 is a light guide 62, which passes through the respective through-hole 50 and terminates with a light guide end 64 at the combustion chamber side. The light guide end 64 is preferably disposed so as to still lie in the through-hole 50 extending through the ceramic member 44 at a distance from the opening 56 thereof at the combustion chamber side, so that a portion 66 of the through-hole 50, which serves to protect the light guide end at the combustion chamber side, remains between the light guide end 64 at the combustion chamber side and the opening 56 at the combustion chamber side.
At the same time, the portion 66 serves to define for the electromagnetic radiation entering from the combustion space 34 an aperture screen which sets an aperture A, with which it is possible to detect electromagnetic radiation from a spatial area 49 of the combustion space 34.
The light guide end 64 may be provided with a coating corresponding to the coating 28. A window element is thereby formed by means of the light guide itself, and the coating (indicated by reference numeral 70 in FIG. 3) provides for a “self-cleaning” of the light guide end 64 with respect to carbon deposits.
(Alternatively or additionally), it is also possible for a window device 72 comprising a window element with a coating as described hereinabove to be disposed at or in the proximity of the opening 56. The portion 66 and hence the light guide end 64 is mechanically closed off from the combustion space 34 by the window device 72, so that no carbon-containing particles can reach the light guide end 64.
The window device 72 with its oxidation catalyst material coating has, as described hereinabove, a self-cleaning effect.
The light guide ends 64 are formed or possibly ground such that a central direction of incidence E, forming a bisector of the aperture A, of the electromagnetic radiation coming from the combustion space 34 can run at an angle to the center axis 60 and preferably also at an angle to a longitudinal direction 74 of the through-hole 50 in a portion 76 of the through-hole 50 following on from the portion 66, this portion 76 extending as far as an opening of the through-hole 50, which is remote from the combustion space 34, and from which, for example, the light guide 62 is led out and led to a diagnosis-compiling device 78.
The diagnosis-compiling device 78 comprises one or more optical sensors, and, in particular, each light guide has its own optical sensor.
A diagnosis system 30 as described hereinabove is disclosed in DE 199 01 795 and in U.S. Pat. No. 6,487,899 and explained in more detail therein. Reference is made explicitly to this publication.
Combustion processes in the combustion space 34 can be analyzed and a diagnosis made with such a diagnosis system. The combustion processes can, for example, be controlled on the basis of the diagnosis.
A deposit of carbon-containing material such as soot and/or tar can be degraded by the window device according to the invention (formed either by means of the light guide with the coating 70 or by a separate window device 72), i.e., a self-cleaning function can be provided. The optical transparency is thereby ensured, so that light signals can reach the diagnosis-compiling device 78 with its optical sensors.

Claims

1. Window device for a space laden with carbon-containing particles, comprising:

at least one optically transparent window element;

wherein said at least one window element has a coating comprising an oxidation catalyst material for degradation of carbon-containing window contaminations.

2. Window device in accordance with claim 1, wherein the oxidation catalyst material is so selected that window contaminations are degradable at least above a limit temperature.

3. Window device in accordance with claim 1, wherein the oxidation catalyst material is so selected that window contaminations are degradable at least above a temperature ranging from 300° C. to 450° C.

4. Window device in accordance with claim 1, wherein the oxidation catalyst material comprises a material from the 8^thsubgroup of the Periodic Table.

5. Window device in accordance with claim 1, wherein the coating comprises platinum.

6. Window device in accordance with claim 1, wherein the coating is made of platinum or platinum-rhodium.

7. Window device in accordance with claim 1, wherein the oxidation catalyst material comprises cerium oxide.

8. Window device in accordance with claim 1, wherein the coating is vapor-deposited.

9. Window device in accordance with claim 1, wherein the coating is subjected to a temperature treatment.

10. Window device in accordance with claim 1, wherein the coating forms a surface of the at least one window element.

11. Window device in accordance with claim 1, wherein the coating faces towards the inside area of the space laden with carbon-containing particles.

12. Window device in accordance with claim 1, wherein the space laden with carbon-containing particles is a combustion space.

13. Use of a coating with a material from the 8^thsubgroup of the Periodic Table, in particular, a platinum coating or platinum-containing coating, or with cerium oxide, on an optically transparent window element for degradation of deposits of carbon-containing material on windows.

14. Diagnosis system for combustion processes, comprising:

at least one optical sensor; and

one or more window devices, said window device comprising:

at least one optically transparent window element;

15. Combustion chamber with a combustion space, which is provided with at least one window device, said window device comprising:

at least one optically transparent window element;