Optics: measuring and testing – Inspection of flaws or impurities – Transparent or translucent material
Reexamination Certificate
2001-04-16
2001-11-13
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Transparent or translucent material
Reexamination Certificate
active
06317205
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for monitoring an optical system having a front lens disposed immediately at a combustion chamber. It also relates to a device suitable for accomplishing the method.
In the combustion of fossil fuel or refuse in a combustion chamber, fluctuations in the calorific value of the fuel or of the fuel mixture occur because of the different origin of the fuel and/or because of the heterogeneous composition of the refuse. These fluctuations increase pollutant emission of the combustion process. These disadvantages also exist in the combustion of industrial residual material. In the case of which, the combustion of solid and liquid as well as gaseous fuels is usually provided simultaneously. Given knowledge of the parameters characterizing the combustion process, the firing control can be optimized, and thus the combustion process as well.
A device for combustion analysis can determine the parameters characterizing the combustion process. The device uses an optical system having a front lens disposed immediately at the combustion chamber, for example, to detect intensity values of the light of the combustion process that, in their totality, yield an image of a flame of the combustion process. The spatially resolved intensity values of the image can then be used, for example, to determine the temperature distribution and the concentration distribution of reaction products arising in the process of combustion. Such a device and a method suitable for operating the device are disclosed in German Published, Non-Prosecuted Patent Application DE 197 10 206 A1.
German Published, No n-Prosecuted Patent Application DE 28 47 935 A1 discloses a device for carrying out a method for finding pollutants on specimens in transmitted light, and for signaling changes in the transillumination of the specimen. Cleaning a transparent body as a function of the degree of pollution is disclosed in German Published, Non-Prosecuted Patent Application DE 29 04 126 A1.
A particular quality of the intensity values used for the analysis is important for reliable optical monitoring of the combustion process, and for a control based thereon. However, because waste products arise during combustion, pollution of the front lens of the optical system used to determine the intensity values, and thus a worsening of the quality of the data can arise. Consequently, there is a need at regular time intervals for time-consuming maintenance and/or cleaning of the front lens of the optical system, which is in direct contact with the combustion chamber. These time intervals are usually determined using empirical values and do not depend on the actual requirement for maintenance and/or cleaning of the front lens of the optical system. For safety reasons, maintenance and/or cleaning work is therefore usually provided more frequently than required for operating reasons. However, this is attended by long down times and a low level of availability of the optical system, and thus also of the combustion chamber.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for monitoring an optical system having a front lens disposed immediately at a combustion chamber, and a device for carrying out the method that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that specifies a method for monitoring an optical system having a front lens disposed immediately at a combustion chamber, in the case of which a particularly low measure of down times, and thus a particularly high level of availability of the optical system is ensured without impairing the reliability of the optical system. This is to be achieved with a particularly low technical outlay in the case of a device suitable for carrying out the method.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for monitoring an optical system. The method includes the first step of providing an optical system with a front lens disposed immediately at a combustion chamber. The next step is recording intensity values from a light of a flame of the combustion chamber with the optical system. The next step is determining a temperature value and a mean intensity value from the intensity values. The next step is determining a relative degree of pollution of the front lens from the temperature value and the mean intensity value. The next step is determining a maintenance time of the front lens.
In accordance with another mode of the invention, the method further includes cleaning the front lens after the maintenance time expires.
In accordance with another mode of the invention, the method further includes determining the mean temperature value of the flame from a first intensity value at a first wavelength and from a second intensity value at a second wavelength of the light of the flame of the combustion chamber.
With the objects of the invention in view, there is also provided a monitoring module for determining a cleaning time of an optical system having a front lens that is disposed immediately at a combustion chamber. The optical system measures a temperature value and a mean intensity value of a flame of the combustion chamber. The monitoring module includes a data processing system connected to the optical system calculating a relative degree of pollution of the front lens from the temperature value and the mean intensity value of the flame of the combustion chamber.
With reference to the method, the object is achieved according to the invention by using the optical system to record intensity values from the light of a flame of the combustion chamber. The front lens surface is cleaned if necessary. A temperature value and a mean intensity value are determined from the intensity values. The relative degree of pollution of the front lens is determined from the temperature value and the mean intensity value and used to determine a cleaning and/or maintenance time of the front lens.
In this case, the invention proceeds from the consideration that, for a particularly low measure of down times of the optical system, a fixed rhythm of maintenance and/or cleaning work for the front lens should not be prescribed. Rather, the front lens should be maintained and/or cleaned flexibly and as required with reference to the actual maintenance and/or cleaning requirement for it. Determining the time of carrying out the maintenance and/or cleaning work should be based in this case on measured data of the optical system. However, in this case impairing the operation of the optical system is to be avoided. If intensity values of the light of a flame of the combustion chamber are determined via the optical system during operation of the combustion chamber, it is possible to derive therefrom a measure of the relative degree of pollution of the front lens of the optical system. Specifically, pollution of the front lens causes a characteristic decrease in the intensity values. A particularly reliable determination of the relative degree of pollution of the front lens is given in this case by comparing an intensity value averaged from directly measured intensity values (actual intensity value) with an intensity value (desired intensity value) that has been determined from a temperature value determined for the flame.
The temperature value required for determining the degree of pollution of the front lens of the optical system is advantageously determined from an intensity value of a first wavelength and from an intensity value of a second wavelength of the light of the flame in the combustion chamber. For this purpose, two narrowband spectral regions each having a wavelength band of approximately ten nanometers (~10 nm) are coupled out of the radiation spectrum of the flame of the combustion chamber. In particular, these spectral regions are each situated in this case in a wavelength region without emission lines of the combustion product, in the so-called band-free regions. Specifically, acc
Font Frank G.
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stafira Michael P.
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