Thermal measuring and testing – Temperature measurement – With fluid flow deflector
Reexamination Certificate
1999-03-31
2001-08-07
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
With fluid flow deflector
C374S144000, C374S148000, C374S179000
Reexamination Certificate
active
06270253
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of temperature measurement technology. It relates to a method for measuring the temperature of hot gases present in a hot gas space, in particular in the combustion chamber of gas turbines, by means of a thermocouple. The invention also relates to a measuring arrangement for carrying out such a method.
BACKGROUND OF THE INVENTION
In order to control and monitor the operation of gas turbines, it is necessary to measure and/or to determine in the combustion chambers of the gas turbines the high temperatures occurring there for the hot gases. Because of the high temperatures and the rugged environment at the measurement site, such a temperature measurement confronts the measurement technology with virtually insurmountable difficulties. One possibility of circumventing these difficulties consists in measuring the temperature of the gases at a cooler point of the machine located further downstream and using the measured data to derive temperatures in the combustion chamber on the basis of a machine model. However, it is disadvantageous in this case that there is only a very indirect and time-delayed relationship between the actually measured temperatures and those to be determined.
Another possibility consists in conducting the temperature measurement by using, for example, thermocouples made from special metals such as platinum and platinum-rhodium which withstand the hot gas temperatures occurring in the combustion chamber and can thereby be used directly in the combustion chamber for measurement purposes. However, the high costs which occur from using such metals, in particular in the case of the use of several measurement sites, constitute a disadvantage here.
It has therefore already been proposed in GB-A-2 100 003 to make use for temperature measurement in aircraft turbines of combined thermocouple arrangements which operate on two staggered temperature levels and comprise a short high-temperature thermocouple, arranged between the two temperature levels and made from platinum/platinum-rhodium, for the first high temperature level, and a compensation thermocouple, which has a lower load bearing capacity and is made from alumel/chromel, for the second, lower temperature level. The actual temperature of the first temperature level can then be determined computationally from the measured data of the two thermocouples. However, the savings made on wire length for the high-temperature thermocouple are bought at the expense of a complicated design of the measurement probe and by the doubling of the number of measurements.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide a novel method and a measuring arrangement for measuring high hot gas temperatures such as occur in combustion chambers of gas turbines, which require little outlay, quickly deliver reliable results and are distinguished by simple and cost-effective design.
The object is achieved in the case of a method of the type mentioned in the beginning by virtue of the fact that a portion of the hot gases to be measured is mixed in a defined way with a cooler gas, that the temperature of the gas mixture is measured by means of the thermocouple, and that the temperature of the hot gases to be measured is determined from the measured temperature of the gas mixture. Mixing with a cooler gas produces a gas mixture with a reduced temperature which can be measured without a problem using a thermocouple which is less thermostable. Since the mixing is performed in a defined way, it is possible to calculate the original temperature of the hot gases backward without difficulty starting with the temperature of the gas mixture.
A preferred embodiment of the method according to the invention is defined in that mixing the gases is undertaken in a mixing space arranged inside the hot gas space and delimited therefrom, that the cooler gas from outside the hot gas space is injected at increased pressure into the mixing space, that gases from the hot gas space are added to the injected cooler gas and mixed therewith, and that for the purpose of measuring, the gas mixture produced is guided past the thermocouple arranged in the mixing space, and subsequently let up into the hot gas space. It is thereby possible to carry out the measurement in a very compact arrangement.
The measuring arrangement for carrying out the method is defined in that a mixing space extending transverse to the wall into the hot gas space and adjacent to the wall is separated by separating means inside the hot gas space, which is bounded by a wall, that at least one injection opening is provided through which the cooler gas can be introduced or injected from outside the hot gas space through the wall into the mixing space, that there is provided at the end, facing the wall, of the mixing space in the separating means at least one recirculation opening, through which the hot gas can enter the mixing space from the hot gas space, that at the end, averted from the wall, of the mixing space, the mixing space is connected to the hot gas space via an outlet, and that the thermocouple is arranged in the mixing space in the vicinity of the outlet.
A preferred embodiment of the measuring arrangement according to the invention is distinguished in that the separating means comprise an injection tube which, proceeding from the wall in a fashion concentric with an axis, projects into the hot gas space, that the thermocouple is arranged on the axis, that, distributed uniformly over the circumference of the injection tube, a multiplicity of recirculation openings orientated in the radial direction are arranged in the injection tube, and that, arranged uniformly on a circle, a multiplicity of injection openings orientated in the axial direction are provided in the part of the wall which is situated inside the injection tube. The result is a very good thorough mixing of the hot and cooler gases.
Further embodiments follow from the dependent claims.
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Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Gutierrez Diego
Pruchnic Jr. Stanley J.
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