Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Reexamination Certificate
1998-11-18
2001-05-08
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
C702S024000, C073S023310, C060S039270
Reexamination Certificate
active
06230103
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to gas turbine engines, such as those used in aircraft or in utility power plants. The invention provides an economical method of determining the concentration of a component of the exhaust gas of the engine, based on measurements taken at a single point probe, located well upstream of the exhaust stack, such as in one combustor of the engine.
A gas turbine engine, such as that used in an aircraft or a utility power plant, includes a compressor, a combustion section, and a turbine. Typically, the combustion section includes a plurality of separate combustors, arranged in a circle around a central axis so that the combustors act in parallel. The combustors are sometimes called “cans”, and the arrangement is referred to as can-annular.
In the design of turbine engines, an important criterion is the level of emissions of various combustion products, especially NOx and carbon monoxide (CO). When the structure of a combustor is proposed to be modified, it is necessary to know how much NOx and/or CO will be emitted by an engine built with combustors having the modified design.
While some properties of the modified combustor, such as its temperature, can be measured directly, measurement of emissions presents a problem. A gas turbine engine typically has many combustors, sometimes as many as eighteen or twenty. A change in only one combustor will have a very small effect on the emissions of the entire engine, and this change is not usually large enough to measure accurately when masked by the contributions of all the others. Thus, in the prior art, in order to determine the concentration of NOx and/or CO in the exhaust of a modified engine, it was considered necessary to build a prototype of the complete engine, including all of its combustors, and to take actual measurements of exhaust products at a location where the exhaust gases are considered well mixed and completely uniform. This procedure is time-consuming and expensive, because it requires that one build and install a full complement of duplicate copies of a redesigned combustor, without knowing beforehand how well the combustor will work.
The present invention solves the above-described problem, by providing a method of determining the concentration of an exhaust component of an engine, which method requires measurements to be taken at only one of the combustors of the engine. Therefore, the present invention eliminates the need to build multiple prototypes when developing a new combustor. The invention also provides a diagnostic method and apparatus for monitoring the performance of an engine, and for taking action when the performance of one of its combustors deteriorates.
SUMMARY OF THE INVENTION
In one embodiment, the method of the present invention begins with the step of providing a modified combustor for inclusion in a gas turbine engine having multiple combustors. One then operates the modified combustor, while measuring the concentration of an exhaust component of interest (such as NOx or CO), at a single and specified point in the modified combustor, and while also measuring the concentration of carbon dioxide (CO
2
), at the same point in the same combustor. The concentration of CO
2
in the exhaust of the entire engine is calculated from known principles, from a knowledge of engine air flow, fuel flow, and the hydrogen/carbon ratio in the fuel. Alternatively, the CO
2
concentration in the exhaust can be measured directly. From the foregoing quantities, one computes the concentration of the component of interest in the exhaust of the entire engine. The calculation can be expressed as:
X
exhaust
=(
X
sample
/CO2
sample
)×CO2
exhaust
where
X
exhaust
is the concentration, in the entire engine exhaust, of the component of interest;
X
sample
is the measured concentration, at one point in the modified combustor, of the component of interest;
CO2
sample
is the measured concentration of CO
2
, at one point in the modified combustor; and
CO2
exhaust
is the calculated or measured concentration of CO
2
at the exhaust outlet of the entire engine.
In a more general form, the method does not require redesign of a combustor, but can simply be used to determine the concentration of an exhaust component based on measurements taken at a single existing combustor. The invention can also be used to compare the performance of the various combustors in an engine. In another embodiment, the invention can be used to monitor the performance of the combustors of an engine, by making continuous calculations of concentrations of exhaust components, and by providing a visual or aural indication when an anomaly is detected.
The above-described method of determining concentration of exhaust components has been found to work well where the component of interest is NOx, but it can also be used to determine the emissions of CO and other components.
The invention also includes apparatus for performing the methods described above.
The present invention therefore has the primary object of providing a method of determining emissions of a gas turbine engine.
The invention has the further object of providing a method as described above, wherein measurements need be taken only at a single point in a single combustor.
The invention has the further object of simplifying the process of testing a newly-designed combustor.
The invention has the further object of substantially reducing the cost of testing a newly-designed combustor.
The invention has the further object of providing information which leads to the design of engines having reduced emissions of pollutants, with minimal cost.
The invention has the further object of providing method and apparatus for monitoring the performance of a gas turbine engine.
The invention has the further object of providing apparatus and methods for indicating an anomaly in emissions of a gas turbine engine.
The reader skilled in the art will recognize other objects and advantages of the present invention, from a reading of the following brief description of the drawings, the detailed description of the invention, and the appended claims.
REFERENCES:
patent: 5024055 (1991-06-01), Sato et al.
patent: 5257496 (1993-11-01), Brown et al.
Belokon Alexandr A.
Buriko Yuri Ya.
DeCorso Mario
Holden Paul C.
Moen David L.
Barbee Manuel L.
Eilberg William H.
Hoff Marc S.
Power Tech Associates, Inc.
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