Patent Description:
A gas turbine engine is a flow machine in which a pressurized high-temperature gas is expanded to produce mechanical work. The gas turbine includes a turbine or expander, a compressor positioned upstream of the turbine, and a combustion chamber between the compressor and turbine. The compressor section compresses air by way of the blading of one or more compressor stages. The compressed air subsequently mixes with a gaseous or liquid fuel in the combustion chamber, where the mixture is ignited to initiate combustion. The combustion results in a hot gas (a mixture composed of combustion gas products and residual components of air) which expands in the following turbine section, with thermal energy being converted into mechanical energy in the process to drive an axial shaft. The shaft is connected to and drives the compressor. The shaft also drives a generator, a propeller or other rotating loads. In the case of a jet power plant, the thermal energy also accelerates a hot gas exhaust stream, which generates the jet thrust. Flashback is a phenomenon that occurs in the combustion chambers of gas turbines when the flame front moves backward against the fuel/air flow and approaches or contacts a flame tube.

<CIT> discloses the detection of combustion anomalies within a gas turbine engine. <CIT> disclose a method for detecting a flashback condition in a fuel nozzle of a combustor in a gas turbine engine. <CIT> a method for monitoring and controlling a gas turbine. <CIT> discloses a gas turbine combustor vibration sensing system. <CIT> discloses a gas turbine control device. <CIT> discloses the monitoring of the state of a flame in a gas turbine engine cobustor.

A method of detecting combustor flashback in a gas turbine engine is provided in accordance with claim <NUM>.

In another construction, a method of detecting flashback in a gas turbine engine is provided in accordance with claim <NUM>.

The foregoing has outlined rather broadly the technical features of the present invention so that those skilled in the art may better understand the detailed description that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims. Those skilled in the art will appreciate that they may readily use the conception and the specific embodiments disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art will also realize that such equivalent constructions do not depart from the scope of the invention in its broadest form.

Also, before undertaking the Detailed Description below, it should be understood that various definitions for certain words and phrases are provided throughout this specification and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases. While some terms may include a wide variety of embodiments, the appended claims may expressly limit these terms to specific embodiments.

Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

Also, it should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms "including," "having," and "comprising," as well as derivatives thereof, mean inclusion without limitation. The singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term "or" is inclusive, meaning and/or, unless the context clearly indicates otherwise. The phrases "associated with" and "associated therewith," as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.

Also, although the terms "first", "second", "third" and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present invention.

In addition, the term "adjacent to" may mean: that an element is relatively near to but not in contact with a further element; or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise. Terms "about" or "substantially" or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard as available a variation of <NUM> percent would fall within the meaning of these terms unless otherwise stated.

<FIG> illustrates an example of a gas turbine engine <NUM> including a compressor section <NUM>, a combustion section <NUM>, and a turbine section <NUM>. The compressor section <NUM> includes a plurality of stages <NUM> with each stage including a set of rotating blades and a set of stationary or adjustable guide vanes. The compressor section <NUM> is in fluid communication with an inlet section to allow the engine <NUM> to draw atmospheric air into the compressor section <NUM>. During engine operation, the compressor section <NUM> operates to draw in atmospheric air and to compress that air for delivery to the combustion section.

In the illustrated construction, the combustion section <NUM> includes a plurality of separate combustors <NUM> that each operate to mix a flow of fuel with the compressed air from the compressor section <NUM> and to combust that air-fuel mixture to produce a flow of high temperature, high pressure combustion gases. Of course, many other combustion section arrangements are possible.

The turbine section <NUM> includes a plurality of stages <NUM> with each stage <NUM> including a number of rotating blades and a number of stationary blades or vanes. The stages <NUM> are arranged to receive the combustion gas from the combustion section <NUM> and expand that gas to convert thermal and pressure energy into rotating or mechanical work. The turbine section <NUM> is connected to the compressor section <NUM> to drive the compressor section <NUM>. For gas turbine engines <NUM> used for power generation or as prime movers, the turbine section <NUM> is also connected to a generator, pump, or other device to be driven. In the case of jet engines, the combustion gas is discharged from the engine to produce thrust.

A control system <NUM> is coupled to the gas turbine engine <NUM> and operates to monitor various operating parameters and to control various operations of the gas turbine engine <NUM>. In preferred constructions the control system <NUM> is micro-processor based and includes memory devices and data storage devices for collecting, analyzing and storing data. In addition, the control system <NUM> provides output data to various devices including monitors, printers, indicators, and the like that allow users to interface with the control system <NUM> to provide inputs or adjustments. In the example of a power generation system, a user may input a power output set point and the control system <NUM> adjusts the various control inputs to achieve that power output in an efficient manner.

The control system <NUM> can control various operating parameters including, but not limited to variable inlet guide vane positions, fuel flow rates and pressures, engine speed, and generator load. Of course, other applications may have fewer or more controllable devices. The control system <NUM> also monitors various parameters to assure that the gas turbine engine <NUM> is operating properly. Some parameters that are monitored may include inlet air temperature, compressor outlet temperature and pressure, combustor outlet temperature, turbine inlet temperature, fuel flow rate, generator power output, and the like. Many of these measurements are displayed for the user and are logged for later review should such a review be necessary.

<FIG> is an enlarged cross-sectional view of one of the combustors <NUM> of the gas turbine engine <NUM> of <FIG>. Each combustor <NUM> includes a top hat section <NUM>, at least one flame tube <NUM>, a combustor basket <NUM>, and a transition piece <NUM>. The top hat section <NUM> attaches to the engine <NUM> and supports any piping and valves necessary to direct fuel into the combustor <NUM>. The combustor basket <NUM> extends from the top hat section <NUM> toward the turbine section <NUM> and defines a long axis <NUM> that is arranged at an oblique angle with respect to a gas turbine engine central axis <NUM>. The combustor basket <NUM> operates as a liner to separate the combustion zone of the combustor <NUM> from the exterior walls of the engine <NUM>. At least one flame tube <NUM>, and in many cases multiple flame tubes <NUM> are disposed within the combustor basket <NUM>. The flame tubes <NUM> expel a flow of fuel and air that is ignited to form one or more flames <NUM> within the combustor basket <NUM>. During normal operation, the flame <NUM> defines a flame front <NUM> (shown in <FIG>) that is spaced a non-zero distance <NUM> from an outlet <NUM> of the flame tube <NUM>. The combustor basket <NUM> includes a plurality of apertures (not shown) that allow additional air into the combustion area to assure complete combustion and to cool the combustion gases before they are discharged to the turbine section <NUM>. The transition piece <NUM> is positioned adjacent the combustion baskets <NUM> to receive the combustion gases and direct them efficiently to the inlet of the turbine section <NUM>.

With reference to <FIG>, a first sensor <NUM> is positioned at an outlet end <NUM> of the combustor basket <NUM> and a second sensor <NUM> is positioned in the transition piece <NUM> downstream of the first sensor <NUM>. Thus, in the illustrated construction, the sensors <NUM>, <NUM> are downstream of the flame tube <NUM>. The sensors <NUM>, <NUM> are dynamic pressure sensors that are operable to detect small and rapid pressure changes associated with auditory changes within the combustor <NUM>. While two sensors <NUM>, <NUM> are illustrated, only one is required to detect the desired pressure fluctuations. In other constructions, these sensors <NUM>, <NUM> can be positioned in the top hat section <NUM> or in other areas of the combustor <NUM>. The actual position and quantity of sensors <NUM>, <NUM> required can vary with the design of the combustor <NUM> as small design changes can have a large effect on the acoustic environment.

Other sensors, such as acoustic sensors, low frequency pressure sensors, temperature sensors, optical sensors, or ionization sensors, alone or in some combination can be configured to detect physical phenomena in at least a portion of the gas flow. In some embodiments, there are multiple actuators or sensors or both, collectively called transducers. In some embodiments, either or both of one or more actuators and sensors are acoustic transceivers that are acoustic transducers that can both emit and detect acoustic signals.

The dynamic pressure sensors <NUM>, <NUM> receive acoustic oscillations generated within the combustor <NUM>, including those generated by the flame <NUM> and convert those oscillations into signals that can be analyzed by a processor. The status of the flame <NUM> can be reliably detected and monitored by combining information about the locations of the sensors <NUM>, <NUM> and the flame <NUM> with the spectral content contained in the sensor signals. In various embodiments described herein, information about the position of the flame front <NUM> is also determined based on the spectral content of the signals received from either or both the dynamic pressure sensors <NUM>, <NUM>. The dynamic pressure sensors <NUM>, <NUM> are arranged at two different locations in the pressure influence zone of the combustor <NUM> in the gas turbine engine <NUM>. What is understood by pressure influence zone in this context is an area where pressure fluctuations are dependent to a large extent on the dynamics of the flame <NUM> of the respective combustor <NUM>. In the case of a gas turbine engine <NUM> of the can-annular type this can be for example an area within the respective basket <NUM> of the combustor <NUM>. In other embodiments, different acoustic transducers in the same or different one or more locations sensitive to acoustic phenomena in the combustor basket <NUM> are used. In some constructions, the pressure sensors <NUM>, <NUM> are positioned upstream from the flame <NUM>. This location is colder than the sensor location shown in <FIG>. However, <FIG> is provided to explain how flame monitoring with sensors <NUM>, <NUM> is done to aid in identifying the problematic phenomena, including flashback in or adjacent to the flame tube <NUM>.

Thus, there are dynamic pressure sensors <NUM>, <NUM> mounted on each basket <NUM> in a can-annular combustor system or a few in the annulus in the case of an annular chamber. From the results obtained by advanced data acquisition systems, these sensors <NUM>, <NUM> are sensitive enough to pick up the sound created by events such as a flashback event.

The dynamic pressure sensors <NUM>, <NUM> are used as part of a flashback detection system that is implemented as part of the control system <NUM> or is a stand-alone monitoring system. During normal operation of the gas turbine engine <NUM>, flames <NUM> are supported a non-zero distance <NUM> from each of the flame tubes <NUM> (shown in <FIG>). The base of the flame <NUM> or the flame front <NUM> tends to move in response to varying operating conditions (e.g., fuel pressure, fuel flow, air pressure, air volume, temperature, etc.). Under certain conditions, the flame front <NUM> can get very close to the flame tube outlet <NUM> or even move into the flame tube <NUM>. This condition is referred to as flashback and can cause rapid and significant damage to the flame tube <NUM> and other turbine engine components. The flashback detection system monitors the dynamic pressure sensors <NUM>, <NUM> for a characteristic signal indicative of a flashback event. Often, the characteristic that indicates a flashback event is an increase in amplitude in a particular frequency range.

With reference to <FIG>, the flame tubes <NUM> are annular tube members that during normal operation vibrate due to the flow passing through them. The flame front <NUM> for each flame tube <NUM> cooperates with its corresponding flame tube <NUM> to define a characteristic length. The characteristic length establishes the frequencies at which the individual flame tube <NUM> vibrates. At the initiation of a flashback event, the flame front <NUM> moves closer to the flame tube <NUM>. This shortens the characteristic length and increases the amplitude and frequency of the vibrations produced by the flame tube <NUM>.

<FIG> illustrates a series of charts including a spectrogram <NUM> generated by the dynamic pressure sensors <NUM>, <NUM> and showing the frequency ranges in which the flame tubes <NUM> vibrate. During the flashback event, the dynamic pressure sensors <NUM>, <NUM> detect the increased amplitude <NUM> immediately. In addition, as the flame front <NUM> approaches the outlet <NUM> of the flame tube <NUM> it shortens the characteristic length which increases the vibration frequency. This immediately appears as a higher amplitude line <NUM> that increases in frequency with time.

Prior art detection systems relied on thermocouples to detect increases in temperatures. <FIG> also illustrates a thermocouple plot <NUM> of the same flashback event illustrated in the spectrogram <NUM>. The dynamic pressure sensors <NUM>, <NUM> detect the flashback event almost instantaneously. However, the thermocouple system requires some time to heat the thermocouple. In addition, a deadband or tolerance is provided for the thermocouple system to inhibit unwanted false positive detections. Thus, the dynamic pressure sensor system detects and reacts to a flashback event before the thermocouple system detects the event. Detecting the flashback early can provide an operator or control system time to reduce the fuel flow to the combustor <NUM> or to shutdown the gas turbine engine <NUM> to reduce the likelihood of damage.

In engines <NUM> with combustor baskets <NUM> that include multiple flame tubes <NUM>, two or more dynamic pressure sensors <NUM>, <NUM> can be used simultaneously to identify the specific flame tube <NUM> that is experiencing the flashback event. With the sensors <NUM>, <NUM> spaced apart, a triangulation method or other known methods can be used to identify the location of the vibration event. The flame tube <NUM> that experiences the event can than be identified for future inspection, maintenance, or replacement.

In another construction, vibration sensors <NUM> are coupled to the individual combustor baskets <NUM> to detect vibration of the baskets <NUM>. During operation of the engine <NUM>, each of the individual baskets <NUM> tends to vibrate within the same range of frequencies. <FIG> includes another spectrogram illustrating the data generated by the vibration sensors <NUM> during normal operation. However, during a flashback event there is often an increased amplitude of the vibration within a particular frequency range of the combustor basket <NUM> in which the flashback event occurs, as illustrated in the spectrogram <NUM> of <FIG>. The control system <NUM> compares the vibration levels of all the combustor baskets <NUM> simultaneously and identifies which combustor basket <NUM> is generating the anomalous vibrations. The events are logged as possible flashback events to allow for future inspection, maintenance, or replacement.

<FIG> illustrates the vibration data in a different format. In <FIG>, the vibration levels within the particular frequency range for each sensor <NUM> on multiple baskets are plotted versus time. A spike or sudden large increase of the vibration level from one vibration sensor <NUM> installed on one basket <NUM> with respect to the normal vibration level from sensors <NUM> installed on other baskets <NUM> is indicative of an event such as a flashback event on the basket <NUM> experiencing the spike. <FIG> also illustrates the reaction of a temperature-based flashback detection system under the same operating conditions. As with the dynamic pressure sensor system, the vibration sensors <NUM> react more quickly to the flashback event than does the temperature-based system.

In some embodiments, the spectrograms <NUM>, <NUM> are presented to a user on a display, such as a display device of a computer system to allow for continuous and real time monitoring of the engine <NUM>. In addition, the data is capable of automated analysis which allows for automated alarming or logging of events that appear to be flashback events.

While much of the disclosure discusses monitoring two combustor baskets, it should be clear that the flashback detection system is capable of monitoring any number of combustor baskets simultaneously.

Although an exemplary embodiment of the present invention has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the scope of the invention in its broadest form.

Claim 1:
A method of detecting combustor flashback in a gas turbine engine (<NUM>), the method comprising:
positioning a dynamic pressure sensor (<NUM>) within a combustion section (<NUM>) having a flame tube (<NUM>); providing a flow of fuel to the gas turbine engine (<NUM>);
operating the gas turbine engine (<NUM>) to establish a flame (<NUM>) having a flame front (<NUM>) spaced a non-zero distance (<NUM>) from an outlet (<NUM>) of the flame tube (<NUM>);
detecting pressure changes adjacent the flame tube (<NUM>) to produce pressure signals;
monitoring a characteristic of the signals provided by the dynamic pressure sensor (<NUM>);
detecting a flashback signature within the signals provided by the dynamic pressure sensor (<NUM>); and
varying the fuel flow in response to the detection of the flashback signature,
wherein the combustion section (<NUM>) includes a plurality of separate combustor baskets (<NUM>) and wherein the dynamic pressure sensor (<NUM>) is positioned to detect pressure changes within a first of the combustor baskets (<NUM>),
wherein the flame tube (<NUM>) is positioned within the first combustor basket (<NUM>), and wherein each combustor basket (<NUM>) includes at least one flame tube (<NUM>),
wherein the method further comprises the steps of:
positioning a vibration sensor (<NUM>) adjacent each of the plurality of combustor baskets (<NUM>), each vibration sensor (<NUM>) measuring vibrations of its respective combustor basket (<NUM>) and generating signals indicative of those measured vibrations and
comparing the measured vibrations between the vibration sensors (<NUM>) and identifying a measured vibration from one vibration sensor (<NUM>) that is not present in the other measured vibrations.