Method for operating combustion system, combustion system and gas turbine engine comprising such combustion system

Abstract

A method is disclosed that enables a combustion system having at least two combustion zones arranged in series to operate on fuel, typically producing a varying flame velocity. First, an operating parameter of the gas turbine engine is determined (110). Control parameters of a control device configured to distribute a total fuel mass flow to the respective combustion zones are determined as a function of the gas turbine engine operating parameters (120). Information about the fuel composition is determined, in particular a relative portion of at least one combustible substance having a higher flame velocity than the first combustible substance is quantified (130). Control parameters (140) for the control means (23) can be adjusted depending on the information about the fuel composition. The control parameter is transmitted as a control signal to a control device (150).

Description

Technical Field

[0001] The present disclosure is directed to the subject matter set forth in the claims. Background Art

[0002] In the context of reducing net carbon dioxide emissions in power generation, the combustion of gases produced by the synthesis of hydrogen and hydrocarbon substances containing hydrogen and / or having two or more carbon atoms in the fuel molecule (so-called C2+ hydrocarbons) is increasingly discussed. In some aspects, the combined combustion of natural gas and hydrogen and / or combustibles containing different portions of C2+ substances may be ideal. As an advantage, such combined combustion increases the flexibility of operations adapted to the availability of the corresponding fuels. Preferably, the combustion system (which can be a combustion system of a gas turbine engine in an embodiment) should be able to operate a fuel composition that contains natural gas and different portions of C2+ substances or hydrogen in an embodiment or a mixture of hydrogen and C2+ substances in other embodiments. It should be understood that in other embodiments, operations performed on 100% natural gas or 100% hydrogen, 100% C2+ substances or 100% hydrogen and a mixture of C2+ substances should be included in the operating range.

[0003] Natural gas is generally understood as a gaseous combustible found on Earth as a fossil fuel and mainly comprising methane and a smaller portion of other hydrocarbons and a smaller portion of a variety of non-hydrocarbon gases, which may include nitrogen, carbon dioxide, carbon monoxide and others. Typically, at 1013.25 hPa and 15 ° C, the methane content is 85% or more by volume. In other examples, the methane content in the natural gas may be 90% or more by volume or 95% or more by volume. In other examples, methane may account for 85% (by volume) or more, 90% (by volume) or more, or 95% (by volume) or more of the total hydrocarbon content, wherein all these volume shares are mentioned at 1013.25 hPa and 15 ° C.

[0004] Hydrogen and / or C2+ species produce flame speeds and ignitabilities that are higher than the flame speed and ignitability of natural gas. Therefore, one problem with burning hydrogen and / or C2+ species in a combustion zone designed to operate on natural gas is the potential for combustion flashback. In other words, a problem with burning natural gas in a combustion zone designed to operate on hydrogen and / or C2+ species can be flame extinction.

[0005] The problem when burning fuel compositions comprising natural gas and different proportions of C2+ substances or one of hydrogen in embodiments or a mixture of hydrogen and C2+ substances in other embodiments in the same combustion system can therefore be broadly considered to include the problem of burning fuels with different flame speeds, while avoiding flame extinction when burning fuels with a relatively high proportion of or consisting of combustible substances with a lower flame speed, and avoiding flashback when burning fuels with a relatively high proportion of or consisting of combustible substances with a higher flame speed.

[0006] Flashback is a problem that becomes more severe the higher the temperature of the combustion fluid in which the fuel is combusted. Therefore, when combusting a fuel containing a component with a relatively high flame temperature, flashback needs to be addressed, for example in a staged combustion system in which a still oxygen-rich fluid containing combustion products at high temperature from an upstream combustion zone is supplied to a downstream combustion zone. Such a combustion system is known for a typical example in a gas turbine engine, in which the fluid flowing out of an upstream combustion stage may or may not be partially expanded before being supplied to a downstream combustion zone.

[0007] US 7,216,486 B2 discloses several proposals for solving the problem when burning natural gas that can be mixed with different shares of C2+ substances. One of the methods proposed is to change the fuel mass flow distribution to increase the relative fuel flow portion of the upstream combustion stage and reduce the relative fuel flow portion of the downstream combustion stage. It is assumed that the flashback risk is reduced due to the leaner mixture in the downstream combustion zone. However, it is obvious that if the total fuel mass flow remains constant, the temperature of the combustion fluid supplied to the downstream combustion zone increases, which in turn can increase the flashback tendency. Therefore, US 7,216,486 B2 also proposes to reduce the total fuel mass flow and thus unload the gas turbine engine if the share of C2+ substances exceeds a certain threshold, or to shut down the system completely.

[0008] Overview of the Disclosed Subject Matter

[0009] An object of the present disclosure is to provide the subject matter mentioned initially. More specifically, a method for operating a combustion system will be provided. The method will avoid the disadvantages in the art in various aspects, and more specifically, avoid the disadvantages in the art mentioned above. In a further aspect, the method will be suitable for enabling the combustion system to be operated using a fuel containing a combustible material with different proportions, and the combustible material of the different proportions has different flame speeds. In a more specific aspect, the method will be suitable for enabling the combustion system to operate on a fuel, wherein the combustible material includes 100% of a combustible material with a relatively low flame speed, 100% of a combustible material with a relatively high flame speed, or any mixture of combustible materials with relatively low and relatively high flame speeds. Based on the change in the composition of the combustible material, the operation of the fuel with combustible materials of different compositions is achieved without reducing the thermal power of the combustion system or the useful power output of the gas turbine engine, wherein the combustion system is operated in the proposed method.

[0010] In another aspect, a combustion system configured to perform the method proposed herein will be disclosed. In yet another aspect, a gas turbine engine to which the method proposed herein can be applied will be disclosed.

[0011] This is achieved by the subject matter recited in claim 1 and in further dependent claims. Further effects and advantages of the disclosed subject matter, whether explicitly mentioned or not, will become apparent from the disclosure provided below.

[0012] Therefore, a method for operating a combustion system is disclosed. The method includes providing a combustion fluid flow to the combustion system, causing the combustion fluid flow to flow through the combustion system in a direction from upstream to downstream, discharging a fuel flow into the combustion system, and causing the fuel flow to burn with at least a certain portion of the combustion fluid flow. In this regard, the method includes generating a combustion gas flow and discharging the combustion gas flow at the downstream end of the combustion system. Discharging the fuel flow into the combustion system includes allocating a first fuel mass flow portion of the total fuel mass flow to a first combustion zone of the combustion system located relatively upstream and providing at least a second fuel mass flow portion of the total fuel mass flow to at least one second combustion zone located relatively downstream of the first combustion zone. The fuel flow includes a fuel having a fuel composition, the fuel composition including a first relative portion of the fuel composition and at least a second relative portion of the fuel composition, the first relative portion of the fuel composition consisting of a first combustible substance having a first flame speed when burned in the combustion fluid, and the at least a second relative portion of the fuel composition consisting of at least one second combustible substance having a second flame speed when burned in the combustion fluid, wherein the second flame speed is greater than the first flame speed. It should be understood that the relative share of a substance can particularly refer to one of the mass share and volume share of the substance, which is a share of the total fuel composition. The method further includes quantifying at least one of the first relative share of the fuel composition and the second relative share of the fuel composition. It should be understood that the second relative share can be determined directly, but in an embodiment, it can also be indirectly derived from the relative share of other substances of the measured fuel composition (e.g., the first relative share, i.e., the relative share of the first combustible substance). It should be understood hereinafter that the change of the second relative share of the fuel composition can also be expressed as the change of the first relative share of the fuel composition, and its algebraic sign is opposite. The method further includes, at least within the range between the two values ​​of at least one of the first relative share of the fuel composition and at least one second relative share of the fuel composition, controlling the distribution of the fuel to the first fuel mass flow share of the total fuel mass flow, so that the first fuel mass flow share of the total fuel mass flow (i.e., the share allocated to the first combustion zone relatively upstream) decreases with the increase of the second relative share of the fuel composition, and the first fuel mass flow share of the total fuel mass flow increases with the decrease of the second relative share of the fuel composition.

[0013] A person skilled in the art will appreciate that the allocation can also be controlled based on other operating parameters, such as, but not limited to, the total fuel mass flow provided to the combustion system or the useful power output of the gas turbine engine in which the combustion system is integrated. Controlling the allocation of fuel to the first fuel mass flow share is controlled based on the fuel composition (e.g., the fraction of at least one combustible substance), independently of and in addition to the control based on other operating parameters. The control actions described herein can be performed if the other operating parameters (e.g., the thermal power of the combustion system or the useful power output of the gas turbine engine) do not change or remain constant, respectively.

[0014] "First" and "second" should not be interpreted as being limited to only two of the corresponding features that exist. For example, the first combustion zone and the second combustion zone are not necessarily the most upstream combustion zone and the most downstream combustion zone in the combustion system, and it is not excluded that there are additional combustion zones interposed between the named first combustion zone and the second combustion zone.

[0015] The combustion fluid may be any fluid in which a fuel may be burned or with which a fuel may be mixed for combustion. Typically, but not limiting, the combustion fluid may include or consist of air or another gaseous fluid containing oxygen and / or air or another gaseous fluid containing oxygen mixed with steam and / or combustion products from a relatively upstream combustion zone.

[0016] When a certain portion of the total fuel mass flow rate fuel is transferred from a relatively upstream combustion zone to a relatively downstream combustion zone, the temperature of the fluid entering the relatively downstream combustion zone is reduced, thereby reducing the risk of flashback in the relatively downstream combustion zone. This may generally be the case, and in particular, if the temperature of the combustion fluid entering the relatively upstream combustion zone is significantly lower than the temperature of the combustion fluid at the inlet of the relatively downstream combustion zone, the overall risk of flashback in the combustion system can be significantly reduced (if it cannot be avoided). For specific cases, the relatively upstream combustion zone can receive air from a fan or from a compressor (such as a compressor of a gas turbine engine), while the relatively downstream combustion zone receives a mixture of combustion products and residual air from the combustion zone upstream thereof.

[0017] It should be noted that within the framework of the present disclosure, the use of the indefinite article "a" or "an" in no way specifies singularity, nor does it exclude the presence of a plurality of the named components or features. Therefore, it should be read in the sense of "at least one" or "one or more".

[0018] The flame speed of a combustible material is defined as the speed at which the flame front travels relative to the unburned gas mixture. In a combustion system of the type disclosed herein, the rate of the unburned mixture of the combustion fluid and the fuel is designed to keep the flame front stationary and within a permissible distance range relative to the upstream burner wall and / or internal fixtures. If the flame speed increases relative to the convection rate of the unburned mixture of the combustion fluid and the fuel, the flame front may be established too close to the upstream burner wall and / or internal fixtures, and cause overheating and damage to the components of the combustion system. The flame speed of a combustible material is determined by methods known to those skilled in the art. In order to compare the flame speed of the material used herein, it should be understood that those flame speeds are flame speeds determined under the same equal reference conditions (i.e., under the same temperature, pressure, and equivalence ratio) of two combustible materials. The reference conditions referred to by the flame speed can be selected within the range of conditions representing the combustion system. Below, specific examples of a first combustible substance and a second combustible substance are provided such that, for a non-limiting example, methane is the first combustible substance having a relatively low flame speed, and hydrogen or at least one C2+ hydrocarbon or C2+ alkane or a mixture thereof is at least one combustible substance having a relatively high flame speed.

[0019] In an embodiment, the method includes online monitoring of fuel composition, including at least the ratio of the second relative fraction of the fuel composition to the first relative fraction of the fuel composition and / or the quantification of the second fraction of the fuel composition. An example of a method for determining fuel composition online and in real time is disclosed in DE 103 02 487A1, as it can be applied in this article. This embodiment of the method disclosed herein provides accurate and dynamic regulation of the fuel distribution to a relatively upstream combustion zone and at least one relatively downstream combustion zone. In other embodiments, two fuel streams including different portions of the first combustible material and at least one second combustible material can be mixed with each other through a separate supply line before being discharged into the combustion system, wherein each of the supply lines has a regulating valve for controlling the flow of the corresponding fuel. In such cases, the first relative portion and the second relative portion of the resulting fuel composition can be determined by the corresponding valve stroke, and can be corrected, for example, by the temperature and pressure of the corresponding fuel stream upstream of the corresponding control valve.

[0020] As described above, natural gas may contain different compositions. Thus, in embodiments, the fuel composition may be characterized by the share of methane and the share of a second combustible substance in the fuel. That is, in embodiments, the first combustible substance is methane. In other embodiments, as a non-limiting example, the natural gas may be characterized as additional hydrogen and / or C2+ substances before being mixed with the second combustible substance, and then further characterization of the mixed fuel will allow the share of the natural gas and the added second combustible substance to be quantified. In this article, "characterization" of a fluid may be broadly understood as the determination of the substances contained in the fluid.

[0021] In a more specific aspect, the at least one second combustible substance may consist of at least one of hydrogen and / or at least one C2+ hydrocarbon or a mixture thereof. That is, the characterization of the fuel composition will include the determination of the share of hydrogen and / or C2+ substances, which, as described above, can be determined by direct measurement, derived from the quantification of the other substances.

[0022] In another, more specific but non-limiting example, it can be provided that the combustion fluid flow and the combustion product flow flowing out of the first combustion zone are at least partially expanded before entering the second combustion zone. The expansion can be performed, for example, in a high-pressure expansion turbine, which includes at least one expansion turbine stage fluidly interposed between the first and second combustion zones. For example, a gas turbine engine having a high-pressure expansion turbine fluidly interposed between the first combustion zone and the second combustion zone is disclosed in EP 620 362 and EP 740 057. In the cited document, the combustion product flow and the combustion fluid flow flowing out of the first combustion zone are only partially expanded before entering the second combustion zone, and are further expanded in the low-pressure expansion turbine downstream of the second combustion zone. The at least one interposed high-pressure expansion turbine can therefore be referred to as a pre-expansion turbine. As described above, the gas flow flowing out of the second combustion zone is discharged into an expansion turbine or at least one expansion turbine stage arranged downstream of the second combustion zone, respectively. The expansion turbine may be a low pressure expansion turbine as defined in, for example, EP 620 362 and EP 740 057. In an embodiment, the high pressure expansion turbine and a low pressure expansion turbine arranged downstream of the second combustion zone may both provide power to a common shaft.

[0023] Insofar as the combustion system is arranged in a gas turbine engine, the gas turbine engine may include at least one row of variable inlet guide vanes at the upstream end of the compressor. The vanes are provided with a variable angle or pitch relative to the flow direction (and in an embodiment, the axial direction of the compressor) and are used to adjust or selectively increase or decrease the volume of the fluid flow entering the compressor, and thus adjust or selectively increase or decrease the volume of the combustion fluid flow according to the present disclosure. Then, the method may include, at least within a second range between two values ​​of at least one of the first relative fraction of the fuel composition and at least one of the at least one second relative fraction of the fuel composition, controlling the vane angle of at least one row of variable inlet guide vanes to increase the mass flow of the combustion fluid as the second relative fraction of the fuel composition increases, and controlling the vane angle of at least one row of variable inlet guide vanes to reduce the mass flow of the combustion fluid as the second relative fraction of the fuel composition decreases. The second range between the two values ​​of the first relative fraction of the fuel composition and at least one of the at least one second relative fraction of the fuel composition may be within the above-mentioned range defined between the two values ​​of the first relative fraction of the fuel composition and at least one of the at least one second relative fraction of the fuel composition, overlap with the above-mentioned range, or be completely different. In an embodiment, the control of at least one variable inlet guide vane row may become effective when the second relative share of the second combustible material having a relatively high flame speed is above a threshold value. The threshold value may be defined according to operating parameters of the combustion system or the gas turbine engine in which the combustion system operates, such as the initial position of at least one variable inlet guide row, the total fuel mass flow, the heat load, the relative load of the gas turbine engine, etc. The parameters may be used alone or in combination with other parameters. Increasing the flow of the combustion fluid while maintaining or only not significantly changing the total fuel mass flow, reducing the equivalence ratio in the combustion zone and the temperature of the combustion fluid received by the second combustion zone, while increasing the convection rate inside the combustion zone, and thus reducing the risk of flashback in both combustion zones.

[0024] A combustion system configured to perform the above method is further disclosed. The combustion system includes at least one combustion flow path and a fuel supply system for causing a combustion fluid to flow therethrough. The combustion flow path has an upstream end and a downstream end. At least one combustion flow path further includes a first combustion zone located relatively upstream and located inside the at least one combustion flow path, and at least one second combustion zone located relatively downstream and located inside the at least one combustion flow path. At least one second combustion zone is located downstream of the first combustion zone and is configured to receive a fluid flow flowing out of a combustion zone located upstream of the second combustion zone (e.g., from the first combustion zone). The first combustion zone is provided with a first fuel discharge device for discharging fuel from the fuel supply system into the combustion flow path and into the first combustion zone, and at least one second combustion zone is provided with a second fuel discharge device for discharging fuel from the fuel supply system into the combustion flow path and into the second combustion zone. That is, for clarity, each second combustion zone may be provided with a corresponding second fuel discharge device. The fuel supply system is configured to provide fuel from a fuel supply source to the first combustion zone through a first fuel discharge device, and to at least one second combustion zone through a corresponding second fuel discharge device. The fuel supply source may be a common fuel supply source for two combustion zones. The fuel supply system includes a control device for allocating a first fuel mass flow rate share of the total fuel mass flow rate to the first combustion zone. In certain cases, the control device may include at least one valve or multiple valves arranged to perform the function. Such valve arrangements are basically known to those skilled in the art. The system further includes a control system adapted and configured to receive information about the fuel composition, the information including quantitative information about the relative share of at least one combustible substance. As described above, this may be quantitative information about the relative share of at least one second combustible substance, but may also be or include information about the relative share of other substances of the fuel, from which the relative share of at least one second combustible substance may be derived. The information about the fuel composition may be provided intermittently, for example as a result of repeated off-line analysis of the fuel. In other embodiments, as will be described in more detail below, information about the fuel composition may be provided from an online measurement system. In yet other embodiments, the information may be derived from the valve stroke of a valve for metering different fuel components to be mixed to form a blended fuel provided by the fuel supply system. As mentioned above, the relative share values ​​derived from the valve stroke information may be further corrected by pressure and temperature readings from corresponding sensors, which may in particular be arranged inside the fuel line and upstream of the valve, for metering the different fuel components.The control device is further suitable for and configured to control a control device for allocating a first fuel mass flow share of the total fuel mass flow to the first combustion zone, so that at least within the range between two values ​​of the first relative share of the fuel composition and at least one second relative share of the fuel composition, the first fuel mass flow share of the total fuel mass flow allocated to the first combustion zone decreases as the second relative share of the fuel composition increases, and the first fuel mass flow share of the total fuel mass flow allocated to the first combustion zone increases as the second relative share of the fuel composition decreases.

[0025] As described above, in an embodiment of a combustion system, a measuring device suitable for online characterization of the composition of the fuel supplied to at least one combustion flow path is operatively connected to the fuel supply system and configured to quantify the share of at least one substance (in a specific embodiment, the share of at least one combustible substance) in the fuel composition provided by the fuel supply system. The measuring device is operatively connected to a control device so as to provide quantitative information about the share of at least one combustible substance in the fuel composition to the control device. In an embodiment, the measuring device can be configured to directly quantify at least one relative share of at least one second combustible substance. In other embodiments, the at least one relative share of at least one second combustible substance can be deducted from the relative share of other substances.

[0026] The combustion system as suggested may further be configured with a high pressure expansion turbine having at least one expansion turbine stage fluidly interposed between the first combustion zone and the second combustion zone.

[0027] The first combustion zone and the second combustion zone can be arranged in a common combustion space, which can also be referred to as a combustion chamber or burner. Such an arrangement is known, for example, from the so-called late lean combustion technology.

[0028] Yet further disclosed is a gas turbine engine comprising a compressor, an expansion turbine and a combustion system of the above type, wherein the combustion system is arranged and configured to receive a combustion fluid from the compressor and discharge the fluid from the combustion system to the expansion turbine. In an embodiment thereof, at least one high-pressure expansion turbine comprising at least one expansion turbine stage may be fluidly interposed between a first combustion zone and a second combustion zone, while at least one low-pressure combustion turbine is arranged downstream of the second combustion zone, as generally suggested, for example, in EP 620 362 and EP 740 057.

[0029] It should be understood that the features and embodiments disclosed above may be combined with each other.It should be further understood that additional embodiments are conceivable within the scope of the disclosed and claimed subject matter, which will be apparent to the skilled person in light of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The subject matter of the present disclosure will now be explained in more detail with the aid of selected exemplary embodiments illustrated in the accompanying drawings.

[0031] Figure 1 is a first exemplary embodiment of a gas turbine engine equipped with a combustion system according to the present teachings and adapted for performing a method according to the present teachings;

[0032] Figure 2 is a block diagram outlining an embodiment of a method according to the present teachings;

[0033] Figure 3 is a second exemplary embodiment of a gas turbine engine equipped with a combustion system according to the present teachings and adapted for performing a method according to the present teachings;

[0034] Figure 4 is a third exemplary embodiment of a gas turbine engine equipped with a combustion system according to the present teachings and adapted for performing a method according to the present teachings;

[0035] It should be understood that the drawings are highly schematic and that details not necessary for illustrative purposes may be omitted for ease of understanding and depiction. It should be further understood that the drawings show only selected illustrative embodiments and that embodiments not shown may still be fully within the scope of the subject matter disclosed and / or claimed herein.

[0036] Exemplary Modes of Implementing the Teachings of the Present Disclosure

[0037] Figure 1A first exemplary embodiment of an arrangement for implementing the teachings of the present disclosure is outlined. A gas turbine engine 1 comprises a compressor 11 and an expansion turbine 12 arranged on a common shaft 13. In a manner fully known to a person skilled in the art, the expansion turbine 12 is intended to drive the compressor 11 and, for example, to provide useful power to a generator 14, which is drivingly connected to the shaft 13 so as to be driven by the gas turbine engine. The compressor 11 is equipped with at least one row of adjustable inlet guide vanes 111, also referred to as variable inlet guide vanes or VIGVs. The gas turbine engine 1 further comprises a combustion system, which in turn comprises two combustion zones 15 and 16. The combustion zones 15 and 16 may or may not be arranged inside a common combustion chamber. A combustion chamber comprising two combustion zones connected in series with fluid is known, for example, from the so-called late lean combustion technology. The two combustion zones may be supplied with fuel to be burned independently of each other, the fuel to be burned being the combustion fluid in the combustion zones. The compressor 11 compresses ambient air in a manner known per se and provides the compressed ambient air to the combustion system as the combustion fluid. A first portion of the total fuel mass flow rate can be discharged into the combustion system at a relatively upstream combustion zone 15 and burned therein. Thus, a mixture of combustion products and residual air flows to a relatively downstream second combustion zone 16, in which a second portion of the total fuel mass flow rate is discharged into the combustion system. This second portion of the total fuel mass flow rate is ignited and burned in the hot mixture of residual air and combustion gases flowing out of the first relatively upstream combustion zone 15. The flow of residual air and combustion products flowing out of the relatively downstream second combustion zone 16 expands in the expansion turbine 12, and thereby generates mechanical power to drive the compressor 11, and further provides useful power.

[0038] Combustion systems which comprise a plurality of combustion zones arranged in series along the flow direction of the combustion fluid are known from the prior art and serve, for example, to reduce the formation of undesirable pollutants.

[0039] In a specific example, a first fuel supply stream 203 having a first fuel composition and a second fuel supply stream 204 having a second fuel composition are provided to a gas turbine engine fuel supply system and a fuel blend or mixture 205 is formed. The fuel supplied as the first fuel supply stream 203 may, for example, be composed of natural gas, and the fuel supplied as the second fuel supply stream 204 may, for example, be or contain hydrogen and / or C2+ substances, and produce a higher flame speed than the fuel supplied as the first fuel supply stream 203. In general, the mixed fuel 205 may include at least two combustible substances with different flame speeds, and such a composition may vary depending on the relative mass flow of the fuel supplied as the first fuel supply stream 203 and the fuel supplied as the second fuel supply stream 204 and / or the composition of the fuel supplied therein. Therefore, the flame speed of the mixed fuel 205 may vary. Therefore, the fuel blend 205 may include a first combustible substance having a relatively low first flame speed. The first combustible substance may typically be methane, which is the main component of the natural gas provided as the first fuel supply stream 203. In addition, the fuel blend 205 may include a second combustible substance having a relatively high second flame speed. The second combustible substance includes at least one of hydrogen and / or C2+ hydrocarbons or alkanes. The relative share of the first combustible substance and the second combustible substance in the total combustible share of the fuel blend 205 may vary from 0% to 100% in some cases. The main regulating valve 21 is configured to control the total fuel mass flow 206 provided to the combustion system so that the useful power output meets the set value, which can be represented by the electric power output from the generator 14, for example. The control valves 22 and 23 control the distribution of fuel to the first fuel mass flow share 201 to be burned in the first combustion zone 15 relatively upstream and the second fuel mass flow share 202 to be burned in the second combustion zone 16 relatively downstream. In this embodiment, one of the control valves 22 and 23 or the main regulating valve 21 can be omitted, wherein, in the case of omitting the main regulating valve, the control valves 22 and 23 will need to be configured to jointly control the total fuel mass flow provided to the combustion system so that the useful power output meets the set value. In a manner known to those skilled in the art, the distribution of fuel to the combustion zone is controlled according to certain operating parameters of the gas turbine engine 1. However, when the relative share of the combustible material in the fuel blend changes, the flame speed of the fuel burning in the combustion zone changes. In addition, the combustion temperature can change. The increased flame speed of the fuel blend combined with the increased temperature of the fluid that potentially flows out of the relatively upstream first combustion zone 15 and flows as a combustion fluid to the relatively downstream second combustion zone 16 can significantly increase the tendency of flashback in the second combustion zone 16.It has been found that the flashback risk associated with the increased flame speed of the fuel can be mitigated even if the operating parameters of the gas turbine engine are otherwise unchanged when reducing the first relative fuel mass flow rate share 201 provided to the relatively upstream combustion zone 15 relative to the total fuel mass flow rate 206. It goes without saying that in the present embodiment with two combustion zones, the increase of the second fuel mass flow rate share 202 relative to the total fuel mass flow rate 206 is accompanied by a decrease of the first relative fuel mass flow rate share 201 relative to the total fuel mass flow rate 206.

[0040] The above method requires some quantitative information about the composition of the combustibles in the fuel blend 205. Therefore, in the illustrated embodiment, a measuring device 31 suitable for online characterization of the composition of the fuel is arranged in a fuel supply line through which the fuel blend 205 flows. The measuring device is configured to quantify the relative share of at least one combustible substance in the fuel blend 205. Useful information about the composition of the fuel is provided to the control device 32, which information at least allows qualitative inferences about the flame speed to be obtained. The control device 32 can be part of a control system of a power station or a gas turbine engine in particular. In one case, the information can include the relative share of the second combustible substance relative to, for example, the total fuel composition or the content of the first combustible substance. The control device 32 then provides control signals to the control valves 22 and 23 in order to change the fuel distribution to different combustion zones. In addition, the control device 32 can provide control signals to the variable inlet guide vanes 111 in order to control the variable inlet guide vanes 111 according to the relative share of different combustible substances, as outlined above.

[0041] exist Figure 2 The described method is summarized in the block diagram of FIG. In box 110, the operating parameters of the gas turbine engine are determined. In box 120, the control parameters for the control valves 22 and 23 are determined based on the operating parameters of the gas turbine engine. In box 130, information about the fuel composition is determined, for example, the relative share of at least one combustible substance having a higher flame speed than the first combustible substance can be quantified. The relative share of at least one combustible substance with a higher flame speed can be quantified, for example, as a share of the total fuel composition, a share of the total combustible content, or a relative share relative to the first combustible substance. As described above, the first combustible substance can be methane. At least one combustible substance having a higher flame speed than the first combustible substance can be composed of or include hydrogen and / or C2+ substances. Based on the information about the fuel composition, the control parameters for the control valves 22 and 23 can be adjusted in box 140. In box 150, the control parameters are transmitted to the control valves 22 and 23 as control signals.

[0042] Figure 3 The embodiment shown is Figure 1 The embodiment shown differs in that the high-pressure expansion turbine 121 is fluidly interposed between the upstream combustion zone 15 and the downstream combustion zone 16, and further, the low-pressure expansion turbine 122 is arranged downstream of the downstream combustion zone 16, as suggested, for example, in EP 620 362 and EP 740 057. It should be understood that each of the high-pressure expansion turbine 121 and the low-pressure expansion turbine 122 includes at least one expansion turbine stage. In any other aspects, the control system and the fuel supply system for distributing fuel to the upstream combustion zone and the downstream combustion zone are combined with Figure 1 Same system as outlined.

[0043] Figure 4 An embodiment is outlined in which: Figure 1 The gas turbine engine shown in FIG. 1 is equipped with a slightly modified fuel supply and control system. Figure 1 and Figure 3 The measuring device 31 shown. The supply lines for providing the first fuel supply flow and the second fuel supply flow are equipped with control valves 25 and 26, respectively. Figure 1 In an embodiment of the present invention, the first combustion zone 15 and the second combustion zone 16 may be arranged in a common combustion space or combustion chamber, burner 17 or may not be arranged in a common combustion space or combustion chamber, burner 17. The opening or stroke of the control valves 25 and 26 is used as a control input of the control device 32. The opening or stroke is considered to represent the relative proportion of the first fuel and the second fuel in the blended fuel 205. It is necessary to make assumptions about the composition of the first fuel supplied as the first fuel supply flow and the second fuel supplied as the second fuel supply flow. For example, a conventional offline fuel analysis can be performed to determine the composition of the first fuel supplied as the first fuel supply flow and the second fuel supplied as the second fuel supply flow. The valve stroke can therefore provide quantitative information about the relative proportion of at least one combustible substance. The valve opening or stroke can be supplemented by temperature and pressure measurements of the upstream valves 25 and 26 to more accurately determine the mass flow through the valves 25 and 26. The control device 32 can then generate control parameters for controlling the valves 22 and 23 and therefore for allocating the share of the total fuel mass flow 206 as a function of the valve openings or strokes of the valves 25 and 26, information about the fuel composition and in particular the composition of the combustible substances in the fuel supply flows 203 and 204 and optionally pressure and temperature values ​​upstream of the valves 25 and 26. It will be appreciated that Figure 4 The fuel supply and control system shown in can also be used in conjunction with a gas turbine engine in which at least one expansion turbine stage is fluidly interposed between a relatively upstream combustion zone and a relatively downstream combustion zone, such as Figure 3 The gas turbine engine shown in .

[0044] Those skilled in the art will be able to readily apply the teachings of the present disclosure to multi-shaft gas turbine arrangements, such as are used, but not limited to, for ground and marine vehicle and aircraft propulsion.

[0045] Although the subject matter of the present disclosure has been explained with the aid of exemplary embodiments, it should be understood that these are by no means intended to limit the scope of the invention claimed. It should be understood that the claims cover embodiments not explicitly shown or disclosed herein, and embodiments that deviate from those embodiments disclosed in the exemplary mode of implementing the teachings of the present disclosure will still be covered by the claims.

Claims

1. A method for operating a combustion system, the method comprising providing a combustion fluid flow to the combustion system, causing the combustion fluid flow to flow through the combustion system in a direction from upstream to downstream, and discharging a fuel flow (205) into the combustion system and causing the fuel flow to combust with at least a portion of the combustion fluid flow, in, Discharging the fuel flow into the combustion system includes distributing a first fuel mass flow portion (201) of a total fuel mass flow rate (206) to a first relatively upstream combustion zone (15) of the combustion system, and providing at least a second fuel mass flow portion (202) of the total fuel mass flow rate to at least one relatively downstream second combustion zone (16) downstream of the first combustion zone, wherein the fuel flow (205) comprises a fuel having a fuel composition, the fuel composition comprising a first relative portion of the fuel composition and at least one second relative portion of the fuel composition, the first relative portion of the fuel composition being composed of a first combustible substance (203) having a first flame speed when burned in the combustion fluid, and the at least one second relative portion of the fuel composition being composed of at least one second combustible substance (204) having a second flame speed when burned in the combustion fluid, wherein the second flame speed is greater than the first flame speed, The method further includes quantifying (130) at least one of a first relative fraction (203) of the fuel composition and a second relative fraction (204) of the fuel composition (205), The method further includes controlling (140, 150) the distribution of fuel to a first fuel mass flow share (201) of the total fuel mass flow, at least within a range between two values ​​of a first relative share of the fuel composition and at least one second relative share of the fuel composition, such that the first fuel mass flow share of the total fuel mass flow decreases as the second relative share of the fuel composition increases, and the first fuel mass flow share (201) of the total fuel mass flow increases as the second relative share of the fuel composition decreases.

2. A method according to any preceding claim, wherein: The method includes online monitoring of the fuel composition, including quantification of at least a second portion of the fuel composition and / or a ratio of a second relative portion of the fuel composition to a first relative portion of the fuel composition.

3. A method according to any preceding claim, wherein: The first combustible substance (203) is methane.

4. A method according to any preceding claim, wherein: The at least one second combustible substance (204) consists of at least one of hydrogen and / or at least one C2+ hydrocarbon or a mixture thereof.

5. A method according to any preceding claim, wherein: The stream of combustion fluid and combustion products flowing out of the first combustion zone is at least partially expanded before entering the second combustion zone.

6. A method according to the preceding claim, wherein: The expansion is at least partially achieved in a high-pressure expansion turbine comprising at least one expansion turbine stage (121).

7. A method according to any preceding claim, wherein: The gas stream from the second combustion zone is discharged into an expansion turbine (12, 122).

8. The method according to claim 6 in combination with claim 7, wherein: The high-pressure expansion turbine (121) and a low-pressure expansion turbine (122) arranged downstream of the second combustion zone (16) provide power to a common shaft (13).

9. A method according to any preceding claim, comprising, at least within a second range between two values ​​of at least one of a first relative fraction of the fuel composition and at least one second relative fraction of the fuel composition, controlling the blade angle of at least one variable inlet guide vane row (111) to increase the mass flow rate of the combustion fluid as the second relative fraction of the fuel composition increases, and controlling the blade angle of the at least one variable inlet guide vane row (111) to reduce the mass flow rate of the combustion fluid as the second relative fraction of the fuel composition decreases.

10. A combustion system configured to perform a method according to any preceding claim, the system comprising: at least one combustion flow path and a fuel supply system for flowing a combustion fluid therethrough, The combustion flow path has an upstream end and a downstream end, a first combustion zone (15) located relatively upstream and located inside the at least one combustion flow path, and at least one second combustion zone (16) located relatively downstream and located inside the at least one combustion flow path, wherein the at least one second combustion zone is located downstream of the first combustion zone and is configured to receive a fluid flow flowing out from a combustion zone upstream of the second combustion zone, the first combustion zone (15) is provided with a first fuel discharge device for discharging fuel from the fuel supply system into the combustion flow path and into the first combustion zone, and the at least one second combustion zone (16) is provided with a second fuel discharge device for discharging fuel from the fuel supply system into the combustion flow path and into the at least one second combustion zone, wherein the fuel supply system is configured to supply fuel from a fuel supply source (205) to the first combustion zone (15) via the first fuel discharge device and to the at least one second combustion zone (16) via a corresponding second fuel discharge device, wherein the fuel supply system comprises a control device (22) for allocating a first fuel mass flow share (201) of a total fuel mass flow (206) to the first combustion zone (15), The system further includes a control system (32), which is suitable for and configured to receive information about the fuel composition, the information including quantitative information about the relative proportion of at least one combustible substance, and is further suitable for and configured to control a control device (22) for allocating a first fuel mass flow proportion of the total fuel mass flow to the first combustion zone (15), so that at least within a range between two values ​​of the first relative proportion of the fuel composition and at least one of the at least one second relative proportion of the fuel composition, the first fuel mass flow proportion of the total fuel mass flow allocated to the first combustion zone decreases as the second relative proportion of the fuel composition increases, and the first fuel mass flow proportion of the total fuel mass flow allocated to the first combustion zone increases as the second relative proportion of the fuel composition decreases.

11. A combustion system according to the preceding claim, wherein: A measuring device (31) suitable for online characterization of the composition of the fuel supplied to the at least one combustion flow path is operatively connected to the fuel supply system and is configured to quantify the proportion of at least one substance in the fuel composition provided by the fuel supply system, wherein the measuring device is further operatively connected to the control device so as to provide the control device (32) with quantitative information about the proportion of at least one combustible substance in the fuel composition.

12. A combustion system according to the preceding claim, wherein: The combustion system is configured with a high-pressure expansion turbine including at least one expansion turbine stage (121) fluidly interposed between the first combustion zone (15) and the second combustion zone (16).

13. The combustion system according to any one of claims 10 and 11, wherein: The first combustion zone and the second combustion zone are arranged in a common combustion space (17).

14. A gas turbine engine comprising a compressor (11), an expansion turbine (12, 121, 122) and a combustion system according to any one of claims 9 to 11, wherein: The combustion system is arranged and configured to receive combustion fluid from the compressor and discharge fluid from the combustion system into the expansion turbine.

15. A gas turbine engine according to the preceding claim, wherein: At least one high-pressure expansion turbine including at least one expansion turbine stage (121) is fluidly interposed between the first combustion zone (15) and the second combustion zone (16), and at least one low-pressure combustion turbine (122) is arranged downstream of the second combustion zone.

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