COMBUSTOR OF GAS TURBINE ENGINE

Abstract

A combustor of a gas turbine engine includes a combustion chamber, pilot fuel supply unit configured to supply solely auxiliary fuel to a flame holding region in the combustion chamber, first auxiliary fuel amount adjustment unit configured to adjust an amount of the auxiliary fuel supplied from the pilot fuel supply unit, main fuel supply unit configured to supply unburned gas and the auxiliary fuel to an unburned gas combustion region in the combustion chamber continuous with the flame holding region, and second auxiliary fuel amount adjustment unit configured to adjust an amount of the auxiliary fuel, in which the first auxiliary fuel amount adjustment unit is configured to adjust the amount of the auxiliary fuel supplied from the pilot fuel supply unit to an amount for flame holding in the flame holding region throughout an operation of the gas turbine engine.

Claims

1. A combustor of a gas turbine engine in which unburned gas and an auxiliary fuel are supplied and combusted, the combustor comprising: a combustion chamber in which the unburned gas, the auxiliary fuel, and compressed air are supplied, and the unburned gas and the auxiliary fuel are combusted; a pilot fuel supply unit configured to supply solely the auxiliary fuel to a flame holding region in the combustion chamber; a first auxiliary fuel amount adjustment unit configured to adjust an amount of the auxiliary fuel supplied from the pilot fuel supply unit; a main fuel supply unit configured to supply the unburned gas and the auxiliary fuel to an unburned gas combustion region in the combustion chamber continuous with the flame holding region; and a second auxiliary fuel amount adjustment unit configured to adjust an amount of the auxiliary fuel supplied from the main fuel supply unit, wherein the first auxiliary fuel amount adjustment unit is configured to adjust the amount of the auxiliary fuel supplied from the pilot fuel supply unit to an amount for flame holding in the flame holding region throughout an operation of the gas turbine engine.

2. The combustor according to claim 1, wherein the amount of the auxiliary fuel needed for flame holding in the flame holding region is decided based on a pressure and a temperature of the compressed air at an inlet in the combustion chamber.

3. The combustor according to claim 1, wherein the amount of the auxiliary fuel supplied from the pilot fuel supply unit is a minimum amount needed for flame holding in the flame holding region or an amount obtained by adding a predetermined amount to the minimum amount.

4. The combustor according to claim 1, wherein the amount of the auxiliary fuel supplied from the main fuel supply unit is an amount obtained by subtracting the amount of the auxiliary fuel supplied from the pilot fuel supply unit from a total amount of the auxiliary fuel to be supplied to the combustion chamber.

5. The combustor according to claim 4, wherein the total amount of the auxiliary fuel to be supplied to the combustion chamber is a fuel amount equivalent to a calorific value obtained by subtracting a calorific value of the unburned gas supplied from the main fuel supply unit from a total calorific value of a fuel to be supplied to the combustion chamber.

6. The combustor according to claim 1, wherein the amount of the auxiliary fuel supplied from the main fuel supply unit is increased or decreased in response to a load of the gas turbine engine.

7. The combustor according to claim 1, wherein an amount of the unburned gas supplied from the main fuel supply unit is estimated from a parameter having a correlation with a flow rate of the unburned gas.

8. The combustor according to claim 1, further comprising unburned gas adjustment unit configured to adjust an amount of the unburned gas supplied from the main fuel supply unit.

9. The combustor according to claim 1, wherein the unburned gas combustion region surrounds the flame holding region in the combustion chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Features, advantages, and technical and industrial significance of exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

[0018] FIG. 1A is a schematic diagram showing a schematic configuration of a gas turbine engine to which a combustor according to the present embodiment is applied;

[0019] FIG. 1B is a diagram showing a schematic configuration of one aspect of the combustor according to the present embodiment;

[0020] FIG. 2 is a block diagram showing a configuration of one aspect of a process of deciding a supply flow rate of an auxiliary fuel in the combustor according to the present embodiment;

[0021] FIG. 3 is a block diagram showing a configuration of another aspect of the process of deciding the supply flow rate of the auxiliary fuel in the combustor according to the present embodiment;

[0022] FIG. 4A is a diagram showing a schematic configuration of another aspect of the combustor according to the present embodiment; and

[0023] FIG. 4B is a block diagram showing a configuration of one aspect of the process of deciding the supply flow rate of the auxiliary fuel in the combustor in the aspect of FIG. 4A.

DETAILED DESCRIPTION OF EMBODIMENTS

[0024] Configuration of Gas Turbine Engine

[0025] With reference to FIG. 1A, a combustor according to the present embodiment is applied to a gas turbine engine 1 in which unburned gas is supplied as a part of a fuel for processing the unburned gas. The gas turbine engine 1 includes a combustor 2, a turbine 3, and a compressor 4, similar to a normal gas turbine engine in the related art used in this field. In the combustor 2, as the fuel, the unburned gas is supplied from a unburned gas supply line 5 and an auxiliary fuel is supplied from an auxiliary fuel supply line 6 (6p, 6r), these fuels are combusted by using compressed air supplied from a compressed air supply line 7 from the compressor 4, and the combustion gas having a high temperature and a high pressure is delivered to a combustion gas delivery line 8. As described in the “SUMMARY” column, the unburned gas may be any gas having room for combustion in exhaust gas in industrial machines or transportation machines of facilities, such as factories, for example, exhaust gas from a coke oven, VOC gas, CO, HC, or NO. Since the unburned gas described above generally has a small calorific value, the auxiliary fuel having a larger calorific value is supplied such that the gas turbine engine can be reliably operated. As described above, the auxiliary fuel may be a fuel normally used as a fuel for the gas turbine engine, or may be a gas fuel, such as city gas, or a liquid fuel, such as kerosene. The turbine 3 is rotated by the combustion gas from the combustion gas delivery line 8, and the compressor 4 is rotated due to the rotation, compresses air At taken in from the atmosphere, and delivers the compressed air At to the compressed air supply line 7. In addition, any machine equipment (not shown), typically, a generator is connected to a rotation shaft 3a of the turbine 3, and rotational energy of the turbine 3 is recovered by the machine equipment, such as the generator or is used as energy for an operation of the machine. In addition, since the exhaust gas discharged from the turbine 3 has a high temperature, a configuration may be adopted in which heat energy thereof is used to raise a temperature of the compressed air given to the combustor 2, an exhaust line 9 through which the exhaust gas flows and the compressed air supply line 7 pass through a heat exchanger 10, and the heat energy of the exhaust gas is transferred to the compressed air such that the energy efficiency can be improved. As will be described below, in order to control a flow rate of the auxiliary fuel supplied to the combustor 2 and a flow rate of the unburned gas, a temperature T.sub.35 and a pressure P.sub.35 of the compressed air at an inlet of the combustor 2 may be measured by a temperature measuring instrument 7a and a pressure measuring instrument 7b, respectively, and an unburned gas flow rate G.sub.ug and an unburned gas temperature T.sub.ug may be measured by a flow rate measuring instrument 5a and a temperature measuring instrument (not shown), respectively.

[0026] In the configuration described above, a control of a supply amount of the auxiliary fuel is executed by a control device 50. The control device 50 may be configured by a computer device including a computer having a CPU, a ROM, a RAM and an input/output port device connected to each other by a bidirectional common bus in a normal type and a drive circuit, and the operation of the control device 50 may be realized by an operation of the computer device in response to a program. The control device 50 may be configured to adjust the flow rate of the auxiliary fuel in a pilot auxiliary fuel flow rate control valve 6a and an auxiliary fuel extra flow rate control valve 6b to be described below with reference to a state of the compressed air from the temperature measuring instrument 7a and the pressure measuring instrument 7b, the flow rate and the temperature of the unburned gas from the flow rate measuring instrument 5a and the temperature measuring instrument (not shown) respectively, a rotation speed and a torque of the turbine 3 from a turbine rotation measuring instrument 3b that detects an output of the turbine, and the like (further, in another embodiment as will described below, the flow rate of the unburned gas may be controlled by an unburned gas flow rate control valve 5b (see FIG. 4A)).

[0027] Configuration of Combustor

[0028] More specifically, as shown in FIG. 1B, the combustor 2 according to the present embodiment is configured in which in a combustion chamber 12, the unburned gas is supplied from the unburned gas supply line 5 and the auxiliary fuel is supplied from the auxiliary fuel supply line 6, the compressed air flows in from the compressed air supply line 7 (not shown in FIG. 1B), and the unburned gas and the auxiliary fuel are combusted. In such a configuration, a configuration is adopted in which the auxiliary fuel supply line 6 is divided into an auxiliary fuel flame holding flow rate supply line 6p connected to a pilot auxiliary fuel supply nozzle 13 (pilot fuel supply unit) and an auxiliary fuel extra flow rate supply line 6r connected to an auxiliary fuel and unburned gas supply nozzle 14 (main fuel supply unit), the pilot auxiliary fuel extra flow rate control valve 6a and the auxiliary fuel extra flow rate control valve 6b are provided in these lines, respectively, and the flow rate of the auxiliary fuel supplied to each nozzle is controlled. In addition, the unburned gas supply line 5 may be further connected to the auxiliary fuel and unburned gas supply nozzle 14, typically, the unburned gas and the auxiliary fuel may be appropriately mixed and supplied from the auxiliary fuel and unburned gas supply nozzle 14. The supply of the fuel from the pilot auxiliary fuel supply nozzle 13 and the auxiliary fuel and unburned gas supply nozzle 14 may be achieved by injecting or spraying each fuel such that the fuel is appropriately dispersed (however, the aspect of the supply of the fuel is not limited thereto). Then, inside the combustion chamber 12, a structure of the combustion chamber 12 is designed and formed such that the auxiliary fuel from the pilot auxiliary fuel supply nozzle 13 is supplied so as to be mostly dispersed over a region PB and the auxiliary fuel and the unburned gas from the auxiliary fuel and unburned gas supply nozzle 14 are supplied so as to be mostly dispersed over a region MB. In FIG. 1B, the region PB is drawn so as to overlap with the region MB, but actually, the combustion chamber 12 has a mostly tubular structure, and the region PB and the region MB are divided such that boundaries thereof are in contact with each other. Typically, as will described below, the region MB may surround the region PB such that the flame generated in the region PB is transferred to the region MB as evenly as possible.

[0029] In the configuration of the combustor 2 described above, substantially solely the auxiliary fuel is dispersed in the region PB, and the unburned gas having a calorific value smaller than that of the auxiliary fuel is dispersed in the region MB. Then, in the region PB, throughout the operation of the gas turbine engine, that is, in the normal operation state in addition to when the engine is activated, in particular, even in a state where the load of the gas turbine engine can fluctuate widely, the auxiliary fuel is supplied such that the flame is held, as a result, the flame in the region PB is transferred to the region MB, and in the region MB, the unburned gas is reliably combusted. Therefore, the region PB is referred to as a “flame holding region”, and the region MB is referred to as an “unburned gas combustion region”. In addition, when the amount of the auxiliary fuel needs to be increased as compared with the amount supplied to the flame holding region PB in order to obtain the stable rotation state of the gas turbine engine or in order to increase the load of the gas turbine engine in response to the request of the machine equipment, such as the generator, connected to the turbine, as will described below, such an increment of the auxiliary fuel is supplied to the region MB together with the unburned gas.

[0030] With the configuration of the combustor 2 described above, since the flame is held in the flame holding region PB regardless of a change in a load state or a change in a state of the unburned gas, even when there is the change in the load state or the change in the state of the unburned gas, a blowout state in the combustion chamber is avoided. In addition, when the flame is held in the flame holding region PB, solely the auxiliary fuel having a large calorific value is substantially dispersed as the fuel in such a flame holding region PB, so that the auxiliary fuel ignites in a smaller amount as compared to a case where the auxiliary fuel is dispersed together with the unburned gas having a small calorific value, and the flame can be held. Therefore, by supplying the auxiliary fuel to the flame holding region PB such that solely the auxiliary fuel is substantially dispersed, the amount of the auxiliary fuel at the equivalent ratio optimized for flame holding can be further decreased (as compared to a case where the auxiliary fuel is dispersed together with the unburned gas). In addition, since solely the auxiliary fuel is dispersed in the flame holding region PB, the flame holding region PB can be designed and formed such that the equivalent ratio can be obtained such that the flame can be held in a state where the amount of the auxiliary fuel is decreased as small as possible, whereas since the increment of the auxiliary fuel in response to the load fluctuation of the gas turbine engine is supplied to the unburned gas combustion region MB, even in that case, the fuel in the flame holding region PB is not in a rich state, and it is also advantageous in that the stable combustion and the suppression of NOx or CO generation are achieved.

[0031] Control of Flow Rate of Auxiliary Fuel

[0032] In the combustor 2 of the present embodiment described above, the unburned gas and the auxiliary fuel are supplied to the combustion chamber 12 as the fuel, in one aspect, the unburned gas is discharged from a discharge source thereof and then supplied as it is to the combustion chamber 12 from the unburned gas supply line 5, and regarding the auxiliary fuel, the flow rates (flame holding flow rate and extra flow rate) supplied to the flame holding region PB and the unburned gas combustion region MB, respectively, may be decided in the control device 50 in consideration of the operation state of the gas turbine engine in an aspect shown in the block diagram of FIG. 2. The control device 50 may include a fuel total flow rate calculation unit that decides a total fuel flow rate G.sub.sf of the fuel in which the unburned gas and the auxiliary fuel are mixed supplied to the combustion chamber 12, an auxiliary fuel flame holding flow rate calculation unit that decides an auxiliary fuel flow rate (flame holding flow rate) G.sub.sfmin supplied to the flame holding region PB, and an auxiliary fuel extra flow rate calculation unit that decides an auxiliary fuel flow rate (extra flow rate) G.sub.sfre supplied to the unburned gas combustion region MB.

[0033] Specifically, with reference to FIG. 2, first, in the fuel total flow rate calculation unit, the total fuel flow rate G.sub.sf of the fuel in which the unburned gas and the auxiliary fuel are mixed is decided such that the stable rotational operation in the gas turbine engine is achieved. In this regard, the total amount of the fuel supplied may be limited such that the temperature of the combustion chamber 12 is not excessively high. Therefore, specifically, the total fuel flow rate G.sub.sf may be decided by monitoring the rotation speed and the output torque of the rotation shaft 3a of the turbine 3 and the temperature of the combustion chamber 12 such that the rotation of the turbine 3 is stable and the temperature of the combustion chamber 12 is not excessively high. Here, regarding the operation of the turbine 3, the output (load) of the turbine 3 may be course in response to combustion processing of the unburned gas, in that case, a target value (target output) of a rotation output of the turbine 3 may be a value at which the rotation of the turbine 3 is stable, and the needed amount of the fuel may be decided such that the rotation of the turbine 3 achieves such a target output. Alternatively, the output of the turbine 3 may fluctuate in response to the request of the machine equipment, such as the generator, connected to the rotation shaft 3a of the turbine 3, in that case, the needed amount of the fuel may be supplied with reference to the target output such that the output of the turbine 3 achieves the target value (target output) decided in response to the request of the machine equipment, such as the generator, by any method. In addition, since the temperature of the combustion chamber 12 is decided by adding the calorific value of the fuel to the calorific value of the compressed air at the inlet of the combustion chamber 12, the estimation can be made in consideration of the calorific value of the fuel flowing in the combustion chamber 12 from the temperature T.sub.35 and the pressure P.sub.35 of the compressed air measured at the inlet of the combustion chamber 12. Then, instead of directly measuring the temperature of the combustion chamber 12, as shown in FIG. 2, the total amount of the fuel supplied may be limited based on the temperature T.sub.35 and the pressure P.sub.35 of the compressed air at the inlet of the combustion chamber 12. In this regard, in a case where the unburned gas is supplied to the combustion chamber 12, the temperature of the combustion chamber 12 is higher as the temperature of the unburned gas itself is higher, and thus the total fuel flow rate G.sub.sf supplied may be further decided with reference to the unburned gas temperature T.sub.ug (in a case where the flow rate of the unburned gas is small, the influence of the unburned gas temperature T.sub.ug is small, so that the reference may be omitted).

[0034] Next, regarding the auxiliary fuel flame holding flow rate G.sub.sfmin, as described above, since solely the auxiliary fuel for flame holding is substantially supplied to the flame holding region PB, the auxiliary fuel flame holding flow rate G.sub.sfmin may be decided so as to have the optimum equivalent ratio for flame holding in response to the amount of the compressed air flowing through the flame holding region PB. Since the amount of the compressed air flowing through the flame holding region PB can be decided based on the temperature T.sub.35 and the pressure P.sub.35 of the compressed air at the inlet of the combustion chamber 12, the auxiliary fuel flame holding flow rate G.sub.sfmin may be decided in the auxiliary fuel flame holding flow rate calculation unit based on the temperature T.sub.35 and the pressure P.sub.35. In the embodiment, the map for deciding the auxiliary fuel flame holding flow rate G.sub.sfmin for given the optimum equivalent ratio may be prepared by using the temperature T.sub.35 and the pressure P.sub.35 of the compressed air in advance by an experiment and the like as variables, and in the operation of the gas turbine engine, the auxiliary fuel flame holding flow rate G.sub.sfmin may be provided by the map calculation by using the temperature T.sub.35 and the pressure P.sub.35 of the compressed air measured sequentially. The auxiliary fuel flame holding flow rate G.sub.sfmin is decided to hold the flame, and the calorific value generated by the combustion of such a flow rate contributes as a part of the output of the gas turbine engine. As described above, since the auxiliary fuel flame holding flow rate G.sub.sfmin is desirably as small as possible for saving of the usage amount of the auxiliary fuel, the stable combustion, and the suppression of NOx or CO generation, the auxiliary fuel flame holding flow rate G.sub.sfmin may be the minimum amount needed for flame holding in the flame holding region PB, but may be an amount obtained by adding a predetermined amount (that can be appropriately set) to such a minimum amount as long as the action and effect of the present disclosure and a case of the minimum amount are approximately not affected.

[0035] The auxiliary fuel extra flow rate G.sub.sfre supplied to the unburned gas combustion region MB is supplied to further supplement the needed calorific value in order to achieve a state where the turbine 3 generates the target output or a state where the turbine 3 is stably rotated such that the temperature of the combustion chamber 12 is not excessively high with respect to the calorific value obtained by the combustion of the auxiliary fuel flame holding flow rate G.sub.sfmin in the flame holding region PB and the combustion of the unburned gas in the unburned gas combustion region MB. Therefore, the auxiliary fuel extra flow rate G.sub.sfre may be given as will described below by using the total fuel flow rate G.sub.sf to be supplied to the combustion chamber 12, the auxiliary fuel flame holding flow rate G.sub.sfmin, and an unburned gas equivalent flow rate G.sub.ug* that is converted in terms of the calorific value.

[00001]$\begin{array}{cc}{G}_{\mathrm{sfre}}=G_{\mathrm{sf}}-G_{\mathrm{sfmin}}-G_{\mathrm{ug}}^{*}& \left(1\right)\end{array}$

[0036] (The unburned gas equivalent flow rate G.sub.ug* is a value obtained by multiplying the actual unburned gas flow rate G.sub.ug by the calorific value per unit flow rate (auxiliary fuel calorific value/unburned gas calorific value).)

[0037] Therefore, in the auxiliary fuel extra flow rate calculation unit, as shown in FIG. 2, the auxiliary fuel extra flow rate G.sub.sfre may be decided by the equation (1) with reference to the total fuel flow rate G.sub.sf from the total fuel flow rate calculation unit, the auxiliary fuel flame holding flow rate G.sub.sfmin, and the unburned gas flow rate G.sub.ug from the fuel total flow rate calculation unit.

[0038] In the embodiment, the total fuel flow rate G.sub.sf, the auxiliary fuel flame holding flow rate G.sub.sfmin, and the auxiliary fuel extra flow rate G.sub.sfre are sequentially calculated throughout the operation of the gas turbine engine, and a control command is given from the control device 50 to the pilot auxiliary fuel extra flow rate control valve 6a and the auxiliary fuel extra flow rate control valve 6b such that the auxiliary fuel is supplied from the pilot auxiliary fuel supply nozzle 13 and the auxiliary fuel and unburned gas supply nozzle 14 at the auxiliary fuel flame holding flow rate G.sub.sfmin and the auxiliary fuel extra flow rate G.sub.sfre, respectively. In the present embodiment, as described above, it should be understood that throughout the operation of the gas turbine engine, that is, even in the stable operation state in addition to when the engine is activated, solely the auxiliary fuel is supplied to the flame holding region PB at the auxiliary fuel flame holding flow rate G.sub.sfmin and the flame is held in the flame holding region PB.

[0039] In the control of the flow rate of the auxiliary fuel described above, when the following equation are satisfied,

[00002]$\begin{array}{cc}{G}_{sf}-G_{\mathrm{sfmin}}-G_{ug}^{*}=0G_{\mathrm{sfmin}}=G_{sf}-G_{ug}^{*}& \left(2\right)\end{array}$

[0040] a state where an engine driving force and the load are balanced and the rotation speed is maintained at a fixed value is a state where the unburned gas can be processed most efficiently. Then, in the control described above, in a case where the load of the engine is increased, such as a case where the power generation request or the load request is increased from a state of the equation (2), in order to maintain the rotation speed of the engine in response to the load, the flow rate of the fuel is calculated and output by a feedback control from a state of the engine, such as the rotation speed. Here, in the flame holding region PB, the equivalent ratio capable of holding the flame is suitably formed such that the auxiliary fuel flame holding flow rate is the minimum value, the combustion is not in the rich state, and NOx or CO generation can be suppressed as small as possible, and the auxiliary fuel extra flow rate G.sub.sfre is supplied to the unburned gas combustion region instead of the flame holding region PB, even when the auxiliary fuel is increased or decreased, an optimum state of the flame holding region PB is maintained, a state where NOx or CO generation is suppressed as small as possible is maintained.

[0041] In the control of the flow rate of the auxiliary fuel described above, the unburned gas flow rate G.sub.ug is not a value directly measured by the unburned gas supply line 5, but any amount having a correlation with the flow rate of the unburned gas may be measured and converted into the flow rate of the unburned gas, and the measured amount may be referred to. As such an amount, specifically, an operating rate of a furnace, an output of a target that discharges the unburned gas, or the like can be considered, and in a case where a composition of the unburned gas is changed, the amount of an unburned gas component may be referred to. For example, such a configuration may be applied in a case where the flow rate of the unburned gas cannot be measured in some factories.

[0042] By the way, as can be understood from the block diagram of FIG. 2, the auxiliary fuel flame holding flow rate G.sub.sfmin is decided based on the temperature and the pressure of the compressed air flowing in the combustion chamber 12 without referring to the operation state (rotation speed and the like) of the gas turbine engine, and the flow rate of the fuel that is adjusted to stabilize the operation state of the gas turbine engine or to fluctuate the load in response to the request from the machine, such as the generator, connected to the turbine is the auxiliary fuel extra flow rate G.sub.sfre. In addition, in a case where an adjustment mechanism of the flow rate of the unburned gas is not provided as in another embodiment as will described below, the flow rate of the unburned gas is decided by the course from the discharge source. Therefore, the auxiliary fuel extra flow rate G.sub.sfre may be substantially adjusted by the feedback control of the operation state of the gas turbine engine. Therefore, as shown in FIG. 3, the auxiliary fuel extra flow rate G.sub.sfre may be adjusted with reference to output of the turbine, such as the turbine rotation speed or the torque, separately from the auxiliary fuel flame holding flow rate G.sub.sfmin such that the target output is achieved. In this case, the change in the rotation state of the turbine due to the fluctuation of the flow rate of the unburned gas is absorbed by adjusting the auxiliary fuel extra flow rate G.sub.sfre.

[0043] Mode in which Flow Rate of Unburned Gas can be Adjusted

[0044] Since the gas turbine engine according to the present embodiment has a main purpose of processing the unburned gas, the unburned gas generally flows in the combustion chamber 12 without adjusting the flow rate. However, in order to stabilize the operation state of the gas turbine engine or avoid overheating of the combustor, as schematically shown in FIG. 4A, the unburned gas flow rate control valve 5b may be provided as a unit that adjusts the flow rate of the unburned gas. In a case of a configuration in which the flow rate of the unburned gas is adjusted, in the control device 50, as shown in the block diagram of FIG. 4B, the total fuel flow rate G.sub.sf, the auxiliary fuel flame holding flow rate G.sub.sfmin, and the unburned gas flow rate G.sub.ug are referred to in the auxiliary fuel extra flow rate calculation unit, and the auxiliary fuel extra flow rate G.sub.sfre and an unburned gas supply amount (unburned gas control flow rate) G.sub.ugmax to the combustion chamber 12 that is controlled in the unburned gas flow rate control valve 5b are decided. As described above, the auxiliary fuel extra flow rate G.sub.sfre is decided by the equation (1), and for example, in a case where the unburned gas equivalent flow rate G.sub.ug* is large and G.sub.sfre<0 is satisfied, the unburned gas control flow rate G.sub.ugmax may be decided such that G.sub.sfre≥0 is satisfied (in a case where G.sub.sfre<0 is satisfied, G.sub.sf<G.sub.sfmin+G.sub.ug* is satisfied, the sum of the auxiliary fuel flame holding flow rate G.sub.sfmin and the unburned gas flow rate G.sub.ug exceeds the total fuel flow rate G.sub.sf that is decided in consideration of the stabilization of the operation state of the gas turbine engine or the avoidance of overheating of the combustor, and thus the flow rate of the unburned gas supplied to the combustion chamber 12 is limited). Then, the control command may be given to the unburned gas flow rate control valve 5b from the control device 50 such that the flow rate of the unburned gas actually supplied to the combustion chamber 12 becomes the unburned gas control flow rate G.sub.ugmax.

[0045] Therefore, in the present embodiment described above, the combustor is configured to execute the combustion processing of the unburned gas and supply, in the gas turbine engine that recovers the calorific value, the auxiliary fuel supplied to the combustion chamber 12 to stabilize the operation state thereof to separate regions respectively at the flow rate for flame holding in the combustion chamber and the flow rate for achieving the operation state in response to the load fluctuation. With such a configuration, the amount of the auxiliary fuel for flame holding can be decreased as small as possible and the stable operation state of the gas turbine engine can be achieved in response to the load fluctuation, and thus the effective use of the resource and the decrease in the running cost can be expected.

[0046] Although the above description has been made in connection with the embodiments of the present disclosure, it is clear that many modifications and changes can be easily made by those skilled in the art, and an applicable embodiment of the present disclosure is not limited to solely the embodiments described above and applied to various devices without departing from the concept of the present disclosure.