JP2018146193A - Liquid fuel burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid fuel burner capable of evenly combusting liquid fuel so as to suppress occurrence of NOx without generating a hotspot in a medium or high-load application, and suppressing occurrence of CO and unburned HC in a non-load or low-load application, to thereby maintain stable combustion.SOLUTION: A burner has: a single fuel injection valve configured to inject liquid fuel; a splitter nozzle surrounding the fuel injection valve coaxially, and whose diameter is contracted toward an outlet end; an outer shroud surrounding the splitter nozzle coaxially, and forming an annular air flow passage therearound; and means of imparting revolution force to airflow flowing in the annular air flow passage. The burner is configured to dividedly supply air into an internal flow passage of the splitter nozzle and the annular air flow passage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid fuel burner, and more particularly to a burner suitable for a gas turbine apparatus.

  NOx emissions associated with fuel combustion increase exponentially as the flame temperature rises, so lowering the flame temperature is effective in reducing NOx emissions, and the ratio of air to fuel is excessive. Thus, a lean combustion method for burning is effective. However, in the conventional diffusion combustion in which liquid fuel is directly injected into the combustion chamber, it is difficult to uniformly disperse the fuel droplets in the air. Since the fuel concentration is inevitably high, a micro hot spot is likely to be generated by this combustion, and there is a limit in suppressing the NOx emission amount. In order to suppress the occurrence of micro hot spots, fuel is injected into an excessive amount of air in the pre-evaporation pre-mixing chamber, fuel droplets are pre-evaporated, pre-mixed with air, and then diluted in the combustion chamber. Combustion method was considered. This is ideal for liquid fuels from the standpoint of reducing NOx emissions, but when the temperature of the air rises to high temperatures and pressures, the reaction of the fuel vapor / air mixture becomes faster and the fuel pre-evaporation is completely eliminated. Spontaneous ignition occurs before the end of the combustion, the start of combustion becomes uneven, NOx emission cannot be suppressed as intended, and the wall of the pre-evaporation premixing chamber may be burned by combustion in the preevaporation premixing chamber .

  Therefore, the residence time in the pre-evaporation pre-mixing chamber is shortened, a part of the injected fuel is pre-evaporated, and the mixture pre-mixed with air is combusted from the pre-evaporation pre-mixing chamber before spontaneous ignition occurs. It was considered to be moved indoors. In this method, according to the pre-evaporation premixing method, by appropriately controlling the air-fuel ratio at high load, not only NOx but also CO and unburned HC emissions can be suppressed. When the load is low, the fuel flow rate is small, so that the flame temperature becomes low, the combustion becomes unstable and incomplete, and the emission of CO and unburned HC increases.

  In order to cope with such a problem, for example, as described in Patent Documents 1 and 2 below, a pilot fuel injection valve is arranged on the inner side and a main fuel injection valve is coaxially arranged on the outer side, and a diffusion combustion system using direct fuel injection However, stable combustion is ensured by the pilot fuel injection valve when there is no load or low load, and the combustion gas temperature is made uniform by operating both the pilot fuel injection valve and the main fuel injection valve during medium to high loads. It is conceivable to reduce NOx.

Japanese Unexamined Patent Publication No. 2016-41999 JP 2016-173225 A

  The liquid fuel burner is required to have a capability of generating high-temperature gas with liquid fuel while suppressing the generation of NOx in the combustion chamber. Further, a wide load range is used as in the case where the burner is a burner for a gas turbine. In addition, when the vehicle is operated over a long period of time, it is required to have the performance of ensuring stable combustion of the liquid fuel by suppressing the generation of CO and unburned HC during no load or low load. In order to generate a high-temperature gas while suppressing the generation of NOx, it is important to raise the temperature of the entire gas generated by the combustion of the fuel as uniformly as possible so as not to generate a hot spot in the combustion chamber. In addition, in order to suppress the generation of CO and unburned HC at the time of no load or low load and ensure stable combustion of the liquid fuel, it is prevented from mixing excess air with the fuel whose injection amount is reduced. This is very important. However, if the fuel injection valve has a multiple structure as described in Patent Document 1 or 2 described above, the structure of the burner becomes complicated accordingly, and it is necessary to control the distribution of fuel to each of the multiple fuel injection valves. It becomes.

  The present invention avoids the generation of hot spots and suppresses the generation of NOx by mixing liquid fuel highly uniformly with air while evaporating in the process of mixing with combustion air during medium to high loads. A burner for liquid fuel that can generate high-temperature gas and that suppresses the generation of CO and unburned HC due to poor combustion of fuel due to excess air during no-load or low-load when the fuel injection amount is reduced, An object of the present invention is to provide a single fuel injection valve without using multiple structures as described in Patent Document 1 or 2.

  In order to solve the above problems, the present invention provides a single fuel injection valve that injects liquid fuel, a splitter nozzle that coaxially surrounds the fuel injection valve and has a diameter reduced toward an outlet end, and the splitter nozzle. An outer shroud that is concentrically surrounded and forms an annular air flow path around the splitter nozzle, and means for imparting a swirling force to the air flow flowing through the annular air flow path, and liquid fuel is supplied to the fuel injection valve Then, the present invention proposes a liquid fuel burner characterized in that air is divided and supplied to an internal flow path of the splitter nozzle and the annular air flow path.

  The burner may further include means for imparting a turning force to the airflow flowing through the internal flow path of the splitter nozzle.

  The means for applying a swirling force to the air flow flowing through the internal flow path of the splitter nozzle is a reciprocal swirl for the air flow flowing through the inner peripheral portion and the air flow flowing through the outer peripheral portion of the internal flow path of the splitter nozzle. A direction turning force may be applied.

  The inner peripheral surface of the outer shroud may be reduced in diameter so as to match the shape reduced toward the outlet end of the splitter nozzle in a portion overlapping the splitter nozzle in the axial direction.

  The inlet portion of the annular air channel or in addition to the inlet portion of the splitter nozzle may be a radial channel directed in the radial direction.

  The fuel injection valve may have a two-fluid injection structure capable of injecting fuel atomization air in addition to fuel injection.

  When the burner is a burner of a gas turbine device, air compressed by a compressor driven by the turbine of the gas turbine device is supplied to the internal flow channel of the splitter nozzle and the annular air flow channel by exhaust of the turbine. As the air for fuel atomization supplied with the heated air and injected by the fuel injection valve, the air compressed by the compressor may be supplied without being heated by the exhaust of the turbine.

  As described above, the burner has a single fuel injection valve that injects liquid fuel, a splitter nozzle that coaxially surrounds the fuel injection valve and has a diameter reduced toward the outlet end, and that surrounds the splitter nozzle coaxially and that splits the nozzle. An outer shroud that forms an annular air passage around the air shroud, and means for imparting a swirling force to the air flow that flows through the annular air passage, and liquid fuel is supplied to the fuel injection valve, and air is supplied to the splitter. If the nozzle internal flow path and the annular air flow path are divided and supplied, the swirl force is applied to the air flow flowing through the fuel injection valve, splitter nozzle, outer shroud, and annular air flow path. By appropriate design of the means to be applied, the fuel injected from the fuel injection valve at the time of middle to high load and the air supplied to the internal flow path of the splitter nozzle A flame that does not cause ignition between the outlet end of the splitter nozzle and a combustion flame forming region that is ignited at a high flow rate through the outlet end of the splitter nozzle. A lift-off region can be formed. In this case, the fuel is mixed with a part of the total air supply amount in the splitter nozzle, and the fuel component is concentrated and becomes a mixture of fuel and air that is easy to hold the flame stably and axially from the outlet end of the splitter nozzle. In this case, a swirling force is applied by mixing with the air flow swirling out of the annular air flow path around the splitter nozzle, and the fuel component is diffused in the radial direction by being stirred. Therefore, if the fuel injection valve, splitter nozzle, outer shroud, and means for imparting a swirling force to the air flow flowing through the annular air flow path are appropriately designed, the fuel is diffused while being appropriately vaporized in the flame lift-off region and burned. In the flame formation region, it is possible to stably hold the flame, uniformly disperse the fuel from the central portion to the outer peripheral portion, and achieve the combustion of the fuel without causing a hot spot.

  On the other hand, when there is no load or low load, the low flow rate fuel injected from the fuel injection valve is gently ejected through the outlet end of the splitter nozzle together with the same low flow rate air supplied to the internal flow path of the splitter nozzle. In the case of no load or low load, since the air temperature is low, the fuel droplets hardly evaporate. Therefore, the fuel ejected from the splitter nozzle does not diffuse in the radial direction in the flame lift-off region, and goes directly to the combustion flame forming region. In the combustion flame formation region, the fuel does not fall into lean combustion, and can be burned satisfactorily while suppressing the generation of CO and unburned HC under a sufficiently high flame temperature necessary for stable combustion of the fuel. .

  If the burner further has means for imparting a swirl force to the air flow flowing through the internal flow path of the splitter nozzle, the fuel droplets injected from the fuel injection valve are atomized better and more easily in the air flow. It can be well dispersed to promote its evaporation. In this case, in particular, the means for imparting the swirling force to the air flow flowing through the internal flow path of the splitter nozzle can be applied to the air flow flowing through the inner peripheral portion and the air flow flowing through the outer peripheral portion of the splitter nozzle. If the swirl force in the reverse swirl direction is applied, not only can the fuel droplets injected from the fuel injection valve be better dispersed in the air flow, but also increase turbulence and promote evaporation, They interfere with each other and can form a substantially swirling flow near the central axis at the outlet of the splitter nozzle, which can lengthen the flame lift-off region, where fuel droplets evaporate, Mixing can proceed. In order to apply a swirl force in the opposite swirl direction to the air flow flowing in the inner peripheral portion of the internal flow path of the splitter nozzle and the air flow flowing in the outer peripheral portion, the inlet portion of the internal flow path of the splitter nozzle A swirler or the like in which the twist of the blades is reversed between the inner peripheral portion and the outer peripheral portion may be provided.

  If the inner circumferential surface of the outer shroud is reduced in diameter so as to match the shape reduced in diameter toward the outlet end of the splitter nozzle in the portion overlapping the splitter nozzle in the axial direction, the annular air flow path The flow velocity of the flowing out air flow can be increased, the interference with the mixture jet from the splitter nozzle can be strengthened, and the mixing of the fuel vapor and air and the mixing of the annular air jet can be promoted.

  When the inlet portion of the annular air passage or the inlet portion of the splitter nozzle in addition to this is a radial passage directed in the radial direction, the inlet portion of the annular air passage or the inlet of the splitter nozzle in addition thereto A high degree of freedom is obtained in the design of the part. This is particularly advantageous for application to a counterflow type gas turbine combustor in which combustion air outside the combustion chamber flows in the direction opposite to the direction of the flow of combustion gas in the combustion chamber.

  If the fuel injection valve has a two-fluid injection structure capable of injecting fuel atomization air in addition to fuel injection, the fuel injection valve is injected from the fuel injection valve without requiring separate fuel atomization means. The fuel spray can be adjusted more finely by adjusting the fuel atomization air, and more stable combustion of the fuel can be achieved even when the burner is under no load or low load operation. The fuel atomization air can protect the fuel injection valve from radiant overheating due to the flame, and can prevent coking and evaporation of the fuel in the fuel injection valve.

  When the burner is a burner of a gas turbine device, the air compressed by the compressor driven by the turbine of the gas turbine device is heated by the exhaust of the turbine in the inside of the splitter nozzle and the annular air flow path. If the air compressed by the compressor is supplied without being heated by the exhaust of the turbine, the gas turbine While increasing the thermal efficiency of the apparatus, the temperature rise of the fuel injection valve can be better suppressed, and the coking and evaporation of fuel in the fuel injection valve can be better prevented.

It is a longitudinal cross-sectional view which shows the fuel-injection state of the burner by this invention in some exploded views in the basic burner structure of this invention. FIG. 6 is an exploded longitudinal sectional view showing another embodiment of the burner according to the present invention. 1 is an exploded longitudinal sectional view showing an example in which the fuel injection valve of the burner shown in FIG. 1 has a two-fluid injection structure that can inject fuel atomization air in addition to fuel injection. is there. When the burner is a burner for a gas turbine device and the fuel injection valve has a two-fluid injection structure as shown in FIG. 3, the internal flow path of the splitter nozzle and the annular air flow path are provided by a turbine. The air compressed by the driven compressor is heated by the exhaust of the turbine, and the air for fuel atomization injected by the fuel injection valve is the air compressed by the compressor by the exhaust of the turbine. It is the schematic which shows the gas turbine apparatus which is supplied without being heated.

  As shown in FIG. 1 in the basic structure of the present invention, the burner according to the present invention does not have a multiple fuel injection structure like the conventional pilot fuel injection valve and the main fuel injection valve, but a single fuel. This is due to the injection valve 10. The burner has a single fuel injection valve 10 that injects liquid fuel, a splitter nozzle 12 that coaxially surrounds it, and an outer shroud 16 that coaxially surrounds and forms an annular air flow path 14 therearound. The liquid fuel is supplied to the fuel injection valve 10 and the air is divided and supplied to the internal flow path and the annular air flow path 14 on the outside by the splitter nozzle 12. A swirler 18 is provided at the inlet of the annular air channel 14 as means for applying a turning force to the air flow supplied through the annular air channel 14. In addition, as a means to give the turning force to the air flow, air may be introduced into the air flow path from an air inlet opening that is inclined with respect to the entire axial direction. The splitter nozzle 12 is reduced in diameter toward the outlet end 20. Here, that the diameter of the splitter nozzle 12 is reduced toward the outlet end 20 means that the outlet end 20 does not have a portion whose diameter is increased toward the outlet. As the splitter nozzle 12 is reduced in diameter toward the outlet end 20 in this way, when there is a portion to be enlarged at the outlet end, the fuel liquid film adhering to the vortex of the air flow along the enlarged diameter portion Inconvenience of being rolled up to a large extent and becoming large droplets is prevented.

  According to the structure as described above, by appropriately designing the means (swirler 18 in the illustrated embodiment) for applying a swirling force to the air flow flowing through the fuel injection valve 10, the splitter nozzle 12, and the annular air flow path 14, The fuel injected from the fuel injection valve 10 at the time of medium to high output is ejected at a high flow rate through the outlet end 20 having a reduced diameter of the splitter nozzle 12 together with the air supplied to the internal flow path of the splitter nozzle 12. A combustion flame forming region 22 where the fuel is ignited and becomes a flame can be spaced apart from the outlet end 20 of the splitter nozzle 12 by a predetermined distance, and a flame lift-off region 24 can be formed between which the fuel does not ignite. In this case, the fuel is mixed with a part of the total air supply amount in the splitter nozzle 12 to form a mixture of fuel and air, which has a rich fuel component and can easily hold the flame stably, and the outlet end 20 of the splitter nozzle 12. The fuel component flows in the axial direction, and is mixed with the air flow that flows out while swirling from the annular air flow path 14 around the splitter nozzle 12 to be given a swirling force, and the fuel component is also stirred in the radial direction. Spread. Therefore, if the fuel injection valve 10, the splitter nozzle 12, the outer shroud 16, and a means (swirler 18) for applying a swirling force to the air flow flowing through the annular air flow path are appropriately designed, the fuel is appropriately stored in the flame lift-off region 24. In the combustion flame formation region 22, the flame is stably held, the fuel is uniformly dispersed from the central portion to the outer peripheral portion, and combustion of the fuel without causing hot spots is achieved. Can do.

  On the other hand, at the time of no load or low load, the low flow rate fuel injected from the fuel injection valve 10 gradually passes through the outlet end 20 of the splitter nozzle 12 together with the same low flow rate air supplied to the internal flow path of the splitter nozzle 12. However, since the fuel droplets hardly evaporate because the air temperature is low during no load or low load, the fuel ejected from the splitter nozzle 12 does not diffuse in the radial direction in the flame lift-off region 24. Proceed to the combustion flame formation region 22 as it is, and the fuel does not fall into lean combustion, and burns satisfactorily while suppressing the generation of CO and unburned HC under a sufficiently high flame temperature necessary for stable fuel combustion. Can do.

  FIG. 1 shows the basic structure of the burner according to the present invention as described above. However, the burner may also apply a turning force to the air flow flowing through the internal flow path of the splitter nozzle 12. In addition, the inner peripheral surface of the outer shroud 16 may be reduced in diameter so as to match the shape reduced toward the outlet end 20 of the splitter nozzle 12 in a portion overlapping the splitter nozzle 12 in the axial direction. Further, the inlet portion of the annular air passage 14 or in addition to this, the inlet portion of the splitter nozzle 12 may be a radial passage directed in the radial direction. Such another embodiment of the present invention is illustrated in FIG. FIG. 2A shows an embodiment in which a swirler 26 is provided as means for imparting a turning force to the airflow flowing through the internal flow path of the splitter nozzle 12. In this way, if a swirl force is applied to the air flow flowing through the internal flow path of the splitter nozzle 12, the fuel droplets injected from the fuel injection valve 10 are better atomized and better dispersed in the air flow. The evaporation can be promoted. In this case, in particular, the swirler 26 applies a turning force in the opposite turning direction to the air flow flowing through the inner peripheral portion of the internal flow path of the splitter nozzle 12 and the air flow flowing through the outer peripheral portion. For example, the fuel droplets injected from the fuel injection valve 10 can be better dispersed in the air flow and can not only increase turbulence and promote evaporation, but they also interfere with each other at the outlet of the splitter nozzle 12. Can form a flow substantially free of swirling in the vicinity of the central axis, can lengthen the flame lift-off region 24, and can evaporate and mix fuel droplets there. Although not shown in particular, the swirler 26 can be used to apply a swirl force in opposite swirl directions to the air flow flowing in the inner peripheral portion of the internal flow path of the splitter nozzle 12 and the air flow flowing in the outer peripheral portion. A swirler in which the twist of the blade is reversed between the peripheral portion and the outer peripheral portion may be used.

  2B and 2C of FIG. 2 are reduced in diameter so that the inner peripheral surface of the outer shroud 16 is aligned with the shape reduced toward the outlet end 20 of the splitter nozzle 12 in a portion overlapping the splitter nozzle 12 in the axial direction. The embodiment shown in the case of the basic form of the present invention shown in FIG. 1 and the case where the swirler 26 is also provided at the inlet of the internal flow path of the splitter nozzle 12 are shown. If the inner peripheral surface of the outer shroud 16 is reduced in diameter so as to be aligned with the shape reduced toward the outlet end of the splitter nozzle in the portion overlapping the splitter nozzle 12 in the axial direction, the annular air flow path 14 can increase the flow velocity of the air flow flowing out from the nozzle 14, strengthen the interference with the mixture jet from the splitter nozzle 12, and promote the mixing of the fuel vapor and air and the annular air jet.

  FIG. 2D shows an embodiment in which the inlet portion of the annular air passage 14 is a radial passage oriented in the radial direction, and FIG. 2E shows the inlet portion of the annular air passage 14. In addition, an embodiment is shown in which the inlet portion of the splitter nozzle 12 is also a radial channel directed in the radial direction. In this way, when the inlet portion of the annular air passage 14 or the inlet portion of the splitter nozzle 12 in addition thereto is a radial passage directed in the radial direction, the design of the inlet portion of the annular air passage 14 and the splitter nozzle 12 is designed. High degree of freedom. This is particularly advantageous for application to a counterflow type gas turbine combustor in which combustion air outside the combustion chamber flows in the direction opposite to the direction of the flow of combustion gas in the combustion chamber.

  FIG. 3 shows an example in which the fuel injection valve 10 in the burner structure shown in FIG. 1 has a two-fluid injection structure capable of injecting fuel atomization air in addition to fuel injection. Is shown as an embodiment having a structure having a fuel injection pipe 28 extending along its central axis and a fuel atomization air passage 30 extending around the fuel injection pipe. In this case, the fuel is supplied through a fuel injection pipe 28 provided along the central axis of the fuel injection valve 10, and fuel atomization air is provided around the fuel injection pipe 28. It is supplied through the passage 30. In the illustrated example, the air atomizing air passage 30 is further provided with air flow swirling means 32 for imparting swirling to the air flow flowing therethrough. The fuel injection valve having a two-fluid injection structure capable of injecting fuel atomization air in addition to fuel injection further increases the fuel atomization along the central axis of the fuel injection pipe 28 shown in FIG. An air passage for gasification may be provided, and the fuel jet may be sandwiched between the outer and inner sides of the air flow layer. In any case, since the fuel injection valve 10 has a two-fluid injection structure that can inject fuel atomization air in addition to fuel injection, the injected fuel can be atomized better, and the burner It is possible to achieve more stable combustion of the fuel even during no-load or low-load operation, and to protect the fuel injection valve 10 from radiant overheating due to the flame by such fuel atomization air. Such a change of the fuel injection valve 10 may be similarly applied to the embodiment shown in FIGS.

  4 shows a gas turbine apparatus in which the burner shown in FIG. 3 is assembled in the combustion chamber 34 and combined with the turbine 36, the compressor 38, and the heat exchanger 40, and the internal flow path of the splitter nozzle 12 and the annular air flow path 14 are combined. The air compressed by the compressor 38 driven by the turbine 36 is supplied with the air heated by the exhaust gas of the turbine 36 in the heat exchanger 40, and compressed into the fuel atomization air passage 30 by the compressor 38. FIG. 3 is a schematic view showing a configuration in which air is supplied without being heated by exhaust of a turbine 36. Thus, the air compressed by the compressor and heated by the turbine exhaust is supplied to the internal flow path of the splitter nozzle 12 and the annular air flow path 14, and the air compressed by the compressor is supplied to the fuel atomization air passage 30. Can be supplied without being heated by the turbine exhaust, it is possible to improve the thermal efficiency of the gas turbine apparatus and to better protect the fuel injection valve 10 from radiant overheating caused by the flame and suppress the temperature rise. In addition, coking or evaporation of fuel in the fuel injection valve 10 can be prevented.

  Although the present invention has been described in detail with reference to the basic embodiments and other embodiments, it will be apparent to those skilled in the art that various modifications can be made to these embodiments within the scope of the present invention. I will.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 12 ... Splitter nozzle, 14 ... Annular air flow path, 16 ... Outer shroud, 18 ... Swirler, 20 ... Outlet end of splitter nozzle, 22 ... Combustion flame formation area, 24 ... Flame lift-off area, 26 ... Swirler 28 ... Fuel injection pipe 30 ... Air passage for atomizing fuel 32 ... Air flow swirling means 34 ... Combustion chamber 36 ... Turbine 38 ... Compressor 40 ... Heat exchanger

Claims (7)

  A single fuel injection valve for injecting liquid fuel; a splitter nozzle coaxially surrounding the fuel injection valve and having a diameter reduced toward the outlet end; and an annular air flow around the splitter nozzle coaxially surrounding the splitter nozzle An outer shroud that forms a path, and means for imparting a swirling force to the air flow flowing through the annular air flow path, wherein liquid fuel is supplied to the fuel injection valve, and air is provided to the internal flow path of the splitter nozzle. A liquid fuel burner characterized by being divided and supplied to the annular air flow path.   The burner according to claim 1, further comprising means for imparting a turning force to the airflow flowing through the internal flow path of the splitter nozzle.   The means for applying a swirling force to the air flow flowing through the internal flow path of the splitter nozzle is a reciprocal swirl for the air flow flowing through the inner peripheral portion and the air flow flowing through the outer peripheral portion of the internal flow path of the splitter nozzle. The burner according to claim 2, wherein a turning force in a direction is applied.   The inner peripheral surface of the outer shroud is reduced in diameter so as to match a shape reduced in diameter toward the outlet end of the splitter nozzle in a portion overlapping the splitter nozzle in the axial direction. The burner in any one of 1-3.   The burner according to any one of claims 1 to 4, wherein an inlet portion of the annular air passage or an inlet portion of the splitter nozzle in addition to the inlet portion is a radial passage directed in the radial direction. .   6. The burner according to claim 1, wherein the fuel injection valve has a two-fluid injection structure capable of injecting fuel atomization air in addition to fuel injection.   When the burner is a burner of a gas turbine device, air compressed by a compressor driven by the turbine of the gas turbine device is supplied to the internal flow channel of the splitter nozzle and the annular air flow channel by exhaust of the turbine. Heated air is supplied, and as air for atomizing fuel injected by the fuel injection valve, air compressed by the compressor is supplied without being heated by the exhaust of the turbine. The burner according to claim 6, characterized in that:

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