JP5896443B2 - Fuel nozzle - Google Patents

Description

  The present invention relates to a fuel nozzle used in a combustor of an aircraft jet engine.

  Aircraft jet engine combustors operate over various power levels such as idle, takeoff and cruise, but at any stage they must be designed to reduce fuel consumption and harmful substances in the exhaust. It is done. In a conventional aircraft jet engine combustor, as a technique for reducing nitrogen oxides (NOx), a rich quench lean combustion system (RQL combustion system) by diffusion combustion or the like is used. In the RQL combustion method, a large amount of NOx is generated by combustion with an equivalence ratio close to 1, so that combustion is performed in a fuel rich (equivalence ratio> 1) upstream of the combustor and then air is rapidly introduced In this way, combustion is performed with a lean fuel (equivalence ratio <1) to suppress NOx to a low level.

  For the purpose of providing an improved combustor having appropriate durability by reducing harmful substances in exhaust gas, Patent Document 1 presents a low emission combustor of the RQL combustion type. The combustor is a single annular combustor 110 disposed within an annular casing 112 in an aircraft turbofan engine, as shown in FIG. The combustor is axisymmetric with respect to a longitudinal or axial central axis 114 and receives pressurized air 116 from a compressor (not shown), which is mixed with fuel 118 and ignited, Hot combustion gas 120 is generated and the combustion gas is discharged from the combustor into a conventional turbine stage that includes a high pressure turbine nozzle 122. The combustor includes radially outer and inner annular combustor liners 124, 126 that are joined at their forward ends to an annular dome 128 and radially spaced at their rear ends. To define an annular combustor outlet 130. A plurality of circumferentially spaced fuel nozzles are suitably mounted through the dome. The fuel nozzle comprises a conventional fuel injector 132 and a cooperating air swirler or swirl cup 134. Each swirl cup is suitably attached to the dome to receive the respective fuel injector coaxially and swirls the air to produce a fuel / air mixture that is combusted within the combustor. It is configured to be mixed with fuel from

  As part of the Aero Engine Environmental Technology Research and Development (TechCLEAN), our environment-adapted engine team is currently reducing the nitrogen oxide emission value of aircraft engines to 20% of the CAEP4 standard value of the International Civil Aviation Organization (ICAO). Research and development of advanced combustion technology is being promoted with the goal of reducing the following. In the future, it is inevitable that the pressure ratio will increase in order to reduce fuel consumption. In the RQL combustion method described above, NOx and smoke emissions tend to increase rapidly. In order to solve this problem, research and development of a staging type fuel nozzle that uses a diffusion combustion system as a pilot fuel injection section and a premixed combustion system as a main fuel injection section has been actively conducted. The staging type fuel nozzle is a premixed gas formed by a main fuel injection unit that operates at a low load such as an engine idle by a combustion generated by the operation of the pilot fuel injection unit and operates at a medium load to a high load. By using it as a spark for stably burning, NOx in the exhaust gas can be reduced and combustion efficiency can be improved.

In the staging type fuel nozzle, Patent Document 2 proposes an invention aimed at providing a fuel injection device that more effectively suppresses the generation of pollutants while preventing deterioration of the durability of a gas turbine engine. Yes. As shown in FIG. 5, this content is a fuel injection device including a pilot fuel injection unit 1 and a main fuel injection unit 10, wherein the pilot fuel injection unit 1 includes an inner fuel chamber forming body 111, An inner oil film forming body 13 disposed around the inner fuel chamber forming body 111, an inner air flow path 113, and an inner wall 114 surrounding the inner oil film forming body 13 and forming the outer periphery of the inner air flow path are provided. Then, the fuel injected from the inner fuel chamber 111a of the inner fuel chamber forming body 111 to the inner surface of the inner oil film forming body 13 is converted into an oil film on the inner surface of the inner oil film forming body 13 and sent downstream. The fuel is discharged from the side tip 13a in the form of a film, and the fuel released in the form of a film is atomized by the air flow in the inner air flow path 113 and sent to the combustion region.
However, since the staging type fuel nozzle injects only the pilot fuel when the engine is under a low load, the combustion efficiency tends to decrease due to mixing with air flowing into the combustor through the main injection portion. In order to reduce this, a conical depression (hereinafter referred to as flare) is provided and a pilot flame is formed here, but the injected fuel adheres to the flare surface and atomization worsens, There are disadvantages in that the combustion efficiency is reduced, smoke is generated, and the lean limit is deteriorated.

  The problems of the present invention are as follows: (1) problems of deterioration of combustion efficiency due to fuel adhering to the pilot flare of the staging type fuel nozzle, generation of smoke, deterioration of the lean limit, (2) pilot fuel injection section It is an object of the present invention to provide a fuel nozzle that solves the problem of reduction in combustion efficiency due to the mixture of the fuel and air and the air that has passed through the main fuel injection section.

In the fuel nozzle of the present invention, the gas flow path surrounding the fuel injection section in an annular shape is in the vicinity of the fuel injection position, and at the downstream end of the flow path area reduction section downstream of the swirler, A step-shaped recess shape that is formed with a flow passage area enlargement portion (flare) following the throat portion on the downstream side of the throat portion, and between the throat portion and the flare in the vicinity of the fuel injection position abruptly increases the flow passage area. Thus, it has a function of preventing the fuel from adhering to the flare wall surface by forming a recirculation airflow in the depression region.
In addition to the above-described configuration, the fuel nozzle of the present invention employs a configuration in which a flow path through which air is introduced from the outside is provided in the flare region as a more preferable form.
In addition, the fuel nozzle of the present invention is of a staging type in which the gas flow path surrounding the fuel injection section in an annular shape is formed by an inner wall and the main fuel injection section is provided around the gas flow path.
Furthermore, the staging type fuel nozzle of the present invention forms a flow path that guides air from the upstream of the pilot and main swirler, which is a high total pressure region, to the back surface of the flare and ejects from the inner wall near the main flow path outlet. Present.

In the fuel nozzle of the present invention, a gas flow path surrounding the fuel injection section is formed by a throat part and a flare downstream of the throat part, and the area between the throat part and the flare is rapidly expanded. Since the recirculation airflow is formed in the depression region, the fuel sprayed from the injection unit is attached to the wall surface of the gas flow path by the recirculation airflow generated in the depression region. Equipped with a function to prevent effectively.
Further, in the fuel nozzle of the present invention in which the depression shape whose flow area is suddenly enlarged is a stepped form, separation of the flow occurs, and a recirculation airflow is generated in the depression region. This recirculation airflow effectively prevents the fuel sprayed from the injection part from adhering to the wall surface of the gas flow path, similarly to the above-described hollow shape in which the flow path area rapidly increases.
Further, in addition to the above-described configuration, the fuel nozzle of the present invention adopting a configuration in which a flow path through which air is introduced from the outside is provided in the flare region as a more preferable form is attached to the surface of the recess, It is also effective in preventing the generation of flames in the depression when there is a decrease in the air flow rate.

In addition, the gas flow passage that surrounds the fuel injection portion in an annular shape is formed of an inner wall, and the fuel nozzle of the present invention that is a staging type having the main fuel injection portion around it has a reduction in combustion efficiency due to adhesion to the pilot flare, Not only can smoke and deterioration of the lean limit be effectively prevented, but when the main fuel is stopped, only air is ejected from the main air flow path and there is no flame. If this is mixed, it will flow downstream without burning, causing a phenomenon that the combustion efficiency is reduced.However, by adopting this configuration, the fuel adhering to the flare is not sufficiently atomized. It is possible to solve the problem of reduction in combustion efficiency due to being discharged from the combustor without being mixed with air and combusted.
Furthermore, the staging type fuel of the present invention is provided with a configuration in which air is led from the upstream of the pilot and main swirler, which is a high total pressure region, to the back surface of the flare, and a flow path is formed from the inner wall near the main flow path outlet. The nozzle is important for cooling the pilot flare and flame holder that are in direct contact with the flame by this air flow, so that they do not burn out, as well as atomization of fuel adhering to the inner inner wall of the main fuel flow path and air Has the effect of promoting mixing with.

It is the figure which showed the whole structure of the fuel nozzle which concerns on this invention. It is the elements on larger scale near the pilot fuel injection part in the fuel nozzle concerning the present invention. It is the elements on larger scale near the main fuel injection part in the fuel nozzle concerning the present invention. It is the elements on larger scale near the hollow part air flow path in the fuel nozzle which concerns on this invention. It is a figure which shows the example of the conventional staging type fuel nozzle. It is a figure which shows the example of the fuel nozzle of the conventional RQL combustion system.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a diagram showing the overall structure of a fuel nozzle according to the present invention. This fuel nozzle is a staging combustion type fuel nozzle having a pilot fuel injection section 1 and a main fuel injection section 10. A combustion chamber is arranged in the right direction (downstream side) of the figure and is configured as a combustor. Before explaining the technology that solves the problems of combustion efficiency reduction, smoke generation, and deterioration of the lean limit due to the adhesion of fuel to the pilot flare of the staging fuel nozzle, which is the subject of the present invention, the operation as a fuel nozzle This will be described in advance. First, the pilot fuel injection will be described with reference to FIG. 2. The pilot fuel is supplied from the pilot fuel supply pipe 11 of FIG. 1 and sent out to the inner surface of the inner oil film forming body 13 through the flow path 12. Since the first swirler 14a and the second swirler 14b are disposed in the flow path 12, the pilot fuel is swirling, and the inner oil film forming body 13 is formed by the centrifugal force downstream of the swirler 14b. A liquid film is formed on the inner surface. On the other hand, since the swirler 16 is disposed in the central first air flow path 15, the air supplied thereto is also given a rotational force and proceeds in the right direction as a swirling flow. The air flow reaches the opening 15a of the air flow path, and this swirling air flow widens the flow path toward the inner surface of the inner oil film forming body 13. The air flow is formed on the inner surface of the inner oil film forming body 13 as a liquid film. The pilot fuel that is sent in the form of a thin film is further thinned by centrifugal force. The thinned pilot fuel reaches the tip of the inner oil film forming body 13, and this time, the second air sent through the second air flow path 17 arranged outside the inner oil film forming body 13. It will come into contact with the flow. Since the swirler 18 is disposed in the second air flow path 17, the air supplied here is also given a rotational force. Therefore, the thinned pilot fuel is atomized by the swirl flow on both sides in a form sandwiched by the inner first air flow and the second air flow from the outer side at the tip of the inner oil film forming body 13, It is scattered in the right direction. The above is the pilot fuel injection operation in the present invention.

  Next, the main fuel injection operation in the present invention will be described with reference to FIG. The main fuel is supplied from the main fuel supply pipe 21 in FIG. 1 and is ejected from the injection port 22 toward the inner surface of the outer oil film forming body 23. A third air flow path 24 is formed inside the outer oil film forming body 23, and a swirler 25 is disposed on the upstream side of the injection port 22, so that the air flow flowing through the third air flow path 24 Is given a rotational force and is sent to the right in the drawing. The main fuel ejected toward the inner surface of the outer oil film forming body 23 receives the centrifugal force of the swirling air flow, and is sent to the right while being pushed and expanded in the form of a liquid film on the inner surface of the outer oil film forming body 23. The main fuel in the form of a liquid film reaches the tip of the outer oil film forming body 23, and this time, the fourth fuel is sent through the fourth air flow path 26 disposed outside the outer oil film forming body 23. It will come into contact with the air flow. Since the swirler 27 is arranged in the fourth air flow path 26, the air supplied here is also given a rotational force. Therefore, the main fuel formed into a liquid film is atomized by the swirl flow on both sides in a form sandwiched between the inner third air flow and the fourth air flow from the outer side at the tip of the inner oil film forming body 13. , Scattered rightward. The above is the main fuel injection operation in the present invention.

  Now, the problems of reduction in combustion efficiency, generation of smoke, and deterioration of the lean limit due to the fuel adhering to the pilot flare of the staging type fuel nozzle, which are the subject of the present invention, will be described. When a fuel nozzle is used in a combustor of an aircraft jet engine, fuel is injected only by a pilot fuel injection unit when the engine is under a low load, and diffusion combustion is performed. A flare (flow passage area enlargement part) is provided downstream of the pilot fuel injection part for the stability of the pilot flame, but the sprayed pilot fuel adheres to the flare surface, resulting in combustion efficiency. Phenomena occur that lead to lowering, generation of smoke, and deterioration of the lean limit. The present invention presents a configuration for preventing sprayed pilot fuel from adhering to the flare surface.

A fuel nozzle according to the present invention is a pilot fuel injection unit that atomizes and sprays a thinned pilot fuel by a swirling flow on both sides in a form sandwiched between a first air flow inside and a second air flow from the outside. 4, the gas flow path 2 surrounding the tip of the inner oil film forming body 13 in an annular shape as shown in a partially enlarged view in FIG. 4, the throat part 4, and the downstream side of the throat part. Although it is formed with the flare 5, it is set as the level | step difference form from which the said throat part 4 and the flare 5 expand the flow path area rapidly. Thereby, the recessed region 6 is formed on the downstream side of the step. Of the air flow flowing through the second air flow path 17, the air flow close to the outer wall surface flows smoothly along the wall surface up to the throat portion 4, but is forcibly separated from the wall surface at the step portion. As a result, a vortex flow as shown in the figure is generated in the depression region 6, and a recirculation airflow is formed in the depression region 6. By generating a stable recirculation airflow, the sprayed pilot fuel can be greatly reduced from adhering to the surface of the flare 5.
Further, in the embodiment of the present invention shown in the figure, the cooling air flow that guides air from the upstream side of the pilot and main swirler, which is a region having a high total pressure, to the back surface of the flare and ejects it from the inner wall near the main channel outlet. A form for forming the path 8 is presented. Further, a flow path 9 is provided for communicating the recessed area 6 from the cooling air flow path 8. Since the air pressure in the cooling air flow path 8 is higher than the air pressure in the recessed area 6, air naturally flows from the cooling air flow path 8 into the recessed area 6. This is effective for preventing the formation of a flame in a dent when there is adhesion or a sudden decrease in the air flow rate.
In the embodiment shown here, the gas flow passage surrounding the pilot fuel injection portion in an annular shape is a staging type having an inner wall and a main fuel injection portion around the gas flow passage. Even a general fuel nozzle that is not necessarily limited to a staging type fuel nozzle is effective in the effect that fuel does not adhere to the flare surface.

  Further, in the fuel nozzle of the above embodiment having the coaxial pilot fuel injection part and the main fuel injection part, a configuration in which the rear step flame stabilizer 7 is provided between the pilot flare rear end and the main flow path is adopted. In addition to the recirculation flow formed in the center of the pilot fuel injection unit, flame holding is also performed around the flame, and combustion is improved by mixing before mixing with the air that has passed through the main injection unit In addition, when the main fuel is injected, the main premixed gas can be reliably brought into contact with the pilot flame or the high-temperature burned gas generated by the pilot flame. In addition, air is guided from a high pressure position (upstream of the swirler of the pilot fuel injection unit and the main fuel injection unit), the pilot flare 5 and the rear step flame stabilizer 7 are cooled from the back surface, and the inside near the outlet of the main flow path By providing a structure that blows out in the form of a film from the wall, the pilot flare and flame holder that come into direct contact with the flame are cooled and played an important function to prevent burning, and to the inner wall of the main fuel flow path It has the effect of promoting atomization of adhering fuel and mixing with air.

  The present invention is applicable to gas turbine combustors, boilers, etc. that perform continuous combustion using liquid fuel. Further, the present invention can be applied to an apparatus that performs atomization of liquid and mixing with gas.

DESCRIPTION OF SYMBOLS 1 Pilot fuel injection part 2 Gas flow path 4 Throat part 5 Flare 6 Indentation area 7 Back step flame stabilizer 8 Cooling air passage 9 Communication flow path
10 Main fuel injection section 11 Pilot fuel supply pipe
12 Channel 13 Inner oil film forming body
14a First swirler 14b Second swirler
15 First air flow path 16 Swirler
17 Second air flow path 18 Swirler
21 Main fuel supply pipe 22 Injection port
23 outer oil film former 24 third air flow path
25 Swirler 26 4th air flow path
27 Swirler

JP 2001-1147018 "Low Emission Combustor" Released on May 29, 2001 JP, 2004-226051, A "Fuel injection device" Published on August 12, 2004

Claims (4)

The gas flow path that surrounds the fuel injection section in an annular shape is near the fuel injection position, the throat formed at the downstream end of the flow path area reduction section downstream of the swirler, and the throat downstream of the throat Is formed in a step-shaped recess shape in which the space between the throat and the flare abruptly increases in the vicinity of the fuel injection position. A liquid fuel nozzle having a function of preventing fuel from adhering to a flare wall surface by forming a recirculation airflow.   The fuel nozzle according to claim 1, wherein a channel through which air is introduced from the outside is provided in the flare region.   3. The fuel nozzle according to claim 1, wherein the gas flow path surrounding the fuel injection portion in an annular shape is a staging type having an inner wall and a main fuel injection portion around the gas flow passage.   Air is led from the upstream side of the pilot and main swirler, which is a region with high total pressure, to the back surface of the flare, and a flow path is formed to be ejected from the inner wall near the main flow path outlet. The fuel nozzle according to claim 3, comprising a function.

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