RU2626887C2 - Tangential annular combustor with premixed fuel and air for use on gas turbine engines - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: method of mixing substances entering the combustion reaction of a gas turbine engine includes the following steps - providing a combustion chamber comprising an outer shell, an inner shell and a perforated front wall, the fuel injectors. The premixed fuel-air mixture is injected in the combustion chamber volume. Reactive substance, injected by fuel and air nozzles, are combusted within mentioned area and create a flow field through the combustion chamber, which rotates around the axis line of the engine. Injected air is coming from the compressor through the perforated front wall. The injection of the mixture is operated through a first series of nozzles disposed adjacent the front wall and having a higher fuel/air ratio than the second set of nozzles with the injection of the mixture downstream of the fuel nozzles, thereby providing the desired mixing and stepped fuel-effect, which in turn, creates optimal conditions for the combustion and reduces NOx and CO emissions from the combustion chamber under partial load and/or full load. Display the hot combustion products from the combustion chamber through the annular opening.

EFFECT: improving the combustion efficiency and reduced emissions of combustion products toxicity.

6 dwg

Description

FIELD OF THE INVENTION

The present invention relates to devices in gas turbine engines, which are intended for the content and combustion of the air-fuel mixture. Such devices include, but are not limited to: air-fuel nozzles, lining and bodies of the combustion chamber, as well as sections of the flow passage used in aircraft of military and commercial purposes, energy generation systems and other areas associated with gas turbines.

State of the art

Gas turbine engines contain mechanisms to extract the work of gaseous products of combustion expiring at very high temperatures, pressures and speeds. The recovered work can be used to drive the generator to generate energy, to drive compressor devices, or to provide the necessary traction for the aircraft. A conventional gas turbine engine consists of a multi-stage compressor in which atmospheric air is compressed to high pressures. Compressed air is then mixed in a certain ratio of fuel / air in the combustion chamber, in which the temperature of the mixture increases. The gaseous products of combustion with high temperature and pressure are then expanded through the turbine to extract work in such a way as to provide the necessary traction or actuate the generator, depending on the application. The turbine contains at least one stage, and each stage consists of a series of blades and a number of blades. The blades are distributed around the circumference of the rotating hub, and the height of each blade corresponds to the path of the flow of hot gas. Each stage of non-rotating blades is located on a circle, which also runs perpendicular to the path of the flow of hot gas. The invention relates to a combustion chamber of gas turbine engines and components for supplying fuel and air to said device.

There are various types of combustion chambers of a gas turbine engine: in the form of a silo, tubular, annular and a combination of the latter two types forming a tubular-annular combustion chamber. Through the specified component, the compressed air-fuel mixture passes through the air-fuel swirls and enters the combustion reaction, creating a flow of hot gas, causing a decrease in the density of the specified mixture and its acceleration downstream. The tube-type combustion chamber usually contains separate, distributed around the circumference of the flame tube, accommodating the flame of each nozzle separately. The flow from each flame tube is then directed through the nozzle and combined in the annular section of the transition, before applying the flow to the first stage of the nozzle guide vanes. In a ring-type combustion cavity, air-fuel nozzles are usually distributed around the circumference and allow the mixture to be introduced into a single annular chamber in which combustion takes place. The stream simply exits through the downstream end of the annular space to the first stage of the turbine, without the need for a transition section. The key difference between the combustion chamber of the latter type, the tubular-annular combustion chamber, is the presence of separate flame tubes surrounded by an annular casing containing air supplied to each flame tube. Each of these types of cameras has its own advantages and disadvantages, depending on the conditions of their use.

In gas turbine combustion chambers, it is common for air-fuel nozzles to introduce turbulence into the mixture for several reasons. Firstly, it improves mixing and, consequently, combustion, and secondly, an additional swirl stabilizes the flame, which prevents flame attenuation and allows the use of poorer air-fuel mixtures to reduce emissions. There are various configurations of fuel-air nozzles, for example, with one or many annular inlets with twisting blades on each.

As for the other components of the gas turbine, cooling is necessary to prevent the melting of the materials of the combustion chamber. The traditional method of cooling the combustion chamber is effusion cooling, implemented by enclosing the lining of the combustion chamber in an auxiliary offset lining, and between the two lining, the air leaving the compressor passes through and enters the duct for hot air through the dilution holes and cooling channels.

Using this technology, heat is removed from the component and a thin boundary layer of cooling air is created between the lining and the gaseous products of combustion, preventing heat transfer to the lining. The dilution holes perform two functions depending on their axial location on the cladding: the dilution hole, located closer to the air-fuel nozzles, helps to mix gases to improve combustion, and also provides fresh air for combustion, and secondly, the hole located closer to the turbine, cools the flow of hot gas, and can be adapted to control the temperature profile at the outlet of the combustion chamber.

It is clear that in order to improve combustion and reduce emissions, many methods and technologies can be implemented in the designs of the combustion chambers of gas turbine engines. Despite the fact that there is a tendency to reduce the formation of pollutants by gas turbines in comparison with other methods of generating energy, there are still opportunities to improve these characteristics. In some countries, government regulation of emissions is tightening, and technology must be improved to meet new requirements.

Disclosure of invention

The present invention provides a new and improved design of a combustion chamber capable of operating normally with a minimum amount of pollutant emissions resulting from the combustion of an air-fuel mixture. The invention comprises a conventional annular combustion chamber with nozzles for a pre-mixed air-fuel mixture and / or dilution holes that introduce air and compressed fuel leaving the compressor into the combustion chamber at various locations in the longitudinal and circumferential directions. A distinctive feature of the invention is the placement of fuel and air inlets, which creates conditions for improved mixing of substances that enter into the combustion reaction, and combustion products. The step pattern of the nozzles for pre-mixed fuel and air to provide more fuel upstream from another set of nozzles located downstream improves the mixing of the combustion substances and creates a certain concentration of oxygen in the combustion area, which can significantly reduce the formation of NO _x . In addition, the introduction of air leaving the compressor downstream of the combustion area allows you to burn / use any amount of CO generated during combustion, before the gas is supplied to the first stage of the turbine. Essentially, the combustion chamber according to the invention reduces the emissions of a gas turbine, thereby reducing the need for emission control devices, and also minimizes the environmental impact of such devices. In addition to the indicated improvement, the tangential ignition of the fuel and the air-fuel nozzles direct their flame to the adjacent burner, significantly improving the ignition process in the combustion chamber, the resulting stream leaving the combustion chamber having a significant peripheral velocity component, which reduces the required size of the first nozzle stage guide vanes.

Brief description of drawings In the drawings:

FIG. 1 is a two-dimensional sketch showing nozzles attached to the outer lining of the combustion chamber and having a circumferential and radial direction in the combustion chamber (a possible longitudinal direction of the nozzle is not shown);

FIG. 2 is an isometric side view of an example of an annular combustion chamber with a proposed stepwise injection of fuel and air;

FIG. 3 is a sectional side elevation in isometry, the plane of which is defined by the center line and radius of the engine;

Fig. 4A is an isometric side view in the direction of the tail portion, which shows a front wall and a perforated front wall, which may contain the present invention;

FIG. 4B is an enlarged view of FIG. 4A;

FIG. 5A is a front isometric view of an embodiment of a combustion chamber in a direction from a tail portion forward, showing outlet and inlet nozzles;

FIG. 5B is an enlarged view of FIG. 5A; and

FIG. 6 is a two-dimensional diagram showing a cross-section of a nozzle of a typical air-fuel nozzle design.

Preferred Embodiments

FIG. 1 illustrates the principal arrangement of an annular combustion chamber with tangentially directed air-fuel nozzles. The combustion chamber consists of an outer shell (or lining) 1, an inner shell (or lining) 2, each of which may have a constant or variable radius in the longitudinal direction, and an outer wall 6 connecting the inner and outer lining 1, 2. As can be seen on to the indicated figure, an example of the construction of the invention comprises nozzles 3 of pre-mixed fuel and air directed mainly in the circumferential direction, and an angle of 10 is formed between the line 8 tangent to the outer lining and the center lines 9 of the nozzles 3, n o in addition to the specified direction may also contain a radial or longitudinal component. These various nozzles 3 may be in a common plane defined by a longitudinal direction and a point on the axial line of the engine, and may be evenly distributed around the circumference or have a different distribution pattern in this direction. These nozzles inject a pre-mixed air-fuel mixture 4 into the volume of the combustion chamber formed by the indicated inner and outer shell 1, 2 and the front wall 6. The reacting substances injected by the fuel and air nozzles 3 are burned inside the specified region and create a flow field 5 through the chamber combustion, which rotates around the centerline of the engine. Said nozzles through which fuel, air or pre-mixed fuel and air pass have the typical construction shown in FIG. 6. The circular region 12, coaxial with the nozzle, encloses a region that can hold the axial swirler and / or starting fuel / air nozzles. The concentric annular flow channel 11 can give air or pre-mixed air-fuel mixture swirl in the range from small to zero. A minimum swirl, if one is provided at all, is communicated to the stream through the annular channel to achieve a substantial tangential velocity of the stream entering the combustion chamber. This configuration allows the flow to maintain the maximum value of the peripheral velocity component at the outlet of the combustion chamber, which reduces the required length of the blades of the first stage of the turbine.

In FIG. 2 shows an example construction of the invention in which fuel nozzles 3 are arranged upstream (to the left) of a second set of fuel air nozzles that are in a common plane and distributed around a circle. One or more fuel injectors 3 may be provided, up to an unlimited number thereof. The air leaving the compressor can also be introduced into the volume of the combustion chamber through the perforated front wall 6, as shown in FIG. 3, 4A and 4B. The injection of the mixture through the first row of nozzles located near the front wall, which may have a higher fuel / air ratio than the second set of nozzles, together with the injection of the mixture downstream of the fuel nozzles 3, provides the required mixing and stepwise air-fuel effect, which, in its in turn, it creates optimal combustion conditions and reduces the emissions of NO _x and CO from the combustion chamber under conditions of partial loading and / or full loading. The hot combustion products then leave the combustion chamber through the annular opening 7, as shown in FIG. 5A and 5V, where they enter the first stage of the gas turbine.

The present invention is disclosed above with reference to a preferred embodiment. However, one skilled in the art will appreciate that various changes and modifications of the disclosed embodiment of the invention can be made without departing from the spirit and scope of the legal protection of the present invention. Various changes and modifications to the embodiment selected herein to illustrate the invention are apparent to those skilled in the art. If such modifications and variations do not go beyond the essence of the invention, they should be included in the scope of legal protection of the invention.

The invention is fully disclosed in clear and understandable terms so that a person skilled in the art can understand and put into practice this invention. The claims of the present invention are given below.

Claims (8)

A method of mixing combustion substances for a gas turbine engine, comprising the following steps: provide a combustion chamber containing: the outer shell (1), the inner shell (2) and the perforated front wall (6), which connects the outer shell (1) and the inner shell (2), forming the volume of the combustion chamber, and the annular space (7); fuel nozzles (3) located upstream of the second set of fuel air nozzles, which are in a common plane and distributed around the circumference; introducing a pre-mixed air-fuel mixture into the volume of the combustion chamber, the reacting substances injected by the fuel and air nozzles (3) are burned inside the specified area and create a flow field (5) through the combustion chamber, which rotates around the center line of the engine; the air leaving the compressor is injected through the perforated front wall (6); the mixture is injected through the first row of nozzles located near the front wall and having a higher fuel / air ratio than the second set of nozzles, together with the injection of the mixture downstream of the fuel nozzles (3), thereby providing the required mixing and a stepwise air-fuel effect, which, in turn, creates optimal combustion conditions and reduces the emissions of NOx and CO from the combustion chamber under conditions of partial loading and / or full loading; and then hot products of combustion are removed from the combustion chamber through an annular opening (7).

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