JPH0240418A - Gas turbine burner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas turbine combustor, and in particular, to expansion of premix combustion that dominates the reduction of nitrogen oxides (No.) and stable combustion. The present invention relates to a low NOx two-stage combustor.

[Conventional technology]

Conventional low NOx combustor (low NOx for combined plants)
x Development of Gas Turbine Combustor The 14th Proceedings of the Gas Turbine Society (1987) P51-56) is a two-stage combustion system in which diffusion combustion is performed at the head of the combustion chamber and premix combustion is performed at the rear.

In the second stage premix combustion, combustion continues due to the heating action of the upstream diffusion flame. The premixing nozzle part of this combustor is
Fuel is injected into the air flowing through the annular flow path to create a combustible mixture, which is introduced into the combustion chamber via swirl vanes. Therefore, the flame stabilizing mechanism is achieved by a relatively weak vortex formed on the back side of the swirl vane.

[Problem to be solved by the invention]

A conventional flame holding mechanism for premix combustion is a mechanism that holds a flame by a vortex region formed in the inner and outer circumferential directions on the back side of a swirling vane. However, the strength of the vortex flow is relatively small, so in lean combustion or high-speed flow load zones, the flame may flow excessively (lift phenomenon), and at high loads, the flame may pulsate, resulting in oscillatory combustion. becomes a factor. In addition, as a means of stabilizing the flame, increasing the thickness of the swirl vanes that serve as flame stabilizing plates can improve flame stabilization performance by expanding the vortex region, but the temperature of the swirl vanes increases. The reliability of the combustor decreases due to non-uniformity of the flame due to thermal deformation. Furthermore, the cooling structure of the swirl vane has problems such as complicating factors and restrictions on manufacturing structure.

An object of the present invention is to provide a gas turbine combustor that is capable of stable premix combustion even under lean conditions and high speed conditions that are advantageous for reducing NOx.

[Means for solving division problems]

In the present invention, the side wall of the main chamber adjacent to the outer peripheral side of the outlet of the premixing swirler is inclined and reduced toward the wake side in order to correspond to the premixing jet flow, and furthermore, the side wall continuous to the wake side is rapidly expanded and reduced. Install a recess with a slightly enlarged annular wall surface. That is, the premixed jet is forcibly pushed and bent to expand the circulating flow region on the downstream side.

In general, flame maintenance is achieved by using a low-velocity flow within a circulating flow region to allow sufficient chemical reaction time to promote the combustion reaction and form a small flame at the base of the most turbulent flow to continue combustion.

Therefore, enlarging the circulating flow area is an important factor in improving flame holding performance.

In particular, the method of bending a part of the mainstream of the premixture toward the flowing high-temperature gas side and forming a circulating flow on the downstream side can also be expected to have a heating effect on the premixture, achieving stable flame stability. . Additionally, since a flame-holding mechanism is installed on the side wall of the main combustion chamber, cooling air can be secured and the structure can be manufactured easily.

[Effect]

When the premixed jet hits the reduced part forming the recessed part, it flows along the reduced angle θ, and separates into a flow depending on the relative speed ratio of the velocity from the minimum reduced part to the central part and the mainstream velocity of the premixed jet. occurs, and a circulating flow occurs on the downstream side. The size of the circulating flow region formed on the downstream side here depends on the separation point of the flow, but the separation point moves further from the minimum reduction part to the center due to the influence of the jet flow due to the reduction angle θ. Therefore, the circulating flow area expands toward the center and downstream of the combustion chamber compared to the actual shape of the recess. This circulating flow region is a low-velocity flow and contains many turbulent components, which acts extremely effectively to promote the combustion reaction, so that combustion can be improved using this region as a starting point. Therefore, under conditions where the premixture flows at high speed, it is most important to expand the circulating flow region, and this is a major factor in improving flame holding performance.

〔Example〕

FIG. 1 shows an overall configuration diagram of a two-stage combustor having the structure of the present invention. In a gas turbine combustor consisting of an outer cylinder 1, an inner cylinder 2, and a transition cylinder 3, a sub-combustion chamber 4 and a main combustion chamber 5 having a larger diameter than the sub-combustion chamber 4 are installed at the head of the inner cylinder 2. At the center of the combustion chamber 4, an inner cylinder cone 6 protrudes from the head, and pipe-shaped first stage fuel nozzles 7 having fuel injection holes protrude from the annular hollow part thereof and are arranged in a circumferential manner. Furthermore, a swirler 8 is installed in the enlarged portion of the auxiliary combustion chamber 4 and the main combustion chamber 5, and the inner and outer walls of the swirler 8 are extended upstream to form an annular air flow path 9. A large number of second-stage premixed fuel nozzles 10 are arranged on the upstream side. Further, a recessed portion 15 is formed on the main chamber side wall 11 near the outlet of the swirler 8 on the downstream side by a combination of a contracting portion 12, a rapidly expanding portion 13, and an annular portion 14, and further, a double wall layer is formed. It has an air-cooled structure.

During operation of this combustor, air 16 from the compressor is introduced from the rear part of the transition piece 3, diluted air hole 17, cooling air 18 on the outer wall of the main combustion chamber, premixed air 19, and cooling air 2 on the wall of the sub-combustion chamber.
0, combustion air 21 and inner cylinder cone cooling air 22 are made to flow into the combustion chamber.

The fuel 23 is introduced into the auxiliary combustion chamber 4 from the first stage fuel nozzle body 24 through a plurality of pipe-shaped fuel nozzles 7, and is combusted while being diffused and mixed with the combustion air 21. First stage fuel 2
The operating range of No. 3 is equivalent to 25% of the turbine load from the time of ignition, and 50% of the total fuel flow rate.

The second stage fuel 25 is supplied to the swirler 8 from a fuel chamber 27 connected to an outer cylinder flange 26 via a premixed fuel nozzle 10.
is introduced into the main combustion chamber 5 and mixed with the premixed air 19.
The turbine is operated within the range of 25% to 100% turbine load. Especially when switching fuel at 25% turbine load,
The first stage fuel 23 is reduced in steps from 50% to 25% of the total fuel flow rate, the second stage fuel 25 is introduced in steps of 25%, and then the proportion of the first stage and second stage fuel is reduced. is introduced at a flow rate commensurate with the turbine load band, and is operated at a ratio of 40,760 to the total fuel during rated operation.

FIG. 2 is an enlarged vertical sectional view of the flame stabilizing structure of the second stage premix combustion of the present invention.

The main chamber side wall 11 adjacent to the seal member 28 is provided on the outer peripheral side of the outlet of the premixing swirler 8, and a reduced portion 12 is provided on the downstream side at an inclination angle of θ so as to correspond to the premixing swirling jet flow 29. ,
A recessed portion 15 is formed by forming a rapidly expanding portion 13 and an annular portion 14 on the side wall that continues to the wake. Further, a hollow space gap 30 is provided on the outer wall of the contracting and expanding annular portion, an outer frame 31 is installed so as to form a double layer, and the upstream end where the hollow layer is formed is sealed;
The downstream end has an open structure, and cooling air holes 32 are provided in the outer frame 31 near the contracting portion and the rapidly expanding portion. Therefore, in order to form a flow in which a part of the premix swirl jet 29 is pushed and bent by the contracting part 12 at an angle of θ toward the central part 33 of the main combustion chamber 5, the rapidly expanding part 13 and the annular part 14 Recessed part 15
The region of the circulation flow 34 induced in the interior is apparently expanded.

Since the circulation flow 34 becomes a low-velocity flow, the combustion reaction is promoted, and a mainstream flame 35 is formed from the rapidly expanding portion 13 in the direction of the decreasing inclination angle θ. In particular, since the minimum reduction part that becomes the flame base tends to become a high-temperature wall, the cooling air holes 32 provided in the outer frame 31 installed through the hollow layer are of the impingement cooling type mainly in the vicinity of the minimum reduction part, and the rear recess is used. Since the structure allows cooling of the parts, effective cooling can be achieved.

〔Effect of the invention〕

According to the present invention, stable combustion of a premixed swirling jet flame is possible under high-speed flow. Therefore, it is possible to expand the range of premixed combustion and achieve leaner combustion, thereby providing a combustor that is advantageous in reducing NOx.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a gas turbine combustor according to an embodiment of the present invention, and FIG. 2 is an enlarged longitudinal sectional view of the second stage premixing swirler section and flame holding structure of FIG. 1. 12... Main chamber side wall contraction part, 13... Main chamber side wall rapid expansion part, 14... Main chamber side wall annular part, 15... Recessed part, 3
0.Middle space gap, 31..Outer frame, 32..Cooling air hole, θ..Reduction part inclination angle.

Claims (1)

[Scope of Claims] 1. The combustor inner cylinder is constituted by a main chamber having a diameter larger than the head of the sub-chamber, and a first-stage fuel nozzle is provided at the head of the sub-chamber, and a fuel nozzle of the first stage is provided from the sub-chamber. In a gas turbine combustor, a second-stage fuel introduction mechanism is provided in an enlarged portion connected to the main chamber, and a premixture is supplied into the main chamber via a swirler, the main chamber on the outer peripheral side of the exit of the swirler. The side wall protrudes in an inclined manner to a position corresponding to the jet of the swirler, and furthermore, a recess is formed from the minimum contraction part to the wake side by a rapidly expanding part and an annular part, and a part of the premixed jet is used for main combustion. A gas turbine combustor characterized in that the circulating flow region is ejected toward the center of the chamber and is induced in the recessed portion. 2. In claim 1, in the recessed portion near the second-stage premixing swirler, an outer frame is installed with a gap along the shape of the recessed portion, and the two-chamber wall is formed. The upstream side of the hollow layer is sealed, and the downstream side is opened into the combustion chamber, and cooling chamber air holes are arranged in multiple stages based on the outer frame portion corresponding to the minimum reduction portion of the recess portion, and the combustor A gas turbine combustor characterized in that the cooling air is jetted against the outer wall of the recessed portion due to the differential pressure between the inside and outside of the combustor, and the cooling air is discharged to the downstream side where it does not impede the circulation flow of the recessed portion.