RU2687475C1 - Small-emission circular combustion chamber for gas turbines - Google Patents

Abstract

FIELD: turbines or turbomachines.SUBSTANCE: low-emission annular combustion chamber for gas turbines comprises a cylindrical thin-wall outer housing and a cone-shaped thin-wall inner housing in the form of a flue for exhaust of exhaust flue gases at the outlet of the turbine impeller, which are rigidly connected to each other by welding using a thin-sheet shell. Shell is made in the form of a toroid truncated along the main meridian. External, internal housings and shell are made of heat-resistant metal or alloy. At least eight hollow braces of adjustable length are installed radially between inner and outer casings. Each spacer consists of hollow tube with holes. Holes are staggered along the entire length of the surface and over a width equal to the radial sector of spreader from 30 to 60°. Spacers are fixed on one side by a shaped washer with locating pins, and on the other side with adjusting threaded bushing fixed with lock nut. Invention makes it possible to provide cooling of working medium flow, to reduce temperature of nozzle grid, to maintain repairability of labor-consuming and expensive CS.EFFECT: invention is aimed at improvement of efficiency of combustion chamber, ensuring complete combustion of fuel with simultaneous reduction of temperature of combustion products and reduced emission of NO, CO, CO, elimination of combustion chamber warping and increased durability.1 cl, 4 dwg

Description

The invention relates to annular combustion chambers (CS) of gas microturbines of increased efficiency and durability.

From the technique known annular combustion chamber of a gas microturbine Capstone C-200 manufactured in the USA, which is a countercurrent chamber that converts the chemical energy of gaseous fuel into thermal energy of the working fluid, adopted as a prototype (http://meteoenergetic.ru/mikroturbiny-capstone). Ring CS is the most lightweight, compact and located between the compressor and the impeller around the turbine rotor (Fig. 1, Fig. 2).

The disadvantages of the prototype:

1. High temperature of combustion products is accompanied by increased levels of harmful emissions in the flue gases NO _X , CO, CO ₂ .

At high temperatures, the strength and modulus of elasticity of the metal constituting the CS structure decrease, which may lead to the loss of stability of the cylindrical CS shell and deformations of FIG. 2, to the burning of the nozzle (power head) of the CS body, damage to the blades of the working turbine and to the fatal failure of the entire turbine.

2. Mutual influence of the working fluid flows formed in the adjacent burners, especially when switching on and off, as power sets and drops, creates turbulence with the occurrence of interacting flows of working fluid and the formation of reverse combustion through the air windows of the mixing chambers of the flame tubes of gas burners. Claps caused by the damaging effects of fast moving high-pressure fronts, especially when ignited local accumulations of combustible gas and mixtures in niches and openings, lead to a distortion of the CS, FIG. 2. This leads to a violation of the mutual arrangement of the articulated joints, namely gas burners, spark plugs, the junction of the nozzle head with the chimney seat (not shown in Fig. 2), etc., ensuring the normal functioning of the microturbine. The change in the relative position of the elements of the flow-through hot part leads to turbine failure.

3. Through-hole ejection holes in the outer casing of the standard CS (not shown in Fig. 2), made of different diameters and in different places. However, they do not provide the specified requirements for the ejection of fresh air into the internal cavity of the combustion chamber, necessary for the burning of combustible active gas components that did not have time to burn due to the lack of homogeneity of the combustible mixture and the lack of air. In addition, fresh air is required for partial cooling of the working fluid to ensure the operating temperature regimes of the nozzle grille and turbine impeller blades. Small-sized holes inject air into the wall layer due to its blowing off by the high-speed flow of the working fluid. At the same time, in transients due to pressure fluctuations inside the chamber, combustion products and flames slip in the opposite direction, as evidenced by traces of soot (soot) outside the CS body in the direction of the burners, which can cause ignition of the accumulated gas with the creation of a shock wave.

4. Creating areas with enriched and depleted zones in conditions of insufficient homogeneity of the combustible mixture and with insufficient air in the combustion chamber leads to incomplete combustion of fuel, reducing the efficiency of the gas turbine and disrupting the ecology of the environment.

An object of the invention is to increase the efficiency and resource of the combustion chamber and the reduction of nitrogen oxides NO _x in the flue gases by increasing resistance to warping, preserving the geometric dimensions, ejection of fresh air into the combustion chamber with the exception of flame leakage outside the CS body.

The solution of this problem is achieved by the fact that the improved combustion chamber additionally contains hollow perforated heat-resistant struts of cylindrical shape of adjustable length, providing additional rigidity to the combustion chamber, preserving the geometric dimensions of the flow passage between the outer cylindrical body of the combustion chamber and the inner conical body, which is the smoke tube of the turbine.

The technical objective is achieved by the fact that low-emission ring

Combustion chamber for gas turbines, containing a thin-walled cylindrical outer casing, a cone-shaped inner casing in the form of a socket for exhaust exhaust gases at the exit of the turbine impeller, interconnected by means of a thin-walled, truncated toroidal shell shape by welding, the listed and additional elements of the combustion chamber are made of heat-resistant metal or alloy, and between the inner and outer housings in the annular gap, eight are additionally installed radially or more hollow spacers of adjustable length. Each strut consists of a hollow tube with holes, the size of the diameter of each hole is less than 1.2 mm, providing an obstacle for the passage of fire from the combustion chamber in the opposite direction. The holes in the tubes are arranged in a staggered manner along the entire length of the tube, and the width is occupied by a section that is equal to the size of the radial sector of the struts in the range of 30 ° to 60 °, the struts are fixed

on the one hand a shaped washer with locating pins, and on the other hand an adjusting threaded bushing fixed with a lock nut.

FIG. 2 (prototype) shows a section of a deformed CS, in which the body buckling (dents) occurred in eight places. In this case, spacers, adjustable in length, it is recommended to place between the belts of injection burners, in this example, in eight parts of the body of the combustion chamber, in the locations of dents in the circumferential direction, resulting from loss of stability.

The rational arrangement of the hollow spacers provides additional stable body rigidity and local cooling of the body of the combustion chamber and the working fluid inside the combustion chamber by supplying fresh air through the internal cavities of the spacers. Multiple additional supply of fresh air through the hollow perforated struts into the associated flow of the working fluid provides for fuel combustion, reduces the temperature of combustion products and thereby reduces the formation of nitrogen oxides NO _x in flue gases.

The described design and technological approach to the improvement of annular combustion chambers will increase their efficiency, thermal power, durability and reliability, reduce the formation and emissions of nitrogen oxides NO _x and carbon CO _x in flue gases.

The invention is illustrated graphic material.

FIG. 3 is a diagram of an annular combustion chamber with eight internally mounted struts.

FIG. 4 shows a hollow perforated cross section in the section.

The low-emission annular combustion chamber for gas turbines (see Fig. 3) contains a cylindrical thin-walled outer casing 1 of heat-resistant metal or alloy, and a cone-shaped thin-walled inner casing 2 in the form of a conical socket for exhaust exhaust gases at the outlet of the impeller of the turbine. The outer and inner parts of the annular combustion chamber are interconnected by the method of welding with thin-sheet shells 3, which is a form of a toroid, also truncated along the main meridian, also made of a heat-resistant metal or alloy. The outer casing of the combustion chamber has through-holes 4 of elliptical shape for installation in them at a predetermined angle of the outlet tips of cylindrical injection burners (injection burners in Fig. 3 are not shown conventionally), which form a directional flow of the working fluid in the flow direction. Depending on the required power, the number of windows 4, corresponding to the number of injection burners, can vary and be arranged in one or several rows. Also in the outer casing 1 of the combustion chamber there is a round hole 5 for the installation of a spark plug for igniting the combustible mixture. From the ignition spark, the flame propagates along the annular cavity of the 12 KS to the working injection burners. With the increase in the number of windows 4 and the installation of additional high-pressure burners to increase the power of the turbine, designers are forced to increase the diameter of the outer casing 1 of the combustion chamber. Simultaneously with an increase in power (due to an increase in the number of burners), the temperature in the combustion chamber also increases, which leads to a decrease in the strength and elasticity of the outer casing 1, which undergoes simultaneously a negative pressure from the inside due to the operating turbine and the excessive pressure of the air blown by the compressor.

Hollow perforated struts 6 (Fig. 3, Fig. 4) of adjustable length, made of heat-resistant material. Each strut is made of perforated tube with external thread and through holes 9, with a diameter of less than 1.2 mm. Holes 9 are arranged in a checkerboard pattern along the entire length of the surface of the struts 6, and along the width equal to the radial sector from 30 ° to 60 ° of the struts. The tube 6 is fixed shaped washer 7 with the installation pins 10, equipped with an adjusting threaded sleeve 8 and the lock nut 11. Changing the length of the spacer is made by rotating the sleeve 8, containing "flats turnkey" from the outside of the combustion chamber.

Since the ejection holes 9 are multiply made in a tubular strut 6 in a staggered manner with a diameter not exceeding the critical size of 1.2 mm, they prevent the fire from passing in the opposite direction, thereby excluding the abnormal ignition of the residual combustible mixture formed in the niches above combustion chamber.

The instability of combustion, the switching on and off of the injection burners, the instantaneous discharge or the increase of power violate the stability of the turbine, create claps and throws the flame in the opposite direction. The formation of thermoacoustic waves with destructive high-pressure fronts from the outside of the CS casing causes deformation of the outer casing inward, in the direction of the flow and more discharged part of the combustion chamber. The distortion of the cylindrical body leads to a violation of the geometric dimensions of the combustion chamber, the exit of injection burners from the junction with the 4CS windows, the output of the spark plug from the cavity of the combustion chamber, which eliminates the possibility of re-ignition the next time the turbine is started. The output of injection burners from the joint changes the mode of operation of the turbine, reduces its efficiency and power, causes burnout of the combustion chamber body with subsequent emergency shutdown of the entire microturbine installation.

Low-emission annular combustion chamber for gas turbines operates as follows.

When starting the turbine, a high-energy working fluid (products of combustion, active radicals) fly out from the open part of the burners tangentially directed tangentially to the body at the point of entry of the burners into windows 4 of the CS (FIG. 3) at high speed, falling into the internal annular cavity 12 of the COP, limited outer 1 and inner casing 2 combustion chambers (Fig. 3). Integrating with other streams of high-energy gases formed by adjacent turbine burners, create a total flow of the working fluid in the flow direction. The working fluid, being repeatedly reflected from the guide surfaces 13, 14, falls into the windows of the nozzle grille (not shown in the figures) and further onto the working blades of the turbine impeller, creating torque for rotating the turbine rotor (not shown in the figures). The purified air 15 supplied under pressure from the compressor and turbine recuperator (Fig. 3) rushes to the windows of the burners 4 and to the open ends of the hollow tubes - struts 6 of Figs. 3, FIG. 4. Pressurized fresh air 15 into the hollow tubes 6, while simultaneously cooling them. Integrating with ejection created by the discharge from the outside of the spacers near the holes resulting from the high-speed flow of the directional movement of the combustion products during the flow around the spacers will be sputtered from the ejection holes of the tubes into the speed flow of the working fluid pos.16, interacting with free active radicals. In this case, the working fluid will be partially cooled.

Physical molecular contact between the active radicals migrating in the common stream, which is the combustible component and the oxidizing agent, is a chemical interaction of molecules that are energetically and (or) kinetically excited to form reaction products. Obviously, the molecules are excited as a result of the process that has begun, including the additional effects of temperature, pressure, speed of movement and interactions in the process of mutual diffusion. Since the ejection openings 9, which are made multiple in the tube 6 in a staggered manner with a diameter not exceeding the critical size of 1.2 mm, prevent the fire from passing in the opposite direction and thereby eliminate the abnormal ignition of the residual combustible mixture formed in the niches above the combustion chamber.

The circumstances of the proposed technical solution will allow:

- to improve the operational reliability and durability of the COP;

- due to the method of multiple spraying of fresh air into the total flow of the working fluid, reduce the combustion temperature in the CS and reduce the formation of thermal nitrogen oxides NO _x in the flue gases, increase the resistance of the hot section elements to deformation and destruction;

due to the complete combustion of gas, to reduce carbon dioxide emissions of CO and CO ₂ into the atmosphere, to increase the efficiency of the turbine; Distinctive and significant features of the invention are:

1. The use of special hollow perforated adjustable length cylindrical spacers installed inside the combustion chamber between the outer cylindrical shell and the inner conical exhaust pipe, in order to increase strength and resistance against distortion when exposed to high pressure fronts from outside the combustion chamber.

2. Supply fresh air directly to the combustion chamber through openings in the hollow perforated struts to ensure complete combustion of the fuel and reduce NOx emissions by cooling the combustion products with an additional inflow of fresh air. In order to prevent leakage of fire from the combustion chamber through a hollow tube beyond the outer boundary of the CS, the critical dimensions of the ejection openings should not exceed a diameter of 1.2 mm.

3. The support legs are made of pipe billets of heat-resistant alloys, which allows them to be streamlined without increasing the aerodynamic resistance of the working body flux and retain strength due to constant cooling with fresh air passing through them.

The proposed device, including for the first time applied technical elements and the method of CS operation provided by this device with the creation of a new physicochemical effect of complete combustion of the combustible mixture, reduction of the working body temperature and NO _x emission by supplying additional fresh air (oxidizer) directly to the combustion chamber, as applicable to annular combustion chambers of gas microturbines, previously not used in practice. The described design mode-technological approach will improve the efficiency and reliability of combustion chambers, ensure complete combustion of fuel while reducing the temperature of combustion products and reducing emissions of NO _x , CO, CO _x , reduce or completely eliminate the distortion of combustion chambers.

From the above it follows that the claimed invention has advantages over the prototype; the combination of these signs meets the requirements of novelty; Corresponds to an inventive step.

The rotation of the turbine wheel, in turn, creates a vacuum in the flow part of the CS. The following negative processes occur simultaneously in the combustion chamber:

1. High temperature creates thermal oxides of nitrogen NO _x ;

2. High temperature causes premature aging of surrounding metals and alloys, strength, elasticity decreases, fluidity increases, long-term durability of ensuring the parameters of operating conditions decreases;

3. The connection, disconnection of the burners, discharge and power surge creates during the transition period, before the establishment of a regular stable mode, turbulent multiparameter phenomena that cannot be predicted and calculated. Freelance modes are created with backflows, short-term effects of reverse flame, flame extinction and the occurrence of flares with the creation of thermo-acoustic waves with destructive fronts, which negatively affects the integrity of the CS design.

4. The incomplete combustion of fuel, the presence of active radicals in the working medium flow, due to the difficulty of obtaining a homogeneous combustible mixture and air deficit, lead to incomplete gas combustion with the formation of carbon black and carbon oxides CO _x , which reduces the efficiency of the turbine and pollutes the air.

The improved CS allows to solve the indicated negative processes as much as possible:

1. Fresh air, multiple ejected into the working fluid stream, will provide

- cooling of the working fluid flow, the temperature of the nozzle grille and turbine impeller blades will decrease, which will increase the life of the hot section elements, reduce the formation of thermal nitrogen oxides NO _x ;

- interaction with free active radicals will ensure complete combustion of the gas, increase the efficiency of the turbine, reduce emissions of carbon oxides CO _x ;

2. Spacer racks will protect the CS casing from deformation, increase the combustion chamber life, ensure uniform injection of fresh air into the working fluid flow, and prevent flame penetration from the CS in the opposite direction.

3. Provide maintainability of labor-intensive and expensive CS.

Claims (1)

Low-emission annular combustion chamber for gas turbines, containing a cylindrical thin-walled outer casing and a cone-shaped thin-walled inner casing in the form of a socket for exhaust exhaust gases at the exit of the turbine impeller, which are rigidly interconnected by welding using thin-sheet shell made in the form of a truncated main the toroid meridian, and the outer, inner body and shell are made of heat-resistant metal or alloy, characterized in that between the inner and at least eight hollow spacers of adjustable length, which are made of heat-resistant material, are each radially mounted; each spacer consists of a hollow tube with ejection holes, the diameter of each ejection hole is 1.2 mm or less, and the ejection holes are arranged in a staggered order the entire length of the tube, and the width is occupied by a section that is equal to the size of the radial sector of the struts in the range from 30 to 60 °, the struts are fixed on one side with a shaped washer with installation pins, and on the other hand an adjusting threaded bushing, fixed by a lock nut.

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