RU2551462C2 - Pre-mixing burner - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: invention relates to power industry. Pre-mixing burner (1) with air supply duct (21), at least one pilot gas supply duct (23) that includes at least one wall of duct (39) directed to air supply duct (21) and one pilot gas outlet end (29) entering air supply duct (21), with ignition element (35) located in air supply duct (21) opposite to flow direction to pilot gas outlet end (29), wall of duct (39) for supply of pilot gas (23) opposite to the flow direction to ignition element (35) includes at least one gas outlet hole (37) and with that, pilot gas supply duct (23) in the flow direction of at least one gas outlet hole (37) includes flow resistance (41, 43, 47, 49, 51, 55), and with that, flow resistance is made by constriction (41, 43, 47, 49) of pilot gas supply duct (23); the constriction is made by means of projection (47, 49) located on the wall of duct (39) and directed inwardly, or the constriction is made by means of sleeve (41) installed in duct (23) and reducing the duct cross-section, or the constriction is made by means of element (51, 55) installed in duct (23) and reducing the duct cross-section, and at least one pilot gas supply duct is made in the form of at least one pilot gas tube (23) that is located in cavity (19) of burner (1) and that leaves cavity (19) at the point located opposite the flow direction to ignition element (35) and enters air supply duct (21); with that, the tube wall forms the duct wall, and at least one gas outlet hole (37) is located in section (27) of pilot gas tube (23), which enters air supply duct (21).

EFFECT: invention allows designing a burner that has a lighting-up sequence that makes a proper ignition burner unnecessary.

6 cl, 9 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a premix burner, which comprises a starting burner and an igniter.

State of the art

Pre-mixing burners are used, first of all, in order to prevent the emergence of the so-called zones of maximum temperature Hotspots of the flame, that is, the formation of inhomogeneity of the flame with very hot zones of the flame. The goal is to reduce NOx emissions from combustion. NOx production increases exponentially with flame temperature. Therefore, decreasing the peak values (Hotspots) of the flame temperature leads to a reduction in NOx emissions.

To keep the temperature of the premixing flame as low as possible, the burner often runs on a lean mixture at the stability boundary, that is, as compared to that required for burning air, so little fuel is added that a hardly flammable mixture is formed. However, this kind of lean mixture can lead to instability of the premix flame, which as a result causes pressure fluctuations in the combustion system. Therefore, in order to stabilize the flame of preliminary mixing of the lean mixture, start-up burners that operate as diffusion burners are used, that is, fuel and the air necessary for combustion are fed into the flame without strong preliminary mixing. The proportion of pilot fuel in the total amount of fuel burner is approximately 5 to 10%. In addition to stabilizing the premixing flame, the starting torch can also be used for ignition.

DE 19757617 and A1 WO 00/12933 describe so-called hybrid burners that contain both a premix burner and a diffusion burner. The premix burner is arranged concentrically around the diffusion burner. In addition, the diffusion burner also contains a pilot fuel supply system so that it can be used for the starting burner.

EP 1712837 A1 describes a burner whose arrangement is similar to that described in DE 19757617 A1 and WO 00/12933. However, there are no separate supply channels for the diffusing gas, that is, the gas that is used for the diffusion operation of the burner, and the pilot gas, that is, the gas that is used for the operation of the starting burner. Instead, both the diffusing gas and the pilot gas may be supplied through the same fuel line or the same fuel lines. Thus dispensing with a gas supply system.

Typically, a pilot flame is ignited by a flame of a diffusion burner. Therefore, this can be done in this way, since the diffusion burner is usually used to start the gas turbine and the start burner is used only when they switch to the burner pre-mixing mode. In addition, as a rule, there is still a pilot burner with which a diffusing gas is ignited. A similar ignition burner, for example, is described in EP 0193838 B1. Unless, as described in EP 1712837 A1, there is a common fuel supply system for diffusing and pilot gas, a suitable ignition device is necessary, since the ignition burner in the form in which it is used in a conventional hybrid burner is not directly suitable for this .

Disclosure of invention

Therefore, it is an object of the present invention to provide a burner without supplying a diffusing gas, which has an ignition order that makes it unnecessary to have its own pilot burner.

This problem is solved by means of a preliminary mixing burner according to claim 1. The dependent claims contain preferred embodiments of the invention.

According to the invention, the premix burner comprises an air supply channel, a pilot gas supply channel, which at least has a wall facing the pilot gas supply channel and an outlet end of the pilot gas entering the air supply channel, and also located opposite the pilot gas outlet the flow in the air supply channel is an ignition element, which, for example, can be designed as a bipolar ignition electrode. In the wall of the channel for supplying the pilot gas there is at least an opening for gas outlet located upstream of the ignition element.

According to the invention, the embodiment of the premix burner allows direct ignition of the pilot gas, that is, without first having to ignite the diffusion flame supplied through the own channel of the diffusing gas, and without the need for an ignition burner with a pilot gas channel only necessary for ignition. For ignition, the pilot gas can be released from at least one gas outlet to the air supply duct and there together with air form a combustible mixture that flows past the ignition element located in the direction of flow. Therefore, the entire design of the burner can be simplified, since fewer gas pipelines are required, which leads to lower costs in the manufacture of the burner.

In a burner according to the invention, the pilot gas supply channel detects flow resistance in the direction of the flow of at least one gas outlet orifice. Resistance to flow in the gas opposite the flow direction leads to an increase in pressure, which ensures that enough gas is released to form a combustible mixture in the area of the ignition element through the gas outlet in the air supply channel. Resistance to flow can be realized, for example, by narrowing, in particular narrowing at the output end of the pilot gas supply channel.

A simple opportunity to constructively narrow the constriction is to position the protrusion in the channel located on the wall of the channel and directed inward. There is another possibility of narrowing by means of a sleeve installed in the channel, which decreases along the cross section of the channel. A further possibility is to install a restriction element in the pilot gas supply channel. Such an element could be, for example, a streamlined element, a lattice, a grid, etc.

In the preliminary mixing burner according to the invention, the channel wall may comprise, against the flow direction towards the ignition element, at least two gas outlet openings displaced in the direction of flow. Thus, it is possible to increase the amount of outgoing pilot gas without increasing the cross section of the gas outlet openings so that their aerodynamics change.

In order to expand the enlarged profile of the pilot fuel supplied to the air supply channel, at least two offset openings for the gas outlet through the channel wall flowing through the air supply channel against the direction of flow to the ignition element can be arranged.

In an embodiment of the premix burner in accordance with the invention, the pilot gas supply channel is designed in the form of a pilot gas tube which is laid in the burner cavity and exits the cavity in a location opposite the flow direction to the ignition element and enters the air supply channel. In this case, the tube wall forms the channel wall, and at least one gas outlet is located on the portion of the pilot gas tube entering the air supply channel. The installation of one or more pilot gas tubes is possible, in particular, in addition to existing burners so that existing burners can be retrofitted.

Brief Description of the Drawings

Other features, properties, and advantages of the present invention will follow from the further description of an embodiment with reference to the accompanying drawings.

Figure 1 shows in accordance with the invention the burner in a schematic section.

FIG. 2 shows a pilot gas tube with gas outlets located therein.

Figure 3 shows the pilot gas tube of figure 2 in section III-III.

Figure 4 shows a section of the pilot gas tube entering the air channel in longitudinal section.

Figure 5 shows the output of the second embodiment of the pilot gas tube.

Figure 6 shows the output of the third embodiment of the pilot gas tube.

7 shows the output of the fourth embodiment of the pilot gas tube.

On Fig shows the output of the fifth embodiment of the pilot gas tube.

Figure 9 shows the output of the sixth embodiment of the pilot gas tube.

The implementation of the invention

Next, an embodiment of a burner in accordance with the invention is described with reference to FIG. The burner 1 is constructed essentially symmetrically with respect to the axis of the burner A with the outlet of the burner 9 open towards the combustion chamber 7. It contains a main burner nozzle 13, which has an inlet channel for liquid fuel and, on its end, one or more spray nozzles nozzles for injecting liquid fuel into the flame prevailing in the combustion chamber. The nozzles 13 are used to create a diffusion flame fed by liquid fuel. If the burner is designed only for general operation on gaseous fuel, then instead of the nozzle 13 described, an attrappe is used, which in its external geometry is similar to the nozzle described, but without spray nozzles at the end of the combustion chamber 15.

Around the nozzle of the burner 13 there is a cylindrical wall 17, which surrounds the cavity 19 formed between the wall 17 and the nozzle of the burner. The annular cavity 19 serves to supply combustible gas to the air supply duct 21, through which the air necessary for maintaining the flame is supplied to the burner 1. In addition, the annular cavity 19 contains openings for the exit of gas 20. Against the direction of flow of the exit of the burner 9, the burner 1 contains the so-called axial lattices 30, which provide swirling of air and combustible gas and as a result they are thoroughly mixed. A thoroughly mixed gas-air mixture is fed through the outlet of the burner 9 of the combustion chamber 7, where it is burned.

To keep NOx emissions at a low level, the mixed air-gas mixture is regulated to a low fuel content, that is, the proportion of fuel in the mixture is kept as low as possible, which helps prevent temperature peaks forming NOx in the resulting pre-mixing flame. The ignition flame, which, in contrast to the pre-mix flame, is used as a diffusion flame, serves to stabilize the pre-mix flame, which works practically at the stability limit, in order to prevent pressure fluctuations in the combustion chamber due to combustion oscillations. In a diffusion flame, in contrast to a preliminary mixing flame, thorough mixing of fuel and air does not occur before they enter the flame. The ignition flame serves not only to stabilize the premixing flame, but also to ignite the premixing flame.

To feed the ignition flame, the pilot gas tubes 23 are laid through the annular cavity 19 between the cylindrical wall 17 and the nozzle of the burner 13 to the end of the combustion chamber of the cavity 19. There they pass through the front wall 25 mainly in the form of a scan of the conical surface and enter through the pipe section 27 into air supply channel 21. The output ends from the side of the combustion chamber 29 of the pilot gas tubes 23 are open and are used to inject pilot gas into the air flowing through the annular supply channel 21. In addition, an igniter 31 with a bipolar ignition electrode 33 is included in the air supply channel 21. The apex 35 of the bipolar ignition electrode 33, which is its own ignition element of the burner 1, is opposite the flow direction to the open outlet ends 29 of the pilot gas tubes 23. It is located such so that it lies wide on the same radial line, for example, one of the pilot gas tubes 23. Thus, the bipolar ignition electrode 35 is close to the pilot gas tube. It should be noted that the apex 35 of the ignition electrode 33 need not be on the same radial line, for example, one of the tubes of the pilot gas 23. It is only important that the apex 35 is brought close enough to one of the tubes 23.

The pilot gas tube 23 located close to the igniter 31 is additionally equipped with at least one gas outlet 37 located in the wall of the tube against the direction of flow towards the outlet end 29, to open the outlet end 29. In the present embodiment, there are three gas outlet openings 37a , 37b, 37c, which are made in the form of axially displaced tubes 23 and in the direction along the circumference of the tube 23 of the holes. The location of the holes is shown in FIGS. 2 and 3, where FIG. 2 shows a view of the holes in the pilot gas tube 23 and FIG. 3 is a section III-III of the wall of the tube 39 of the pilot gas tube 23. The location of the holes 37a, 37b, 37c is selected taking into account the optimization of the distribution profile of the gas exiting through the openings 37.

The gas outlet openings 37 are located in the pilot gas tube 23 against the flow direction to the top of the electrode 35, that is, the gas exiting the openings 37, which enters the air flowing through the supply duct 21, is directed along the top of the electrode 35, so that the gas can ignite with a spark.

To ensure that through the openings 37a, 37b, 37c there is a sufficient flow resistance for igniting the amount of gas in the pilot gas tube 23 in the direction of flow of the gas outlet openings, It leads to the fact that against the flow direction towards the flow resistance there is an increase in pressure, which is responsible for ensuring that a sufficient amount of pilot gas is released through the openings 37a, 37b, 37c into the air supply channel 21 for successful ignition.

In detail, a section of the portion 27 of the pilot gas tube 23 entering the air supply duct 21 is shown in FIG. on an enlarged scale. On it you can see only one of the holes 37 passing through the wall of the tube 39. At the output end of the pilot gas tube 29, a sleeve 41 is installed in the pilot gas tube 23, which reduces the cross section of the flow in the pilot gas tube 23. Thus, the gas pressure rises against the direction of flow to the sleeve 41 so that a sufficient amount of pilot gas is released through the openings 37.

An alternative embodiment of creating flow resistance in the area of the outlet end 29 of the pilot gas tube 23 is shown in FIG. Instead of the sleeve 41, the pilot gas tube 23 at the output end 29 contains a truncated cone section of the wall 43, which leads to the fact that the outlet 45 at the end of the pilot gas tube 29 has a passage section reduced in comparison with the cross section of the flow of the pilot gas tube 23. Thus, it is possible to achieve the desired increase in pressure in the zone against the direction of flow to the gas outlet openings 37.

Another option for obtaining resistance to flow in the tube of the pilot gas 23 is presented in Fig.6. In this embodiment, the pilot gas tube 23 comprises, in front of the outlet end 29, a V-shaped recess 47 extending around its circumference, which reduces the cross-section of the flow for the pilot gas in the recess zone. The decrease in the cross section of the flow in turn leads to an increase in pressure against the direction of flow to the recess 47.

The next embodiment of the formation of flow resistance is shown in Fig.7. In this embodiment, the pilot gas tube 23 comprises, in front of the outlet end 29, an inwardly extending protrusion 49 extending around the circumference of the tube, which leads to a decrease in the flow cross-section for the pilot gas and thereby to an increase in pressure against the flow direction to the protrusion 49.

Another embodiment of creating flow resistance is shown in FIG. In this embodiment, a cylindrical wall of the tube 39 is designed up to the outlet end 29. A decrease in the cross section of the flow with increasing pressure in the pilot gas tube 23 is carried out by means of a streamlined insert 51, which is fixed by supports 53 on the inner surface of the tube wall 39. Fixing can be carried out by high-temperature soldering or welding. Alternatively, the supports can also be fixed to the wall of the tube 39 by means of a threaded connection.

Another option for the formation of flow resistance in the tube of the pilot gas 23 is presented in Fig.9. And the pipe of the pilot gas 23 shown in FIG. 9 contains a cylindrical wall of the tube 39 to its outlet end 29. A grill 55 is installed in front of the outlet end 29 or directly at the outlet end 29 of the pilot gas 23, which is an obstacle to the flow of the pilot through the tube 23 gas and thus leads to an increase in pressure against the direction of flow to the lattice 55.

The invention described by means of an embodiment allows a burner in which a starting burner contains only pilot gas supply channels as the only supply channels to ignite the burner without a pilot burner having its own fuel supply system specifically for this purpose. Therefore, in accordance with the invention, the burner manages only two gas supply systems, namely, the pilot gas supply system and the gas supply system in the pre-mixing mode. The result is a simplification of the design of the burner and, at the same time, the manufacturing cost.

Claims (6)

1. Pre-mixing burner (1) with an air supply channel (21), at least one pilot gas supply channel (23), which contains at least one channel wall (39) directed to the air supply channel (21) and one inlet the outlet end of the pilot gas (29) into the air supply channel (21), with the ignition element (35) located in the air supply channel (21) against the direction of flow to the output end of the pilot gas (29),
characterized in that
the wall of the channel (39) for supplying the pilot gas (23) against the direction of flow to the ignition element (35) contains at least one gas outlet (37) and wherein the channel for supplying the pilot gas (23) in the direction of flow of at least one hole for the gas outlet (37) contains flow resistance (41, 43, 47, 49, 51, 55), and moreover, the flow resistance is made by narrowing (41, 43, 47, 49) of the pilot gas supply channel (23), and the narrowing is performed by located on the wall of the channel (39) directed inwardly protrusion (47, 49), or narrowing by means of a sleeve (41) reducing the cross section of the channel installed in the channel (23), or narrowing is performed by means of a member (51, 55) reducing the cross section of the channel installed in the channel (23), and at least one pilot gas supply channel is made in the form at least one pilot gas tube (23), which is laid in the cavity (19) of the burner (1) and which leaves the cavity (19) in a place located opposite to the direction of flow to the ignition element (35) and enters the air supply channel (21 ), and the wall of the tube forms the wall of at least one gas outlet (37) is located on the portion (27) of the pilot gas tube (23) entering the air supply channel (21). 2. Burner pre-mixing (1) according to claim 1,
characterized in that
the restriction is located at the outlet end (41, 43, 47, 49) of the pilot gas supply channel (23). 3. Burner pre-mixing (1) according to claim 1,
characterized in that
the wall of the channel (39) contains against the direction of flow to the ignition element (35) at least two displaced in the direction of air flow in the air supply channel (21) into the gas outlet (37a, 37b, 37c). 4. Burner pre-mixing (1) according to claim 1,
characterized in that
the wall of the channel (39) contains against the flow direction to the ignition element (35) at least two offset gas outlets (37a, 37b, 37c) that are vertical to the direction of the air flow in the air supply channel (21). 5. Burner pre-mixing (1) according to claim 2, characterized in that
the wall of the channel (39) contains against the flow direction to the ignition element (35) at least two offset gas outlets (37a, 37b, 37c) that are vertical to the direction of the air flow in the air supply channel (21). 6. Burner pre-mixing (1) according to claim 3,
characterized in that
the wall of the channel (39) contains against the flow direction to the ignition element (35) at least two offset gas outlets (37a, 37b, 37c) that are vertical to the direction of the air flow in the air supply channel (21).

Images