Title of Invention

AN IMPROVED GAS TURBINE HYBRID BURNER FOR REDUCTION OF COMBUSTIONS OSCILLATION AND PROCESS THEREOF

Abstract

The invention pertains to an improved hybrid burner (1), in which conbustion air (5) or a combustion air/fuel-mixture (5) is fed in a flow (7) to a combustion, wherey a non-uniform spin is induced in circumferential direction on the flow (7). For feeding the combustion air (5) or the combustion air/fuel-mixture (5). there is a flow channel , in which a spin device (6) for effecting the non-uniform spin in circumferential direction on the flow (7) is arranged. The invention further pertains to an application of a burner as wel1 as a process for reduction of combustion osci1lations.

Full Text

1 An improved hybrid burner for reduction of combustion oscillations in a combustion system and a process thereof. The invention pertains to an improved gasturbine hybrid burner for reduction of combustion oscillations in a combustion system, the burner having a flow channel for feeding a flow of combustion air or a combustion air/fuel-mixture, whereby in the flow channel a spin device is foreseen for inducing a spin on the flow. The invention further pertains to a process for reduction of combustion oscillations during the operation of the burner in a combustion system. During operation of a burner in a combustion system, there could be formation of combustion oscillations. This is also known under the terms "burner chamber ripple", "burner chamber oscillations", "combustion-induced pressure pulsations", "oscillatory combustions". The combustion oscillations are based on an interaction of the quantity of combustions air/fuel-mixture flowing in the flow channel and which is fed per unit of time, which is ignited on entering into a burner chamber and combusted in a flame, with momentary combustion turnover in the flame. By combustion turnover one means the quantity of combustion air/fuel-mixture converted during combustion in a flame per unit of time. By changing the combustion turnover there could be pressure fluctuations in the burner chamber which could lead to formation of a stable pressure oscillation. Apart form an enhanced noise generation, the combustion oscillations also cause a reinforced mechanical and thermal load of the walls belonging to the burner chamber and other accessory parts of the combustion system. A hybrid burner for a gas turbine is known from the document EP-0-580 683 Bl. A hybrid burner has a diffusion burner as well as a premix burner. Therefore, it can be operated in diffusion operation as well as in premix operation. The premix burner of the hybrid burner has a ring channel for feeding combustion air or a combustion air/fuel-mixture. Arranged in the ring channel there is a spin device for inducing a spin on the flow which forms the fed combustion air/fuel-mixture or the combustion air in the ring 2 channel This spin device is also referred to as spin screen. The diffusion burner of the hybrid burner is arranged coaxially in the ring channel of the premix burner. The diffusion burner has a combustion air feeding channel designed as ring channel, in which a fuel feeding channel is arranged coaxially. The channels of the diffusion burner enter into a nozzle , The diffusion burner additionally has a pilot burner in its combustion air feeding channel which is necessary only for operation of the premix bum. In case of a premix operation of the hybrid burner, a combustion air/fuel mixture is fed through the ring channel of the premix burner and this forms a flow in the ring channel, on which a spin is induced with the help of the spin screen. The spin-adhered flow exits out of the premix burner to a combustion. The combustion is stabilized with the help of the flame of the pilot burner. In a diffusion operation of the hybrid burner, combustion air or fuel respectively is fed through the combustion air- and the fuel feeding channel of the diffusion burner to a mixture in the region of the nozzles of the diffusion burner. The combustion air/fuel-mixture formed during mixing exits out of the diffusion burner to a combustion. It is the task of this invention to present a burner with a sight inclination for formation of combustion oscillations during application in a combustion system. A further task of the invention is to present a process for reduction of combustion oscillations. This task is fulfilled as per the invention by means of a burner, which as a spin device with a flow-offend; the spin device is designed in such a way that the spin is created non-uniformly in circumferential direction. The invention is based on the knowledge that on. operation of a burner in the flow channel, a flow of combustion air gets formed, to which fuel is mixed through fuel inlets for forming combustion air/fuel mixture. Feeding of fuel takes place preferably in a uniform flow of combustion air flowing through the cross section of the flow channel. This has the advantage that the local mixing ration between combustion air and fuel over the cross section is by and large uniform. With a uniform mixing , the NOx-content of the exhaust gas which is generated on combustion of the combustion air/fuel mixture 3 formed during mixing, can be influenced. Before the combustion air/fuel-mixture is fed to the combustion, a spin is created in the flow channel with a spin device, in order to stabilize the combustion. This spin is mostly uniform over the circumference of the flow channel, so as not affect the uniformity of the flow. Investigations have revealed the following: the more uniform the flow of a combustion air/fuel-mixture fed for combustion with a burner, the greater is the probability that on operation of the burner in a combustion system there could be formation of combustion oscillations. The invention is therefore based on the idea of designing a burner in such a way, that a flow of a formed combustion air /fuel-mixture before feeding to a combustion is made so non-uniform by inducing a non-uniform spin, that the impulse of combustion oscillations during operation of the burner in a combustion system is at least clearly reduced. For this, with the help of a spin device arranged in the flow channel, a non-uniform spin is effected on the flow of the combustion air/fuel-mixture in circumferential direction. Ideally the spin device has several spin elements, whereby each spin element has a diverting surface. On account of the geometry of the flow channel, a main flow direction of the flow of the combustion air/fuel-mixture is defined, which can change depending on the burner geometry. The diverting surfaces of the spin elements have at the flow-off end respectively a flow-off angle to the main flow direction, which should preferably be different for at least two directly adjacent spin elements. In this way it is achieved that the flow after flowing through the spin device in circumferential direction exits at least in two different angles, so that the induced spin in circumferential direction is non-uniform. Furthermore, each spin element is designed as a spin blade. Several spin elements with the same flow-off angles ideally form a spin group and the spin device has at least one such spin group. Furthermore, the spin device is formed out of several spin groups, whereby adjacent spin groups have different flow-off angles. The spin device can hereby be formed out of six spin groups, whereby each spin group respectively could have four spin elements. 4 The flow channel of the burner is preferably designed as ring channel, whereby the spin sift-device is arranged in the ring channel. The burner can, for example, be designed as hybrid burner for a gas turbine. For reducing the quantity of No compounds during combustion, it is desirable to feed into a uniform flow of a combustion air for formation of combustion air/fuel-mixture meant for combustion. For this, the burner preferably has a fuel inlet, through which fuel can be fed into the flow channel in flow direction of the flow-off end. In this way the fuel is fed into a uniform flow before the spin device of the combustion air flowing in the feeding channel. The task of application is fulfilled by means of the invention , according to which the burner is used in a gas turbine for combustion of a combustion air/fuel-mixture in a burner chamber. The task before the invention is fulfilled by means of a process whereby a flow of a combustion air/fuel-mixture or of combustion air is subjected to a non-uniform spin in circumferential direction in a flow channel of the burner. On the basis of the design example shown in the accompanying drawings, the spin device for creating the spin and the process for reduction of combustion oscillations is described in more details. The following are shown schematically and partly not to scale, mentioning the design and functional features used for the description. Fig. 1 A burner designed as hybrid burner for a gas turbine; and Fig. 2 A view of the spin elements of the ring channel of the premix burner developed in circumferential direction. The reference numbers of all figures respectively have the same meaning. In fig. 1, a burner 1 designed as hybrid burner 1 of a gas turbine (not shown in details) is shown. The hybrid burner 1 has a diffusion burner 2, as well as a premix burner 3. The 5 premix burner 3 has a ring channel 4 with an outer wall 16 which serves the purpose of feeding combustion air 5 or a combustion air/fuel-mixture 5. Arranged in the ring channel 4 there is a spin device 6 with a flow-off end 12 which serves the purpose of inducing a spin on a flow 7, which forms the fed combustion air/fuel-mixture 5 or the combustion air 5 in the ring channel 4. The spin device 6 is also referred to below as spin screen. The spin screen 6 has several spin elements 15 which are respectively designed as spin blades. In the flow direction of the flow-off end 12, fuel inlets 13 are arranged through which the fuel 14 can be fed into the ring channel 4 and thus can be mixed with the combustion air 5. The diffusion burner 2 of the hybrid burner 1 is arranged coaxially in the ring channel 4 of the premix burner 3. The diffusion burner 2 has a combustion air feeding channel 8 designed as a ring channel, in which a fuel feeding channel 9 is arranged coaxially. The channels 8 and 9 of the diffusion burner 2 go into a nozzle 10. Furthermore, the diffusion burner 2 has a pilot burner 11 in its combustion air feeding channel 8, which is provided for an operation of the premix burner 3. In a premix operation of the hybrid burner 1, combustion air 5 is fed through the ring channel 4, which gets mixed with the fuel 14 fed through the fuel inlet 13 to a combustion air/fuel-mixture. In the flow channel 2 the combustion air/fuel-mixture 5 forms a flow 7 with a local main flow direction 14. On flowing through the spin screen 6 a non-uniform spin is induced on the flow 7 in circumferential direction, with which the flow 7 leaves the spin screen 6 at the flow-offend 12 and subsequently exits out of the ring channel 4. After the exit, an ignition and combustion of the combustion air/fuel-mixture 5 takes place. With the help of a flame of the pilot burner 11 the combustion is stabilized. Advantageous in the described design of the hybrid burner 1 is, that on account of the non-uniform spin which the flow 7 of the combustion air/fuel-mixture 5 fed to the combustion has, the flow-off from the burner itself is non-uniform, whereby and increase of combustion oscillations is at least reduced. Furthermore, it is of advantage that the flow 7 has a spin, with which the combustion is stabilized. In the ring channel 4 of the 6 premix burner the combustion air 5 forms in flow direction of the flow-off end 12 a uniform flow 7. By means of the arrangement of the fuel inlets 13 fuel 14 can be fed to the uniform flow 7 of the combustion air 5 in flow direction and get mixed there, whereby a uniform mixing between combustion air 5 and fuel 14 can be achieved. In this way, a reduction in the quantity of Nox-compounds formed during combustion is possible. Analogous to the design of the design spin screen 6 of the premix burner 3, a spin screen arranged in the combustion air feeding channel 8 can be designed in such a way that with it a non-uniform spin can be induced on a flow forming in the combustion air feeding channel 8 in circumferential direction. In fig. 2 a view of the spin elements 15 of the ring channel 4 of the premix burner 3 developed in a circumferential direction is shown, whereby as view direction the direction 17 shown in fig.l perpendicular to the outer wall 16 of the ring channel 4 is selected. The spin elements 15 respectively have a diverting surface 18. The diverting surfaces 18 form along with the local main flow direction 14 (see also fig.l) respectively a flow-off angle a. The diverting surfaces 18 of two adjacent spin elements 20 and 21 have different flow-off angles a1 and a2. In this way the flow 7 leaves the spin screen 6 at the flow-off 12 with a non-uniformly induced spin in circumferential direction. The spin element 20 and the spin element 21 are combined respectively to one spin group, which have the flow-off angles a1 or a2. The invention is characterized by a burner, in which combustion air or a combustion air/fuel-mixture is fed in a flow to a combustion, whereby a non-uniform spin in circumferential direction is induced on the flow. 7. WE CLAIM: 1. An improved gas turbine hybrid burner (1) for reduction of combustion osci11ations in a combustion system comprising a diffusion burner (2) having a combustion air feeding channel (8) configured as a ring channel in which coaxially being disposed a fuel feeding channel (9), said channels (8,9) extending into a nozzle (10); a premix burner (3) having a ring channel (4) for feeding a flow (7) of combustion air (5) or a combustion air/fuel mixture (5), characterized in that a spin device (6) having a plurality of spin elements (15) each having a diverting surface (18) at a flow-off end (12) is disposed at said ring channel (4) for inducing a non-uniform spin in a circumferential direction, forming a respective flow-off angle in respect of a local main flow direction (14) being defined on account of the geometry of said ring channel (4) such that the flow-off angle of at least two directly adjacent spin elements (15) are different ( a1 ,a2) 2- The burner (1) as claimed in claim 1, wherein each of said spin element (15) is designed as a spin blade. 3. The burner (1) as claimed in claim 1 or 2, wherein the spin device (6) has a plurality of spin group (20 or 21), formed out of said plurality of spin elements (15) with equal flow-off angles ( a1 or a2 ). 8. 4. The burner (1) as claimed in claim 3, wherein the spin device is formed out of said sping groups (20,21) whereby the adjacent spin groups (20, 21) have different flow-off angles ( a1 and a2). 5. The burner as claimed in claim 4, wherein the spin device (6) has six spin groups each with four spin elements. 6. The burner (1) as claimed in one of the previous claims, wherein fuel can be fed through a fuel inlet (13) into the ring channel (4) in flow direction of the flow-off end (12). 7. The burner (1) as claimed in claim 1, wherein said diffusion burner (2) has a pilot burner (11) disposed in said air-feeding channel (8) provided for operation of said premix burner (3). 8. Process for reduction of combustion oscillations during operation of a burner (1) as claimed in claim 1 comprising the steps of : - providing a burner (1) in a combustion system; - feeding combustion air (3) through the ring channel (4) of the burner (1): - feeding fuel (14) through an inlet (13) arranged in the flow off end (12) into the ring channel (4); - forming a flow (7) with said combustion air-fuel mixture in the flow channel (2), the flow (7) having a local main flow direction (14); inducing a non-uniform spin to the flow (7) in a circumferential direction while the flow passes through the spin device (6) such that the flow (7) with the non-uniform spin exiting out of the ring channel (4) of the burner (1), Dated this 12th day of March 1999 The invention pertains to an improved hybrid burner (1), in which conbustion air (5) or a combustion air/fuel-mixture (5) is fed in a flow (7) to a combustion, wherey a non-uniform spin is induced in circumferential direction on the flow (7). For feeding the combustion air (5) or the combustion air/fuel-mixture (5). there is a flow channel , in which a spin device (6) for effecting the non-uniform spin in circumferential direction on the flow (7) is arranged. The invention further pertains to an application of a burner as wel1 as a process for reduction of combustion osci1lations.

Documents:

00211-cal-1999-abstract.pdf

00211-cal-1999-claims.pdf

00211-cal-1999-correspondence.pdf

00211-cal-1999-description(complete).pdf

00211-cal-1999-drawings.pdf

00211-cal-1999-form-1.pdf

00211-cal-1999-form-18.pdf

00211-cal-1999-form-2.pdf

00211-cal-1999-form-3.pdf

00211-cal-1999-form-5.pdf

00211-cal-1999-g.p.a.pdf

00211-cal-1999-priority document others.pdf

00211-cal-1999-priority document.pdf