Premix burner

Technical field

p0001The invention relates to a premix burner, at essentially comprising at least two interleaved in the flow direction part-cone bodies having their respective cone axes of which are offset from a central axis, whereby tangential slots for the combustion air are formed.

State of the art

p0002Such premix burners are known, for example from EP-B1-0 321 809.-The designed as a swirl burner premixing burner, which consists of two cone half-shells substantially, the combustion air is set in rotation. The fuel is injected into the rotating air and mixed there with her. At the burner outlet leaves behind a dome-shaped recirculation zone, headed ignition occurs. The flame itself is stabilized by the recirculation zone in front of the burner, without the need for a mechanical flame holder. The thermoacoustic behavior of such burners is normally stable and they are characterized by a simple and inexpensive construction.

p0003If the burner is operated with gaseous fuel, for this purpose longitudinally distributed gas inlet openings are provided in the region of the cone formed by the two half-shells tangential slots in the walls of the two partial bodies. In gas mode, the mixture formation thus begins with the combustion air already in the zone of the inlet slots.

p0004At the top of the cone shells a fuel nozzle for liquid fuel is located. The fuel is injected at an acute angle in the hollow cone. The resulting conical fuel profile is enclosed by the tangentially inflowing air. In axial direction, the concentration of the fuel is continuously reduced as a result of mixing with the compressed air. The injection angle of the fuel is determined by the opening angle of the premix burner. However, good mixing between liquid and gaseous fuel is made difficult due to the low angle of aperture, which can lead to increased pollutant emissions.

p0005At part load, when the operation of the premix burner is no longer guaranteed by the injection of gaseous fuel in the region of the tangential slots, gaseous fuel is injected via the arranged at the top of the cone shells fuel. Through the large axial distance between backflow and fuel there is a risk that the axial position of the flame changes and this results in pulsations. Next rises, due to the large axial distance between backflow and fuel, the amount of required fuel, which can lead to increased pollutant emissions.

Summary of the Invention

p0006The invention has for its object to reduce at a premix burner of the type mentioned pollutant emissions and stabilize the backflow.

p0007This is according to the invention achieved by starting from the top of the partial conical bodies a downstream inside the premix burner extending feed lance is arranged symmetrically extends substantially to the central axis, and that at the downstream end of the feed lance is arranged at least one fuel.

p0008The advantages of the invention are, inter alia, in that the axial distance between backflow and fuel is shortened by projecting into the burner interior feed lance. Thus, the backflow zone is stabilized in each load range in the axial direction and pulsations are avoided. By carrying out the injection of the fuel through the fuel nozzle in the vicinity of the reverse flow, also less fuel to stabilize the flame is needed. Thus, it is possible even at partial load to operate the premix burners Low NOx emissions. The outer surface of the feed lance also serves as a shear surface which supports the mixing of gaseous fuel and combustion air, thereby reducing the emission of pollutants. The positioning of the fuel nozzle in the vicinity of the reverse flow of the injection angle of the fuel nozzle for liquid fuel can be increased. This premix is ​​improved with the use of liquid fuels and reduce the nitrogen oxide emissions.

p0009It is particularly expedient if the feed lance extends downstream to at least the lower third of the premix burner. This prevents flash back of the flame front in the burner interior.

p0010Further, it is convenient to form the feed lance from a lance tube and a fuel conduit disposed therein. This can be blown through the lance tube, a part of the combustion air, whereby the mixing of fuel and air is supported. In addition, prevents the flame attaches to the end of the feed lance.

p0011It is advantageous to arrange a swirler between the lance pipe and the fuel line. This allows the air blown through the lance tube air be imparted any spin, whereby the mixing is further optimized.

p0012In addition, it is expedient at the downstream end of the lance tube to arrange an air-assisted atomization nozzle. This allows liquid fuel with low emissions to burn.

p0013It is of advantage that the premix burner in the region of the burner outlet has at least one circular cross-section. The circular burner exit generates an axially-symmetric flow with respect to the central axis. This will pulsations caused avoided by the partial conical axes and further stabilizing the backflow.

Brief Description of Drawing

p0014The drawing shows an embodiment of the invention is illustrated with a premix burner.

p0015Show it: <dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>a partial longitudinal section through the premix burner;</dd><dt>FIG. 2</dt><dd>a partial cross-section through the premix burner along the line II-II in Figure 1;</dd><dt>Fig. 3</dt><dd>the detail III of Figure 1;</dd><dt>Fig. 4</dt><dd>a partial cross section along line IV-IV in Fig.4;</dd><dt>Fig. 5</dt><dd>a partial cross-section through the premix burner along the line VV in Figure 1;</dd><dt>Fig. 6</dt><dd>a partial cross section of an adapter;</dd><dt>Fig. 7</dt><dd>a schematic, perspective view of the adapter.</dd></dl>

p0016Only the elements essential for understanding the invention are shown. The flow directions of the working media are represented by arrows.

Way of Implementing the Invention

p0017In Fig. 1 and Fig. 2, a premix burner is shown schematically eleventh It is essentially a so-called double-cone burner, as it is 321 809 known from the aforementioned EP-B1-0. The premix is ​​previously used the combustion of mixing of combustion air and fuel, for example in a gas turbine group. Such premix burner 11 is composed of two hollow semi-conical partial bodies 12 and 13 that are interleaved in the flow direction. The respective cone axes are offset 14 and 15 of the two part body against the central axis 10 of the premixing burner eleventh The adjacent walls of the two partial bodies form tangential slots 16 for the compressed combustion air 9, which enters in this manner in the burner interior in the longitudinal extension.

p0018In the region of the tangential slots 16 in the walls of the two partial bodies extending in the longitudinal direction of the gas supply lines 18 are provided. The injection of the gaseous fuel takes place via not shown, branched from the gas supply line 18 Gaseinströmungsöffnungen.

p0019Symmetrical to the central axis 10 of the premix burner 11, starting from the tip formed by the partial conical bodies 12, 13 is a downstream extending feed lance 1 is arranged. It consists of a lance tube 2 disposed therein and a fuel line 3. The axial position of the downstream end of the feed lance 1 is preferably located at least in the lower third of the premix burner 11, that the feed lance can project out of the premix burner eleventh For example, the feed lance 1 protrude up to twenty percent of the axial height of the premix burner of the premix 11th In the interior of the lance tube 2, preferably in the vicinity of the downstream end, a swirl body 6 is disposed.

p0020According to FIG. 3 and FIG. 4, the swirl body 6 of a plurality of deflection bodies 7, which are arranged between the inner wall of the lance tube and the fuel line 3. Inside the fuel line 3, an annular outer fuel feed 5 and an inner fuel supply channel 4 is located. By means of the inner duct 4 is one located at the downstream end of the fuel line 3, fuel nozzle 8 fed fuel. The nozzle 8 is designed as a dual nozzle system for injection of liquid and gaseous fuels. The outer channel 5 is branched on the deflecting 7 in an outer fuel supply channel 5a from the inside of the downstream end of the lance tube second The conveyed through the outer duct 5 liquid fuel 30 is thereby guided to the downstream end of the lance tube second Located at the downstream end of the lance tube 2 outer edge of the lance tube is used as atomization 17th

p0021The compressed combustion air generated in a non Pictured compressor 9 enters through the tangential slots 16 into the interior of the premix burner 11th The embodiment of the premix burner 11, the air is set in rotation 9, wherein the swirl number increases in the flow direction. In gas operation, the mixture formation starts with the combustion air 9 in the zone of the inlet slots 16. The outer wall of the lance tube 2 serves as additional shear surface, which continues to support the thorough mixing of combustion air and gaseous fuel 9. At the burner outlet 20 itself provides a most homogeneous fuel concentration over the cross section acted upon. It arises at the burner outlet 20, in the combustion chamber formed by a combustion chamber wall 19, a defined cap-shaped reverse flow zone 21, which is headed by ignition occurs. The axial position of the backflow zone 21 is fixed by the axial position of the downstream end of the feed lance. 1 Thus, the backflow is prevented from axially move and pulsate with it.

p0022At part load, when the operation of the premix burner 11 is 16 no longer guaranteed by the injection of gaseous fuel 31 in the region of the tangential slots, gaseous fuel through the nozzle 8 is injected. The gaseous fuel is thereby injected near the backflow zone 21, whereby pulsations between full load and partial load operation are avoided. Next, the required amount of fuel that must be injected through the nozzle 8 is ,, reduced because the fuel is injected directly into the backflow 21st

p0023The cavity between the lance tube 2 and fuel line 3 combustion air 9 is also encouraged. The aided by the lance tube combustion air portion 9a can be up to 25% of the total air flow. By the swirler 6, the combustion air 9a is rotated. The type and strength of the swirl must be adapted to the specific circumstances of the premix burner. For example, the swirler be construed 6 that the swirl generated by him opposite to the swirling of the premix burner 11 runs. This enhances the mixing of combustion air 9, 9a and fuel, and in addition prevents strike back of the Rüchströmzone 21 and thus the flame at the downstream end of the feed lance first

p0024If the premix burner 11 operated with liquid fuel, the fuel is injected by means of the feed lance. 1 This is done by means of the outer channel 5, on the liquid fuel 30 for spraying edge 17 'is promoted. By means of policies supported by the lance tube 2 air 9a thereby an air assisted spray nozzle 22 (eng. Airblast atomizer) formed. To improve the atomization eventually the air must be 9a over the air 9 is further compressed.

p0025Further, liquid fuel through the fuel nozzle 8 are injected. Because of the axial position of the nozzle 8 in the interior of the premix burner 11, the spray angle of the nozzle 8 can be made very large. Characterized the mixing of air 9, 9a and fuel is enhanced.

p0026According to FIG. 5 of the premix burner, at least at the burner outlet 20 fitted with a circular exit being. The two axes 14, 15 of the partial conical bodies 12, 13 must be brought together to, for example to the central axis 10. The circular outlet displaces the reverse 21 is further stabilized and pulsations avoided.

p0027According to FIG. 6 and FIG. 7, for the conversion of the cross section of the premix burner 11 in a circular cross-section at the downstream end of the premix burner 11, an adapter 39 is attached. The inner radius R_i the two partial conical bodies 12, 13 is greater than the exit radius R at the transition to the adapter 39_a of the adapter 39. The height h and the size of the angle α of the adapter 39 are dependent on the entry form into the adapter. 39 The angle α corresponds to the average flow angle, so that no delamination can occur. The through-flow free surface of the adapter 39 is reduced in the direction from the inlet to the outlet of the adapter 39, so here the flow is additionally accelerated by the adapter.

p0028Naturally, the invention is not limited to the embodiment shown and described. The premix can of course be provided with more tangential inlet slots. The feed lance can also be installed in other premix burners as in the double-cone burner. The dual nozzle can also be composed of two nozzles, then the inner feed must be adjusted accordingly. The external fuel supply channel can also be laid from the fuel line in the lance tube.

LIST OF REFERENCE NUMBERS

p0029<dl id="dl0002" compact="compact"><dt>1</dt><dd>feed lance</dd><dt>2</dt><dd>lance tube</dd><dt>3</dt><dd>fuel line</dd><dt>4</dt><dd>internal fuel supply channel</dd><dt>5, 5a</dt><dd>external fuel feed</dd><dt>6</dt><dd>swirler</dd><dt>7</dt><dd>deflecting</dd><dt>8th</dt><dd>fuel nozzle</dd><dt>9, 9a</dt><dd>compressed combustion air</dd><dt>10</dt><dd>central axis</dd><dt>11</dt><dd>premix</dd><dt>12</dt><dd>Partial conical bodies</dd><dt>13</dt><dd>Partial conical bodies</dd><dt>14</dt><dd>cone axis</dd><dt>15</dt><dd>cone axis</dd><dt>16</dt><dd>tangential slots</dd><dt>17</dt><dd>atomization</dd><dt>18</dt><dd>Gas supply line</dd><dt>19</dt><dd>combustion chamber wall</dd><dt>20</dt><dd>burner outlet</dd><dt>21</dt><dd>dome-shaped backflow</dd><dt>22</dt><dd>air-assisted spray nozzle</dd><dt>30</dt><dd>liquid fuel</dd><dt>31</dt><dd>gaseous fuel</dd><dt>39</dt><dd>adapter</dd></dl><dl id="dl0003" compact="compact"><dt>α</dt><dd>average flow angle</dd><dt>R_i</dt><dd>Inner radius partial conical bodies</dd><dt>R_a</dt><dd>Exit radius adapter</dd><dt>H</dt><dd>height adapters</dd></dl>