METHOD FOR OPERATING A COMBUSTION ARRANGEMENT AND COMBUSTION ARRANGEMENT

Abstract

A method for operating a combustion arrangement, the combustion arrangement including at least one combustor chamber arranged in a double-walled housing, at least one inlet configured to supply a fuel to the at least one combustion chamber, at least one outlet for letting exhaust air from the at least one combustion chamber, and at least one air channel configured to feed supply air into the housing, wherein the housing includes an inner wall and an outer wall which jointly define an intermediate space between each other, wherein an air inlet opening that cooperates with the at least one air channel is arranged in an upper end section of the outer wall so that the supply air is feedable through the at least one air channel into the intermediate space.

Claims

1. A method for operating a combustion arrangement, the combustion arrangement including at least one combustion chamber arranged in a double-walled housing, at least one inlet configured to supply a fuel to the at least one combustion chamber, at least one outlet for letting exhaust air from the at least one combustion chamber, and at least one air channel configured to feed supply air into the housing, wherein the housing includes an inner wall and an outer wall which jointly define an intermediate space between each other, wherein an air inlet opening that cooperates with the at least one air channel is arranged in an upper end section of the outer wall so that the supply air is feedable through the at least one air channel into the intermediate space, wherein the intermediate space and the at least one combustion chamber that is enveloped by the inner wall are flow connected so that the supply air conducted into the intermediate space is transferable into the at least one combustion chamber, the method comprising the steps: introducing the supply air into the upper end section of the housing through the at least one air channel; guiding the supply air in the intermediate space towards a lower end section of the housing; introducing the supply air into the at least one combustion chamber; and initially running the supply air out of the housing through an air conduit that cooperates with an air outlet opening arranged in the outer wall; and thereafter running the supply air into the at least one combustion chamber at least indirectly.

2. The method according to claim 1, wherein the intermediate space is divided by an intermediate floor in the lower end section into an upper portion and a lower portion, wherein the supply air is conducted exclusively by the air conduit from the upper portion into the lower portion of the intermediate space.

3. The method according to claim 2, wherein the supply air is run from the lower portion of the intermediate space through at least one transfer opening into the at least one combustion chamber.

4. The method according to claim 1, wherein the supply air is deflected by at least one first air control element when transitioning into the combustion chamber, and wherein a tangential flow component is advantageously imparted upon the supply air by the at least one air control element during the transitioning.

5. The method according to claim 1, wherein the supply air flows from the air inlet opening to the air outlet opening of the outer wall in a downward spiral pattern flow about the inner wall.

6. The method according to claim 5, wherein the supply air is deflected by at least one second air control element within the intermediate space so that the downward spiral pattern flow is generated.

7. The method according to claim 1, wherein the supply air is introduced into the intermediate space with a tangential direction component viewed in a horizontal sectional plane of the combustion arrangement, and wherein a main flow direction of the supply air encloses an angle between 60° and 90° with the outer wall at the air inlet opening.

8. A combustion arrangement configured to burn pellets made from renewable material, the combustion arrangement comprising: at least one combustion chamber arranged in a double-walled housing; at least one inlet for supplying a fuel to the at least one combustion chamber; at least one outlet for letting exhaust air out of the at least one combustion chamber; and at least one an air channel configured to feed supply air into the housing, wherein the housing includes an inner wall and an outer wail which jointly define an intermediate space between each other, wherein an air inlet opening that cooperates with the at least one air channel is arranged in an upper end section of the outer wall so that the supply air is feedable through the at least one air channel into the intermediate space, wherein the intermediate space and the at least one combustion chamber that is enveloped by the inner wall are flow connected so that the supply air conducted into the intermediate space is transferable into the at least one combustion chamber, wherein a first end of an air conduit cooperates with an air outlet opening that is arranged in the outer wall in a lower end section of the housing, wherein at least an outer section of the air conduit extends outside of the housing, and wherein the supply air is conductible from the air outlet opening into the combustion chamber at least indirectly.

9. The combustion arrangement according to claim 8, wherein the intermediate space is divided by an intermediate floor into an upper portion and a lower portion, and wherein the supply air is conducted exclusively through the air conduit from the upper portion into the lower portion.

10. The combustion arrangement according to claim 9, wherein the inner wall includes a plurality of transfer openings that provide a flow connection between the lower portion of the intermediate space with the at least one combustion chamber.

11. The combustion arrangement according to claim 8, wherein the outer wall includes a pass-through opening, and wherein the supply air is feedable by the air conduit through the pass-through opening into the intermediate space.

12. The combustion arrangement according to claim 8, wherein a center axis of the at least one air channel encloses an angle between 60° and 90° with the outer wall at the air inlet opening.

13. The combustion arrangement according to claim 8, wherein air control elements are arranged in the intermediate space at the inner wall.

14. The combustion arrangement according to claim 13, wherein the air control elements are formed by guide plates.

15. The combustion arrangement according to claim 8, wherein the intermediate space is divided into a wide portion and a narrow portion, and wherein a horizontally measured extension of the intermediate space in the wide portion is greater than in the narrow portion.

16. The combustion arrangement according to claim 15, wherein the air inlet opening cooperates with the wide portion and the air outlet opening cooperates with the narrow portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention is now described based on embodiments with reference to drawing figures, wherein:

[0031] FIG. 1 illustrates a vertical cross-sectional view of the combustion arrangement according to the invention;

[0032] FIG. 2 illustrates a horizontal cross-sectional view of a lower portion of the combustion arrangement according to FIG. 1;

[0033] FIG. 3 illustrates a vertical cross-sectional view of another embodiment of the combustion arrangement according to the invention; and

[0034] FIG. 4 illustrates a horizontal cross-sectional view of the combustion arrangement according to FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0035] A first embodiment that is shown in FIGS. 1 and 2 includes a combustion arrangement 1 that includes a combustion chamber 3 that is defined by a housing 2 with a circular cross section. The combustion arrangement 1 includes a supply conduit through which a fuel, in particular in a form of pellets is feedable to a combustion table 27 within the combustion chamber 3. A supply conduit 4 is run through the housing 2. The housing 2 is configured double walled and includes an external outer wall 8 and an internal inner wall 7. The outer wall 8 and the inner wall 7 jointly define an intermediate space 9 arranged there between. The combustion arrangement 1 according to the invention further comprises an outlet 5 that is arranged at a ceiling 36 of the housing 2. The outlet 5 is configured to let out exhaust gases, in particular smoke gasses that are generated by the combustion of the respective fuel in the combustion chamber 3.

[0036] Typically, a combustion arrangement 1 of this type includes at least one heat exchanger arrangement by which thermal energy released by the combustion is transferrable to a heat transfer medium. The heat transfer medium is typically formed by water wherein the heat exchanger arrangement can be formed e.g. by a water spiral that extends in a helical shape within the combustion chamber 3 wherein the water spiral is flow enveloped by hot exhaust gases of the combustion that occurs in the combustion chamber 3. Thermal energy included in the exhaust gas can be transferred in the water spiral to the heat transfer medium which is thus heated by a large amount. In particular, the heat transfer medium is initially evaporated and the steam superheated e.g.; to a temperature about 500° C. Thus, energy included in the respective fuel is converted into thermal energy and then rendered mechanically useable wherein a turbine is drivable by the steam, typically water steam. Exhaust gas that exits the combustion arrangement 1 is also usable for pre-drying a fuel that is to be combusted.

[0037] An air channel 6 is connected to the intermediate space 9, wherein supply air is conductible by the air channel 6 through an air inlet opening 10 into the intermediate space 9. The air inlet opening 10 is arranged in an upper end section 14 of the housing 2, wherein the air inlet opening 10 is advantageously arranged directly below a ceiling 36 of the housing 2. The supply air flows initially into the air channel 6 in a main flow direction 16 that is parallel to a center axis 24 of the air channel 6 before the supply air is deflected into the intermediate space 9 by air control elements 26, 31. The air control elements 26, 31 are arranged in the intermediate space 9 and configured to force the supply air into a spiral flow about the inner wall 7. This is based on the concept that the supply air is heatable by flowing about the inner wall 7 wherein the inner wall 7 has a high temperature due to the combustion in the combustion chamber 3. Thus, the supply air is run from the air inlet opening 10 within the intermediate space 9 downward towards a lower end section 15 of the housing 2 and thus heated.

[0038] The air control elements 26, 31 are configured differently in the illustrated embodiment. In particular the air control elements 26 are associated with an upper wide portion 34 of the housing 2 whereas the air control elements 31 are associated with a narrow portion 33. The wide portion 34 and the narrow portion 33 differ in a width of the intermediate space 9 that is measured in the radial direction. The housing 2 is configured in the illustrated embodiment so that a diameter of the outer wall 8 is configured constant over the entire height of the housing 2. The inner wall 7, however, is configured with a variable diameter wherein the inner wall 7 has a small diameter in the wide portion 34 and a large diameter in the narrow portion 33. This has the consequence that radially measured distance between the inner wall 7 and the outer wall 8 that corresponds to a width of the intermediate space 9 which is greater in the wide portion 34 than in the narrow portion 33. The wide portion 34 is typically associated with the upper end section 14 in which the air inlet opening 10 of the air channel 6 is arranged. The wide portion 34 has the advantage that enough space is available in the intermediate space 9 to arrange comparatively large air control elements 26. The air control elements are configured to impart a helical flow pattern upon the supply air wherein the air control elements are arranged with a corresponding orientation at the inner wall 7. Thus, the air control elements 26 are formed by plate shaped components that extend from the inner wall 7 in a direction towards the outer wall 8. The air control elements 26 can be inclined at least partially relative to vertical in order to provide a deflection of the main flow direction 16 of the supply air downward at a slant angle.

[0039] As soon as the spiral flow of the supply air is set in motion additional measures to maintain the spiral flow only require smaller air control elements 31. These are arranged in the narrow portion 33 and formed in the illustrated embodiment by elongated air control plates that are adapted to a camber of the inner wall 7. These air control plates can extend essentially horizontally viewed in particular in the circumferential direction of the inner wall 7 or can be configured slightly inclined relative to horizontal in particular inclined by less than 10°, advantageously by less than 5°. Advantageously a portion of the air control elements 31 is arranged horizontal while another portion of the air control elements 31 is inclined relative to horizontal. This way air channels are formed along the inner wall 7 in the narrow portion 33 that maintain the spiral flow of the supply air about the inner wall 7 wherein a slope of the flow is kept small enough so that an air conduction path and thus a dwelling time of the supply air at the inner wall 7 when flowing through the intermediate space 9 is configured as long as possible. This assures that a strong heat transfer occurs from the inner wall to the supply air which heats the supply air by a particularly strong amount. The latter is particularly advantageous for a combustion of highly compressed solid fuels in the combustion chamber 3. The large diameter of the inner wall 7 in the narrow portion 43 makes the circumferential surface of the inner wall 7 particularly large so that the air conduction path along which the supply air flows around the inner wall 7 is particularly long.

[0040] The outer wall 8 includes an air exit opening 12 in the lower end section 15 that is arranged below the upper end section 14 wherein the air outlet opening 12 cooperates with the air conduit 11. The air outlet opening 12 is arranged in the narrow portion 33. The air conduit 11 is configured to conduct the supply air from the intermediate space 9 in a radially outward direction out of the housing 2. Put differently, the air conduit 11 extends in an environment 23 of the housing 2. The air conduit 11 is connected with its first end 18 at the air outlet opening 12. A second end 19 of the air conduit 11 cooperates with a pass through opening 22 which is arranged in the outer wall 8 of the housing 2. The air conduit 11 is formed as a 180° arc that is vertically oriented wherein both ends 18, 19 of the arc are arranged at different elevation levels. An outer section 21 of the air conduit 11 extends between the air outlet opening 12 and the pass through opening 22 wherein the outer section forms the entire air conduit 11 in the illustrated embodiment.

[0041] In the illustrated embodiment the intermediate space 9 is divided by an intermediate floor 28 into an upper portion 29 and a lower portion 30. The intermediate floor 28 is configured to separate a flow in the upper portion 29 and the lower portion 30 of the intermediate space 9. A flow of the supply air can thus only be provided from the upper portion 29 into the lower portion 30 using the air conduit 11. Thus, the air outlet opening 12 cooperates with the upper portion 29 and the pass through opening 22 cooperates with the lower portion 30 of the intermediate space 9. Accordingly, the air conduit 11 represents the only flow connection between the upper portion 29 and the lower portion 30. The pass through opening 22 feeds the supply air to the lower portion 30 of the intermediate space 29. The supply air is then fed from the lower portion 30 through a plurality of pass through openings 13 that are arranged in the inner wall 7 into the combustion chamber 3. Within the combustion chamber 3 the supply air is eventually conducted into the fire 25 so that the supply air is available as a reaction partner for the combustion reaction of the respective fuel.

[0042] As evident from FIG. 2, that shows a horizontal cross-section through the housing 2 in the lower portion 30 the supply air is deflected by an air control element 37 during a transition of the supply air from the air conduit 11 into the intermediate space 9 so that the main flow direction 16 of the supply air is provided with a tangential flow component. This causes the supply air to flow in a circular pattern from the pass through opening 22 within the intermediate space 9 about the inner wall 7. The pass through openings 13, wherein five of them are distributed in the illustrated embodiment in a uniform pattern about the circumference of the inner wall 7, respectively offset from each other by 72 degrees, facilitate a transfer of the supply air into the combustion chamber 3. Thus, the transfer openings 13 are configured as horizontal slots that form a flow resistor for the supply air. This way the transfer openings 13 act as throttles that lead to a local increase of the flow velocity of the supply air when entering the combustion chamber 3. The transfer openings 13 also cooperate with air conducting elements 32 that provide a tangential flow of the supply air into the combustion chamber 3. Due to the oxygen consumption of the fire 25 the supply air is eventually sucked into the fire 25 by a vacuum formed in the fire 25. Thus, a tangential flow component of the supply air is maintained long as possible.

[0043] In another advantageous embodiment that is illustrated in FIGS. 3 and 4 the essential difference to the embodiment according to FIGS. 1 and 2 is that supply air is conducted directly from the intermediate space 9 through the air conduit 11 directly into the combustion chamber 3. Thus, the air conduit 11 is run from the air exit opening 12 in the lower end section 15 of the housing 2 away from the housing 2 and then passes through the outer wall 8 in the portion of a pass-through opening 22. Thereafter the air conduit 11 extends from the pass-through opening 22 through the intermediate space 9 and terminates at a transfer cross section 13 where the second end 19 of the air conduit 11 is connected. The air conduit 11 includes an outer section 21 that extends outside of the housing 2 and an inner section 20 that extends within the housing 2, more precisely within the intermediate space 9. This configuration causes the spiral shaped main flow direction 16 of the supply air that prevails in the intermediate space 9 to be interrupted or stopped since the supply air is forced into the air conduit 11 which forces the supply air into a flow within the air conduit 11. The housing 2 is dosed in its upper end section 15 so that supply air can only exit through the air conduit 11 from the intermediate space 9. Since the air conduit 11 is directly connected to the combustion chamber 3 as described supra flowing the supply air from the air conduit 11 into the combustion chamber 3 facilitates controlling the main flow direction 16 of the supply air. In particular it is conceivable to connect the air conduit 11 to the inner wall at a slant angle relative to the inner wall so that the main flow direction 16 of the supply air is oriented at an angle 35 relative to the transmission cross section 13. The angle 35 is approximately 60° so that a tangential flow component is imparted upon the supply air. This causes the supply air to flow around the combustion table 27 in a circular pattern or in a vortex which has proven particularly advantageous for the combustion of highly compressed solid fuels.

[0044] Independently from the direct connection of the air conduit 11 at the inner wall 7 the intermediate space 9 is configured with a constant cross section over an entire height of the housing 2 in the second embodiment. Generating a spiral flow in the portion of the intermediate space 9 is achieved at least initially by a slanting of the air channel 6 relative to the outer wall 8. This slanting is done so that the main flow direction 16 of the supply air that is oriented parallel to the center axis 24 of the channel 6 encloses and angle 17 of about 70° with a plane of the air inlet opening 10. This way the supply air is already conductible into the intermediate space 9 with a tangential flow component, wherein the housing 12 develops a downward flow pattern of the supply air due to the arrangement of the air outlet opening 12 in the lower end section 15 of the housing 2. As a result, this yields the spiral shaped flow characteristics of the supply air from the air inlet opening 10 to the air outlet opening 12.

REFERENCE NUMERALS AND DESIGNATIONS

[0045] 1 combustion arrangement

[0046] 2 housing

[0047] 3 combustion chamber

[0048] 4 inlet

[0049] 5 outlet

[0050] 6 air conduit

[0051] 7 inner wall

[0052] 8 outer wall

[0053] 9 intermediate space

[0054] 10 air inlet opening

[0055] 11 air conduit

[0056] 12 air outlet opening

[0057] 13 transition opening

[0058] 14 upper end section

[0059] 15 lower end section

[0060] 16 main flow direction

[0061] 17 angle

[0062] 18 first end

[0063] 19 second end

[0064] 20 inner section

[0065] 21 outer section

[0066] 22 pass through opening

[0067] 23 ambient

[0068] 24 center axis

[0069] 25 fire

[0070] 26 air control element

[0071] 27 combustion table

[0072] 28 intermediate floor

[0073] 29 upper portion

[0074] 30 lower portion

[0075] 31 air control element

[0076] 32 air control element

[0077] 33 narrow portion

[0078] 34 wide portion

[0079] 35 angle

[0080] 36 ceiling

[0081] 37 air control element