Abstract
In accordance with the flow distribution of combustion gas including an unburned portion, an after-air port (AAP) arranged downstream of the two-stage combustion burner can effectively reduce the unburned portion by dividing as appropriate so as to avoid interaction, and by mixing together, two types of after-air having functions of linearity and spreading. As the configuration of this AAP, a primary nozzle for supplying primary after-air and having a vertical height greater than the horizontal width is provided in the center in the opening of the AAP, a secondary nozzle for supplying secondary after-air is provided in the opening outside of the primary nozzle, and one or more secondary after-air guide vanes having a fixed or variable tilt angle relative to the after-air port center axis are provided at the outlet of the said secondary nozzle to deflect and supply the secondary after-air horizontally to the left or right.
Claims
1. A combustion device in which burners are disposed on a furnace wall to burn fuel with an amount of air of theoretical air or less, and after-air ports to supply air are disposed on the furnace wall in the downstream side from the position where the burners are disposed, the combustion device characterized in that it comprises: a primary after-air nozzle (5) which is provided at the central part in an opening (17) of the after-air port with larger vertical height than horizontal width to supply a primary after-air (1); secondary after-air nozzles (14) which are provided in the opening (17) of the after-air port at the outside of the primary after-air nozzle (5) to supply a secondary after-air (11); and one or more pairs of secondary after-air guide vanes (15) which are provided in the outlet parts of the secondary after-air nozzles (14) and have inclination angles with respect to a central axis of the after-air port, so as to deflect the secondary after-air (11) right and left in the horizontal direction and supply the same.
2. The combustion device according to claim 1, characterized in that the primary after-air nozzle (5) includes one or more primary after-air guide vanes (8) which are provided in the outlet part thereof and are configured to control an inclination angle thereof in the horizontal direction or upward from the horizontal direction, so as to supply the primary after-air (1) upward with an inclination angle.
3. The combustion device according to claim 1, characterized in that the secondary after-air guide vanes (15) all have the same inclination angles with respect to the central axis of the after-air port.
4. The combustion device according to claim 1, characterized in that each of the secondary after-air guide vanes (15) has a deviation in the inclination angles thereof with respect to the central axis of the after-air port.
5. The combustion device according to claim 4, characterized in that the secondary after-air guide vanes (15) have inclination angles becoming larger with increasing distance away from the primary after-air nozzle (5) with respect to the central axis of the after-air port.
6. The combustion device according to claim 1, characterized in that the secondary after-air guide vanes (15) are configured to change the inclination angles thereof.
7. The combustion device according claim 1, characterized in that the secondary after-air guide vanes (15) are configured to move in the anteroposterior direction of the furnace wall.
8. The combustion device according to claim 1, characterized in that a first guide member (16) is provided at a portion nearest the primary after-air nozzle (5), to supply a small amount of secondary after-air (11) along a surface of the secondary after-air guide vane (15) on the furnace side thereof and the outer surface of the tip part of the primary after-air nozzle (5).
9. The combustion device according to claim 1, characterized in that the openings (17) of the after-air port have spreading parts (18) of a shape whose end spreads toward the furnace, and are respectively provided with second guide members (19) to supply a small amount of the secondary after-air (11) along surfaces of the spreading parts (18).
10. The combustion device according to claim 1, characterized in that any one or both of an inlet part of the primary after-air nozzle (5) and inlet parts of the secondary after-air nozzles (14) are provided with air flow rate control functional members to change a flow path resistance.
11. The combustion device according to claim 1, characterized in that the primary after-air nozzle (5) includes a contracting member (5a) having a flow passage cross-sectional area gradually decreased in a flow direction of air, which is attached to the inlet part thereof.
12. The combustion device according to claim 1, characterized in that the primary after-air nozzle (5) includes a contracting member (5b) having a horizontal width gradually decreased in a flow direction of air, which is attached to the tip part thereof.
13. The combustion device according to claim 1, characterized in that any one or both of the primary after-air nozzle (5) and the secondary after-air nozzles (14) include rectifiers installed in flow passages thereof.
14. The combustion device according to claim 1, characterized in that the opening (17) of the after-air port is formed in a rectangular shape.
15. The combustion device according to claim 1, characterized in that the opening (17) of the after-air port is formed in a polygonal shape.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) FIG. 1 is a front view of an after-air port according to one example of the present invention as viewed from the furnace side (FIG. 1(a)), and a view taken in the arrow direction of line A-A in FIG. 1(a) (FIG. 1(b)).
(2) FIG. 2 is a plan sectional view of a left half of a tip part of the after-air port according to one example of the present invention (FIG. 2(a)), and a plan sectional view of a left half of a tip part of an after-air port known in the related art (Patent Literature 1) (FIG. 2(b)).
(3) FIG. 3 is a plan sectional view of a left half of a tip part of an after-air port according to another example of the present invention.
(4) FIG. 4 is a plan sectional view of a left half of a tip part of an after-air port according to another example of the present invention in a case of relatively increasing an inclination angle of secondary after-air guide vanes (FIG. 4(a)), and a plan sectional view of the left half thereof in a case of relatively decreasing the inclination angle of the secondary after-air guide vanes (FIG. 4(b)).
(5) FIG. 5 is a view illustrating an operation mechanism of the secondary after-air guide vanes of the after-air port according to another example of the present invention.
(6) FIG. 6 is a plan sectional view of a left half of a tip part of an after-air port according to another example of the present invention, when the secondary after-air guide vanes are inserted to the furnace side (FIG. 6(a)), and a plan sectional view of the left half of the tip part thereof, when the secondary after-air guide vanes are pulled out from the furnace side (FIG. 6(b)).
(7) FIG. 7 is a plan sectional view of a left half of a tip part of an after-air port according to another example of the present invention, when a guide member is not installed in a secondary after-air nozzle (FIG. 7(a)), and a detailed plan sectional view of the left half of the tip part thereof around the guide member, when a first guide member is installed in the secondary after-air nozzle (FIG. 7(b)).
(8) FIG. 8 is a plan sectional view of a left half of a tip part of an after-air port according to another example of the present invention in a case of without a primary after-air nozzle outlet contracting member (FIG. 8(a)), and a plan sectional view of the left half of the tip part thereof in a case of including the primary after-air nozzle outlet contracting member (FIG. 8(b)).
(9) FIG. 9 is a front view of an after-air port having a rectangular opening according to another example of the present invention (FIG. 9(a)), and a cross-sectional view taken in the arrow direction of line A-A in FIG. 9(a) (FIG. 9(b)).
(10) FIG. 10 is a front view of an after-air port having a hexagonal opening according to another example of the present invention (FIG. 10(a)), and a cross-sectional view taken in the arrow direction of line A-A in FIG. 10(a) (FIG. 10(b)).
(11) FIG. 11 is a front view of an after-air port according to another example of the present invention (FIG. 11(a)), a cross-sectional view taken in the arrow direction of line A-A in FIG. 11(a) (FIG. 11(b)), and a cross-sectional view taken in the arrow direction of line B-B in FIG. 11(a) (FIG. 11(c)).
(12) FIG. 12 is a view for describing a difference in a penetration force within the furnace due to a difference in the inclination angle of the primary after-air guide vanes in the after-air port of FIG. 1.
(13) FIG. 13 is a view for describing the difference in the penetration force within the furnace when a flow rate ratio of a primary after-air to a secondary after-air is set to be 8:2 in the after-air port of FIG. 1.
(14) FIG. 14 includes a front view of a furnace wall in which burners and the after-air ports are disposed (FIG. 14(a)), a side sectional view thereof (FIG. 14(b)), and a plan sectional view thereof (FIG. 14(c)).
(15) FIG. 15 includes a front sectional view of the furnace for describing a flow rate distribution of the rising gas in a horizontal section in the furnace immediately below the after-air ports illustrated in FIG. 14 (FIG. 15(a)), and a side sectional view thereof (FIG. 15(b)).
(16) FIG. 16 is views illustrating concentration distributions of the after-air in the vertical plane passing through the central axis of the air port due to difference in an outlet shape of the after-air ports installed on the furnace wall (FIG. 16(a)), and views illustrating the concentration distribution of the after-air in the surface orthogonal to the central axis of the air port in a furnace depth center (FIG. 16(b)).
DESCRIPTION OF EMBODIMENTS
(17) Before describing specific examples of the present invention, FIG. 16, which is views illustrating shapes (a concentration distribution) of an after-air jets, when supplying after-air through nozzles having openings with various shaped cross-sections at the same velocity among combustion gas flowing upward in the furnace, will be described.
(18) FIG. 16 illustrates numerical flow analysis results, wherein FIG. 16(a) illustrates the shapes and the concentration distributions of the after-air jets in the vertical plane passing through the air port central axis Co (see FIG. 2) in relation to difference in the outlet shapes of the after-air ports installed on the furnace wall, and FIG. 16(b) illustrates the shapes and the concentration distributions of the after-air jets in the plane orthogonal to the air port central axis Co at the furnace depth center. The left parts of FIGS. 16(a) and (b) illustrate the scope of the analysis model.
(19) The present analysis model covers a range obtained by cutting a portion of the furnace including one after-air port, which is a rectangular body having a width of 4 m, a height of 13 m, and a depth of 8 m. Herein, the after-air port is installed in a widthwise center at a position of a height of 3 m from the bottom, and the after-air is supplied in a direction illustrated by an arrow in FIG. 16(a) from the after-air port. The furnace depth is 16 m, and a position of 8 m from the after-air port is the center in the depth direction, and this model is set to be a half in the depth direction. The boundary on both sides and a depth side of the model scope is defined as a condition of a mirror symmetry, and it is possible to simulate an actual flow in the furnace.
(20) In addition, FIGS. 16(a) and (b) illustrate the scope of the analysis model in the left portion thereof, and contrasting densities (actually expressed by a difference in color) obtained by representing an air concentration of the after-air in a strip shape and showing it in a dimensionless way as an after-air mass distribution in the right portion thereof. It is shown in red toward the top and in blue toward the bottom, the top is 100% and the bottom is 0%.
(21) The combustion gas rising from a burner (not illustrated) is defined as flow upward at uniform velocity for simplification. As illustrated in FIG. 16, an after-air supply nozzle has a cross-sectional shape of total of seven types including: (vii) horizontally long rectangular shape (an aspect ratio of 1:2, wherein vertical of the aspect ratio refers to the vertical length of the nozzle, and horizontal thereof refers to the horizontal length of the nozzle); (vi) a circular shape; and (i) to (v) vertically long rectangular shapes (five types of aspect ratios of (v) 3:2, (iv) 2:1, (iii) 3:1, (ii) 4:1 and (i) 5:1).
(22) The cross-sectional area and an ejected flow rate of the after-air supply nozzle (hereinafter, simply referred to as a nozzle) are the same for all the seven types of nozzles. The jet of after-air injected into the furnace is bent to the upper side due to the flow of the combustion gas rising in the furnace. The cross-sectional shape of the after-air immediately after the injection is the same as the nozzle, but as the horizontal length of the shape is larger, it may be easily affected by the combustion gas flow rising in the furnace, and may be bent rapidly upward. That is, after-air jets are bent by the combustion gas flow rising in the furnace rapidly to the upper side in an order of a horizontally long rectangular, circular, and vertically long rectangular.
(23) In the case that the aspect ratio of the nozzle is larger than 3:1 (3/1), a saturation tendency is observed in the characteristics that the after-air jet is bent to the upper side due to an increase in a resistance of both sides of the jet. The rising combustion gas flow bent to the upper side is the model which is referred to as the mirror symmetry in the furnace depth direction, such that the jets injected from the after-air ports 7a which are disposed in a pair of the opposed furnace walls collide at the position of 8 m which is a central position in the furnace depth direction (the position recessed to 8 m from the furnace wall in the depth direction), and then rise upward.
(24) Mixing and combustion reaction of the combustion gas containing the after-air and unburned components proceed in the upper side of the after-air jet. If the after-air jet is rapidly bent to the upper side, a space from the after-air jet required for mixing and combustion reaction to the furnace outlet is decreased, and as a result, an unburned component residual rate is increased. Reversely, when it is difficult for the after-air jet to be bent to the upper side, it is possible to secure the space from the after-air jet required for mixing and combustion reaction to the furnace outlet, and the unburned component residual rate is kept low.
(25) When supplying the after-air using a nozzle having a shape with a small horizontal width and a large vertical height, it is possible to reduce an influence of the flow of the combustion gas rising in the furnace, improve penetration thereof due to bending of the flow of the combustion gas to the upper side being reduced, and secure the space from the after-air jet to the furnace outlet, which is required for mixing and combustion reaction of the combustion gas containing unburned components and the after-air, such that it is possible to achieve high efficiency combustion with a lower residual rate of the unburned components.
(26) In addition, only by using the nozzle having a shape with a small horizontal width and a large vertical height, it is effective for reducing the unburned components. However, by effectively supplying the after-air to the combustion gas containing the unburned components of the region (the regions C illustrated in FIG. 15(b)) in the vicinity of the furnace front wall and the furnace rear wall between the after-air jets, high efficiency combustion with being further reduced the unburned components can be realized.
(27) The above-described problems in Patent Literature 1 and Patent Literature 2 will be additionally described based on a difference in the flow pattern in the furnace of the jet due to a difference in the jet shape.
(28) When applying the after-air port structure according to Patent Literature 1, an after-air jet having an integral type of an end-spreading shape in the horizontal direction is formed, and the cross-sectional shape of the after-air jet immediately after the injection becomes a horizontally wide shape (with a small aspect ratio), and as illustrated in FIG. 16 (a)(vii) and FIG. 16 (b)(vii), is rapidly bent to the upper side due to the rising gas flow in the furnace. Therefore, it cannot be said that this kind of after-air jet is an appropriate shape for maintaining the penetration.
(29) The present invention defines the after-air port which has two functions of a primary after-air (1) governing the penetration and a secondary after-air (11) governing the spreadability, but which is basically different from the invention described in Patent Literature 1 in terms of that, by completely separating two types of after-air jets having the penetration and the spreadability to cut off the continuity of the two types of jets, and by eliminating the interaction between the two types of jets, it is possible to maintain the penetration and the spreadability.
(30) When applying the after-air port structure according to the invention described in Patent Literature 2, the after-air jet of the after-air port outlet part has a circular cross-sectional shape, and as compared to FIG. 16 (a)(vi) and FIG. 16 (b)(vi) and the rectangular shape having a large vertical/horizontal ratio (FIG. 16 (a)(i) to (v) and FIG. 16 (b)(i) to (v)), the penetration is deteriorated, and there is room for improvement.
EXAMPLE 1
(31) FIG. 1 illustrates an after-air port according to one example of the present invention, wherein FIG. 1(a) is a front view as viewed from the furnace (31) side, and FIG. 1(b) is a cross-sectional view taken in the arrow direction of line A-A in FIG. 1(a).
(32) In the after-air port illustrated in FIG. 1, after-air in a wind box (30) for after-air (the wind box (30) represents an entire space surrounded by a wind box casing (32) and the furnace wall) is divided into primary after-air (1) and secondary after-air (11), and the primary after-air (1) and the secondary after-air (11) are supplied to the furnace (31) via a primary after-air nozzle (5) and secondary after-air nozzles (14), respectively. The primary after-air nozzle (5) includes a primary after-air nozzle inlet contracting member (5a) which is installed in an inlet thereof and has a cross-sectional area gradually decreased toward the flow direction, to suppress a pressure loss in the inlet of the primary after-air nozzle (5). Further, the primary after-air nozzle (5) includes primary after-air flow rate control dampers (3) which are installed in the inlet part thereof and are capable of changing a flow path resistance, to optimally control the flow rate of the primary after-air (1).
(33) The primary after-air nozzle (5) includes a primary after-air rectifier (4) which is installed inside thereof and made of a plate material provided with a plurality of through holes. Even when deviation in the velocity distribution may exist in the primary after-air (1) at the inlet part of the primary after-air nozzle (5), it is uniformly rectified to a uniform flow by the primary after-air rectifier (4), and thus the primary after-air (1) is supplied to the furnace (31) as a jet having a stable penetration.
(34) In addition, the secondary after-air nozzles (14) include secondary after-air flow rate control dampers (12) which are installed in the inlet parts thereof and are capable of changing the flow path resistance, thereby enabling the optimum control of the flow rate of the secondary after-air (11). Secondary after-air rectifiers (13), which are made of plate material provided with a plurality of through holes, are installed in the outlets of the secondary after-air flow rate control dampers (12). Even when deviation in the velocity distribution may occur at the inlet parts of the secondary after-air nozzles (14), it is uniformly rectified to uniform flows by the secondary after-air rectifiers (13) and introduced via secondary after-air guide vanes (15), and thus the secondary after-air (11) is supplied to the furnace (31) as jets having a stable penetration.
(35) The primary after-air nozzle (5) may include one or more partition plates (not illustrated) provided inside thereof and having flat plates in a gas flow direction, instead of the primary after-air rectifier (4), such that a rectifying effect can be obtained by separating the inside of the primary after-air nozzle (5) into a plurality of flow passages. Even when deviation in the velocity distribution may exist at the inlet part of the primary after-air nozzle (5), it is rectified to a straight flow, and thus the primary after-air (1) is supplied to the furnace (31) as a jet having a stable penetration.
(36) Herein, a difference in the flow of the after-air jet at the outlet part of the after-air port between the present example and the above-described invention stated in Patent Literature 1 will be again described using FIG. 2. FIG. 2 shows views for comparing plan cross-sections of structure examples of tip parts of the after-air ports and jet pattern examples of the outlet part with left halves from the central axes, between the present example (FIG. 2(a)) and the invention described in Patent Literature 1 (FIG. 2(b)).
(37) In the after-air port by the invention described in Patent Literature 1, as illustrated in FIG. 2(b), the flow direction of the after-air is straight in the vicinity of the central axis of an after-air main flow (1a), but gradually spreads toward the horizontal outside, to form a continuous united after-air jet with an after-air sub flow (1b) separated from the after-air main flow (1a) by an air separation plate (25). Compared to this, in the after-air port by the present example, as illustrated in FIG. 2(a), the primary after-air (1) flowing through the primary after-air nozzle (5) and the secondary after-air (11) flowing through the secondary after-air nozzles (14) are present as independent jets having two type directions of a straight direction and a direction with an horizontal inclination angle, and a circulation vortex (11a) which is a pair of secondary flows is formed therebetween. As seen above, due to the flow pattern of the after-air (1) and (11) in the present example, the penetration and the spreadability of the after-air (1) and (11) is maintained. Further, a formation of the above-described secondary flow (circulation vortex) (11a) is a phenomenon in which the combustion gas around the after-air (1) and (11) are accompanied by (drawn in) the jets of the primary after-air (1) and the secondary after-air (11), and plays an important role in terms of facilitating the mixing of the combustion gas containing the unburned components with the after-air (1) and (11).
EXAMPLE 2
(38) FIG. 3 illustrates an after-air port according to a second example of the present invention (illustrating a left half thereof). In the present example, the secondary after-air nozzles (14) has three secondary after-air guide vanes (15) on right and left, respectively. An inclination angle of the secondary after-air guide vanes (15) with respect to an axis C.sub.1 parallel to the after-air port central axis C.sub.0 becomes larger with increasing distance away from the primary after-air nozzle (5). The secondary after-air jets supplied into the furnace (31) with a direction being changed by the secondary after-air guide vanes (15) on the sides away from the primary after-air nozzle (5) are supplied to regions near the opposed furnace front and rear walls, and the secondary after-air jets supplied into the furnace (31) with a direction being changed by the secondary after-air guide vanes (15) on the sides near the primary after-air nozzle (5) are supplied to the regions away from the furnace front and rear walls, such that it is possible to supply the secondary after-air (11) to a wider region.
EXAMPLE 3
(39) FIG. 4 illustrates a third example of the present invention (illustrating a left half thereof). Three secondary after-air guide vanes (15) are installed on right and left, respectively, and rotation shafts (22) which pivot the secondary after-air guide vanes (15) to determine the inclination angle thereof are integrally provided in base parts of the secondary after-air guide vanes (15). Due to the rotation shaft (22), the secondary after-air guide vanes (15) are rotatably provided in a fixing member (15a).
(40) FIG. 5 in a view illustrating an operation mechanism of the secondary after-air guide vanes (15).
(41) A link (23) is also movable from side to side, and the inclination angle of the secondary after-air guide vanes (15) is changed in conjunction therewith. The rotation shafts (22) are pivotably attached to the fixing members (15a), and link rotation shafts (24) fixed to the tip of a lever (20) are pivotably provided in the link (23), such that the link (23) may move forward and backward by the lever (20).
(42) The three secondary after-air guide vanes (15) are connected to the secondary after-air guide vane link (23) which connects the central parts of the respective guide vanes (15), and the link rotation shafts (24) which are provided in connection parts of the link (23) with the secondary after-air guide vanes (15). The inclination angle of the three secondary after-air guide vanes (15) may be simultaneously changed by pivoting the link rotation shafts (24) through the link (23) by an operation lever (20) which is provided by extending the tip of an operation member to the outside of the wind box casing (32).
(43) With the secondary after-air guide vane operation lever (20) being pulled out (FIG. 4(a)), the spreading inclination angle of the secondary after-air guide vanes (15) is relatively increased, and the secondary after-air jet is close to the furnace front (rear) wall. Reversely, with the secondary after-air guide vane operation lever (20) being inserted (FIG. 4(b)), the spreading inclination angle of the secondary after-air guide vanes (15) is relatively decreased, and the secondary after-air jet is separated from the furnace front (rear) wall.
(44) As described above, by controlling the position of the secondary after-air guide vane operation lever (20) in the back and front of the furnace wall surface, it is possible to optimally set the direction of the secondary after-air (11) to be deflected in a horizontal direction near the furnace wall surface. Since the secondary after-air guide vane operation lever (20) is installed by penetrating the wind box casing (32) for after-air, a secondary after-air guide vane operation lever through part seal (21) is provided in the wind box casing (32), so as to prevent the after-air from being leaked to the outside of the wind box (30).
EXAMPLE 4
(45) FIG. 6 illustrates a fourth example of the present invention. Both of FIGS. 6(a) and (b) illustrate a left half of the after-air port plan horizontal cross-section, wherein FIG. 6(a) illustrates a case in which the secondary after-air guide vanes (15) is inserted toward the furnace side by the operation lever (20), and FIG. 6(b) illustrates a case in which the secondary after-air guide vanes (15) is pulled out from the furnace. Further, the same components as the members described in FIG. 1, and the like will be denoted by the same reference numerals, and therefore will not be described.
(46) The secondary after-air guide vanes (15) illustrated in FIGS. 6(a)(b) are fixed to the fixing member (15a) so as not to be rotated.
(47) With the secondary after-air guide vane operation lever (20) being inserted (FIG. 6(a)), the tip of the secondary after-air guide vanes (15) is inserted to a position of the furnace front (rear) wall, and the secondary after-air (11) is injected along the set inclination angle of the secondary after-air guide vanes (15) with no influence by the an after-air port opening spreading part (throat part) (18).
(48) With the secondary after-air guide vane operation lever (20) being pulled out (FIG. 6(b)), the tip of the secondary after-air guide vanes (15) is a position in which it moves from the furnace front (rear) wall to the wind box (30) side, and the secondary after-air (11) is affected by the after-air port opening spreading part (18). The secondary after-air (11) supplied from the outside of the secondary after-air guide vanes (15) farthermost from the primary after-air nozzle (5) forms a flow while suppressing the spread along an inner surface of the after-air port opening spreading part (18).
(49) The influence of the after-air port opening spreading part (18) also affects the secondary after-air (11) supplied from the secondary after-air guide vanes (15) on the side near the primary after-air nozzle (5), and as compared to FIG. 6(a), the secondary after-air jet is supplied in a direction toward the inside of the furnace away from the furnace front (rear) wall as a whole.
(50) Therefore, by controlling the position of the secondary after-air guide vane operation lever (20) in the back and front, it is possible to control an influence degree of the after-air port opening spreading part (18), and optimally set the direction of the secondary after-air (11). In the present example, since the direction of the secondary after-air (11) is controlled using the influence of the after-air port opening spreading part (18), the spreading inclination angle of the after-air port opening spreading part (18) is set to be smaller than that of the example disclosed in FIG. 4.
EXAMPLE 5
(51) FIG. 7 illustrates a fifth example of the present invention. Effects when installing a first guide member (16) will be described. FIG. 7(a) is a plan sectional view illustrating a left half of a tip part of an after-air port, when the first guide member (16) is not installed, and FIG. 7(b) is a detailed plan sectional view of the left half of the tip part of the after-air port around the first guide member (16), when the first guide member (16) is installed.
(52) As illustrated in FIG. 7(a), the secondary flow (circulation vortex 11a) between the primary after-air jet and the secondary after-air jet is formed by contacting with the tip part of the primary after-air nozzle (5) and a portion of the secondary after-air guide vanes (15) facing the furnace nearest to the primary after-air nozzle (5), and molten ash suspended in the secondary flow (circulation vortex (11a)) are adhered to the tip part of the primary after-air nozzle (5) and the portion of the secondary after-air guide vanes (15) facing the furnace nearest to the primary after-air nozzle (5).
(53) The ash adhered to the furnace side surface gradually grow to become a cause of inhibiting the stable formation of the primary after-air jet and the secondary after-air jets. As illustrated in FIG. 7(b), a small interval is provided between the tip part of the primary after-air nozzle (5) and the portion of the secondary after-air guide vanes (15) facing the furnace nearest to the primary after-air nozzle (5), and the first guide member (16) is installed in the interval, such that a small amount of sealing air (S) illustrated by arrows is normally supplied along the outer surface of the tip part of the primary after-air nozzle 5 and the portion of the secondary after-air guide vanes (15) facing the furnace (31) nearest to the primary after-air nozzle (5). Therefore, contact and adherence of the molten ash suspended in the secondary flow (circulation vortex (11a)) can be suppressed so as to form stable after-air jets.
(54) The effects of a second guide member (19) illustrated in the drawings other than FIG. 1 will not be described in detail, but due to the same effects as the above-described effects, a small amount of sealing air is normally supplied to the after-air port opening spreading part (18). Therefore, the adherence of the ash to the after-air port opening spreading part (18) can be suppressed so as to form stable secondary after-air jets.
EXAMPLE 6
(55) A sixth example of the present invention will be described using FIG. 8. FIG. 8(a) is a plan sectional view illustrating the left half of a tip part of an after-air port when an outlet contracting member (5b) is not provided in the primary after-air nozzle (5), and FIG. 8(b) is a plan sectional view illustrating the left half of the tip part of the after-air port when the outlet contracting member (5b) is provided therein.
(56) When the inclination angle with respect to the axis C.sub.1 parallel to the after-air port central axis C.sub.0 of secondary after-air guide vanes (15) is small, as illustrated in FIG. 8(a), a space between the jets of the primary after-air (1) and the secondary after-air (11) is decreased, and there is a case in which forming the secondary flow (circulation vortex (11a)) is difficult, or although the secondary flow (circulation vortex (11a)) is formed, stably forming the same is difficult. In such a case, separation of the secondary after-air (11) from the primary after-air (1) is difficult or unstable, such that a so-called penetration in the primary after-air (1) and spreadability in the secondary after-air (11) which are the basic configuration of the present invention are difficult to be achieved, or effects thereof are reduced.
(57) Therefore, by providing the outlet contracting member (5b) of the primary after-air nozzle (5) on the tip of the primary after-air nozzle (5), as illustrated in FIG. 8(b), even when the inclination angle of secondary after-air guide vanes (15) with respect to the axis C.sub.1 parallel to the after-air port central axis C.sub.0 is small, it is possible to form the space between the jets of the primary after-air (1) and the secondary after-air (11), and form the stable secondary flow (circulation vortex (11a)), such that a so-called penetration in the primary after-air (1) and spreadability in the secondary after-air (11) which are the basic configuration of the present invention can be normally achieved.
EXAMPLE 7
(58) A seventh example of the present invention will be described using FIG. 9. FIG. 9(a) is a front view of an after-air port as viewed from the furnace (31) side of the after-air port provided on the furnace wall, and FIG. 9(b) is a cross-sectional view taken in the arrow direction of line A-A in FIG. 9(a).
(59) In the after-air port illustrated in FIG. 9, the after-air is divided into a primary after-air (1) and a secondary after-air (11) from a wind box (30) for after-air, and the primary after-air (1) and the secondary after-air (11) are supplied to the furnace (31) via a primary after-air nozzle (5) and secondary after-air nozzles (14), respectively. The primary after-air nozzle (5) includes a primary after-air nozzle inlet contracting member (5a) which is installed in the inlet thereof and has a cross-section gradually decreased toward the flow direction, to suppress the pressure loss in the inlet of the primary after-air nozzle. The primary after-air nozzle (5) includes primary after-air flow rate control dampers (3) which are installed in an inlet part thereof and are capable of changing the flow path resistance, to optimally control the flow rate of the primary after-air (1).
(60) The primary after-air nozzle (5) includes a primary after-air rectifier (4) which is installed inside thereof and made of a plate material provided with a plurality of through holes. Even when deviation of velocity distribution exists in the primary after-air (1) at the inlet part of the primary after-air nozzle (5), it is rectified to a uniform flow by the primary after-air rectifier (4), and thus the primary after-air (1) is supplied to the furnace (31) as a jet having stable penetration.
(61) As illustrated in FIG. 9(a), the present example has a rectangular after-air port. By forming openings (17) and (18) in a rectangular shape, the primary after-air nozzle (5), the secondary after-air flow rate control dampers (12), the secondary after-air guide vanes (15), and the like may also be formed in rectangular shape. Therefore, it may be effective in terms of reduction in production costs, while achieving the function of the present invention.
EXAMPLE 8
(62) An eighth example of the present invention will be described using FIG. 10. FIG. 10(a) is a front view of an after-air port as viewed from the inside of the furnace thereof, which is provided in the furnace wall, and (FIG. 10(b)) is a cross-sectional view taken in an arrow direction of line A-A in FIG. 10(a).
(63) In the after-air port illustrated in FIG. 10, the after-air is divided into the primary after-air (1) and the secondary after-air (11) from a wind box (30) for after-air, and the primary after-air (1) and the secondary after-air (11) are supplied to the furnace (31) via a primary after-air nozzle (5) and secondary after-air nozzles (14), respectively. The primary after-air nozzle (5) includes a primary after-air nozzle inlet contracting member (5a) which is installed in the inlet thereof and has a cross-section gradually decreased toward the flow direction, to suppress the pressure loss in the inlet of the primary after-air nozzle. The primary after-air nozzle (5) includes primary after-air flow rate control dampers (3) which are installed in an inlet part thereof and are capable of changing the flow path resistance, to optimally control the flow rate of the primary after-air (1).
(64) The primary after-air nozzle (5) includes a primary after-air rectifier (4) which is installed inside thereof and made of a plate material provided with a plurality of through holes. Even when the deviation of velocity distribution exists in the primary after-air (1) at the inlet part of the primary after-air nozzle (5), it is rectified to a uniform flow by the primary after-air rectifier (4), and thus the primary after-air (1) is supplied to the furnace (31) as a jet having stable penetration.
(65) As illustrated in FIG. 10(a), in the present example, openings (17) and (18) of the after-air port are formed in a hexagonal shape. As seen above, by applying the hexagonal openings (throat parts) (17) and (18), the secondary after-air flow rate control dampers (12), the secondary after-air guide vanes (15), and the like may also be formed in simple hexagonal shape. Therefore, it may be effective in terms of production costs, while achieving the function of the present invention.
(66) The structure of the furnace wall in which the after-air ports are installed may be various, such as a panel of a water cooling tube group, a structure of a fireproof wall and metal, or the like, but it may be appropriately selected depending on the structure of the after-air port having the rectangular or hexagonal opening, also in consideration of the production costs.
(67) When the after-air ports described in the above respective examples are applied as after-air ports (7) (7a and 7b), depending on the flow rate distribution of the combustion gas containing the unburned components and rising from burners (6), it is possible to appropriately set the after-air flow rate distribution and jet direction of the primary after-air (1) and the secondary after-air (11), and stably maintain the penetration of the primary after-air (1) jet and the spreadability of the secondary after-air (11) jet, as well as, achieve high combustion performance by effectively reducing the unburned components.
(68) When the after-air ports (7) (7a and 7b) of the above respective examples are applied as the combustion device having a single stage (one stage) after-air ports (7) (7a and 7b), as described above, it is possible to achieve high combustion performance. However, in the combustion device having multiple stages of after-air ports (7) (7a and 7b), even when the after-air ports (7) (7a and 7b) formed by the present invention are applied as all stages of after-air ports (7) (7a and 7b) or as a part of stages of after-air ports (7) (7a and 7b), it is possible to achieve high combustion performance by effectively reducing the unburned components.
(69) In the combustion device having the single stage or multiple stages of after-air ports, the after-air ports formed by the present invention may be applied to the after-air ports (7a), and the conventional after-air ports of cited invention 3 may be applied to the sub after-air ports (7b).
(70) Further, even when the after-air ports (7) are applied to a single surface combustion type combustion device in which the burners are disposed only on one side of the furnace front and rear walls, or a tangential combustion type combustion device in which the burners are disposed in entire surfaces or corner portions of the furnace front and rear walls, it is possible to achieve high combustion performance by effectively reducing the unburned components by utilizing the penetration and spreadability of the primary and secondary after-air jets.
(71) In addition, FIGS. 4 and 6 define the function capable of controlling the direction of the secondary after-air jets, and flow rate of the primary after-air and the secondary after-air, but any one of manual and automatic control means may be used. When applying the automatic control means, it is possible to apply a control program that changes the settings based on an operation condition such as load, after-air total flow rate, and the like.
EXAMPLE 9
(72) FIG. 11 illustrates an after-air port according to a ninth example of the present invention. FIG. 11(a) is a front view as viewed from the furnace side, FIG. 11(b) is a cross-sectional view taken in the arrow direction of line A-A in FIG. 11(a), and FIG. 11(c) is a cross-sectional view taken in the arrow direction of line B-B in FIG. 11(a). In the present example, the primary after-air nozzle (5) is provided with primary after-air guide vanes (8) inside thereof. Multiple stages of the primary after-air guide vanes (8) are installed in a height direction of the after-air port along the flow of the after-air. Herein, rear ends of the primary after-air guide vanes (8) in the flow of the primary after-air (1) are at a fixed position, and front ends thereof in the flow of the primary after-air (1) are formed in a movable type. When the front ends of the primary after-air guide vanes (8) move downward from the horizontal direction, the primary after-air guide vanes (8) have an upwardly inclined angle, and it is possible to upwardly inject the primary after-air (1) into the furnace.
(73) FIGS. 12 and 13 illustrate a shape of jet of the after-air structure according to the present example. Furthermore, the results illustrated in FIGS. 12 and 13 are the results of numerical analysis of the same system as a jet analysis of the after-air structure shown in FIG. 16. In addition, the analysis of FIG. 12 was performed by a flow rate ratio of 6:4 of the primary after-air (1) to the secondary after-air (11). As similar to FIG. 16, these drawings illustrate contrasting densities (actually expressed by a difference in color) obtained by representing the air concentration of the after-air in a strip shape and showing it in a dimensionless way as an after-air mass distribution. AAP center, Upper level of AAP (1), Upper level of AAP (2) and Upper level of AAP (3) shown in FIGS. 12 and 13 illustrate a height from the AAP center, respectively, which are sequentially increased from (1) to (3).
(74) FIG. 12(a) shows the shape and the after-air concentration distribution of the jet due to a difference in the cross-sectional shape of the AAP opening in the plane of the vertical direction passing through the central axis C.sub.0 of the after-air port (AAP) (7) (see FIG. 2) by the contrasting densities (actually expressed by a difference in color), and FIG. 12(b) shows the shape and the after-air concentration distribution of the jet due to a difference in the cross-sectional shape of the AAP opening in the plane of the horizontal direction passing through the central axis C.sub.0 of the after-air port (AAP) (7) by the contrasting densities (actually expressed by a difference in color).
(75) (i) of FIGS. 12(a) and (b) illustrates a case of without the primary after-air guide vane (8), (ii) of FIGS. 12(a) and (b) illustrates a case that the inclination angle with respect to the horizontal of the primary after-air guide vanes (8) is 0, (iii) of FIGS. 12(a) and (b) illustrates a case that the inclination angle with respect to the horizontal of the primary after-air guide vanes (8) is upward 25 on the furnace outlet side (hereinafter, briefly referred to as upward), and (iv) of FIGS. 12(a) and (b) illustrates a case that the inclination angle with respect to the horizontal of the primary after-air guide vanes (8) is upward 45.
(76) In the result when the plane of the primary after-air guide vanes (8) faces the horizontal direction ((ii) of FIG. 12 (a)), the jet of the primary after-air (1) has a high penetration force, and collides with the primary after-air jet from the opposite wall at the central part of the furnace. This is effective for reducing the unburned components by facilitating the combustion, when using a flame retardant fuel with a low combustion rate, in order to facilitate the mixing in the central part of the furnace.
(77) In addition, it can be seen that the secondary after-air (11) spreads at the outlet of the AAP (7), and is separated from the primary after-air (1) to spread in the horizontal direction.
(78) In the result when the inclination angle of the primary after-air guide vanes (8) is set to be an upward angle of 25 ((iii) of FIG. 12 (b)), the primary after-air (1) is injected upward, rather than horizontal. However, since the primary after-air has a substantial penetration force without being affected by the combustion gas in the furnace, it is possible to confirm that it collides with the after-air from the opposite wall at the center of the furnace.
(79) From the above results, there is an effect to facilitate the mixing of the after-air (1) and (11), such that in the case of fuel with relatively excellent combustibility, the combustion is facilitated, and it is effective for reducing the unburned components. In addition, since the mixing of the after-air (1) and (11) shifts to the top of the furnace, and the mixing of the combustion gas rising in the furnace with the after-air (1) and (11) is delayed, there are advantages that the residence time of the combustion gas is increased, and NOx reduction is strengthened. It can be seen that the secondary after-air (11) is separated from the primary after-air (1), spreads in the horizontal direction, and spreads along the wall surface in which the AAP is installed. From this, it can be seen that it is effective for reducing the unburned components in the region illustrated by the one dot dash line C in FIG. 3(b).
(80) (iv) of FIGS. 12(a) and (b) illustrates the result when the inclination angle of the primary after-air guide vanes (8) is set to be an upward angle of 45. In these cases, the primary after-air has a substantial upward penetration force, but reaches the top of the furnace before reaching the central part of the furnace, and it was not observed that it collides with the after-air from the opposite wall. From this, it is preferable that the inclination angle of the primary after-air guide vanes (8) ranges from 0 to 25.
(81) FIG. 13 is a view illustrating the distribution of the jet when the flow rate ratio of the primary after-air (1) to the secondary after-air (11) is set to be 8:2, in the after-air structure of the present invention. FIG. 13(a) shows the shape and the after-air concentration distribution of the jet in the plane of the vertical direction passing through the central axis C.sub.0 of the after-air port (AAP), and FIG. 13(b) shows the shape and the after-air concentration distribution of the jet in the plane of the horizontal direction passing through the central axis C.sub.0 of the after-air port (AAP).
(82) FIGS. 13(a) and (b) illustrate the shape and the temperature distribution of the jet as the contrasting densities (actually expressed by a difference in color), wherein (i) shows a case of setting the inclination angle of the primary after-air guide vanes (8) to be 0, and (ii) shows a case of setting the inclination angle of the primary after-air guide vanes (8) to be 25, respectively.
(83) It can be seen from FIG. 13 that, by increasing the flow rate of the primary after-air (1), the jet of the primary after-air (1) has an increased penetration force, while the flow rate of the secondary after-air (11) is decreased, and spreads in the horizontal direction at the outlet of AAP (7). When the primary after-air guide vanes (8) are horizontally installed, the secondary after-air (11) spreads in the horizontal direction, and spreads along the wall surface in which the AAP (7) is installed. As a result, compared to FIG. 12(a) having a high flow rate of the secondary after-air (11), the diffusion in the vicinity of the wall surface is promoted, and reducing the unburned components is facilitated in the region of C in FIG. 15(b).
REFERENCE SIGNS LIST
(84) 1 primary after-air 3 primary after-air flow rate control damper 4 primary after-air rectifier 5 primary after-air nozzle 5a primary after-air nozzle inlet contracting member 5b primary after-air nozzle outlet contracting member 6 burner 7a after-air port 7b sub after-air port 8 primary after-air guide vane 11 secondary after-air 11a circulation vortex 12 secondary after-air flow rate control damper 13 secondary after-air rectifier 14 secondary after-air nozzle 15 secondary after-air guide vane 15a fixing member 16 first guide member 17 after-air port opening (throat part) 18 after-air port opening spreading part 19 second guide member 20 secondary after-air guide vane operation lever 21 secondary after-air guide vane operation lever through part seal 22 secondary after-air guide vane rotation shaft 23 secondary after-air guide vane link 24 secondary after-air guide vane link rotation shaft 25 air separation plate 30 wind box for after-air 31 furnace 32 wind box casing for after-air S sealing air
