Liquid fuel combustion burner

Abstract: Method and burner (1) in which a liquid fuel is sprayed together with a spray-inducing fluid from various injection holes (32) arranged at the burner tip (22). The liquid fuel is turned into a rotating stream in these injection holes while the spray-inducing fluid is not rotated. This reduces the frictional energy between the spray-inducing fluid and the liquid fuel and formation of NO x is under control.

Description: Background of the Invention (1) Field of the Invention The present invention relates to a liquid fuel combustion burner used for a heating apparatus as a heat source of a boiler, a heating furnace and the like. More particularly, the present invention relates to a liquid fuel combustion burner having a structure in which a liquid fuel is sprayed together with fluid flow of air, steam or misty water drop (hereinafter referred to as "atomization-promoting fluid") mixed in the liquid fuel. (2) Description of the Related Art A liquid fuel combustion burner having a structure in which a liquid fuel is mixed with an atomization-promoting fluid such as steam or air and this mixed fluid is sprayed from a plurality of injection holes is known. For example, US Patent No. 4356970 discloses a liquid fuel atomizing nozzle which defines, on its interior, a pressurized fuel compartment and a pressurized steam chamber. A core stream of steam is flowed from the steam chamber and the liquid fuel is brought tangentially into contact with the stream of steam so as to form a combined stream. Thereafter, a secondary annular stream of steam is used to envelope the combined stream. According to the fuel spraying method adopted for this liquid fuel combustion burner, by the expansion energy generated when an atomization-promoting fluid such as steam or air is injected to a low-pressure side from a high-pressure side, the liquid fuel to be mixed with the spraying medium is atomized and diffused. As the above-mentioned spraying method, there are known an internal mixing method in which the injection quantity is controlled while maintaining a certain difference between the pressure of the spraying medium and the pressure of the liquid fuel, and an intermediate mixing method in which the pressure of the liquid fuel is changed while maintaining the pressure of the spraying medium at a certain level, whereby the injection quantity is controlled. The intermediate mixing method is advantageous over the internal mixing method in that the consumption of the spraying medium is small and a good atomizing effect is attained. However, this spraying method is defective int hat since the liquid fuel, which is an incompressible fluid, has no substantial dispersing force, the spraying medium should be maintained at a high temperature and a high pressure. As the means for solving this problem, there has been proposed a technique of giving a turning movement to the spraying medium and liquid fuel, promoting the atomization and diffusion of the liquid fuel by a centrifugal force generated by this turning movement and improving the combustion state (see Japanese Unexamined Utility Model Publication No. 57-145116). According to this conventional technique, not only by the expansion energy generated when steam is injected to a low-pressure side from a high-pressure side, but also by the centrifugal force generated by the turning movement, the mixing of the liquid fuel with air and the atomization of the fluid are promoted, and the liquid fuel is uniformly diffused over a broad range. Recently, exhaust gas regulations for combustion apparatuses become severe, and reduction of a level of nitrogen oxides (hereinafter referred to as "NO X ") is therefore an important problem. We made various experiments on the above-mentioned conventional liquid fuel combustion burner, and it was found that since the flame layer becomes thick and large and the heat dissipation is degraded, the flame temperature rises, the residence time in a high-temperature zone becomes long and it is difficult to reduce the level of NO X . The reason is that in the conventional liquid fuel combustion burner, since a plurality of injection holes are arranged equidistantly or substantially equidistantly, the flame layer becomes thick and large and the heat dissipation is degraded. Moreover, since both of the liquid fuel and the spraying medium such as steam are simultaneously turned, the frictional energy between steam and the liquid fuel is increased. Accordingly, the consumption of the spraying medium such as steam increases, and if the consumption of the spraying medium thus increases, it becomes necessary to elevate the heating temperature of the liquid fuel, with the result that a problem of increase of NO X in the exhaust gas arises. Summary of the Invention The present invention has been completed under this background to solve the foregoing problems of the conventional techniques. Namely, the present invention relates to a liquid fuel combustion burner, in which a liquid fuel is sprayed together with an atomization-promoting fluid mixed in the liquid fuel, and the object of the present invention is to promote the atomization and diffusion of the liquid fuel and reduce the level of NO X in exhaust gas while reducing the consumption of the spraying medium. More specifically, in accordance with the present invention, there is provided a liquid fuel combustion burner, in which liquid fuel is turned in a flow passage having a sectional area restricted for constringing a flow of the liquid fuel, and atomization-promoting fluid is introduced into said flow passage and a mixed fluid of the liquid fuel and the atomization-promoting fluid is sprayed from said flow passage. Accordingly, by the expansion energy generated when the spraying medium is injected to a low-pressure side from a high-pressure side, the liquid fuel to be mixed with the spraying medium is atomized and uniformly diffused. Furthermore, a turning movement is given to the liquid fuel, and by a centrifugal force generated by this turning movement, the atomization and diffusion of the liquid fuel are further promoted and the liquid fuel is uniformly diffused over a broad range. Especially, since only the liquid fuel is turned but the spraying medium is not turned, the frictional energy between the spraying medium and the liquid fuel is reduced, and hence, the consumption of the spraying medium can be reduced. Since the consumption of the spraying medium is reduced the heating temperature for the liquid fuel need not be elevated and hence, generation of NO X can be reduced. According to the present invention there is provided a liquid fuel combustion burner for use in a combustion apparatus, which burner is adapted to spray a mixture of the liquid fuel and the atomising promoting fluid into the combustion apparatus, and is attached to the end of a tube projecting into the combustion apparatus, said tube having formed therein a liquid fuel supply and an atomising promoting fluid supply, said burner comprising: a burner element, said burner element defining: at least one liquid fuel supply passage; a plurality of injection holes; at least one atomising promoting fluid passage, and characterised in that: said burner element further defines: a branch passage branched from the liquid fuel supply passage; an annular passage communicating with the downstream end of the branch passage and located around the downstream end of the atomising promoting fluid passage, a first connecting passage connecting the downstream end of the atomising promoting fluid passage to the injection holes; and a second connecting passage connecting the downstream end of the liquid fuel supply passage to the annular passage and the injection holes, wherein the injection holes are divided into groups of two, these groups being arranged circumferentially around the central axis of the burner element, the injection holes in each group being spaced closely to each other in a circumferential direction. In the burner having the above-mentioned structure, the liquid fuel flows into both of the liquid fuel supply passage and the branch passage. The liquid fuel which has flowed into the liquid fuel supply passage arrives at the connecting passage through the downstream end of the liquid fuel supply passage and is injected into the interior of the injection hole from the side position of the injection hole to which the connecting passage opens. The liquid fuel which has flowed into the branch passage arrives at the connecting passage through the annular passage and is injected into the interior of the injection hole from the side position of the injection hole to which the connecting passage opens. The spraying medium flows into the spraying medium supply passage. The spraying medium which has flowed into the spraying fluid supply passage arrives at the connecting passage and is injected into the interior of the injection hole from the downstream end of the injection hole to which the connecting passage opens. Since the direction of the connection of the connecting passage to the side portion of the injection hole is made in agreement with the tangential direction of the injection hole, the liquid fuel injected from the side portion of the injection hole is formed into a turning stream. A plurality of injection holes can be divided into a plurality of groups, each group consisting of two injection holes, and respective groups can be arranged at a plurality of positions separately from one another by predetermined angles in the circumferential direction with the central axis of the burner proper being as the center. Two injection holes of each group can be arranged so that they are brought close to each other in the circumferential direction with the central axis of the burner proper being as the center. If this embodiment is adopted, the flame can be divided into a plurality of independent small flames, and flames can be formed in the discrete state. Therefore, the heat dissipation is enhanced, and the flame temperature can be reduced, and since the flame layer becomes thin, the residence time of the gas in a high-temperature zone can be shortened, with the result that formation of NO X can be controlled. It is especially preferred that the injection holes of each group be arranged contiguously to each other so that the central axes of the injection holes form a crossing angle smaller than 20° or they are parallel to one another. Therefore, NO X can be effectively controlled. According to the preferred embodiment, the burner element comprises a fuel supply member and a burner tip connected to the top end of the fuel supply member, a liquid fuel supply passage, an atomization-promoting fluid supply passage, a branch passage and a connecting passage connecting the spraying medium supply passage to injection holes are formed in the fuel supply member, and a plurality of injection holes, an annular passage and a connecting passage connecting the downstream end of the liquid fuel supply passage to the annular passage and injection holes are formed in the burner tip. If this embodiment is adopted, the productivity of the burner element can be improved, and mass production and reduction of the cost become possible. Preferably, the fuel supply member is formed of a substantially columnar member having a surface of a circular cone on the top end. According to this embodiment, the productivity and reduction of price become possible. Furthermore, in the fuel supply member, a liquid fuel supply passage is preferably formed through top end and rear end portions thereof. According to this embodiment, the productivity and reduction of price become possible. Moreover, it is preferred that a plurality of branch passages be formed in the fuel supply member so that the branch passages extend obliquely upward from the rear end of the liquid fuel supply passage and open to the top end face of the fuel supply member. According to this embodiment, the productivity and reduction of price become possible. Still further, it is preferred that in the fuel supply member, a plurality of small-diameter holes extending obliquely from positions close to the rear end of the liquid fuel supply passage on the rear end face of the fuel supply member and being pierced to the top end face of the fuel supply member from the direction orthogonal to said to end face be formed According to this embodiment, the productivity and reduction of price become possible. Still in addition, it is preferred that an engaging pin be driven into the peripheral part of the top end face of the fuel supply member and the engaging pin be engaged with an engaging hole formed on the rear face of the burner tip to engage the fuel supply member with the burner tip. According to this embodiment, the productivity and reduction of price become possible. It is preferred that a recess capable of being engaged with the top end portion of the fuel supply member be formed on the rear face of the burner tip and the burner tip be formed to have substantially a shape of a circular cone as a whole. According to this embodiment, the productivity and reduction of price become possible. Moreover, it is preferred that a circular recess be formed at a central part of the inner face of the burner tip, an annular passage be formed in the peripheral portion of said inner face, and a plurality of injection holes pierced from the top end face of the burner tip in a direction orthogonal to said top end face and opening to the interior of the engaging portion be formed between said annular passage and said circular recess. According to this embodiment, the productivity and reduction of price become possible. Furthermore, it is preferred that between an injection hole-opening portion on the inner face of the burner tip and a circular recess formed at a central part of the inner face of the burner tip, a connecting passage connecting the injection hole and the circular recess be formed, and a connecting passage connecting the injection hole to the annular passage be formed between the opening of the injection hole and the annular passage. According to this embodiment, the productivity and reduction of price become possible. Still further, it is preferred that between an injection hole-opening portion on the top end face of the fuel supply member and a circular recess formed at a central part of the top end face of the fuel supply member, a connecting passage connecting the injection hole to the circular recess be formed, and a connecting passage connecting the injection hole to the annular passage be formed between the opening of the injection hole and the annular passage. The burner element can comprise a fuel supply member and a burner tip to be engaged with the top end portion of the fuel supply member, in which a liquid fuel supply passage, an atomization-promoting fluid supply passage, a branch passage, a connecting passage connecting the spraying medium supply passage and an injection hole, a part of a plurality of injection holes, an annular passage and a connecting passage connecting the downstream end of the liquid fuel supply passage to the annular passage and injection holes are formed in the fuel supply member, and the remainder of a plurality of injection holes are formed in the burner tip. According to this embodiment, the productivity of the burner element is increased, and mass production and reduction of the price become possible. Especially, since it is sufficient if connecting passages are formed on the top face of the fuel supply member by machining, there can be attained an advantage in that the machining operation can be performed simply and easily. It is preferred that a circular recess be formed at a central part of the top end face of the fuel supply member, an annular passage be formed in the peripheral portion of the inner face of the fuel supply member, and a connecting portion of a plurality of injection holes pierced from the top end face of the burner tip in a direction orthogonal to said top end face be formed between the annular passage and the circular recess. According to this embodiment, the productivity and reduction of price become possible. Furthermore, it is preferred that a connecting passage be formed between the injection hole-connecting portion of the fuel supply member and the circular recess formed at the central part of the fuel supply member to connect the injection opening-connecting portion to the circular recess, and a connecting passage be formed between the injection hole-connecting portion and the annular passage to connect the injection hole-connecting portion to the annular passage. According to this embodiment, the productivity and reduction of price become possible. The present invention will now be described in detail with reference to embodiments illustrating in the accompanying drawings, from which the present invention will be clearly understood. However, the scope of the present invention is not limited by these embodiments, but modifications can be freely made within the scope defined by the claims. Brief Description of the Drawings Fig. 1 is a sectional view illustrating the state of attachment of the liquid fuel combustion burner according to the present invention. Fig. 2 is a plan view showing a fuel supply member of the burner element shown in Fig. 1. Fig. 3 is a sectional view of a burner tip of the burner element shown in Fig. 1, which shows the section taken along the line III-III in Fig. 4. Fig. 4 is a bottom view of a burner tip of the burner element shown in Fig. 1. Fig. 5 is a plan view of a burner tip of the burner element shown in 1, which illustrates an example of the arrangement of injection holes. Fig. 6 is a sectional view illustrating another embodiment of the liquid fuel combustion burner according to the present invention. Fig. 7 is a plan view of a fuel supply member of the burner shown in Fig. 6. Fig. 8 is a sectional view illustrating still another embodiment of the liquid fuel combustion burner according to the present invention. Fig. 9 is a plan view of a fuel supply member of the burner shown in Fig. 8. Fig. 10 is a plan view illustrating the arrangement of injection holes in the conventional burner. Detailed Description of the Preferred Embodiments Fig. 1 is a sectional view illustrating the attachment of the liquid fuel combustion burner according to the present invention. A liquid fuel combustion burner 1 is inserted through the peripheral wall of a furnace as a combustion apparatus not shown in the drawings and is used in the state where the top end side of the burner 1 is fixed to the top end portion of a guide pipe 2 projected into the interior of the furnace. An adapter 3 is inserted and fixed in the guide pipe 2, and in the adapter 2, there are formed passages 4 and 5 connected to a fuel supply pipe and an atomization-promoting fluid supply pipe, which are extended from a fuel supply source and an atomization-promoting fluid supply source, not shown in the drawings. A cylindrical cap 6 is engaged with a burner element 20 of the burner 1 in the state where the top end face of the burner element 20 is projected, and by fitting male screw 6a formed on the peripheral face of the cap 6 to a female screw 2a formed on the inner circumferential face of the guide pipe 2, the burner element 20 is fixed to the top end portion of the guide pipe 2. In this attachment state of the burner element 20, the passages 4 and 5 communicating with the fuel supply pipe and the spraying medium supply pipe are connected to a fuel supply hole 23 and an atomization-promoting fluid supply hole 26, described hereinafter, of the burner element 20. The burner element 20 comprises a fuel supply member 21 and a burner tip 22 connected to the top face of the fuel supply member 21. The fuel supply member 21 is formed of a substantially columnar body having a top end face of a circular cone. The liquid fuel supply hole 23 is formed to pierce a central part of the fuel supply member 21 along the central axis thereof. In the fuel supply member 21, a plurality of branch holes 25 are formed so that the branch holes 25 extend obliquely upward from a large-diameter portion formed at the rear end of the liquid fuel supply hole 23 and open to the top end face of the liquid fuel supply hole 23 and open to the top end face of the fuel supply member 21. A plurality of spraying medium supply holes 26 are formed in the fuel supply member 21 so that the spraying medium supply holes 26 extend obliquely from the position close to the large-diameter portion of the liquid fuel supply hole 23 while approaching the liquid fuel supply hole 23, and the holes 26 communicate with a plurality of small-diameter holes 27 pierced in the top end face of the fuel supply member 21 from a direction orthogonal to said top end face, respectively. In the embodiment, as shown in the plan view of the fuel supply member in Fig. 2, the small-diameter holes 27 are arranged between the liquid fuel supply hole 23 and the branch holes 25 on the top end face of the fuel supply member 21. An engaging pin 8 is driven in the peripheral portion of the top end face of the fuel supply member 21, and by engaging this engaging pin 8 with an engaging hole 36 formed on the rear face of the burner tip 22, the fuel supply member 21 and the burner tip 22 are fixed together. As shown in the sectional view of the burner tip in Fig. 3 and the bottom view of the burner tip in Fig. 4, a fitting portion 29 capable of engaging with the top end portion of the above-mentioned fuel supply member is formed as a recess on the rear face of the burner tip 22, and the burner tip 22 is formed to have substantially a shape of a circular cone as a whole. A circular recess 30 is formed at a central part of the inner face of the fitting portion 29 of the burner tip 22 and an annular groove 31 is formed on the periphery of the inner face of the fitting portion 29. A plurality of injection holes 32 pierced from the top end face of the burner tip 22 in a direction orthogonal to said to end face and opened to the inner face of the fitting portion 29 are formed between the annular groove 31 of the fitting portion 29 and the circular recess 30. A communicating groove 33 connecting the injection holes 32 to the circular recess 30 is formed between the openings of the injection holes 32 on the inner face of the fitting portion 29 and the circular recess 30. Furthermore, a communicating groove 35 connecting the injection holes 32 to the annular groove 31 is formed between the openings of the injection holes 32 on the inner face of the fitting portion 29 and the annular groove 31. One side walls a and b of the communicating grooves 33 and 35 are located substantially on a line passing through the centers of the injection holes 32. The other side walls c and d of the communicating grooves 33 and 35 are parallel to said one side walls a and b and are located on a line along the tangential direction of the injection holes 32. In the above-mentioned structure, the connecting directions of the communicating grooves 33 and 35 to the side portions of the injection holes 32 are made in agreement with the tangential direction of the injection holes 32. Referring to the plan view of the burner tip in Fig. 5, the arrangement of the injection holes 32, which is one of the characteristic features of the present invention, will now be described in detail. Namely, six injection holes 32a through 32f are arranged and these injection holes 32a through 32f are divided into three groups, that is, a group of injection holes 32a and 32b, a group of injection holes 32c and 32d and a group of injection holes 32e and 32f. These groups are arranged at three positions spaced by 120° from one another with the central axis of the burner tip 22 being as the center. In each group, the injection holes 32a and 32b, 32c and 32d or 32e and 32f are arranged adjacently to one another so that the central axes of these injection holes cross each other at a predetermined angle α (smaller than 20°). Incidentally, in each group, the injection holes 32a and 32b, 32c and 32d or 32e and 32f can be arranged adjacently to each other so that the central axes of these injection holes are parallel to one another. The function of the liquid fuel combustion burner having the above-mentioned structure will now be described. A liquid fuel supplied to the fuel supply member 21 flows into the liquid fuel supply hole 23 and the branch hole 25 from the rear end of the fuel supply member 21. The liquid fuel which has flowed into the liquid fuel supply hole arrives at the communicating groove 33 through the circular recess 30 of the burner tip 32 and is injected into the interior of the injection hole 32 from the position on the inner circumferential face of the injection hole 32 to which the communicating groove 33 opens. The liquid fuel which has flowed into the branch hole 25 arrives at the communicating groove 35 though the annular groove 31 of the burner tip 32 and is injected into the interior of the injection hole 32 from the position of the inner circumferential face confronting to the position of the opening of the communicating groove 33 of the injection hole 32, to which the communicating groove 35 opens. Steam as the spraying medium flows into the spraying medium supply hole 26 from the rear end portion of the fuel supply member 21. Steam which has flowed into the spraying medium supply hole 26 arrives at the small-diameter hole 27 and is injected into the interior of the injection hole 32 from the position on the rear end face of the injection hole 32 to which the small-diameter hole 27 opens. Since one side walls a and b of the communicating grooves 33 and 35 are formed to pass substantially through the center of the injection hole 32 and the other side walls c and d are formed so that they are parallel to said one side walls a and b and located in the tangential direction of the injection hole 32, the liquid fuel is injected from two confronting positions on the inner circumferential face of the injection hole 32, and each injected liquid fluid is formed into a turning stream. Steam is injected to these turning streams of the liquid fluid and the liquid fuel is mixed with steam, and the mixture is sprayed from the injection hole 32. At this point, by the expansion energy generated when the steam is injected to a low-pressure side from a high-pressure side, the liquid fuel mixed with steam is atomized and uniformly diffused. Furthermore, a turning movement is given to the liquid fuel, and by the centrifugal force generated by this turning movement, atomization and diffusion of the liquid fuel are further promoted and the liquid fuel is uniformly diffused over a broad range. Especially, since only the liquid fuel is turned but steam is not turned, the frictional energy between steam and the liquid fuel is reduced, the consumption of steam can be reduced, and by this reduction of the consumption of steam, it is made unnecessary to elevate the temperature for heating the liquid fuel and therefore, formation of NO x can be controlled. Moreover, since the injection holes 32a through 32f are divided into three groups, the injection holes of respective groups are arranged at three positions separated from one another by 120° and in each group, the injection holes 32a and 32b, the injection holes 32c and 32d or the injection holes 32e and 32f are arranged adjacently to each other so that the central axes of the injection holes cross each other at a predetermined angle α(smaller than 20°) or they are parallel to each other, the flame can be divided into a plurality of small independent flames in the discrete state, and therefore, a good heat dissipation can be attained and the flame temperature can be lowered. Moreover, the flame layer becomes thin and the residence time of gas in a high-temperature zone can be shortened, and therefore, formation of NO x can be effectively controlled. The effects of the above-mentioned liquid fuel combustion burner of the present invention will be readily understood from the experimental results shown in Tables 1 through 4. It is obvious that the NO x concentration and the soot quantity can be drastically reduced. Conventional Burner Invention Burner of Present capacity of boiler 3 t/h 3 t/h spraying method internal mixing intermediate mixing number of burners 1 1 size of injection holes ⊘1.7 × 8 holes (Fig. 10-a) ⊘2.6 × 6 holes (parallel) fuel oil kerosene kerosene combustion oil quantity 280 l/h 280 l/h spraying oil pressure 2.7 kg/cm² 4.7 kg/cm² spraying steam pressure 2.1 kg.cm² 4.6 kg/cm² NO x concentration 80 ppm 40 ppm exhaust gas O₂ level 2.9 % 3.0 % smoke concentration 0.5 - 1.0 0 Conventional Burner Invention Burner of Present capacity of boiler 85 t/h 85 t/h spraying method internal mixing intermediate mixing number of burners 4 4 size of injection holes ⊘3.5 × 8 holes (Fig. 10-b) ⊘4.7 × 6 holes (parallel) fuel oil fuel oil C fuel oil C combustion oil quantity 6000 l/h 6000 l/h spraying oil pressure 7.4 kg/cm² 8.0 kg/cm² spraying steam pressure 9.0 kg.cm² 9.4 kg/cm² NO x concentration 223 ppm 173 ppm exhaust gas O₂ level 3.9 % 4.1 % smoke concentration 5.0 3.5 Conventional Burner Invention Burner of Present capacity of boiler 50 t/h 50 t/h spraying method internal mixing intermediate mixing number of burners 3 3 size of injection holes ⊘3.9 × 4 holes (Fig. 10-c) ⊘4.2 × 6 holes (α= 7.5°) fuel oil fuel oil C fuel oil C combustion oil quantity 3774 l/h 3786 l/h spraying oil pressure 10.5 kg/cm² 10.6 kg/cm² spraying steam pressure 10.7 kg.cm² 10.7 kg/cm² NO x concentration 202 ppm 182 ppm exhaust gas O₂ level 1.1 % 1.0 % smoke concentration 0 0 soot quantity 40 - 80 kg/day 20 - 30 kg/day Conventional Burner Invention Burner of Present capacity of boiler 120 t/h 120 t/h spraying method internal mixing intermediate mixing number of burners 6 6 size of injection holes ⊘4.9 × 5 holes (Fig. 10-d) ⊘6.2 × 6 holes (α= 15°) fuel oil fuel oil C fuel oil C combustion oil quantity 8800 l/h 8800 l/h spraying oil pressure 8.2 kg/cm² 8.4 kg/cm² spraying steam pressure 5.4 kg.cm² 5.6 kg/cm² NO x concentration 230 ppm 180 ppm exhaust gas O₂ level 1.8 % 1.2 % smoke concentration 0 - 0.5 0 - 0.5 If the crossing angle between the central axes of the injection holes is larger than 20° (for example, 25°), as shown in Table 5, the NO x concentration and the soot quantity are larger than those attained when this angle is smaller than 20°. Accordingly, it is obvious that particular effects are attained in the present invention by arranging the injection holes adjacently to each other so that the central axes of the injection holes cross each other at an angle smaller than 20° or they are parallel to each other. Burner of Present Invention capacity of boiler 120 t/h spraying method intermediate mixing number of burners 6 size of injection holes ⊘6.2 × 6 holes (α= 25°) fuel oil fuel oil C combustion oil quantity 8800 l/h spraying oil pressure 8.4 kg/cm² spraying steam pressure 5.6 kg.cm² NO x concentration 210 ppm exhaust gas O₂ level 1.5 % smoke concentration 0 - 0.5 Incidentally, in Tables 1 through 4, the conventional burners are those in which the injection holes are arranged as shown in Fig.s 10-a through 10-d. Another embodiment of the present invention will now be described with reference to Figs. 6 and 7. In the present embodiment, in the fuel supply member 21, the liquid fuel supply hole 23 and spraying medium supply hole 26 are arranged in a positional relation reverse to that shown in Figs. 1 through 4. Namely, the spraying medium supply hole 26 is formed at the central part of the rear end face of the fuel supply member 21, and a plurality of small-diameter holes 27 connecting the spraying medium supply hole 26 to the injection hole 32 are formed. A plurality of liquid fuel supply holes 23 are formed in the periphery of the spraying medium supply hole 26, and a first branch hole 37 and a second branch hole 39 branched from the liquid fuel supply hole 23 in two different directions are formed. The first branch hole 37 communicates with the circular recess 30 of the burner tip 22, and the second branch hole 29 communicates with the annular groove 31 of the burner tip 22. The function of the present embodiment will now be described. The liquid fuel supplied to the fuel supply member 21 follows into the liquid fuel supply hole 23 from the rear end portion of the fuel supply member 21. The liquid fluid which has flowed into the liquid fuel supply hole 23 is introduced into the first branch hole 37 and the second branch hole 39. The liquid fuel which has flowed into the first branch hole 37 arrives at the communicating groove 33 through the circular recess 30 and is injected into the interior of the injection hole 32 from the position on the inner circumferential face of the injection hole 32, to which the communicating groove 33 opens. The liquid fuel which has flowed into the second branch hole 39 arrives at the communicating groove 35 through the annular groove 31 and is injected into the interior of the injection hole 32 from the position of the inner circumferential face confronting to the position of the opening of the communicating groove 33 of the injection hole 32, to which the communicating groove 35 opens. Steam flows into the spraying medium supply hole 26 from the rear end portion of the fuel supply member 21 and is injected into the interior of the injection hole 32 from the position on the rear end face of the injection hole 32 to which the small-diameter hole 27 opens, through the small-diameter hole 27. Also in the present embodiment, the liquid fuel injected from the two confronting positions on the inner circumferential face of the injection hole 32 is formed into turning streams, while steam is not turned. Still another example of the present invention will now be described with reference to Figs. 8 and 9. In the present embodiment, the communicating grooves 33 and 35, which are formed on the side of the burner tip 22 in the embodiment shown in Figs. 1 through 4, are formed on the side of the fuel supply member 21. Accordingly, in the present embodiment, it is sufficient if the communicating grooves 33 and 35 are formed on the top face of the fuel supply member 41 by machining. Therefore, the present embodiment is advantageous in that the machining operation can be performed simply and easily.

Claims: A liquid fuel combustion burner (1) for use in a combustion apparatus, which burner is adapted to spray a mixture of the liquid fuel and the atomising promoting fluid into the combustion apparatus and is attached to the end of a tube projecting into the combustion apparatus, said tube having formed therein a liquid fuel supply (4) and an atomising promoting fluid supply (5), said burner comprising: a burner element (21, 22), said burner element defining: at least one liquid fuel supply passage (23); a plurality of injection holes (32); at least one atomising promoting fluid passage (26), and characterised in that: said burner element further defines: a branch passage (25) branched from the liquid fuel supply passage (23); an annular passage (31) communicating with the downstream end of the branch passage (25) and located around the downstream end of the atomising promoting fluid passage (26), a first connecting passage (27) connecting the downstream end of the atomising promoting fluid passage (26) to the injection holes; and a second connecting passage (33, 35) connecting the downstream end of the liquid fuel supply passage (23) to the annular passage (31) and the injection holes (32), wherein the injection holes (32) are divided into groups of two, these groups being arranged circumferentially around the central axis of the burner element, the injection holes (32) in each group being spaced closely to each other in a circumferential direction. A liquid fuel combustion burner (1) as set forth in claim 1, wherein the injection holes (32) of each group are arranged continuously to each other so that the central axes of the injection holes form a crossing angle smaller than 20° or they are parallel to one another. A liquid fuel combustion burner (1) as set forth in claim 1, wherein the burner element (21, 22) comprises a fuel supply member (21) and a burner tip (22) connected to the top end of the fuel supply member (21), said fuel supply member (21) having formed therein: the liquid fuel supply passage (23); the atomising promoting fluid passage (26); the branch passage (25); and the first connecting passage (27), said burner tip (22) having formed therein: the annular passage (31); the second connecting passage (33, 35); and the injection holes (32). A liquid fuel combustion burner (1) as set forth in claim 3, wherein the fuel supply member (21) is formed of a substantially columnar member having a surface of a circular cone on the top end. A liquid fuel combustion burner (1) as set forth in claim 3, wherein in the fuel supply member (21), the liquid fuel supply passage (28) is formed through top end and rear end portions thereof. A liquid fuel combustion burner (1) as set forth in claim 3, wherein a plurality of branch passages (25) are formed in the fuel supply member (21) so that the branch passages extend obliquely upward from the rear end of the liquid fuel supply passage (23) and open to the top end face of the fuel supply member (21). A liquid fuel combustion burner (1) as set forth in claim 3, wherein in the fuel supply member (21), a plurality of small-diameter holes (27) extending obliquely from positions close to the rear end of the liquid fuel supply passage (23) on the rear end face of the fuel supply member (21) and being pierced to the top end face of the fuel supply member (21) from the direction orthogonal to said end face are formed. A liquid fuel combustion burner (1) as set forth in claim 3, wherein an engaging pin (28) is driven into the peripheral part of the top end face of the fuel supply member (21) and the engaging pin (28) is engaged with an engaging hole (36) formed on the rear face of the burner tip (22) to engage the fuel supply member (21) with the burner tip (22). A liquid fuel combustion burner (1) as set forth in claim 3, wherein a recess capable of being engaged with the top end portion of the fuel supply member (21) is formed on the rear face of the burner tip (22) and the burner tip (22) is formed to have substantially a shape of a circular cone as a whole. A liquid fuel combustion burner (1) as set forth in claim 3, wherein a circular recess (30) is formed at a central part of the inner face of the burner tip (22) the annular passage (31) is formed in the peripheral portion of said inner face, and a plurality of injection holes (32) pierced from the top end face of the burner tip (22) in a direction orthogonal to said top end face and opening to the interior of the engaging portion are formed between said annular passage (31) and said circular recess (30). A liquid fuel combustion burner (1) as set forth in claim 3, wherein between an injection hole-opening portion on the inner face of the burner tip (22) and a circular recess (30) formed at a central part of the inner face of the burner tip, said second connecting passage (33, 35) is formed, said second connecting passage comprising: a connecting passage (33) connecting the injection hole (32) and the circular recess (30) and a connecting passage (35) connecting the opening of the injection hole to the annular passage (31). A liquid fuel combustion burner (1) as set forth in claim 3, wherein between an injection hole-opening portion on the top end face of the fuel supply member (21) and a circular recess (30) formed at a central part of the top end face of the fuel supply member, said second connecting passage (33, 35) is formed, said second connecting passage comprising: a connecting passage (33) connecting the injection hole (32) to the circular recess (30), and a connecting passage (35) connecting the opening of the injection hole (32) to the annular passage (31). A liquid fuel combustion burner (1) as set forth in claim 1, wherein the burner element (21, 22) comprises a fuel supply member (21) and a burner tip (22) to be engaged with the top end portion of the fuel supply member (21), the fuel supply member (21) having formed therein the liquid fuel supply passage (23), the atomising promoting fluid passage (26), the branch passage (25), the first connecting passage (27), the annular passage (31), the second connecting passage (33, 35), and a part of each of the injection holes, and wherein the burner tip (22) has formed therein the remainder of each of the injection holes. A fuel liquid combustion burner (1) as set forth in claim 13, wherein a circular recess (30) is formed at a central part of the top end face of the fuel supply member (22), an annular passage (31) is formed in the peripheral portion of the inner face of the fuel supply member (21), and a connecting portion of a plurality of injection holes pierced from the top end face of the burner tip (22) in a direction orthogonal to said top end face is formed between the annular passage and the circular recess. A liquid fuel combustion burner as set forth in claim 13, wherein a connecting passage (33) is formed between the injection hole-connecting portion of the fuel supply member and the circular recess (30) formed at the central part of the fuel supply member (21) and a connecting passage (35) is formed between the injection hole-connecting portion and the annular passage (31).

Inventors: MIYAKE TUNEO, MIYAKE, TUNEO, Miyake, Tuneo c/o E.P.S. Engineering Co., Ltd.
Applicants: E P S ENGINEERING CO LTD, FUJI DENKI CO LTD, NIPPON OIL CO LTD, E.P.S. ENGINEERING CO., LTD., FUJI DENKI CO., LTD., NIPPON OIL CO. LTD.
Application year: 1990
Main classification: F23D11
IPC codes: F23C99, F23D11