JPH0550646B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Application of Industrial Articles) The present invention relates to a fuel spray nozzle device for a burner for burning fluid fuel, and in particular to COM fuel (Coal and Oil Mixture), which is oil fuel or a mixed fuel of oil and pulverized coal. ) and a spray nozzle device for a burner that atomizes, sprays, and burns fluid fuel such as CWM fuel (Coal and Water Mixture), which is a mixed fuel of water and pulverized coal.

(Prior Art) To burn liquid fuel or slurry fuel,
Conventionally, many methods have been used to atomize these fuels by atomizing them to increase the surface area that comes into contact with combustion air and then burn them in a furnace. In this case, in order to atomize the fuel, in addition to the energy that helps atomization, such as the pressure of the fuel itself, compressed air or steam is used as an atomizing medium, and the energy of these gases is used to fuel the atomization. A two-fluid atomization method is known as a means for efficient atomization.

FIG. 5 shows a side sectional view of a Y-jet type burner nozzle, which is one of the most popular and popular types. This nozzle is composed of an inner cylinder 1 and an outer cylinder 2 for supplying liquid, and a sprayer plate 5 for mixing the two fluids and atomizing them.
Inside the sprayer plate 5, there are provided a round atomizing medium inlet hole 6, a fuel inlet hole 7, which are machined by a drill, and a mixing hole 8 where the two join in a Y shape. An atomizing medium 4 such as air or steam passes through the normally cylindrical inner cylinder 1 , and a liquid or slurry fuel (COM or CWM) 3 passes through an annular passage 33 between the outer cylinder 2 and the inner cylinder 1 .

The number of holes varies depending on the capacity of the burner (the amount of fuel sprayed per unit time), but normally there are 3 to 10 nozzle holes 17 arranged concentrically with respect to the nozzle center axis XX.
It is arranged symmetrically or asymmetrically with respect to the axis with outward expansion.

(Problem to be solved by the invention) According to recent experiments by the present inventors (unpublished),
It has been found that the most important part for spraying is the shape of the hole between the part where the two fluids join in the mixing hole 8 and the outlet end of the outlet hole 17 where the fluid is spouted to the outside. Furthermore, there is a problem with the force relationship at the time of collision between the atomization medium and the fuel, and if the flow velocity or inertia of the fuel is greater than that of the atomization medium, the fuel will cross the flow of the atomization medium traveling straight and move along the opposing wall 8a of the mixing hole. If the fuel is ejected as a liquid film, or on the other hand, if the flow velocity of the spray medium and the resulting inertial force are greater than that of the fuel, as shown in Figure 5, the fuel will not be sufficiently mixed with the spray medium. , it bends at the point where the mixing holes meet and ejects as a liquid film along the wall 8b.
It was found that in both cases, overall, the fuel was not sufficiently atomized and coarse particles were produced. Coarse particle fuel is not completely burned in the furnace, causing an increase in unburned matter and soot in the combustion exhaust gas.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel spray nozzle device for a fluid fuel combustion burner that can uniformly mix fuel and spray medium and promote atomization of the fuel.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides two or more mixing holes in the spray nozzle for mixing the fuel and the spray medium, in which the fuel and the spray medium are mixed to form a jet stream. The mixed fluid is made to collide with each other in the mixing chamber provided at the downstream side of the mixing hole to promote atomization, and after uniformizing the atomization of the mixed fluid within the mixing chamber,
The present invention provides a nozzle device configured to inject into a combustion furnace through an injection hole provided at the nozzle outlet end to finish atomization.

That is, the present invention provides a fuel spray nozzle for a burner for burning fluid fuel, which has an intersection where a fuel passage for supplying fuel and a medium passage for supplying a medium for pulverizing the fuel into fine particles intersect, and at least two or more mixing holes are provided in the interior so that the fuel is pulverized by a medium, and the mixing holes are installed at positions such that the mixed fluid of fuel and medium that flows out of each hole collides with each other, An inner mixing chamber is provided at the collision position of the mixed fluid to ensure uniformity of fine fuel particles caused by collision, and multiple outlet jet holes are provided from the inner mixing chamber toward the nozzle tip to ensure uniformity in the inner mixing chamber. It is characterized in that it is configured to inject a mixed fluid of the converted fuel and medium to the outside.

(Embodiment) FIG. 1 is a sectional view of a fuel spray nozzle device showing one embodiment of the present invention. A sprayer head 18 and a sprayer plate 5 are attached to the tips of the double tubes on the concentric shaft 19 of the inner cylinder 1 and the outer cylinder 2.
The fluid fuel 3 passes through the inner cylinder fuel passage 32, and the annular passage 33 between the inner cylinder and the outer cylinder is filled with an atomizing medium (usually steam or air is used, but hereinafter the atomizing medium is simply referred to as a medium). ) passes. Next, the fuel and the medium pass through the fuel inlet hole 7 and the medium inlet hole 6 provided in the sprayer head 18, respectively, and collide and mix in the mixing chamber 8, which is made up of cylindrical holes. The fuel enters the internal mixing chamber 9, which is comprised of , and is injected into the combustion furnace from a tapered jet hole 17 with an enlarged tip provided in the sprayer plate 5. Outlet nozzle 1
The inlet portion of the hole 17 is not perpendicular to the tip inner surface 34 of the inner mixing chamber 9 but is inclined outwardly, so that the portion 11 located on the outside with respect to the nozzle axis 19 is at an acute angle. It forms the edge of.

FIG. 2 is a front view of the nozzle in FIG. 1 viewed from direction A, and six jet holes 17 are arranged radially with respect to the nozzle axis 19 and at six equal positions in the circumferential direction on the surface 35. ing.

Now, the atomization of fuel in two-fluid spraying is a matter of how efficiently the energy of the steam or air medium is used to crush and atomize fluid fuel or slurry fuel.In other words, how efficiently is the exchange of momentum? It depends on how well it is done.

In FIG. 1, the fuel 3 is first divided into a number of fuel inlet holes 7 at the inlet of the sprayer head 18, each of which is configured to have a divergence angle of about 45 degrees with respect to the nozzle central axis 19. At this time, in the case of slurry fuel consisting of solid particles and liquid, the solid particles tend to clog the holes 7, but instead of making the holes 7 take a steep angle close to a right angle, the angle of the holes 7 should not be made to be at a steep angle close to a right angle, but rather be made at a gentle angle of about 45 degrees as described above. Since the angle is set, solid particles in the slurry can be prevented from stagnation at the portion where the fuel branches from the flow path 32 to the hole 7, and the fuel can flow smoothly. Also,
Even when purging the fuel when starting or stopping the fuel burner, the fuel can be discharged without being retained.

Next, the medium 4 that has passed through the outer cylinder 2 is guided from a medium inlet hole 6 provided correspondingly to the fuel inlet hole 7 to a mixing hole 8, where it is connected to the fuel from the hole 7 at an angle δ. collide. The angle δ is preferably about 80 to 100 degrees, and particularly preferably about 90 degrees.
What is important here is that the medium hole 6 is constricted immediately before the collision, and that the collision angle δ is set to the above angle. The aperture just before rectifies and accelerates the medium,
This is to ensure that the fuel is evenly impacted with a large force to atomize the fuel, and the reason why the collision angle δ is set above is to effectively convert the kinetic energy of the medium and fuel into collision pulverization. be. Note that if the collision angle δ is 100 degrees or more, the collision energy will be larger, but in that case, the effect of interfering with the flow of both the medium and the fuel will be greater, and the pressure will increase unnecessarily or The other fluid becomes more susceptible to the influence of pressure, making flow control difficult. For this reason, δ is preferably about 80 to 100 degrees,
In particular, it is preferable that δ=about 90 degrees.

Next, the fuel dispersed in the mixing holes 8 further flows into the internal mixing chamber 9. At this time, each mixing hole 8
Preferably, the axis of the nozzle intersects a point B on the central axis 19 of the nozzle at an angle α.
As a result, the fuel that has not been sufficiently dispersed and atomized in each mixing hole 8 collides with each other again.
The particles are uniformly dispersed and atomized throughout. The collision angle α at this time is preferably 30 degrees or more in order to effectively utilize each velocity energy for crushing, and even when it is 180 degrees, the collision effect is large. However, for the same reason as the first collision part described above, it is preferable for operation to set the angle to about 90 degrees.

The third feature is that an internal mixing chamber 9 is provided, which ensures the residence time necessary for dispersion and atomization after collision, and makes it possible to homogenize the slurry mixture. It is possible to prevent coarse particles and fuel liquid film from remaining.

The final structural feature is that the outlet jet hole 17 provided in the sprayer plate 5 is shaped like a truncated cone with a widening tip, and the mounting angle β of the hole 17 is 90 degrees with respect to the nozzle center axis. over 180 degrees
The point is that it is less than 100%. Spreading angle γ of the jet hole 17
obtained a result that the liquid spreading angle during two-fluid spraying is usually about 20 degrees, so in order to prevent contact re-agglomeration of the mixed fluid particles on the inner wall surface of the hole 17, it is necessary to set the angle to be at least this angle or more. is preferred.

The ejection hole 17 is shaped like a truncated cone that widens toward the tip (therefore, the cut surface of the hole 17 on the plane that includes the central axis becomes a tapered shape that widens toward the tip), and the divergence angle β is set to the value described above. In particular, as shown in the figure, the tip inner wall surface 34 of the internal mixing chamber and the inlet of the outlet jet hole 17 have an acute wedge-shaped edge part 11 formed at the farthest point from the nozzle central axis 19, resulting in an angular jet. An obtuse angle portion 36 is formed on the opposite side of the hole 17 from the 11th portion, that is, at a portion close to the nozzle center axis.

The edge portion 11 has the effect of breaking the fuel particles into ultra-fine particles when ejected from the internal mixing chamber into the combustion path using high-speed energy due to the pressure drop of the medium to atmospheric pressure, while the obtuse portion It serves as a wall against which the fuel mixture 10 travels straight to exit into the outer furnace, where the fuel becomes finer particles. For this reason, one hole of the outlet jet hole needs to have a certain length, and the effect is more likely to be exhibited if the expansion angle γ of the hole is not too large. Further, the smaller the acute angle of the edge portion 11 is, the more effective it is in making the fuel particles fine, but it cannot be made extremely small in consideration of defects and wear. For this reason, it is practical to set the expansion angle γ of the hole 17 to about 25 to 60 degrees.

The expansion angle β of the axis of the nozzle 17 is determined by the positional relationship of the nozzle 50 in relation to the throat 12 and air register 13 that constitute the burner device, as shown in FIG. It is preferable to make the fuel as large as possible in order to promote mixing with the combustion air 14 entering the combustion air, but if the jet flow of fuel is not bent by the combustion air flow 4, the fuel is It is inconvenient that it gets stuck. Therefore, the divergence angle β of the jet hole 17 is determined by the relative relationship between the velocity vector of the air flow 14 in the nozzle axial direction and the velocity vector of the fuel jet flow from the spray plate 5 of the nozzle, and depends on the type of fuel. From the viewpoint of ignition and stable combustion, it is preferable to set β to 90 to 180 degrees, although this differs depending on conditions such as the injection capacity of the nozzle and the injection capacity of the nozzle.

The features described above in the description of the embodiments of the present invention are effective even if each is adopted independently, but if they are adopted in combination, finely atomized fuel can be obtained with a small amount of medium and medium pressure.

The fine atomized fuel particles obtained by carrying out the present invention improve the initial ignitability immediately after leaving the burner nozzle portion, and as a result, the atmospheric temperature immediately after the fuel is sprayed from the burner can be increased. Based on the inventors' experience in developing low NOx combustion burners, in order to achieve low NOx combustion, the fuel injected from the burner into the furnace is first subjected to primary combustion as a high-temperature reducing flame, and then the combustion air is It was found that it was necessary to perform a second complete combustion by adding
reference). Therefore, the present invention can be suitably applied to a low NOx combustion burner.

In the embodiment of the present invention shown in FIG. 1, the fuel 3 is supplied from the passage 32 in the inner cylinder through the fuel inlet hole 7 to the mixing hole 8, while the medium is supplied between the inner cylinder 1 and the outer cylinder 2. Although it is shown that the medium is supplied to the mixing hole 8 through the annular passage 33 and through the medium inlet hole 6, the present invention is not limited to this embodiment. Fuel is passed through the annular passage 33
There is no problem even if it is supplied from the source, and this is also included in the present invention.

FIG. 3 shows another embodiment of the present invention, which differs from the one in FIG. Do not intersect the central axis, Figures 2 and 3
As is clear from comparing the figures, the structure is eccentric by an angle θ with respect to the radiation axis YY emerging from the nozzle center axis. In this case, sprayer plate 5
Since the length of the outlet orifice 17 provided in the fuel cell is longer than that shown in FIG. 2, the fuel 10 coming out of the internal mixing chamber 9 reliably collides with the wall surface of the outlet orifice, improving atomization.

(Effects of the Invention) When the present invention is carried out, the fluid is sufficiently atomized, and as a result, (1) the amount of medium used can be reduced, and fine atomized particles can be achieved in which the formation of coarse particles in the atomized fuel is prevented.

(2) The fine atomized particles improve the stability of fuel ignition and combustion, reducing the amount of unburned matter and soot.

(3) Improved ignitability due to fine fuel particles
Combustion with reduced NOx becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a burner nozzle showing one embodiment of the present invention, FIG. 2 is a front view seen from direction A in FIG. 1, and FIG. 3 is a front view of a nozzle showing another embodiment.
FIG. 4 is an explanatory diagram of the entire burner configuration when the nozzle device according to the present invention is installed, and FIG. 5 is a side sectional view showing a conventional burner nozzle device. 1... Inner cylinder, 2... Outer cylinder, 5... Sprayer plate, 6... Medium inlet hole, 7... Fuel inlet hole, 8
... Mixing hole, 9 ... Inner mixing chamber, 17 ... Outlet jet hole, 18 ... Sprayer head, 19 ... Nozzle center axis.

Claims (1)

[Claims] 1. A fuel spray nozzle for a burner for burning fluid fuel, which has an intersection where a fuel passage for supplying fuel intersects with a medium passage for supplying a medium for pulverizing the fuel into fine particles, and a fuel spray nozzle for internally discharging fuel. At least two or more mixing holes are provided so that the mixture is crushed by a medium, and the mixing holes are located at positions where the mixed fluid of the fuel and the medium that flows out of each hole collides with each other, and the mixing holes are arranged so that the mixed fluid that flows out of each hole collides with each other. An internal mixing chamber is provided at the position to homogenize the fuel fine particles caused by collision, and multiple outlet jet holes are provided from the internal mixing chamber toward the nozzle tip to mix the fuel homogenized in the internal mixing chamber. A fuel spray nozzle device for a burner for burning fluid fuel, characterized in that it is configured to inject a mixed fluid of media to the outside.