The present invention relates to a spray nozzle to atomize liquid fuel, and a combustion device having the spray nozzle.
In a high-output and high-load combustion device such as a boiler for power generation, suspension firing for horizontal fuel combustion is adopted frequently. When liquid fuel such as fuel oil is used as fuel, the fuel is atomized with a spray nozzle, then floated in a furnace of the combustion device and is combusted. Further, when solid fuel, typified by coal is used as fuel, the solid fuel (coal) is ground into fine powdered coal having a particle diameter equal to or smaller than 0.1 mm. The fine powdered coal is conveyed with carrier gas such as air and is combusted in the furnace. Even in the case of the combustion device to combust the fine powdered coal, it is frequently accompanied by a combustion device using liquid fuel for activation or flame stabilization.
In the combustion of liquid fuel, when a spray particle diameter is large, combustion reaction is delayed, then the combustion efficiency is lowered, and ash dust and carbon monoxide may occur. Accordingly, upon liquid combustion, a method (pressure spraying) of pressurizing the fuel (spray fluid), generally to 0.5 to 5 MPa, and spraying it from a spray nozzle, to obtain fine particles having a particle diameter equal to or smaller than 300 μm, or a method (2 fluid spraying) of supplying air or vapor as spray medium for atomization to attain atomization is employed. In the pressure spraying, since the spray medium is not required and the device is downsized, it is frequently used in a small capacity combustion device such as the above-described combustion device for activation.
As the pressure spraying type spray nozzle, applying a vortex turning flow to the fuel so as to forma thinner liquid film from a spray hole by a centrifugal force (turning spray nozzle) is known. The liquid film is divided and atomized with a shearing force from peripheral gas. This method provides spray having liquid droplets with high kinetic momentum and high spray penetration.
With regard to the above-described method, a cross-slit spray nozzle, in which a nozzle main body is provided with crossed slit holes formed from both sides, to forma cross-shaped fluid duct and the intersecting part is used as a fuel spray hole, is known. Patent Document 1 to Patent Document 3 describe them. In this method, two flows toward the central intersecting part are formed in the upstream-side channel, and opposed flows are collided to form a thin fan-shaped liquid film from the intersecting part (spray hole). The liquid film is divided and atomized by shearing force from the peripheral gas. In this method, in comparison with the above-described turning spray nozzle, the kinetic momentum of liquid droplets is low and it is easy to keep the fine particles in the vicinity of the spray nozzle. Note that the present type nozzle is also described as a fan spray type spray nozzle from its fan-spray shape. Further, Patent Document 4 also shows a spray nozzle structure. The flow of fluid from a flow plate toward an orifice is issued from a gap therebetween, but the structure has no particular collision route.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. Hei 4-303172
[Patent Document 2] Japanese Unexamined Patent Application Publication No. Hei 6-299932
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 2000-345944
[Patent Document 4] Japanese Patent No. 2657101
The above-described patent documents related to the cross slit spray nozzle, having an object of application mainly to a fuel injection device of an internal combustion engine, provide a valve for intermittent spray on the upstream side of the spray nozzle main body, provide space (fluid duct extending part) on its downstream side, and further, arrange a cross-shaped channel (spray nozzle main body) in its downstream.
As the fluid duct extending part is provided in the upstream of the spray nozzle main body, the flow velocity of the spray fluid entering from the valve is reduced, and the fuel flow is distributed in the upper channel. The spray fluid flowing in the upper channel becomes opposed flows toward the intersecting part of the cross-shaped channel, to form a thin fan-shaped liquid film by collision. At this time, it is desirable that the opposed flows collide at a more obtuse angle for atomization.
However, in the above-described patent documents, a part of the spray fluid passes from the valve through the fluid duct extending part and a flow linearly toward the intersecting part occurs. This flow has low contribution to collision. Accordingly, it increases the thickness of the liquid film, and causes difficulty in atomization. Further, the kinetic momentum of the issued liquid droplets is increased. In the Patent Document 3, the kinetic momentum is reduced by arrangement of the fluid duct extending part and the shape of the intersecting part. In this case, the fluid linearly flows from the fluid duct extending part to the intersecting part. Accordingly, it increases the thickness of the liquid film and causes difficulty in atomization. Further, the kinetic momentum of the issued liquid droplets is high.
The first object of the present invention is to cause fluid, which is branched and opposed in the upper channel of the cross-shaped channel, to collide with each other at an obtuse angle, to promote atomization, further, to propose a spray nozzle to reduce the kinetic momentum in the axial direction of issued liquid droplets.
Further, the Patent Documents 1 to 3 show the method of forming plural cross-shaped channels to increase the number of intersecting parts. By increasing the number of spray holes having a small cross sectional area, it is possible to increase the spray amount with small diameter of spray particles. However, since the plural cross-shaped channels are formed in the same plane, sprays formed from the respective spray holes easily collide with each other and connected with each other, thus the particle diameter is increased. The second object of the present invention is to propose a spray nozzle to prevent interference between the sprays formed from the respective spray holes.
Further, in the fuel injection device of an internal combustion engine, the injection amount is comparatively small whereas the injection pressure is comparatively high, i.e., 5 to 12 MPa. Further, as intermittent spraying is performed, turbulence occurs in the fluid flowing in the fluid duct, to prevent sedimentation of solid materials in the fluid duct. However, in a combustion device such as a boiler, as the injection amount is large, reduction of injection pressure is required from the viewpoint of reduction of energy consumption. In this case, the sedimentation of solid materials in the fluid duct may cause occlusion or deterioration of atomization. Further, as fluid often flows by a constant flow amount, turbulence does not easily occur in the flow, and easily causes sedimentation of solid materials in a part of the flow at a low flow velocity or small turbulence. When the solid materials grow by chemical reaction or the like, the occlusion of the fluid duct may occur, to cause the deterioration of atomization performance of the spray nozzle and the occurrence of large diameter particle. The third object of the present invention is to propose a spray nozzle to prevent sedimentation of solid materials in the fluid duct in the combustion device such as a boiler in which fluid often flows by a constant fluid amount.
The present invention is a spray nozzle which pressurizes liquid fuel as spray fluid and supplies it from upstream to downstream of a fluid duct to spray it from an end, in which at least one channel is formed in respective both surfaces of a nozzle plate provided at the end of the spray nozzle, and an intersecting part of the two channels is used as a fuel spray hole. A guide member is in contact with the upstream-side channel provided in the both surfaces of the nozzle plate, the guide member is provided for spray fluid flowing through a fluid duct on the upstream side of the intersecting part, and the fluid is guided toward the fuel spray hole and collided from opposite directions.
Further, in the spray nozzle, the angle of the flow direction of the fluids guided toward the fuel spray hole and collided from the opposite directions with the guide member is an obtuse angle.
Further, in the spray nozzle, the nozzle plate has flat surfaces at different angles with respect to the spray nozzle axial direction, and plural fuel spray holes are formed by providing a plurality of at least one of the channels formed in the both surfaces of the nozzle plate and using combinations of the channels.
Further, in the spray nozzle, the axial direction of the plural fuel spray holes is inclined in a direction symmetric with respect to the flow direction of the spray fluid flowing through the fluid duct at the end of which the spray nozzle is provided, and issue is performed.
Further, in the spray nozzle, the fluid-duct cross-sectional area of the upstream-side channel of the channels is changed in the flow direction of the spray fluid flowing through the upstream-side channel.
Further, in the spray nozzle, the fluid-duct cross-sectional area of the upstream-side channel is decreased toward the fuel spray hole.
Further, in the spray nozzle, the upstream-side channels are mutually connected.
Further, in a combustion device, using liquid fuel as at least a part of fuel, and having a spray nozzle which pressurizes the liquid fuel and sprays it, comprising: a combustion furnace to combust fossil fuel; a fuel supply system to supply fuel and carrier gas to carry the fuel to the combustion furnace; a combustion gas supply system to supply combustion gas to the combustion furnace; a burner provided on a furnace wall of the combustion furnace and connected to the fuel supply system and the combustion gas supply system, to combust the fossil fuel; and a heat exchanger for heat exchange from combustion exhaust gas caused in the combustion furnace to the outside, the above-described spray nozzle is used as the spray nozzle.
The present invention is a spray nozzle to pressurize liquid fuel as spray fluid and supplies it from the upstream to the downstream of a fluid duct, and sprays it from its end. At least one channel is formed in both surfaces of a nozzle plate provided at the end of the spray nozzle, and an intersecting part of the two channels is used as a fuel spray hole. In the channels provided in the both surfaces of the nozzle plate, a guide member is provided for the spray fluid flowing through the upstream-side fluid duct of the intersecting part in contact with the upstream-side channel. It is possible to atomize the spray particle diameter by guiding the fluid from opposite directions toward the fuel spray hole to collide with each other. Accordingly, the combustion reaction is quickened, the combustion efficiency is improved, and the occurrence of ash dust and carbon monoxide is suppressed. Further, as the flow velocity of the spray particle is low and the spray particles easily stay in the vicinity of the spray nozzle, practically excellent advantages i.e. quickened ignition and improved flame stability are attained.
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Hereinbelow, working examples of the present invention will be described in the respective embodiments.
In the embodiment 1, the combustion air is branched to the pipes 5 and 6, and respectively issued from the burner 2 and the air supply port 7 into the furnace 1. By supplying air less than a necessary logical air amount for complete combustion of the fuel from the burner 2, a reducing region of air-short combustion is formed in the vicinity of the burner in the furnace 1, and combustion gas 9 flows upward in this reducing region. In this reducing region, a part of nitrogen content included in the fuel is generated as a reducing agent, and reaction to reduce NOx caused by combustion with the burner to nitrogen occurs. Accordingly, the NOx concentration at the exit of the furnace 1 is reduced in comparison with a case where all the combustion air is supplied from the burner 2. Note that the unburnt combustible content is reduced by supplying the remaining combustion air from the air supply port 7 and completely combusting the fuel. Combustion gas 10 mixed with the combustion air from the air supply port 7 passes through a flue 12 via a heat exchanger 11 above the furnace 1, and is discharged from a funnel 13 in the atmosphere.
In the spray nozzle of the embodiment 1 shown in
In the nozzle plate 22, upper and lower rectangular channels 28 and 29 are provided from both surfaces, the two channels intersect in a cross shape, and the communicating intersecting part forms a fuel spray hole 30. In the embodiment 1, it has a guide member 23, and this is in contact with the upstream-side channel 28 in the nozzle plate 22, and is provided in a position overlapped with the fuel spray hole 30 with respect to the spray direction of the spray nozzle.
By providing the guide member 23, the spray fluid (liquid fuel) is branched with the above-described guide member 23 from the fuel fluid duct 21 connected to the spray nozzle, passes through the above-described upstream-side channel 28, flows to the fuel spray hole 30 and is issued. At this time, the flow from the fuel fluid duct 21 linearly toward the fuel spray hole 30 is disturbed with the guide member 23. Accordingly, the spray fluid forms opposed two flows toward the fuel spray hole 30 in the upstream-side channel 28, and the flows collide at an obtuse angle of approximately 90° or greater between flow directions, and are sprayed from the fuel spray hole 30. The collision of the two flows form a thin fan-shaped liquid film 31. The liquid film is divided by a shearing force from peripheral gas, and is microminiaturized into spray particles 32. Further, as the spray fluids collide at an obtuse angle, the kinetic momentum in the axial direction of the liquid film 31 and the spray particles 32 is lowered, and the flow velocity of the spray particles 32 is reduced.
In the combustion device using the spray nozzle of the embodiment 1 of the present invention, as the spray particle diameter is small, the combustion reaction is quickened, the combustion efficiency is improved, and the occurrence of ash dust and carbon monoxide is prevented. Further, as the flow velocity of the spray particles is low and the spray particles easily stay in the vicinity of the spray nozzle 8, ignition is quickened and the flame stability is improved. Accordingly, when the combustion air is branched and sprayed from the burner 2 and the air supply port 7 in the furnace 1 as in the case of the combustion device shown in
Further, as in the application shown in
Note that in the combustion device shown in
Further, in the embodiment 1, as the combustion device, liquid fuel is used, however, it is applicable to a case where solid fuel such as fine powdered coal is used as main fuel and liquid fuel is used as secondary fuel. In this case, when the liquid fuel is sprayed from the spray nozzle 8 into the furnace 1, the above-described advantages are obtained.
For this purpose, the burner 2 is connected to a fuel pipe 41 connected to a solid fuel supply system (not shown) and a fuel pipe 42 connected to liquid fuel supply system (not shown). The burner 2 has a fuel nozzle 43 in its center, and an air nozzle 44, connected to the combustion air supply system 3, to supply combustion air into the furnace, on its outer periphery. Note that in the embodiment shown in
The liquid fuel spray nozzle is included in the burner 2. The combustion device shown in
The spray nozzle of the embodiment 2 shown in
As an application of the spray nozzle of the embodiment 2, in addition to a case where the downstream-side surface of the nozzle plate is formed with a flat surface having an angle in the opposite direction with respect to the axial direction of the spray nozzle, it may be arranged such that the downstream-side surface of the nozzle plate has a conical shape and the surface is provided with plural channels.
The spray nozzle for liquid spray fuel is included in the burner 2. In
The spray nozzle of the embodiment 3 of the present invention shown in
Accordingly, as the spray fluid flowing on the upstream side approaches the exit of the fuel spray hole, the flow velocity is increased. At this time, turbulence occurs in the fluid duct by the change of the flow velocity, to prevent sedimentation of solid materials in the fluid duct.
In a case were the solid materials are stacked in the fluid duct, when the solid materials grow by chemical reaction or the like, there is a probability of occlusion of the fluid duct. When a part of the fluid duct is occluded, the atomization performance of the spray nozzle is deteriorated and large diameter particles occur. The large diameter particles delay the combustion reaction. Accordingly, in the combustion device using the spray nozzle, there are probabilities of reduction of combustion efficiency and occurrence of ash dust and carbon monoxide. It is possible to operate the combustion device in a stable manner for a long time with the structure to prevent sedimentation of solid materials in a fluid duct as in the case of the present embodiment.
As in the case of the spray nozzle shown in
Number | Date | Country | Kind |
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2011-003614 | Jan 2011 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2012/050411 | 1/12/2012 | WO | 00 | 8/15/2013 |