阅读说明：本技术 文丘里喷嘴以及具备该文丘里喷嘴的燃料供给装置 (Venturi nozzle and fuel supply device provided with same ) 是由 芝诚 渡边茂广 藤原达也 于 2016-10-27 设计创作，主要内容包括：本发明提供一种文丘里喷嘴以及具备该文丘里喷嘴的燃料供给装置。文丘里喷嘴配置于送风机(20)的上游侧,通过该送风机(20)的吸入压混合燃烧用空气与燃料气体,所述文丘里喷嘴(1)具备：形成为朝向下游侧直径变小的形状,导入燃烧用空气的喷嘴部(12)；配置于所述喷嘴部(12)的下游侧,形成为朝向下游侧直径变大的形状,将燃烧用空气与燃料气体混合的混合部(13)；以及配置于所述喷嘴部(12)与所述混合部(13)之间,导入燃料气体的燃料气体导入口(15),在所述喷嘴部(12)的内表面形成有多个槽部或凸条部(16),所述槽部或凸条部以圆周方向延伸且以燃烧用空气的流动方向隔着规定的间隔配置。(The invention provides a venturi nozzle and a fuel supply device provided with the same. The venturi nozzle is disposed on the upstream side of a blower (20), and mixes air for combustion with fuel gas by the suction pressure of the blower (20), and the venturi nozzle (1) is provided with: a nozzle part (12) which is formed into a shape with a diameter decreasing towards the downstream side and introduces air for combustion; a mixing section (13) disposed on the downstream side of the nozzle section (12), having a shape in which the diameter thereof increases toward the downstream side, and mixing combustion air with fuel gas; and a fuel gas inlet (15) disposed between the nozzle section (12) and the mixing section (13) and configured to introduce a fuel gas, wherein a plurality of grooves or ridges (16) extending in the circumferential direction and arranged with a predetermined interval in the flow direction of the combustion air are formed on the inner surface of the nozzle section (12).)

1. A venturi nozzle is disposed upstream of a blower and mixes combustion air and fuel gas by suction pressure of the blower,

the venturi nozzle is provided with:

a nozzle portion formed in a shape with a diameter decreasing toward a downstream side and introducing combustion air;

a mixing section disposed downstream of the nozzle section, having a shape in which a diameter thereof increases toward the downstream side, and mixing combustion air with fuel gas; and

a fuel gas inlet port disposed between the nozzle portion and the mixing portion for introducing a fuel gas,

a plurality of grooves extending in a circumferential direction and arranged at predetermined intervals in a flow direction of combustion air are formed on an inner surface of the nozzle portion,

among the surfaces constituting the groove, a surface (16a) located on the central axis side of the nozzle portion extends perpendicularly to the central axis or in a direction away from the central axis as it goes toward the upstream side,

among the surfaces constituting the groove, a surface (16b) located on the outer surface side of the nozzle portion extends in parallel with the central axis or in a direction closer to the central axis as it goes to the upstream side.

2. The venturi nozzle of claim 1,

the inner surface of the nozzle is formed of a curved surface that is curved so as to protrude inward.

3. The venturi nozzle of claim 1 or 2,

the height (h) of the groove portions is 0.5mm to 5mm, and the ratio (l/h) of the distance (1) between adjacent groove portions to the height (h) of the groove portions is 1 to 5.

4. The venturi nozzle of claim 1 or 2,

the ratio of the flow rate coefficient at a Reynolds number of 1.0E +5 to the flow rate coefficient at a Reynolds number of 2.5E +5 is 0.97 to 1.00.

5. The venturi nozzle of claim 1 or 2,

the ratio of the flow rate coefficient at a Reynolds number of 5.0E +4 to the flow rate coefficient at a Reynolds number of 2.5E +5 is 0.94 to 1.00.

6. A fuel supply device is provided with:

the venturi nozzle of any one of claims 1-5;

a blower disposed on a downstream side of the venturi nozzle; and

and a control unit for controlling the output of the blower.

7. The fuel supply apparatus according to claim 6,

the air blower is capable of varying the output,

the fuel supply device can change the combustion amount.

Technical Field

The present invention relates to a venturi nozzle and a fuel supply device provided with the venturi nozzle. This application claims priority based on japanese patent application No. 2016-.

Background

As a fuel supply device for a combustion apparatus such as a steam boiler that generates steam by heating water by mixing and combusting fuel gas and combustion air, there has been known a premix burner of a fan intake mixing type in which combustion air and fuel gas are mixed on an upstream side of a blower that feeds the combustion air to the combustion apparatus (see, for example, patent document 1).

Prior art documents

Patent document

Patent document 1: japanese Kohyo publication No. 2001-526372

The fan suction mixing type premix burner includes a blower and a venturi nozzle disposed upstream of the blower. The venturi nozzle includes a nozzle portion formed in a shape having a diameter that decreases toward the downstream side and into which the combustion air is introduced, a mixing portion disposed on the downstream side of the nozzle portion and mixing the combustion air and the fuel gas, and a fuel gas introduction port disposed between the nozzle portion and the mixing portion and into which the fuel gas is introduced.

According to the above venturi nozzle, the air blower is driven to suck the combustion air into the nozzle portion, and the fuel gas is introduced into the mixing portion from the fuel gas inlet by the venturi effect of the combustion air introduced into the nozzle portion.

In this way, since the premix burner is configured to include the venturi nozzle, the fuel gas and the combustion air can be efficiently mixed by the venturi effect, and the fuel gas and the combustion air can be mixed well without increasing the supply pressure of the fuel gas to the fuel supply device.

However, in the case of the fan-suction mixing type premix burner, when the combustion amount is changed by changing the output of the blower, it is difficult to keep the mixing ratio (air ratio) between the fuel gas and the combustion air constant. That is, when the output of the blower is small (that is, the flow rate of the combustion air is small) as compared with the case where the output of the blower is large (that is, the flow rate of the combustion air is large), the influence of the boundary layer separation occurring on the surface of the venturi nozzle becomes large, and the flow rate coefficient of the combustion air introduced into the venturi nozzle decreases. In the venturi nozzle, since the air ratio is also kept constant by keeping the relationship between the supply pressure of the combustion air (atmospheric pressure) and the supply pressure of the fuel gas constant, the air ratio cannot be kept constant if the flow rate coefficient changes. Therefore, in the conventional fuel supply device, an air pressure adjusting mechanism for adjusting the supply pressure of the fuel gas is required in accordance with a change in the flow rate coefficient accompanying a change in the combustion amount (i.e., a change in the supply amount of the combustion air).

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to provide a venturi nozzle and a fuel supply device including the venturi nozzle, which have a simpler configuration and can maintain a constant flow coefficient even when the flow rate of combustion air varies.

Means for solving the problems

The present invention relates to a venturi nozzle which is disposed upstream of a blower and mixes combustion air and fuel gas by suction pressure of the blower, the venturi nozzle including: a nozzle portion formed in a shape with a diameter decreasing toward a downstream side and introducing combustion air; a mixing section disposed downstream of the nozzle section, having a shape in which a diameter thereof increases toward the downstream side, and mixing combustion air with fuel gas; and a fuel gas inlet port disposed between the nozzle portion and the mixing portion and configured to introduce the fuel gas, wherein a plurality of grooves or ridges are formed on an inner surface of the nozzle portion, the grooves or ridges extending in a circumferential direction and being disposed at predetermined intervals in a flow direction of the combustion air.

Preferably, the inner surface of the nozzle portion is formed of a curved surface curved so as to protrude inward.

The height (h) of the groove or the ridge is 0.5mm to 5mm, and the ratio (1/h) of the distance (1) between adjacent grooves or ridges to the height (h) of the groove or ridge is preferably 1 to 5.

In addition, it is preferable that the surfaces forming the raised strip portions extend in a direction away from the central axis, parallel to, perpendicular to, or toward the upstream side with respect to a surface on the central axis side of the nozzle portion, and the surfaces forming the raised strip portions extend in a direction closer to the central axis, parallel to, perpendicular to, or toward the upstream side with respect to a surface on the outer surface side of the nozzle portion.

Further, the ratio of the flow rate coefficient at a Reynolds number of 1.0E +5 to the flow rate coefficient at a Reynolds number of 2.5E +5 is preferably 0.97 to 1.00.

Further, the ratio of the flow rate coefficient at a Reynolds number of 5.0E +4 to the flow rate coefficient at a Reynolds number of 2.5E +5 is preferably 0.94 to 1.00.

Further, the present invention relates to a fuel supply device including: the venturi nozzle described above; a blower disposed on a downstream side of the venturi nozzle; and a control unit for controlling the output of the blower.

Effects of the invention

According to the present invention, it is possible to provide a venturi nozzle and a fuel supply device including the venturi nozzle, which have a simpler configuration and can maintain a constant flow coefficient even when the flow rate of combustion air varies.

Drawings

Fig. 1 is a diagram schematically showing the configuration of a fuel supply device according to the present invention.

Fig. 2 is a perspective view showing a nozzle portion of a venturi nozzle according to an embodiment of the present invention.

Fig. 3 is an X-X sectional view of fig. 2.

Fig. 4 is an enlarged view of a portion of fig. 3.

FIG. 5 is a sectional view showing a nozzle portion of a venturi nozzle in comparative example 1, and corresponds to FIG. 3.

FIG. 6 is a sectional view showing a nozzle portion of a venturi nozzle of comparative example 2, and corresponds to FIG. 3.

FIG. 7 is a graph showing the results of examples and comparative examples.

Fig. 8 is a sectional view showing a nozzle portion of a venturi nozzle according to modification 1 of the present invention, and corresponds to fig. 4.

Fig. 9 is a cross-sectional view showing a nozzle portion of a venturi nozzle according to a modification 2 of the present invention, and corresponds to fig. 4.

Fig. 10 is a view schematically showing a ridge portion of a venturi nozzle according to a 3 rd modification of the present invention.

Description of the reference numerals

1 Venturi nozzle

12 nozzle part

13 mixing section

15 fuel gas inlet

16 convex strip part

20 blower

30 control part

100 fuel supply device.

Detailed Description

Hereinafter, preferred embodiments of the venturi nozzle and the fuel supply device according to the present invention will be described with reference to the drawings.

The fuel supply device 100 of the present embodiment is a fan-suction mixing type premix burner that mixes combustion air and fuel gas on the upstream side of a blower, and supplies the fuel gas and the combustion air gas to a combustion device (not shown) such as a steam boiler. The fuel supply device 100 includes a blower 20, a control unit 30, a venturi nozzle 1, a fuel gas supply line 40, a1 st mixed gas supply line 50, and a2 nd mixed gas supply line 60.

The blower 20 includes a blower main body 21 having a fan and a motor for rotating the fan, and an inverter 22 for increasing or decreasing the number of rotations of the fan (motor). The blower 20 is rotated by a predetermined number of rotations of the fan in accordance with the frequency of the inverter 22 to be input, thereby sucking combustion air and fuel gas at a predetermined output and sending them to the combustion apparatus.

The control unit 30 changes the output of the blower 20 according to the combustion state of the combustion device (for example, the combustion position of the steam boiler) to control the flow rate of the combustion air supplied to the combustion device. Specifically, the output of the blower 20 when the combustion device is burning at a high combustion position is set to be higher than the output of the blower 20 when the combustion device is burning at a low combustion position.

The venturi nozzle 1 is disposed upstream of the blower 20. The venturi nozzle 1 includes a housing 11, a nozzle portion 12, a mixing portion 13, a fuel gas passage 14, and a fuel gas inlet 15.

The housing 11 is formed in a tubular shape with one end and the other end opened by a metal member such as aluminum or stainless steel, for example. The housing 11 forms the outer shape of the venturi nozzle 11.

The nozzle 12 is disposed inside the casing 11. More specifically, the nozzle 12 is formed in a shape with a reduced diameter toward the downstream side, and the upstream end of the nozzle 12 is joined to the upstream end of the casing 11 over the entire circumference.

The nozzle portion 12 functions as a combustion air introduction portion for introducing combustion air.

In the present embodiment, as shown in fig. 2 and 3, the nozzle portion 12 is formed in a truncated cone shape having a curved surface curved so that a sectional shape in the axial direction is convex inward. More specifically, the inner surface of the nozzle 12 has, in a cross section in the radial direction, a straight portion 121 disposed on the downstream end side, and a quarter-circle curved portion 122 curved so as to be convex inward at a predetermined radius R.

As shown in fig. 2 and 3, the inner surface of the nozzle portion 12 is formed with a plurality of ridges 16, and the plurality of ridges 16 extend in the circumferential direction and are arranged at predetermined intervals in the flow direction of the combustion air. The ridge portion 16 will be described later in detail.

The mixing section 13 is disposed downstream of the nozzle section 12 in the casing 11, and has a shape with a diameter that increases toward the downstream side. The diameter of the upstream end of the mixing section 13 is slightly larger than the diameter of the downstream end of the nozzle section 12. The upstream end of the mixing section 13 is disposed at a position overlapping the downstream end of the nozzle section 12. The downstream end of the mixing section 13 is joined to the downstream end of the casing 11 over the entire circumference. In the present embodiment, as shown in fig. 2 and 3, the mixing portion 13 is formed in a truncated cone shape.

The mixing portion 13 mixes the combustion air introduced from the nozzle portion 12 with a fuel gas introduced from a fuel gas introduction port 15, which will be described later.

The fuel gas flow path 14 is formed by a space surrounded by the inner surface of the casing 11, the outer surface of the nozzle portion 12, and the outer surface of the mixing portion 13. The fuel gas is supplied to the fuel gas flow field 14 from a fuel gas supply line 40 described later.

The fuel gas inlet 15 is disposed between the nozzle 12 and the mixing portion 13. Specifically, the fuel gas inlet 15 is formed by a gap formed between the downstream end of the nozzle 12 and the upstream end of the mixing section 13.

The fuel gas supply line 40 supplies fuel gas to the venturi nozzle 1. The upstream side of the fuel gas supply line 40 is connected to a fuel gas supply source (not shown). The downstream side of the fuel gas supply line 40 is connected to the housing 11.

The fuel gas supply line 40 is provided with a pressure equalizing valve 41 and a hole 42. The pressure equalizing valve 41 and the hole 42 reduce the pressure of the fuel gas flowing through the fuel gas supply line 40 to a predetermined pressure and supply the pressure to the venturi nozzle 1.

The 1 st mixed gas supply line 50 connects the venturi nozzle 1 and the blower 20. The 1 st mixed gas supply line 50 allows the fuel gas and the combustion air mixed in the mixing portion 13 to flow to the blower 20 side.

The 2 nd mixed gas supply line 60 connects the blower 20 and a combustion device (not shown). The 2 nd mixed gas supply line 60 circulates the mixed gas fed to the blower 20 to the combustion apparatus side.

According to the fuel supply device 100 described above, when the blower 20 is driven at a predetermined output by the control unit 30, the combustion air is introduced into the nozzle portion 12 whose diameter decreases toward the downstream side, and then introduced into the mixing portion 13 whose diameter increases toward the downstream side. The fuel gas is supplied from the fuel gas supply line 40 to the fuel gas flow field 14 at a predetermined pressure. Accordingly, the fuel gas supplied to the fuel gas channel 14 is introduced into the mixing section 13 from the fuel gas inlet 15 by the venturi effect of the combustion air introduced into the nozzle section 12 and further introduced into the mixing section 13. Thus, the venturi nozzle 1 can efficiently mix the combustion air and the fuel gas without increasing the supply pressure of the fuel gas by utilizing the venturi effect.

The gas of the combustion air and the fuel gas mixed in the mixing portion 13 is supplied to the combustion device through the 1 st mixed gas supply line 50, the blower 20, and the 2 nd mixed gas supply line 60, and is combusted in the combustion device.

Here, in the venturi nozzle 1, the following relational expression is preferably established.

[ number 1 ]

Flow rate of fuel gas:

air volume:

Pg2＝Pa2

in addition to the above equation, the proportional relationship between Qg and Qa is maintained in venturi mixing by holding Pg1 at Pa1(Patm (atmospheric pressure)) by the pressure equalizing valve 41. This makes it possible to realize a constant air ratio without including a mechanical or electrical fuel gas pressure adjusting mechanism for keeping a required air ratio (a mixing ratio of combustion air and fuel gas) constant in other mixing systems.

However, in the case of the fan suction mixing type premix burner including the conventional venturi nozzle, when the output of the blower is changed to change the combustion amount, it is difficult to keep the mixing ratio (air ratio) between the fuel gas and the combustion air constant. In other words, it is considered that the influence of boundary layer separation occurring on the surface of the venturi nozzle becomes large in the case where the output of the blower is small (i.e., the flow rate of the combustion air is small) as compared with the case where the output of the blower is large (i.e., the flow rate of the combustion air is large), and thus the flow coefficient of the combustion air introduced into the venturi nozzle becomes small. In the venturi nozzle, the air ratio is kept constant by keeping the supply pressure Pa1 (atmospheric pressure) of the combustion air and the supply pressure Pg1 of the fuel gas in a constant relationship, and the air ratio cannot be kept constant by changing the flow rate coefficient.

Here, the flow rate coefficient C is expressed by the following equation. A decrease in the flow coefficient indicates an increase in flow loss.

Number 2

Here, v represents a flow velocity, p represents a pressure, and ρ represents a density. Further, a reference numeral 2 denotes a value at the narrowest part of the nozzle (corresponding to a position Pa2 in fig. 1), and a reference numeral 1 denotes a nozzle inlet (corresponding to a position Pa1 in fig. 1).

In the present embodiment, the venturi nozzle 1 is configured by forming a plurality of ridges 16 on the inner surface of the nozzle portion 12. Thus, turbulence can be generated on the surface of the nozzle portion 12 by the plurality of ridges 16 formed in the nozzle portion 12, and the occurrence of boundary layer separation can be suppressed. Accordingly, when the flow rate of the combustion air is small or large, the variation in the pressure of the combustion air introduced into the venturi nozzle 1 can be suppressed, and therefore, even when the flow rate of the combustion air varies, the flow rate coefficient C can be stabilized, and the air ratio can be kept constant.

In the present embodiment, as shown in fig. 3 and 4, the raised strip portion 16 is formed in an annular shape so as to extend over the entire circumference in the circumferential direction on the inner surface of the nozzle portion 12. The raised strip portions 16 formed in a ring shape are disposed at predetermined intervals in the flow direction of the combustion air in the curved surface portion 122 of the nozzle portion 12.

More specifically, in the present embodiment, the raised strip 16 is formed so as to protrude inward from the inner surface of the curved surface portion 122 of the nozzle 12. The height (h) of the plurality of ridges 16 gradually increases from the upstream side toward the downstream side. The top portions of the plurality of ridges 16 protrude at an angle of substantially 90 degrees, and the plurality of ridges 16 are formed in a step shape.

Among the surfaces constituting the raised strip portion 16, a surface (surface 16a in fig. 4) located on the side of the central axis X of the nozzle portion 12 extends in a direction away from the central axis X in parallel with, perpendicular to, or toward the upstream side of the central axis X. In the present embodiment, a surface 16a of the surfaces constituting the raised strip portions 16, which surface is located on the side of the central axis X of the nozzle portion 12, extends parallel to the central axis X.

Among the surfaces constituting the raised portions 16, the surface (surface 16b in fig. 4) located on the outer surface side of the nozzle portion 12 extends in a direction parallel to, perpendicular to, or closer to the central axis X toward the upstream side. In the present embodiment, among the surfaces constituting the raised strip 16, the surface 16b located on the outer surface side of the nozzle 12 extends in a direction perpendicular to the central axis X.

Thus, the raised portions 16 can be formed appropriately when the nozzle 12 is used for molding.

The height (h) of the ridges 16 formed in the nozzle 12 is preferably 0.5mm to 5mm from the viewpoint of effectively suppressing a decrease in the flow coefficient C at a low flow rate while reducing the pressure loss. If the height (h) of the raised strips 16 is too high, the pressure loss due to the arrangement of the raised strips 16 becomes too large. If the height (h) of the raised strips 16 is too low, then turbulent flow cannot be generated sufficiently by the raised strips 16, and the occurrence of boundary layer separation cannot be sufficiently suppressed.

In addition, the ratio (l/h) of the distance (l) between the adjacent ridges 16 to the height (h) of the ridges 16 is preferably 1 to 5 from the same viewpoint. When the ratio (l/h) of the distance (l) between the ridges 16 to the height (h) of the ridges 16 is excessively large (i.e., the distance (l) between the ridges 16 adjacent to each other is excessively long), the effect of suppressing the occurrence of boundary layer separation by the plurality of ridges 16 is reduced.

In the present embodiment, the height (h) of the raised portion 16 is a distance from the top of the raised portion 16 to the perpendicular direction with respect to the curved surface portion 122 of the nozzle 12. The distance (1) between the adjacent ridges 16 is a linear distance between the tops of the adjacent ridges 16.

When the venturi nozzle 1 of the present embodiment is applied to a combustion apparatus in which the output of the blower is largely changed (for example, a steam boiler in which the turn down ratio is large), the ratio (C2/C1) of the flow coefficient C2 when the reynolds number is 1.0E +5 to the flow coefficient C1 when the reynolds number is 2.5E +5 is preferably 0.97 to 1.00, from the viewpoint of suppressing the fluctuation of the air ratio between the high flow rate and the low flow rate. From the same viewpoint, the ratio (C3/C1) of the flow rate C3 at a Reynolds number of 5.0E +4 to the flow rate C1 at a Reynolds number of 2.5E +5 is preferably 0.94 to 1.00, more preferably 0.97 to 1.00.