JPH06280791A - Axial-flow blade for vortex generator - Google Patents

Abstract

PURPOSE: To provide a vortex generator capable of generating a vortex flow to improve a combustion flame stability, by setting inside and outside diameters of the vortex generator and respective radii of curvature of lower and upper boundaries of a vane to have a specific rational relation releting to respective points in lower and upper circumstances. CONSTITUTION: A burner is composed of a fireproofing wall 1, a vortex generator 2, a fuel gun 3 and the like. In this case, an inside diameter r1 and an outside diameter r2 of the generator 2, and radii of curvature R1 , R2 of lower and upper boundaries of a vane are set to have a rational relation of R1 :R2 =r1 :r2 relating to respective points u, ϕ of the lower boundary and respective points u', ϕ' of the upper boundary. Deviation angles of the respective points are made θk respectively, and polar coordinates of the respective points in development of the vane are expressed by the expression. Provided is by this manner a vortex generator having low pressure lowering and low turbulent flow intensity, capable of controlling partially concentrated fuel combustion and a residence time of combustion gas, and capable of generating a vortex flow to improve combustion flame stability.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates generally to vortex generators, and more particularly to vortex generators having specially designed axial flow vanes.

[0002]

Burners are one of the most important parts of combustion equipment.
Is one. Burner performance not only greatly affects combustion efficiency, but is also closely related to combustion flame stability, effective fuel utilization, and pollutant emissions. Improper combustion methods and proper burner selection not only affect the effective use of energy, but also produce air pollutants due to the release of large amounts of harmful substances such as NOx due to improper combustion.

In order to reduce the amount of NOx produced in the combustion process and improve the performance of the burner so as to increase the stability of the combustion flame, the peak temperature of the flame is decreased, the residence time of the combustion gas is controlled, and It is necessary to create a rich fuel burn.

[0004]

The great effect of vortices on the flow device has been known and recognized for many years. When one effect is desired, the designer strives to generate a predetermined amount of vortex for a special purpose; when another effect is not desired, the designer strives to control and reduce its occurrence. In combustion systems, the desired effect of applying vortices to injected air and fuel is in various practical situations: gasoline engines, diesel engines, gas turbines, industrial furnaces, boilers for components, and many other practical heating devices. It is widely used as an aid in the stabilization of strong combustion treatment and effective clean combustion of.

[0005]

A vortex flow results from the application of vortex motion, and a vortex velocity component (also known as a tangential or azimuthal velocity component) (also known as a tangential or angular velocity component) is
It is added to the flow by the use of vortex vanes, the use of axial plus tangential flow vortex generators or direct tangential flow into the chamber. Experimental studies show that vortices have a large effect on the field of flow: injection increase (for inert injection) suction and damping and flame size, shape stability (responsive to flow) and fuel strength Is affected by the degree of vortex added to. This degree of vortex is usually characterized by an equivalent nozzle, the vortex number S which is a unitless number representing the axial velocity of the vortex moment divided by the radius times the axial flow of the axial momentum.

That is,

[0007]

[Equation 3]

[0008] where

[0009]

[Equation 4]

Axial flow of eddy momentum including turbulent shear stress term in direction, Gx = turbulent vertical stress term in X direction and pressure term (axial thrust)
Axial flow of axial momentum including: d / 2 = nozzle radius = (x, r, θ) Velocity component in the circumferential cylindrical polar coordinate direction.

Eddy currents are generated in three main ways: Tangential inflow (axis plus tangential inflow vortex generator) 2. Guide vanes (vortex vane pack or swirler) 3. Direct rotation (rotating tube).

Among these methods, commercial burners tend to apply guide vane devices, the vanes being in such a position that they deflect the flow direction. Conventional burners typically use a fan or compressor to supply air to the combustion chamber and use fixed radial vanes to mix the combustion fuel and air. However, when the air required for combustion flows through the fixed radial vanes of a conventional burner forming a vortex, the pressure drop is very large and the turbulence intensity is very high, the burner performance is very poor. I understand.

Therefore, the main object of the present invention is to have low pressure drop and low turbulence intensity, to control local rich fuel combustion, to control combustion gas residence time, and finally to improve combustion flame stability. Providing a vortex generator for a burner adapted to generate a vortex flow.

[0014]

The present invention is illustrated for purposes of illustration only and will be more fully understood from the following detailed description and the accompanying drawings, which do not limit the invention.

FIG. 1 shows a vortex generator housed in a burner that produces the vortex air flow required for a combustion chamber according to the present invention. The burner has a refractory wall 1, a vortex generator 2 and a fuel gun 3. The symbols used in this specification have the following meanings: r ₁ : inner diameter of vortex generator; r ₂ : outer diameter of vortex generator; R ₁ : radius of curvature of lower boundary of blade; R ₂ : blade Radius of curvature of the upper boundary; θ: deviation angle (angle between the tangential direction of the blade and the axial direction); θ ₀ : deviation angle of the end of the blade; S: vortex number; L: under the blade in the axial direction Boundary protrusion length;

[0016]

[Equation 5]

U: The distance between the point of the blade and the origin.

The radius of curvature R of a point on the blade is proportional to the direct current r
To do. That is, R₁: R₂= R₁: R ₂. Deviation angle θ is the axis
0 to θ along the direction₀Gradually increase.

The vortex generator according to the present invention has a radius of r ₁ and L
It is constructed by attaching n blades equally spaced to a hollow tube having a length of. The air is simply disturbed while passing through the vortex generator, thus eliminating turbulence and pressure drop.

Robert E. Kriega Publishing Co., J. M. Beer and N. Sigir, Maraban, Florida, 1983, "Combustion Aerodynamics," p. 112, Eqn.
Referring to (5.146), the vortex number S of the present invention can be approximated by:

[0021]

[Equation 6]

Please refer to FIGS. 2, 3 and 4. The blade of the present invention is a three-dimensional curved surface. The design principle will be described below. The development of this curved surface of the surface is shown in FIG. Only the lower limit will be further described since the lower and upper limits are equal.

For any point K on the lower boundary MN, the locus of the point K is shown in polar coordinates as (u, φ), where u is the distance between the point K and the origin, and φ is KOM. Is the angle. As shown in FIG. 2, MN has a radius of curvature R as shown in FIG.
Is a cylindrical curve with radius r.

According to the Pythagorean theorem, OK ² = OT ² + TK ² (1) where OK = u, OT = r, TK = RSin θ, and then u ² = r ² + (RSin θ) ² ... (2) Therefore, u = (r ² + R ² Sin ² θ) ^1/2 (3) See FIG. 3 showing the vicinity of the point K. Point K'is the difference distance to point K

[0025]

[Equation 7]

Is the point of the curve MN having The polar coordinate of K ′ is (u + du, φ + dφ). From FIG.

[0027]

[Equation 8]

From FIG. 3 and the Pythagorean theorem,

[0029]

[Equation 9]

Here, dr = udθ.
(6) From the formula (5),

[0031]

[Equation 10]

From equation (6),

[0033]

[Equation 11]

By integration, φ = ∫ (dr / u). (9) Substituting into the equation (7),

[0035]

[Equation 12]

Where

[0037]

[Equation 13]

Expressions (3), (4), and (11) are converted into expression (10).
Assigned to

[0039]

[Equation 14]

Therefore, when the deviation angle θ at the point K is θk ′, the polar coordinates of the development point K are (u,
φ), where

[0041]

[Equation 15]

Substituting the radiuses of curvature r ₁ , r ₂ , R ₁ , R ₂ of the upper and lower boundaries of the inner and outer diameters of the vortex generator and the deviation angle θk from 0 to θ ₀ into the equation (13), The deployment of the wings is obtained. Thereafter, the flat blades can be manufactured by a hand cutter or a numerical control machine. The vortex generator according to the present invention is completed by bending the vanes according to the locus shown in FIG. 2 and fixing the vanes to the hollow tube having the radius r ₁ .

[0043] The total number of vanes can be found as shown below: radius r ₁ of the cylinder is the total number of blades n, the radius of curvature R ₁ of the lower boundary of the blade, the overlap angle of the deviation angle theta ₀ and blades of the blade edge portion α Related to ₁ . The development of the surface of the cylinder is shown in FIG. Here arcs AB and CD are the loci of the lower boundaries of two adjacent blades. The definition of the overlap angle α is the angle between the axial line passing through the point B and the tangent line of the arc CD at the point B. Part A
The lengths of C, CE, AE, EO and EO 'are shown in FIG.

Since AE = AC + CE, therefore

[0045]

[Equation 16]

Organizing equation (14),

[0047]

[Equation 17]

Here, n is the nearest natural number.

The deviation angle θ ₀ at the end of the blade is obtained as shown below.

By rearranging equation (1), the deviation angle θ ₀ at the end of the blade becomes the following equation:

[0051]

[Equation 18]

The radius of curvature of the lower boundary of the blade R ₁ is obtained as shown below.

R ₁ is obtained from the protrusion length of the lower boundary of the blade in the axial direction L and the deviation angle θ ₀ at the end of the blade as shown in FIG.

[0054]

[Formula 19]

The choice of the overlap angle α between two adjacent blades is as follows: The overlap angle α between two adjacent blades is shown in FIG. In designing a vortex generator that achieves a desired vortex number, α is proportional to θ ₀ : α = Kθ ₀ (18) where K is a predetermined constant. The higher the value of K, the more overlap between the blades. That is, the wings are more emphasized. The preferred value of K is 0.5 to 0.
The range of 75, that is, α = 0.5θ _{0 to} 0.75θ ₀ (19), whereby a satisfactory vortex effect can be generated. In fact, α
Desirable values for range from 20 ° to 45 °. The most desirable value of α is 30 °.

The method of manufacturing the vortex generator according to the present invention comprises the following steps.

1. If necessary, r ₁ , r ₂ , S, α and L
Select the value of.

2. The value of θ ₀ is obtained from equation (16).

3. The value of R ₁ is obtained from equation (17), and then the value of R ₂ is found from the rational expression R ₂ = R ₁ × (r ₂ / r ₁ ).

4. The locus of the lower boundary of the blade is plotted on the surface by the equation (13).

5. The locus of the upper boundary of the blade is plotted on the surface by the equation (13).

6. Connect the beginning and end of the lower and upper boundaries obtained in steps 4 and 5. The line forms the development of the vane.

7. Manufacture blades by deployment.

8. Bend the blades to match the trajectory shown in FIG. 2 to obtain standard blades.

9. Find the total number of blades from equation (15).

10. Repeat steps (1) to (8) to obtain n standard blades.

11. 2 for tubes with radius r ₁ and length L
By fixing n standard blades equidistantly separated by πr ₁ / n, a vortex generator according to the present invention is obtained.

For further understanding, an example is given below: r ₁ = 5.72 cm, r ₂ = 8.80 cm, S =
Select 0.7, α = 27.2 ° and L = 9.7 cm.

2. From Expression (16), θ _{0 is} 40 °.

3. From the formula (17), R ₁ = 15.1 cm
And

From the rational expression, R ₂ = 23.2 cm.

4. The above data is substituted into equation (13).
Plot the loci of the lower and upper boundaries of the blade on the plate. Figure 7
Tie the beginning and end to obtain the deployment of the blade as shown in.

5. From equation (15), the total number of blades is n = 1
Set to 9.

6. 19 blades are manufactured according to FIG.

Nineteen equally spaced blades are fixed in a tube having a radius of 7.5.72 cm and a length of 9.7 cm. Thus, the vortex generator as shown in FIG. 8 is obtained.

Although the present invention has been illustrated by way of example with respect to some preferred embodiments, it should be understood that the invention need not be limited to the described embodiments. On the contrary, various modifications and similar arrangements are included within the scope and spirit of the following claims, the scope of which should be construed in its broadest sense to include all such modifications and similar constructions.

[Brief description of drawings]

1 is a schematic sectional view showing a vortex generator according to the present invention installed in a burner.

FIG. 2 is a schematic perspective view showing the trajectory of the vanes of a vortex generator according to the invention on the surface of a cylinder.

FIG. 3 is a diagram in which the locus shown in FIG. 2 is partially exaggerated.

FIG. 4 is a diagram showing development of blades on a surface.

FIG. 5 is a diagram showing a lower boundary of a blade having a radius of curvature R on development of a surface of a cylinder.

FIG. 6 is 2 having a radius of curvature R ₁ on the development of a cylindrical surface.
FIG. 6 is a diagram showing a lower boundary of two adjacent blades.

FIG. 7 is a diagram showing the development of the blade of the first example according to the present invention at the original size.

FIG. 8 is a perspective view of a first example of the present invention.

[Explanation of symbols]

1 refractory wall 2 vortex generator 3 fuel gun r ₁ inner diameter of vortex generator r ₂ outer diameter of vortex generator R ₁ radius of curvature of lower boundary of blade R ₂ radius of curvature of upper boundary of blade θ deviation angle (tangent of blade Angle between the direction of the blade and the axial direction) θ ₀ Deviation angle of the end of the blade S Swirl number L Length of protrusion of the lower boundary of the blade in the axial direction

[Equation 20] u: distance between the point of the blade and the origin

Claims (5)

[Claims] _1. A lower boundary having an inner diameter r ₁ and an outer diameter r ₂ , having a radius of curvature R ₁ and an upper boundary having a radius of curvature R ₂ , wherein r ₁ , r ₂ , R ₁ and R. ₂ is related to the lower boundary point (u, φ) and the upper boundary point (u ′, φ ′),
We have a rational relationship where R ₁ : R ₂ = r ₁ : r ₂ , where the deviation angles of the points are both θ _k and the polar coordinates of the points of the expansion of the vane are given by: [Equation 1] Axial flow blade for vortex generator. 2. The axial flow blade for a vortex generator according to claim 1, wherein the overlapping angle of the blades is 0.5 to 0.75 times the deviation angle of the end portions of the blades. 3. The axial flow blade for a vortex generator according to claim 1, wherein the overlapping angle of the blades is 20 ° to 45 °. 4. The axial flow blade for a vortex generator according to claim 1, wherein the overlapping angle of the blades is 30 °. 5. The total number of blades n is the nearest natural number of the following formula; 2. The axial flow blade for a vortex generator according to claim 1, wherein α is an overlapping angle of the blades, and θ ₀ is a deviation angle of one end of the blades.