GB2253476A - An adjustable burner air swirl generator - Google Patents

Abstract

A swirl generator to supply air A, B radially inwardly to an outlet 14 surrounding fuel pipe 1 comprises adjustable generally radial vanes 31 in a housing 10 connected to a combustion chamber. Each radial vane 31 has a fixed inner pivot 32 and a roller 33 at its outer end engaging a radial elongate guide slot 44 of a vane adjusting mechanism 40. To adjust the relative radial orientation of the vanes, a plate 43 with a plurality of slots 44 is rotated by a handle 42 outside the housing 10 which has air outlets 16 and a flow smoothing apertured plate 2. <IMAGE>

Description

A SWIRL GENERATOR WITH IMPROVED RADIAL VANES The present invention relates generally to a swirl generator, and particularly to a a swirl generator with improved vanes.

A burner is one of the most important parts in a combustion system. The performance of the burner not only influences the combustion efficiency but also closely relates to the stability of combustion flame, the effective utilization of the fuel, and the discharge of pollutants. Improper combustion technology and improper selection of burners not only influences the effective use of energy, but also results in air pollution due to emission of large amount of hazardous matters such as NOx on account of undue combustion.

A conventional burner usually feeds air into the combustion chamber by means of a fan or a compressor having blades of fixed radial type to mix the air with the fuel for burning. However, it is found that the performance of the burner will become very poor if the pressure drop is too large and the turbulence intensity is too high when the air flows through the blades of fixed radial type in the conventional burner for forming swirling flow which is required for combustion.

In order to improve the performance of the burner by decreasing the amount of NOx formed in the combustion process and increasing the stability of the combustion flame, it is necessary to reduce the peak temperature of the flame and the residence time of combustion gas, and to form local fuel-rich combustion.

It is therefore a primary object of the present invention to provide a swirl generator, for burner, adapted to provide a swirling flow having low pressure drop and low turbulence intensity, and being capable of controlling local fuel-rich combustion, lowering the peak temperature of combustion flame, controlling the residence time of combustion gas, and improving combustion flame stability, In accordance with the present invention, a swirl generator, adapted to produce swirling flow required for a combustion chamber, comprises a housing connected to a combustion chamber at one end, with a hollow fuel pipe axially extending through the housing into the combustion chamber; a vane pivoting mechanism provided within the housing; a radial vane mechanism including a plurality of radial vanes, circumferentially arranged around the axis of the housing, each of which is pivoted to the vane pivoting mechanism near the inner end thereof, and a plurality of guide rollers each of which is rotatably supported near the outer end of one the radial vane; a vane driving mechanism including a manually operating means which may be operated from outside the housing so as to rotate the vane driving mechanism relative to the vane pivoting mechanism; and a plurality of substantially radial elongate guide slots adapted to receive therein one of the guide rollers, respectively, and guide the radial movement of the guide rollers; whereby each of the radial vanes may be rotated around the pivotal inner end thereof so as to adjust its orientation angle relative to a radial direction when the vane driving mechanism is operated to rotate relative to the vane pivoting mechanism and thus making each of the guide rollers, together with the outer end of the radial vane, to move along a corresponding guide slot.

The present invention can be more fully understood by reference to the following description and accompanying drawings, which form an integral part of this application: Fig. 1 is a fragmentary sectional view showing the construction of a swirl generator with improved vanes, in an assembled state, according to the present invention; Fig. 2 is an exploded perspective view of part of the comprising members of the swirl generator illustrated in Fig. 1, with some of the members being partially taken away to clearly show their hiden structures; Fig. 3A is a front view of a drive plate included in the swirl generator shown in Fig. 1; Fig. 3B is a sectional view of the drive plate shown in Fig. 3A; Fig. 4A, 4B and 4C are schematic views, respectively, showing radial vanes at three angular positions of different orientation angles; and Fig. 5 is a diagram, obtained from experiments, showing the relation between the orientation angle of the radial vanes in the swirl generator of the present invention and the Swirling number of the swirling flow produced by use of the swirl generator of the present invention.

As can be seen from Figs. 1 and 2, in accordance with the present invention, a swirl generator adapted to produce swirling air flow required for a combustion chamber (not shown), mainly comprises a hollow housing 10, a vane pivoting mechanism 20, a radial vane mechanism 30, and a vane driving mechanism 40.

The housing 10 has an axis X-X, a first side wall 11 and a second side wall 12 at the two axial ends thereof, and a first opening 13 and a second opening 14 provided, respectively, in the central areas of the two side walls 11 and 12. An air intake hole 16 is provided in the first side wall 11 for allowing the air to enter the housing 10. The housing 10 is connected to a combustion chamber (not shown) through the second opening 14 by means of a flange 15. A straightening plate 2 provided with a plurality of through holes 3 is detachably installed within the housing 10 for straightening the air flowing therethrough. A hollow fuel pipe 1 extends from the first opening 13 through the straightening plate 2 and the second opening 14 into the combustion chamber.

Within the hollow fuel pipe 1 may be provided with fuel atomization system and ignition system (not shown).

Within the housing 10 and near the second opening 14 is provided with the vane pivoting mechanism 20 which includes a mounting plate 21 detachably fixed to the second side wall 12, a guide seat 22 provided thereon an annular guide groove 24 around the axis X-X of the housing 10 for a purpose to be described latter, and a plurality of separate connecting bars 23 interconnecting the mounting plate 21 and the guide seat 22 so as to secure the guide seat 22 to the mounting plate 21 while allow the air to. flow radially inwards through the spacing between each pair of adjacent connecting bars 23.

The vane driving mechanism 40 comprises a cylinder 41 rotatably sleeved around the fuel pipe 1, a handle 42 which is connected to the cylinder 41 and may be operated from outside the housing 10 so as to rotate the cylinder 41, a drive plate 43 which is connected to the cylinder 41 and is formed with a plurality of substantially radial elongate guide slots 44 (see also Fig. 3A and 3B), and at least one guide wheel 45 which is rotatably supported by the drive plate 43 and is adapted to run along the annular guide groove 24 so as to guide a smooth relative rotation between the vane driving mechanism 40 and the vane pivoting mechanism 20.

The radial vane mechanism 30 comprises a plurality of radial vanes 31, circumferentially symmetrically arranged around the axis X-X of the housing 10, each of which has an inner end and an outer end and is pivoted to the mounting plate 21 and the guide seat 22 near its inner end by means of a pivot pin 32, and a plurality of guide rollers 33 each of which is rotatably supported by a radial vane 31 near the outer end of the latter and is received in and guided by a guide slot 44 in the drive plate 43.Thus, each of the radial vanes 31 may be rotated around its pivotal inner end so as to adjust its orientation angle relative to a radial direction when the vane driving mechanism 40 ( the drive plate 43) is operated to rotate relative to the vane pivoting mechanism 20 and thus making each of the guide rollers 33, together with the outer end of the associated radial vane 31, to move radially under the guidance of a corresponding guide slot 44.Since it is easily understood that, due to symmetry, all the radial vanes can be synchronously adjusted in their orientation angles when the. vane driving mechanism 40 is operated to rotate relative to the vane pivoting mechanism 20, Figs. 4A to 4C representatively show only one radial vane 31 located, respectively, at three different positions of orientation angles OA, Un, and dc- In fact, the orientation angle of the radial vane may be adjusted in the range from about 0 to about 800 according to the vortex intensity of required the swirling air flow to be produced by the swirl generator.

In order to find the relationship between the orientation angle e of the radial vane in the swirl generator of the present invention and the Swirl Number S of the swirling air flow produced by the same swirl generator, experiments are performed with respect to several different orientation angles 0, and the values of corresponding Swirling Numbers S are detected by use of a LDV experiment apparatus. The result is shown in Fig. 5 wherein the abscissa and ordinate represent the orientation angle e and Swirling Number S, respectively.

From this diagram, it can be seen that the Swirling Number S of the produced swirling air flow is approximately proportional to the orientation angle 0 of the radial vanes 31, and that vortex intensity required for common industrial burners (namely, S= 0.4 to 1.2) may be obtained by use of the swirl generator of the present invention. It is also found that when the orientation angle B of the radial vane gradually increases to make the Swirling Number S reach the value of about 0.6, a recirculation zone is established in the central aera of the combustion chamber (not shown) near the front end (not shown) of the fuel pipe 1 through which the fuel is sprayed into the combustion chamber.The thus formed recirculation zone is capable of stabilizing combustion flame, increasing the residence time of combustion gas, and resulting in a more efficient combustion.

The working condition of the swirl generator in accordance with the present invention will now be described by referring to Fig. 1. Prior to working, according to the required Swirling Number S with reference to the diagram shown in Fig. 5, the orientation angle of the radial vane mechanism is adjusted to a desired value by operating the handle 42 from outside the housing 10 and thus rotating the vane driving mechanism 40 to a proper angular position. The required air flow is first introduced through the radial vane mechanism 30 in the direction of Arrows A and B, and then the produced swirling air flow of desired Swirling Number ( or vortex intensity ) is fed into the combustion chamber through flange 15.

In addition to availability of obtaining a swirling air flow of desired vortex intensity, it is also proved in actual operation that a swirl generator of the abovedescribed structure may avoid the drawbacks of resulting in high pressure drop and turbulence intensity due to mechanical loss as in the case when the air is introduced through conventional radial vanes. Besides, air flow produced by the swirl generator of the present invention will have larger radial momentum to compensate the energy loss due to viscosity effect, thus improving the performance of the burner.

Claims (5)

Claims

1. A swirl generator with improved radial vanes, comprising: a housing having an axis, and a first opening and a second opening located at the two axial ends thereof, the housing being connected to a combustion chamber at the second opening, with a hollow fuel pipe extending from the first opening through the second opening into the combustion chamber; a vane pivoting mechanism provided within the housing near the second opening; a radial vane mechanism including a plurality of radial vanes, circumferentially arranged around the asis of the housing, each of which is pivoted to the vane pivoting mechanism near the inner end thereof, and a plurality of guide rollers each of which is rotatably supported near the outer end of one the radial vanes;; a vane driving mechanism including a manually operating means which may be operated from outside the housing so as to rotate the vane driving mechanism relative to the vane pivoting mechanism; and a plurality of substantially radial elongate guide slots adapted to receive therein one of the guide rollers, respectively, and guide the radial movement of the guide rollers; whereby each of the radial vanes may be rotated around the pivotal inner end thereof so as to adjust its orientation angle relative to a radial direction when the vane driving mechanism is operated to rotate relative to the vane pivoting mechanism and thus making each of the guide rollers, together with the outer end of the associated radial vane, to move radially along a corresponding guide slot.

2. A swirl generator with improved radial vanes as claimed in claim 1, wherein the vane driving mechanism comprises a cylinder rotatably sleeved around the fuel pipe, a handle which is connected to the cylinder and may be operated from outside the housing so as to rotate the cylinder, and a drive plate which is connected to the cylinder and is formed with the guide slots.

3. A swirl generator with improved radial vanes as claimed in claim 1, wherein the vane pivoting mechanism further comprises an annular guide groove disposed-around the axis of the housing, and wherein the vane driving mechanism further comprises at least one guide wheel adapted to run along the guide groove so as to facilitate a smooth relative rotation between the vane driving mechanism and the vane pivoting mechanism.

4. A swirl generator with improved radial vanes as claimed in claim 1, wherein the orientatioin angle of each radial vane may be adjusted in the range from about 0 to about 800.

5. A swirl generator with improved radial vanes as hereinbefore described with reference to Figs. 1 to 5.