Integrated air foil and diamond flow vane

Abstract

A flow enhancing arrangement for ducts such as rectangular flue ducts wherein a series of tear shaped foils are spacedly mounted in the duct extending from top to bottom thereof and where a series of diamond shaped vanes also extending from the top to the bottom of the duct are spacedly mounted between the tear shaped foils to provide a more uniform flow distribution and to lower the pressure thereby. A series of baffles extending from both the tear shaped foils and the diamond shaped vanes may also be used.

Description

FIELD AND BACKGROUND OF INVENTION

The present invention is generally drawn to devices for distributing and mixing particle or injected gas laden air in ducts and more particularly to such devices as used in the ducts of power generating stations which may contain ammonia for NOx reduction.

It is known to use air foils for distributing and mixing air streams in secondary air supply ducts and selective catalyst reduction (SCR) system flues (10), as shown in FIG. 1. The usual arrangement comprises a plurality of whole foils (12) in the center of the flue and half foils (14) at the walls (16) of the flue (10). Another example of prior art air foil design is shown in FIG. 2. This is the air foil configuration for distributing and mixing economizer bypass flue gas used in the Kansas City Power & Light, Hawthorn Station in their SCR flue system. This system uses the basic FIG. 1 system but has plates (18) added. The contoured lines in the above and the remaining figures which will be described later represent the airflow distribution in the duct (10). In addition, air foils (12) have been used extensively for flow measurement and control. It is also known to use Diamond shaped flow devices for flow control with low pressure drop. For example, many commercially available dampers contain diamond shaped blades. Such devices achieve good flow control with minimal pressure group.

The disadvantage of the above described prior art arrangements are added pressure loss, potential mixing of ammonia when added, and the requirement of a larger flue to accommodate the system components.

Ammonia injection grids (AIG) with zone control are known and have been installed to distribute a prescribed rate of ammonia for NOx reducing SCR systems. Static mixers are commercially available in several forms and have been proposed to reduce thermal and/or flue gas species gradients by adding turbulent mixing in SCR flue systems. Koch and Chemineer are manufacturers that produce some such commercially available static mixers.

Design requirements for secondary flues and SCR systems include the specification of flow distribution and thermal gradients downstream of the mixing device(s). The objectives are to achieve flow uniformly and minimize thermal gradients. For example, in an SCR system mixing and flow uniformity at the ammonia injection grid should be sufficient such that catalyst performance and life is maintained. To accomplish these goals, devices such as those listed in the prior art have been utilized. While it is also desirable to minimize the unrecoverable pressure loss to the system, space restrictions limit the installation of an air foil for gas mixing and a separate AIG for ammonia distribution in an SCR system. Thus a uniform distribution system for such applications was needed which would also minimize the pressure loss therein.

SUMMARY OF INVENTION

The present invention solves the problems associated with prior art devices as well as others by combining the best features of the prior art mixing foils and diamond shaped flow device to yield an integrated device that provides an improved system design. The present invention is unique because it combines air foils and diamond vanes to produce a device that provides a uniform flow distribution with minimal pressure drop. As noted, both air foils and diamond vanes have been used separately to accomplish flow control, however, these systems have not been used together in a manner proposed in the present invention.

In another embodiment of the present invention, plates or baffles are added to both the mixing foils and the diamond shaped devices to produce a uniform flow and low pressure drop device especially adapted for flue gas applications.

In view of the foregoing, it will be seen that one aspect of the present invention is to provide mounted device for improved uniformity of flow distribution.

Another aspect of the present invention is to provide a duct mounted device for reduced pressure drop in the duct.

Another aspect of the present invention is to provide a flue duct mounted device for improving flow distribution and lowering the pressure drop therein.

These and other aspects of the present invention will be more fully understood upon a review of the following description of the preferred embodiment when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a prior art foil arrangement for ducts.

FIG. 2 is a prior art foil and plate or baffle arrangement for flue ducts.

FIG. 3 is a foil and diamond arrangement of the present invention for ducts.

FIG. 4 is another embodiment of the present invention using a foil and diamond arrangement with divider plates.

FIG. 5 is a side view of the foil and diamond arrangement seen in FIG. 3 and FIG. 4.

FIG. 6 is a rear view of the foil and diamond arrangement of FIG. 5.

FIG. 7 is a front view of the foil and diamond arrangement seen in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and more particularly to FIGS. 3 and 5-7, an improved flow system duct arrangement is shown which integrates the air foils (12) with diamond shaped flow vanes (20). Flow uniformly downstream of the foil throats is achieved with the arrangement. A comparison of the distributors with and without the diamonds (20) (FIGS. 1, 2, vs. FIG. 3) clearly demonstrates the improved flow distribution with the diamonds (20). The aerodynamic shapes of the diamonds (20) and airfoils (12) are also advantageous to the design objective of minimizing system unrecoverable pressure loss. The advantage exists whether or not the foils (12) will be used or particle injection for reducing NOx due to their aerodynamic shape which is exposed to the gas stream. Thermal gradients are also minimized by distributing the flue gas for temperature control over the cross section of the flue.

For SCR applications with ammonia injection between the foils (12), mixing of ammonia with the flue gas is improved because of the flow uniformity provided with the additional use of the diamond vanes (20).

An alternative arrangement to the invention is shown in FIG. 4 wherein plates or baffles (18) are mounted to both the foils (12) and the diamonds (20). The baffles (18) from the diamonds (20 extend across the space of the foils (12). This arrangement promotes flow uniformity between the foils (12).

As seen from FIGS. 5-7, the duct (16) is rectangular and the foils (12) and diamonds (20). Both extend from the top to the bottom of the duct (16). The foils (12) are tear-shaped having a rounded end (19) and a sharp end (21). The baffles or plates (18), when they are used, also extend from the top to the bottom of the duct starting at imaginary lines (22, 24) of the rounded end (19) of the foils (12) and leading edges (23) of the diamonds (20) respectively. The plates (18) are shown in dotted lines at FIG. 5 as alternate embodiments.

Certain modifications and additions will occur to those skilled in the art area upon reading this disclosure. It will be understood that all such were deleted herein for the sake of conciseness and readability but are intended to all with the scope of the following claims.

Claims

1. A flow enhancing arrangement for ducts having fluid flow therein comprising: a series of tear-shaped foils spacedly extending across the duct; and a series of diamond shaped vanes shapedly extending between said series of tear-shaped foils.

2. A flow enhancing arrangement for ducts as set forth in claim 1 including a series of baffles extending from said tear shaped foils and from said diamond shaped vanes.

3. A flow enhancing and arrangement for ducts as set forth in claim 2 wherein said tear-shaped foils have a rounded end and a sharp end and wherein said baffles extend from said rounded end of said foils.

4. A flow enhancing arrangement for ducts as set forth in claim 1 wherein said diamond shaped vanes have sharp front and back ends and said baffles extend from said front end.

5. A flow enhancing arrangement for ducts as set forth in claim 1 wherein said tear-shaped foils have a rounded end and a sharp end and wherein said baffles extend from said rounded end of said foils.

6. A flow enhancing arrangement for ducts as set forth in claim 5 wherein said diamond shaped vanes have sharp front and back ends.

7. A flow enhancing arrangement for ducts as set forth in claim 5 wherein the duct is a rectangular flue duct.