2. Description of the Prior Art In many industrial settings it is often necessary to combine a number of different gaseous (or liquid) materials. For example, it may be necessary to mix combustion, high temperature gases from conventional burners (gas- or oil-fired) with relatively low temperature process air (as may be encountered with air dryers). Alternatively, it may be necessary to mix exhaust gas (high temperature) from the outlet of gas turbines with process air from, for example, air dryers. The structure of these arrangements typically includes a first air stream traveling through a duct (or similar enclosure), with the second stream introduced into the duct via an input port.

In order to effect a combination of such dissimilar streams, prior art arrangements typically relied upon the utilization of a"stirring motion"and turbulence downstream from the injection point of the second air stream. In

generai, such an arrangement requires a significant amount of energy (thus reducing the flow rate of the combined stream), as well as requiring a relatively long distance to ultimately combine the two streams and create a stream of homogeneous properties. In an alternative prior art arrangement, deflector vanes are inserted downstream of the injection jet to induce counter rotational flows in the ducting.

Thus, a need remains in the prior art for an improved arrangement for facilitating the combination of dissimilar streams, wherein the arrangement is both energy efficient and utilizes a minimum length of additional ducting.

SUMMARY OF THE INVENTION The need remaining in the prior art is addressed by the present invention which relates to an arrangement and method for combining dissimilar streams and, more particularly, to a baffle configuration for utilization within a duct or similar enclosure to increase the efficiency at which two (or more) dissimilar streams of material (for example, two air streams at different temperatures) may be combined to form a homogeneous stream.

In a preferred embodiment of the invention, a tapered baffle is disposed within a duct upstream of an input source for a second air stream, the second air stream to be combined with a first air stream traveling through the duct. The duct is configured to comprise parallel and spaced-apart walls forming the floor and ceiling of the duct. The input port for the second stream is inserted through the floor of the duct and the baffle is tapered in a manner such that the widest

part of the baffle is nearest the input port, narrowing across the width of the duct as it approaches the ceiling of the duct. A first air stream (e. g., low temperature) is traveling through the duct and a second air stream (e. g., high temperature) is introduced via the input port. The flow of the first stream across the baffle results in creating a low pressure area along the face of the baffle nearest the input port. The second stream, introduced by the input port, then naturally flows into the low pressure area created by the baffle configuration of the present invention, resulting in efficient mixing with the first stream.

In an alternative embodiment of the present invention, a baffle may be configured to as to include a gap area across the bottom edge of the baffle, near the floor of the duct. This embodiment is particularly well-suited for arrange- ments where it is desirous to combine a low temperature air stream with a high temperature air stream. In particular, the gap allows for a stream of the low temperature air to pass underneath the baffle and be pulled into the low pressure region in front of the baffle so as to provide for additional cooling of the baffle structure.

The arrangement and method of the present invention may be used to combine any two dissimilar materials, for example, steam and air, low humidity air and high humidity air, nitrogen and oxygen, or even two liquids (such as a clear liquid and an mulsion or suspension). In particular, the ability to combine two dissimilar streams of material (such as low temperature air and high temperature air) is extremely useful in the paper and textile industries. For example, in the fabrication of woven or knitted fabrics, as well as certain non-

woven materials, it is necessary to"air dry"the material with a homogeneous air stream (often referred to in the art as"through air drying"). In accordance with the teachings of the present invention, the homogeneous air stream is formed by a combination of low temperature air and high temperature air utilizing a baffle interposed between the air streams.

In yet another embodiment of the present invention, a non-tapered baffle may be utilized to provide for the combination of two or more streams of material. In particular, a non-tapered baffle may be used in situations where a first, high velocity stream is to be combined with a second, low velocity stream.

In the prior art, if the low velocity stream were to be injected into the path of the high velocity stream, the input port of the low velocity stream could become strained, thus misdirecting the flow of low velocity material across the floor of the duct, resulting in inefficient mixing. In accordance with the teachings of the present invention, a baffle configured as a non-tapered plate functions to shield the input port from the path of the high velocity stream. Thus, the low velocity material is able to extend across the width of the duct, resulting in more efficient mixing downstream.

In a further embodiment of the present invention, a plurality of dissimilar streams may be combined to form one, homogeneous stream by utilizing a plurality of separate baffles, each baffle being disposed upstream of one of a plurality of input ports. The plurality of input ports may be disposed in any desired location with respect to the enclosure. For example, the ports may be positioned along the length of the enclosure or, alternatively, may be positioned

across the width of the enclosure. Additionally, the baffle may comprise a solid piece of material or, alternatively, may include one or more perforations.

These and other embodiments of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the drawings, where like numerals represent like parts in several views : Figure 1 illustrates a view in perspective of an exemplary embodiment of the mixing arrangement of the present invention ; Figure 2 contains a view of the arrangement of Figure 1, taken along line 2-2 ; Figure 3 contains an alternative view of the arrangement of Figure 1, taken along line 3-3 ; Figure 4 illustrates an alternative embodiment of the present invention, including a gapped baffle ; Figure 5 is a view of the arrangement of Figure 4 taken along line 5-5 ; Figure 6 is an alternative view of the arrangement of Figure 4, taken along line 6-6 ; Figure 7 is a view of the arrangement of Figure 5, taken along line 7-7, illustrating in particular the gap area included within the exemplary baffle structure ;

Figure 8 illustrates, in a perspective view, an alternative arrangement of the present invention utilizing a plurality of baffles and associated input ports ; Figure 9 contains a side view of the arrangement of Figure 8, taken along line 9-9 of Figure 8 ; and Figure 10 is a graph illustrating the results achieved utilizing the arrangement of the present invention as compared with a prior art arrangement, in particular, the improvement in temperature"mixing"achieved when combining low temperature air with high temperature air.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 illustrates an exemplary mixing arrangement 10 of the present invention. As shown, the arrangement comprises a tapered baffle 12 disposed in a duct 14 such that widest edge 16 of baffle 12 is in proximity with bottom wall 18 of duct 14. Baffle 12 then tapers into a point 20 in the proximity of top wall 22 of duct 14. It is to be understood that while duct 14 of this embodiment is illustrated as comprising a rectangular cross-section, any suitable enclosure of any predetermined geometry may be utilized. Additionally, the geometry of baffle 12 may differ in particular circumstances. For the arrangement of Figure 1, baffle 12 is illustrated as comprising a conic section.

Other tapered or non-tapered configurations may be utilized and fall within the spirit and scope of the present invention.

Input port 24 protrudes through bottom wall 18 of duct 14 and is located downstream (with respect to the direction of the flow through duct 14) of baffle 12. The distance d between the center of input port 24 and baffle 12 (shown in

Figure 2), is a matter of design, and provides either greater or lesser air pressure in the area therebetween, as a function of separation d.

In the embodiment as illustrated a first gas stream G, is traveling along the length I of duct 14. Gas stream G, may comprise oxygen, nitrogen, stream, air, or any other gaseous stream. A second gas stream G2 travels through tubing 26 and is introduced into duct 14 via input port 24. In accordance with the teachings of the present invention, the flow of first gas stream G, past tapered baffle 12 creates a cavity of low pressure on the downstream side 28 of baffle 12. The path of second gas stream G2, as shown in Figure 1, thus enters the low pressure area. The natural tendency of the jet of injected gas to broaden with increasing distance from the injection point thus causes increasing amounts of second gas stream G2 to flow outside the low pressure cavity and be swept into the flow of first gas stream G, and thereby be evenly distributed across the face (width) of first gas stream G,. The turbulence created by the tapered baffle structure thus contributes to spreading the mixing action across the front of the flow of first gas stream G,.

It is to be understood that the mixing of the present invention achieved by the utilization of the tapered baffle can be further enhanced by any of the following attributes : (1) modifying the cross section area of duct 12 so as to control the velocity of gas stream G, (e.g., decreasing the cross section of duct 14 in the region of baffle 12 and input port 24 will increase the velocity of gas stream G,) ; (2) modifying the aspect ratio of duct 14 (thus controlling the width and breadth of the front of the flow of gas stream G,) ; or (3) modifying the

velocity at which second gas stream G2 exits input port 24.

Figure 2 illustrates a side view of the arrangement described above in Figure 1. As shown in this view, input port 24 protrudes a predetermined height h through bottom surface 18 of duct 14. The center of input port 24 is illustrated as being disposed a predetermined distance d downstream from the back edge 30 of baffle 12. Both the height h and the distance d can be controlled so as to provide the most efficient mixing of the two streams, wherein these parameters will be function of the various conditions associated with the two streams (e. g., temperature, composition, humidity, flow rate, etc.).

As clearly seen in this view, baffle 12 is sized such that top point 20 does not come into contact with top surface 22 of duct 14. The flow of gas stream G, around baffle 12 thus produces low pressure cavity area 32. Gas stream G2 as it exits input port 24 thus naturally tends to enter cavity 32 and results in increased efficiency in the mixing of gas streams G, and G2.

As mentioned above, another factor that effects the efficiency of the arrangement of the present invention is the geometry of the baffle. Figure 3 illustrates a top view in perspective of the mixing arrangement of Figure 1. As shown, sidewall 34 of baffle 12 is formed to comprise an arc of radius r, where this angular displacement has been found to control the overall dimensions of low pressure cavity 32, as well as the actual pressure within the cavity area.

One particular environment for the utilization of the method of the present invention, as mentioned above, is the"through air"drying process associated with the fabrication of woven and non-woven fabrics, where it is often

necessary to combine low temperature and high temperature air streams. Figure 4 illustrates a particular embodiment of the present invention that is well-suited to such an environment. This environment is suitable for treating light-weight, soft paper products including those having a basis weight of less than 5 and greater than 200 grams per square meter. In particular, mixing arrangement 50 comprises a baffle 52 disposed in a conduit (or similar enclosure) 54, where baffle 52 is located upstream (with respect to the direction of flow through conduit 54) a predetermined distance d (illustrated in Figure 5) from an input port 56. As shown, a first stream of low temperature air ALow travels along the length of conduit 54 and impinges upon baffle 52 so as to create a low pressure cavity 56 in the interior region of baffle 52. A second stream of high temperature air AHIGH travels through tubing 58 and enters conduit 54 via input port 56. For this particular low temperature/high temperature embodiment of the present invention, baffle 52 includes a lower gap area formed by displacing the bottom surface 58 of baffle 52 a predetermined gap distance a (illustrated in Figure 5) from lower surface 60 of conduit 54. As also seen in Figure 4, baffle 52 includes a number of perforations 53, where these perforations serve to "cool"baffle 52 by allowing a larger quantity of low temperature air to pass therethrough. It is to be understood that the number and size of the perforations should be limited so as to not disrupt the low pressure region created by the baffle structure. Another feature of this particular embodiment is that input port 56 protrudes into conduit 54 a height h greater than the gap distance g (refer to Figure 5). A particular advantage associated with this

arrangement is that the injection point of stream AHIGH will remain above the flow path of ALoww Therefore, the passage of stream ALow will not disrupt stream AHIGH, which will enter the low pressure region unimpeded.

Figure 6 illustrates a top view of arrangement 50. As illustrated in this particular embodiment, tapered baffle 52 includes a triangular geometry and comprises a pair of sidewalls 62 and 64 displaced by a predetermined angle 0.

Low temperature air stream ALow travels past baffle 52 so as to create a low pressure region 66 between input port 56 and baffle 52. Therefore, high temperature air stream AHIGH will naturally enter this low pressure cavity and effectively mix with stream ALow to form output air stream Aulx, Figure 7 contains a perspective view of the arrangement of Figure 5, taken along line 7-7. Evident in this view is the gap area 55 between baffle and lower surface 60 of conduit 54. As shown, only small leg portions 57, 59 of baffle 52 are in contact with surface 60 (for stability purposes), allowing for a steady stream of ALow to pass through gap area 55 and provide cooling to baffle 52.

As mentioned above, the utilization of a baffle arrangement in accordance with the present invention may be particularly advantageous in situations where it is necessary to inject a low velocity stream into the path of a high velocity stream. Figure 8 illustrates one such arrangement of the present invention that is particularly well-suited for this purpose. Additionally, Figure 8 illustrates an arrangement including a pair of baffles and associated input ports since, as discussed earlier, the technique of the present invention may be extended to

provide for the combining of any number of dissimilar materials. Indeed, although only two exemplary baffles and associated input ports are illustrated, it is to be understood that any desired number of such baffles and associated input ports may be utilized and fall within the spirit and scope of the present invention. Additionally, in accordance with the teachings of the present invention, the multiple baffle/port arrangements may be disposed in any desired fashion within the enclosure. For example, they may be positioned along the length of the enclosure or, alternatively, across the width of the enclosure, or any suitable combination. In general, their location within the enclosure (as long as the baffle is disposed upstream of its associated input port) is not relevant to the teachings of the present invention.

Referring in particular to Figure 8, arrangement 70 includes a first baffle plate 72 and a second baffle plate 74, each baffle plate being disposed to extend across the width of an enclosure 76. A first stream of high velocity material VH (for example, a clear liquid) is traveling through enclosure 76 such that it first impinges and passes over first baffle plate 72, subsequently striking and passing over second baffle plate 74. A second stream of low velocity material V" (for example, an emulsifier) is introduced into enclosure 76 via a first input port 78. Similarly, a third stream of low velocity material V,2 (for example, an emulsifier of a different composition and/or velocity) is introduced into enclosure 76 via a second input port 80. In accordance with the teachings of the present invention, each input port is located a predetermined distance downstream of its associated baffle plate. As with the other embodiments

discussed above, arrangement 70 allows for the formation of low pressure areas in the region between each baffle plate and its associated input port. Thus, in this particular embodiment, the low pressure areas allow for low velocity streams V" and V,2 to be injected into a sufficient volume of enclosure 76 so as to result in efficient mixing. Additionally, as shown in Figure 8, any baffle structure of the present invention may be formed as a multiple unit structure, with the capability to add or remove separate units to effect different results.

For example, a second baffle section 82 may be attached to the top portion of first baffle plate 72, where second section 82 would allow for the baffle structure to perform with even higher velocity materials. It is to be understood therefore, that the baffle size and shape may be adjusted, over time, to accommodate for various velocities of materials, where the adjustment may best be accomplished by utilizing a multiple unit baffle structure.

Figure 9 contains a cut-away side view of arrangement 70 of Figure 8, taken along line 9-9. As previously discussed, the utilization of a baffle in situations where a low velocity stream is injected into a high velocity flow is particularly advantageous. In a conventional arrangement without the baffle structure of the present invention, the force of high velocity stream VH would cause first input port 78 to bend, as shown in phantom in Figure 9. The injection path of low velocity material V" is therefore perturbed, further reducing the mixing efficiency of streams VH and VL1. Therefore, utilization of baffle plate 72 in accordance with the teachings of the present invention acts as a physical barrier between the high velocity stream and the input port, allowing the low

velocity material to be injected in the desired direction.

A numerical depiction of the effectiveness of the present invention is included in Figure 10. In particular, Figure 10 is a graph illustrating temperature variation, as a function of distance, along a chamber, such as duct 14 or conduit 54, when utilizing the arrangement of the present invention to combine to air streams of different temperatures. For the results as illustrated in Figure 9, a first stream of air having an ambient temperature of 250°F is to be combined with a second stream of air having an ambient temperature of 2440°F. The efficiency of the combination of the air streams may be measured by assessing the temperature variation at any point downstream of the point at which the two streams begin to combine. The graph in Figure 10 includes measurements of this temperature variation at three separate locations - a first point B at a distance of 575 inches beyond the location of the input port for the high temperature stream, a second point C at a distance of 779 inches beyond the input port, and a third point D, a distance of 983 inches beyond the input port.

The temperature variations associated with a convention, prior art structure are indicated as circles in Figure 9. The improvement in mixing efficiency associated with utilization the baffle arrangement of the present invention is evident from viewing the temperature variations, indicated as triangles, measured at the same three locations B, C and D. In particular, at location B, the temperature variation dropped from 500°F to 60°F. At location C the variation was reduced from 320°F to 24°F and, lastly, at point D the variation was reduced from 180°F to only 16°F. It is to be understood that these data points represent temperature variations (as a function of location across the width of the enclosure at the associated point), not the actual ambient temperature of the mixed air stream.