Air Distributing Channel

Abstract

Air is distributed uniformly and at reduced outflow speed from the outlet of the channel. The perforated inner wall defines an air passage of linearly decreasing cross-section with the channel bottom to uniformly distribute the air. The next perforated wall defines a partitioned turbulence space to reduce air speed. The domed perforated wall defines a second turbulence space to further reduce air speed.

Description

This invention relates to an air distributing channel particularly for textile machines.

In air technology, difficulties have been known to arise, under certain conditions, in the uniform distribution of air to be blown out laterally from an air-supply channel. The chief difficulty has been based on the fact that generally the inflow speed into the channel has been made greater than the outflow speed. Without special devices, this has the result that a substantially greater amount of air emerges at the channel end opposite the inflow than at the beginning of the channel because the flow energy becomes progressively converted into static pressure.

The simplest technical solution to making the initial or inflow speed into the distributor channel less than the outflow speed has very often not been possible due to a lack of space. Generally, therefore, in the case of room-ventilating equipment, the initial speed has been made about twice that of the outlet speed. Thus, with the usual speed relationships for ventilating rooms, it has been known to install throttling elements, such as flaps or shutters, in the channel at spacings, e.g. spacings of 5 to 10 quasi-diameters (the quasi-diameter of a channel is the diameter of circle equal in area to that of the channel cross-section) for the purpose of destroying the rise of static pressure. This has severed to make the lateral emergence of the air uniform.

In certain cases, particularly in the case of the individual or internal air-conditioning of textile machines, the space available for the air channel inside the machine is very limited. Thus, the initial speed has to be very high in order to bring the required quantity of air into the machine. Moreover, in this case, not only must the initial speed in the channel be made unusually great, but this air should also emerge into the machine at a particularly low speed, somewhat like spring-water so as not to cause derangements of the machine, or defects in the threads or in the woven cloth by whirling dust and bits of fibers. In such cases, the initial speed or inflow speed into the channel has been made to correspond to 10 to 20 times the outflow speed from the channel. Thus, the static pressure which is, as is well known, proportional to the square of the speed is 100 to 400 times higher at the channel end than at the beginning of the channel. With such great differences of speed, the known measures described are no longer of use, because that would require too great a number of throttling locations.

It is known to be possible to inhibit the pressure build-up by continuously installing a filtering or felt insert along the channel or by loosely filling the channel with a loose filling-material, e.g. steel shavings. From the aerodynamic point of view, such measures would be very advantageous, but they do not work in practice because such inserts act at the same time as dust catchers and become plugged up in a short time. It is moreover practically impossible to clean the inserts and therefore replacements are required every time an insert becomes plugged. This, of course, causes great expense.

Further, because of impurities in the air to be distributed, it has also been necessary to provide a minimal dimension for each individual opening for the outflow of an air channel. For example, this dimension has amounted to about 3 millimeters.

Accordingly, it is an object of the invention to create an air-distributing channel having an air outlet out of which air is uniformly distributed over the entire length of the outlet while emerging at a low speed.

It is another object of the invention to conduct air through an air channel without plugging-up the outlets of the channel with impurities.

Briefly, the invention provides a distributor channel having an air outlet with a plurality of walls between which are situated turbulence spaces. In addition, in order to uniformly distribute the air over the entire length of the air outlet, a section of the channel disposed upstream of the wall flanking the first turbulence space is tapered down, in a substantially linear way, toward the end opposite the inlet. The flanking wall thus has an effective opening cross-section that corresponds, at least closely, to that at the channel inlet. Furthermore, the adjoining walls of the air channel are provided with air openings which gradually increase in their effective opening cross-section to effect a reduction of speed of the air passing therethrough. Finally, the turbulence space between the first and second walls has baffle plates spaced along the entire length of the air outlet to nullify the flow components in the lengthwise direction.

The individual components of the air channel have different functions. That is, the tapered-down section of channel, in cooperation with the first wall provided with openings, produces a uniform distribution of air along the entire length of the air outlet. In order to ensure uniform distribution of the air, the effective opening cross-section of the first wall (which, as is well known, is defined as the product of the actual total cross-section of all holes in a wall, of the concentration or density coefficient .alpha., approximately 0.7 to 0.75, and of the sine of the angle of slope in the flow direction relative to the plane of the flow-through cross-section), shall be at least approximately equal to the opening cross-section at the channel entrance. In this way, the flow speed through the first wall remains at least approximately equal to that at the channel inlet. Thus, it is not possible for a greater static pressure to build up that would result in unequal distribution. On the other hand, a speed reduction or a pressure reduction, by means of a greater effective opening cross-section relative to the inflow cross-section would not be allowable because that would impair uniform distribution.

In passing through the next walls, whose effective flow cross-sections gradually increase from wall to wall in the outflow direction, the speed of the outflowing air becomes gradually decreased. The turblence spaces, situated between the walls therefore have the function of obtaining a smoothing and equalization of the flow, through the individual openings in separate streamlines, before the flow reaches the next wall.

Because it is not possible to completely nullify the flow components in the lengthwise direction of the channel by the aid of the first wall, the turbulence spaces beyond this wall must be provided with baffle plates, which can advantageously be made as partitions. For the sake of simplicity, these plates are, in their turn, set at constant spacing, amounting to about one time to four times the quasi-diameter of the channel, and are distributed along the length of the air outflow.

The number of walls following the first wall can, to a certain extent, be optional. This depends on the desired reduction of speed, on the room available, and on economic considerations, because the installation of each new wall means an additional expense. In this connection, it has been found to be advantageous for the ratio between the effective flow cross-sections of two successive walls to be made at least approximately constant.

A simple constructional solution for the tapering down of the channel cross-section is obtained when, for at least a part of the length of the air outflow, a wedge shaped filler is installed in the channel between the wall flanking the first turbulence space and a parallel channel delimitation. This permits the partitions present in the first turbulence space to be made of equal size in the region in which the channel tapers down by means of the wedge-shaped filler.

In order to obtain as uniform as possible a distribution of the air over an angle of 180.degree. perpendicular to the lengthwise direction in the space to be ventilated, it is advantageous for the last wall, provided with openings, to be made in the form of an arched cover.

It is possible to obtain very simple fabrication of walls provided with a differing number of inflow openings when, for exact adjustment of the flow-through cross-section, the walls are made of two perforated plates offset relative to one another.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 schematically illustrates an air channel having a tapering cross-section according to the invention;

FIG. 2 illustrates a view taken on line II--II of FIG. 1; and

FIG. 3 illustrates a view of a modified air channel according to the invention.

Referring to FIG. 1, the air-distributing channel 1 which, for example, is of rectangular cross-section and extends lengthwise across the entire width of a loom (not shown) serves to transport conditioned air in the direction of the arrow A. The channel 1 is constructed to distribute the air uniformly over the entire width (region B) of the loom so as to flow out at low speed into the interior of the loom and to obtain optimum conditions (above all, optimum temperatures and humidities) for the processing of a textile article.

As mentioned above, it is necessary that the inflow speed of the air into the channel cross-section C be reduced to some 1/10 to 1/20 of its value before emerging from the channel 1.

In order, in the first place, to ensure equal distribution of the air over the region B, the cross-section of the channel 1 tapers down continuously and linearly. This tapering is obtained by positioning a first wall 2 provided with openings 3 in the region B to extend through the channel diagonally in such a way that the channel cross-section decreases continuously toward the channel end 8.

Referring to FIG. 3, the tapering effect can alternatively be obtained in the same way for about half of the region B. The wall 2 in the remaining half 2a extends substantially parallel to the opposite channel delimitation 4 while a wedge-like filler 5 is positioned under this section 2a to receive the diminution of the channel cross-section.

Referring to FIG. 1, the channel 1 is provided with a series of first turbulence spaces 6, defined by baffle plates 7 positioned at at least approximately uniform spacing, amoutning to between one to four times the quasi-diameter of the channel 1. As shown, the baffles 7 are made as partitions that subdivide the channel but do not, in fact, make the turbulence spaces 6 completely gas-tight to the flow in the lengthwise direction. Instead, the baffles 7 serve to nullify the flow components in the lengthwise direction of the channel 1. The partitions 7, as shown in FIG. 2, are fastened to the side walls of the U-shaped channel 1 by means of screws 9 and by the aid of rivets 10, are fastened to a wall 11 having outflow openings 12. The wall 11 delimits the turbulence zone 6 in the outflow direction. This wall 11 is held, in turn, by screws 13 to the extended side-walls of the channel 1 to serve as a first pressure-reducing or speed-reducing stage. The same screws 13 also serve to attach a third wall 14 having the form of a domed cover and provided with outflow openings 15 to the channel 1.

By a suitable choice of the effective openings cross-section, which for example amounts to about four times that of the wall 2, the uniform speed along the entire length of the channel 1 is substantially reduced by the wall 11, and amounts to about one-fourth of that through the wall 2 or of that at the channel entry. Further, in the turbulence spaces 6, between each two baffle plates 7 and the walls 2 and 11, the kinetic energy of the air flowing through the first wall 2 is nullified to a great extent through turbulent mixing and the pressure is equalized.

The shape given the wall 14 produces another turbulence space 16 between the walls 11 and 14. In this space, the flow energy of the air passing through the wall 11 becomes nullified, and once more equalization of pressure at a low level is obtained. The air, upon passing through the openings 15 in the wall 14, which form the final stage of the air outflow, then becomes distributed as uniformly as possible over a semiplane and in the longitudinal direction at low speed into the space which, for example, is the interior of a loom. The effective opening cross-section of the wall 14 is once more advantageously four times that of wall 11.

The construction shown in FIG. 3 has the advantage, from a fabricating point of view, that the baffle plates 7 disposed behind the wall 2 in the turbulence spaces 6, can be made equal in size in section 2a.

It has proved to be advantageous to make the actual speed-diminishing and pressure diminishing stages of about equal value. This facilitates production of the openings 3, 12, 15 in the individual walls 2, 11 and 14, which walls are usually made of perforated plates.

It is only seldom that commercial perforated plates have the required area ratio between openings and wall parts. It is however, easily possible, by means of two perforated plates, which are offset relative to one another and have a commercially-usual and relatively large number of holes, to produce a desired smaller area-ratio between openings and wall parts by adjusting the plates relative to each other to change the size of the effective openings.

Claims

What is claimed is:

1. An air distributing channel having

an air outlet end defining a longitudinally extending air passage and an inlet to said outlet end of predetermined cross-section;

a first wall disposed within said outlet end of said channel to linearly decrease the cross-sectional area of said air passage in the longitudinal direction and having a plurality of longitudinally spaced apart openings therein for uniformly distributing air from said air passage therethrough, said openings having an effective opening cross-section substantially equal to said cross-section of said inlet;

a second wall disposed longitudinally within said outlet end of said channel in spaced relation to said first wall to define a first turbulence space therebetween, said second wall having a plurality of openings therein for passage of air therethrough;

a plurality of baffles positioned in longitudinally spaced relation within said first turbulence space to nullify the longitudinal flow components of the air passing through said first turbulence space;

a third wall disposed longitudinally of said outlet end of said channel in spaced relation to said second wall to define a second turbulence space therebetween, said third wall having a plurality of openings therein for passage of air therethrough; and

each of said plurality of openings in said second wall and said third wall having a gradually increasing effective opening cross-section relative to said openings in said first wall to effect a reduction in speed in the air passing therethrough.

2. An air distributing channel as set forth in claim 1 wherein said openings in said walls are disposed laterally of said outlet end.

3. An air distributing channel as set forth in claim 1 wherein said baffles are plates disposed as partitions in said first turbulence space.

4. An air distributing channel as set forth in claim 1 wherein the ratio of effective opening cross-section of two adjacent plurality of openings is constant.

5. An air distributing channel as set forth in claim 1 wherein said baffles are spaced apart equally from one to four times the diameter of said channel.

6. An air distributing channel as set forth in claim 1 further having a wedge-shaped filler in a section of said outlet end in opposition to said first wall to linearly decrease said cross-sectional area of said air passage.

7. An air distributing channel as set forth in claim 1 wherein said third wall is in the form of an arch over said channel outlet end.