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Title:
A SILENCED BLOWING NOZZLE
Document Type and Number:
WIPO Patent Application WO/2017/217916
Kind Code:
A1
Abstract:
The invention relates to a silenced blowing nozzle for blowing of a gas medium under overpressure, in particular air. The blowing nozzle includes a central part (11) with a primary nozzle means (13) which includes at least one Laval nozzle (14) and has at least one primary discharge opening (15) such that the primary discharge opening (s) (15) will generate a core stream of gas with supersonic velocity. The central part (11) is surrounded by a more peripheral part (12) containing a plurality of secondary nozzles (16a, 16b, 16c) with respective secondary discharge openings (17a, 17b, 17c). These are spaced from another and from said primary discharge opening(s) (15). According to the invention each secondary discharge opening (17a, 17b, 17c) is arranged to generate a gas stream that is divergent from the axis of the core stream.

Inventors:
TIBELL RASMUS (SE)
Application Number:
PCT/SE2017/050616
Publication Date:
December 21, 2017
Filing Date:
June 09, 2017
Export Citation:
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Assignee:
SILVENT AB (SE)
International Classes:
B05B1/14; B05B1/34
Domestic Patent References:
WO1983001748A11983-05-26
Foreign References:
US6415991B12002-07-09
US4050632A1977-09-27
CN104069966A2014-10-01
CN104069962A2014-10-01
CN104069961A2014-10-01
CN104069960A2014-10-01
US6241510B12001-06-05
Other References:
See also references of EP 3471890A4
Attorney, Agent or Firm:
HYNELL PATENTTJÄNST AB (SE)
Download PDF:
Claims:
A silenced blowing nozzle for blowing of a gas medium under

overpressure, in particular air, which blowing nozzle includes a central part (1 , 1 1 ) with a primary nozzle means (3, 13) which includes at least one Laval nozzle (4, 14) and has at least one primary discharge opening (5, 15) such that the primary discharge opening (s) (5, 15) will generate a concentrated core stream (A) of gas with supersonic velocity, which central part (1 , 1 1 ) is surrounded by a more peripheral part (2, 12) containing a plurality of secondary nozzles (6, 16a, 16b, 16c) with

respective secondary discharge openings (7, 17a, 17b, 17c) spaced from another and from said primary discharge opening(s) (5, 15),

characterized in that each secondary nozzle (6, 16a, 16b, 16c) has an orientation such that each secondary discharge opening (7, 17a, 17b, 17c) generates a gas stream that is divergent from the axis (C) of the core stream, which divergent gas stream has an angle (a) relative to the axis (C) of the core stream in the range of 1 ,5 - 8°, and wherein at least some of the secondary nozzles (6, 16a, 16b, 16c) are Laval nozzles

A silenced blowing nozzle according to claim 1 , wherein said divergent gas stream has an angle (a) relative to the axis (C) of the core stream in the range of 2,5 - 5°.

A silenced blowing nozzle according to claim 1 or 2, wherein all said secondary nozzles (6, 16a, 16b, 16c) are Laval nozzles.

A silenced blowing nozzle according to any one of claims 1 -3, wherein said secondary nozzles (6, 6c, 16a, 16b, 16c) are located along at least one circle, which circle is concentric with the axis (C) of the core stream.

A silenced blowing nozzle according to claim 4, wherein the number of secondary nozzles (6) is 4 - 8, preferably 6.

6. A silenced blowing nozzle according to claim 4 or 5, wherein said secondary nozzles (6, 16a, 16b, 16c) are divided into at least two groups, wherein the nozzles in each group has a different localisation from the nozzles in the other group(s) with regards to the axial position of the discharge opening (7, 17a, 17b, 17c) and/or with regards to the diameter of the circle along which the nozzles in the group are located.

7. A silenced blowing nozzle according to claim 6, wherein the number of nozzles in each group is 2 - 32, preferably 4 - 16, most preferably 6.

8. A silenced blowing nozzle according to claim 6 or 7, wherein the number of nozzles (16a, 16b) in two groups arranged along the same circle is equal. 9. A silenced blowing nozzle according to any one of claims 1 -8, wherein a circular front ring (8, 18) with a front edge (9, 19) surrounds the primary nozzle means (3, 13), and wherein each discharge opening (5, 15, 7, 17a, 17b, 17c) is located ahead of said front edge (9, 19) as seen in the flow direction through the primary nozzle means (3, 13).

10. A silenced blowing nozzle according to claim 9, wherein a relief channel means (10) is arranged within the blowing nozzle, which relief channel means (10) communicates with the space formed between the front edge (9, 19) and the primary discharge opening (5, 15) and communicates with the surrounding at a location ahead of the front ring (8, 18) as seen in the flow direction through the primary nozzle means.

Description:
A SILENCED BLOWING NOZZLE

FIELD OF INVENTION

The present invention relates in a first aspect to a silenced blowing nozzle for blowing of a gas medium under overpressure, in particular air, which blowing nozzle includes a central part with a primary nozzle means which includes at least one Laval nozzle and has at least one primary discharge opening such that the discharge opening (s) will generate a core stream of gas with supersonic velocity, which central part is surrounded by a more peripheral part containing a plurality of secondary nozzles with respective secondary discharge openings spaced from another and from the primary discharge opening(s)

In the present application terms like axial, radial and circle has the axis of the core stream, i.e. the centre line of the blowing nozzle, as the reference, if not explicitly defined otherwise.

BACKGROUND OF INVENTION

Pressure air is used in many applications within the industry e. g. for clean blowing, cooling, separation, drying or transporting. Blowing with pressure air is normally entailed with a high noise level. Environment demands are continuously increasing. With respect to work environment, lower sound level and energy saving are frequently required, or at least desired.

Therefore it has been an endeavour to attain blowing nozzles that generate as low sound as possible for a given blowing force, so called "silent type nozzles". Examples of this type of nozzle are tapered slot nozzle of type Silvent ® 51 1 and 512, cupped hole nozzles of type Silvent ® 208 and 209 and blowing nozzles with flat ends, type Silvent ® 701 -720. These blowing nozzles are used for low and moderate blowing forces and blowing distances. So called "large blowers" are used when large blowing forces are required at long distances. Belonging to this group are aggregates consisting of a large number of co-operating hole nozzles, which belong to the Silvent ® 1 100- and 1200-series. These tools are used for instance for application in steel plants, paper mills and foundries for cleaning, cooling drying etc.

In certain cases within the pulp and paper industry, blowing nozzles with even higher air flows are used, which generate extremely high noise levels due to the expansion of the air stream after it has left the nozzle. The operator can be subject to a level of approx.1 15 dB(A), and for other personnel in the vicinity of the discharge it is not unusual with values in the range of 100-1 10 dB(A). As the nozzle is often required for sudden interruptions in production at the factory, e.g. when a paper web goes out of line, high requirements are placed on the personnel for immediate action. Many times one simply does not have time to put on hearing protection, which in unfortunate cases can imply permanent hearing damage after only a few seconds of exposure time.

The need to increase the blowing forces and to reduce the noise level is addressed in US 6 414 991 , the disclosure of which hereby is incorporated in the present application by reference. US 6 415 991 discloses a silenced blowing nozzle which has a central part with at least one first discharge opening generating a core stream of gas with supersonic velocity. The central part is surrounded by a more peripheral part having a number of second discharge openings generating a gas flow of lower velocity than the core stream, which gas stream surrounds the core stream and has the same direction as the core stream. The discharge openings may have circular shape or be shaped as slits.

Similar blowing nozzles are disclosed in CN 104069962 and CN 104069966. Although a silenced blowing nozzle of the kind disclosed in US 6 414 991 represents significant improvements with regards to increasing the blowing force and reducing the noise level, it still remains a need for further improvement in these respects. There is also a demand for attaining a more concentrated stream from the blowing nozzle due to a need for better precision of the gas stream. The object of the present invention is to meet these demands.

SUMMARY OF INVENTION

The object of the present invention is achieved in that a silenced blowing nozzle of the kind specified in the preamble of claim 1 includes the specific features specified in the characterizing portion of the claim. Thus, each secondary discharge opening is arranged to generate a gas stream that is divergent from the centre line of the core stream.

By the divergent direction of the peripheral gas stream it has been shown that the concentration of the central beam becomes more accentuated in comparison with peripheral gas streams that are parallel to the core steam. The propagation pattern of the core stream has been simulated through computer flow program and analysed, which indicates such an increased concentration of the core stream. This has also been confirmed by laboratory tests. A more concentrated core stream results in lower energy consumption, since a concentrated stream results in a better blowing precision. This leads to shorter blowing time and thus less energy consumption. The invented blowing nozzle also decreases the turbulence, which means a lower noise level. Thereby less energy gets wasted in sound generation which leads to a higher blowing force. A higher blowing force in relation to the gas consumption means that the efficiency of the nozzle is increased.

According to a preferred embodiment, the divergent gas stream has an angle relative to the axis of the core stream in the range of 1 ,5 - 8°.

The simulation and the laboratory tests mentioned next above have shown that the concentration of the core stream in relation to the blowing distance is most significant when the deviation is in this range. In particular a deviation angle within the range of 2,5 - 5° has been shown to be optimal in most applications.

According to a further preferred embodiment at least some of the secondary nozzles are Laval nozzles.

This further contributes to attain a core stream that is as concentrated as possible. The Laval nozzles allow the peripheral streams to have supersonic speed, although lower than the supersonic speed of the core stream. This further decreases turbulence, and thereby leads to a lower sound level. Preferably all of them are Laval nozzles since it provides an optimal effect in this respect.

According to a further preferred embodiment, the secondary nozzles are located along at least one circle, which circle is concentric with the axis of the core stream.

A circular arrangement is optimal with regards to the effects achieved with the invented blowing nozzle regarding concentration, sound level and energy consumption. Preferably the nozzles are evenly distributed along the circle.

According to a preferred embodiment, when all the secondary nozzles are arranged along one circle, the number of secondary nozzles is 4 - 8.

The advantageous effects discussed above will be more significant the larger the number of secondary nozzles along the circle is. A large number of nozzles, however adds to the complexity of the blowing nozzle. The specified range is an adequate balance between these considerations. A number of 6 secondary nozzles in most cases is optimal in this respect.

According to a further preferred embodiment, the secondary nozzles are divided into at least two groups, wherein the nozzles in each group have a different localisation from the nozzles in the other group (s) with regards to the axial position of the discharge opening and/or with regards to the diameter of the circle along which the nozzles in the group are located.

Arranging the nozzles in e.g. two groups where the axial positions of the discharge openings are different between two groups makes it possible to obtain space for a larger number of secondary nozzles along one and the same circle and increase the concentration of the core stream. Preferably the secondary nozzles along the circle are arranged such that every second secondary nozzle belongs to one group, and the other secondary nozzles belong to the other group.

There may be applications where it is advantageous for increasing the concentration of the core stream and decrease the turbulence for a given flow rate to arrange a first group of secondary nozzles along a first circle and a second group along another circle concentric with the first.

According to a further preferred embodiment the number of nozzles in each group is 2 - 32.

The optimal number of nozzles in a group follows similar considerations as mentioned above regarding the number of nozzles where there is only one group. It has also to be taken into account the constellation of the groups; whether there are two different groups arranged along different circles, which may give reason to have a relatively large number for the radially outer group or whether two groups are located along one and the same circle, which may give reason to have a relatively small number of nozzles in these groups. In most cases an optimal number will be found within the specified range, in particular within the range 4 - 16. A number of 6 nozzles in each group is generally found to be optimal.

According to a further preferred embodiment, the numbers of nozzles in two groups arranged along the same circle are equal.

This further harmonizes the flow pattern with a minimum of turbulence and therefore leads to a good concentration and low noise level.

According to a further preferred embodiment, a circular front ring with a front edge surrounds the primary nozzle means, and each discharge opening is located ahead of said front edge as seen in the flow direction through the primary nozzle means.

By this front ring it is assured that the discharge openings of the secondary nozzles are not destroyed due to wear. Deterioration of the edges of the outlet openings would give rise to increased turbulence. The ring thus maintains the low turbulence achieved with the invented blowing nozzle. Since increased turbulence also decreases the concentration of the core stream, the ring is also important for maintaining a concentrated core stream.

A further advantage with this ring is that it contributes to that the blowing nozzle meets the requirement of OSHA (Occupational Safety and Health Administration), a US organization enforcing regulations for workers safety. In its framework of rules there are rulings regarding maximal pressure in case the discharge opening becomes closed by obstruction. If there is a risk that the discharge can be completely obstructed, the pressure may not exceed 30 psi (210 kPa) according to OSHA 29CFR 1910.242(b). With the front ring, the blowing nozzle will meet the requirements of OSHA. The air velocity pressure has been measured to be far below 210 kPa.

According to a further preferred embodiment a relief channel means is arranged within the blowing nozzle, which relief channel means communicates with the space formed between the front edge and the primary discharge opening and communicates with the surrounding at a location ahead of the front ring as seen in the flow direction through the primary nozzle means.

The channel means in an advantageous way allows the gas to escape in the backwards direction in case the front ring would be completely obstructed. The channel means is a simple and advantageous way to meet the OSHA

requirements mentioned above.

The above described preferred embodiments of the invention are set out in the dependent claims. It is to be understood that further preferred embodiments may be constituted by any possible combination of features of the described preferred embodiments and by any possible combination of features in these with features described in the description of examples below.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a section along the axis of a blowing nozzle according to a first example of the invention.

Fig. 2 is a side view of the blowing nozzle in fig. 1.

Fig. 3 is a side view of the blowing nozzle of fig. 1 as seen from another angular position than that of fig. 2.

Fig. 4 is a perspective view of a blowing nozzle according to a second example of the invention.

Figs. 5-7 are diagrams illustrating various examples of the positioning of the secondary nozzles.

Fig. 8 illustrates the shape of the core stream of a blowing nozzle according to the invention.

DESCRIPTION OF EXAMPLES

Figs 1 to 3 illustrate a first example of a silenced blowing nozzle according to the invention, where fig 1 is a longitudinal section through the centre of the blowing nozzle. The blowing nozzle has a main housing 20 with an inlet 21 for pressurized gas such as air. The main housing 20 has an internal thread 22 adjacent the inlet 21 for connection with a pipe connected to a source of pressurized air. The blowing nozzle is arranged to generate a core stream with a centre axis C.

The blowing nozzle at its outlet portion has a central part 1 in which a primary nozzle means 3 is arranged. The primary nozzle means 3 consists in the illustrated example of one Laval nozzle 4 with a discharge opening 5, which generates the core stream with the axis C. It is to be understood that the core stream alternatively could be generated by a plurality of Laval nozzles.

The central part is surrounded by a peripheral part 2, which has six secondary nozzles 6 with a respective discharge opening 7. Each of the secondary nozzles 6 is a Laval nozzle. The direction of each secondary nozzle has an orientation such that the air stream generated therethrough has a direction that is divergent from the direction of the axis C of the core stream. The direction thus forms an angle a with the axis C. In the illustrated example a is 4,75°.

The blowing nozzle is designed such that a circular front ring 8 with a front edge 9 is formed. The front ring 8 projects in the flow direction beyond the primary discharge opening 5 and the secondary discharge openings 7. The front edge 9 thereof thus forms the very downstream end of the blowing nozzle. Fig. 2 is a first side view of the blowing nozzle, and fig. 3 is a second side view thereof, which second side view is turned 60° in relation to that of fig. 2.

Fig. 4 illustrates a second example of the blowing nozzle. In this example the secondary nozzles are divided into three groups. Also in this example the primary nozzle means 13 has one single Laval nozzle 14 with a discharge opening. 15. In the figure the nozzle and its discharge opening are located behind the ring 18 and thus not visible. The reference numbers for these are within brackets and the broken reference line points towards the location.

The peripheral part 12 of the blowing nozzle has a number of secondary nozzles 16a, 16b, 16c. The secondary nozzles are divided into three groups, wherein a first group has six nozzles 16a with a respective discharge opening 17a. A second group likewise consists of six nozzles 16b with a respective discharge opening 17b. A third group also consisting of six nozzles 16c with discharge openings are arranged radially innermost around the primary nozzle 14. All the secondary nozzles in the first and second groups 16a, 16b are arranged at substantially the same radius from the centre line of the blowing nozzle, i.e. along a common circle. This circle has larger diameter than that of the circle along which the third group of nozzles 16c is arranged. And each of the secondary nozzles is a Laval nozzle. All the secondary nozzles are oriented such that they generate an air stream that diverges about 5° from the centre line of the blowing nozzle.

The first group of secondary nozzles 16a are axially longer than the second group of secondary nozzles 16b, and the discharge opening 17a of each nozzle 16a in the first group are located downstream of the discharge openings 17b of each nozzle 16b in the second group.

Also this blowing nozzle is designed such that a circular front ring 18 with a front edge 19 is formed. The front ring 18 projects in the flow direction beyond the primary discharge opening 15 and the secondary discharge openings 17a, 17b, 17c The front edge 19 thereof thus forms the very downstream end of the blowing nozzle.

Fig. 4 also illustrates a channel means 10 formed by the space between the inner secondary nozzles 16c. The channel means 10 in this example thus has six channels. Should the ring 19 be completely covered by an object, the gas streams from the primary nozzle and the inner secondary nozzles 16c will reflect against the obstacle, return through the intermediate channels and escape to the surrounding at the rear end 19b of the ring 18. Similar channels 10 are present also in the example illustrated in figs 1 -3.

Many variations of arranging the secondary nozzles in different groups are possible within the scope of the claimed blowing nozzle. A few such examples are illustrated in the diagrams in figs 5 to 7. Each diagram shows the positions of the nozzles in a plane perpendicular to the centre axis of the blowing nozzle.

In fig. 5 there are six inner secondary nozzles 16c arranged along a circle and twelve outer secondary nozzles arranged along a common circle. Of these every second nozzle 16a, indicated with a cross, has its discharge opening in a common first plane perpendicular to the centre axis of the blowing nozzle. The other nozzles 16b have their discharge openings in a second common plane

perpendicular to the centre axis. The first plane is located closer to the

downstream end of the blowing nozzle the second plane. This corresponds with the example depicted in fig. 4.

In fig. 6 there are twenty-four secondary nozzles arranged in three groups. Along an inner circle there are six secondary nozzles 26c, and along an outer circle are twelve secondary nozzles 26b. Along an intermediate circle are six secondary nozzles 26a.

In fig 7 there are thirty-six secondary nozzles arranged in four groups. Along an inner circle there are six secondary nozzles 36c. Along an intermediate circle there are two groups of secondary nozzles 36a, 36b, with six nozzles in each group, and arranged similar to those of fig. 5. Along an outer circle are eighteen secondary nozzles 36d arranged with their discharge openings in a plane common to the discharge openings of nozzles 36a.

It is, within the scope of the invention further possible to include secondary nozzles that are not Laval nozzles, e. g. shaped as slits.

It is also to be understood that the cross flow areas of all the secondary nozzles are not necessarily equal.

Fig. 8 in a side view illustrates the shape of the core stream A obtained with a blowing nozzle according to the invention. The core stream of a blowing nozzle according to prior art is indicated as B. As can be seen, the core stream is much more concentrated with a blowing nozzle according to the invention.