Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
  • B05B1/005—Nozzles or other outlets specially adapted for discharging one or more gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
  • B05B1/14—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means with multiple outlet openings; with strainers in or outside the outlet opening

Definitions

• the present invention refers to a method of reducing the noiGe generation in multi-channel pozzies for blowing devices for a pressurized gas and of providing an increased power concentration and a more concentrated flow.
• the invention also refers to a multi-channel nozzle for o performing the method and comprising a plurality of substantially parallel outlet channels arranged peripherally in the nozzle.
• Nozzles of the above mentioned kind may be connected to various kinds of blowing tools pf conventional design or, alternatively, directly to a distribution conduit.
• the necessary control means for the gas flow o may be provided within the distribution conduit or, alternatively, at a central control unit.
• the blowing devices may be used for instance in turning and milling operation for cleaning by means of pressurized air or other gas.
• the blowing device may be used for cooling, heating, drying, ventilation etc.
• critical flow will normally be obtained if the pressure P is greater than 5-6 bar, i.e. the pressure P will normally be greater than atmospheric pressure. This is due to the fact that the outflowing gas will draw some of the 0 surrounding atmospheric air along with it, which reduces the velocity of the gas blow, whereupon a certain portion of the dynamic pressure of the gas blow will be transformed into static pressure. If the outlet does not communicate with the atmosphere, critical flow will be obtained at a 5 substantially lower pressure than P .
• the temperature T in the through-flpw channel 1 When the pressure ratio is critical, the temperature T in the through-flpw channel 1 will be lowered downstreams of the outlet to a temperature T which, if the gas is air and 0 the isotropic exponential equals 1.4, will be equal 0.833 times T . The density of the air will thereby be reduced by a factor of 0.633.
• the relation between pressures and temperatures is given by the expressions
• a multi-channel nozzle according to figures 2 and 3 will provide a high blowing power at a low air consumption.
• the blowing function and the power concentration will be limited, especially when the nozzle is designed for obtaining higher blowing forces, for instance when the nozzle is used as a so called blow gun.
• a larger number of outlet channels 6 are required than is shown in fig. 3. If the optimum channel spacing is thereby maintained in order to obtain a noiceless and efficient blowing, the air-jet obtained as the sum of the part jets will have unacceptable extension at right angles to the direction of the flow, which means that, apart from the area hit by the jet being unreasonably large, the blowing power per surface unit will be too low.
• the object of the present invention is to provide a multi ⁇ channel nozzle with reduced turbulency and thereby reduced noice generation for the composite flow in the mixing zone outside the mouth.
• the invention further aims at providing a
• Nozzles according to the invention have considerably lower noice levels than admittedly low-noice multi-channel nozzles.
• the noice level may be
• Fig. 1 is a longitudinal section through a conventional tubular nozzle and illustrates the distribution shape of the 5 gas-jet downstreams of a circular outlet.
• Fig. 2 is a longitudinal section through a previously known multi-channel nozzle showing the distribution shape of the gas-jets. _ -.
• Fig. 3 is an end view of the nozzle according to fig. 2.
• Fig. 4 is a longitudinal section through a nozzle according to the invention connected to a blowing tool.
• Fig. 5 is an end view of the nozzle according to fig. 4.
• Fig. 6, 8 and 10 illustrate in section other embodiments of 5 nozzles according to the invention.
• Fig. 7, 9 and 11 are end views of nozzles according to fig.
• a first embodiment of a nozzle according to the invention is illustrated in fig. 4 and 5.
• the nozzle is composed of the outlet portion 20 and the pressure regulating unit 21.
• the two parts may be interconnected by means of a screw connection 22, but the connection may naturally be effected by means of a press fit, welding or gluing.
• the nozzle is intended to be connected to a base part 23.
• the screw connection 22 By means of the screw connection 22 the two nozzle parts 20 and 21 are n n secured against a shoulder 24 and one end surface of the
• the base part 23 may be connected directly to the compressed air conduit or it may constitute a complete blowing tool.
• the base part may then be made of rubber or other elastic material.
• the pressure regulating unit 21 is provided with feeder channels 34 which connect the inner space 25 of the base part 23 with a distribution chamber 27.
• the pressure regulating unit it also provided with an internal reservoar chamber 28 provided with at least one-flow opening 29 through which the two chambers 27 and 28 communicate with each other.
• the reservoar chamber 28 is further made with an opening 30 towards the secondary flow channels 32 of the outlet part said channels 32 being provided inside of the
• the feeder channels 34 in the pressure regulating 21 should have a total through-flow area which is larger than the total through-flow area of the primary flow channels 21 and the secondary flow channels 22.
• the gas discharged from the nozzle via the primary flow channels 31 and the gas discharged through the secondary flow channels 32 will thus be substantially different as concerns the state of the gas.
• the primary flow when discharged from the outlet part 20 will have an outlet pressure P13 which is higher than the outlet pressure P14 of the secondary flow.
• the noice reductions obtained with the nozzle according to the invention are not primarily based upon a regulation of the mass flow amount of the primary flow in comparison with the secondary flow. Tests with considerably differencies in the mass flow of the secondary flow have shown noice reductions only upon the fulfilment of certain other conditions in accordance with the invention, which conditions will be described more closely here below.
• the secondary flow with lower pressure and density cooperates with the primary flow to form a composite flow 8 according to fig. 2
• lower turbulence will be obtained within and around the composite flow. This will cause less noice genaration and lower losses of momentum of the flow.
• the least total area of the trough flow opening 29 should be less than 1.3 times, preferably less than 0.8 times the total area at the secondary flow channels 32, so that the ratio between the total pressures P14 and P13 is less than 0.87, preferably less than 0.73. Further, some part of the reservoar chamber 28 should have a through-flow area which is more than 1.5 times larger, preferably more than 5 times larger than the total area of the through-flow opening 29, so that kinetic energy generated therein will substantially be lost.
• a gas temperature will be obtained which substantially corresponds to the gas temperature within the chamber 27.
• the rate of flow at the outlet of the outlet part 20 obtained through the expansion of the gas will thus be substantially the same for the primary and the secondary flows.
• the secondary flow will receive, apart from a lower total pressure, also a comparatively high dynamic pressure.
• the static pressure at the discharge of the secondary flow from the secondary flow channel 32 will therefore be lower than the static pressure of the primary flow at its outlet from the primary flow channel 31.
• the secondary flow will give a higher degree of co-ejection than the primary flow.
• the primary flow is always composed of two or more part flows.
• the outlet channels 31, of which there will thus always be two or more, may be substantially circular, and the through-flow area have a largest cross sectional measure D which should be less than 2 millimetres, preferably less than 1.3 millimetres, in order to minimize negative effects such as described in connection whith fig. 2.
• the primary flow channels 31 may also with advantage be in the form of two or more slot channel 35 according to fig. 6 and 7.
• the largest slot S should be less than 2 millimetres, preferably less than 1 millimetre.
• the length L of the primary flow channels should be greater than 3 times, but preferably greater than 5 times the cross sectional measure D and the slot measure S, respectively.
• the regulating passage 29 does not necessarily have to communicate directly wiht the chamber 27, but instead communication may be directly with the space 25 - for. instance in accordance with what is shown in fig. 6.
• the secondary flow does not necessarily have to composed of two or several part flow, but may have only one central outlet within the outlet part 20. This is true even for such cases where the secondary flow before the outlet passes through a low pressure chamber 36 connected in series with the reservoar chamber 28, as illustrated in fig. 8.
• a choke device 37 which may have one or several thorugh-flow channels 38.
• the latter should have a least total through-flow area which is less than 1.3 times, preferably less than 0.8 times the total through-flow area of the secondary flow channels 32.
• the embodiment according to fig. 8 and 9 with a low pressure chamber 36 connected in series may advantageously, but not necessarily, be included in a nozzle which has secondary flow channel 32 arranged in two or several circles ( as shown in fig. 10 and 11) which may be independently design to give different gas state of the gas discharged from the outlet part 20.
• the discharged gas may be given three different gas states, whereby is provided a less turbulent outflow for obtaining a lower noice level while retaining the blowing power.
• the nozzle has been tested and has thereby been compared with the conditions in most of the commercially available nozzle types.
• the comparison has included i.e. the noice limiting nozzles design according to Swedish patent application No. 7910235-6 and the US patent specification 3984054.
• a nozzle design according to the invention at equal blowing power at the normally used feeding pressures of 5-9 bar, gives a lower noice level, a higher power concentration, and a higher, or at least equal, efficieny.

Landscapes

• Nozzles (AREA)
• Jet Pumps And Other Pumps (AREA)
• Gas Burners (AREA)
• Details Of Valves (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=20345002

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Cited By (1)

Families Citing this family (11)

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• 1981
  • 1981-11-10 SE SE8106651A patent/SE439441B/sv not_active IP Right Cessation
• 1982
  • 1982-11-08 EP EP19820903360 patent/EP0093144A1/en not_active Withdrawn
  • 1982-11-08 WO PCT/SE1982/000373 patent/WO1983001748A1/en unknown

Non-Patent Citations (1)

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