Fluid sprinkling – spraying – and diffusing – Combining of separately supplied fluids – At or beyond outlet
Patent
1983-07-06
1986-06-03
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Combining of separately supplied fluids
At or beyond outlet
2394255, B05B 706
Patent
active
045925097
DESCRIPTION:
BRIEF SUMMARY
The invention of this application is disclosed in International Application PCT/SE No. 82/00388, filed Nov. 17, 1982, in which applicant claims priority under 35 USC 119.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a blowing device for compressed air or the like having at least one feed channel which is connectable to a source of compressed air and an outlet which is shaped to impart to the compressed air a jet in the form of a ring, or part of a ring, under adiabatic expansion, and at least one communication channel adapted to connect the inside of the jet with the atmosphere.
2. Description of the Prior Art
The most common way to use compressed air for blowing purposes is by supplying the compressed air to a nozzle with one or several substantially circular outlet channels. The velocity of the discharge of the air is dependent upon the pressure upstream of the outlet channels and the pressure situation downstream of the same. If this pressure relation corresponds with the so-called critical pressure relation, the velocity of the discharge will be equal to the sound velocity. In most industries utilizing compressed air, the pressure normally present in the air supply network will be such, that the velocity of discharge, for example for cleaning purposes, using nozzles of the kind mentioned will be essentially equal to the sound velocity. Thus in most cases, the pressure relation will be equal to the critical pressure relation, i.e. 0.528.
When air is flowing out from an outlet in this manner under substantially adiabatic expansion there will occur a conically shaped core jet and outside of this a mixing zone where the air jet, due to transmission of movement to the ambient air in the form of expansion, will diverge and bring ambient air along with it in its movement. Thus, the air jet will increase in mass but will loose velocity. The loss of velocity entails that the dynamic pressure of the air jet will be partly transformed into static pressure. This pressure, added to the atmospheric pressure, comprises the counter pressure to which the pressure ratio is related.
The supply pressure at which critical flow occurs will thus be determined by the degree of co-ejection. From the point of view of co-ejection, among other things, it is an advantage to divide a given mass flow into several smaller part flows, so called multi-channel nozzles. This will provide, related to the mass flow amount, a considerably larger contact surface between outflowing air and ambient air, since the contact surface "KA" between outgoing flow and ambient air is directly proportional to the total circumference, O.sub.out, i.e. KA.dbd.O.sub.out .times.K. K is a constant which is determined, among other things, by the angle at which the air jet diverges, i.e. by the conditions of turbulance, and by the distance between the nozzle outlet and the work piece to which the air jet is directed.
For instance, in the case of 10 outlet channels with a diameter of 1 mm, O.sub.out =31.4 mm, whereas, for the same outlet area A.sub.out using 1 outlet channel, O.sub.out is less than 10 mm. Thus, the contact number KT, which may be expressed as O.sub.out /A.sub.out, will be 4 mm/mm.sup.2 and about 1.24 mm/mm.sup.2, respectively. One drawback of multi-channel nozzles is the manufacturing of the long and narrow channel. An increased O.sub.out, while maintaining the same A.sub.out, to for instance 2 times 31.4 mm, i.e. to an increased KT of 8 mm/mm.sup.2, will necessitate 40 channels with a diameter of 0.5 mm. Such a nozzle outlet, which gives a lower noise level, is difficult to implement in view of the manufacturing.
At the normal supply pressures of 6-8 bar there is obtained at larger nozzle outlets, preferably larger than 40 mm.sup.2, a counter pressure which is lower than 0.528 times the supply pressure.
Within an outgoing air jet there will occur downstreams of the outlet local differences in velocity, pressure and density. The locally and periodically varying pressure differences will be reduced at a
REFERENCES:
patent: 3477112 (1969-11-01), Yerkins
patent: 3615053 (1971-10-01), Pease et al.
patent: 3770204 (1973-11-01), Schuster
patent: 4195780 (1980-04-01), Inglis
patent: 4311404 (1982-01-01), Kodera
Kashnikow Andres
Malpede Scott
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