Fluid sprinkling – spraying – and diffusing – Flow deflecting or rotation controlling means – Fluid rotation inducing means upstream of outlet
Reexamination Certificate
2000-09-15
2003-02-11
Mar, Michael (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Flow deflecting or rotation controlling means
Fluid rotation inducing means upstream of outlet
C239S461000, C239S471000, C239S489000
Reexamination Certificate
active
06517012
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on PCT/EP99/01726 filed on Mar. 17, 1999, which claims priority from German No. 198 11 736.1 filed on Mar. 18, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for varying the swirling movement of a fluid in the swirl chamber of a nozzle, and to a nozzle system for carrying out the method. Such nozzles are used, in particular, in industrial burners, oil burners and systems for washing flue gas and for the spray-drying of foodstuffs.
2. The Prior Art
It is frequently desired to be able to vary the atomization characteristic when atomizing liquids with the aid of swirl nozzles. It is possible to influence the drop size of the spray produced by varying the circumferential speed (swirling movement or swirl component) of the fluid in the swirl chamber. It is important here that the circumferential speed can be varied independently of the liquid throughput, and also that there is no need to undertake mechanical variation at the nozzle. So-called spill-return nozzles (bypass nozzles) constitute a variant. With these nozzles, the liquid is directed tangentially into the swirl chamber and drained off both from the nozzle outlet opening and through a return-flow opening on the middle of the axis. This portion of the liquid throughput is led back again into the liquid reservoir. By varying the return rate, the liquid throughput which is atomized can be kept constant, although the inlet speed of the liquid into the swirl chamber can be varied and thereby adjusted to the swirl intensity and, consequently, to the drop quality. The disadvantage of this solution consists in the necessity of conducting liquid in a circuit. The control range of the spill-return nozzles is bounded below. There is a substantial variation in the jet angle with the desired control range.
Also known are so-called “duplex nozzles” (DE-C 893 133 and U.S. Pat. No. 2,628,867), which are used for atomizing fuels. The nozzles have a swirl chamber into which the fuel is introduced via a plurality of tangential feed channels, and is set rotating about an axis. The nozzles can have different cross-sectional surfaces at the connecting point to the swirl chamber, and the tangential feed channels are connected to separate feed conduits. Incorporated into one of the feed conduits inside the nozzle is a valve which is opened as a function of the pilot pressure present in the other feed conduit, and permits the feed of a larger fuel quantity. The disadvantage of the “duplex nozzles” resides chiefly in the fact that they can implement only a limited possibility of regulation and control which is a function of the pilot pressure present or throughput. U.S. Pat. No. 4,796,815 describes a shower head for a hand-held shower in the case of which the incoming water flow is introduced via two tangential and two radial channels into a swirl chamber, in which a rotatable ball is also located, as well. The water feed in the nozzle head may be varied by means of an adjusting element which can be actuated by hand; either the water inlet into the tangential channels or into the radial channels is covered, or the radial and tangential channels are only partially covered. Different spray patterns are obtained by means of these possible adjustments. The disadvantage of this spray head consists in that for the purpose of generating different spray patterns the adjusting element is arranged inside the swirl chamber, and this varies the inlet surfaces of the tangential and radial channels. This shower head is essentially limited in its application to the sanitary field.
DE 39 36 080 C2 has disclosed a method for varying the circumferential speed component of the swirl flow of a fluid at the outlet from a swirl nozzle having a swirl space with a plurality of tangential feed lines. The entire material flow of the fluid is subdivided into at least two subflows, it being possible to vary the size of at least one subflow. The subflows are fed into the tangential feed conduits of the swirl space. It is disadvantageous that the achievable control range depends on the number of the feed conduits, the result being a rise in the outlay of production for the nozzles with a wide control range. Although rotational symmetry of the flow is achieved, the control range remains narrow. The known nozzles for industrial burners have the disadvantage that the burner output must be kept constant, because otherwise undesired pollutant emissions occur, in particular when the throughput is varied. Remedy is frequently found with a plurality of nozzles, it being possible to achieve optimum conditions only for one operating case. With the known nozzle systems used in spray-drying, a system start-up time of 2 to 3 hours is required when switching products. The powder produced during the start-up time cannot be reused, and must be recycled with considerable outlay. Moreover, it is not possible to influence variations in the product quality and product specification during the operation of production with the aid of the known nozzle systems. The reason for these disadvantages in the known swirl nozzles is their limited and/or inadequate control range.
SUMMARY OF THE INVENTION
It was the object of the invention to create an improved method for varying the swirling movement of a fluid in the swirl chamber of a nozzle which renders it possible to be able to operate a nozzle with a wide control range and, in the process, to achieve as far as possible a comparable drop quality (mean drop diameter and drop distribution), that is to say to create possibilities of being able to control the mean drop diameter in conjunction with a constant volumetric flow, or to keep the drop spectrum constant in conjunction with controlling the volumetric flow. The aim is also to create a suitable nozzle system for the purpose of carrying out the method.
According to the invention, the object is achieved by means of the features specified in claims 1 and 18. Corresponding variant refinements of the proposed method are specified in claims 2 to 17. Advantageous refinements of the nozzle system are the subject matter of claims 19 to 32.
The proposed method for subdividing the subflows over tangential feed conduits which differ in their cross-sectional surfaces at the connecting point to the swirl chamber, it being the case that upon subdivision of the subflows over more than two tangential feed conduits, the cross-sectional surfaces are formed from the sum of the cross-sectional surfaces of the feed conduits which branch off from the respective subflow, and the sums of the cross-sectional surfaces at the connecting point to the swirl chamber of the respective subflows therefore differ, leads to a substantial widening of the control range during operation of the nozzle systems. The possibility of controlling the drop spectrum in conjunction with a constant volumetric flow, or of keeping the drop spectrum constant in conjunction with variation in the volumetric flow is particularly advantageous in the practical use of the nozzles. The term fluid is to be understood within the scope of the present invention as also including mixtures of different fluids with or without solids. The control possibilities, created by the new method, for different nozzle applications result in improved productivity of the production systems, and in a substantial cost reduction. In order to ensure a wide control range, the cross-sectional surfaces should differ by a factor of more than four. According to the invention, the liquid throughput is subdivided into a plurality of subflows which have different cross-sectional surfaces. It is the cross-sectional surfaces at the inlet of the liquid into the swirl chamber (connecting point of the feed conduit and swirl chamber) which are decisive, since the circumferential speed at the periphery of the swirl chamber is fixed at this point. If the aim is a high swirl intensity for a fine drop spectrum, it is necessary to enlarge the subflow applied to the feed conduits which have th
Kohlmann Jürgen
Slowik Günter
Collard & Roe P.C.
Mar Michael
Nguyen Dinh Q.
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