Pumps – One fluid pumped by contact or entrainment with another – Jet
Patent
1990-08-06
1991-10-08
Bertsch, Richard A.
Pumps
One fluid pumped by contact or entrainment with another
Jet
417196, 417198, 137860, 239432, F04F 548
Patent
active
050550039
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a liquid driven jet pump of the kind which includes a nozzle which is intended to accelerate the drive liquid and which discharges into a pump chamber having an outlet part which is substantially coaxial with the acceleration nozzle, the nozzle orifice area being smaller than the smallest cross-sectional area of the outlet part, an evacuation line which opens out into the pump chamber and which is intended for connection to the space to be evacuated, wherein the outlet part of said pump chamber discharges into a drainage chamber which is substantially coaxial with the outlet part and which has a cross-sectional area which increases abruptly in relation to the outlet part and which, when measured perpendicularly to the axial direction of the outlet part is much larger than the area of the outlet part, and said drainage chamber having a drain orifice which determines the shape of the exiting jet.
Jet pumps that are driven by water under pressure and fitted directly to the tap locations of water delivery pipes are often used in laboratories to pump away gases. In the case of jet pumps of this kind, the water first flows through a nozzle, in which the water is accelerated to a high velocity. The water then enters a pump chamber as a jet which cooperates with a gas inlet line. The jet of water collides with gas molecules in the pump chamber and the molecules are entrained by the water into a diffusor, which is normally in the form of a long pipe whose cross-sectional area increases gradually in the direction of flow. In order to prevent the water jet from exiting too powerfully and causing splashing, it is necessary to increase the cross-sectional area of the diffusor to at least 15 times the area of the nozzle orifice. Since, for reasons of a technical nature concerning flow, this increase in the cross-sectional area of the diffusor must take place very gradually, the diffusor, and therewith also the jet pump, will have unduly long length dimensions. The jet pump will normally block-off the tap location, such as to prevent its use for other purposes.
The object of the invention is to provide a novel and advantageous pump whose length dimension is so small as to create practically no obstruction at the tap location, while still producing a high degree of efficiency, a high final vacuum and a gentle and collected jet.
To this end, it is proposed in accordance with the invention that in the case of a jet pump of the aforedescribed kind, the ratio between the smallest cross-sectional areas of the nozzle and the outlet part respectively and the distance between the nozzle orifice and the drainage chamber are mutually so adapted that the whole of the diffusion process, or at least the most predominant part of said process, takes place with the aid of a multiple of net-like elements which are located in the drainage chamber and through-passed by the liquid; that the smallest cross-sectional are of the outlet part is from 1.4 to 4.8 times as large as the area of the nozzle orifice; and that the area of the drain orifice is from 15 to 45 times larger than the area of the nozzle orifice. A pump of this construction can be given a length of such small dimension and will produce a water jet which is so gentle and so collected and compact, irrespective of whether the evacuation line communicates with the surroundings or is connected to a vessel or some like device to be evacuated, such as to enable the pump to be fitted permanently to, e.g., a conventional tap fitting for laboratory or domestic use, all to no disadvantage.
A particular advantage is afforded when the smallest cross-sectional area of the outlet part is from 2 to 3 times greater than the area of the nozzle orifice, when the total area of the holes in a perforated plate located in the drainage chamber on the upstream side of the net-like elements is from 5 to 15 times larger, when the open mesh area of the net-like elements is 6 to 20 times, preferably 8 to 16 times, larger than the area of the nozzle orifice, and when the drai
REFERENCES:
patent: 2741997 (1956-04-01), Parker
patent: 3529421 (1970-09-01), Neeley
patent: 3902671 (1975-09-01), Symmons
patent: 4014961 (1977-03-01), Popov
patent: 4487553 (1984-12-01), Nagata
patent: 4637552 (1987-01-01), Finkbeiner et al.
Bertsch Richard A.
Kocharov Michael I.
Teknovia AB
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