Pumps – One fluid pumped by contact or entrainment with another – Jet
Patent
1990-12-27
1992-02-11
Bertsch, Richard A.
Pumps
One fluid pumped by contact or entrainment with another
Jet
417198, F04F 544
Patent
active
050871757
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to compressor engineering and fluidics and has specific reference to a gas-jet ejector.
2. Description of the Related Art
Known in the art is a gas-jet ejector comprising an inlet chamber, a mixing chamber and a diffuser (TSINTIKHIMNEFTEMASH Abstracts, XM-6 Series, Criogenic and Vacuum Engineering, No 3, I986, Moscow, I. A. Raizman et al "Ejector-Backed Vacuum Pumps With Liquid-Ring Seals of Foreign Make", pp. 1-3) which are series-arranged in alignment with each other. The inlet chamber communicates with the evacuated space and the diffuser, with a vacuum pump. A Laval nozzle communicating with the surroundings is contained inside the inlet chamber in alignment therewith. The Laval nozzle can also be connected to a delivery outlet of a vacuum pump.
The prior art gas-jet ejector creates the prospect of widening the high-vacuum region of the vacuum pump. A vacuum pump with an ultimate pressure of 5-8 kPa is capable of producing a pressure of 1-5 kPa if only one stage of the gas-jet ejector is added to the system. However, the throughput of the prior art gas-jet ejector amounts to only 0.5-0.7 of the throughput of the vacuum pump at the point of connection of the ejector.
SUMMARY OF THE INVENTION
The principal object of the present invention is to provide a gas-jet ejector which is dimensionally proportioned so as to give a throughput which is higher than ever before.
This object is realized by disclosing a gas-jet ejector comprising an inlet chamber connected to an evacuated space and containing an aligned Laval nozzle communicating with the surroundings, a mixing chamber and a diffusor connected to a vacuum pump which are all series-arranged in a direction coinciding with the direction of gas flow and in alignment with each other inside a housing, wherein, according to the invention, the geometry of the critical and outlet sections of the Laval nozzle and of the inlet and outlet sections of the mixing chamber is conducine to an increase in the volumetric flow rate across the outlet section of the diffuser by 1.35 to 1.80 times.
It is expedient that the relationship between the diameter of the critical section of the Laval nozzle and the diameters of the inlet and outlet sections of the mixing chamber and the distance from the outlet section of the Laval nozzle to the inlet section of the mixing chamber is as follows: of the mixing chamber.
An optimal d.sub.1 /d.sub.kp relationship provides for a maximum velocity of the outflow from the Laval nozzle under a pressure of the operating gas corresponding to that of the evacuated gas. If d.sub.1 <1.8 d.sub.kp, the velocity of the operating gas and, consequently, its performance decrease. In case d.sub.1 >2.7 d.sub.kp, the pressure of the operating gas will be less than that of the evacuated gas with the result that wasteful shock waves will occur in the operating gas.
An optimal distance between the outlet section of the Laval nozzle and the inlet section of the mixing chamber locates the point where the flows of operating and evacuated gases begin to mix up. If the Laval nozzle is disposed too far from the mixing chamber (l>4.5 d.sub.kp), the two flows will mix up before entering the mixing chamber and their ratio will impair the performance of the ejector. A too close distance between the Laval nozzle and the mixing chamber (l<2.5 d.sub.kp) will cause the two flows to start mixing up inside the mixing chamber.
An optimal relationship between the diameter, d.sub.2, of the inlet section of the mixing chamber and the diameter, d.sub.kp, of the critical section of the Laval nozzle is conducive to an optimal relationship between the flow rates of the operating and compressed gases. If d.sub.2 <2.8 d.sub.kp, the flow rate of the evacuated gas decreases but if d.sub.2 >5.2 d.sub.kp, the flow rate of the evacuated gas increases with the result that the relative performance of the operating gas decreases.
An optimal relationship between the diameter, d.sub.3, of th
REFERENCES:
patent: Re21416 (1940-04-01), Sargent
patent: 2268656 (1942-01-01), Haltmeier
patent: 3625820 (1971-12-01), Gluntz et al.
patent: 4134547 (1979-01-01), Gamst
V. A. Uspensky, et al. "Get Vacuum Pumps" 1973, Mashinostroenie, (Moscow), cf, p. 114 (FIG. 67).
Tsintikhimneftemash Abstracts, XM-6 Series, Criogenic & Vacuum Engineering, No. 3, 1986, Moscow, I. A. Raizman; et al. "Ejector--Backed Vacuum Pumps with Liquid Ring Seals of Foreign Make", pp. 1-3.
Pirogov Valery A.
Raizman Isak A.
Bertsch Richard A.
Kocharov Michael I.
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