Gas and liquid contact apparatus – Contact devices – Injector type
Reexamination Certificate
1999-08-09
2001-05-01
Bushey, C. Scott (Department: 1724)
Gas and liquid contact apparatus
Contact devices
Injector type
Reexamination Certificate
active
06224042
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention pertains to the field of jet technology, primarily to liquidgas ejectors, which can be used in the petrochemical industry for producing a vacuum, for example in vacuum rectifying columns.
A liquid-gas ejector is known, which comprises an active nozzle, a mixing chamber, a diffuser and a receiving chamber. The length of the ejector's mixing chamber represents 7 times the diameter of the outlet cross-section of the ejector's nozzle (see, for example, book of Sokolov E. Y. and Zinger N. M., Jet apparatuses, M., Energy 1970, page 211).
Jet apparatuses of this type possess quite high capacity. At the same time they have a relatively low efficiency factor. This is why their range of application is limited.
The starting point for the present invention is a liquid-gas jet ejector comprising a nozzle and a mixing chamber, wherein the ratio of the length of a throat of the mixing chamber to the diameter of the throat is 11.5 (see book of Sokolov E. Y. and Zinger N. M., Jet apparatuses, M., Energy 1970, page 200-201).
Such apparatuses are widely used in power engineering as air-ejecting devices of condensing units and in vacuum water deaeration plants. The apparatuses allow evacuation of an air-vapor mixture from a condenser. They are able to boost the pressure of the evacuated medium from 0.02 . . . 0.06 atm(abs) up to the atmospheric pressure. However, these ejectors also have a relatively low efficiency factor due to nonoptimal geometry of the ejector's flow-through channel, which results in big hydraulic energy losses.
SUMMARY OF THE INVENTION
The objective of the present invention is to increase the efficiency factor of a liquid-gas ejector due to optimization of the flow regime in a mixing chamber of the ejector.
The stated objective is achieved as follows: a liquid-gas ejector having a nozzle and a mixing chamber has a mixing chamber whose length ranges from 200 cm to 1400 cm.
Experiments on the operation of liquid-gas ejectors were conducted on a bench in a wide range of the ejectors' capacities. The investigated ejectors had mixing chambers of different diameters and their characteristic dimension (the ratio of the surface area of the minimal cross-section of the mixing chamber to the surface area of the minimal cross-section of the nozzle) ranged from 5 to 250 (the mentioned book of Sokolov E. Y. & Zinger N. M., page 205, teaches that the like characteristic dimension be from 5 to 30). During the research it was discovered that the absolute length of the mixing chamber is one of the most important geometric parameters of a liquid-gas ejector. It also became clear that pressure of a liquid medium at the nozzle's inlet is the determinant parameter affecting the length of the mixing chamber. Therefore the experiments were conducted within a wide range of the motive liquid pressure. The pressure varied from 6 to 240 atm (abs), the mass coefficient of injection ranged from 10
−3
% to 14%. It was discovered, that within the above indicated range of the motive liquid pressure mixing of the liquid and evacuated gaseous mediums can not be completed in the mixing chamber if the length of the mixing chamber is smaller than 200 cm. A heterogeneous gas-liquid flow discharged from such mixing chambers is evidence of the imperfect mixing of the mediums. At the same time, expansion of the mixing chamber's length beyond 1400 cm does not improve the ejector's performance and causes only an increase in specific consumption of materials. The distance between the outlet cross-section of the nozzle and the outlet cross-section of the mixing chamber was interpreted as the length of the mixing chamber during the tests. It was also discovered, that the availability or absence of a diffuser at the outlet of the mixing chamber does not have an influence on the mixing chambers optimal length. The mixing chamber whose length is within the discovered optimal range provides complete mixing of liquid and evacuated gaseous mediums and a uniform gas-liquid flow in its outlet section. Under such conditions a pressure jump is generated in the zone of the outlet section of the mixing chamber and a liquid flow containing small gas bubbles is formed at the mixing chamber's outlet
Thus the stated objective has been achieved: a complete mixing of liquid and gaseous mediums takes place in the mixing chamber, i.e. in the part of ejector's flow-through channel, which is specially assigned for this function. Such provides a reduction in energy losses and an increase in efficiency of a liquid-gas ejector.
REFERENCES:
patent: 992081 (1911-05-01), Tait
patent: 1117626 (1914-11-01), Bassler
patent: 2382391 (1945-08-01), Berman
patent: 3707067 (1972-12-01), Dietrick
patent: 5628623 (1997-05-01), Skaggs
patent: 985462 (1982-12-01), None
patent: 1483106 (1989-05-01), None
patent: 1755714 (1992-08-01), None
Sokolov E.Y., “Jet apparatuses” book, 1970, USSR, Moscow, “Energy” Publishing house, pp. 200-201, 211.
Bushey C. Scott
Oathout Mark A.
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