Fluid reaction surfaces (i.e. – impellers) – Rotor having flow confining or deflecting web – shroud or... – Radially extending web or end plate
Patent
1988-07-13
1989-09-05
Powell, Jr., Everette A.
Fluid reaction surfaces (i.e., impellers)
Rotor having flow confining or deflecting web, shroud or...
Radially extending web or end plate
416223B, F04D 2928, F04D 1718
Patent
active
048633496
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to compressor manufacture and, more particularly, to the impeller of a centrifugal compressor.
PRIOR ART
Known in the prior art is the impeller of a centrifugal compressor comprising a base disc with cylindrical vanes and a cover disc. The web of the base disc has internal and external surfaces whose generatrices are set at different angles to the plane perpendicular to the axis of impeller rotation (see, for example, V.F. Ris. Centrifugal Compression Machines, Moscow/Leningrad, Machinostroenie, 1964, pp. 10, 265).
The base impeller disc is made up of a solid hub and a relatively thin web, the generatrix of the internal web surface being perpendicular to the impeller rotation axis whereas the generatrix of the external surface of the base disc web is set at an angle to the rotation axis.
The base disc is acted upon by the bending moment of the centrifugal forces of the mass of vanes arranged asymmetrically to the disc and by the bending moment of assymmetrically distributed masses of the web, both moments being unidirectional and summarized.
The maximum stresses develop in the section of the disc which is close to the point of disc-to-vane attachment. The same section, apart from having concentrators of stresses arising due to the nature of disc-to-vane attachment, is characterized by heaviest wear and corrosion caused by the flow of gas. All these factors call for high safety margins and the use of materials characterized by high mechanical properties. Therefore, the base discs in the known impeller are made of high-strength steel forgings.
However, the use of such forgings for making the base discs requires a large amount of labour and extensive consumption of metal for blanks. Utilization of rolled stock for making the base discs would cut down considerably the labour and metal content, but the rolled stock has lower mechanical properties and cannot be used in the impellers running at high peripheral speeds, V>180 m/s.
DISCLOSURE OF THE INVENTION
The main object of the present invention is to provide the impeller of a centrifugal compressor wherein, due to a special design of the surfaces of the base disc the latter would feature a low level of stresses at the point of disc-to-vane attachment which would enable the disc to be made of rolled stock.
This problem is solved by providing the impeller of a centrifugal compressor comprising a base disc carrying cylindrical vanes and a cover disc, the web of the base disc having internal and external surfaces whose generatrices are set at different angles to the plane perpendicular to the impeller rotation axis wherein, according to the invention, the angle between the internal surface of the base disc web and the plane perpendicular to the impeller rotation axis is 0.5.degree.-1.degree. larger than the angle between the external surface and the same plane.
The web of the base disc in such an impeller is acted upon by the centrifugal force created by the mass of the disc proper and by the centrifugal force of a part of the mass of vanes. At a selected difference of inclination angles of the generatrices of the internal and external web surfaces its middle section line is set at such an angle to the impeller rotation axis that the effect of the bending moments generated by the centrifugal forces of the mass of web and of a part of the mass of vanes is directed in the opposite way. The total bending moment acting on the web is defined by the difference of these moments, and, consequently, stresses in the dangerous section of said web. The difference of inclination angles (0.5.degree.-1.degree. ) of the generatrices of the external and internal surfaces of the web is selected with a view to ensure minimum stresses in the dangerous section. Thus, the reduced level of stresses in the base disc web enables said base disc to be made from rolled stock.
SUMMARY OF THE DRAWINGS
Now, the invention will be described in detail by way of example with reference to the appended drawings, in which:
FIG. 1 is a lo
REFERENCES:
patent: 892262 (1908-06-01), Jaeger
patent: 1600708 (1926-09-01), Baumann
patent: 1953064 (1934-04-01), Dowson
patent: 2392858 (1946-01-01), McMahan
patent: 2441432 (1948-05-01), McGee
patent: 2799445 (1957-07-01), Hull
patent: 3884595 (1975-05-01), Herrick
Arkhipov Vladimir V.
Raer Gilya A.
Sarantsev Kir B.
Velikanov Gennady F.
Powell Jr. Everette A.
Proizvodstvennoe Obiedinenie "Nevsky Zavod" Imeni V.I. Lenina
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