Spiral housing for a turbomachine

Details Spiral housing for a turbomachine Spiral housing for a turbomachine

1995-06-12

1997-04-29

Larson, James

Rotary kinetic fluid motors or pumps

Working fluid passage or distributing means associated with...

Casing having tangential inlet or outlet

4152121, F04D 2942

Patent

active

056242298

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention concerns a spiral housing for a turbomachine. The upstream radial or semi-axial annular disk space of the disk diffuser in the event of a compressor, or the intake space of a turbine, is asymmetrical to the spiral cross-sections. The base-circle diameter D.sub.z is approximately constant.
An intake spiral for a radial turbine with an upstream separator is known from U.S. Pat. No. 3,380,711 (FIG. 3). The spiral housing exhibits only one spiral with a constant inner or base-circle diameter and with a constant outer radius in the event of an axially adapted flow cross-section. No decrease in the outer radius at the transition to a circular cross-section in the vicinity of the tongues is evident.
The spiral in the art known from pages 211 and 224 of Ventilatoren by Bruno Eck, Berlin etc., Springer, 5th edition, 1992 has a rectangular or circular cross-section. It merges upon arriving at the commencement of the tongue in the case of a compressor into an adjacent diffuser, usually a conical diffuser. Base-circle radius r.sub.z is usually approximately constant and equal to the outer radius r.sub.s of the annular disk space accommodated in the spiral. An ideal flow can simultaneously be maintained in the vicinity of the spiral tongue. The circular cross-section simultaneously results in relatively large radii r.sub.A max, which contribute in particular to high manufacturing costs when the spiral is surrounded at high pressures by a cylindrical outer housing. An outer housing must, due to the r.sub.A max, have a large inside diameter.
To decrease the r.sub.A max while maintaining a prescribed annular disk-space outer radius r.sub.s, the base-circle radius r.sub.z is often hauled inward (r.sub.z <r.sub.s) in the prior art illustrated in FIG. 2 on page 213 of the Eck book while outer radius r.sub.A is left constant.
Such an approach, however, results in unfavorable flow conditions in the spiral, because the flow is decelerated in accordance with the law of angular momentum as the radius increases up to the end of the annular disk space in a compressor and must be re-accelerated in accordance with that law at the adjacent transition to smaller radii.
Since, however, the center of the circle constituted by the radius r.sub.k of curvature will no longer be on the axis A of the impeller and since the curvature of the inner contour is often inconstant, complex flow conditions contrary to the law of angular momentum will also occur in the vicinity of tongue Z. Given an axial spiral with a constant base-circle radius r.sub.z and a constant outer radius r.sub.A at the circumference in accordance with the art illustrated in FIG. 3 on page 214 of the Eck book, the law of angular momentum can be complied with along much of the spiral's centrical angle .phi. by adapting the axial length L of the spiral cross-section to the volumetric flow as it increases along the circumference. There will, however, still be complex conditions in the vicinity of the tongue.


SUMMARY OF THE INVENTION

The object of the present invention is accordingly a spiral housing that will ensure more efficient flow, that will be less expensive to manufacture, and that will lack the aforesaid drawbacks.
The base-circle diameter is accordingly approximately constant. The spiral cross-section of the region II-III adjacent to tongue region I-II along the circumference is approximately circular and, once it attains a prescribed outside diameter D.sub.A =D.sub.G, increases only axially.
The conditions for creating a channel vortex generated by asymmetric flow into the spiral will be ideal when the circular area with radius R.sub.G =(r.sub.G -r.sub.Z)/2 is separated as the spiral continues into two semicircular areas (R.sub.G 2.multidot..pi.)/2 perpendicular to the axis with a rectangular area 2R.sub.g .multidot.L between them, whereby the rectangular area constantly increases axially in relation to L as centric angle .phi. increases while the semicircular areas (R.sub.G 2.multidot..pi.)/2 and the radial exte

REFERENCES:
patent: 3365122 (1968-01-01), Hajec et al.
patent: 3380711 (1968-04-01), Blattner et al.
patent: 3407995 (1968-10-01), Kinsworthy
patent: 5069599 (1991-12-01), Carretta
patent: 5474422 (1995-12-01), Sullivan
Kosmowski et al, "Turbomaschinen", Heidelberg, pp. 132-133 Dec. 1989.

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