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Composite francis turbine wheel

Time:2018-01-09 17:11Turbochargers information Click:

turbine Whee Francis composite

Composite francis turbine wheel

Composite francis turbine wheel


F03B3/02 - with radial flow at high-pressure side and axial flow at low-pressure side of rotors, e.g. Francis turbines

FIELD: engines and pumps.

SUBSTANCE: proposed Francis turbine wheel comprises at least two wheel segments 12, 14 that can be jointed together along their opposed surface sections 16, 16a, 18, 18a to make composite wheel with top rim 28, bottom rim 30 and multiple vanes 32 running between said rims and secured thereto. Said opposed surface sections 16, 16a, 18, 18a are arranged solely along top and bottom rim segments. Note that opposed surface sections 16, 16a, 18, 18a of wheel segments 12, 14 are arranged between apart from adjacent vanes. Proposed wheel has central axis. Top rim has central round bore. Opposed surface sections 16, 16a of top rim, if seen from above, run from central bore, radially offset from central axis.

EFFECT: higher reliability and longer life.

7 cl, 2 dwg

 

The present invention relates to a work wheels for Francis turbines and, in particular, to composite the impeller to the turbine Francis.

Impellers for Francis turbines contain upper rim, a bottom rim and a multitude of turbine blades passing between the upper rim and lower rim. An example of such impeller disclosed in the publication DE 648174. In the manufacture of blades usually are fixed on the upper rim and the lower rim by welding. When the diameter exceeds 5 meters, for example, it is known separation of the impeller of the turbine in two segments, separated from each other by a plane passing along the axis of the impeller so as to provide the transportation of the impeller from the manufacturing site to the construction site of the dam. This radial plane cuts through the upper rim, a lower rim and some areas of blades.

At the site of the dam split segments of the impeller are collected by execution of welded joints in the upper rim, a lower rim and cut the blades. Welding blades requires great care due to the loads that should be applied to the blades during operation of the turbine. These welded connections typically perform filler metal-based material CA-6NM, which is an alloy of iron-chromium-Nickel-molybdenum, harden eleswarapu heat treatment. During the post-weld heat treatment of welded joints are susceptible to cracking, which requires re-processing of the welded connection up until there will be no cracks in the joints.

Accordingly would benefit from any improvements in the manufacture of composite impeller for Francis turbines, which would not lead to welded joints in the blades of the impeller and potential cracking of joints blades during post weld heat treatment.

The present invention relates to compound the impeller to the turbine Francis, containing at least two segments of the impeller, designed to connect together at their opposite surface areas for the formation of composite impeller having a top rim, a bottom rim and a variety of blades passing between the upper rim and lower rim and attached to them. The improvement of the present invention refers to the opposite surface areas of the segments of the impeller, which are located only along sections of the upper rim and lower sections of the rim and to the opposite surface areas of the segments of the impeller, which are located between adjacent composite blades of the impeller and are about them. Since the opposite surface sites are located only along sections of the upper rim and parts of the lower rim, none of the blades is cut, whereby is eliminated the welding of the blades in the process of formation of a compound of the impeller at the site of the dam. Accordingly, the composite impeller has no welded joints formed in the blades, which are heavily stressed working parts of the impeller.

In one embodiment of the invention the segments of the impeller are connected together by welded connection. This welding can be a partial receipt of weld penetration of the base metal. In an alternative embodiment, the upper rim can be connected mechanical fastening means such as bolts and nuts. Additionally it is envisaged that the weld material used in welded joints, is a material which does not require post weld heat treatment. Such material is, for example, welded material E309L.

Thus, according to the object of the present invention created a composite impeller for Francis turbines, containing at least two segments of the impeller, made with the possibility of connection together they protivole the relevant surface areas for the formation of a compound of the impeller, having a top rim, a bottom rim and a variety of blades passing between the upper rim and lower rim and attached thereto, while the opposite surface areas of the segments of the impeller are located only along sections of the upper rim and parts of the lower rim and the opposing surface areas of the segments of the impeller are located between adjacent composite blades of the impeller and are separated from them, and the composite impeller has a Central axis, and the upper rim has a Central opening round shape, while the opposite surface plots plots of the upper rim, when viewed from above, are from the Central hole with a radial offset from the Central axis.

Preferably, the segments of the impeller are connected together by welded connection.

Preferably, the weld material used in welded connection, does not require post weld heat treatment.

Preferably, the welded material contains welded material E309L.

Preferably, the opposing surface areas are located midway between adjacent blades.

Preferably, the opposing surface areas are located midway between adjacent blades.

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