Fluid reaction surfaces (i.e. – impellers) – Specific working member mount – Welded – cemented or fused
Patent
1994-06-16
1996-07-16
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
Specific working member mount
Welded, cemented or fused
416218, 416220R, 416229A, 416234, 416241R, 416241B, 29464, 29530, 29559, 2988921, 2988971, F01D 528
Patent
active
055361455
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a hybrid turbine wheel having blades made of a ceramic or composite material and fixed on a metal hub, and also to an inserted-blade turbine wheel obtained by performing the method. The invention is applicable both to the field of industry, and to the field of aeronautical and space engineering.
PRIOR ART
Documents EP-A-0 176 386, FR-A-2 637 319, and FR-A-2 476 766 disclose examples of one-piece turbine wheels in which both the hubs and the blades are made entirely of composite materials. Such turbine wheels offer the advantage of being lightweight, but they are difficult to manufacture because the unidirectional strength characteristics of the composite fibers must be adapted to the multidirectional stress field that exists in an assembly constituted by a disk and by blades, and balancing problems also exist.
In that type of turbine wheel, it is also necessary to take into account the shear and deformation characteristics of the matrix and of the fibers, and there is also a danger that the blades might shear off at the rim.
Also, Documents FR-A-2 608 674, EP-A-0 367 958 and U.S. Pat. No. 4,326,835 disclose examples of compound turbines having blades made of a ceramic or composite material, each of the blades having a base enabling it to be inserted into a metal hub.
In that type of turbine, the blades are manufactured in the form of discrete components, and they are then received and locked in the periphery of a metal disk by assembly means, e.g. dovetail means.
Such a blade has a complicated shape because its base is dovetail or Christmas tree shaped. Therefore, it is difficult to machine the composite material, and also to assemble the blades with the hub.
Turbine rotors that are made entirely of metal are also known. But they have considerable mass, and, as a result of the way in which they are assembled, their speeds of rotation are limited.
OBJECT AND BRIEF DESCRIPTION OF THE INVENTION
An object of the present invention is to remedy the above-mentioned drawbacks of known turbine wheels, and in particular to enable turbine wheels to be manufactured simply that have improved mechanical strength and that are capable of withstanding high speeds of rotation under difficult environmental conditions.
To these ends, the invention provides a method of manufacturing a turbine wheel having blades made of a ceramic or composite material and inserted into a metal hub, said method being characterized in that it comprises the following steps: blade having an essentially right cylindrical shape with a cross-section defining a predetermined non-circular shape, and a hole is formed in the base of each blade, the hole being essentially perpendicular to the axis of the blade; corresponds to the width of the hub of the wheel, the ring being provided with orifices corresponding to the predetermined cross-sectional shape of the blades; rim-forming cylindrical ring; are successively threaded onto an open annular rigid metal wire which has a smaller diameter than the cylindrical ring and which passes through said holes formed in the bases of the blades; the annular rigid metal wire is disposed inside a sealed housing after removable spacers or inserts have been interposed between the heads of the blades projecting radially outwards beyond said cylindrical ring; powder form that is inserted into the sealed housing so as to make the hub of the turbine wheel while embedding the blade bases and the annular rigid metal wire by using the powder metallurgy technique; and turbine wheel is machined and said removable spacers are removed.
By retaining the blades by means of the rigid metal wire passing through their bases, it is possible to hold the blades effectively both while they are being installed, and during the final assembling step in which the blade bases and the rigid metal wire are embedded in the hub made of a metal alloy by hot isostatic compaction.
The method of the invention enables blades to be manufactured "by the yard". Accordin
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Look Edward K.
Societe Europeenne de Propulsion
Verdier Christopher
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