Turbomachine with a vaneless rotating diffuser and nozzle

Details Turbomachine with a vaneless rotating diffuser and nozzle Turbomachine with a vaneless rotating diffuser and nozzle

2002-03-19

2004-03-30

Yu, Justine R. (Department: 3746)

Pumps

Motor driven

Fluid motor

C417S405000, C415S224500

Reexamination Certificate

active

06712588

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO MICROFICHE APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to improvements made to radial turbomachines of the type comprising at least one centripetal radial turbine comprising a rotor mounted to rotate in a casing about an axis of rotation, the rotor comprising a disk that can rotate about its axis which is coincident with the axis of rotation, and in which a face of the disk facing in the downstream direction with respect to the direction of flow of a fluid let into the turbine is fitted with blades.
2. Background Art
Centripetal radial and radial-axial turbines of the state of the art generally comprise, from the upstream to the downstream end, an inlet volute, a plain (that is to say unbladed) nozzle with fixed walls, followed by a bladed centripetal radial rotor or a radial-axial rotor when the stream flowing through the rotor changes from the radial direction to the axial direction, and finally a plain and generally axial oriented exhaust diffuser.
In a configuration of such a turbine with a low cross section, according to a known alternative form, the turbine has no inlet volute, and inlet is via an axial-centripetal radial duct of revolution about the axis of rotation. According to another known alternative form, a bladed nozzle is arranged between the inlet volute or the axial-radial inlet duct and the plain nozzle.
Furthermore, the rotor disk, in the inlet region, has significant notches or apertures between the blades, and this makes it possible to reduce the stresses in the rotor and its inertia.
These known centripetal radial and radial-axial turbines have the following disadvantages: their plain nozzle has a radius ratio (outside radius/inside radius) generally higher than 1.1, so as to limit the erosion of the trailing edges of the blades of the bladed nozzle, this erosion being due to the centrifuging of particles. In the absence of a bladed nozzle, the radius ratio of the plain nozzle is very high, because this radius ratio governs the acceleration of the fluid. As the speed of the fluid leaving the plain nozzle is high, the length of the stream lines is long, the coefficient of friction is not insignificant, and the hydraulic diameter small, this means that losses of stagnation pressure by viscosity may be significant in the plain nozzle.
Furthermore, in the rotor and more specifically at the notches thereof, the frictional losses are once again not insignificant, because the friction rate to be considered is the rate of flow with respect to the fixed casing, that is to say a rate similar to the rate at which the rotor rotates.
Finally, at the exhaust, and more specifically in the case of non-optimum operation (away from the nominal point), the axial exhaust diffuser does not allow the tangential kinetic energy to be converted into pressure. This is rendered possible by the use of a radial exhaust diffuser with fixed walls. However, in the latter instance, the tangential friction greatly diminishes the pressure gains that could theoretically be achieved by the use of such a component.
BRIEF SUMMARY OF THE INVENTION
One object of the invention is to improve the overall efficiency of this type of turbomachine by improving their inlet and, preferably also, or alternatively, their exhaust.
Another object of the invention is to combine, within such a radial turbomachine, a centrifugal compressor with the centripetal turbine according to the invention so as to obtain a turbocompressor unit the respective inlets and/or exhausts of which are perfected, so as to improve the overall efficiency of the turbocompressor unit thus obtained by comparison with similar units of the state of the art, and in particular by limiting the axial bulk of such a unit at the cost of a limited increase both in the cross section and the weight and structural complexity of such a turbocompressor unit.
Yet another object of the invention is to propose a turbomachine with a centripetal radial turbine and, possibly, centrifugal radial compressor, which can be produced by using two-dimensional machining techniques, of the microelectronic type.
The field of application at which the invention is targeted relates essentially to the microturbines, particularly of the type used for producing auxiliary power units for aircraft or for propelling unmanned aerial vehicles, such as microdrones.
To this end, the invention proposes a turbomachine comprising at least one centripetal radial turbine of the type set out hereinabove, and which is characterized in that the centripetal turbine is supplied with fluid by a plain radial inlet nozzle rotating freely and coaxially with respect to the turbine rotor and surrounding the turbine rotor.
One essential advantage afforded by the plain freely rotating radial nozzle is that it makes it possible to very significantly reduce the losses through friction on the walls of this member because the kinetic energy of the fluid in the movement associated with the walls is practically quartered. In the same way, at the apertures in the rotor, the presence of the rotary disk of the nozzle makes it possible to reduce the losses through friction of the fluid against the fixed casing, because the kinetic energy of the fluid in the movement associated with the walls is also quartered.
To improve performance, the turbomachine of the invention also and advantageously comprises at least one centrifugal radial compressor comprising a rotor coaxial with the turbine rotor and rotating as one with the turbine rotor about the axis of rotation in the casing, the compressor rotor comprising a rotary disk coaxial with the turbine rotor disk and of which a face facing in the upstream direction with respect to the direction of flow of a fluid let into the compressor is equipped with blades compressing the fluid toward a plain radial exhaust diffuser rotating freely and coaxially with respect to the plain and freely rotating radial turbine inlet nozzle, the compressor exhaust diffuser surrounding the compressor rotor and being surrounded by a fluid flow uptake volute in communication with a fluid inlet volute surrounding the turbine inlet nozzle, for supplying the latter through said inlet nozzle.
The function of the compressor plain radial exhaust diffuser is to convert some of the kinetic energy acquired by the fluid leaving the compressor wheel into a pressure increase, because of the increase in the radius or distance between the point in question and the axis of rotation of the machine, and because of the conservation of momentum, give or take the friction on the walls, this friction being reduced because this plain radial diffuser is mounted so that it can rotate freely. The presence of moving walls, both for the centrifugal compressor plain radial exhaust diffuser and for the centripetal turbine plain radial inlet nozzle makes it possible to appreciably reduce the aerodynamic losses through friction between fluid and walls in the two plain radial ducts passing one through the nozzle and the other through the diffuser, these aerodynamic losses being associated with the fact that there is significant momentum both on the compressor side and on the turbine side.
Advantageously, to improve the compactness and simplify the structure of the machine, and to further reduce the aerodynamic losses, the compressor plain radial exhaust diffuser and the turbine plain radial inlet nozzle are arranged as a single assembly free to rotate coaxially with respect to the turbine and compressor rotors.
In this architecture, it is advantageous for the freely rotating assembly to comprise an intermediate disk mounted so that it is free to rotate, between the turbine and compressor rotor disks, about a common main shaft connecting together the turbine and compressor rotor disks so that they rotate as one about the axis of rotation. Thus frictional losses at the rotor disks are also reduced because the intermediate disk is set in rotation between the turbine and

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