FR2518644A1 - Multiple stage turbo machine - has one high pressure and two low pressure stages all geared to output shaft - Google Patents

Abstract

The turbo-machine has a high pressure stage (1), fed with fluid and at least one, probably two, low pressure staqes (3) fed from the high pressure stage. Each stage has an individual shaft (6,7) with a gear train to transfer the shaft couples to an output shaft (12). The gear train has a pinion (8) with helical teeth on the high pressure shaft (6). This meshes with two toothed wheels (9) meshing with the low pressure shafts (7). These shafts each have a pinion (10) meshing with a wheel (11) on the output shaft.

Description

Turbo-marchine
The present invention relates to a new turbo-machine structure.

 It is known that conventional turbo-machines comprise a high pressure stage and a low pressure stage which are crossed by the same mass flow of fluid, which transmits or receives energy. Consequently, for a given turbo-machine model, the power is limited by the maximum volume flow rate at the low pressure stage, while it would be possible to pass a higher flow rate to the high pressure stage and to improve consequently the efficiency of the machine.

 Furthermore, the increase in the volume of the low pressure stage is limited by technological problems of mechanical resistance of its blades to centrifugal forces, the rotational speeds being relatively high with the aim of reducing the dimensions of the mobile members and consequently reduce ventilation losses and leaks at constant power.

 The present invention overcomes the drawbacks previously shown and it relates to a new turbo-machine structure, the advantages of which will be explained in the following.

 The subject of the invention is therefore a turbo-machine of the type comprising a high pressure stage supplied with a fluid, and at least one low pressure stage supplied by said high pressure stage, characterized in that each stage comprises an individual shaft, the turbo-machine comprising a gear system for transferring the torque of said individual shafts onto an output shaft of the turbomachine.

Other characteristics and advantages of the invention emerge from the description which follows, given by way of purely illustrative but in no way limiting, with reference to the appended drawings in which
FIG. 1 schematically represents a turbo-machine according to the invention.

 FIG. 2 schematically represents the position of the various wheels and shafts used in the turbo-machine according to the invention.

 The turbo-machine shown in FIG. 1 comprises a high pressure stage 1 supplied with fluid, for example steam, via a pipe 2. On either side of the high pressure stage 1 are arranged two low-pressure stages 3 supplied by said high-pressure stage 1 via pipes 4, the fluid leaving via pipes 5. Inside these stages, in the known manner, are rotors or blades ( not shown) mounted at the end of shafts 6 and 7 for the high pressure stage 1 and the low pressure stages 3 respectively, these rotors being of course driven by said fluid.

 The axes of the shafts 7 are symmetrical with respect to the axis of the shaft 6. On the shaft 6 of the high pressure stage 1 is wedged a pinion 8 with chevron teeth on which mesh two toothed wheels 9, each of them being shrunk onto one of said shafts 7 of the low pressure stages 3.

 Furthermore, it can be seen that at the lower end of each of the shafts 7 are mounted pinions 10 with collar stops (not shown) on which meshes a wheel 11 wedged on the output shaft 12 of the turbo-machine, the axis of this shaft being arranged in a plane different from that of the axes of the trees 6 and 7 as it appears-more particularly in reference to FIG. 2.

 FIG. 1 also shows a casing 13 inside which the movable members described above are arranged, these members, in particular the shafts, journalling in the known manner in bearings associated with the casing 13 and which have therefore not been illustrated in detail.

 However, it will be noted that advantageously the output shaft 12 pivots in a thrust bearing 15.

 In addition, flanges such as 14 are provided for the purpose of fixing the high pressure 1 and low pressure 3 stages to the casing 13, but however any other mounting of said stages could be adopted, for example in a single casing with distribution: internal fluid between the stages.

 FIG. 1 also illustrates the direction of rotation of the shafts 6 and 7, the direction embodied by the fleohes F and F 'respectively.

The main advantages of a turbo-machine according to the present invention are therefore the following:
Firstly, the use of two low-pressure stages makes it possible to divide the thermodynamic power as well as the mechanical power of the machine; these powers are then taken up by the wheels and pinions and supplied to the output shaft. This results in a significant improvement in efficiency due to the possibility of increasing the speed of the high-pressure stage on the one hand, and of reducing the dimensions of the low-pressure stages on the other hand.

 In addition, such a structure makes it possible to avoid the use of axial stops mounted at the end of the rotors1 such stops consuming considerable power as a result of friction at high rotational speeds. In fact, the assembly of shaft lines can be brought to a single fixed point situated on the line of the output shaft at the level of the thrust bearing 15, by means of collar stops disposed on the pinions 10.

 In addition, in the case where a so-called "cantilever" mounting of the rotors is carried out, it is even possible to eliminate the radial bearings holding said rotors in their respective stages.

 Such advantages translate into a marked improvement in the overall efficiency of the turbo-machine and a reduction in the overall manufacturing price.

 The invention therefore finds advantageous applications in all fields of use of turbo-machines, in particular in the case of low installed powers.

 Of course, the invention is in no way limited to the embodiment described and shown, which has been given only by way of example.

In particular, it is possible, without departing from the scope of the invention, to modify details, to change certain provisions or to replace certain means by equivalent means.

Claims (6)

 1 / Turbo-machine of the type comprising a high pressure stage (1)  supplied by a fluid and at least one low pressure stage (3) supplied  by said high pressure stage (1), characterized in that  each stage (1, 3) has an individual tree (6, 7), the turbo  machine comprising a gear system for transferring the torque  said individual shafts on an outlet shaft (12) of the turbo  machine.  2 / Turbo-machine according to claim 1, characterized in that  which has two low pressure stages (3).  3 / Turbo-machine according to claim 1, characterized by the fact  that said gear system comprises a pinion (8) with toothed  chevron wedged on the shaft (6) of the high pressure stage (3) and meshed on two toothed wheels (9) respectively hooped on each  shafts (7) of the low pressure stages (3), said shafts low pres  sion (7) each comprising a pinion (10) meshing on a wheel (11)  wedged on said output shaft (12) of the turbo-machine.  4 / Turbo-machine according to claim 3, characterized in that the axis of said output shaft (12) is arranged in a different plane  that of the axes of the shafts (6, 7) of said high pressure stages (1)  and low pressure (3).  5 / Turbo-machine according to one of claims 1 to 4, characterized by  the fact that said output shaft (12) pivots in a bearing at  stop (15).  6 / Turbo-machine according to one of claims 2 to 5, characterized  by the fact that the axes of the shafts (7) of the low pressure stages (3)  are symmetrical about the axis of the tree (6) of the upper storey  pressure (1).