FR2496169A1 - VISCOUS SHOCK ABSORBER WITH ROTOR CENTERING ELEMENT - Google Patents

Abstract

THE INVENTION RELATES TO A VISCOUS DAMPER WITH A ROTOR CENTERING ELEMENT. THIS SHOCK ABSORBER IS MADE BY SEALING THE ENDS OF A SUPPORT RING 56 BY MEANS OF ANNULAR GASKETS 59 AND 60 EXTENDING BEYOND THE OUTSIDE SURFACE OF THIS SUPPORT RING 56 AND PRESSING ON THE INTERNAL DIAMETER OF AN ANNULAR CROWN 64. THIS SHOCK ABSORBER IS SUITABLE FOR A BEARING SUPPORTING THE SHAFT 50 OF A TURBINE ROTOR AND WHICH IS ITSELF SUPPORTED BY A SPRING OVERLAY 70. THE INVENTION IS USED TO PREVENT AN INCREASE OF FREE SPACE CLEANING CLOSE TO THE BLADE HEADS OF A TURBINE ROTOR FOLLOWING A BENDING OF THE ROTOR WHEN USING A HYDRAULIC SHOCK ABSORBER BEARING.

Description

The present invention relates to a turbine

  two rotors and, in particular, damping bearings

viscous.

  As is well known, it is practically

  to support the high-speed shaft of a two-rotor gas turbine with radial bearings

  hydraulic damping. Similarly, we generally know

  that the natural frequency of the rotating pressure field can be modified by soliciting the damper

  viscous by means of a spring in order to avoid instability

  occurring as a result of uncontrolled vibrations

  ble. In patent reissue No. 30,210 issued February 1, 1980 to the names of D. F. Buono, N. G. Carlson, D. H. Hlibner and D. C. Moringiello, an example is described.

  of a system of this type in which a spring is

  parallel to the viscous damper, which has the effect of modifying the natural frequency of the

pressure.

  It has been found that the use of amortization

  viscous materials in a high-speed twin rotor turbine inherently influenced the free space

  circumferential rotor and this, as a result of the

  the latter in the free space defined by the film of oil. Obviously, the increased free space

  allows the escape of an excessive amount of air

  the head of the rotor blade and its adjacent seal with, consequently, an increase in fuel consumption specific to the thrust. In order to avoid this increase in consumption, it is

  a centering spring for keeping the game

  rotor, which avoids most of the deflection of the rotor. The strength of the spring

  this system is chosen so as to offer

  maximum rotor weight, for gyro loads and

  given gravitational force, while maintaining flexibility

  sufficient to allow damping by the film of oil under conditions of imbalance

important rotor.

  An object of the present invention is to provide

  a process to prevent rotor deflection in a two-rotor turbine, using

bearings with viscous damping.

  According to one characteristic of the invention,

  uses a centering spring for the damping bearing

  -sement viscous, so that the bearing rotor of the shaft does not abut against the bottom of the tank of the viscous damper during the maneuvers of

  the aircraft. the force of the centering spring is optically

  in such a way as to minimize the movement of

  tor in relation to the crankcase, while maintaining the freedom

  15 of movement required inside the screw damper

chef.

  Other features and advantages appear

  read the description and the claims

  Hereinafter, with reference to the accompanying drawings which illustrate an embodiment of the invention; in these drawings: FIG. 1 is a partial schematic view of the rotor and a support system without the incorporation of the device of the present invention; Figure 2 is a partial schematic view similar to Figure 1, but illustrating the damping bearing according to the present invention; and FIG. 3 is a partly schematic and partly sectional view illustrating the details.

of the invention.

  Although the present invention is described with reference to its preferred embodiment used with a rotor / shaft assembly for a two-rotor gas turbine, supported by three bearings, it is understood that the scope of the invention is not not limited to this

embodiment.

  In order to better understand this invention,

  tion, reference is made to Figure 1 which illustrates the

  tor (designated by a general

  reference 10) supported by three bearings 12, 14 and 16.

  The bearings 12 and 14 support the radial load and

  the bearing 16 supports the thrust load. The

  Particulars are well known and, for further details, reference is made to the "JT9D" and "JTIOD" models manufactured by the Pratt & Whitney Aircraft.

  Group "of the" United Technologies Corporation ".

  As can be seen in Figure 1, the deflection of the rotor d to its weight brings it to come

  press on the bottom of the wall of the screw damper

  chef. The importance of this deflection is based on the displacement of the bearing relative to the free space of the hydraulic damper when the rotor is subjected to a gravitational force or to a gyroscopic load. In this case, the weight and inertia of the rotor (i.e. shaft 18, compressor vane stages 20 and turbine blade stages 22) cause deformation of the shaft. as shown

the curve of the central line 24.

  Figure 2 shows the same rotor system

  where he uses the device of the present invention

  tion. The centering spring 30 supports

  the landing, so that the free space of the damping

  Hydraulic system 32 remains virtually unchanged when the rotor is subjected to the loads imposed by the maneuvers

of the aircraft.

  As it appears in the description below,

  above, the viscous damping bearing is located between the compressor and the turbine. However, this is not an indispensable aspect of the present invention and it will be appreciated by those skilled in the art that the damping bearing may be disposed at other locations.

  while several damping bearings can be provided

ment.

24961'69

  Therefore, using the centering spring, the annular free space defined by the reservoir

  32 ensures that free space "A" remains practically

  the same when the turbine is in the static state

  than. In a real test, it was found that the game

  could be reduced from 0.127 to 0.0254 mm, which represents

  a considerable advantage with regard to the

  fuel consumption specific to the thrust.

  Figure 3 illustrates the details of a preferred embodiment of a viscous damping bearing centered by a spring. As can be seen, the roller bearing generally designated by the reference numeral 40 comprises an inner race 42 and an outer race 44 1S between which are trapped several rollers 46

  (only one of whom is represented) retained in their posi-

  relating to a cage 48. The track

  42 is supported by a shaft 50 at the

  52 and 54. The outer race 44 is fixed in place and supported.

  by an annular element 56 at the intervention of an assembly

  rivet and locknut 58. The screw damper

  It is obtained by sealing the ends of the support ring 56 by means of annular seals 59 and 60 which protrude beyond the outer surface 62 of the support ring 56 and bear on the inside diameter of a crown. 64. It should be noted that the bearing assembly is not supported by the seals, but rather by a door spring

  70. Therefore, the landing is centered on the

  centering spool which consists of several cantilevered springs 70 (one of which is shown). As can be seen, one end of the spring 70 is attached to a bulkhead or housing support member 72 by a nut assembly 74, while its other end is attached to an extension 76 of the annular member 56 at

by means of a nut assembly 78.

  From the description above, it appears

  that the centering spring 70 serves to maintain the space

  free "B" in the hydraulic damper. It is obvious

  that the centering spring can be made more ef-

  with regard to his ability to bear the

  rotor, giving it increased rigidity. always

  However, this could result in reduced movement inside the viscous damper under

  in which the rotor is subjected to loading loads

  sequilibre (swirl). Consequently, the strength of the support spring must be optimized according to these

two contradictory conditions.

  It is understood that the invention is not limited

  to the particular embodiments illustrated and de-

  written here, but that various modifications can be made without departing from the spirit and the framework

  of its new concept as defined by the

hereinafter.

Claims (3)

  1. Rotor enclosed in a housing and comprising   a rotary shaft supporting several compressor blades   one end and a plurality of turbine blades, at the opposite end, characterized in that it comprises at least two bearings spaced axially along the shaft to support the latter by allowing it to rotate, a hydraulic damper provided on one of these bearings and comprising, close to this landing, a   cavity in which a fluid is conveyed to support   carry the bearing when the shaft is rotated   this tree can undergo deformation   tion of the depth of the aforementioned cavity, while de-   radially positioning the compressor blades to a corresponding extent, the heads of the blades being sufficiently spaced from the housing to prevent them from coming into contact with the inner diameter of the latter, and means for reducing the distance of the compressor. movement of the blade heads, this means comprising an elastic element fixed to the bearing to prevent this   last to move on the depth of the cavity.   Rotor according to Claim 1, characterized   in that the elastic element is a spring, one of which   tremity is attached to the shock absorber and the other end is attached to the housing.   Rotor according to Claim 2, characterized   in that the spring force is selected to re-   at least the deviation of the rotor resulting from the load imposed on it by the gyroscopic and acceleration forces during the acceleration of the shaft to   its operating speed in steady state.