GB2217790A - Adjusting gas turbine nozzle vanes - Google Patents

Description

2.2'17790 IMPROVED SYSTEM FOR SETTING ADJUSTABLE-DIRECTION GAS TURBINE

NOZZLES IN POSITION This invention relates to a new robust system of small overall size enabling the length of the connecting rods which connect to a single control ring all the levers rigid with the corresponding shanks of adjustable-direction nozzles of a gas turbine to be easily varied to the appropriate extent, so allowing said nozzles to be properly set in position so as to make the passage area of the channels defined by the vanes of adjacent nozzles rigorously constant. It is well known that in a gas turbine provided with adjustabledirection nozzles, these are generally operated simultaneously by a single control ring to which the levers rigid with the shanks of said nozzles are connected on assembly by connecting rods. When this assembly is complete, the passage area defined by the spaces between the vanes of adjacent nozzles must be constant throuE;hout, and it must therefore be possible to set the individual nozzles in position in such a manner as to compensate for any unbalance due to inevitable manufacturing tolerances. In the current state of the art said position setting is done by varying the length of the individual connecting rods or rather the distance between the points at which each connecting rod is hinged to the control ring and to the lever of the respective nozzle, this being done by an intermediate sleeve having threaded ends with right and left- handed threads respectively, on which two eyelets of the connecting rod are screwed. The length of the connecting rod is varied by screwing said sleeve to a greater or lesser extent, to transmit an angular movement in one direction or the other to the corresponding lever and consequently to the nozzle rigid with it so that it rotates about its shaft, which is supported by a bearing housed in the turbine casing. A known system of this type for setting adjustable-direction nozzles of a gas turbine in position has however the serious drawback that the connecting rods are very weak in that because of their necessarily small dimensions and particular shape they easily break, particularly if the nozzles jam. In addition, the need for intermediate sleeves increases the overall bulk of the connecting rods, to the detriment particularly of those turbines having a large number of adjustabledirection nozzles.

The object of the present invention is to obviate said drawbacks by providing a system for setting adjustable-direction nozzles of a gas turbine in position which does not, result in increased bulk and in particular does not result in connecting rod weakness, ie is robust and of small overall size, in addition to being efficient, reliable and of rapid operation. This is attained substantially in that said rotation for sett.ing each nozzle in position is effected by varying the distance 1 I between the points at which each connecting rod is hinged respectively to the control ring and to the lever of said nozzle, by means of an eccentric pin. Thus, the system for setting adjustable-direction nozzles of a gas turbine in position, each nozzle being supported rotatably by a bearing housed in the turbine casing and being rigid with a lever which is disposed orthogonal to its shank and connected by a connecting rod to a single control ring for simultaneously operating all the levers, is characterised according to the present invention in that each said connecting rod is connected to said control ring by a ball Joint and to said nozzle lever by another ball joint, the eccentricity of this latter being adjustable by a key. The invention is described in detail hereinafter with reference to the accompanying drawing, which illustrates a preferred embodiment thereof by way of non-limiting example only, in that technical or constructional modifications can be made thereto but without leaving the scope of the present invention. The figure of said drawing is a partly sectional partial isometric view of the system according to the present invention for setting adjustable-direction nozzles of a gas turbine in position. In the figure, the reference numeral 1 indicates one of the adjustable-direction nozzles of a gas turbine, the shank 2 of which is rotatably supported by a bearing 3 housed in the turbine casing 4 and is rigid with one end of a lever 5 disposed orthogonal to it. The other end of the lever 5 comprises a fork 6 into which the eyelet 7 of a connecting rod 8 is inserted. Said eyelet 7 is connected to the lever 5 by the ball joint 9 which is held in position by a pin 10 comprising a cam 11 of eccentricity e, the position of which can be adjusted by an Allen key which is inserted into a cavity 12 provided for this purpose. The other eyelet 13 of the connecting rod 8, disposed orthogonal to the eyelet 7, is connected by a ball Joint 14 to a single control ring 15 having through holes 16 for fixing said ball joints 14.

i 1 5 CLAIMS

A system for setting direction-adjustable nozzles of a gas turbine in position, each nozzle being supported rotatably by a bearing housed in the turbine casing and being rigid with a lever which is disposed orthogonal to its shank and is connected by a connecting rod to a single control ring for simultaneously operating all the levers, wherein each connecting rod is connected to said control ring by a ball joint and to said nozzle lever by another ball joint, the eccentricity of the latter being adjustable.

2. A system as claimed in claim 1, wherein the eccentricity of the latter ball joint is adjustable by a key.

3. A system as claimed in claim 1, substantially as hereinbefore described with reference to, and as shown in, the drawing.

led 1989 at The Patent Ofnoe. 8 House, W71 Holbom In WC1R 4TP. Purthcr Copies maybe obtained from The Patent Ofnze. Wee Branch, St)Lary Cray, Orpir4Lon, Icent ERLS 3BD. Printed by Multiplex techniques ltci, St, rent Son. 1,87