US2421890A - Turbine blade - Google Patents

Description

J1me 1947' J. E. JOHANSSON 2,421,890

- TURBINE BLADE Filed Nov. 19, 1945 2 eetsheet 1 June 10, 1947. JQHANSSQN 2,421,890-

TURBINE BLADE Filed Nov, 19, 1945 2 Sheets-Sheet 2 Patented June 10, 1947 UNITED STATES PATENT OFFICE TURBINE BLADE Johan'Erik Johansson, Gothenburg, Sweden, assignor to A tiebolaget Gotaverken, Gothenbmig, Sweden, a corporation of Sweden Application November 19,

In Sweden November 27,

3 Claims.

The present invention relates to an arrangement in turbine blades for axial flow turbines in which each moving blade is by means of one or more peripheral partitions divided into two or more sections located radially outwardly of each other. One of the objects of the invention is to provide a rigid and reliable connection for the blades, which is of great importance on account of the increased action of the rotating masses due to the partitions. A further object of the invention is to simplify the assembling work for the blades in spite of the presence of the partitions. A still further object is to improve the transmis sion of force between the connecting means of the blades.

The invention is hereinbelow described more in detail with reference to an embodiment illustrated in the accompanying drawing, in Which- Fig. 1 shows a partial section of a turbine devised in accordance with the invention, Fig. 2 is a perspective view of a moving blade according to the invention; and Fig. 3 is a section taken on the line III-III, Fig. 1.

The type of turbine shown by way of example in Fig. 1 can advantageously be used as a gas turbine .driven by exhaust gases from an internal combustion engine. .In the drawing, reference. numeral l indicates an inlet chamber for gases suitably discharged from the engine at a relatively high pressure, while numeral 2 indicates an inlet chamber for low pressure gases, such as gases finally expanded in the engine.

From the inlet chamber I, the high pressure gases are supplied through a nozzle system 3 into a moving blade rim 4 the blades of which may advantageously be of the impulse type, Hence, the gases pass through a guide vane rim 5 to a turbine rotor the blades 6 of which are preferably and substantially of the reaction type.

The low pressure gases entering the inlet chamher 2 pass through a nozzle system I directly to the outer portions of the moving blades 6. The heat drop of the high pressure gases can be chosen such as to be equal to the heat drop of the low pressure gases so that the blades 6 may be shaped principally equally throughout their lengths. As a rule, the temperature of the high pressure gases is so much higher than the temperature of the low pressure gases that the temperature ahead of the blades 6 will be higher for the high pressure gases than for the low pressure gases. At equal heat drops. the pressure of the partly expanding high pressure gases will, consequently, be lower ahead of the blades 6 than the pressure of the low pressure gases. Assuming that both the high- 1945, Serial No. 629,628 1944 pressure gas and the low-pressure gas after having passed the blade 6 shall have substantially the same heat contents and that the heat drop in the blade 6 shall be approximately the same 5 for both media, the result will be that the highpressure gas should substantially have the same heat contents as the low-pressure gas ahead oi the blade 6. However, as the temperature of the high-pressure gas is higher than that of the lowpressure gas, its pressure must consequently be lower. Thus, the high-pressure gas in the first stage is expanded down to substantially the same heat contents as the low-pressure .gas in order that the blade 6 can be given substantially the same shape along its entire length, and on account of the difference of temperature the high-pressure gas will have a lower pressure than the lowpressure gas ahead of the blade 6. With respect to the difierence in pressure, it is desirable to divide the blades into two sections. Under certain operating conditions, it may prove suitable to cut on the supply of low pressure gases to the turbine, in which case the outer sections of the blades 6 are idling. Also in this case, it may be desirable vto separate the two sections of the moving blades from each other by means of peripheral partitions t, in order to maintain constant the .cross sectional area through which the high pres- .sure gases pass through the inner section of the blades. Since a certain difference in pressure and in heat drop may exist between the high pressure gases and low pressure gases passing through the final stage, the outer portions of the blades 6 may be devised somewhat different from the inner portions.

As will be seen from Fig. 2, the partitions 8 may consist of partition walls connected with or formed in one piece with the appertaining blades, said partition walls abutting against each other along their edges 9. As will be further seen from Fig. 2, a portion 10 of each partition extends beyond the forward edge of the blade 6 and coop erates with a corresponding projection of the stationary guide vane partition. As indicated in Fig. 1, the edges of the cooperating partitions are in overlapping relation and serve as sealing members between the different driving fluids throughout the whole turbine blade system.

As will appear from Fig. 3, the grooves II for the blade roots are located at an acute angle '1) with respect to the plane of the rotor, and the abutting edges 9 of the partitions 8 are located at the same angle 12. Consequently, the thickened portions l2 of the blade roots can be inserted one after the other into the grooves H.

3 In spite of the partitions 8, the blades according to the embodiment described can be located entirely within the boundary of the partitions 8, as viewed in a radial direction, which, of course, would not be possible if the grooves and the edges of the partition were located at right angles to the.

plane of the rotor, that is in the direction indicated by the dash and dot line l3. The longitudinal axis of the partitions coincides with the longitudinal axis of the grooves II, as viewed in a radial direction.

In the embodiment shown, the grooves and the blade roots are substantially extending in the same direction as the main direction of the blades 6 viewed in radial direction. It also appears from Fig. 3 that the projections of the grooves and blade roots, viewed in radial direction, cover the major portion of the cross-sections of the blades and the major portion of the lengths of said cross-sections. This is of great advantage to the transmission of the force between the blade roots and the grooves and is especially important in blades having two or more sections, in which the partitions between the sections considerably increase the influence of the rotating masses.

Although the invention is described above in conjunction with turbine blades substantially of the reaction type, it may obviously be used as well for blades of the impulse type.

What I claim is:

1. In an axial flow turbine, a turbine rotor having straight grooves at the periphery disposed at acute angles to the plane of said rotor, said grooves extending across the rotor from one end to the other end thereof, a number of moving blades having roots inserted into said grooves, and peripheral partitions secured to said blades and adapted to divide said blades into at least two sections located radially outwardly of each other, each of said portions having edges abutting against adjacent partitions and being inclined, with respect to the plane of said rotor, at the same angle as said grooves and roots.

2. In an axial flow turbine, a turbine rotor having straight grooves at the periphery disposed at acute angles to the plane of said rotor, said grooves extending across the rotor from one end to the other end thereof, a number of moving blades having roots inserted into said grooves,

and peripheral partitions secured to said blades and adapted to divide said blades into at least two sections located radially outwardly of each other, each of said portions having edges abutting against adjacent partitions and being inclined, with respect to the plane of said rotor, at the same angle as said grooves and roots, and each of said grooves and roots, as viewed in radial direction towards said rotor, covering the major portion of the cross-section of said blade and the major portion of the length of said cross-section, and the longitudinal direction of each partition coinciding with the longitudinal direction of the ap pertaining groove.

3. In an axial flow turbine, a turbine rotor having straight grooves at the periphery disposed at acute angles to the plane of said rotor, said grooves extending across the rotor from one end to the other end thereof, a number of moving blades having roots inserted into said grooves, peripheral partitions secured to said blades and adapted to divide said blades into at least two sections located radially outwardly of each other, each of said portions having edges abutting against adjacent partitions and being inclined, with respect to the plane of said rotor, at the same angle as said grooves and roots, and each of said partitions having a projection extending beyond the inlet edge of the appertaining blade, and a corresponding projection on another part of the turbine, said projections being in overlapping sealing relation to each other so as radially to separate different driving fluids passing through diiferent blade sections separated from each other by said partitions.

J OHAN ERIK J OHAN SSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS France June 4, 1923

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