US3306576A - Arrangement for reducing steam condensation within steam turbines - Google Patents

Description

Feb. 28, 1 J. c. CHABOSEAU ARRANGEMENT FOR REDUCING STEAM CONDENSATION WITHIN STEAM TURBINES Filed May 24, 1965 U a 9 M5 o M10 V a NIH C 5 e L r O In C H G 8 J BY J W ,JW & PMZW United States Patent 7 Claims. (Cl. 253-76) The present invention relates to an improved arrangement for operating a steam turbine comprising stages in which there is a relatively high degree of humidity in the steam.

If there is a relatively high degree of humidity in the steam in certain stages of a steam turbine, and the physical conditions of balance between water and steam are fulfilled, a water film can form on the stationary, guide blades. The film is dragged onwards by the surrounding steam, hereinafter called the working steam, and splits up into droplets which collect in the turbulence in the wake of the blades, and strike the following blades. This results in erosion of the latter, and a reduction in the efficiency of the turbine because of the impacts of these droplets on the blades.

The problem of the present invention is to avoid these disadvantages.

It is known that condensation takes place in particularly vigorous fashion in certain zones of steam flow. These are the zones in which the very small drops which form when the steam condenses, and which are generally harmless because of their small size, bind together and form significant drops which are precipitated on the surfaces of parts of the machine in contact with the steam. This phenomenon occurs above all in boundary layers and in turbulences which are more particularly set up by friction on the walls, in turbulent wakes and'when there are aerodynamic mis-matches, for example, terminal losses. In the same way, it is known that drops of Water produced in this manner collect especially on the walls of the steam-path and on the pressure side of the blades. The stream-path is to be understood here to mean the space taken up by the steam between the housing and the shaft. The walls of the steam-path are the internal surfaces of the housing and the surface of the rotor at the base of the blades which it carries.

The improvement according to the invention resides in that auxiliary steam is introduced at suitably chosen points into the steam-path, and this auxiliary steam is at sufliciently high temperature at least to reduce condensation in those zones of the steam-path in which mixing takes place. It is easily comprehensible that, generally expressed, the fact of introducing a medium at relatively high temperature and in sufficient quantity into steam which is condensing as a result of expanding and performing work makes it possible to obtain a mixture which is at a sufliciently high temperature for its humidity content to be appreciably lower than what would be present if the hot medium were not introduced.

Such a procedure, carried out in a steam turbine, would exhibit poor efliciency if the total quantity flowing through the turbine participated therein. However, if it concerns only a small portion of the quantity of steam, the said disadvantage becomes negligible, since it is outweighted by an improvement in the internal efiiciency of the machine resulting from the disappearance of the drops of water striking the blades. It is therefore advantageous for the hot auxiliary steam to be introduced in those zones in which the water droplets tend to bind together.

The auxiliary steam may be taken above the mixing zone from the working steam flowing through the turbine,

3,306,576 Patented Feb. 28, 1967 'ice and introduced into this zone after having been throttled or reheated in a suitable supplementary device. It may likewise be supplied by a separate steam-boiler. The auxiliary steam is passed through suitably arranged conduits, and flows into the steam-path through orifices in the walls of the .blades or of the steam-path, insofar as the same form part of the said zones.

A blade suitable for carrying out this process is characterized in that it comprises at least one internal steamv feed conduit proceeding from one end of the blade and communicating with orifices in the Wall of the blade, from which orifices the auxiliary steam passed through the steam-feed conduit flows out. The orifices are expediently arranged on the pressure side of the blade, and are supplied with steam which is sufliciently superheated for it still to be superheated even after passing through the orifices.

Different embodiments of the invention are described hereinafter with reference to non-limitative examples.

FIGURES 1 and 2 illustrate profile sections of a solid and a hollow blade respectively.

FIGURES 3 and 4 show such blades in perspective.

FIGURE 5 depicts a meridian section through the steam-path between the guide blades.

In the figures, 1 designates the blade, and 2 the direction in which the working steam flow. The solid blade of FIGURES 1 and 3 has a steam-feed conduit 3 passing through it along its length, and the said conduit is in communication with the pressure side of the blade via one or more transverse ducts 4. The interior of the hollow blade of FIGURES 2 and 4 here plays the part of the steam-feed conduit 3 and the ducts 4 in the solid blade of FIGURES 1 and 3. Steam-feed conduits and ducts may also be embodied in any other suitable fashion.

Whether the blade is solid or hollow,- it may comprise a plurality of orifices on the pressure side, which may, for example, take the form of circular apertures 5 (FIG URE 3) or radial gaps 6 (FIGURE 4) distributed over all or part of the height of the blade. In all cases, the auxiliary steam passes through the orifices, and mixes with the Working steam after expanding from the pressure prevailing in conduit 3 to the surrounding pressure, which expansion gives it suflicient velocity to produce correct mixing.

At the ends of the blades, ie, in the vicinity of the walls of the steam-path, and in particular of the above-named external wall, it is advantageous relatively to enlarge the field of the orifices, or to distribute them to a greater extent, in order to be able better to supply auxiliary steam to this zone which is especially loaded with drops of water.

In FIGURE 5, the auxiliary-steam outflow apertures along the pressure side of the guide blade 1 are designated by 5. The outflow apertures 7 and 8 are intended more particularly for supplying those zones of the steam-path in the vicinity of the ends of the blades. There is likewise an orifice 9 at the end of a conduit 10 which passes through the walls of the housing in the sectional plane.

I claim:

1. In a multi-stage steam turbine, the improvement wherein the stationary, guide blading thereof includes an internal conduit extending longitudinally of the same and in communication with orifices located in the wall of the blading, and means discharging auxiliary steam through said orifices for mixing with the main steam flow engaging the surfaces of the blading, the temperature of said auxiliary steam being sufficiently high to at least reduce condensation of the main steam flow in those zones of the flow path where mixing of said auxiliary and main steam occurs.

2. A multi-stage turbine as defined in claim 1 wherein said orifices are disposed on the pressure side of the blading.

3. A multi-stage turbine as defined in claim 1 wherein said orifices are constituted by circular apertures extending along the pressure side of the blading.

4. A multi-stage turbine as defined in claim 1 wherein said orifices are constituted by a gap extending radially along the pressure side of the blading.

5. A rnulti-stage turbine as defined in claim 1 wherein said orifices are constituted by a pair of parallel spaced gaps extending radially along the pressure side of the blading.

6. A multi-stage turbine as defined in claim 1 and which further includes auxiliary steam discharge orifices located in the wall of the blading at the end thereof.

7. A multi-stage turbine as defined in claim 1 and 4 blading terminating in an orifice communicating with the main steam flow path and through which said auxiliary steam is also discharged.

References Cited by the Examiner UNITED STATES PATENTS 1,864,352 6/1932 Hilgers 60-73 2,149,510 3/1939 Darrieus.

3,123,283 3/1964 Leis 230132 FOREIGN PATENTS 1,115,125 12/1955 France.

MARTIN P. SCHWADRON, Primary Examiner.

which further includes a bore through the housing for the 15 EVERETTE A. POWELL, JR., Examiner.

Claims (1)

1. IN A MULTI-STAGE STEAM TURBINE, THE IMPROVEMENT WHEREIN THE STATIONARY, GUIDE BLADING THEREOF INCLUDES AN INTERNAL CONDUIT EXTENDING LONGITUDINALLY OF THE SAME AND IN COMMUNICATION WITH ORIFICES LOCATED IN THE WALL OF THE BLADING, AND MEANS DISCHARGING AUXILIARY STEAM THROUGH SAID ORIFICES FOR MIXING WITH THE MAIN STEAM FLOW ENGAGING THE SURFACES OF THE BLADING, THE TEMPERATURE OF SAID AUXILIARY STEAM BEING SUFFICIENTLY HIGH TO AT LEAST REDUCE CONDENSATION OF THE MAIN STEAM FLOW IN THOSE ZONES OF THE FLOW PATH WHERE MIXING OF SAID AUXILIARY AND MAIN STEAM OCCURS.

Images