US1027201A - Turbine-blade. - Google Patents

Description

W. GRUN. TURBINE BLADE. APPLICATION FILED JULY 3, 1911.

Patented May 21, 912.

WITNESSES.

WILLIBALD: GRUN', OF FRANKFORT-ON-THE-MAIN, GERMANY.

TURBINE-BLADE.

Specification of Letters Patent.

Patented May 21, 1912.

' Application filed July 8, 1911. Serial No. 637,503.

To all whom it may concern:

Be it known that I, WILL IBALD GRUN, a citizen of the German Empire, and a resident of Frankfort-on-the-Main, Germany, have invented certain new and useful Improvements in Turbine-Blades, of which the following is a specification.

My present invention relates to rotating turbine blades and has for its object to so construct them as to reduce or avoid the detrimental effects due particularly to the action of centrifugal force.

In rotary turbine blades as generally constructed with recesses at the inner portion or foot, the center of gravity of the root cross section of the blade (that is to say, the cross section of the blade at the point where it projects from the turbine wheel) is not located in the same radial line with the center of gravity of the outer blade portion or blade body, that is to say, the portion extending outwardly from the wheel. Owing to this unfavorable arrangement, the centrifugal force arising during the operation of the turbine will tend to bend the blades, the bending strain falling most heavily on the junction of the foot with the outer portion or body of the blade, and many blade fractures are due to this cause.

According to my present invention, the blades are inclined in such a manner that their concave or impact-receiving surfaces will form obtuse angles with the respective tangents to the wheel. This arrangement enables me to bring the center of gravity of the root cross section exactly or approximately into the same radial line with the center of gravity of the outer or body portion of the blade.

In the accompanying drawing, Figures 1, 2 and 3 are fragmentary views, with parts in section, showing three different constructions of blades embodying my invention.

The body of the wheel or rotor is indicated at g, and its center at f. The outer circumference of the wheel, at 6-0, indicates the plane of the root cross section of the blade, which has a notched portion fitted into the wheel body 9. The outer or bodyv portion of the blade receives the impact of the steam or other driving medium. I have not illustrated the details of-the manner of fitting the blades to the wheel, as any usual or approved construction may be employed. In the constructions illustrated by Fig. 1,

the center of gravity of the root cross section is indicated at 6, while d is the center of gravity of the body portion a. It will be seen that these two centers of gravity are located upon the same radius f, 6, cl. In

order to accomplish this result, the blades instead of being set radially as in ordinary practice (that is to say,at an angle of 90 to the periphery) are so arranged that their concave or impact-receiving surfaces (facing toward the left in the drawing) will form obtuse angles, as 90+oa, with the periphery,

that is to say, with the respective tangents to the wheels periphery.

The blade bodies a taper toward their outer ends. In the construction shown in Fig. 2, the blade bodies a are of uniform thickness, but otherwisethe arrangement is the same, that is to say, the concave impactreceiving front surfaces form obtuse angles with the respective tangents to the wheels periphery, or, to express it in a different way, the convex back surfaces form acute angles wit-h such tangents, and the two centers of gravity 6' and d are located on the same radius. With this arrangement of the two centers of gravity, the bending strain otherwise produced at the root cross section by the action of centrifugal force, is avoided entirely. Even when the two centers 0 gravity are only approximately on the same radius, a considerable advantage is secured over the usual construction, with radial blades, since the bending strain due to the action of centrifugal force is minimized.

During the operation of the turbine (which in the construction illustrated will rotate clockwise) the pressure of the driving medium on the blades will tend to bend them (clockwise) relatively to the root cross section. To counteract this tendency, the obtuse angle at which the blades are inclined to the wheels periphery may be increased ,(as shown in Fig. 3) so that the center of gravity 6 of the root cross section will be in the rear (to the left in the drawing) of the radius f, d which passes through the center of gravity 0? of the blade body of.

tend to bend the blade body contra-clockwise, that is to say, contrary to the bending act-ion due to steam pressure, and the two tendencies may be made to neutralize each other absolutely or approximately. It will therefore be understood that the useful result pointed out above is obtained whenever the two centers of gravity are in the same radial region, Whether actually or approximately on the same radius; thus it is not essential to my invention to bring the aforesaid two centers of gravity exactly into the same radial line, since the diminution or avoidance of bending strains is often attained even better if the center of gravity of the root cross section is slightly to one side of the radius passing through the center of gravity of the blade body.

Various modifications may be made Without departing from the nature of my invention as set forth in the appended claims.

I claim as my invention:

1. In a turbine, a rotor comprising a Wheel and blades carried thereby, the impact-receiving surfaces of the blades forming obtuse angles With the respective tangents to the periphery of the Wheel.

2. In a turbine, a rotor comprising a Wheel and inclined blades carried thereby, the center of gravity of the root cross sec tion of a blade and the center of gravity of the body of the same blade being located in the same radial region of the Wheel.

3. In a turbine, a rotor comprising a Wheel and inclined blades carried thereby, the center of gravity of the root cross section of a blade being in the rear of the radial line drawn through the center of gravity of the body of the blade.

In testimony whereof I have signed this specification in the presence of two subscriblng witnesses.

IVI'LLIBALD GRUN.

Witnesses JEAN GRUND, CARL GRUND.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). C.

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