US 2506581 A
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Description (OCR text may contain errors)
A. C. COWLES, JR
Isms FOR cbounc GAS TURBINE BLADES Filed June 30, 1945 Qwuvwkw Alba!) 0. Carlos, Jr
Patented May 9, 1950 Albon C. Cowles, In, United States Navy Application June 30, 1945, Serial No. 602,645.
(Granted under the act of March 3,'1883, as
amended April 30, 1928; 370 0. G. 757
This invention relates to turbine blades or vanes, and particualrly to gas turbine blades of the type in which a layer ofcool air is provided immediately adjacent the surface normally ex: posed to the extremely hot expanding gases prevent undue heating of those surfaces.
An object of the present invention is to 111-.
flow of cool air through the passageway 2 formed by' the spacing between the shields i and 1,
crease the eiliciencyof the gas turbine engine by.
decreasing the volume of excess cool air normally required to lower the temperature ofthe gases to which the turbine blades are exposed.
A further obj ect is toprovide gas turbine blades with a laminar flow of gases with a layer of cool air contiguous to all parts of thelexposed blade surfaces.
A still further object of this invention is to provide a turbine blade with one or more shields streamline in construction to enhance the free flow of gases wherein all surfaces, including those of the streamline shields, are. protected from the hot gases by. a layer of cool air. 1
These and other objects and advantages of the invention will be apparent from the following specification and taken with the accompanying drawing, wherein like numerals refer to like parts, inwhich: v
- Fig. 1 is a radialsection of l-i of F18. 2;
Fig. 2 is a section taken along the line 2-2 of Fig. 1;
a turbine blade and -a portion of the blade support taken along line Fi 3 is a section taken along the line 3-: Fig.1;
through the passageway 8 formed by the-spacing between, the parts 6 and I of the shield I, and through the passageway alongside and over the "mainsection I of the turbine blade, as shownby the arrows. .Also, cool air will flow along the'outside surface of the shield through the passageway ll formed by the spacing between the shield I and the frame ll of the turbine. The bottom portion of the shield 5 is of scoop shaped construction consisting of a lip or projection l2 extending in a direction of rotation of the turbine rotor, and'has a curvilinear passageway I2 to permit a free flow of air scooped up by the lip l3 through'the various aforementioned passageways. ;In order to lighten the weight of each of the-shields 5, a part of the unexposed portion of same which rests against the base portion 2 of the turbine blade may be recessed, as shown in Fig. 2. The shields 4 and 5 are bolted or preferablywelded to the base portion 2 of the turbine .blade prior to positioning of the blade'on the operating gases.
the'turbinerotor so that when assembled, the' top portions of theadjacent shields 5 form an annulus and will provide a smooth surface to The flow of air through and around the shields and the turbine blade is shown in the drawings, by the arrows thereon. As can be seen, all the exposed surfaces, and especially the surface of the main section of blade I, will be protected by a layer of cool air. Because of Fig. 4 is a radial section through another cmbodiment showing a single streamline shield; and
Fig. 5 is a section taken along line 5 -5 .of
I"! .4. is shown'by Figs. 1 and 3 inclusive, the nu meral l refers to a main section of a turbine blade' having a base portion 2 which is fitted tightly into an opening in the periphery of a turbine wheel 3 so as to be wedged securely therein in a manner well known in the art. A plurality of shields l and 5, spaced apart to form a passageway 9 and streamlined in construction so as not to affect the normal flow of the hot expanding gases nor to reduce the reactive forces of these gases, are welded or otherwise secured to the base portion 2 to forma unitary construction. The shield 4 consists of two parts, 6 and I, spaced from each other to form a passageway 8,
overlapping at their end portions and being joined along their trailing edges and spaced from the main section I of the turbine blade along both sides of same. This construction permits the free a a Each shield 20 is welded at its lowermost portion at its trailing edge to the side wall of thebase 2 of the turbine blade, or bolted thereto as the'streamlined shape of the shields l and I, there will be a smooth and even flow of'cool air which will have little tendency to mix with the hot ex,- panding gases, but will instead form a protective layer of cool air.
Figs. 4 and 5, which show a modification of the invention, include only a single streamline shield 20, constructed as anannulus so that each of the turbine blades is provided with a shield.
shown, to form the air passageway 2 I. The trailing edge of the shield 20 above the base 2 of the turbine blade is spaced therefrom'to form pas-- 'sageways. for cooling air.
turbine is spaced from the shield 20 to form another air passageway 22. In this modification,
' all of the turbine blades are first assembled-onto the rotor wheel and the annulus carrying the shields 20 bolted or welded thereon. Cool air flows then through the passageway 22 to provide the outer surface of the shield 20 with a layer The frame 22 of theor coolair, and also-through the passageway in.
alongside and, over the main section I of the turbine blade to completely envelope the same- Wifll laminar flow of cool air. 1 Asindicated by the arrows shown in mg drawing, a relatively small volume of airis permitted to flow to the base of the turbine blade and diverted through a plurality of passageways formed by thestreamlined shields. The various exposed surfaces are maintained at a temperature lower tha'n'that of the not operating gases by; the layer of cool air flowing along the exposed surfaces.-
This results in a marked increase in the efliciency inthe performance of the turbine and a drop in the percentage of failuresof' turbine blades due 2. In: a turbine blade air-cooling means, a pinrality of streamlined overlappingshields extending outwardly from the base of each blade, following substantially the contour around the forwardedge of said-blade or of .the inner portion of an overlapped shield, and closely approaching said blade or'said portion at their outer edges to distribute cooling air' supplied at the base of the blades in a laminar fashion over the surfaces of said blade and said overlapped shields, and means for directing cooling air from said air supplied at the base over the innermost shield.
to warping and breaking causedby the intense heat of those gases. Since theloperating gases are hottest at the primary stages and decrease in temperature in the succeeding stages. the passageways formed by the shields on the blades of the primary stages may be large and 'may decrease in size inthe succeeding stages. I While the forms'of mechanism herein shown 4 3. A turbine blade construction comprising a turbine blade, a base therefor adapted to be fitted into a turbine wheel and an open-ended shield overlying the forward portion of saidblade in spaced relation thereto and mounted on said base for distributing cooling air supplied at I the .base of the blade in a laminar flow over the and described constitute the preferred forms of embodiment of the present invention, it is understood that other forms might be adopted, all coming within the scope of the claims which follow. The inventiondescribed herein may be manufactured and used by or for the Government of the United States of' America for governmental purposes without the thereon or therefor.
What I claim is: 1
. 1. In a turbine blade air-cooling means, a plurality of streamlined overlapping shields extendpayment of any royalties ing outwardly'from the base of each blade, following substantially the contour around the forward edge of. said blade or of the inner portion of an overlapped shield, and closely approaching said blade or said portion at their outer edges to distribute cooling air supplied at thebase of the blades ina laminar fashion over thelsurfaces of said bladeand said overlapped shields.
surface of said blade, said open-ended shield being a substantially U-shaped member having two sections spaced from each other,-overlapping at .end
portions and being Joined along'their trailingj edges. v v
I l Remittances-"siren I The following. references are of record in the file of this patent:
Germany Jan 5, 1922