JPH0517361B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates generally to turbine blades and, more particularly, to the design of internal cooling passages for such blades. BACKGROUND OF THE INVENTION Gas turbine engines use hot gas from a combustor to drive a turbine. Gas is directed to turbine blades that are radially connected to the rotor. These gases have relatively high temperatures. Engine capacity is limited in large part by the ability of the turbine blade material to withstand the thermal stress caused by this hot gas. In order to reduce the temperature of the blades and thus improve their thermal performance, it is known to supply cooling air to hollow cavities inside the blades. Typically, one or more passageways are formed within the vane, supplying air through openings at the root of the vane and exiting through cooling holes strategically placed on the surface of the vane. Make sure you can go. Such a configuration is effective in providing convective cooling inside the vane and boundary film cooling on the surface of the vane. A variety of differently shaped cavities have been used to improve heat transfer to cooling air within the vane. For example, U.S. Patent No. 3,628,885 and
No. 4353679 describes an internal cooling system. One way to improve heat transfer is to provide a number of protruding ribs along the walls of the interior cavity of the vane. By creating turbulence near the ribs, heat transfer is improved. Traditionally, such turbulence-enhancing ribs have been placed at right angles to the cooling airflow. A device in which the ribs are oriented in this manner is described, for example, in US Pat. No. 4,257,737. One problem with using turbulence promoting ribs perpendicular to the airflow is that debris in the cooling air tends to collect behind the ribs. When dust accumulates in this way, heat transfer performance decreases. The turbulence-enhancing ribs also affect the pressure and flow rate inside the vane. The pressure of the cooling air when it exits the cooling hole is
The absolute condition is that the pressure be higher than the pressure of the hot gas flowing above the blade. This pressure difference is called the backflow margin. If the backflow margin is not maintained positive, cooling air will not flow out of the holes and hot gases may enter the blades through the cooling holes, thus shortening the life of the blades. In addition to the advantage of keeping the backflow margin positive, the high pressure exiting the exit holes has the advantage of imparting a relatively high velocity to the cooling air as it exits such holes. Most such holes have a downstream vector component, so depending on the magnitude of the air velocity, the mixing of the two air streams results in either less energy loss or greater energy gain. , thus improving the efficiency of the institution. To ensure that the outlet pressure is high enough,
Two conditions must be met. Firstly,
The pressure supplied to the inlet of the cooling air to the vanes must be high; second, the pressure drop between the inlet and the outlet must be low. This 2
The second condition, expressed as pressure drop or Δp, is proportional to the coefficient of friction inside the vane and the square of the flow rate. Δp is improved by decreasing the friction coefficient.
The coefficient of friction is also partially influenced by the shape of the walls of the cooling passages. For example, turbulence-enhancing ribs increase shear stress, thereby increasing the coefficient of friction by creating vortices behind the ribs. Thus, the turbulence-enhancing ribs improve heat transfer while at the same time worsening pressure drop. OBJECTS OF THE INVENTION It is an object of this invention to provide a new and improved means of cooling turbine blades. Another object of the invention is to provide a new and improved turbulence promoting rib within a turbine blade to reduce debris buildup. Another object of the invention is to provide new and improved turbulence promoting ribs within the interior of a turbine blade that reduce the pressure drop of the cooling air. Another object of the invention is to provide new and improved turbulence promoting ribs within the turbine blade to enhance heat transfer. Another object of the invention is to provide a new and improved turbulence promoting pin arrangement within a turbine blade to enhance heat transfer. Another object of the invention is to provide a new and improved molding core for turbine blades. It is an object of this invention to provide a new and improved molding core for turbine blades that has increased resistance to bending stresses. SUMMARY OF THE INVENTION In one form of the invention, a gas turbine blade having an internal cooling passage with two generally opposing walls has a plurality of integrally connected ribs. The ribs on one wall are disposed at a first angle relative to the centerline of that wall, and the ribs on the opposing wall are disposed at a second angle relative to the centerline of that wall. Each rib is separated into at least two rib members by a turbulence promoting gap. DETAILED DESCRIPTION OF THE INVENTION It should be appreciated that references to "turbine blades" in this specification include turbine stator blades, turbine rotating blades, as well as other cooled airfoil structures. FIG. 1 shows a shank 12 and an airfoil section 14.
1 shows a cross-sectional view of a turbine blade with . A plurality of internal passageways 16 conduct a flow of cooling air 17 within the vane 10 . Each passageway 16 is connected at one end to a cooling air inlet 18 within the shaft 12. A plurality of cooling holes 20 are provided at various locations along the passageway 16 near the other end. This kind of hole is passage 1
6 provides a flow path from the cooling air inside the vane to the gas flow outside the vane. A plurality of angled turbulence-enhancing ribs 22 are also shown inside the passageway 16. Note that the orientation of the ribs 22 in adjacent passageways 16 is generally the same. Thus, the swirl of the cooling air 17 is kept in the same direction as the cooling air flows from one passage to the next. Rib 22 is shown in more detail in FIGS. 2, 3, and 4. FIG. 2 is a cross-sectional view taken along line 2--2 in FIG. The rib 22 is the passage 16a, 1
6b, 16c, 16d, 16e, and 16f. Each of passageways 16a-16f has a unique cross-section, ranging from a roughly rectangular shape in passageway 16b to a near-trapezoidal shape in passageway 16d. Generally speaking, however, passageway 16 is generally quadrilateral and has two pairs of opposing walls. The first pair of opposing walls 24, 26 are generally aligned in orientation with the suction side 28 of the vane and the pressure side 30 of the vane, respectively. A second pair of opposing walls 32, 34 connect with walls 24, 26 to each form a passageway 16. FIG. 3 is a partial cross-sectional view of wall 24 taken along line 3--3 in FIG. FIG. 3 details the shape of the ribs 22 and their orientation relative to the centerline 38 of the passageway 16. each rib 22 extending between walls 32, 34 and being integral with wall 24;
has a roughly rectangular cross section. each rib 22
is oriented at a first angle α, measured counterclockwise from centerline 38 to rib 22. The value of α is 40°
and 90°, in one embodiment a value of 60°. Each rib 22 is divided by a gap 36 into rib members 22a and 22b. Adjacent ribs in the same flow path may have the same overall angular orientation, but the gaps 36 may be staggered about the centerline 38. FIG. 4 is a partial cross-sectional view of wall 26 taken along line 4--4 of FIG. FIG. 4 shows the orientation of rib 22 with respect to centerline 41 of wall 26. FIG. Each rib 22 is oriented at a second angle β measured clockwise from centerline 41 to rib 22. Preferably, the value of β is between 90° and 140°;
In one embodiment, the value is 120°. FIG. 5 is a partial cross-sectional view of wall 34. FIG. Ribs 22 extend from walls 24, 26, respectively. More specifically, rib member 22b extends from wall 24 to wall 34, and rib member 22c extends from wall 26 to wall 34. Each rib member 22b, 22c is substantially perpendicular to the direction of the centerline 39. In the illustrated embodiment, neither rib members 22b nor rib members 22c extend beyond the centerline 39 of wall 34. The aforementioned orientation of the ribs 22 on the wall 34 is the same for the ribs 22 on the wall 32. Specifically, in a preferred embodiment,
Rib members 22a and 22d are disposed on the wall 32 at right angles to the centerline of the wall 32, respectively.
4,26, but does not extend beyond the centerline of wall 32. FIG. 6 is a schematic diagram of the internal cooling passageway showing the shape of the ribs provided therein. The rib 22 provided on the wall 24 is similar to the rib 22 provided on the wall 26.
is not parallel to As previously mentioned, each rib 22 on wall 24 is at a first angle α with respect to a plane passing through centerline 38 and perpendicular to wall 24.
It is located in The angle α is measured counterclockwise from this plane toward the rib 22 when viewed from the pressure side 30. Each rib 22 on wall 26 is disposed at a second angle β with respect to a plane passing through centerline 41 of wall 26 and perpendicular to wall 26 .
The angle β is measured clockwise from this plane towards the rib 22 when viewed from the suction side 28. Alternatively, angles α and β may be measured clockwise and counterclockwise, respectively, from the aforementioned plane. walls 32, 34
The ribs 22 provided are substantially parallel. The invention is not restricted to the embodiments described above.
Various modifications are possible. For example, the gaps 36 between adjacent ribs 22 need not be staggered with respect to the centerlines of their passage walls. Furthermore,
Two or more gaps may be provided in each rib.
A gap may be provided at one end or both ends of the rib 22. FIG. 11 shows a cross-sectional view of another type of turbine blade 10 of the present invention. As shown in FIG. 11 and in more detail in FIG. 12, each rib 22 is divided into a plurality of rib members 23a, 23b, etc. by a plurality of gaps 36a, 36b, etc. Gap 36
a, 36b, etc., and the ribs 23a, 23
The minimum width such as b is determined by constraints during casting or molding. Instead of the quadrilateral rib members 23a, 23b, etc. shown in FIGS. 11 and 12, various other geometric shapes may be used. For example, FIG. 13 shows a circular pin 50 in place of the rib members 23a, 23b, etc. Each row of aligned but non-abutting pins 50 forms an array 52 of pins. Like the ribs 22, each array 52 is integral with the wall 24 or 26, each positioned at an angle α or β with respect to the centerline 38 or 41 of the wall 24 or 26. the orientation of the ribs 22 provided on the walls 32, 34;
Rib members 22a, 22 provided on these walls
Both lengths b, 22c, 22d are affected by molding constraints. For example, molding ceramic cores for molding typical turbine blades requires separating the core molds. Generally, the mold parts of the core are separated approximately along the separation line between the suction side 28 and the pressure side 30, so that in a plane perpendicular to the walls 24, 26, i.e., the walls 32, 34 If the rib mold has a recess, the recess must be parallel to the separation direction.
Furthermore, because the core mold is constructed of two parts that fit together, it is difficult to precisely cast a single rib on the walls 32,34. For this reason, the rib member 2
2b and 22c extend to just before the center line 39, which is also the separation line of the core mold. Another arrangement of ribs is shown in FIG. 7, which schematically shows the passageway 16. Ribs 22 are confined to walls 24, 26 and do not extend to walls 34, 32. rib 2
The extent to which 2 extends toward walls 32, 34 varies from no extension, as shown in FIG. 7, to full extension between these walls. It should be appreciated that the cooling air passages do not necessarily have to be rectangular in cross section. For example, a variety of cross-sections ranging from irregular quadrilaterals and triangular shapes to less well-defined shapes can be taken and are within the scope of this invention. FIG. 8 shows a typical molded molding core 40 used in manufacturing a turbine blade 10 such as that shown in FIG.
shows a side view. The composition of core 40 may be ceramic or any other known material. The angled ribs 22 are shown as angled grooves 42 in the face 48 of the tang portion 44 of the passageway.
The gap 36 appears as a wall 46 that interrupts the groove 42. Each rib 22 provided on the surface 48 is
The core portion 44 is disposed at a first angle relative to the centerline. Ribs 22 (not shown) on the surface opposite surface 48 are disposed at a second angle relative to the centerline of core portion 44 . By making the groove 42 at this angle and dividing it into two,
Core 40 is strengthened to provide greater resistance to bending stresses. FIG. 14 shows a side view of a molded molding core 56 that can be used to manufacture turbine blades having a pin arrangement as shown in FIG. Each pin 50 is shown as an aperture 64 in the face 58 of the channel core portion 60. Each array of pins appears as an array of holes 62 and is disposed at a first angle relative to the centerline of core portion 60 . A second set of hole arrays (not shown) are disposed on opposite sides of the core portion 60. Each of the second array of holes is
The opposing surfaces are disposed at a second angle relative to the centerline. To explain the operation, the cooling air 17
It enters the passage 16 at the shaft 12 of the turbine blade 10 shown in the figure. As this cooling air passes through cooling passage 16, it encounters angled turbulence promoting ribs 22. If there is debris in the cooling air 17, it will tend to be directed along the angled ribs and pass through the gaps 36 in each rib 22 so that it does not accumulate. After passing through passage 16, air 17 exits through cooling holes 20 and enters the gas stream. In order to incorporate the vane of this invention into an existing engine without otherwise modifying the engine, the flow rate through each vane using this invention must be the same as the current vane. Angled ribs 22 tend to increase the flow rate, thus reducing the diameter and/or number of cooling holes 20 to keep the flow rate constant. What is very important in blade design is the pressure drop △p
The aim is to keep the heat transfer rate as low as possible and to make the heat transfer rate as high as possible. This angled rib can be expected to improve Δp, that is, reduce it. Since Δp is proportional to the coefficient of friction, reducing the rib angle from 90° reduces flow resistance or friction and thus reduces Δp. The International Journal of Heat was improved by adding angled ribs to parallel plates.
Mass Transfer (International Jouranl)
This is described in the article ``Study of heat transfer and friction on surfaces roughened with ribs'' published in the Journal of Heat Transfer, Vol. 21, pp. 1143-1156. The results of this study are reproduced in Figure 9. By decreasing the rib angle from 90°, a decrease in heat transfer rate is also expected. FIG. 10 shows the empirical results of the above-mentioned research regarding the angle of the Stanton rib. Stanton number
Note that Number) is proportional to heat transfer. As the ribs are moved away from 90°, the heat transfer rate decreases. This degradation of effective cooling cannot be accommodated in the design of the vane. However, in tests conducted on the model of the present invention, improvements in both pressure drop as well as heat transfer rate were measured in contrast. This test is performed at 60° to the flow path.
This is a comparison of a model with ribs at an angle of , with no gaps, and a model with similar ribs at a 90° angle. Furthermore, we have a model with ribs with a 60° angle and a gap between each rib.
A comparison was also made with a model with no gap at 90°. The test results were surprising and unexpected. These results are summarized in the table below.

[Table] As is clear from this table, angles with gaps
60° ribs improve pressure drop by 4-10% and improve heat transfer by 12-20%. Additionally, debris that accumulates behind the ribs is expected to be reduced due to the gaps provided in each rib. It should be noted that the numerical range shown in this table represents test results conducted at different flow rates. Although there is currently no data for a pin arrangement of the type shown in FIG. 11, it is expected that heat transfer will be improved. Furthermore, virtually no debris is expected to accumulate. It will be apparent to those skilled in the art that the invention is not limited to the embodiments particularly shown and described. The present invention is not limited to the manufacture of turbine blades and molded cores thereof, but is also applicable to turbine vanes, turbofluid machines generally having internal cooling passages, and cores for manufacturing such articles. can also be used in the same way. The dimensions, proportions, and structural relationships shown in the drawings are exemplary only, and such illustrations should not be construed as actual dimensions, proportions, or structural relationships used in the turbine blades of the present invention. It goes without saying that various modifications can be made within the scope of the invention, but the invention is limited by the scope of the claims.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of one type of turbine blade of the present invention, Fig. 2 is a sectional view taken along line 2-2 in Fig. 1, and Fig. 3 is a section taken along line 3-3 in Fig. 2. 4 is a partial sectional view taken along line 4--4 in FIG. 2; FIG. 5 is a partial sectional view taken along line 5--5 in FIG. 2; FIG. FIG. 7 is a partial perspective view schematically showing an internal cooling passage of a turbine blade having one type of turbulence-promoting rib of the present invention, and FIG. 8 is a side view of the molding core for the turbine blade shown in FIG. 1; FIG. 9 is a partial perspective view schematically showing the internal cooling passages; FIG. Figure 10 is a graph showing the coefficient of friction for airflow between two parallel ribbed plates; Figure 11 is a graph showing the Stanton number as a function of the angle of approach of the flow for airflow between two parallel ribbed plates; 12 is a partial sectional view showing the wall of one passage of the blade of FIG. 11; FIG. 13 is a passage wall of another type of blade of the invention; FIG. A partial cross-sectional view showing
FIG. 14 is a side view of a molding core for a turbine blade having passage walls as shown in FIG. 13. Explanation of main symbols: 16... passage, 22... rib, 24, 26... facing walls, 36... gap.

Claims (1)

Claims: 1. A turbine blade having at least one internal cooling passage having first and second opposing walls and first and second turbulence promoting ribs, comprising:
a rib is integral with the first wall of the passageway and is disposed at a first angle with respect to a centerline of the first wall, and the second rib is integral with the second wall of the passageway. a second wall with respect to the centerline of the second wall;
and each of the first and second ribs is arranged at an angle of 2.degree.
A turbine blade consisting of two rib members. 2. In the turbine blade according to claim 1, the first angle is between 40° and 90°, and the second angle is between 90° and 140°. turbine blade. 3. In the turbine blade according to claim 2, the first angle is about 60°, the second angle is about 120°, and the gap between adjacent ribs of each wall is The turbine blades are arranged alternately on one side and the other side of the centerline of its wall. 4. Connect the first and second facing walls to the third and fourth walls.
A turbine blade having at least one internal cooling passage formed by four walls connected by a wall, and a plurality of first and second turbulence promoting ribs integral with the wall. the first rib extends from a centerline of the third wall at a right angle to the centerline of the third wall and subsequently at a first angle to the centerline of the first wall; extending across the first wall and subsequently to the centerline of the fourth wall, and the second rib extends perpendicularly to the centerline of the fourth wall; extending from the centerline of the third wall at a right angle to the centerline of the third wall and subsequently extending across the second wall at a second angle to the centerline of the second wall. , and then the fourth
two ribs extending perpendicularly to the centerline of the fourth wall to the centerline of the wall, and each first rib being separated by a gap provided on the first wall;
A turbine blade comprising two rib members, each second rib being comprised of two rib members separated by a gap provided on said second wall. 5. In the turbine blade according to claim 4, the first angle is between 40° and 90°, and the second angle is between 90° and 140°. turbine blade. 6. In the turbine blade according to claim 5, the first angle is about 60 degrees, the second angle is about 120 degrees, and the gaps between adjacent ribs are each about 60 degrees. Turbine blades are alternately arranged on one side and the other side of the centerline of the first wall and the second wall. 7. In a ceramic core used for forming a hollow turbine blade having at least one passage core portion having first and second opposing surfaces, the centerline of the first surface. a plurality of first grooves provided in the first surface at a first angle with respect to the first groove;
a plurality of second grooves provided in the second surface at a second angle with respect to a centerline of the second surface, the first angle being less than 90°; Second
A ceramic core whose angle is greater than 90°. 8. A ceramic core according to claim 7, wherein each groove is interrupted by a wall integral with the surface. 9. The ceramic core according to claim 8, wherein the first angle is 60° and the second angle is 120°. 10 at least one having first and second opposing walls and a plurality of first and second turbulence promoting ribs.
In a turbine blade having two internal cooling passages,
the first rib is integral with the first wall of the passageway and is disposed at a first angle relative to the centerline of the first wall; and the second rib is integral with the first wall of the passageway;
and is disposed at a second angle with respect to the centerline of the second wall, and is disposed at a second angle with respect to the centerline of the second wall;
A turbine blade comprising a plurality of rib members, each of the ribs being separated by a turbulence promoting gap. 11 in a turbine blade having at least one internal cooling passage having first and second opposing walls and an array of a plurality of first and second turbulence promoting pins; each of the arrays of pins is comprised of a plurality of aligned but non-butting pins, the first array of the plurality being integral with the first wall of the passageway; are disposed at a first angle relative to the centerline of the first wall, and the plurality of second arrays are integral with the second wall of the passageway, each of the plurality of second arrays being integral with the second wall of the passage. a turbine blade, wherein the array is disposed at a second angle relative to a centerline of the second wall. 12 A hollow body having at least one passageway tang portion having first and second opposing surfaces and having a plurality of first and second arrays of holes disposed therein. In a ceramic core used for molding a turbine blade, each of the first and second hole arrays is composed of a plurality of holes that are aligned but do not abut each other; Each of the first arrays of holes is disposed at a first angle relative to the centerline of the first surface, and each of the second arrays of holes is disposed at a first angle relative to the centerline of the second surface. Ceramic core placed at an angle of 2.