MX2008010091A

MX2008010091A - Gas turbine blade with internal cooling structure.

Info

Publication number: MX2008010091A
Application number: MX2008010091A
Authority: MX
Inventors: Alexander Khanin; Maxim Konter; Anton Sumin; Sergey Vorontsov
Original assignee: Alstom Technology Ltd
Priority date: 2007-08-08
Filing date: 2008-08-06
Publication date: 2009-02-27
Also published as: EP2025869A1; CA2638535C; CA2638535A1; TW200928075A; ATE491863T1; DE602007011256D1; EP2025869B1; SI2025869T1; TWI374214B; US20090041587A1

Abstract

A gas turbine rotating blade (1) comprises an internal cooling structure having at least three cooling air passages (5-7) in fluid connection with one another by means of turns (9, 10). An opening (12) provides an outlet for dissolved core material to be removed from the blade following casting of the cooling structure without any residue remaining within. According to the invention, the cooling structure comprises trip strips (13, 15) in the first and second passage (5, 6) with specified ratio of height to distance between trip strips and the trip strips (13) in the first passage being arranged at 90 DEG with respect to the direction of airflow. In a particular embodiment, the trip strips (15) in the second passage (6) are arranged at angle of 45 DEG . The design according to the invention assures sufficient airflow through first and second air passages (5, 6).

Description

TURBINE ASSEMBLY WITH INTERNAL COOLING STRUCTURE Field of the invention The present invention relates to melting rotating vanes for a gas turbine, and in particular to the design of an internal cooling structure within the vane in view of blade manufacture.

BACKGROUND OF THE INVENTION Turbine blades for gas turbines are designed and manufactured to withstand high temperatures during gas turbine operation. Such turbine blades comprise an internal cooling structure through which a cooling fluid, typically air, passes. The cooling air is typically expelled from a gas turbine engine compressor. This extraction of air, however, reduces the overall performance of the engine. In order to minimize the effect on engine performance by minimizing air consumption and even ensuring sufficient blade cooling, the internal blade cooling structure is designed for optimum cooling efficiency. Such designs are described, for example, in US 6,139,269 and US 5,403,159. US 6,139,269 discloses a serpentine cooling structure having several passages extending in the longitudinal direction of the blade and connecting to a REF. : 195334 entry opening in the blade root, to an opening in the exit at the blade tip, or to an additional longitudinal passage by means of a rotation or tilt of approximately 180 °. The cooling structure further comprises on the walls of the longitudinal passengers a multitude of movement bands, oriented at approximately 45 ° to the direction of flow through the passage. The particular construction in US 6,139,269 further comprises at each 180 ° turn near the blade root an air refueling passage that allows air to enter the passage from the blade root. Turbine blades with internal cooling structure of this type are fused, as a rule, by a coating melting process using a core that defines the cooling structure. The core is made of a material that can be leached such as ceramics. Following the molding process, the ceramic core is removed by a leachate process. The leachate process is difficult with respect to the removal of core material from the region of the 180 ° turns, and there remains a risk that the residual core material remains behind in the blade cooling channels and thus obstructs the flow of cooling media through the cooling passage. In order to reduce this risk, a opening in the wall of cooling structure in the region of 180 ° rotation so that the remaining core material is leached. In some known gas turbine blades, this opening is again closed by means of a plate or connector as described for example in US 6,634,858.

SUMMARY OF THE INVENTION It is the object of the invention to provide a rotating turbine of gas turbine with an internal cooling structure having a design that allows improved manufacturing over those of the state of the art while at least maintaining the existing cooling performance of the internal cooling structure. A rotating gas turbine blade comprises an internal cooling structure having at least three cooling passages extending in the longitudinal direction of the blade, at least one opening in the region of the blade root, and at least one exit opening in the region of the blade tip leading from a cooling passage outside the blade. The blade further comprises in its root region an intake chamber for cooling air, the inlet opening extending from this intake chamber to a cooling passage. The first cooling passage extends, in the direction of cooling fluid, from the root region of the blade to the Punta tip region. The second cooling passage extends from the tip to the root region. The first and second cooling passages are in fluid connection with one another in the region of the blade tip by means of an inclination or rotation in the region of the blade tip. The third cooling passage again extends from the root to the tip, while the second and third cooling passages are in fluid connection with each other by means of a twist or tilt in the region of the blade root. In order to remove a core material from the leach inclination with a reduced risk of core material remaining at the tilt, an opening is provided in the cooling structure wall extending from the intake chamber towards the tilt or turn in the blade root region from the second to the third cooling passage. The opening provides a direct fluid connection from the inclination towards the root of the blade and towards the outside of the blade. In particular, the opening and the root region of the blade is such that a liquid fluid is allowed to flow directly and essentially in the longitudinal blade direction away from the inner blade cooling structure. This allows the fluid core material to exit the blade completely without having to pass through none of the return turns or dead zones. In that way, it is prevented that the fluid core material remains in the structure as a residual fluid. This ensures the flow of cooling air through the internal cooling structure when the blade is in operation. For purposes of simplified manufacturing and thus efficient cost of the rotating turbine of gas turbine, the opening in the inclination or rotation of 180 ° of the internal structure does not close again prior to the operation of the blade in the turbine. Since the opening in the 180 ° turn has an effect on the aerodynamics of the internal cooling structure and the cooling air distribution, the design of the cooling passages is therefore adapted and optimized in view of the function and efficiency Cooling. According to the invention, the first cooling passage that extends, in the direction of the cooling fluid from the intake chamber in the root region towards the tip region of the blade, comprises a plurality of turbulence producers or bands of movement distributed at an angle of 90 ± 10 ° towards the direction of the cooling fluid flow. Additionally, the second cooling passage, in fluid connection with the first cooling passage through means of a turn, comprises a plurality of motion bands or turbulence producers. Finally, in combination with the specific orientation of the movement bands in the first cooling passage, the movement bands in the first and second cooling passages are distributed and have dimensions so that the relationship between their height and the distance between bands of Adjacent movement is 10 + 2. In an illustrative embodiment of the invention, the movement bands in the second cooling passage are distributed at an angle of 45 ° ± 10 ° with respect to the flow direction. In a further illustrative embodiment, the third cooling passage comprises a plurality of movement bands distributed at an angle of 45 ° ± 10 ° from a direction of flow towards the direction of the movement band. As mentioned above, the opening in the turn from the second to the third passage affects the distribution of cooling air in the cooling structure. In particular, an opening not connected at that location will result in a reduction of air flow from the intake chamber in the root region through the first and second passage and an increase in air flow from the intake chamber through the the opening directly towards the third passage. The design measures according to the invention in the form of a particular distribution of movement bands in the first and second passage allow optimization of cooling air flow and restoration of air flow through the first and second passage. With which ensures sufficient and uniform cooling of the complete blade. The design of the movement belts according to the invention allows compensation of very small hydraulic pressure losses from the start of the first passage towards the beginning of the third passage. The compensation of low pressure losses is achieved by pumping forces in the first and second passages due to an increase in convection temperature of the cooling air along these passages. The flow dynamics of the cooling air are elaborated in connection with the following figures. As mentioned above, the design of the blade cooling structure according to the invention allows optimized fabrication due to the opening provided in the turn near the blade root. The design does not require measurements that follow the casting to close the opening. The specific design of the movement bands in the cooling passages compensates the hydraulic pressure losses and thereby ensures sufficient cooling within the first and second passages. Therefore the design allows for improved and simplified manufacturing while maintaining cooling performance.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a side view of an illustrative gas turbine blade, to which the invention can be applied; Figure 2 shows a cross-sectional view of the blade of Figure 1 along II-II showing the internal blade cooling structure according to the invention; Figures 3a and 3b show, respectively, a cross section of the movement bands along Illa-Illa in Figure 2 and the bands of movement in detail, in particular the distribution and relative dimensions of turbulence producers in the first passage Cooling of the blade cooling structure; Figures 3c and 3d respectively show a cross section of the bands of movement along IIIc-IIIc in Figure 2 and the bands of movement in detail, in particular the distribution and relative dimensions of turbulence producers in the second passage of Cooling of the blade cooling structure.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a rotating gas turbine blade 1 extending longitudinally from a root 2 to a tip section 3.

Figure 2 shows the internal cooling structure of the blade having an intake chamber 4 within the root region for cooling air entering the cooling structure, a plurality of at least three longitudinal cooling passages 5-7 which they extend from the intake chamber 4 at root 2 to point 3 and from point 3 to root 2 respectively. The longitudinal passages are in fluid connection with each other by means of turns of approximately 180 °. The air flow passes, as indicated by the arrows, from the intake chamber 4 through an inlet opening 8 at the start of the first cooling passage 5 towards the end of the first passage at the tip of the vane, and around a turn 9 of approximately 180 °. It then flows along the second cooling passage 6 to an additional 180 ° turn 10 which connects the second cooling passage 6 with the third cooling passage 7. The cooling air finally flows through the third cooling passage 7 towards the tip of the blade and leaves the cooling structure through the outlet opening 11 at the tip of the blade. At turn 10 near the root of the blade, an opening or channel 12 is provided to leach core material after melting and allow all dissolved core material to run out of the cooling structure through the intake chamber 4 so that no core material remains in the turn 10. Due to this opening 12, the cooling air can more easily pass from the intake chamber 4 directly into the third cooling passage 7 instead through the first and second cooling passages 5 and 6. However, due to the particular design of the first and second cooling passages according to the invention, the pressure drop between position A and position B is such that a flow of cooling air is ensured through passages 5 and 6. A pressure loss is due to hydraulic resistance and depends on the square of the air velocity, the shape of the channel, the degree of smoothness of the passage walls as well as the form of turbulence producers or movement bands. All these characteristics according to the invention result in the fact that the air pressure at the position B at the start of the third passage 7 is lower than at the position A at the start of the first passage 5. In addition, a pumped effect occurs due to the rotation of the blade. Due to the pumped effect the air pressure increases with increasing radius of the passage, specifically in proportion to the difference of the squares of the spokes at a given angular velocity. At first passage 5 therefore, the pressure increases with increasing radius from position A to position B. In second passage 6, the pressure decreases with decreasing radius from position B to position C, which decreases by the same amount with which increased in passage 5. The final effect will therefore be zero. Additionally, however, a heat flux is collected by the cooling air from the heat convection walls of the passages that increase the temperature of the cooling air. As a result, the temperature of the cooling air in the second passage 6 is higher than in the first passage 5. This change in temperature also affects the pumped effect in the first and second passages. The upper temperature in the second passage results in that the pumpage effect along the second passage 6 is smaller than in the first passage 5. Therefore, the pressure in the position B is lower compared to that of the position in A, which results in an effective cooling air flow along passages 5 and 6. As mentioned above, the hydraulic resistance of a cooling passage depends, among others, on the design of the passage, in particular the design of turbulence producers or movement bands 13. Figure 2 shows an embodiment of the invention comprising in the first cooling passage 5 producers of turbulence or movement bands 13 distributed at 90 ± 10 ° in relation to the cooling flow direction, as indicated by the arrow. Figure 3a shows in cross-section the distribution and relative dimensions of the movement bands. Each of the movement bands has a height h measured from the wall 14 of the passage 5, and each movement band 13 is distributed at a distance d from the adjacent movement bands. The height h and the distance d are in a ratio of 10 + 2. Motion bands are shown by having a rectangular shape. However, it can also be any other form of aerodynamically suitable cross-section. Figure 3b shows the orientation of the movement bands in relation to the cooling air flow direction. The angle a is 90 ° ± 10 °. Figure 2 further shows the second cooling passage 6 having movement bands 15. Similarly as in passage 5, the movement bands 15 in passage 6 are designed to have a height h measured from the wall 16 of passage 6 and distance d between them so that the ratio of the height to the distance d is 10 ± 2, as shown in Figure 3c. The height h is measured from the wall of the passage, and the distance d is measured between adjacent moving bands along the cooling air flow direction.

The movement bands 15 in the cooling pge 6 as shown in Figure 2 are at a greater distance from one another compared to a distance between adjacent moving bands 13 in pge 5. However, the essential design features of the cooling pges in order to ensure an air flow of sufficient increase through pges 5 and 6 include the specific orientation of the movement bands in pge 5 and the height ratio h towards the distance d between bands of adjacent movement of 10 ± 2 for both pges 5 and 6. An additional design feature, which increases the effect includes the specific orientation of the movement bands in pge 6. The movement bands are distributed at a tilt angle ß of 45 ± 10 ° in relation to the direction of air flow, as shown in Figure 3d. The angle is measured in the counterclockwise direction from the direction of the movement bands to the direction of air flow. The third pge 7 may also have turbulence producers 7 of any design in order to increase the cooling efficiency along that pge. In the illustrative embodiment shown, the angle which is 45 ± 10 ° in relation to the direction of air flow is distributed at an angle of inclination d towards the direction of air flow.

Terms used in the figures 1 rotating blade 2 blade blade 3 blade tip 4 intake chamber for cooling air 5 first cooling air pge 6 second cooling air pge 7 third cooling air pge 8 inlet opening 9 turn 10 turn 11 opening output 12 exit opening for core material 13 movement bands in first pge 14 cooling pge wall 15 movement bands in second pge 16 wall of second cooling pge 17 movement bands in third pge h movement band height d distance between adjacent movement bands OI orientation angle of movement bands 13 ß orientation angle of movement bands d orientation angle of movement bands 17 A position at the start of the cooling pge 5 B position at the end of the cooling pge 5 C position at the inclination of the second pge 6 to the third pge 7 It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

Having described the invention as above, the claim contained in the following claims is claimed as property: 1. The rotating blade for a gas turbine comprising a blade root and a blade tip and an internal cooling structure comprising a first cooling air passage extending essentially in the longitudinal direction of the blade of an intake chamber of a blade root towards the blade tip, a second passage of cooling air extending from blade tip to blade root blade and a third passage of cooling air extending from the blade root to the blade tip, the first passage which is in fluid connection with the second passage by means of a first rotation and the second passage which is in connection of fluid with the third passage by means of a second rotation, and the cooling structure further comprises an opening extending from the second rotation towards the chamber of a duct that provides a direct outlet for fluids of the blade characterized in that the first and second passages of air each comprise a plurality of bands of movement, the bands of movement in the first cooling passage that are distributed at an angle of 90 ± 10 ° towards the direction of cooling fluid flow in that first passage, the movement bands in the second passage that are distributed at a 45 ° angle ± 10 ° in relation to the direction of air flow, and additionally, the bands of movement in the first and second passages have a height and a distance between adjacent moving bands, the relationship between the height and the distance that is 10 ± 2.
2. The rotating blade according to claim 1, characterized in that the third passage comprising a plurality of movement bands distributed at an angle of 45 ° ± 10 °.