KR20120084888A - Rotor blade of gas turbine - Google Patents

Abstract

PURPOSE: A design for optimizing a winglet for a tip of a gas turbine flow is provided to improve turbine efficiency by reducing pressure losses caused by a tip clearance vortex. CONSTITUTION: A winglet for a tip comprises a unit for preventing pressure losses. A gas turbine flow is formed into a ring shape. The unit for preventing the pressure losses is the winglet protruded toward the outside of a diameter direction from a pressure side. A longitudinal section of the winglet is formed into tetragonal and triangular shapes, which are gradually thin.

Description

Optimal Design of Tip Blade for Turbine Rotor Flat Tip of Gas Turbine {Rotor blade of gas turbine}

The present invention relates to a gas turbine, and more particularly, to a blade rotor blade tip of the turbine turbine of the gas turbine having a function of providing a winglet at the end of the turbine rotor to effectively prevent pressure loss. Is about design optimization.

A gas turbine engine is typically a device that burns compressed air from a compressor in a combustion chamber and then powers it from this hot, high pressure combustion gas in a turbine (FIG. 1A). This engine is mainly used for combined cycle power and propulsion of aircraft. The turbine has several turbine stages consisting of stator vanes and rotor blades, and the efficiency of the turbine is closely related to the pressure loss at each turbine stage. In particular, unlike the turbine stator fixed to the casing, the turbine rotor as shown in Figure 1b has to rotate at a high speed, so that a tip gap that allows relative movement between the tip portion and the casing gap) exists. As can be seen in FIGS. 2 and 3, due to the pressure difference between adjacent airfoil passages, a strong secondary flow occurs through the tip gap from the pressure surface side of the airfoil to the suction surface, which causes the flow to tip. This is called tip-leakage flow. This tip leakage flows through the tip clearance and moves downstream along the suction surface in a spiral fashion. Three-dimensional flows, such as tip-leakage vortex, which occur near the tip gap, significantly increase pressure loss and reduce turbine stage efficiency. The pressure loss due to this tip leakage flow increases in proportion to the leakage flow rate, which is known to account for about 30% of the total pressure loss. This leakage flow rate is generally proportional to the tip clearance height.

2 shows an example of tip gap leakage flow for a plane tip. As can be seen in Figure 2, there is a very complex three-dimensional flow inside the tip gap by a pair of tip gap vortex and the separation / reattachment of the inflow flow. The flow entering the tip gap near the upstream pressure side tip edge approaches the casing parallel to the pressure side as in FIG. 3. This flow is divided into a leakage flow and a passage flow based on a stagnation line. Leakage flows through the peeling / reattaching from the edge of the pressure plane to the adjacent airfoil passages, and in the form of a jet of leakage, reaching the leakage flow separation line. This leakage flow develops into a tip leakage vortex, interacting with the main flow in the cascade passage. Passage vortex is created by developing a pressure-side leg downstream of a horseshoe vortex created at the leading edge upstream end wall boundary layer. If there is a tip gap, this passage vortex is located below the tip leakage vortex, which rotates in opposite directions and moves downstream (FIG. 3). The leakage flow through the tip gap depends on the position of the stagnation line located upstream of the pressure plane, and the leakage flow increases as the stagnation line moves away from the pressure plane. Since the pressure loss due to tip leakage is proportional to the leakage flow rate, it is necessary to reduce the leakage flow rate to reduce the pressure loss. Therefore, in order to reduce the pressure loss due to tip leakage, (i) effective blocking of the flow between the stagnation line and the pressure surface, and (ii) reduction of leakage flow through the tip clearance near the airfoil, caused by tip clearance vortex It is necessary to reduce the pressure loss and, at the same time, (iii) inhibit the development of passage vortices near the suction surface.

A winglet is a small wing installed at the tip of the aircraft main wing to reduce the drag force of the aircraft. It was first proposed by NASA Dr. Whitcomb in the mid-1970s and is now mounted on the main wing of many aircraft. The shape of this tip blade is very diverse, and FIG. 4A shows one example.

If there is no tip blade, there is a strong wing tip vortex at the tip of the main blade, as seen in the left wing of FIG. 4b. This vortex is created by the pressure difference between the pressure surface of the high pressure wing and the suction surface of low pressure. Wing tip vortices are developed by the interaction between the upwash flow due to this pressure difference and the free flow approaching the wing, which is similar to the tip leakage vortex generated by the interaction between tip leakage flow and main flow in the turbine passage. Comparing this main rotor tip flow region with the turbine rotor tip region, the tip of the aircraft main rotor tip is infinitely large.

As can be seen in the right wing of Figure 4b, when the tip blade is mounted on the main blade, the strength of the wing tip vortex becomes very weak. When the tip blade is installed at the tip of the aircraft main wing, the pressure difference between the top and bottom of the wing is maintained at the wing tip by the vertical tip blade, so (i) the reduction of lift force of the wing due to unloading near the tip is eliminated, (ii) The wingtip vortex is greatly reduced, resulting in less drag.

In turbine rotor blades, the leakage flow increases in proportion to the tip clearance. This increase in leakage flow increases pressure loss and tip surface thermal load, so it is necessary to keep the tip clearance to an acceptable minimum. To improve the performance of a turbine with a constant tip clearance, the turbine rotor tip shape should be designed to reduce tip leakage flow. Applying the above mentioned tip vanes to the turbine rotor tip and optimizing its shape will greatly increase the turbine's stage efficiency. As can be seen in Figures 2 and 3, the leakage flow is introduced into the tip gap beyond the front edge of the airfoil and the pressure surface edge. This inflow flow is continuously supplied from the flow moving toward the tip along the pressure surface of the airfoil as shown in FIG. Therefore, if the tip vane can be used to effectively block this flow across the airfoil and pressure plane of the airfoil, the leakage flow will be greatly reduced.

In general, a cascade in which turbine blades are arranged in a pitch direction is defined as shown in FIG. 5. c is the chord length, b is the axial chord length, p is the pitch, s is the span, and h is the height of the tip gap. Figure 6 shows the general shape of the tip vane installed on the turbine rotor blade tip. The area marked in blue represents the range of tip blades, w is the width of the tip blades, t is the tip blade thickness, and d is the offset distance from the tip surface to the top of the tip blades. To optimize the shape of this tip blade, it is necessary to find the range, width, offset distance, thickness, and cross-sectional shape of the tip blade to minimize tip leakage pressure loss.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a configuration of a new turbine rotor blade to prevent the pressure loss is increased by the three-dimensional flow, such as tip leakage vortex of the airfoil. .

In order to achieve the above object,

In the turbine rotor blades of the gas turbine arranged in an annular shape,

A pressure loss preventing means for alleviating pressure loss is provided on the tip upper end side disposed opposite the tip of the turbine rotor blade.

According to the present invention, it is effective in blocking the flow between the stagnation line and the pressure surface, and reducing the pressure loss caused by the tip gap vortex through the reduction of the leakage flow introduced through the tip gap near the airfoil, thereby affecting the turbine rotor performance. The main advantage is that large improvements in the turbine efficiency are effectively implemented.

1A is a schematic internal structural diagram of an apparatus for obtaining power from combustion gas of high temperature and high pressure.
1B is a perspective view of a turbine rotor blade rotating at high speed.
2 shows an example of tip gap leakage flow for a plane tip.
Figure 3 shows an example of approaching the casing parallel to the pressure plane in the flow entering the tip clearance near the upstream pressure plane tip edge.
FIG. 4A is a diagram illustrating an example of a tip wing installed on the main wing of most aircraft. FIG.
4b is a diagram showing an example in which there is a powerful wing tip vortex at the tip of the main wing as shown in the left wing when there is no tip blade.
5 is a plan view and side view of a cascade in which turbine airfoils are arranged in a pitch direction.
6 is a view showing a general shape of the tip blade installed on the turbine rotor blade tip.
7 is a result of setting the tip gap, the tip blade width, the thickness, the offset distance, and the like, and measuring tip leakage pressure loss with respect to various candidate shapes of the tip blade.
8 is a result of measuring the effect of the tip blade width on the tip leakage pressure loss with respect to the optimum shape tip blade "FL".
FIG. 9 shows the offset distance d for the optimal tip-swing FL with h / c = 2.0%, w / p = 10.55%, and t / s = 1.25%, respectively. Shows the effect on tip leakage pressure loss.
FIG. 10 shows the tip blades, the tip blade width, the offset distance, and the like for the optimum tip blade FL with h / c = 2.0%, w / p = 10.55%, and d / s = 0.0%, respectively. It is a graph showing the effect of thickness ( t ) and cross-sectional shape on tip leakage pressure loss.
11 is a graph showing a result of a smaller pressure loss when the bottom surface of the tip blade is inclined.

Hereinafter, the configuration of the present invention will be described with reference to the accompanying drawings.

A turbine rotor of a gas turbine arranged in an annular shape according to the present invention has been designed as part of an optimization design technique in which pressure loss preventing means for mitigating pressure loss of the turbine rotor is provided.

Here, the pressure loss preventing means is a tip vane that protrudes radially outward from the pressure side of the turbine rotor blade, which will be described in detail later.

First, Figure 7 is fixed to the tip gap, tip blade width, thickness, offset distance, etc. h / c = 2.0%, w / p = 10.55%, t / s = 1.25%, d / s = 0.0%, respectively The tip leakage pressure loss was measured for various candidate shapes of the tip tip. In the name of each tip blade, "P" means pressure side, "S" means suction side, "LE" means forward, "TE" means backward, "1" means upstream and "2" means downstream. Indicates. When the tip vane is present in all parts of the airfoil, the tip vane is named "LEP12S12TE", in which case it is specifically named "FL" (Full-Length) (FIG. 7C).

As can be seen in Figure 7, the pressure loss in the case of no tip tip ("No Winglet") of the various candidate shapes is the largest. According to FIG. 7A, the pressure loss was smaller in the case where the tip vanes were simultaneously provided on both sides ("P12S12") than when the tip or suction surfaces were installed. Looking at the results of Figure 7b, any tip blades including airfoil ahead of the pressure loss was greater than "P12S12". As can be seen from FIG. 7C, the pressure loss was smaller as the range of the tip tip was wider, and the pressure drop of the tip tip FL was the smallest among all candidates in FIG. 7. Thus, the "FL" ("LEP12S12TE") tip-sock, which has tip-socks on all parts of the airfoil, is the optimal shape.

The tip blade tip optimum shape mentioned in FIG. 7 is a result obtained by fixing the tip blade width to w / p = 10.55%. 8 is a result of measuring the effect of the tip blade width on the tip leakage pressure loss with respect to the optimum shape tip blade "FL". At this time, tip gap, tip blade thickness, and offset distance were fixed at h / c = 2.0%, t / s = 1.25%, and d / s = 0.0%, respectively. As a result, the pressure loss tends to decrease as the tip blade width increases, but the pressure loss no longer decreases when w / p exceeds 10.55%. Therefore, there is no reason to adopt a tip profit with a w / p greater than 10.55%, so that the width of the tip gain is approximately 10% of the pitch, which is the optimum tip gain.

For the optimal tip-soil FL, where the tip clearance, tip thickness, and width are h / c = 2.0%, w / p = 10.55%, and t / s = 1.25%, respectively, the offset distance d is the tip leakage. The effect on pressure loss is shown in FIG. 9. According to FIG. 9, as the d / s increases, the pressure loss increases rapidly. Therefore, it can be seen that the pressure loss is smallest when d / s is 0.0%, that is, when the tip surface and the tip blade top are coplanar.

Respectively, the width, the offset distance of the tip clearance, wing chancel ripening h / c = 2.0%, w / p = 10.55%, d / s = 0.0% in respect to the optimum ripening chancel ripening FL, wing thickness (t of chancel ripening ) And the effect of cross-sectional shape on tip leakage pressure loss is shown in FIG. According to the result of FIG. 10, the pressure loss was further increased when t / s was large, and the pressure loss was smaller when the lower surface of the tip blade was inclined.

Respectively, the width, the offset distance of the tip clearance, wing chancel ripening h / c = 2.0%, w / p = 10.55%, d / s = 0.0% in respect to the optimum ripening chancel ripening FL, wing thickness (t of chancel ripening ) And the effect of cross-sectional shape on tip leakage pressure loss is shown in FIG. According to the result of FIG. 11, the pressure loss was further increased when t / s was large, and the pressure loss was smaller when the bottom surface of the tip blade was inclined.

Based on the tip leakage pressure loss measurement results described above, the optimum tip-sink shape for the turbine rotor plane tip as shown in FIG. The optimal tip vane is arranged in a uniform width over the entire circumference of the rotor, with the optimum tip vane width being approximately 10% of the pitch. The tip tip thickness should be as thin as possible, around 1.25% of the span. The tip tip tip is coplanar with the tip surface and the bottom tip is inclined so that the tip tip tip thickness is minimal. To be

Role of each part

The front edge of this optimum tip blade serves to weaken the tip gap vortex (FIG. 2) by reducing the flow rate entering the tip gap beyond the tip edge. The pressure side reduces the flow rate of tip leakage entering the tip clearance beyond the tip edge edge, thereby reducing the pressure loss in the tip leakage vortex region. The tip side suction on the suction side prevents the development of passage vortices by blocking the pressure leg of the horseshoe vortex, which occurs at the hub tip of the adjacent airfoil and moves toward the suction side, thereby reducing the pressure loss in the passage vortex region. Let's do it. This function is most effective when the tip blade width is about 10% of the pitch. The thicker the tip tip, the greater the pressure loss due to the unnecessary blockage of the inflow and the expansion of the wake wake downstream.

The tip vane according to the present invention diverges radially outward from the pressure side of the turbine rotor and increases the resistance to the flow of combustion gas utilizing a tip shroud clearance.

In the pressure loss measurement, the turbine rotor performance is influenced by the turbine rotor performance for the state with the tip-side vane having a rectangular cross section (see FIG. 10) and the state with the tip-side vane having a triangular cross section (see FIG. 11). A great improvement in efficiency can be achieved, too, and so on.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

10: turbine rotor blade
20: tip-sided

Claims (7)

In the turbine rotor blades of the gas turbine arranged in an annular shape,
A tip rotor blade for a turbine rotor plane tip of a gas turbine, characterized in that a pressure loss prevention means for alleviating pressure loss is provided on the tip top side of the turbine rotor blade.
The method of claim 1,
The pressure loss prevention means,
A tip rotor blade for a turbine rotor plane tip of a gas turbine, characterized in that the tip rotor blade protruding radially outward from the pressure side of the turbine rotor blade.
The method of claim 2,
The tip blade tip, the blade blade tip blade for the turbine rotor blade tip of the gas turbine, characterized in that the longitudinal section of the tip blade.
The method of claim 2,
The tip blade tip, the blade rotor blade tip blade tip for the turbine turbine of the gas turbine, characterized in that the longitudinal section of the thinner the thinner end surface going to the tip.
The method according to claim 3 or 4,
A tip rotor blade for a turbine rotor blade tip of a gas turbine, characterized in that the width of the tip blade blade is 10% of the pitch.
The method according to claim 3 or 4,
In the tip vane, the width and the offset distance of the tip vane, the blade tip for the turbine rotor plane tip of the gas turbine, characterized in that optimized at w / p = 10.55%, d / s = 0.0%, respectively.
The method of claim 2,
The tip blade tip blade rotor blade tip for the turbine turbine of the gas turbine, characterized in that formed extending over the upper front and outer peripheral surface of the rotor blade.

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