阅读说明：本技术 一种叶轮机械动叶叶顶密封结构 (Impeller machinery movable vane top seal structure ) 是由 李辉 陈海生 朱阳历 李文 王星 于 2020-06-23 设计创作，主要内容包括：本发明公开了一种叶轮机械动叶叶顶密封结构,包括透平叶冠、密封齿和机匣,叶冠进气侧的第一个凸台周向连续无开槽,其它高台阶设置泵送槽/孔,槽口由排气侧至进气侧呈收缩状,并与转轴中心线成一定夹角,这样在叶片转动时间隙气流通过收缩状泵送槽/孔产生“泵送作用”,从而提高长密封齿出气侧的压力,以减小长密封齿间隙两侧的压差,起到减小泄漏的作用。为了减小叶顶间隙气体沿着开槽逆流升压时向叶顶方向泄漏,叶顶凸台开槽向叶顶方向为收缩形状,或者在凸台上设置开孔来替代开槽,这样可以起到更好的防止泄漏的效果。通过上述密封结构的应用,可以使叶顶间隙的泄漏量更小,从而减小透平的泄漏损失,提高机组的效率和经济效益。(The invention discloses a sealing structure of a movable vane top of an impeller machine, which comprises a turbine vane crown, sealing teeth and a casing, wherein a first boss at the air inlet side of the vane crown is circumferentially and continuously provided with no groove, other high steps are provided with pumping grooves/holes, and a groove opening is in a contraction shape from the air outlet side to the air inlet side and forms a certain included angle with the central line of a rotating shaft, so that clearance airflow generates a pumping action through the contraction-shaped pumping grooves/holes when vanes rotate, thereby improving the pressure at the air outlet side of a long sealing tooth, reducing the pressure difference at two sides of a clearance between the long sealing teeth and reducing the leakage. In order to reduce the leakage of the gas in the clearance between the blade tops to the direction of the blade tops when the gas is reversely pressurized along the slots, the slots of the lug bosses of the blade tops are in a contraction shape towards the direction of the blade tops, or the slots are replaced by the holes arranged on the lug bosses, so that the effect of better preventing the leakage can be achieved. Through the application of the sealing structure, the leakage amount of the blade top gap can be smaller, so that the leakage loss of a turbine is reduced, and the efficiency and the economic benefit of a unit are improved.)

1. A sealing structure for the top of moving blade in vane machine is composed of a moving blade wheel with a top ring-shaped turbine shroud, and a ring-shaped casing with several axially arranged and radially extended sealing teeth consisting of long and short sealing teeth,

a plurality of annular bosses which are arranged along the axial direction are arranged on the radial outer side wall of the annular turbine blade shroud, at least one short sealing tooth is arranged close to the top of each annular boss, at least one short sealing tooth is arranged between every two adjacent annular bosses and close to the radial outer side wall of the annular turbine blade shroud, so that a step labyrinth sealing structure is formed between each sealing tooth and each annular boss,

the number of the annular bosses is at least three, wherein a first annular boss is arranged close to the upstream high-pressure air inlet side of the movable blade impeller, a second annular boss is arranged between the first annular boss and a third annular boss, the third annular boss is arranged close to the downstream low-pressure air outlet side of the movable blade impeller, the first annular boss is of a continuous non-slotted structure along the whole circumference, a plurality of pumping grooves and/or pumping holes are uniformly arranged along the circumference of the second annular boss and the third annular boss, each pumping groove and/or pumping hole is of a contraction-shaped structure extending from the downstream low-pressure air outlet side to the upstream high-pressure air inlet side, and each pumping groove and/or pumping hole is obliquely arranged relative to the central line of the rotating shaft of the movable blade impeller.

2. The turbomachinery bucket tip seal structure of the preceding claim, wherein the root of each annular seal tooth is fixedly arranged on the radially inner side wall of the casing in an embedded manner.

3. The turbomachinery bucket tip seal structure of the preceding claim, wherein the bottom of each pumping groove and/or pumping hole is arranged directly opposite to the leakage gap of the long seal tooth.

4. The turbomachinery bucket tip seal structure of any preceding claim, wherein each said pumping groove and/or pumping hole is tapered radially outward in size in order to reduce leakage of gas flow in the groove in the radial direction during pumping.

5. The turbomachinery bucket tip seal structure of the preceding claim, wherein the channel exhaust direction of each pumping groove and/or pumping hole is as close to the axial direction as possible, so that the pumping airflow and the leakage flow form a hedging effect, and the pressure difference between two sides of the leakage gap is small, thereby achieving a better leakage prevention effect.

6. The turbomachinery bucket tip seal structure of the preceding claim, wherein the cross-sectional shape of the pumping groove comprises but is not limited to a rectangle, a wedge, a trapezoid, a circular arc or a curved shape, and the cross-sectional shape of the pumping hole comprises but is not limited to a circle, an ellipse, a hyperbola or a bezier curve, as long as the shape conducive to reducing leakage in the direction of the tip can be adopted.

7. The turbomachinery bucket tip seal structure of the preceding claim, wherein the pumping groove provided on the second boss is curved and contracted, and the pumping groove provided on the third boss is linearly contracted.

8. An impeller machine comprising an impeller machine bucket tip seal structure as claimed in any preceding claim.

Technical Field

The invention relates to a movable blade top sealing structure of impeller machinery, in particular to a combined sealing structure of a labyrinth and a spiral groove/hole of a turbine blade top.

Background

The labyrinth seal has the advantages that a gap exists between the rotor and the casing, the labyrinth seal is free of solid contact, lubrication is not required, the labyrinth seal is simple to maintain and long in service life, other sealing materials are not required, thermal expansion is allowed, and the labyrinth seal can adapt to occasions with high temperature, high pressure and high rotating speed frequency, so that the labyrinth seal is widely applied to blade top sealing and shaft sealing of equipment such as steam turbines, gas turbines, compressors and air blowers. The leakage amount of the labyrinth seal increases with the increase of the clearance value and the pressure difference before and after the seal.

The spiral groove seal has the greatest advantage that even if a larger gap exists between the sealing parts, an effective sealing effect can be achieved, and because the spiral groove has the pumping function, the damping of a leakage channel can be increased so as to reduce the leakage amount. If the spiral seal is designed reasonably, the service life of the spiral seal can reach infinity. Due to the wide choice of materials and the extreme ease of manufacture, the power consumption and heat generation of the screw seal are small when the pressure differential is not large. However, the spiral seal is greatly influenced by the rotating speed of the rotor, and when the spiral seal deviates from the designed rotating speed to a certain degree, the problem of seal failure exists.

In order to utilize the advantages of labyrinth seal and spiral groove seal at the same time, the invention provides a combined seal structure of a labyrinth of a turbine blade top and a groove/hole of a boss. By the combined application of the labyrinth seal and the spiral groove seal, the leakage loss of the turbine through the blade top gap is reduced, and the operation efficiency and the economic benefit of the unit are improved.

Disclosure of Invention

Aiming at the defects and shortcomings of the existing impeller mechanical movable blade top labyrinth seal and spiral seal technology, the invention provides an impeller mechanical movable blade top seal structure for further improving the impeller mechanical movable blade top seal effect and reducing the leakage loss through a blade top gap in a turbine. Through the application of the structure, the advantages of labyrinth seal and spiral seal can be comprehensively utilized, and the leakage of the blade top clearance and the flow loss are reduced, so that the efficiency and the economic benefit of the turbine are improved, and the application prospect is good.

In order to achieve the above object, the solution adopted by the present invention is as follows:

a sealing structure for the top of moving blade in vane machine is composed of a moving blade wheel with a top ring-shaped turbine shroud, and a ring-shaped casing with several axially arranged and radially extended sealing teeth consisting of long and short sealing teeth,

a plurality of annular bosses which are arranged along the axial direction are arranged on the radial outer side wall of the annular turbine blade shroud, at least one short sealing tooth is arranged close to the top of each annular boss, at least one short sealing tooth is arranged between every two adjacent annular bosses and close to the radial outer side wall of the annular turbine blade shroud, so that a step labyrinth sealing structure is formed between each sealing tooth and each annular boss,

the number of the annular bosses is at least three, wherein a first annular boss is arranged close to the upstream high-pressure air inlet side of the movable blade impeller, a second annular boss is arranged between the first annular boss and a third annular boss, the third annular boss is arranged close to the downstream low-pressure air outlet side of the movable blade impeller, the first annular boss is of a continuous non-slotted structure along the whole circumference, a plurality of pumping grooves and/or pumping holes are uniformly arranged along the circumference of the second annular boss and the third annular boss, each pumping groove and/or pumping hole is of a contraction-shaped structure extending from the downstream low-pressure air outlet side to the upstream high-pressure air inlet side, and each pumping groove and/or pumping hole is obliquely arranged relative to the central line of the rotating shaft of the movable blade impeller.

Preferably, the root of each annular sealing tooth is fixedly arranged on the radial inner side wall of the casing in an embedding manner.

Preferably, the bottom of each pumping groove and/or pumping hole should be arranged to face the leakage gap of the long seal tooth.

In the sealing structure for the blade top of the mechanical moving blade of the impeller, because the linear velocity of the turbine blade crown is very high, when the sealing structure of the pumping groove and/or the pumping hole is introduced into the labyrinth seal boss of the turbine blade crown, a very strong pumping pressure effect can be generated in the channel, the direction of the pumping flow in the channel is opposite to the main leakage flow direction, and the fluid outlet of the pumping groove and/or the pumping hole is over against the gas seal tooth leakage gap with the labyrinth seal low step, so that the pressure on the outlet side of the gap is increased, namely the pressure difference on two sides of the gap is reduced, the effect of reducing the leakage amount is achieved, the bottom of the pumping groove and/or the pumping hole is over against the leakage gap of the long seal tooth, and the damping effect is the best.

In the sealing structure for the blade top of the moving blade of the impeller machinery, the sealing teeth are embedded on the casing and form a step labyrinth sealing structure with the boss on the turbine blade crown. The high step pumping grooves and/or pumping holes are directly opposite to the throttling jet flow of the previous step, so that the damping effect and the bypass flow dissipation effect in the leakage cavity are increased. In order to reduce leakage, the first boss on the inlet side of the blade top is sealed continuously in the whole circle. The second boss on the air inlet side of the blade top is provided with a contraction-shaped pumping groove and/or a pumping hole which forms a certain angle with the central line of the rotating shaft, so that when the moving blade impeller rotates, the gap air flow generates a pumping action through the contraction-shaped pumping groove and/or the pumping hole, and a pumping pressure head is generated, thereby reducing the pressure difference on two sides of the gap between the long sealing teeth and reducing the leakage amount.

Preferably, each of said pumping grooves and/or pumping holes is tapered radially outwardly in order to reduce leakage of gas flow in the recess radially during pumping.

Preferably, the channel discharge direction of each of said pumping grooves and/or pumping holes is as close to axial as possible, so that the pumping air flow and the leakage flow have a counter-flushing effect, and the pressure difference between the two sides of the leakage gap is small, thereby achieving a better leakage prevention effect.

Preferably, the cross-sectional shape of the pumping groove includes, but is not limited to, a rectangle, a wedge, a trapezoid, a circular arc, or a curved line, and the cross-sectional shape of the pumping hole includes, but is not limited to, a circle, an ellipse, a hyperbola, or a bezier curve, as long as the shape is conducive to reducing leakage in the direction of the tip of the blade.

Preferably, the pumping grooves arranged on the second boss are in a curved contraction shape, and the pumping grooves arranged on the third boss are in a linear contraction shape.

Another object of the present invention is to provide an impeller machine including the impeller top seal structure of the present invention.

Compared with the prior art, the impeller top sealing structure of the impeller mechanical movable blade has the advantages and beneficial effects that: (1) because the linear velocity of the turbine blade shroud is very high, the pumping effect of the sealing of the pumping groove and/or the pumping hole is obvious, the effects of reducing the pressure difference at two sides of the sealing tooth gap and enhancing the air flow dissipation of the leakage chamber can be well achieved, and the resistance of the sealing tooth leakage channel and the damping of the leakage chamber are equivalently increased. Therefore, the combined sealing structure of the invention has less clearance leakage amount compared with the traditional labyrinth sealing structure. (2) The pumping grooves and/or the pumping holes formed in the boss of the blade shroud reduce the weight of the blade shroud, so that the centrifugal force load borne by the blade is reduced, and the deformation of the blade in the operation process of the unit is reduced, so that the thermal state blade top gap can be small in value, the gap leakage amount is reduced, the pneumatic efficiency of the system is improved, and the service life of the blade is prolonged.

Drawings

FIG. 1 is a front view of a bucket tip seal structure of a turbomachinery of the present invention;

FIG. 2 is a schematic three-dimensional structure of a tip seal of a moving blade of the turbomachinery of the present invention;

FIG. 3 is a top view of the turbomachinery bucket seal structure of the present invention;

FIG. 4 is a schematic of tip clearance leakage and "pumped flow";

FIG. 5 is a "pump flow" velocity triangle;

FIG. 6 is an axial cross-sectional view of a pumping groove/pumping hole wherein (a) is a rectangular pumping groove, (b) is a trapezoidal pumping groove, (c) is a circular pumping groove, and (d) is a constricted triangular hole;

in the figure: the turbine blade is characterized by comprising a casing 1, a seal tooth 2, a turbine blade crown 3, a first boss 4, a second boss 5, a third boss 6, a bent and contracted pumping groove 7 and a linear contracted pumping groove 8.

Detailed Description

In order to make the implementation objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, but not all embodiments of the invention. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The structure and technical scheme of the present invention are further described in detail with reference to the accompanying drawings, and an embodiment of the present invention is provided.

The embodiments of the present invention are shown in FIGS. 1 to 6. As shown in fig. 1, the blade tip sealing structure of the turbomachinery of the present invention mainly includes a turbine shroud 3 with a boss, a casing 1 (a stationary blade extension ring), and a seal tooth 2. The sealing teeth 2 are embedded on the casing 1 and the turbine blade shroud 3 with the boss form a traditional staggered step labyrinth sealing structure. Three bosses 4, 5 and 6 are arranged on the turbine blade shroud 3, wherein the second boss 5 and the third boss 6 on the air inlet side are circumferentially provided with slots, and the leakage through the blade top gap is reduced through the combined action of labyrinth seal and spiral seal, so that the efficiency and the economic benefit of the system are improved.

The three-dimensional schematic diagram of the combined seal shown in fig. 2 shows that the turbine shroud 3 is provided with three bosses 4, 5 and 6, wherein the first boss 4 is circumferentially continuous without gaps, and corresponding seal teeth are arranged above the bosses, so that the labyrinth seal blade tip leakage can be better reduced. The second boss 5 and the third boss 6 on the air inlet side are circumferentially provided with contraction- shaped pumping grooves 7 and 8 which are used as propulsion devices to exchange energy with media when the rotor rotates, so that a pumping effect is generated, a pumping pressure head is generated, the pressure difference on two sides of the long sealing tooth is reduced, the leakage of the blade tip is reduced, the bottom of the pumping groove/hole is opposite to the leakage gap of the long sealing tooth, and the damping effect is best.

In the top view of the combined seal shown in fig. 3, the second boss 5 on the air inlet side is a curved contracted slot 7, the third boss 6 is a linear contracted slot 8, the slot line type is not limited to the above, and may be linear or curved, and in any case, the optimal contracted line type should be selected according to the actual operation condition and working medium calculation.

FIG. 4 is a schematic tip clearance leakage and pumping flow diagram, with the pumping flow direction and leakage flow direction reversed. When the rotor rotates, the clearance airflow generates a pumping action through the shrinkage-shaped slot and generates a pumping pressure head, so that the airflow pressure at the gas outlet side of the long steam seal tooth can be improved, the pressure difference at the left side and the right side of the steam seal tooth is reduced, and the leakage is reduced. A part of leakage flow leaks towards the direction of the blade top under the action of centrifugal force in the boss contraction-shaped open groove, and the leakage flow can also play a role in increasing leakage damping for the leakage of the gap between the short steam seal teeth, so that the leakage flow is reduced to a certain extent.

The velocity triangle of the "pumped flow" shown in fig. 5 is influenced by the tie-up velocity U at the inlet of the flow, and the relative flow can effectively enter the slot to achieve the pressurization effect. In the pumping channel, the air flow speed and pressure in the channel are gradually increased under the influence of the channel on the action of the air and the gradual reduction of the space, the air exhaust direction of the channel is as close to the axial direction as possible, the channel and the leakage flow form a hedging effect, and meanwhile, the pressure difference between two sides of the leakage gap is small, so that the better leakage prevention effect is achieved.

Fig. 6 is a slotted axial cross-sectional view of the combination seal, wherein fig. 6(a) is a conventional rectangular slot. In order to reduce the leakage of the air flow in the slots to the blade tip clearance along the radial direction when the rotor rotates, the circumferential slots of the blade tip boss gradually shrink along the blade tip direction, and the shape of the circumferential slots is trapezoidal as shown in fig. 6(b) or circular as shown in fig. 6 (c). Or the boss is provided with a contraction-shaped hole along the axial direction, as shown in fig. 6(d), so that the leakage towards the blade top can be better reduced. The axial shape of the groove is not limited to the above-described shape, and may be an ellipse, a hyperbola, a bezier curve, or the like, as long as it is a shape useful for reducing leakage in the tip direction.

The object of the present invention is fully effectively achieved by the above embodiments. Those skilled in the art will appreciate that the present invention includes, but is not limited to, what is described in the accompanying drawings and the foregoing detailed description. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications within the spirit and scope of the appended claims.