CN108397237B - Composite winglet - Google Patents

Abstract

The present invention proposes a composite blade tip winglet, the structure of which includes setting a blade tip winglet on the suction surface side of the blade tip, and a plurality of shunt grooves on the blade tip surface; the blade tip surface includes the blade tip winglet and the original blade tip. The top two parts of the blade. The present invention retains the function of the conventional blade tip winglet for suppressing gap leakage, and forms a flow that intersects the flow direction of the blade tip leakage flow through the increased shunt groove on the blade tip surface, so as to reduce the leakage flow that directly crosses the blade tip from the pressure surface side. At the same time, the leakage flow is split into several strands through several shunt grooves with different outlet angles, and several leakage vortices with smaller strength are formed in the channel to reduce the mixing loss of the leakage flow and the low-energy flow on the suction surface side, thereby improving the impeller. performance.

Description

Composite tip winglets

technical field

The invention relates to a composite blade tip winglet. The invention is mainly installed on the top of a rotor blade, and is used for suppressing the leakage flow from the blade pressure to the blade suction surface side in the blade tip clearance area, so as to improve the performance of the impeller machinery; it belongs to the impeller. field of mechanical technology.

Background technique

Turbomachinery is an important mechanical equipment, widely used in aerospace navigation, energy power and other fields. It is the core component of aero-engine, gas turbine, supercharger, centrifugal pump and other equipment, and its performance restricts the overall performance of the equipment; impeller There is a certain radial gap between the rotor blade and the casing in the machine to accommodate the radial tensile deformation of the blade caused by the centrifugal load and thermal load when the impeller is working, but it also causes the blade pressure surface side to the suction surface side. The leakage reduces the pressure difference on both sides of the blade and reduces the working capacity of the impeller, and the mixing of the leakage flow with the low-energy flow on the suction side of the blade causes obvious mixing losses. Decrease; take the axial-flow turbine in conventional aero-turbine engines as an example, the current loss due to blade tip leakage accounts for more than 1/3 of the flow loss of the turbine stage, and for every 1% increase in the clearance size relative to the blade height, the turbine efficiency decreases by 1.5 %, and the engine oil consumption rate increases by 3%. Therefore, it is of great significance to seek suitable measures to suppress leakage flow in the gap to improve the performance of the turbomachinery, which is one of the current research hotspots in the field of turbomachinery.

The researchers proposed a variety of suppression measures for the leakage flow of the blade tip clearance. The more common ones are sealing grate teeth, blade tip winglets, blade tip processing, processing casing, and unsteady excitation. The sealing grate teeth have better performance. However, its structure is more complex and the manufacturing cost is high, so it is widely used in early aero-engines; and processing the casing and unsteady excitation requires huge additional equipment (additional pipelines and power supplies, etc.), sealing The sealing effect is poor and the practical applicability is not strong; the structure of the blade tip and blade tip treatment is relatively simplified, and it has been tried and applied in aero-engines, but its suppression effect on leakage is not as effective as grate seal. .

The tip winglet is a common measure to suppress tip leakage. Its main working principle is to reduce the driving pressure difference on both sides of the clearance area by increasing the length of the flow passage in the tip clearance area and increase the flow there. At the same time, the researchers also found that arranging the tip winglet on the suction surface of the blade can push the leakage flow to the middle of the channel farther away from the blade surface, thereby reducing the leakage flow Interacting with low energy flow on the suction side, this also reduces flow losses and improves impeller performance.

The tip winglet is a thin sheet structure with a shape similar to the blade profile but is wider, and is arranged at the top of the blade. In the current technical solution, the tip winglet is arranged on the suction side and the pressure side, as well as on the suction side and the pressure side. The larger blade tip increases the length of the flow passage in the tip clearance area, which not only increases the flow resistance in this area, but also reduces the pressure difference on both sides of the clearance passage, that is, reduces the The driving force of the leakage flow is reduced, and the leakage flow and leakage loss are reduced according to this principle; the increase of the width of the blade tip can effectively reduce the leakage flow, but it will cause additional friction loss. The width does not help the improvement of impeller performance; under the condition of small tiplet width, the simple flow channel structure does not have a significant effect on suppressing leakage loss. The current research results show that the tiplet can approximately improve the impeller efficiency. However, the blade tip winglet has a simple structure and low cost, and is especially suitable for small aero-engines, gas turbines and other equipment with small size and power. Therefore, the development of a simple and reliable structure with obvious suppression effect The unique tip winglet solution is very valuable for reducing tip clearance leakage and improving impeller performance.

SUMMARY OF THE INVENTION

The present invention proposes a composite blade tip winglet, the purpose of which is to better suppress the leakage of the blade tip clearance of the impeller machinery.

The technical solution of the present invention: a composite tip winglet, the structure of which includes setting a tip winglet on the suction surface side of the tip of the blade, and setting a number of shunt grooves on the blade tip surface; the blade tip surface includes a tip winglet and the top two parts of the original leaf.

Advantages of the present invention: The composite tip winglet proposed by the present invention retains the function of the conventional tip winglet to suppress gap leakage, and forms a flow that intersects the flow direction of the tip leakage flow through the increased shunt groove on the blade tip surface, reducing the The leakage flow that directly crosses the blade tip from the pressure surface side is small, and the leakage flow is split into several strands through several shunt grooves with different outlet angles, forming several leakage vortices with smaller strength in the channel, reducing the leakage flow and suction force Blending losses for low energy flows on the face side, thereby improving impeller performance.

Description of drawings

FIG. 1 is a schematic diagram of the structure of a composite tip winglet with a shunt slot.

FIG. 2 is a schematic diagram of the slotting position and direction of the shunt groove on the blade tip surface of the present invention.

Figure 3 is a schematic diagram of the block diagram of the conventional leakage flow by the jet in the distribution tank.

Figure 4 is a schematic diagram of the ejection and entrainment of the air flow in the gap area by the jet in the shunt and the block diagram of the conventional leakage flow.

FIG. 5 is a schematic diagram of the comparison between the leakage flow of the conventional tiplet scheme and the leakage flow of the tiplet with a splitter groove.

Detailed ways

A composite tip winglet, the structure of which includes setting a tip winglet on the suction surface side of the blade tip, and a plurality of shunt grooves on the blade tip surface; the blade tip surface includes the tip winglet and the top of the original blade. part.

The original blade refers to the rotor blade in the turbomachinery.

Composite tip winglets with shunt slots can be used to better suppress tip clearance leakage of turbomachinery.

The distribution groove is groove-shaped.

The composite tip winglet is installed on the suction surface side of the top of the rotor blade in the turbomachinery; the width of the composite tip winglet is 3% to 8% of the height of the rotor blade, and the height of the composite tip winglet is the rotor blade. 2% to 5% of the height, and within the range of 15% to 80% of the chord length of the rotor blade, 3 to 5 shunt grooves are arranged on the blade tip surface.

The direction of the shunt trough forms an included angle of 30° to 45° with the local blade mid-arc; when the impeller is working normally, at the inlet of the shunt trough, the high-pressure gas on the pressure surface side of the blade tip flows through these shunt troughs. To the suction surface side, a jet with a certain velocity is formed in the shunt groove, and the jet flow direction is at a certain angle with the flow direction of the conventional leakage flow, which is equivalent to forming several blocking zones in the main area where the leakage flow is generated (as shown in Figure 3). ); where there is no shunt groove on the blade tip surface, the high-pressure gas on the pressure side still flows across the blade tip to the suction side under the pressure difference, but it meets the jet in the shunt groove in the middle, and the jet has a certain effect on the leakage flow. The obstruction effect reduces the leakage flow of this part, and the leakage loss caused thereby is reduced.

The groove depth of the shunt groove is 50% to 80% of the thickness of the composite blade tip; the shunt groove on the blade tip surface is in the shape of a flow channel with a large inlet and a small outlet, so that the jet in the shunt groove forms an accelerated flow under the driving of the pressure difference. Ensure that the jet has a large kinetic energy at the outlet and can be far away from the suction surface of the blade to reduce the mixing loss with the low-energy flow on the suction surface side; Other fluids in the gap area form a certain ejection effect, and part of the air flow is drawn into the jet of the shunt slot, which strengthens the jet intensity, forms a better blocking effect on the leakage flow at the non-shunt slot, and reduces the leakage loss (as shown in Figure 4).

The outlets of different distribution grooves in the several distribution grooves form different included angles between 0° and 60° in the radial direction and the horizontal plane (as shown in the angle β1 in FIG. 5 , that is, the angle between the outlet plane of each distribution groove and the horizontal plane). In this way, after the airflow in each slot is accelerated, several jets with different directions will be formed at the outlet, which will be injected into different height positions of the blade channel respectively. Since the downstream leakage flow and the upstream leakage vortex are not at the same radial height, the upstream leakage The leakage vortex cannot form a strong entrainment effect on the downstream leakage flow, so its growth rate is slow, and finally several leakage vortices with small flow and weak strength are formed at different spatial positions of the blade channel (as shown in Figure 5). Then these small leakage vortices with weak strength will disappear quickly under the strong scouring of the mainstream, resulting in less mixing loss, so the performance of the impeller is improved.

According to the research results of conventional tip winglets, the tip clearance leakage flow mainly occurs in the range of 15% to 80% of the blade chord length, and the mixing of the tip clearance leakage flow and the low-energy flow on the blade side will form a strong leakage The vortex flow will cause large flow loss. Installing a blade tip winglet on the suction surface can push the leakage flow to the middle of the channel, reducing the mixing loss between the leakage flow and the low-energy flow on the suction surface side; at the same time, increasing the width of the winglet can increase the The flow resistance in the gap area can effectively reduce the leakage amount, but the friction loss in the gap area will increase at the same time, offsetting the gain brought by the reduction of leakage flow rate; therefore, the present invention adds a tip winglet on the suction surface side of the blade tip , in order to ensure the suppression effect of the blade tip and reduce the additional friction loss caused by the installation of the blade tip, the width of the blade tip is set to 3% to 8% of the blade height, and the height of the blade tip is set to 2% to 5% of the blade height, in order to effectively suppress the leakage flow of the blade tip clearance, 3 to 5 shunt grooves are arranged on the blade tip surface within the range of 15% to 80% of the blade chord length, and these shunt grooves are used to form and leak at the blade tip. The flow flows to several strong jets that intersect to block the leakage flow from the pressure surface to the suction surface, reducing this part of the leakage flow.

Generally speaking, the normal blade tip leakage flow is driven by the pressure difference on both sides of the blade to flow from the pressure surface across the blade tip to the suction surface side, and its flow direction is substantially perpendicular to the middle arc line of the blade. The present invention is arranged on the blade tip surface. In the diverter slot, in order to use the jet in the diverter slot to form a better blocking effect on the leakage flow from the pressure surface to the suction side, it is required that the flow direction in the diverter slot should intersect with the normal leakage flow. The direction of the shunt (that is, the centerline of the shunt trough) forms an angle of 30°~45° with the local blade mid-arc line (as shown in the angle α1 in Figure 2, that is, the local tangent of the shunt trough centerline and the blade mid-arc line. When the impeller is working normally, at the inlet of the shunt slot, the high-pressure gas on the pressure surface side of the blade tip flows to the suction side through these shunt slots, and a jet with a certain speed is formed in the shunt slot. The flow direction is at a certain angle with the flow direction of the conventional leakage flow, which is equivalent to forming several blocking zones in the main area where the leakage flow occurs (as shown in Figure 3). Driven by the pressure difference, it flows across the tip of the blade to the suction side, but meets the jet in the shunt groove in the middle. Losses are reduced.

In the present invention, the shunt groove arranged on the blade tip surface has a groove depth of 50% to 80% of the thickness of the winglet, which is equal to or slightly larger than the height of the blade tip clearance (the tip clearance of a conventional impeller is about 1% to 2% of the blade height). %), so that the intensity of the jet in the shunt slot can be equal to or even slightly larger than that of the conventional leakage flow, which can effectively block the effect; because the leakage flow and the flow into the adjacent blade channel are often mixed with the low-energy flow on the suction surface side of the blade tip Mixing causes losses. Studies have shown that pushing the leakage flow to the middle of the channel away from the blade surface can reduce this part of the mixing loss. Therefore, the tip shunt trough is designed to have a large inlet and a small outlet. Accelerated flow is formed under the drive of differential pressure, which ensures that the jet has a large kinetic energy at the outlet and can be far away from the suction surface of the blade, so as to reduce the mixing loss with the low-energy flow on the suction surface side; It can also form a certain ejection effect on other fluids in the gap area outside the shunt groove, draw a part of the air flow into the shunt trough jet, strengthen the jet intensity, and form a better blocking effect on the leakage flow at the non-shunt trough. Leakage loss (as shown in Figure 4); the groove depth is 50%~80% of the thickness of the winglet, so that the groove depth is equal to or slightly larger than the height of the tip clearance area, so that the flow in the groove has greater kinetic energy, ensuring that it is suitable for conventional The leakage flow has a significant blocking effect; at the same time, the inlet section of the shunt slot is larger than the outlet section, so that the airflow is accelerated in the slot, which can form an ejection effect on the airflow in the gap area outside the slot, enhance the flow strength of this part, and can Part of the fluid is pushed to the middle of the blade channel, keeping it away from the suction surface of the blade, reducing the mixing loss between the leakage flow and the low-energy flow on the suction side of the blade tip.

In a conventional tiplet, the flow direction of the tip leakage flow on the suction side is basically parallel to the blade tip plane, and the trajectory of the leakage flow entering the main flow channel is approximately a parabola, and the leakage flow on each suction side along the flow direction is basically in the same diameter. Therefore, the leakage vortex formed in the upstream continuously entrains the downstream leakage flow, so that the strength of the leakage vortex is continuously enhanced, resulting in a large mixing loss with the low-energy flow and the main flow on the suction side. Each of the shunt troughs, the outlet of which forms a different angle between 0° and 60° in the radial direction and the horizontal plane (as shown in the angle β1 in Figure 5, that is, the angle between the outlet plane of the shunt trough and the horizontal plane). After the airflow is accelerated, several jets with different directions will be formed at the outlet, which will be sprayed into different heights of the blade channel. Since the downstream leakage flow and the upstream leakage vortex are not at the same radial height, the upstream leakage vortex cannot affect the downstream leakage flow. A strong entrainment effect is formed, so its growth rate is slow, and finally several leakage vortices with small flow and weak intensity are formed at different spatial positions of the blade channel (as shown in Figure 5). The leakage vortex will disappear quickly under the strong scouring of the mainstream, resulting in less mixing loss, so the performance of the impeller is improved. The leakage flow in the tip clearance is split into several small flows in the space to reduce the mixing loss between the leakage flow and the low-energy flow on the suction side of the tip and the main flow area.

The invention provides a composite tip winglet technology for suppressing the leakage flow in the blade tip clearance area and improving the mechanical efficiency of the impeller. The tip winglets are arranged on the suction surface side of the blade top, and the tip winglets are arranged along the flow direction on the blade tip surface. ~ 5 diverter grooves, the high-pressure gas on the pressure surface side is introduced into the suction surface side through the diverter groove, and the fluid in the gap area is entrained at the same time. The leakage flow is kept away from the suction surface side of the blade tip, so as to reduce the mixing loss of the leakage flow and the low-energy flow near the suction surface and improve the impeller efficiency.

Claims (1)

1. a composite blade tip winglet is characterized in that the composite blade tip winglet is installed on the suction surface side of the rotor blade tip in the impeller machinery, and a number of shunt grooves are arranged on the blade tip surface; the blade tip surface includes a blade. The two parts of the tip winglet and the original blade tip; The shunt is groove-shaped; The width of the composite tip winglet is 3% to 8% of the height of the rotor blade, and the height of the composite tip winglet is 2% to 5% of the height of the rotor blade, within the range of 15% to 80% of the chord length of the rotor blade. 3 to 5 shunt grooves are arranged on the top surface of the blade; The direction of the shunt slot is at an angle of 30° to 45° with the mid-arc line of the local rotor blade; when the impeller is working normally, at the inlet of the shunt slot, the high-pressure gas on the pressure side of the blade tip flows to the suction force through the shunt slot On the surface side, a jet with a certain speed is formed in the split groove, and the jet flow direction is at a certain angle with the normal leakage flow direction, which is equivalent to forming several blocking zones in the main area where the leakage flow occurs; there is no split flow on the blade tip surface At the groove, the high-pressure gas on the pressure surface side is still driven by the pressure difference and flows across the blade tip to the suction surface side, but it meets the jet in the split groove in the middle. reduced, and the resulting leakage loss is reduced; The groove depth of the shunt groove is 50% to 80% of the thickness of the composite blade tip; the shunt groove is in the shape of a flow channel with a large inlet and a small outlet, so that the jet in the shunt groove is driven by pressure difference to form an accelerated flow to ensure that the jet flow is The outlet has a large kinetic energy, which can be far away from the suction surface of the blade, so as to reduce the mixing loss with the low-energy flow on the suction surface side; The fluid forms a certain ejection effect, and a part of the air flow is drawn into the jet of the shunt slot, which strengthens the intensity of the jet, forms a better blocking effect on the leakage flow at the no-shunt slot, and reduces the leakage loss; The outlets of different distribution grooves in the plurality of distribution grooves form different included angles between 0° and 60° in the radial direction and the horizontal plane, so that after the air flow in each distribution groove is accelerated, several jets with different directions will be formed at the outlet, which are sprayed separately. At different heights into the blade channel, because the downstream leakage flow and the upstream leakage vortex are not at the same radial height, the upstream leakage vortex cannot form an entrainment effect on the downstream leakage flow, so its growth rate is slow, and finally the difference in the blade channel is different. Several leakage vortices with small flow and weak strength are formed at the spatial position, these small leakage vortices with weak strength will disappear quickly under the strong scouring of the mainstream, and the mixing loss caused is also small, so the impeller performance is obtained. promote.

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