Miniature radial turbine with blade ring and power unit

Abstract

This invention relates to the field of engine technology, specifically to a miniature radial turbine with an impeller ring and its power unit. The miniature radial turbine includes: a casing with a receiving cavity; an impeller disposed within the receiving cavity; blades disposed on the impeller, with a gap between the blades and the inner wall of the casing; a leakage fluid working medium flowing from the pressure surface of the blades through the gap to the suction surface of the blades, forming a leakage area; and an impeller ring fitted over all the blades, surrounding the impeller circumferentially; and the impeller ring at least partially covering the leakage area. This solution utilizes the impeller ring to partially block the gap, directly preventing the leakage path of airflow flowing from the pressure surface of the blades through the gap to the suction surface. This avoids energy waste caused by the leakage working medium's inability to perform work on the blades, and reduces mixing losses caused by the mixing of the leakage airflow with the mainstream, effectively improving the problems of high leakage losses and low aerodynamic efficiency caused by large gaps in miniature radial turbines.

Description

Technical Field

[0001] This invention relates to the field of engine technology, and specifically to a miniature radial turbine with blade rings and its power unit. Background Technology

[0002] The radial turbine is a core working component of a power plant, such as an aero-engine or gas turbine. Due to its compact structure, large single-stage expansion ratio, and fewer components, the radial turbine is widely used in micro gas turbines and supercritical closed-cycle CO2 power plants. However, due to assembly requirements to prevent abrasion, a certain assembly clearance must be maintained between the impeller tip and the casing. A fluid pressure difference exists between the pressure and suction surfaces of the blades; however, the working fluid can leak from the pressure surface to the suction surface through the blade tip gap, creating leakage.

[0003] Since leaking fluid cannot drive the blades to do work and will mix with the mainstream flow in the blade cascade, resulting in mixing losses, tip leakage loss is a key factor limiting turbine efficiency improvements. Furthermore, there is currently a lack of tip leakage technology suitable for miniature radial turbines. Summary of the Invention

[0004] In view of this, the present invention provides a miniature radial turbine with an impeller and a power unit to solve the problem of low turbine efficiency caused by fluid leakage in radial turbines.

[0005] In a first aspect, the present invention provides a miniature centripetal turbine with an impeller ring, the miniature centripetal turbine comprising: The casing is provided with a receiving cavity, which has an air inlet side and an air outlet side; An impeller is installed in a receiving cavity; blades are installed on the impeller, and a gap is provided between the blades and the inner wall of the casing; the leaking fluid working medium flows from the pressure surface of the blade through the gap to the suction surface of the blade to form a leakage area; The blade ring is fitted onto all the blades and connected to all the blades, so that the blade ring surrounds the circumference of the impeller; The blade ring has a first end and a second end, with the first end located near the air inlet side and the second end located near the air outlet side, and the blade ring at least covers part of the leakage area.

[0006] Beneficial effects: This design employs a circumferentially circumferential blade ring fitted around the tips of all blades. This ring partially blocks the gaps, directly preventing leakage channels where airflow travels from the pressure side of the blade through the gaps to the suction side. This avoids energy waste caused by the leaking working fluid failing to perform work on the blades, and reduces mixing losses caused by the leakage airflow mixing with the mainstream. It effectively improves the problems of high leakage losses and low aerodynamic efficiency in micro-sized centripetal turbines due to relatively large tip clearances.

[0007] Meanwhile, in this design, the impeller ring can cover part of the leakage area, completely cover the leakage area, or cover beyond the leakage area. This can improve aerodynamic efficiency while controlling the overall weight of the impeller according to actual conditions, avoiding excessive weight of the impeller and affecting aerodynamic efficiency.

[0008] In one alternative implementation, the direction of the working fluid flow is set: the point where the leakage flow passes through the tip of the blade is the leakage start point, the point where the leakage flow gradually decreases is the leakage weakening point, and the point where the leakage flow no longer crosses the tip of the blade is the leakage termination point. The first end extends out into the leakage area, such that the first end is located between the leakage initiation point and the end of the blade near the air inlet side.

[0009] Beneficial effects: In this embodiment, the first end of the blade ring is arranged between the leading edge of the blade and the leakage initiation point, that is, along the direction of the working fluid, the first end of the blade ring is located upstream of the leakage initiation point. This allows the gap to be sealed in advance before the leakage flow crosses the blade tip and forms a cross-tip flow. This forces the starting point of the leakage flow at the blade tip to shift to the middle and rear section of the blade, thereby significantly reducing the flow loss caused by the leakage flow and optimizing the uniformity of the flow field at the leading edge of the blade.

[0010] In one alternative embodiment, the blade is at a height of H mm on the air inlet side, and the distance between the first end and the leakage initiation point is L mm, where L is between 0.2H and 0.5H.

[0011] Beneficial effects: In this embodiment, the distance from the first end to the leakage initiation point is limited to 20% to 50% of the inlet blade height. This parameter range has been optimized through multiple rounds of simulation. If the distance is too small, the blade ring will have difficulty sealing the leakage flow in its initial stage, resulting in insufficient leakage control benefits. If the distance is too large, the ineffective section of the blade ring will be too long, which will excessively increase the impeller weight and affect the rotor dynamic balance performance.

[0012] Therefore, this embodiment can maximize the leakage suppression effect within this size range, while also accurately controlling the blade ring volume and balancing aerodynamic benefits with lightweight design requirements.

[0013] In one alternative embodiment, a blade cascade channel is formed between two adjacent blades, and the blade ring has a protrusion on the side facing the blade cascade channel. The protrusion extends into the interior of the blade cascade channel, and the thickness of the protrusion along the spanwise direction of the blade is t mm, where t is between 0.5%H and 10%H.

[0014] Beneficial effects: In this embodiment, the thickness of the protrusion is limited to 0.5% to 10% of the inlet blade height. The lower limit of the thickness can ensure the structural rigidity of the blade ring under miniature size and resist the risk of deformation and fracture under normal operating conditions. The upper limit of the thickness can prevent the blade ring from bulging excessively into the blade channel and disturbing the mainstream streamline, avoiding additional flow resistance and eddy current loss, and achieving the optimal match between structural reliability and aerodynamic smoothness.

[0015] In one alternative implementation, the second end is located between the leak initiation point and the leak attenuation point.

[0016] Beneficial effects: In this embodiment, the blade ring only covers the core leakage area at the front end where leakage loss is most concentrated, so that the blade ring uses the least amount of material, the impeller weight increase is minimal, and the overall size of the ring is short. It can accurately seal high-loss leakage channels, effectively reduce leakage loss at a very low weight cost, and has outstanding cost-effectiveness advantages. It is extremely suitable for micro power equipment with extremely strict weight control.

[0017] In one alternative implementation, the second end is located between the leakage reduction point and the leakage termination point.

[0018] Beneficial effects: This embodiment completely covers the entire range of leakage flow from generation to gradual decay with the blade ring, blocking most of the leakage channels across the blade tip. The leakage suppression effect is significantly improved compared to the short ring structure, and the turbine aerodynamic efficiency is improved even more. Compared to a full-size blade ring extending to the blade trailing edge, the redundant ring structure from the leakage termination point to the trailing edge is eliminated, avoiding impeller overweight and overcoming the defects of excessive weight compensation and deteriorated rotor dynamics in traditional fully enclosed impellers.

[0019] In one alternative implementation, the second end extends out of the leakage area such that the second end is located between the leakage termination point and the end of the blade near the air outlet side.

[0020] Beneficial effects: This embodiment completely covers the entire leakage generation area with the blade ring, sealing off all gaps prone to tip crossflow, further improving leakage control and significantly increasing turbine efficiency. Simultaneously, the blade ring does not extend to the blade trailing edge, reducing the ring volume compared to a full-length blade ring, effectively lowering impeller weight and rotor moment of inertia, and optimizing rotor stability at high speeds.

[0021] In one alternative implementation, the second end extends out of the leakage area and extends to the end of the blade near the air outlet side.

[0022] Beneficial effects: In this embodiment, the blade ring extends from the leading edge to the trailing edge of the blade, sealing the blade tip gap throughout its entire stroke. This maximizes the prevention of tip leakage flow across the entire blade section, resulting in the best leakage loss suppression effect and the greatest improvement in turbine efficiency. It is suitable for power units with high aerodynamic performance requirements. However, the impeller is relatively heavy, making it more suitable for power units with less stringent weight constraints.

[0023] In one alternative implementation, the impeller and the blade ring are integrally formed.

[0024] Beneficial effects: This embodiment adopts a one-piece molding structure for the impeller and blade ring, resulting in excellent overall integrity of the parts and eliminating assembly gaps caused by separate assembly, thus completely eliminating hidden energy loss caused by air leakage from gaps. Furthermore, one-piece machining eliminates the need for separate assembly processes, is suitable for the precision machining of micro-sized and ultra-thin blades, and avoids the drawbacks of traditional perforated and slotted leak control structures being difficult to machine on small blades and having a low molding yield. At the same time, one-piece machining also enhances the overall structural strength and vibration resistance of the impeller, extending its service life under high-temperature and high-speed operating conditions.

[0025] In a second aspect, the present invention also provides a power device comprising a centripetal turbine as described in any of the above embodiments.

[0026] Beneficial effects: In this embodiment, the power unit can be an aircraft engine with a micro-sized radial turbine, a micro gas turbine, or other power units. The leakage loss at the turbine tip is significantly reduced, the isentropic efficiency of the turbine is improved, and the overall thermodynamic cycle efficiency is simultaneously improved. This can effectively reduce the consumption of working fluid and fuel, increase the overall output power, and improve the operating economy and operating condition adaptability of the power unit. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of the present invention, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram illustrating the percentage of various losses in a centrifugal turbine. Figure 2 This is a schematic diagram of the leakage flow between blades in a radial turbine. Figure 3 This is a schematic diagram of the design process of the centripetal turbine in an embodiment of the present invention; Figure 4 This is a schematic diagram of a conventional radial turbine. Figure 5A schematic diagram showing the distribution of the initial, weakening, and termination points of the leakage flow; Figure 6 This is a cross-sectional view of the centripetal turbine in an embodiment of the present invention; Figure 7 This is a top view of the centripetal turbine in an embodiment of the present invention; Figure 8 This is a schematic diagram showing the starting and ending positions of the blade ring on the blade in an embodiment of the present invention; Figure 9 This is a schematic diagram comparing the structure of a conventional turbine and the turbine in this design; Figure 10 This is a performance comparison diagram between a conventional turbine and the turbine in this design; Figure 11 This is a schematic diagram comparing the leakage flow of a conventional turbine and the turbine in this design.

[0029] Explanation of reference numerals in the attached figures: 1. Casing; 2. Impeller; 3. Blades; 4. Blade ring; 5. Protrusion; A. Leakage initiation point; B. Leakage reduction point; C. Leakage termination point. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used for the convenience of describing the invention and for simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes and should not be construed as indicating or implying relative importance.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] The turbine is one of the three major components in gas turbines and aero engines, and its efficiency level directly affects key indicators such as the overall thermodynamic cycle efficiency and fuel consumption rate of the engine. Centripetal turbines are widely used in gas turbines and aero engines due to their simple structure, fewer parts, and large single-stage expansion ratio.

[0035] However, due to the relatively small blade height, the efficiency level of the radial turbine is greatly affected by the relative height of the blade tip clearance. Figure 1 The percentage of various losses for a micro centripetal turbine is given. It can be seen that, among the six losses, tip leakage accounts for 30.05%, making it one of the important factors affecting the efficiency of the centripetal turbine.

[0036] This is mainly because the impeller 2 of the radial turbine is relatively small. To prevent impeller 2 from rubbing against the casing 1, a clearance height of 0.15~0.5mm, approximately 1%~10% of the relative blade height, is generally required. Due to the pressure difference between the pressure and suction surfaces of impeller 2 and the relative movement between casing 1 and impeller 2, the fluid working medium flows from the pressure surface to the suction surface through the blade tip gap, such as... Figure 2 As shown, on the one hand, this part of the fluid flows through the gap and cannot perform work on the blade 3; on the other hand, this part of the fluid mixes with the mainstream, causing a large mixing loss, which limits the improvement of the aerodynamic efficiency of the centripetal turbine.

[0037] Furthermore, in power generation systems such as micro gas turbines and supercritical carbon dioxide closed-cycle systems, the low flow rate and high density of the working fluid result in extremely compact impeller 2 dimensions for centripetal turbines. The inlet blade height is typically in the millimeter range, only 1~5mm. In this case, the relatively large impeller 2 relative to the blade tip clearance may exceed 10%, causing complex blade tip leakage flow and significant leakage losses, which severely restricts the aerodynamic efficiency of the turbine.

[0038] Existing tip leakage flow control methods used in large-size radial turbines, such as tip slots, tip grooves, and tip injection holes, can reduce tip leakage flow to some extent. However, when applied to micro-sized radial turbines, they suffer from difficulties in processing, insignificant effects, and excessive weight compensation, making them unsuitable for micro-sized radial turbines.

[0039] In medium and large-sized radial turbines, tip slots and tip injection holes are typical methods for controlling tip leakage flow, which can reduce leakage flow losses to a certain extent. These methods rely on processes such as slotting, perforating, and machining on the impeller blades. For large-sized turbines, there is ample space to ensure the machining and forming of structures such as slots, holes, and grooves. However, for compact micro-radial turbines, the extremely limited machining space makes it difficult to machine structures such as slots and holes, making the above methods difficult to apply in engineering.

[0040] The closed impeller 2 structure is also a way to improve the aerodynamic efficiency of large-size centripetal turbines, but this method is difficult to apply to small-size impeller 2. One reason is the difficulty in manufacturing, which leads to serious deviations in the dimensions of the blade passage, making it difficult to meet the design requirements of high-performance turbines. Another reason is that the "full enclosure" of the blade tip of the closed impeller 2 increases the overall weight of the impeller 2. For small-size centripetal turbines that generally have strict weight limits, this leads to problems such as excessive weight compensation and insufficient rotor dynamics and blade strength.

[0041] Therefore, there is currently no effective control method for leakage flow at the tip of such tiny centripetal turbine blades.

[0042] In view of this, the present invention provides a miniature radial turbine with an impeller and a power unit to solve the problem of low turbine efficiency caused by fluid leakage in radial turbines.

[0043] The following is combined with Figures 1 to 11 The following describes embodiments of the present invention.

[0044] According to an embodiment of the present invention, in one aspect, a miniature centripetal turbine with an impeller ring is provided, the miniature centripetal turbine comprising: a casing 1, an impeller 2, and an impeller ring 4.

[0045] Specifically, in this embodiment, the casing 1 is provided with a receiving cavity, which is divided into an air inlet side and an air outlet side along the flow direction of the working fluid. The air inlet side corresponds to the inlet of the working fluid, and the air outlet side corresponds to the air outlet of the impeller 2. The inner wall of the receiving cavity forms a sealing and limiting surface on the periphery of the impeller 2 and is used to limit the assembly size of the blade tip clearance.

[0046] Furthermore, in this embodiment, the impeller 2 is disposed in the receiving cavity, and multiple blades 3 are evenly distributed around the circumference of the impeller 2. A gap is provided between the tip of the blade 3 and the inner wall of the casing 1. During actual operation, driven by the pressure difference between the pressure surface and the suction surface of the blade 3, the working fluid flows from the pressure surface of the blade 3 through the gap at the blade tip to the suction surface. This flow area is the leakage area.

[0047] Furthermore, in this embodiment, the blade ring 4 is integrally fitted around the tips of all blades 3 and connected to all blades 3, such that the blade ring 4 surrounds the impeller 2 circumferentially. Moreover, along the flow direction of the working fluid, the blade ring 4 has a first end and a second end, as shown... Figure 8 As shown, the first end is the starting position SS, and the second end is the ending position SE. The first end is set near the air inlet side, and the second end is set near the air outlet side. The blade ring 4 covers at least part of the leakage area.

[0048] This design employs a circumferentially circumferential blade ring 4 fitted at the tips of all blades 3. This blade ring 4 partially blocks the gaps, directly preventing the leakage path of airflow from the pressure side of the blade 3 through the gaps to the suction side. This avoids energy waste caused by the leaking working fluid failing to perform work on the blades 3, and reduces mixing losses caused by the mixing of the leaking airflow with the mainstream. It effectively improves the problems of high leakage losses and low aerodynamic efficiency in micro-sized radial turbines caused by relatively large blade tip clearances.

[0049] Meanwhile, in this design, the blade ring 4 can cover part of the leakage area, completely cover the leakage area, or extend beyond the leakage area. Technicians can flexibly adjust the length of the blade ring 4 according to the actual weight and performance specifications of the turbine. This allows for improved aerodynamic efficiency while controlling the overall weight of the impeller 2 to prevent it from becoming too heavy and affecting aerodynamic efficiency.

[0050] Furthermore, in an optional embodiment, the direction of the fluid working medium is used as the setting: the point where the leakage flow passes through the tip of blade 3 is the leakage start point A, the point where the leakage flow gradually decreases is the leakage weakening point B, and the point where the leakage flow no longer crosses the tip of blade 3 is the leakage termination point C. For example... Figure 5 As shown, the leakage initiation point A is A, the leakage reduction point B is B, and the leakage termination point C is C.

[0051] In this embodiment, the first end of the blade ring 4 extends into a leakage area, such that the first end is located between the leakage initiation point A and the end of the blade 3 near the air inlet side.

[0052] In this embodiment, the first end of the blade ring 4 is arranged between the leading edge of the blade 3 and the leakage initiation point A. That is, along the direction of the working fluid, the first end of the blade ring 4 is located upstream of the leakage initiation point A. This allows the gap to be sealed in advance before the leakage flow crosses the blade tip and forms a cross-tip flow. This forces the starting point of the blade tip leakage flow to shift to the middle and rear section of the blade 3, thereby significantly reducing the flow loss caused by the leakage flow and optimizing the uniformity of the flow field at the leading edge of the blade 3.

[0053] Furthermore, in an optional embodiment, the height of the blade 3 on the air inlet side is H mm, and the distance between the first end and the leakage initiation point A is L mm, that is, the distance between the starting position SS and the leakage initiation point A is L mm, and L is between 0.2H and 0.5H.

[0054] In this embodiment, the distance of the first end beyond the leakage initiation point A is limited to 20% to 50% of the inlet blade height. This parameter range has been optimized through multiple rounds of simulation. If the distance is too small, the blade ring 4 will have difficulty completing the sealing in the initial stage of the leakage flow, resulting in insufficient leakage control benefits. If the distance is too large, the ineffective section of the blade ring 4 will be too long, which will excessively increase the weight of the impeller 2 and affect the rotor dynamic balance performance.

[0055] Therefore, this embodiment can maximize the leakage suppression effect within this size range, while also precisely controlling the volume of the blade ring 4, balancing aerodynamic benefits and lightweight design requirements.

[0056] Furthermore, in an optional embodiment, a blade cascade channel is formed between two adjacent blades 3, and the blade ring 4 is provided with a protrusion 5 on the side facing the blade cascade channel. The protrusion 5 extends into the interior of the blade cascade channel, and the thickness of the protrusion 5 along the spanwise direction of the blade 3 is t mm, and t is between 0.5%H and 10%H.

[0057] In this embodiment, the thickness of the blade ring 4 is limited to 0.5% to 10% of the inlet blade height. The lower limit of the thickness can ensure the structural rigidity of the blade ring 4 under miniature size and resist the risk of deformation and fracture under normal operating conditions. The upper limit of the thickness can prevent the blade ring 4 from bulging excessively into the blade channel and disturbing the mainstream streamline, avoiding additional flow resistance and eddy current loss, and achieving the optimal match between structural reliability and aerodynamic smoothness.

[0058] There are four possible extension lengths for the second end of the blade ring 4, and the following embodiments will describe them respectively.

[0059] The first extension method involves extending the second end so that it is located between the leakage initiation point A and the leakage reduction point B.

[0060] In this embodiment, the blade ring 4 only covers the core leakage area at the front end where leakage loss is most concentrated, so that the blade ring 4 uses the least amount of material, the impeller 2 has the smallest increase in weight, and the overall size of the ring is short. It can accurately seal the high-loss leakage channel, and achieve an effective reduction in leakage loss at a very low weight cost. It has outstanding cost-effectiveness advantages and is extremely suitable for micro power equipment with extremely strict weight control.

[0061] The second extension method involves extending the second end so that it is located between the leakage reduction point B and the leakage termination point C.

[0062] In this embodiment, the blade ring 4 completely covers the entire range of leakage flow from generation to gradual decay, blocking most of the leakage channels across the blade tip. The leakage suppression effect is significantly improved compared to the short ring structure, and the turbine aerodynamic efficiency is improved even more. Compared to the full-size blade ring 4 extending to the trailing edge of blade 3, the redundant ring structure from the leakage termination point C to the trailing edge is eliminated, avoiding excessive weight of impeller 2 and overcoming the defects of excessive weight compensation and deteriorated rotor dynamics in traditional fully enclosed impeller 2.

[0063] The third extension method involves extending the second end out of the leakage area, so that the second end is located between the leakage termination point C and the end of the blade 3 near the air outlet side.

[0064] In this embodiment, the blade ring 4 completely covers the entire leakage generation area, sealing off all gaps prone to tip crossflow, further improving leakage control and significantly increasing turbine efficiency. Simultaneously, the blade ring 4 does not extend to the trailing edge of the blade 3, reducing the ring volume compared to a full-length blade ring 4, effectively lowering the impeller 2's weight and rotor inertia, and optimizing rotor stability at high speeds.

[0065] The fourth extension method involves extending the second end out of the leakage area and extending it to the end of blade 3 near the air outlet side.

[0066] In this embodiment, the blade ring 4 extends from the leading edge to the trailing edge of the blade 3, sealing the tip gap of the blade 3 throughout its entire stroke. This maximizes the prevention of tip leakage flow across the entire blade section, resulting in the best leakage loss suppression effect and the greatest improvement in turbine efficiency. This design is suitable for power units with high aerodynamic performance requirements. However, the impeller 2 is relatively heavy, making it more suitable for power units with less stringent weight constraints.

[0067] Furthermore, in one alternative embodiment, the impeller 2 and the blade ring 4 are integrally formed.

[0068] In this embodiment, the impeller 2 and the blade ring 4 are integrally molded, resulting in excellent overall integrity of the parts and eliminating assembly gaps caused by separate assembly, thus completely eliminating hidden energy loss caused by air leakage from gaps. Furthermore, integral machining eliminates the need for separate assembly processes, making it suitable for the precision machining of micro-sized ultra-thin blades 3, and avoiding the drawbacks of traditional perforated and slotted leak control structures on small blades 3, which are difficult to machine and have low forming yield. Simultaneously, integral machining also enhances the overall structural strength and vibration resistance of the impeller 2, extending its service life under high-temperature and high-speed operating conditions.

[0069] The R&D team went through five design steps when designing the miniature centripetal turbine in this solution, such as... Figure 3 As shown, it specifically includes: S1, the impeller of the radial turbine has an aerodynamic design; Similar to the aerodynamic design method for impeller 2 in conventional radial turbines, based on the overall circulation parameter requirements, one-dimensional design, radial distribution design, and three-dimensional modeling of blade 3 are performed to finally complete the aerodynamic design of impeller 2, resulting in a three-dimensional drawing of impeller 2, as shown below. Figure 4 As shown.

[0070] Analysis of the development of leakage flow in the gap between S2 and impeller 2; The centripetal turbine to which the method of this invention is to be applied is initially verified using CFt to obtain initial turbine efficiency and power performance parameters. The focus is on tip leakage flow analysis and full three-dimensional flow field analysis of impeller 2. Through analysis, such as... Figure 5 As shown, the leakage starting point A, where the gap leakage flow crosses the blade tip and enters the mainstream, the leakage weakening point B, where the influence of the leakage flow on the mainstream begins to decrease, and the leakage termination point C, where the leakage flow no longer crosses the blade tip, are determined. Among them, the AB segment is the area where the gap leakage flow has the greatest influence on the mainstream and causes the most mixing loss.

[0071] S3, Design of a finite crown ring structure; Based on the gap leakage flow analysis in step S2, considering processing factors and according to performance improvement requirements, the first end of the blade ring 4, namely SS, is selected at the position of 20% to 50% of the inlet blade height before point A. The blade ring 4 is arranged between SS and B, or between SS and C.

[0072] like Figure 6 and Figure 7 The diagram shows a radial turbine impeller 2 with a circumferential blade ring 4 arranged in a finite envelope range along the flow direction.

[0073] In practical applications, the blade ring 4 can also be positioned at the top of the impeller blade 3, for example, at 90% to 100% of the blade height. In the flow direction, such as... Figure 8As shown, let the flow direction position of the leading edge of impeller 2 be 0% and the position of the trailing edge be 100%, and let the blade ring 4 start at the SS flow direction position and end at the SE flow direction position, where 0%≤SS≤SE≤100%.

[0074] Furthermore, in the spanwise direction, the blade ring 4 extends into the blade passage with a thickness t, which is approximately 0.5% to 10% of the height of the inlet-side blade 3, and the specific thickness can be selected based on the strength verification results. In the circumferential direction, the blade ring 4 occupies the entire 360° circumferential space within its enclosed flow direction.

[0075] S4. Numerical verification of performance improvement effect: The performance of the centripetal turbine with the applied blade ring 4 is verified using the same CFt calculation method as in step S2.

[0076] S5. Determine if the requirements are met. If the turbine performance does not meet the requirements, repeat steps S3 and S4 until the requirements are met. If the turbine performance meets the performance improvement requirements, stop.

[0077] The specific testing process for this solution is as follows: Taking a small-sized supercritical carbon dioxide back-to-back centripetal turbine as an example, with the following specifications: the inlet blade height of impeller 2 is only 3.3 mm and the blade tip clearance is 0.3 mm, the control effect of applying the blade ring 4 in this scheme on the leakage flow loss at the blade tip of impeller 2 was compared and studied using a full three-dimensional numerical simulation method.

[0078] like Figure 9 The diagram shows the three-dimensional geometry of a conventional impeller 2 (without the blade ring 4) and the impeller 2 after applying the blade ring 4 in this design. During testing, the initial flow direction position of the blade ring 4 was set to 0%, with a thickness of 0.5 mm. The final flow direction positions of the blade ring 4 were set to 10%, 20%, 30%, and 40%, respectively, meaning the coverage range of the blade ring 4 was 0% to 40%. Figure 8 As shown.

[0079] Then, the three-dimensional flow field inside the conventional impeller 2 and the impeller 2 of this scheme was numerically simulated using ANSYS CFX software, and the turbine aerodynamic performance of the conventional impeller 2 and the four impeller 2 of this scheme was obtained.

[0080] Figure 10 The diagram shows a comparison of turbine efficiencies for five different impeller types 2. A flow envelope range of 0.0 represents a conventional impeller 2 without a crown ring. A flow envelope range of 0.1 indicates a 10% coverage area of ​​the blade ring 4; a flow envelope range of 0.2 indicates a 20% coverage area; a flow envelope range of 0.3 indicates a 30% coverage area; and a flow envelope range of 0.4 indicates a 40% coverage area.

[0081] As can be seen, the limited flow direction of the blade ring 4 has a significant impact on the aerodynamic performance of the micro-sized centripetal turbine. With the use of blade ring 4, the turbine efficiency increases with the increase of the flow direction envelope range of the crown ring. When the flow direction envelope range of the crown ring reaches 0%~40%, the aerodynamic efficiency of the turbine is nearly 0.45% higher than that of the conventional crownless impeller 2.

[0082] This solution further analyzes the leakage flow in the impeller 2 clearance.

[0083] like Figure 11 As shown, the limiting streamlines on the blade surface 3 of a conventional impeller 2 without a crown ring and an impeller 2 with a flow envelope range of 0%~40% are compared. It can be seen that for the conventional impeller 2, there is a very obvious secondary flow on the suction side of the leading edge of its blade 3. The suction surface separation flow caused by the positive angle of attack at the leading edge interacts with the tip leakage flow generated from the pressure surface to the suction surface from the leading edge, resulting in turbulent limiting streamlines in the leading edge region of the suction surface and strong secondary flow losses.

[0084] When the blade ring 4 is used, the blade ring 4 physically hinders the tip leakage flow near the leading edge. There is no tip gap between the blade 3 and the casing 1 within the flow envelope covered by the blade ring 4 in the leading edge region. The fluid cannot flow from the pressure surface of the blade 3 through the gap to the suction surface, which improves the secondary flow mixing in the leading edge region of the suction surface of the blade 3 and reduces the secondary flow loss in the leading edge region.

[0085] Downstream of the blade ring 4, the blade tip clearance between the blade 3 and the casing 1 is restored. At this time, the blade tip leakage flow begins to form and rapidly develops towards the pressure surface of the adjacent blade 3 under the action of the pressure difference driving force at the higher position in the middle of the blade 3. It basically does not affect the limiting streamline on the suction surface side of the blade 3. Therefore, the limiting streamlines of the conventional impeller 2 and the impeller 2 of this scheme are basically the same downstream of the suction surface side.

[0086] The above results indicate that the control of the tip leakage flow of impeller 2 by the blade ring 4 is mainly manifested in delaying the generation of the tip leakage flow, postponing the location of the leakage flow generation from near the leading edge to the midstream flow direction of blade 3 where the leakage flow pressure differential driving force is higher. This weakens the interaction between the separated flow induced by the angle of attack near the leading edge of the suction surface and the leakage flow, and allows the leakage flow generated in the midstream flow direction to rapidly develop into the blade passage under a higher pressure differential driving force, thus reducing its impact on the flow on the suction surface of blade 3. The combined effect of these two factors effectively reduces the tip leakage flow loss of impeller 2, thereby improving the aerodynamic performance of the small-sized centripetal turbine.

[0087] In a second aspect, the present invention also provides a power device comprising a centripetal turbine as described in any of the above embodiments.

[0088] In this embodiment, the power unit can be an aero-engine with a micro-sized radial turbine, a micro gas turbine, or other power units. The leakage loss at the turbine tip is significantly reduced, the isentropic efficiency of the turbine is improved, and the overall thermodynamic cycle efficiency is simultaneously improved. This can effectively reduce the consumption of working fluid and fuel, increase the overall output power, and improve the operating economy and operating condition adaptability of the power unit.

[0089] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A miniature centripetal turbine with an impeller ring, characterized in that, include: The casing (1) is provided with a receiving cavity, which is provided with an air inlet side and an air outlet side; An impeller (2) is disposed in the cavity; blades (3) are disposed on the impeller (2), and a gap is provided between the blades (3) and the inner wall of the casing (1); the fluid working medium flows from the pressure surface of the blades (3) through the gap to the suction surface of the blades (3) to form a leakage area; A blade ring (4) is fitted onto all the blades (3) and connected to all the blades (3) such that the blade ring (4) surrounds the circumference of the impeller (2); The blade ring (4) has a first end and a second end, the first end being disposed near the air inlet side and the second end being disposed near the air outlet side, and the blade ring (4) at least covers part of the leakage area.

2. The miniature centripetal turbine according to claim 1, characterized in that, The leakage is set according to the direction of fluid flow: the point where the leakage flow passes through the top of the blade (3) is the leakage start point (A), the point where the leakage flow gradually decreases is the leakage weakening point (B), and the point where the leakage flow no longer crosses the top of the blade (3) is the leakage termination point (C). The first end extends out of the leakage area, such that the first end is located between the leakage initiation point (A) and the end of the blade (3) near the air inlet side.

3. The miniature centripetal turbine according to claim 2, characterized in that, The blade (3) is at a height of H mm on the air inlet side, and the distance between the first end and the leakage initiation point (A) is L mm, with L being between 0.2H and 0.5H.

4. The miniature centripetal turbine according to any one of claims 1 to 3, characterized in that, A blade cascade channel is formed between two adjacent blades (3). The blade ring (4) has a protrusion (5) facing the blade cascade channel. The protrusion (5) extends into the interior of the blade cascade channel, and the thickness of the protrusion (5) along the span of the blade (3) is t mm, and t is between 0.5%H and 10%H.

5. The miniature centripetal turbine according to claim 2 or 3, characterized in that, The second end is located between the leakage initiation point (A) and the leakage reduction point (B).

6. The miniature centripetal turbine according to claim 2 or 3, characterized in that, The second end is located between the leakage reduction point (B) and the leakage termination point (C).

7. The miniature centripetal turbine according to claim 2 or 3, characterized in that, The second end extends out of the leakage area, such that the second end is located between the leakage termination point (C) and the end of the blade (3) near the air outlet side.

8. The miniature centripetal turbine according to any one of claims 1 to 3, characterized in that, The second end extends out of the leakage area and extends to the end of the blade (3) near the air outlet side.

9. The miniature radial turbine according to any one of claims 1 to 3, characterized in that, The impeller (2) and the blade ring (4) are integrally formed.

10. A power unit, characterized in that, include: The centripetal turbine as described in any one of claims 1 to 9.

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