A high-speed industrial steam turbine with large fan blade root and wheel groove

Abstract

The present invention discloses a large-angle blade root and wheel groove for a high-speed industrial steam turbine, belonging to the technical field of steam turbine devices; the structure includes a blade root body, the upper part of the blade root body is a blade root platform, and a plurality of pairs of teeth are arranged below the blade root platform, wherein the pairs of teeth are arranged in a longitudinal tree shape, namely, a first pair of teeth, a second pair of teeth, a third pair of teeth and a fourth pair of teeth, the first pair of teeth is connected to the lower edge of the blade root platform by a smooth curve, and the fourth pair of teeth is connected to the bottom of the blade root by a smooth curve; the relevant parameter design of the present invention can reduce the peak stress concentration on the blade root and the wheel groove by 27%-30%, so that the stress load is more inclined to equal strength distribution and the bearing capacity is greatly improved, which can meet the blade root and wheel groove strength requirements of the last-stage blade with a speed level of 12000rpm and a steam duct height of 9 inches.

Description

Technical Field

[0001] The invention relates to a large-degree blade root and a wheel groove of a high-speed industrial steam turbine, belonging to the technical field of steam turbine devices. Background Art

[0002] Industrial steam turbines are limited by the driven device, usually with high speed and small hub diameter, which brings great difficulties to the structural design of the low-pressure last-stage moving blades, especially the design of the blade root and wheel groove profile with high load-bearing capacity and low stress concentration.

[0003] Currently, the final-stage blades manufactured by various domestic and international industrial steam turbine manufacturers primarily utilize forked or fir-tree-shaped blade roots. Given comparable blade dimensions, the fir-tree blade root offers superior load-bearing capacity, but also presents the greatest design challenges. Publicly available literature indicates that very few final-stage blade series in the industry exceed the 10,000 rpm rating, and the blade duct height is typically 8 inches or less.

[0004] As market demands for higher energy efficiency increase, industrial steam turbines will develop towards higher speeds and greater single-unit power. This will increase the exhaust area required for the final-stage rotor blades, and the stress levels in the blade roots and wheel grooves will also increase. Therefore, from a reliability perspective, blade root and wheel groove profiles with greater load-bearing capacity, lower stress concentration, and the strength required for the final-stage rotor blades at speeds of 10,000 rpm and above are urgently needed. Summary of the Invention

[0005] The object of the present invention is to provide a large-degree blade root and wheel groove for a high-speed industrial steam turbine in response to the above-mentioned problems, which can reduce stress concentration in the blade root and wheel groove profile, improve its load-bearing capacity, and meet the strength requirements of the high-speed last-stage moving blades.

[0006] The technical solution adopted in the present invention is as follows:

[0007] A large-angle blade root for a high-speed industrial steam turbine includes a blade root body, the upper part of the blade root body is a blade root platform, and multiple pairs of teeth are arranged below the blade root platform. The pairs of teeth include four pairs of first pairs of teeth, second pairs of teeth, third pairs of teeth and fourth pairs of teeth distributed in a longitudinal tree shape. The first pair of teeth is connected to the lower edge of the blade root platform by a smooth curve, and the fourth pair of teeth is connected to the bottom of the blade root by a smooth curve. The pairs of teeth, the connection between the first pair of teeth and the lower edge of the blade root platform, and the connection between the fourth pair of teeth and the bottom of the blade root are all symmetrical along the center of the blade root.

[0008] Furthermore, the inclination angle of the load-bearing surface of the pair of teeth is 45°, and the angle between the load-bearing surface and the non-load-bearing surface is 85°.

[0009] Furthermore, the width of the pair of teeth gradually decreases from top to bottom, and the fan envelope angle thereof is 29.5°.

[0010] Furthermore, the pair of teeth have the same tooth height Da, tooth top transition arc radius Ra and tooth bottom transition arc radius Rb, the spacing between adjacent teeth is Db, and the proportional relationship satisfies Da:Db:Ra:Rb=0.415:1.0:0.186:0.202.

[0011] Furthermore, the first pair of teeth is connected to the lower edge of the blade root platform by a smooth curve, and the smooth curve includes three arc curves, namely arc A, arc B and arc C, and the corresponding arc curvature radius ratio relationship satisfies 0.5:1.0:0.42.

[0012] Furthermore, the fourth pair of teeth is connected to the bottom of the blade root by a smooth curve, and the smooth curve includes three arc curves, namely arc D, arc E and arc F, and the corresponding arc curvature radius ratio relationship satisfies 0.36:1.0:0.509.

[0013] Furthermore, the ratio of the width and effective height of the blade root body is 0.596:1.0.

[0014] Furthermore, the ratio of the distance from the center of the arc D to the bottom of the blade root to the distance from the working surface of the fourth pair of teeth is controlled to be less than 0.6.

[0015] Furthermore, the ratio between the pitch of the lower edge of the blade root platform and the blade root width satisfies 1.52-1.62.

[0016] A blade root wheel groove, matched with the above-mentioned high-speed industrial steam turbine large-sector blade root, includes a wheel groove body, which is assembled with the blade root body, and a gap is provided at the mating position between the blade root body and the wheel groove body after assembly;

[0017] The gap between the upper part of the wheel groove body and the lower edge of the blade root platform is 0.215-0.385mm, the gap between the wheel groove body and the load-bearing surface of each pair of teeth is 0-0.004mm, the gap between the wheel groove body and the non-load-bearing surface of the first pair of teeth, the second pair of teeth, the third pair of teeth and the fourth pair of teeth is 0.124-0.276mm, the gaps between the wheel groove body and the upper transition connection part and the lower transition connection part of the first pair of teeth, the second pair of teeth and the third pair of teeth are 0.05-0.156mm and 0.05-0.156mm respectively, the gap between the wheel groove body and the transition connection part of the fourth pair of teeth is 0.10-0.21mm, and the gap between the bottom of the wheel groove body and the bottom of the blade root is 0.265-0.435mm.

[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0019] The present invention discloses a high-speed industrial steam turbine with a large-angle blade root and groove. By improving the tooth profile arrangement of the blade root and groove, the connection curve between the first pair of teeth and the lower edge of the blade root platform, the connection curve between the fourth pair of teeth and the bottom of the blade root, and the aspect ratio of the blade root profile, the peak stress concentration on the blade root and groove is reduced by 27% to 30%, resulting in a more uniform stress load distribution and a significantly improved load-bearing capacity. The blade root and groove strength requirements of last-stage blades with a speed of 12,000 rpm and a steam duct height of 9 inches are met. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0021] Figure 1 It is a structural schematic diagram of the blade root of the present invention;

[0022] Figure 2 It is a schematic diagram of the assembly of the blade root and the wheel groove of the present invention. DETAILED DESCRIPTION

[0023] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0024] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0025] Example 1

[0026] A high speed industrial steam turbine with large fan blade root, such as Figure 1 and Figure 2 As shown, it includes a blade root body, the upper part of the blade root body is a blade root platform, and a plurality of pairs of teeth are arranged below the blade root platform. The pairs of teeth include 4 pairs of first pairs of teeth, second pairs of teeth, third pairs of teeth and fourth pairs of teeth distributed in a longitudinal tree shape. The first pair of teeth is connected to the lower edge of the blade root platform with a smooth curve, and the fourth pair of teeth is connected to the bottom of the blade root with a smooth curve. The pairs of teeth, the connection between the first pair of teeth and the lower edge of the blade root platform, and the connection between the fourth pair of teeth and the bottom of the blade root are all symmetrical along the center of the blade root.

[0027] Further optimization of the blade root structure was achieved, with the bearing surface inclination angle α of the teeth being 45°, and the angle β between the bearing and non-bearing surfaces being 85°. These structural parameters were designed to minimize the impact of the load borne by the blade root tooth profile on the root, and to rationally distribute the bending and shear stresses within the blade root profile.

[0028] Based on the above specific design, as a more specific design, the width of the teeth gradually decreases from top to bottom, and the fan envelope angle θ is 29.5°. This allows for a more rational arrangement of the blade roots and wheel grooves along the radial direction of the impeller, controlling the stress distribution along the radial direction to be uniform. Furthermore, the larger fan envelope angle also facilitates the fabrication of wheel grooves for rotors with small hub diameters.

[0029] The above data are taken as the design requirements of absolute values. After designing for the above specific parameters, the design of related height and bandwidth is further optimized. After determining the relative values ​​of certain parameters, the relative values ​​of related parameters can be obtained accordingly.

[0030] Based on the above specific design, as a more specific design, the pairs of teeth have the same tooth height Da, tooth top transition arc radius Ra, and tooth bottom transition arc radius Rb, the spacing between adjacent teeth is Db, and their proportional relationship satisfies Da:Db:Ra:Rb = 0.415:1.0:0.186:0.202. In the specific structural design, the relevant parameters of each tooth in the pair are designed to be identical to ensure the consistency of the overall structure. Through the design of the above proportional relationship, the peak stress concentration factor at the root of the tooth profile can be reduced by 30% while the extrusion stress of the bearing surface meets the allowable value.

[0031] As a further design optimization, the first pair of teeth connects to the lower edge of the blade root platform with a smooth curve. This curve consists of three segments: arc A, arc B, and arc C. The curvature radius of arc A is Rn1, the curvature radius of arc B is Rn2, and the curvature radius of arc C is Rn3. The corresponding arc curvature radii satisfy the ratio of Rn1:Rn2:Rn3 = 0.5:1.0:0.42. This design ratio reduces the peak stress concentration factor at this connection by 27%.

[0032] Building on the aforementioned design, a more specific design connects the fourth pair of teeth to the blade root using a smooth curve. This curve consists of three segments: arc D, arc E, and arc F. The curvature radius of arc D is Rd1, the curvature radius of arc E is Rd2, and the curvature radius of arc F is Rd3. The corresponding arc curvature radii satisfy the ratio of Rd1:Rd2:Rd3 = 0.36:1.0:0.509. This proportional design reduces the peak stress concentration factor at this connection by 29%.

[0033] As a more specific design, to control the wheel groove depth and reduce the centrifugal tensile stress at the wheel groove bottom, the ratio of the blade root width D0 and effective height H1 is D0:H1 = 0.596:1.0. Furthermore, based on this design, the ratio of the distance H3 from the center of arc D to the blade root bottom and the distance D4 from the working surface of the fourth pair of teeth is controlled to be less than 0.6, that is, H3 / D4 < 0.6. This minimizes the wheel groove bottom depth and further reduces the difficulty of wheel groove machining.

[0034] Furthermore, the ratio between the pitch T of the lower edge of the blade root platform and the blade root width D0 satisfies T / D0 = 1.52-1.62. This ensures a reasonable distribution of the blade roots and wheel grooves on the circumference of the disc, solving the problem of unilaterally high stress in the blade roots or wheel grooves at different blade root diameters.

[0035] In the above specific design, as a more specific description, when determining the design of relevant parameters such as D0 and H1, other relevant parameters can be directly obtained based on the design of relevant angles.

[0036] In combination with the design of the above-mentioned specific parameters, the relative values ​​of the blade root structural parameters and dimensions provided in this embodiment are as follows:

[0037]

[0038] Example 2

[0039] In combination with the above specific design, in a specific operation, in order to further optimize the design, a blade root wheel groove is provided as a match, which matches the large-sector blade root of a high-speed industrial steam turbine in Example 1. Specifically, 10, comprising a wheel groove body, which, after being assembled with the blade root body, has a gap provided at the mating portion between the blade root body and the wheel groove body after being assembled;

[0040] More specifically, with respect to the further design of relevant gaps, the gap G1 between the upper part of the wheel groove body and the lower edge of the blade root platform is 0.215-0.385mm, the gap G2 between the wheel groove body and the load-bearing surface of each pair of teeth is 0-0.004mm, the gap G4 between the wheel groove body and the non-load-bearing surface of the first pair of teeth, the second pair of teeth, the third pair of teeth and the fourth pair of teeth is 0.124-0.276mm, the gaps between the wheel groove body and the upper transition connection part and the lower transition connection part of the first pair of teeth, the second pair of teeth and the third pair of teeth are G3=0.05-0.156mm and G5=0.05-0.156mm respectively, the gap between the wheel groove body and the transition connection part of the fourth pair of teeth is G6=0.10-0.21mm, and the gap between the bottom of the wheel groove body and the bottom of the blade root is G7=0.265-0.435mm. In this specific design, gaps G3, G4, and G5 exist between the first, second, and third pairs of teeth and the profile of the wheel groove. This wheel groove profile is structurally aligned with the blade root's structural parameters, and reasonable clearances are provided at all mating locations between the blade root and the wheel groove. This effectively prevents stress concentration or poor contact between the load-bearing surfaces caused by localized jamming at the transition joint during assembly, ensuring uniform load-bearing on the blade root teeth.

[0041] In summary, the large-degree blade root and wheel groove of a high-speed industrial steam turbine of the present invention reduces the peak stress concentration on the blade root and wheel groove by 27% to 30% by improving the tooth profile arrangement of the blade root and wheel groove, the connection curve between the first pair of teeth and the lower edge of the blade root platform, the connection curve between the fourth pair of teeth and the bottom of the blade root, and the aspect ratio of the blade root profile. This makes the stress load more uniformly distributed and the load-bearing capacity greatly improved. It can meet the blade root and wheel groove strength requirements of the last-stage blade with a speed level of 12,000 rpm and a steam duct height of 9 inches.

[0042] The present invention is not limited to the aforementioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A large-degree blade root for a high-speed industrial steam turbine, characterized by: It includes a blade root body, the upper part of the blade root body is a blade root platform, and a plurality of pairs of teeth are arranged below the blade root platform, the plurality of pairs of teeth include four pairs of first pairs of teeth, second pairs of teeth, third pairs of teeth and fourth pairs of teeth distributed in a longitudinal tree shape, the first pair of teeth is connected to the lower edge of the blade root platform by a smooth curve, the fourth pair of teeth is connected to the bottom of the blade root by a smooth curve, and the connection between the first pair of teeth and the lower edge of the blade root platform, the connection between the first pair of teeth and the second pair of teeth, the connection between the second pair of teeth and the third pair of teeth, the connection between the third pair of teeth and the fourth pair of teeth, and the connection between the fourth pair of teeth and the bottom of the blade root are all symmetrical along the center of the blade root; The load-bearing surface inclination angle of multiple pairs of teeth is 45°, and the angle between the load-bearing surface and the non-load-bearing surface is 85°; The width of multiple pairs of teeth gradually decreases from top to bottom, and the fan envelope angle is 29.5°; The multiple pairs of teeth have the same tooth profile height Da, tooth profile top transition arc radius Ra and tooth profile bottom transition arc radius Rb, the spacing between adjacent teeth is Db, and the proportion relationship satisfies Da:Db:Ra:Rb=0.415:1.0:0.186:0.202; The first pair of teeth is connected to the lower edge of the blade root platform by a smooth curve. The smooth curve consists of three arc segments, namely arc A, arc B and arc C. The corresponding arc curvature radius ratio meets the relationship of 0.5:1.0:0.42; The fourth pair of teeth is connected to the bottom of the blade root by a smooth curve. The smooth curve includes three arc curves, namely arc D, arc E and arc F, and the corresponding arc curvature radius ratio meets the relationship of 0.36:1.0:0.509; The ratio between the width and effective height of the blade root body is 0.596:1.

0.

2. The large-angle blade root for a high-speed industrial steam turbine according to claim 1, characterized in that: The ratio of the distance from the center of the control arc D to the bottom of the blade root and the distance from the working surface of the fourth pair of teeth is less than 0.

6.

3. The large-angle blade root for a high-speed industrial steam turbine according to claim 1, characterized in that: The ratio between the pitch of the lower edge of the blade root platform and the blade root width satisfies 1.52-1.

62.

4. A blade root groove, adapted for use with a high-speed industrial steam turbine blade root having a large fan angle as claimed in any one of claims 1 to 3, characterized in that: It includes a wheel groove body, and after being assembled with a blade root body, a gap is provided at a fitting position between the blade root body and the wheel groove body; The gap between the upper part of the wheel groove body and the lower edge of the blade root platform is 0.215-0.385mm, the gap between the wheel groove body and the load-bearing surface of each pair of teeth is 0-0.004mm, the gap between the wheel groove body and the non-load-bearing surface of the first pair of teeth, the second pair of teeth, the third pair of teeth and the fourth pair of teeth is 0.124-0.276mm, the gaps between the wheel groove body and the upper transition connection part and the lower transition connection part of the first pair of teeth, the second pair of teeth and the third pair of teeth are 0.05-0.156mm and 0.05-0.156mm respectively, the gap between the wheel groove body and the transition connection part of the fourth pair of teeth is 0.10-0.21mm, and the gap between the bottom of the wheel groove body and the bottom of the blade root is 0.265-0.435mm.

Images