Low-damage noise reduction structure of low-pressure rotor of steam turbine and improvement method

Abstract

The invention discloses a turbine low-pressure rotor low-damage noise reduction structure and an improvement method.The turbine low-pressure rotor low-damage noise reduction structure comprises a turbine low-pressure rotor and an opposite wheel at the end of the turbine low-pressure rotor, a last-stage impeller and a plurality of preorder impellers are arranged on the circumference of the turbine low-pressure rotor, and the last-stage impeller and the preorder impellers are symmetrically arranged on the turbine low-pressure rotor; a step is arranged outside the last-stage impeller, a dovetail groove is formed in the side face of the step, the circumferences of the front-stage impellers are flat, and chamfers or fillets are arranged on the two sides of the front-stage impellers. According to the low-damage noise reduction structure for the low-pressure rotor of the steam turbine, air blowing and airflow friction noise generated by high-speed rotation of the impeller can be effectively restrained, and running noise of the steam turbine can be reduced to be within a qualified range; and meanwhile, the improvement method can reduce the machining amount of the impeller, ensures stable operation of the turbine low-pressure rotor, improves the overall operation efficiency of the turbine and is suitable for popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbines, and in particular to a low-damage noise reduction structure for a low-pressure rotor of a steam turbine and an improvement method thereof. Background Art

[0002] Steam turbines are core power equipment in thermal power generation, industrial drive and other fields. When the steam turbine is running, the original impeller balance hole and other structures produce a strong blowing effect and airflow friction under the high-speed rotating airflow, thereby generating huge noise; and this phenomenon will directly affect the performance and working environment of the steam turbine.

[0003] Common methods for addressing steam turbine noise include sound insulation and rotor reprocessing. Sound insulation typically involves installing a soundproofing enclosure around the turbine or treating the machine room with sound-insulating materials. Soundproofing enclosures are typically made of multi-layer composite materials and filled with sound-absorbing materials such as fiberglass and rock wool. These enclosures reduce the impact of noise by blocking sound transmission. In some small steam turbine applications, simple soundproofing enclosures can reduce noise by a certain decibel level, minimizing disturbance to the surrounding environment.

[0004] However, this approach has many limitations. For large steam turbines, installing a soundproof enclosure is difficult and costly due to its large size. The installation of a soundproof enclosure must take into account the equipment's maintenance and overhaul needs. An improper design can cause inconvenience during routine maintenance, increasing maintenance costs and time. Furthermore, a soundproof enclosure can only reduce the intensity of sound transmission and cannot fundamentally address the noise generated within the turbine. When the intensity of the noise source within the turbine is high, the soundproofing effect of the enclosure is limited, making it difficult to reduce the noise to the desired level.

[0005] However, reprocessing the rotor takes a long time and involves major changes, and the original turbine foundation, counter-wheels, turning system and other equipment need to be recalculated and redesigned, which adds a lot of uncertainty.

[0006] Therefore, there is an urgent need for a noise reduction structure and improvement method that can fundamentally reduce the impeller rotation noise, with small processing volume and low modification cost. Summary of the Invention

[0007] The purpose of the present invention is to solve the above problems and provide a low-damage noise reduction structure and improvement method for the low-pressure rotor of the steam turbine, which can effectively suppress the blast and airflow friction noise generated by the high-speed rotation of the impeller, and reduce the operating noise of the turbine to an acceptable range; at the same time, the improved method can reduce the processing amount of the impeller, ensure that the low-pressure rotor of the steam turbine maintains stable operation, and improve the overall operating efficiency of the turbine.

[0008] To achieve the above-mentioned purpose, the technical solution of the present invention is: a low-damage and noise reduction structure of a low-pressure rotor of a steam turbine, comprising a low-pressure rotor of a steam turbine and a pair of wheels at the end of the low-pressure rotor of the steam turbine, the circumference of the low-pressure rotor of the steam turbine being provided with a last-stage impeller and a plurality of preceding impellers, the last-stage impeller and the plurality of preceding impellers being symmetrically arranged on the low-pressure rotor of the steam turbine, the outside of the last-stage impeller being provided with a step, the side of the step being provided with a dovetail groove, the circumference of the plurality of preceding impellers being flat and chamfered or rounded on both sides.

[0009] In addition, the present invention also discloses a method for improving the low-damage noise reduction structure of the low-pressure rotor of a steam turbine, comprising the following steps: S1: modification of the last-stage impeller; S2: modification of the preceding impeller; S3: optimization of the low-pressure inner cylinder flow field; S4: overall processing of the rotor; and S5: reinstallation and testing.

[0010] Preferably, the step S1 also includes the following steps: S101: Identify the last-stage impeller on the low-pressure rotor of the steam turbine; S102: Turn the balancing hole and balancing plug on the outside of the original last-stage impeller to form a step; S103: Process at least one dovetail groove axially on the step side of the last-stage impeller; S104: Perform magnetic particle inspection on the blade root after processing to ensure that there are no crack defects; S105: According to the dynamic balancing requirements of the low-pressure rotor of the steam turbine, install an adjustable counterweight block in the dovetail groove, and the counterweight block is fixed by a locking bolt.

[0011] Preferably, step S2 also includes the following steps: S201: identifying multiple preceding impellers on the low-pressure rotor of the steam turbine, where the original preceding impellers are provided with outward-wrapped inverted T-shaped blade roots or outward-wrapped double inverted T-shaped blade roots; S202: turning the outward-wrapped inverted T-shaped blade roots and outward-wrapped double inverted T-shaped blade roots on the multiple preceding impellers until the chamfers or rounded corners of the blade roots are outwardly wrapped.

[0012] Preferably, the step S3 also includes the following steps: S301: Check the inner surface of the low-pressure inner cylinder corresponding to the impeller modification area; S302: Grind the sharp edges, protrusions, etc. in the inner cylinder to make them transition smoothly to form chamfers or rounded corners; S303: Seal the holes, guide holes, and pressure isolation plate grooves in the inner cylinder.

[0013] Preferably, the overall rotor treatment in step S4 is to perform a dynamic balancing test on the entire low-pressure rotor of the steam turbine to ensure that its balancing accuracy meets the requirements; in addition, the low-pressure rotor of the steam turbine needs to be cleaned.

[0014] Preferably, the step S5 further includes the following steps: S501: reinstalling the qualified low-pressure rotor of the steam turbine into the steam turbine; S502: performing a running test in the steam turbine to monitor and confirm that the noise value has been reduced to an acceptable range.

[0015] The present invention discloses a low-damage noise reduction structure and improvement method for a low-pressure rotor of a steam turbine, comprising a low-pressure rotor of a steam turbine and a pair of wheels at the ends of the low-pressure rotor of the steam turbine, wherein a final-stage impeller and a plurality of preceding impellers are provided on the circumference of the low-pressure rotor of the steam turbine, and the final-stage impeller and the plurality of preceding impellers are symmetrically arranged on the low-pressure rotor of the steam turbine, a step is provided on the outside of the final-stage impeller, a dovetail groove is provided on the side of the step, and the circumference of the plurality of preceding impellers is flat and chamfered or rounded on both sides; compared with the prior art, the low-damage noise reduction structure of the low-pressure rotor of the steam turbine has the function of effectively suppressing the blast and airflow friction noise generated by the high-speed rotation of the impeller, and can reduce the operating noise of the steam turbine to within an acceptable range; at the same time, the improvement method can reduce the processing amount on the impeller, ensure that the low-pressure rotor of the steam turbine maintains stable operation, and has the beneficial effect of improving the overall operating efficiency of the steam turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the structure before the last-stage impeller and the preceding impeller are modified Figure 1 .

[0017] Figure 2 Schematic diagram of the structure before the last-stage impeller and the preceding impeller are modified Figure 2 .

[0018] Figure 3 Schematic diagram of the low-damage noise reduction structure of the low-pressure rotor of the steam turbine in the present invention Figure 1 .

[0019] Figure 4 Schematic diagram of the low-damage noise reduction structure of the low-pressure rotor of the steam turbine in the present invention Figure 2 .

[0020] In the figure: 1. Steam turbine low-pressure rotor; 2. Pair of impellers; 3. Last-stage impeller; 31. Balancing hole; 32. Step; 33. Dovetail groove; 4. Precursor impeller; 41. Outer-wrapped double inverted T-shaped blade root; 42. Outer-wrapped inverted T-shaped blade root. DETAILED DESCRIPTION

[0021] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner, and thus only show components related to the present invention.

[0022] Please refer to Figure 1-4 The low-damage and noise reduction structure of the low-pressure rotor of the steam turbine comprises a low-pressure rotor 1 of the steam turbine and a pair of wheels 2 at the end of the low-pressure rotor 1. The circumference of the low-pressure rotor 1 of the steam turbine is provided with a final-stage impeller 3 and multiple preceding impellers 4. The final-stage impeller 3 and multiple preceding impellers 4 are symmetrically arranged on the low-pressure rotor 1 of the steam turbine. A step 32 is provided on the outside of the final-stage impeller 3, and a dovetail groove 33 is provided on the side of the step; the outer circumference of the multiple preceding impellers 4 is turned smooth and flat, and the edges are chamfered or rounded.

[0023] In this embodiment, the last-stage impellers 3 are the two outermost ones, and the preceding impeller 4 is arranged between the two last-stage impellers 3, among which there are five preceding impellers 4, and the total number of all the last-stage impellers 3 and preceding impellers 4 is 12; and the steps 32 and the dovetail grooves 33 are arranged on the outer side surfaces of the two outermost last-stage impellers 3; by changing the balancing method of the last-stage impeller 3 and the preceding impeller 4, the noise generated by the blast and airflow friction during the operation of the impeller can be effectively suppressed.

[0024] Please refer to the previous Figure 1-2 ,exist Figure 1-2 The outer array of the middle and last stage impeller 3 is provided with a plurality of balancing holes 31, and balancing plugs (not shown in the figure) can be set in the balancing holes 31, and the outer circumferences of the plurality of preceding impellers 4 are provided with external double inverted T-shaped blade roots or external inverted T-shaped blade roots; and when the low-pressure rotor 1 of the steam turbine drives the last stage impeller 3 and the preceding impeller 4 to rotate, the balancing holes 31, the balancing plugs, the external double inverted T-shaped blade roots or the external inverted T-shaped blade roots will produce a strong blast effect and airflow friction under the high-speed rotating airflow, thereby generating huge noise; and this huge noise affects the safe and stable operation of the unit and the on-site working environment.

[0025] Please refer to the modified Figure 3-4 ,exist Figure 3-4 In the embodiment, the balancing hole 31 and the internal balancing screw plug are removed on the outer side of the last-stage impeller 3 to form a step 32, and a dovetail groove 33 (dovetail groove type balancing groove) is provided on the vertical side wall of the step; in addition, multiple preceding impellers 4 are turned, specifically, the outer double inverted T-shaped blade root 41 or the outer inverted T-shaped blade root 42 is turned and removed, so that the outer circumference of multiple preceding impellers 4 is flat and smooth; such modification can effectively suppress the noise generated by the impeller during operation due to the friction between the blast and the airflow.

[0026] The method for improving the low-damage and noise reduction structure of the low-pressure rotor of the steam turbine includes the following steps: S1: modification of the last-stage impeller 3; S2: modification of the preceding impeller 4; S3: optimization of the low-pressure inner cylinder flow field; S4: overall processing of the rotor (steam turbine low-pressure rotor); S5: reinstallation and testing.

[0027] The step S1 further includes the following steps: S101: Identify the last-stage impeller 3 (the 1st and 12th-stage impellers) on the low-pressure rotor 1 of the steam turbine; S102: Turn the balancing hole 31 and the balancing screw plug on the outer side of the original last-stage impeller 3 to form a step 32; S103: Process at least one dovetail groove 33 axially on the side of the step 32 of the last-stage impeller 3; S104: Perform magnetic particle inspection on the impeller after processing to ensure that there are no crack defects; S105: According to the dynamic balancing requirements of the low-pressure rotor 1 of the steam turbine, install an adjustable counterweight / balancing block (not shown in the figure) in the dovetail groove 33, and the counterweight is fixed by a locking bolt.

[0028] In addition, the turning depth tolerance and surface roughness must be controlled to avoid stress concentration.

[0029] The step S2 also includes the following steps: S201: identifying multiple preceding impellers 4 on the low-pressure rotor 1 of the steam turbine, where the original preceding impellers 4 are provided with outward-wrapped inverted T-shaped blade roots 42 or outward-wrapped double inverted T-shaped blade roots 41; S202: turning the outward-wrapped inverted T-shaped blade roots 42 and outward-wrapped double inverted T-shaped blade roots 41 on the multiple preceding impellers 4 until the chamfers or fillets of the blade roots are outwardly wrapped to reduce their outer envelope size.

[0030] The step S3 also includes the following steps: S301: Check the inner surface of the low-pressure inner cylinder corresponding to the impeller modification area; S302: Grind the sharp edges, protrusions, etc. in the inner cylinder to make them transition smoothly to form chamfers or rounded corners; S303: Effectively seal the holes in the inner cylinder that may cause airflow turbulence, such as guide holes, partition grooves, etc.

[0031] After the above transformation is completed in step S4, a dynamic balancing test is performed on the entire steam turbine low-pressure rotor 1 in accordance with relevant standards (such as GB / T9239.12) to ensure that its balancing accuracy meets the requirements.

[0032] In addition, the low-pressure rotor of the steam turbine is cleaned according to relevant cleanliness standards (such as JB / T4058).

[0033] The step S5 further includes the following steps: S501: reinstalling the qualified low-pressure rotor of the steam turbine into the steam turbine; S502: performing a running test in the steam turbine to monitor and confirm that the noise value has been reduced to a qualified range.

[0034] By changing the balancing method of the last-stage impeller, trimming the outer envelope profile of the preceding impeller, and optimizing the inner cylinder flow field, the blast and airflow friction noise generated by the impeller is effectively suppressed, and the turbine operating noise is reduced to an acceptable range. At the same time, the processing volume is small and highly targeted. The modification plan focuses on the suspected area of ​​the noise source. The last-stage impeller uses a dovetail groove balancing block to replace the original balancing structure, and the remaining impellers only undergo a small amount of processing on the outer envelope, avoiding further large-scale modifications to the impeller body and the blades themselves.

[0035] The rotor's structural stability is maintained: minimal machining effort has minimal impact on the rotor's overall mass distribution and stiffness (lift), ensuring the rotor's dynamic characteristics remain close to the original design, facilitating stable operation. The relatively minimal structural changes to the modified rotor facilitate reinstallation and subsequent dynamic balancing, reducing on-site installation and commissioning workload. The overall solution is highly operational, with relatively simple machining and processing steps, facilitating noise reduction within the tight maintenance schedule. Simultaneously, treatment of sharp areas and sealing of holes in the low-pressure inner cylinder stabilize the flow field within the cylinder, reducing airflow impact and turbulence losses, further aiding noise reduction and improving the turbine's overall operating efficiency.

[0036] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. The low-damage and noise-reducing structure of the steam turbine low-pressure rotor is characterized by: It includes a low-pressure rotor of a steam turbine and a pair of wheels at the end of the low-pressure rotor of the steam turbine. The circumference of the low-pressure rotor of the steam turbine is provided with a final-stage impeller and multiple preceding impellers. The final-stage impeller and multiple preceding impellers are symmetrically arranged on the low-pressure rotor of the steam turbine. The outside of the final-stage impeller is provided with a step, and the side of the step is provided with a dovetail groove. The circumference of the multiple preceding impellers is flat and chamfered or rounded on both sides.

2. A method for improving a low-damage noise reduction structure of a steam turbine low-pressure rotor, characterized in that: It includes the following steps: S1: modification of the last stage impeller; S2: modification of the preceding impeller; S3: optimization of the low-pressure inner cylinder flow field; S4: overall processing of the rotor; S5: reinstallation and testing.

3. The method for improving the low-damage noise reduction structure of the steam turbine low-pressure rotor according to claim 2, characterized in that: The step S1 also includes the following steps: S101: Identify the last-stage impeller on the low-pressure rotor of the steam turbine; S102: Turn the balancing hole and balancing screw plug on the outside of the original last-stage impeller to form a step; S103: Process at least one dovetail groove axially on the step side of the last-stage impeller; S104: Perform magnetic particle inspection on the blade root after processing to ensure that there are no crack defects; S105: According to the dynamic balancing requirements of the low-pressure rotor of the steam turbine, install an adjustable counterweight block in the dovetail groove, and the counterweight block is fixed by a locking bolt.

4. The method for improving the low-damage noise reduction structure of the steam turbine low-pressure rotor according to claim 2, characterized in that: The step S2 also includes the following steps: S201: identifying multiple preceding impellers on the low-pressure rotor of the steam turbine, where the original preceding impellers are provided with outward-wrapped inverted T-shaped blade roots or outward-wrapped double inverted T-shaped blade roots; S202: turning the outward-wrapped inverted T-shaped blade roots and outward-wrapped double inverted T-shaped blade roots on the multiple preceding impellers until the chamfers or rounded corners of the blade roots are outwardly wrapped.

5. The method for improving the low-damage noise reduction structure of the steam turbine low-pressure rotor according to claim 2, characterized in that: The step S3 also includes the following steps: S301: Check the inner surface of the low-pressure inner cylinder corresponding to the impeller modification area; S302: Grind the sharp edges, protrusions, etc. in the inner cylinder to make them transition smoothly to form chamfers or rounded corners; S303: Seal the holes, guide holes, and pressure isolation plate grooves in the inner cylinder.

6. The method for improving the low-damage noise reduction structure of the steam turbine low-pressure rotor according to claim 2, characterized in that: The overall rotor treatment in step S4 is to perform a dynamic balancing test on the entire low-pressure rotor of the steam turbine to ensure that its balancing accuracy meets the requirements; in addition, the low-pressure rotor of the steam turbine needs to be cleaned.

7. The method for improving the low-damage noise reduction structure of the steam turbine low-pressure rotor according to claim 2, characterized in that: The step S5 further includes the following steps: S501: reinstalling the qualified low-pressure rotor of the steam turbine into the steam turbine; S502: performing a running test in the steam turbine to monitor and confirm that the noise value has been reduced to a qualified range.

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