Overall planning and optimization design method for runner diameter ratio and water bucket number of pelton turbine

Abstract

The invention relates to a pelton turbine runner diameter ratio and pelton number overall planning optimization design method, and belongs to the field of hydraulic machinery. According to an optimization design principle, changing a water bucket design reference position, and anticlockwise rotating a conventional water bucket design reference position by a half of a water bucket included angle delta theta; the outer diameter Dh and the radius Rh of the water diversion blade are determined according to the newly-arranged design reference position of the water buckets, so that it is guaranteed that under the diameter of the notch, when any one water bucket passes through the design reference position, water cannot be ejected out of the water bucket; and calculating the diameter ratio bd of the runner according to the water bucket number Zd, and sequentially changing the water bucket number Zd to obtain an optimal matching relation table of the diameter ratio bd of the runner along with the change of the water bucket number Zd. By optimizing the matching relation among the pitch circle diameter of the runner of the pelton turbine, the jet flow water column diameter and the number of the pelton, the proper number of the pelton is selected, and the water torque of the jet flow impacting the pelton is increased, so that higher hydraulic efficiency is obtained.

Description

Technical Field

[0001] This invention relates to the field of hydraulic machinery technology, specifically to a method for the overall optimization design of the runner diameter ratio and the number of buckets in a bucket turbine. Background Technology

[0002] The bucket turbine is the most common type of impulse turbine. Unlike the reaction turbine, the impulse turbine is less widely used, and its design principles and methods are not studied in depth. More importantly, the flow within the runner of an impulse turbine is not pressurized. Most of the theories and methods developed for pressurized flow cannot be applied to this type of turbine, posing significant challenges to improving its output, efficiency, and other performance characteristics.

[0003] Similar to reaction turbines, the current design principle of impulse turbines is based on the assumption that the number of blades (or "number of buckets" for bucket turbines) is infinite. This is then modified to take into account the impact of a finite number of blades.

[0004] In the limited literature on impulse turbines, most scholars believe that, given a fixed power station head, flow rate, and unit speed, increasing the runner pitch circle diameter is the best approach. D 1. Increase the number of water buckets Z d This is beneficial for improving runner efficiency. As a result, newly designed bucket turbines currently have a runner pitch circle diameter... D 1. Gradually increase, number of water buckets Z d The increasing number of buckets in current bucket turbines limits the improvement of their efficiency. For example, the number of buckets in current bucket turbines... Z d Some have as many as 30 water buckets, which is very crowded. The selection of the number of water buckets did not take into account the coordination and influence with other parameters. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a method for comprehensively optimizing the runner diameter ratio and the number of buckets in a bucket turbine, thereby solving the problem of runner pitch circle diameter in newly designed bucket turbines. D 1. Gradually increase, number of water buckets Z d The increasing trend has limited the improvement of the efficiency of bucket turbines.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention discloses a method for the overall optimization design of the runner diameter ratio and the number of buckets in a bucket turbine, comprising: Step 1: Determine the optimization design principle, namely: a jet of water should only impact one water bucket at the designed location, and at most two water buckets. Step Two: Based on the optimization design principle, change the reference position of the water bucket design by rotating the conventional water bucket design reference position counterclockwise by half the included angle Δ of the water bucket. i , where Δ i =π / Z d , Z d The number of water buckets; Step 3: Determine the outer diameter of the water-dividing blade based on the design reference position of the newly set water hopper. D h and water-dividing blade radius R h This is to ensure that, within the diameter of the notch, water will not be ejected from any of the water buckets when they pass the design reference position; Step 4: Based on the number of water buckets Z d Calculate the diameter ratio of the runner b d The diameter of the rotor is greater than that of the rotor. b d The pitch circle diameter of the runner D 1 and the diameter of the jet water column d The ratio of 0; change the water bucket number in sequence Z d To obtain the ratio of the rotor diameter b d Follow the water bucket number Z d A table of optimal matching relationships for varying conditions; where selection can be made based on the rigidity requirements of the power station. b d and the number of matching water buckets Z d .

[0007] Wherein, the outer diameter of the water-dividing blade D h The expression is: D h =( D 1+ d 0) / cos(2π / (2 Z d ))= ( D 1+ d 0) / cos(π / Z d ) In the formula, D h The outer diameter of the water-dividing blade; D1 represents the pitch circle diameter of the impeller; d 0 represents the diameter of the jet water column; Z d The number of water buckets.

[0008] The radius of the water-dividing blade R h The expression is: R h =0.5 D h =0.5( D 1+ d 0) / cos(π / Z d ) In the formula, R h The radius of the water-dividing blade; D 1 represents the pitch circle diameter of the impeller; d 0 represents the diameter of the jet water column; Z d The number of water buckets.

[0009] Preferably, the obtained rotor diameter ratio b d Follow the water bucket number Z d The process of creating the optimal matching table involves the following specific steps: Step 41: Based on the number of water buckets Z d Calculate the angle of wrapping of a single water bucket i and half-water bucket corner Δ i , Among them, single water bucket corner i =2π / Z d , Z d The number of water buckets; Half-water bucket corner Δ i =2π / (2 Z d )= i / 2, Z d The number of water buckets; Step 42: Based on the single water bucket angle i and half-water bucket corner Δ i Calculate the ratio of the rotor diameter b d , Wherein, the diameter ratio of the rotating wheel bd The expression is: b d =2cos(Δ i ) / (cos(0.5 i )- cos(1.5 i ))-1 In the formula, b d The ratio of the rotor diameter, b d = D 1 / d0, where D 1 represents the pitch circle diameter of the impeller. d 0 represents the diameter of the jet water column; Δ i It is a half-water bucket corner; i It is a single water bucket with a corner; Step 43: Change the number of water buckets sequentially. Z d Repeat steps 41 and 42 respectively to obtain the rotor diameter ratio. b d Follow the water bucket number Z d A changing optimal matching table.

[0010] Compared with the prior art, the present invention has the following beneficial effects: (I) This invention relates to a method for the overall design of the runner diameter ratio and number of buckets in a bucket turbine, comprising: determining the design principles; and, based on the design principles, changing the bucket design reference position by rotating the conventional bucket design reference position counterclockwise by half a bucket angle Δ. i The original outer diameter and radius of the water-dividing blade were modified to determine the modified outer diameter of the water-dividing blade. D h and the corrected water-dividing blade radius R h This ensures that, within the opening diameter, water will not eject from any of the water buckets when they pass the design reference position; based on the number of water buckets... Z d Calculate the diameter ratio of the runner b d The diameter of the rotor is greater than that of the rotor. b d The pitch circle diameter of the runner D 1 and the diameter of the jet water column d The ratio of 0; change the water bucket number in sequence Z d To obtain the ratio of the rotor diameter b d Follow the water bucket number Zd The optimal matching relationship table varies. This invention increases the hydraulic torque of the jet impacting the water buckets by optimizing the proportional relationship between the runner pitch circle diameter, the jet water column diameter, and the number of water buckets in a bucket turbine, thereby achieving higher hydraulic efficiency.

[0011] (II) This invention relates to a method for comprehensively optimizing the runner diameter ratio and the number of buckets in a bucket turbine, which is a method for comprehensively optimizing the runner pitch circle diameter. D 1. Diameter of the jet water column d 0. Number of water buckets Z d The design method for the relationship between the three elements involves a single water jet impacting one bucket at a designated location, while at other locations, a single water jet impacts a maximum of two buckets. This optimized design reduces the number of buckets impacted simultaneously by a single jet, ensuring that all buckets are fully utilized and perform better work, thereby improving the efficiency of the bucket turbine.

[0012] Furthermore, the present invention also has the following advantages: (1) The design concept proposed in this method, which is to spray only one water bucket at the best location and at most two water buckets, is clear and logically sound. (2) This patent is the first to propose a design method that takes into account both the selection of the number of water buckets and the ratio of the rotor diameter, which reduces the randomness of the selection of the number of water buckets and increases its rationality.

[0013] (3) The designed water bucket can change the original design of no jet at the root, which can improve efficiency and extend the service life of the impeller. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a jet of water impacting two buckets in a conventionally designed bucket turbine with an excessive number of buckets. Z d =21, Rotor diameter ratio b d =12.14.

[0015] Figure 2 This is a schematic diagram of a jet of water impacting three buckets in a conventionally designed bucket turbine. The number of buckets in this conventionally designed bucket turbine is... Z d =21, Rotor diameter ratio b d =12.14.

[0016] Figure 3 yes Figure 2 A magnified view of the upper jet of water simultaneously impacting three water buckets.

[0017] Figure 4 This is a schematic diagram of a jet of water impacting 1-2 buckets in a bucket turbine with a bucket number and runner diameter ratio adapted according to Embodiment 1 of the present invention. The number of buckets in this embodiment 1 is... Z d =17. Rotor diameter ratio b d =13.81. Detailed Implementation

[0018] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0019] The design principle of impulse turbines is also based on the assumption of an infinite number of blades. Existing literature mostly believes that increasing the runner pitch circle diameter is the best approach. D 1. Increase the number of water buckets Z d While it is beneficial to improve the efficiency of the impeller, it does not take into account the interaction between the impeller diameter and the number of water buckets, and increasing the number of water buckets is a very one-sided approach.

[0020] Our new research demonstrates that the assumption of an infinite number of buckets is not optimal for impulse turbines. For reaction turbines, water can flow through even the narrowest flow channels between the blades. However, in a bucket turbine with an infinite number of buckets, the jet of water only impacts the outer edge of the rotating buckets that pass through the jet's range—a relatively inefficient part of the bucket system, resulting in very low efficiency. Therefore, an infinite number of buckets cannot be pursued as a design principle, as is the case with reaction turbines.

[0021] Therefore, the selection of the number of water buckets needs to be optimized, and it cannot be increased unilaterally. Even without considering increasing the pitch circle diameter of the impeller... D 1 and increase the number of water buckets Z d The subsequent increase in cost, solely based on considerations of improving efficiency, unilaterally increased the pitch circle diameter of the impeller. D 1 or water bucket number Z d Neither of these methods is an effective way to improve efficiency; instead, the pitch circle diameter of the impeller should be considered holistically. D 1. Diameter of the jet water column d 0. Number of water buckets Z dThe interaction effects were analyzed to optimize the most efficient matching parameters, and then other structural parameters were designed and determined while considering the high strength requirements of the impeller. This was especially true when unilaterally increasing the number of water buckets... Z d Subsequently, due to overcrowding of the water buckets, undesirable phenomena may occur, such as a single jet of water impacting two or more water buckets simultaneously, or water only entering the upper part of the water bucket. Figure 1 and Figure 2 As shown.

[0022] in, Figure 1 The image shows a jet of water simultaneously impacting two water buckets. Figure 2 and its enlarged image— Figure 3 The image shows a single jet of water simultaneously impacting three water buckets, including the first, second, and third water buckets. Figure 3 As shown, this significantly reduces efficiency. Figure 2 Comparison Figure 1 All water jets rotate counterclockwise. α =2° (positive with clockwise rotation), where the angle between water bucket #21 and +Y is... i 21 =6.57°, the angle between water bucket #1 and +Y i 1 = -10.57°, the angle between water bucket #2 and +Y. i 2 = -25.71°. Assume the diameter of the jet water column... d 0=1, water-dividing blade radius R h =6.6442, maximum projected radius R max =6.57, minimum projected radius R min =5.57. The projected radii of these three water buckets in the +Y direction. R y They are: R 21 =6.6, R y1 =6.531, R y2 =5.986. Because R y1 < R max This indicates that some water bypassed water hopper 1 and entered water hopper 21; while R min < R y2 < R max This indicates that the water jet impacted water bucket number 2, and some water impacted the water bucket in front; this fully demonstrates that at this water bucket location, the jet water jet impacted at least 3 water buckets simultaneously.

[0023] Therefore, this invention proposes a completely new design concept and a completely new design method.

[0024] Example 1: A method for the overall optimization design of the runner diameter ratio and number of buckets in a bucket turbine. To improve the efficiency of bucket turbines, the runner pitch circle diameter was comprehensively optimized. D 1. Diameter of the jet water column d 0. Number of water buckets Z d Regarding the relationship between these three factors, Embodiment 1 of this invention provides a method for the overall optimization design of the runner diameter ratio and the number of buckets in a bucket turbine, including the following steps: Step 1: Determine the optimization design principle, namely: a jet of water should only impact one water bucket at the designed location, and at most two water buckets.

[0025] The rationale for this design principle is as follows: even in the optimal position, no water bucket should be impacted; in some positions, three or four water buckets may be impacted simultaneously; all water buckets should not be fully filled at any time or in any position; and each water bucket should only be used on its outermost (radius) side. R The larger half of the scoop is impacted by the jet of water, and the inflow conditions differ significantly from the design, resulting in a substantial decrease in actual efficiency. This is because the jet of water only impacts the outer perimeter of the scoop (radius). R Larger parts (such as the lower part) have the greatest impact on the safety of the water bucket, while the lower part (radius) is rarely impacted. R Smaller, less sensitive safety areas are more prone to fracture at the bucket root due to large impact torque, posing a greater threat to the safe operation of the bucket system. While the new design cannot completely eliminate the issue of more impact on the outer perimeter of the buckets and less impact on the bucket root, it is a significant improvement over conventional designs and can extend the runner's service life to some extent. This is essentially equivalent to cutting a notch around the runner of a bucket turbine; the purpose of the notch is to minimize obstruction of the jet stream by the lower buckets, allowing the jet stream to impact more effectively on the front buckets and output greater power.

[0026] As one specific implementation method, in the design location (see...) Figure 4 (Upper part) A jet of water only impacts one water bucket; in other locations (see...) Figure 4 (Lower part) A single jet of water can only impact a maximum of two water buckets.

[0027] Step Two: Based on the optimization design principle, change the reference position of the water bucket design by rotating the conventional water bucket design reference position counterclockwise by half the included angle Δ of the water bucket. i , where Δ i =π / Z d , Z d The number of water buckets; Under the assumption of an infinite number of water buckets, the design reference position of the water buckets is usually defined as the vertical entry of the jet water column into the water bucket, such as... Figure 1 The position of the water buckets in the -Y direction is shown. Given the number of water buckets... Z d Under these conditions, the design reference position of the water bucket should be rotated counterclockwise by Δ. i =0.5 i ,like Figure 4 Rotate counterclockwise in the +Y direction by Δ i The corresponding water bucket position.

[0028] The reason for changing the reference position of the water bucket design is: if designed according to the reference position defined by conventional design, and the outer diameter of the water-dividing blade is... D h (Or, "outer diameter at the bucket opening") is equal to the pitch circle diameter of the impeller. D 1 and the diameter of the jet water column d If the sum of 0 and 0, then when the water bucket leaves the designed position, some water will be ejected from the turbine through the opening at the top of the water bucket without doing any work, resulting in power generation loss.

[0029] Step 3: Determine the outer diameter of the water-dividing blade based on the design reference position of the newly set water hopper. D h and water-dividing blade radius R h This ensures that, within the diameter of the notch, water will not be ejected from any of the buckets when they pass the design reference position.

[0030] Specifically, the outer diameter of the water-dividing blade D h The expression is: D h =( D 1+ d 0) / cos(2π / (2 Z d )) = ( D 1+ d 0) / cos(π / Z d ) In the formula, D h The outer diameter of the water-dividing blade; D 1 represents the pitch circle diameter of the impeller; d 0 represents the diameter of the jet water column; Z d The number of water buckets.

[0031] Specifically, the radius of the water-dividing blade Rh The expression is: R h =0.5 D h =0.5( D 1+ d 0) / cos(π / Z d ) In the formula, R h The radius of the water-dividing blade; D 1 represents the pitch circle diameter of the impeller; d 0 represents the diameter of the jet water column; Z d The number of water buckets.

[0032] Step 4: Based on the number of water buckets Z d Calculate the diameter ratio of the runner b d The diameter of the rotor is greater than that of the rotor. b d The pitch circle diameter of the runner D 1 and the diameter of the jet water column d The ratio of 0; change the water bucket number in sequence Z d To obtain the ratio of the rotor diameter b d Follow the water bucket number Z d The optimal matching relationship table varies; the runner diameter ratio is selected from the optimal matching relationship table according to the power station's rigidity requirements. b d and the number of matching water buckets Z d This includes the following specific steps: Step 41: Based on the number of water buckets Z d Calculate the angle of wrapping of a single water bucket i and half-water bucket corner Δ i ; Among them, single water bucket corner i =2π / Z d , Z d The number of water buckets; Half-water bucket corner Δ i =2π / (2 Z d )= i / 2, Z d The number of water buckets; Step 42: Based on the single water bucket angle i and half-water bucket corner Δ i Calculate the ratio of the rotor diameter b d , Wherein, the diameter ratio of the rotating wheel b d The expression is: b d =2cos(Δ i ) / (cos(0.5 i )- cos(1.5 i ))-1 In the formula, b d The ratio of the rotor diameter, b d = D 1 / d0, where D 1 represents the pitch circle diameter of the impeller. d 0 represents the diameter of the jet water column; Δ i It is a half-water bucket corner; i It is a single water bucket with corner protection.

[0033] Step 43: Change the number of water buckets sequentially. Z d Repeat steps 41 and 42 respectively to obtain the rotor diameter ratio. b d Follow the water bucket number Z d The optimal matching relationship table for the changes is shown in Table 1: Table 1 Number of Water Buckets Z d Ratio to wheel diameter b d Optimal matching table

[0034] It should be noted that the diameter of the jet water column d 0 is not the nozzle outlet diameter. d j It is not the actual diameter of the jet water column, but the actual diameter of the jet water column. d 0 According to the water head H ,flow Q and number of nozzles Z p The theoretical value is calculated to be: d 0 = (4 × Q / (π× Zp ×(2 g × H ) 1 / 2 )) 1 / 2 In the formula, d 0 represents the diameter of the jet water column; Q For traffic; Z p Number of nozzles; H For water head.

[0035] The diameter of the designed water jet should be slightly larger than the theoretical value because the water jet will scatter slightly in the air.

[0036] The optimal runner diameter ratio is described below. b d Detailed calculation steps: 1. Calculate the single water bucket wrap angle i : i =2π / Z d (Equation 1) 2. Calculate the radius of the water-dividing blade in the water bucket. R h : R h =0.5 ( b d +1) d 0 / cos(0.5) i (Equation 2) 3. Calculate separately Figure 4 Water bucket number 1 (in 0.5) i (location) and No. 2 water bucket (at 1.5) i The projection of the radius of the notch in the vertical direction, such as Figure 4 As shown, that is: R y1 = R h ·cos(0.5 i (Equation 3) R y2 = R h ·cos(1.5 i (Equation 4) Calculate the difference between (Equation 3) and (Equation 4). Δ R y = R y1 -R y2 = R h ·(cos(0.5 i )- cos(1.5 i (Formula 5) 4. Let the difference Δ between the projected radii of the two water buckets be... R y and the diameter of the jet water column d 0 is equal, and substituting equation (2) into it, we can obtain 0.5 ( b d +1)· d 0·(cos(0.5 i )- cos(1.5 i )) / cos(0.5 i )= d 0 (Equation 6) Then we obtain the formula for calculating the ratio of the rotor diameters. b d =2 cos(0.5 i ) / (cos(0.5 i )- cos(1.5 i ))-1 (Equation 7) Different water bucket numbers Z d and the corresponding corner i Substituting into the formula for calculating the runner diameter ratio in Equation 7, we can obtain the corresponding optimal runner diameter ratio. b d .

[0037] This invention relates to a method for comprehensively optimizing the runner diameter ratio and the number of buckets in a bucket turbine, specifically for comprehensively optimizing the runner pitch circle diameter. D 1. Diameter of the jet water column d 0. Number of water buckets Z d The design method for the relationship between the three, such as in the design location (see Figure 4 (Upper part) A jet of water only impacts one water bucket; in other locations (see...) Figure 4 (Lower section) A single jet of water impacts a maximum of two buckets. This optimized design reduces the number of buckets impacted by a single jet, allowing all buckets to be fully utilized and perform better work, with the aim of improving the efficiency of the bucket turbine.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the integrated optimization design of the runner diameter ratio and the number of buckets in a bucket turbine, characterized in that, include: Step 1: Determine the optimization design principle, namely: a jet of water should only impact one water bucket at the designed location, and at most two water buckets. Step Two: Based on the optimization design principle, change the reference position of the water bucket design by rotating the conventional water bucket design reference position counterclockwise by half the included angle Δ of the water bucket. θ , where Δ θ =π / Z d , Z d The number of water buckets; Step 3: Determine the outer diameter of the water-dividing blade based on the design reference position of the newly set water hopper. D h and water-dividing blade radius R h This is to ensure that, within the diameter of the notch, water will not be ejected from any of the water buckets when they pass the design reference position; Step 4: Based on the number of water buckets Z d Calculate the diameter ratio of the runner b d The diameter of the rotor is greater than that of the rotor. b d The pitch circle diameter of the runner D 1 and the diameter of the jet water column d The ratio of 0; change the water bucket number in sequence Z d To obtain the ratio of the rotor diameter b d Follow the water bucket number Z d A changing optimal matching table.

2. The method according to claim 1, characterized in that, The radius of the water-dividing blade R h The expression is: R h =0.5( D 1+ d 0) / cos(π / Z d ) In the formula, R h The radius of the water-dividing blade; D 1 represents the pitch circle diameter of the impeller; d 0 represents the diameter of the jet water column; Z d The number of water buckets.

3. The method according to claim 1, characterized in that, The obtained rotor diameter ratio b d Follow the water bucket number Z d The process of creating the optimal matching table involves the following specific steps: Step 41: Based on the number of water buckets Z d Calculate the angle of wrapping of a single water bucket θ and half-water bucket corner Δ θ , Among them, single water bucket corner θ =2π / Z d , Z d The number of water buckets; Half-water bucket corner Δ θ =2π / (2 Z d )= θ / 2, Z d The number of water buckets; Step 42: Based on the single water bucket angle θ and half-water bucket corner Δ θ Calculate the ratio of the rotor diameter b d , Wherein, the diameter ratio of the rotating wheel b d The expression is: b d =2cos(Δ θ ) / (cos(0.5 θ )- cos(1.5 θ ))-1 In the formula, b d The ratio of the rotor diameter, b d = D 1 / d0, where D 1 represents the pitch circle diameter of the impeller. d 0 represents the diameter of the jet water column; Δ θ It is a half-water bucket corner; θ It is a single water bucket with a corner; Step 43: Change the number of water buckets sequentially. Z d Repeat steps 31 and 32 respectively to obtain the rotor diameter ratio. b d Follow the water bucket number Z d A changing optimal matching table.

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