JP3353668B2 - Erosion prediction method for hydraulic machinery - Google Patents
Erosion prediction method for hydraulic machineryInfo
- Publication number
- JP3353668B2 JP3353668B2 JP28158897A JP28158897A JP3353668B2 JP 3353668 B2 JP3353668 B2 JP 3353668B2 JP 28158897 A JP28158897 A JP 28158897A JP 28158897 A JP28158897 A JP 28158897A JP 3353668 B2 JP3353668 B2 JP 3353668B2
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- Prior art keywords
- erosion
- vorticity
- cavitation
- predicting
- flow
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Aerodynamic Tests, Hydrodynamic Tests, Wind Tunnels, And Water Tanks (AREA)
- Control Of Non-Positive-Displacement Pumps (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、水車、ポンプ、舶
用プロペラ、等の水力機械や弁、絞り等の水力機器や油
圧機器において、キャビテーションにより発生する壊食
を運転前に事前にその発生の有無を予測する水力機械の
壊食予測法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the prevention of erosion caused by cavitation in hydraulic machines such as water turbines, pumps, marine propellers, etc., and hydraulic equipment such as valves and throttles before operation. The present invention relates to a method for predicting erosion of a hydraulic machine for predicting the presence or absence of erosion.
【０００２】[0002]
【従来の技術】代表例としてポンプについて述べるが、
他の水力機械・機器や油圧機器についても同様である。
従来は次のような方法により壊食の発生の有無の予測を
行っている。2. Description of the Related Art A pump will be described as a typical example.
The same applies to other hydraulic machines / equipment and hydraulic equipment.
Conventionally, the presence or absence of erosion is predicted by the following method.
【０００３】（１）実機ポンプと同じ全揚程を持つ小形
モデルポンプを製作し、ある時間本ポンプをキャビテー
ションが発生する条件で連続運転して壊食を発生させ、
その壊食痕に基づき実機の壊食を予測する。本方法によ
れば極めて高い実機壊食の予測精度を得ることができ
る。(1) A small model pump having the same total head as the actual pump is manufactured, and the pump is continuously operated for a certain period of time under the condition that cavitation occurs to cause erosion.
Erosion of the actual machine is predicted based on the erosion marks. According to this method, it is possible to obtain extremely high prediction accuracy of actual machine erosion.
【０００４】（２）ポンプのケーシングの振動加速度を
測定し、別途、従来実績の振動加速度と壊食との関係を
調査して整理された資料から、その振動加速度に対応す
る材質別の壊食速度を求め、実機条件下での壊食を予測
する方法である。本方法によれば測定が短時間で安価に
実現可能のため、本法は実用性が高い予測法である。[0004] (2) The vibration acceleration of the casing of the pump is measured, and the relationship between the vibration acceleration and the erosion obtained in the past is separately investigated. This is a method of calculating the speed and predicting erosion under actual machine conditions. According to the present method, the measurement can be realized in a short time and at low cost, and therefore, the present method is a highly practical prediction method.
【０００５】本方法を適用した事例として特公平６−１
００１９８号公報記載の「ポンプの寿命予測法」があ
る。As an example of applying this method, Japanese Patent Publication No. 6-1
There is a "pump life prediction method" described in Japanese Patent Publication No. 00198.
【０００６】[0006]
【発明が解決しようとする課題】上記（１）の従来技術
においては次のような問題点がある。すなわち、小形モ
デルポンプの製作及び連続運転を行うためには多大の経
費と時間を必要とする。一方、（２）の従来技術におい
ては経費と時間は（１）の技術に比べ格段に少額の経費
と時間で壊食の予測を行うことができるが、精度の高い
振動加速度と壊食の関係データを得ることは困難で、予
測精度が低くなるという問題がある。The prior art (1) has the following problems. That is, a large amount of cost and time are required to manufacture and continuously operate a small model pump. On the other hand, in the prior art of (2), the erosion can be predicted with much less cost and time than the technique of (1). It is difficult to obtain data, and there is a problem that prediction accuracy is low.
【０００７】本発明は、ポンプ等の水力機械に発生する
キャビテーションによる壊食を、乱流解析等で得られる
渦度分布から、事前に壊食発生の可能性を予測する水力
機械の壊食予測方法を提供することを目的とする。According to the present invention, the erosion caused by cavitation generated in a hydraulic machine such as a pump is predicted from the vorticity distribution obtained by turbulence analysis or the like, and the erosion prediction of the hydraulic machine is predicted in advance. It aims to provide a method.
【０００８】[0008]
【課題を解決するための手段】上記目的は、水力機械の
内部流路にキャビテーションにより発生する壊食を予測
する方法において、水力機械の内部流れの乱流解析を行
って渦度分布を求め、その渦度がある数値以上において
は壊食が発生すると判定する、ことによって達成され
る。An object of the present invention is to provide a method for predicting erosion caused by cavitation in an internal flow path of a hydraulic machine, performing a turbulence analysis of an internal flow of the hydraulic machine to obtain a vorticity distribution, This is achieved by determining that erosion occurs when the vorticity exceeds a certain numerical value.
【０００９】水力機械で激しい壊食が生じて問題となる
なる場合は、通常、低流量域で羽根車入口付近に生ずる
ような渦状のキャビテーションが発生している場合が多
い。この渦状キャビテーションの発生と羽根面上の渦度
の大きさとには良好な相関関係がある。このような壊食
性の強い渦状キャビテーションの発生を設計図に基づき
事前に予測できれば、激しい壊食の発生の有無も高精度
で予測できることになる。そこで、水力機械の内部流れ
を乱流解析により流路壁面上の渦度を求め、ある数値以
上の領域は渦状のキャビテーションひいては壊食が発生
する可能性が極めて高いと予測する。[0009] When severe erosion occurs in a hydraulic machine and becomes a problem, vortex-like cavitation usually occurs near the impeller inlet in a low flow rate region in many cases. There is a good correlation between the occurrence of the spiral cavitation and the magnitude of the vorticity on the blade surface. If the occurrence of such highly erosive spiral cavitation can be predicted in advance based on a design drawing, the presence / absence of severe erosion can be predicted with high accuracy. Therefore, the vorticity on the channel wall surface is obtained by turbulence analysis of the internal flow of the hydraulic machine, and it is predicted that the possibility of vortex-like cavitation and thus erosion is extremely high in a region exceeding a certain numerical value.
【００１０】[0010]
【発明の実施の形態】図１は水力機械・機器に関する実
施例の壊食予測法のフロー線図である。本実施例につい
ても、ポンプについて代表例として説明する。の段階
においては、ポンプ内部のキャビテーションが発生して
いない状態での流れを乱流解析にて求める。その際、キ
ャビテーション強さが設計点より大きくなる低流量域に
ついてより詳細に解析する。次にの段階においては、
（数１）、（数２）で定義される流路壁面上の渦度ｑの
大きさの分布を乱流解析結果から等高線の形で求め表示
する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart of an erosion prediction method according to an embodiment relating to hydraulic machines and equipment. Also in this embodiment, a pump will be described as a representative example. In the step (2), the flow in a state where no cavitation occurs inside the pump is obtained by turbulence analysis. At that time, a more detailed analysis is performed on the low flow rate region where the cavitation intensity is larger than the design point. In the next stage,
The distribution of the magnitude of the vorticity q on the flow path wall defined by (Equation 1) and (Equation 2) is obtained and displayed in the form of contour lines from the turbulence analysis results.
【００１１】[0011]
【数１】 (Equation 1)
【００１２】[0012]
【数２】 (Equation 2)
【００１３】ここに、ｑx、ｑy、ｑz は、それぞれ渦度
ｑのｘ，ｙ，ｚ軸方向の成分である。また、ｕ，ｖ，ｗ
は、それぞれ流速Ｖのｘ，ｙ，ｚ軸方向の成分である。
渦度は流れの回転運動を表す量で、大きさと方向を持つ
ベクトル量である。微小部分の回転角速度の２倍の値を
持っている。従って、渦度は流れの中に発生する渦の大
きさを表す尺度と考えることができる。次にの段階で
は、別途、壊食が生じた種々のポンプについて乱流解析
から得た渦度ｑとその壊食痕から後述する（数３）で定
義されるキャビテーション強さＩとの関係からで得た
渦度ｑに対するキャビテーション強さＩを求める。の
段階においてはで得られたキャビテーション強さＩか
ら壊食の侵食速度ＥＲを後述の（数５）にて求め、壊食
の程度が定量的に予測される。Here, q x , q y , and q z are components of the vorticity q in the x, y, and z axis directions, respectively. U, v, w
Are the components of the flow velocity V in the x, y, and z axis directions, respectively.
The vorticity is a quantity representing the rotational movement of a flow, and is a vector quantity having a magnitude and a direction. It has twice the value of the angular speed of rotation of the minute part. Therefore, the vorticity can be considered as a measure of the size of the vortex generated in the flow. In the next stage, the vorticity q obtained from the turbulence analysis of various pumps having erosion and the cavitation intensity I defined by (Equation 3) described later from the erosion mark are separately calculated. Of the cavitation intensity I with respect to the vorticity q obtained in the above. In the step (2), the erosion rate ER of erosion is determined from the cavitation intensity I obtained by (Equation 5), and the degree of erosion is quantitatively predicted.
【００１４】以下、上述の壊食の予測法の詳細説明とし
て、羽根車内のキャビテーションと壊食と渦度の関係に
ついて説明する。ポンプ羽根車において激しい壊食が生
ずるのは、ポンプの最高効率点の流量Ｑnより低流量
側、例えば６０％Ｑn等において運転される場合であ
る。The relationship between cavitation, erosion, and vorticity in the impeller will be described below as a detailed description of the above-described erosion prediction method. Severe erosion occurs in the pump impeller when the pump is operated at a flow rate lower than the flow rate Qn at the highest efficiency point, for example, 60% Qn.
【００１５】図２、図３及び図４は低流量域における羽
根車１の入口付近の流れの様相を示す。子午面断面で
は、流れはシュラウド２側で逆流４が生じ、ハブ３側は
正流５となる。一方、羽根間流路では負圧面入口側に逆
流４が生じる。その結果、羽根車１の羽根入口付近には
羽根車１内に入る正流５と羽根車１から吸込側へ出て行
く逆流４との間に激しい渦８が生ずる。ポンプ吸込圧が
低い場合は、この渦８は渦状キャビテーションとなる。
この渦状キャビテーションは常に激しく変動し、ある時
は逆流４に乗って羽根車１の上流へ向かい、ある時は羽
根車１の羽根の圧力面６にその端面は達し、そこで崩壊
する。その結果、羽根圧力面６に激しい壊食がもたらさ
れる。FIGS. 2, 3 and 4 show aspects of the flow near the inlet of the impeller 1 in the low flow rate region. In the meridional section, a reverse flow 4 occurs on the shroud 2 side, and a positive flow 5 occurs on the hub 3 side. On the other hand, in the inter-blade flow path, a backflow 4 is generated on the negative pressure surface inlet side. As a result, a strong vortex 8 is generated near the blade inlet of the impeller 1 between the normal flow 5 entering the impeller 1 and the reverse flow 4 exiting from the impeller 1 to the suction side. When the pump suction pressure is low, the vortex 8 becomes spiral cavitation.
This spiral cavitation always fluctuates violently, and at some point rides on the backflow 4 to the upstream of the impeller 1 and at some point reaches the pressure surface 6 of the impeller blades of the impeller 1 where it collapses. As a result, severe erosion occurs on the blade pressure surface 6.
【００１６】図７はそのような渦状キャビテーションが
羽根車１内で発生したとき、羽根車１の羽根の圧力面６
に発生した激しい壊食の事例である。このように低流量
域の激しい壊食は、逆流４に基づく渦状キャビテーショ
ンによりもたらされる。FIG. 7 shows that when such a spiral cavitation occurs in the impeller 1, the pressure surface 6
This is a case of severe erosion that occurred on the island. Such severe erosion in the low flow rate region is caused by the spiral cavitation based on the backflow 4.
【００１７】このように低流量域では圧力面６の羽根入
口付近に激しい壊食が発生する可能性が高い。As described above, in the low flow rate region, there is a high possibility that severe erosion occurs near the blade inlet of the pressure surface 6.
【００１８】そこで、図７に示した壊食事例の羽根車で
ある図５に示す羽根車を持つポンプについて、設計点の
６０％流量点においての乱流解析を行った。Therefore, a turbulent flow analysis was performed on a pump having the impeller shown in FIG. 5, which is the impeller of the broken meal example shown in FIG. 7, at a 60% flow point of the design point.
【００１９】図６はその解析結果の一例で、子午面のシ
ュラウド面に平行な回転面上の相対速度ベクトルを示
す。羽根前縁付近９には圧力面６から負圧面７に回り込
みながら逆流する流れが発生していることが見られる。
この付近に渦状のキャビテーションが発生することが、
実験的な観察から確認されている。そのような渦状キャ
ビテーションにより羽根の圧力面には図５に示すような
激しい壊食の発生がもたらされるのである。FIG. 6 shows an example of the analysis result, showing a relative velocity vector on a rotation plane parallel to the shroud plane on the meridian plane. In the vicinity 9 of the leading edge of the blade, it can be seen that a flow which flows backward while flowing from the pressure surface 6 to the suction surface 7 is generated.
The vortex-like cavitation is generated around this area.
Confirmed from experimental observations. Such spiral cavitation causes severe erosion on the pressure surface of the blade as shown in FIG.
【００２０】一方、前述の乱流解析結果から算出される
（数１）（数２）の渦度は、等高線表示で、図６のよう
に表される。図においては白い部分が渦度が高く黒い部
分が渦度が低い部分である。図７の壊食領域と図８の渦
度が高い白い領域は、そのパタンが似通っている。もっ
とも領域の面積などには相違があるが、基本的な様相す
なわち、羽根前縁部では領域の幅は広く、下流側に向か
い三角形状に幅が狭まって行くという点において類似性
は極めて高い。従って、渦度の大きさと壊食には良好な
相関関係がり、渦度を評価することにより壊食の発生の
有無を評価できることになる。これは渦度は前述の通り
流れの渦の大きさを示す尺度であり、渦度が大なること
は強力な渦状のキャビテーションが発生する可能性が高
く、その結果、キャビテーションの崩壊によりもたらさ
れる壊食エネルギーも大きくなり、壊食も激しくなるた
めである。On the other hand, the vorticity of (Equation 1) and (Equation 2) calculated from the above-described turbulence analysis result is expressed by contour lines as shown in FIG. In the figure, a white portion is a portion having a high vorticity and a black portion is a portion having a low vorticity. The erosion area in FIG. 7 and the white area with high vorticity in FIG. 8 have similar patterns. Although there is a difference in the area of the region, the similarity is extremely high in the basic aspect, that is, the width of the region is wide at the leading edge of the blade, and the width decreases in a triangular shape toward the downstream side. Therefore, there is a good correlation between the magnitude of the vorticity and the erosion, and the evaluation of the vorticity makes it possible to evaluate the occurrence of erosion. As described above, vorticity is a measure of the size of vortices in a flow, and the higher the vorticity, the more likely it is that strong vortex-like cavitation will occur, resulting in the collapse of cavitation This is because the food energy increases and erosion increases.
【００２１】従って、設計段階において、設計された吸
込流路、羽根車、ディフューザあるいはボリュートケー
シングなどの組み合わせからなるポンプ内部流路につい
て乱流解析を行い、流路壁面上の渦度分布を求め、実績
データから材料別に定めた壊食発生限界渦度の値以上の
領域を調べ、その領域を特定すれば、その領域が壊食を
被る領域であると予測することができる。Therefore, in the design stage, turbulent flow analysis is performed on the pump internal flow path composed of a combination of the designed suction flow path, impeller, diffuser or volute casing, and the vorticity distribution on the flow path wall surface is obtained. If an area equal to or greater than the erosion occurrence limit vorticity value determined for each material is determined from the actual data and the area is specified, it is possible to predict that the area will be subjected to erosion.
【００２２】壊食発生限界の渦度ｑcavの値は、次のよ
うにして求める。すなわち、壊食が発生した多くの実績
ポンプについて乱流解析を行い、壊食発生領域の渦度ｑ
を求める。一方、その壊食痕の深さＥと運転時間Ｔから
（数３）にて定義されるキャビテーションの壊食に及ぼ
す強さIを求め、上述の渦度ｑとキャビテーション強さ
Ｉとの関係式（数４）やあるいは関係線図を求める。The value of the vorticity q cav at the erosion generation limit is obtained as follows. That is, turbulence analysis is performed for many actual pumps in which erosion has occurred, and the vorticity q
Ask for. On the other hand, the strength I exerted on cavitation erosion defined by (Equation 3) is obtained from the depth E of the erosion scar and the operation time T, and the above-mentioned relational expression between the vorticity q and the cavitation strength I is obtained. (Equation 4) Alternatively, a relation diagram is obtained.
【００２３】[0023]
【数３】 (Equation 3)
【００２４】[0024]
【数４】 (Equation 4)
【００２５】ここに、ｑ：渦度[1/sec], a、 b、：実績
データから定まる定数である。Here, q: vorticity [1 / sec], a, b: constants determined from actual data.
【００２６】この関係式や関係線図を用いて、解析で得
られた渦度ｑに対するキャビテーション壊食強さＩを求
め、（数５）に基づき壊食の侵食速度ＥＲを求める。The cavitation erosion strength I with respect to the vorticity q obtained by the analysis is obtained using the relational expression and the relation diagram, and the erosion erosion rate ER is obtained based on (Equation 5).
【００２７】[0027]
【数５】 (Equation 5)
【００２８】ここに、記号は（数３）に用いられている
ものと同じである。得られた侵食速度ＥＲが設計仕様の
侵食速度より大であれば、仕様を満足しないのでより耐
食性の高い材料を適用したり、羽根車形状を修正して渦
度が小さくなるように設計する必要がある。Here, the symbols are the same as those used in (Equation 3). If the obtained erosion rate ER is higher than the erosion rate of the design specification, the specification does not satisfy the specification, so it is necessary to apply a material with higher corrosion resistance or modify the impeller shape to reduce the vorticity. There is.
【００２９】以上によりポンプに発生する壊食を解析的
に机上にて予測することが可能で、壊食を回避するため
の対応策も実機製作・運転前に検討することが可能とな
り、壊食に対して信頼性の高いポンプを設計することが
可能となる。As described above, the erosion generated in the pump can be analytically predicted on the desk, and measures for avoiding erosion can be examined before the actual machine is manufactured and operated. A highly reliable pump can be designed.
【００３０】[0030]
【発明の効果】本発明によれば、水力機器の設計段階に
おいて乱流解析を行うだけで壊食の発生場所とその強さ
を予測することが可能となり、その結果、従来の壊食の
予測技術に比べ、大幅に経費、時間を縮減することがで
きる。According to the present invention, it is possible to predict the location of erosion and its intensity only by performing turbulence analysis in the design stage of hydraulic equipment. As a result, the conventional erosion prediction Expenses and time can be greatly reduced compared to technology.
【図１】本発明の壊食の予測法を説明するフロー線図。FIG. 1 is a flow chart illustrating a method for predicting erosion according to the present invention.
【図２】ポンプの低流量域で羽根車羽根入口付近に発生
する逆流及び渦状キャビテーションを示す図。FIG. 2 is a diagram showing backflow and spiral cavitation generated near the impeller blade inlet in a low flow rate region of the pump.
【図３】実施例として乱流解析を行ったポンプの羽根車
の子午面流路。FIG. 3 is a meridional plane flow path of an impeller of a pump subjected to turbulence analysis as an example.
【図４】実施例として乱流解析を行ったポンプの羽根車
の羽根間流路。FIG. 4 is a flow path between blades of a pump impeller subjected to turbulent flow analysis as an example.
【図５】実施例として乱流解析を行ったポンプの羽根車
の羽根入り口付近の流れの様相を示す図。FIG. 5 is a diagram showing a flow state near a blade inlet of a pump impeller in which a turbulent flow analysis is performed as an example.
【図６】乱流解析から得た設計流量の６０％流量点にお
ける羽根車内の相対速度ベクトル分布図。FIG. 6 is a relative velocity vector distribution diagram in an impeller at a 60% flow point of a designed flow rate obtained from turbulence analysis.
【図７】設計流量の６０％流量の低流量点で、羽根車羽
根圧力面に発生した壊食の様相を示す図。FIG. 7 is a view showing an aspect of erosion generated on an impeller blade pressure surface at a low flow point of 60% of a designed flow rate.
【図８】乱流解析から得た羽根面上の渦度分布図。FIG. 8 is a vorticity distribution diagram on a blade surface obtained from turbulence analysis.
１…羽根車、２…シュラウド、３…ハブ。 1. Impeller, 2. Shroud, 3. Hub.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平５−322714（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) G01M 9/00 F04D 15/00 ────────────────────────────────────────────────── (5) References JP-A-5-322714 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) G01M 9/00 F04D 15/00
Claims (3)
より発生する壊食を予測する方法において、水力機械の
内部流れの乱流解析を行って渦度分布を求め、その渦度
がある数値以上においては壊食が発生すると判定するこ
とを特徴とする水力機械の壊食予測法。In a method for predicting erosion caused by cavitation in an internal flow passage of a hydraulic machine, a turbulence analysis of an internal flow of the hydraulic machine is performed to obtain a vorticity distribution, and the vorticity is measured at a certain value or more. Is a method for predicting erosion of hydraulic machinery, which determines that erosion occurs.
おいて、材料の耐壊食性と壊食の侵食速度とから定義さ
れるキャビテーション強さと渦度の大きさとの関係か
ら、材料の壊食速度を予測することを特徴とする水力機
械の壊食予測法。2. The method of predicting erosion of a hydraulic machine according to claim 1, wherein the erosion resistance of the material and the erosion rate of erosion define the relationship between cavitation strength and vorticity, and the magnitude of vorticity. A method for predicting erosion of a hydraulic machine, comprising predicting an erosion speed.
おいて、材料の耐壊食性と壊食深さの侵食速度とから定
義されるキャビテーション強さと渦度の大きさとの関係
から、乱流解析で得られた渦度の大きさに対応するキャ
ビテーション強さを求め、壊食速度の設計仕様に適切な
適用材料を選定することを特徴とする水力機械の壊食予
測法。3. The method for predicting erosion of a hydraulic machine according to claim 1, wherein the turbulence is determined from the relationship between the cavitation strength defined by the erosion resistance of the material and the erosion rate of the erosion depth and the magnitude of the vorticity. A method for predicting erosion of hydraulic machinery, which determines the cavitation strength corresponding to the magnitude of vorticity obtained by flow analysis and selects the appropriate material for the erosion rate design specification.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28158897A JP3353668B2 (en) | 1997-10-15 | 1997-10-15 | Erosion prediction method for hydraulic machinery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28158897A JP3353668B2 (en) | 1997-10-15 | 1997-10-15 | Erosion prediction method for hydraulic machinery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11118662A JPH11118662A (en) | 1999-04-30 |
| JP3353668B2 true JP3353668B2 (en) | 2002-12-03 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP28158897A Expired - Fee Related JP3353668B2 (en) | 1997-10-15 | 1997-10-15 | Erosion prediction method for hydraulic machinery |
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Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4665186B2 (en) * | 2001-03-09 | 2011-04-06 | 株式会社 東北テクノアーチ | A method for identifying the threshold value of cavitation impact force specific to a material, a method for quantitatively predicting the amount of erosion caused by a cavitation jet, and a device for quantitatively predicting the amount of erosion. |
| JP7086802B2 (en) * | 2018-09-26 | 2022-06-20 | 株式会社クボタ | Maintenance method, design method, and pumping equipment of pumping equipment |
| CN117516947B (en) * | 2024-01-02 | 2024-03-15 | 西华大学 | Visualized test system and method for water pump turbine |
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