JPH0140239B2

JPH0140239B2 -

Info

Publication number: JPH0140239B2
Application number: JP57070374A
Authority: JP
Inventors: Tatsuya Ishigaki; Tetsuya Sato; Kinya Morioka; Masao Yoshida; Seiji Yanagisawa; Tomoyoshi Okamura; Yasumasa Nakawa
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1982-04-28
Filing date: 1982-04-28
Publication date: 1989-08-25
Also published as: JPS58187600A

Description

[Detailed description of the invention]

［産業上の利用分野］本発明は遠心ポンプの羽根車に関するものであ
り、特に低比速度ポンプのための改良した羽根車
を提供するものである。［従来の技術］第１図に従来のポンプの羽根車のごく一般的な
構造を示す。すなわち、１は円板状の後面シユラ
ウド２と、吸込口を備えた図示しない前面シユラ
ウドの間に配置した羽根であり、羽根車の内側か
ら外側に向けて渦巻状に伸ばしてある。また、羽
根１相互の間には渦巻状の曲状流路が形成され
る。一般的に低比速度ポンプの羽根車は羽根１の出
口幅Ａに比べて羽根車のD₀が大きく、このため
流路３内に、相隣る羽根１相互に内接する内接円
b₁，b₂を描くと、この内接円b₁，b₂は羽根車の内
側より外側に向かうにしたがい、次第にこれの径
が大きくなつている。また、羽根車のメリジアン
断面は逆に羽根車の内側より外側に向かうにした
がい減少する形状となつている。また、相隣り合う羽根に内接する円を流路内に
描くとき、流路の入口より出口に向うに従い円の
直径が、一旦大きくなつた後に小さくなるように
構成してあるものが特開昭52−69004号公報に示
してある。［発明が解決しようとする課題］第１図に示してあるものの場合は、羽根１と後
面シユラウド２、及び前面シユラウドによつて囲
まれた流路３の断面積変化が適切に選ばれていな
いため、低流量域において羽根１の表面で流水の
剥離が起き、吐出し性能を引き上げることができ
ない。特開昭52−69004号公報に示してあるものの場
合は、第１図に示してあるものよりは改善されて
いるが、隣接する両羽根間に形成される流路が充
分な長さを有してなく、流路の断面積も充分小さ
い値になつていないので、羽根の表面でやはり流
水の剥離が起こり、やはり充分に吐出性能を引き
上げることができない。また、羽根の出口角も充分小さな値に選択され
ていない。羽根の出口角が充分小さくない場合の問題点を
更に第２図を用いて説明する。第２図は横軸に吐出し量、縦軸にポンプの全揚
程、ポンプ効率、軸動力の各項目をとつたもので
ある。従来から多数の吐出し特性を持つたポンプ
を少ない部品の組み合せで構成するため、同一の
羽根車を利用し、この羽根車の外径側を適量削り
落して異特性のポンプを得ることが行なわれてい
る。すなわち、羽根車の外径側を削り落し、これ
の径をD₁，D₂，D₃としだいに小さくしてゆくと、
全揚程および軸動力はほぼ比例的に変化するが、
ポンプの最高効率点は小吐出し量側に移つてしま
う。また、ポンプの最高効率点を過ぎても軸動力
が同様な割合で増加を続けるため、このような外
径側を削り落した羽根車を組み込んだ遠心ポンプ
ではポンプの負荷が増し、吐出し量がポンプの最
高効率点を過ぎると次のような問題が生じる。す
なわち、通常、遠心ポンプの使用点はポンプの最
高効率点付近に選び、これに合わせてポンプ駆動
用の電動機を選定しているため、ポンプの最高効
率点を過ぎても軸動力が増え続けると、電動機が
オーバーロードしてしまい、ポンプ設備をダウン
させることになる。また、電動機の容量に余裕を
持たせて、遠心ポンプの使用点以上の軸動力を供
給できるように選定することも考えられるが、こ
れではポンプ設備が割高になつてしまう。さらに、比較的使用水量範囲の広いポンプでは
吐出し量の変化に対して全揚程の変化が大きい、
すなわち、右下がりの傾きの大きな遠心ポンプが
好まれている。これは遠心ポンプの制御運転を行
うとき、吐出し量の変化を吐出し圧力の変化に対
応させて検出する方式を取ることが多いため、圧
力変化が大きいほど制御性が向上するからであ
る。しかし、従来の構造の羽根車では羽根の出口角
が大きいため、これを組み込んだ遠心ポンプで
は、この傾きを大きく取ることができず、制御性
の向上をはかれない問題があつた。そこで本発明の目的は、比較的低比速度の遠心
ポンプにおいて、損失が少なく、且つ低流量域で
の吐出圧力が高く、吐き出し量−全揚程特性曲線
が、右下がりの急勾配を持つ、改良した構造の羽
根車を提供することにある。［課題を解決するための手段］抵比速度の遠心ポンプで締切揚程が高く、しか
も、吐出し量−全揚程特性曲線が右下がりの急勾
配を持つ特性のポンプを得るためには、羽根車の
外径D₀は大きく、羽根出口角β₂は小さく、かつ、
出口幅Ａを小さくしてゆくことが必要であること
が、研究の結果から分かつた。そこで、本発明では、円板状に構成した後面シ
ユラウドと、この後面シユラウドと対面してお
り、中央に吸込口を有する前面シユラウドと、後
面シユラウドと前面シユラウドとの間に配置した
複数枚の羽根とを備えており、羽根の入口先端か
ら出口末端に向かうに従い、後面シユラウドと前
面シユラウド間の距離が次第に減少するように構
成してあり、吸込口から前面シユラウドの外縁に
向けて伸ばした羽根相互間に曲状流路が形成して
ある羽根車に於いて、羽根の枚数を特に７枚と定
める。また、相隣り合う羽根に内接する円を流路
内に描くとき、流路の入口より出口に向かうにし
たがい円の直径が、一旦大きくなつた後に小さく
なるように構成する。更に各羽根の負圧面側の出
口末端から羽根車の中心に向けて伸ばした各線上
に、前記全面シユラウドまで至る３枚の羽根の重
なりが存在するように、羽根の巻き角を大きく構
成し、且つ、隣接する羽根間の間隔は、前記各線
上で見た場合、羽根車の中心から外周面に向かう
に連れて次第に狭くなるように構成するものであ
る。［作用］以上のように、構成すると、隣接する両羽根間
に形成される流路が必然的に長くなる。その結果
流路の断面積も充分小さくなるから、流路内で増
速流が生じる。その結果、主流が増速流になつて
いるので流路内での逆流の発生が抑制される。そ
の結果損失の少ない羽根車を構成することができ
る。また、低流量域での吐出圧力も高くなる。ま
た、羽根枚数を特に７枚と定めた理由は次の通り
である。各羽根の巻き角を前記した条件を満足す
るように大きくし、羽根車の外形寸法を従来のも
のと同等の大きさにすると、羽根の出口角β₂は必
然的に従来品の半分程度、つまり10゜前後になる。
出口角β₂を10゜前後に統一して羽根枚数を５〜８
枚に変えて性能を調べたのが次表である。 INDUSTRIAL APPLICATION This invention relates to centrifugal pump impellers, and in particular provides an improved impeller for low specific speed pumps. [Prior Art] Fig. 1 shows a very general structure of a conventional pump impeller. That is, the blade 1 is disposed between a disk-shaped rear shroud 2 and a front shroud (not shown) having a suction port, and extends in a spiral shape from the inside of the impeller toward the outside. Further, a spiral curved flow path is formed between the blades 1. In general, the impeller of a low specific speed pump has a larger D ₀ than the outlet width A of the blades 1, and therefore, in the flow path 3, there is an inscribed circle inscribed between adjacent blades 1.
When b ₁ and b ₂ are drawn, the diameter of the inscribed circles b ₁ and b ₂ gradually increases from the inside to the outside of the impeller. In addition, the meridian cross section of the impeller has a shape that decreases from the inside to the outside of the impeller. Furthermore, when drawing a circle inscribed in adjacent blades in a flow path, the diameter of the circle increases once from the inlet to the outlet of the flow path, and then becomes smaller. It is shown in Publication No. 52-69004. [Problem to be solved by the invention] In the case shown in FIG. 1, the change in cross-sectional area of the flow path 3 surrounded by the blade 1, the rear shroud 2, and the front shroud is not appropriately selected. Therefore, separation of flowing water occurs on the surface of the blade 1 in a low flow rate region, making it impossible to improve the discharge performance. The case shown in Japanese Patent Application Laid-Open No. 52-69004 is improved over the one shown in Fig. 1, but the flow path formed between the two adjacent blades does not have sufficient length. Since the cross-sectional area of the flow path is not set to a sufficiently small value, separation of flowing water still occurs on the surface of the blade, and the discharge performance cannot be sufficiently improved. Also, the exit angle of the vanes is not selected to be small enough. The problem when the exit angle of the blade is not small enough will be further explained with reference to FIG. In Figure 2, the horizontal axis shows the discharge amount, and the vertical axis shows the total pump head, pump efficiency, and shaft power. Conventionally, in order to construct pumps with a variety of discharge characteristics using a combination of a small number of parts, the same impeller was used and an appropriate amount of the outer diameter of the impeller was shaved off to obtain a pump with different characteristics. It is. In other words, by cutting off the outer diameter side of the impeller and gradually reducing its diameter to D ₁ , D ₂ , and D ₃ , we get
Although the total lift and shaft power change almost proportionally,
The pump's highest efficiency point shifts to the small discharge amount side. In addition, since the shaft power continues to increase at the same rate even after the pump's maximum efficiency point has passed, in a centrifugal pump that incorporates an impeller with the outside diameter cut down, the load on the pump increases and the discharge volume decreases. When the maximum efficiency of the pump is exceeded, the following problems occur. In other words, the point of use of a centrifugal pump is usually selected near the pump's highest efficiency point, and the electric motor for driving the pump is selected accordingly, so if the shaft power continues to increase even after the pump's highest efficiency point, , the electric motor will overload and the pump equipment will go down. It is also possible to select a motor with a sufficient capacity so that it can supply shaft power greater than the point of use of the centrifugal pump, but this would make the pump equipment relatively expensive. Furthermore, for pumps that use a relatively wide range of water usage, the total head changes greatly with changes in discharge volume.
That is, centrifugal pumps with a large downward slope to the right are preferred. This is because when performing controlled operation of a centrifugal pump, a method is often used in which a change in discharge amount is detected in correspondence with a change in discharge pressure, and the larger the pressure change, the better the controllability is. However, since the exit angle of the blades of conventional impellers is large, centrifugal pumps incorporating this impeller have a problem in that the inclination cannot be made large, and controllability cannot be improved. Therefore, an object of the present invention is to provide an improved centrifugal pump with relatively low specific speed, which has low loss, high discharge pressure in the low flow rate range, and has a discharge volume-total head characteristic curve with a steep downward slope to the right. The purpose of this invention is to provide an impeller with an improved structure. [Means for solving the problem] In order to obtain a low specific speed centrifugal pump with a high cut-off head and a characteristic curve in which the discharge rate-total head characteristic curve slopes downward to the right, it is necessary to The outer diameter D ₀ of is large, the blade exit angle β ₂ is small, and
The results of the research revealed that it is necessary to reduce the exit width A. Therefore, in the present invention, a rear shroud configured in a disk shape, a front shroud that faces the rear shroud and has a suction port in the center, and a plurality of blades arranged between the rear shroud and the front shroud are provided. The blades are configured so that the distance between the rear shroud and the front shroud gradually decreases from the inlet tip to the outlet end, and the distance between the blades extending from the inlet toward the outer edge of the front shroud is In an impeller having a curved flow path formed therebetween, the number of blades is specifically set to seven. Further, when a circle inscribed in adjacent blades is drawn in the flow path, the diameter of the circle increases once and then decreases as it goes from the inlet to the outlet of the flow path. Furthermore, the winding angle of the blades is configured to be large so that there is an overlap of three blades extending to the entire shroud on each line extending from the outlet end on the suction side side of each blade toward the center of the impeller, Moreover, the spacing between adjacent blades is configured to gradually become narrower from the center of the impeller toward the outer circumferential surface when viewed along each of the lines. [Function] With the configuration as described above, the flow path formed between the two adjacent blades inevitably becomes longer. As a result, the cross-sectional area of the flow path becomes sufficiently small, so that an accelerated flow occurs within the flow path. As a result, the main flow becomes an accelerated flow, and the occurrence of backflow within the flow path is suppressed. As a result, an impeller with less loss can be constructed. Furthermore, the discharge pressure in the low flow rate region also increases. Moreover, the reason why the number of blades was specifically set to 7 is as follows. If the winding angle of each blade is increased to satisfy the above conditions and the external dimensions of the impeller are made to be the same size as the conventional one, the exit angle β ₂ of the blade will inevitably be about half that of the conventional product. In other words, it will be around 10 degrees.
The exit angle β ₂ is unified around 10° and the number of blades is 5 to 8.
The following table shows the results of examining the performance by changing the number of sheets.

【表】これから内部効率は５枚から７枚に近づくにつ
れて向上し、７枚が最も高くなり、８枚になると
今度は低下することが分かる。また揚程にしても
７枚が最高値を示している。これが本発明に於い
て羽根枚数を７枚と特定した理由である。且つ流路の幅も前記したように定めたので、本
発明によれば、羽根出口角β₂も小さくなり、かつ
出口幅Ａも十分小さくなる。従つて、低流量域で羽根の出口端から吐出され
た水が、隣の羽根の出口端から逆流することを防
止することができ、低流量域での吐出圧力が高く
なり、且つ損失が少なくなる。［実施例］以下本発明の一つの実施例を第３図、第４図、
及び第５図によつて説明する。第３図は羽根車を
これの回転中心Ｏを通る線に沿つて切断した断面
図、第４図は羽根車をこれの回転中心線ｌに対し
て垂直を成す面、すなわち第３図に示すＸ−Ｘ面
に沿つて切断した断面図、第５図は横軸に吐出し
量、縦軸に軸動力、ポンプ効率、全揚程の各値を
取つた線図である。図に示すのは鋳造製の羽根車４の例であり、５
は円板状に構成した前面シユラウドであり中央に
吸込口６が設けてある。７は円板状に構成した後
面シユラウドであり、中央に図示しない回転軸に
連結するためのボス８を備えている。もちろん、
このボス８には回転軸を嵌合するための貫通穴９
が設けてある。１０は前面シユラウド５と後面シ
ユラウド７との間に設けた羽根であり、羽根車４
の内側から外側に向けて渦巻状に伸ばしてある。
この羽根の枚数は、本発明により、特に７枚が選
択してある。また、この羽根１０の吸込口６側の
前縁、つまり入口先端１１は後面シユラウド７か
ら前面シユラウド５に向かうにしたがい、羽根車
４の中心（回転中心Ｏ）よりしだいに離れるよう
に渦巻状に設けてある。羽根１０相互の間には羽
根車４の内側、すなわち、吸込口６より外側に向
けて曲状流路が形成されている。また、前面シユ
ラウド５と後面シユラウド７間の距離ｇは羽根車
４の入口先端１１より出口末端に向かうにしたが
い、しだいに減少するように構成している。さらに、第４図により説明を続けると、各羽根
１０，１０の負圧面側の出口末端１３から羽根車
の中心Ｏに向けて伸ばした各線ｈ上には、出口末
端１３から羽根車の中心Ｏに至る間に前面シユラ
ウドまで至る３枚の羽根１０の重なりが形成して
ある。隣接する羽根間の間隔l₁，l₂，l₃は、各線
ｈ上で見た場合、羽根車の中心Ｏから外周面に向
かうに連れて次第に狭くなるように構成してあ
る。また、羽根車４は相隣り合う羽根１０，１０に
内接する円を流路内に描くとき、流路の入口より
出口に向かうにしたがい、円の直径E₁，E₂，E₃
が一旦大きくなつた後に小さくなるように流路の
幅ｆが形成してある。さて、羽根１０の負圧面側の出口末端１３より
羽根車４の回転中心Ｏに向けて伸ばした各線ｈ上
に、前面シユラウドまで至る、３枚の羽根の重な
りが存在するように各羽根の巻き角を大きく構成
し、且つ隣接する羽根間の間隔は、各線ｈ上で見
た場合、羽根車の内側から外側に向うに連れて次
第に小さくなるように構成したので、羽根の出口
角β₂を十分小さくすることができ、また羽根枚数
を７枚に定めたことと相俟つて、出口端での流路
ｆも十分狭くなる。したがつて流路１２内で剥離
や逆流が発生する可能性が少なくなり、締切り圧
力が上昇してゆく。この結果、吐出し量−全揚程
特性は第５図に示すように、急勾配な右下り特性
となり遠心ポンプの制御性が向上してゆく。また、この羽根車４を使用して異特性の遠心ポ
ンプを製作する場合、羽根車４の外径側を削り落
してゆくことが行なわれているが、実施例の羽根
車４の羽根１０では負荷分布が羽根１０の出口末
端１３側より入口末端１１側に片寄つているた
め、羽根車４の外径側を削り落しても、ポンプ効
率の最高効率点が小吐出し量側に移動してしまう
ことがなくなり、常に十分な水量を効率良く送水
してゆくことができるものである。さらに、吐出し量−全揚程特性の勾配が大きい
ことから、ポンプの最高効率点を過ぎると軸動力
の増加が鈍くなるため、ポンプの使用点に合わせ
て電動機の容量を選んだ場合、ポンプの負荷が使
用点を越えたとき急に電動機がオーバーロードし
てしまう危険が避けられ、ポンプ設備の安全性が
向上する。さて、本発明の羽根車では、従来の羽根車に比
べて出口幅Ａが小さく、さらに羽根１０の後縁１
３側の流路幅ｆが小さく流路１２が長いことか
ら、第６図に示す実施例では、羽根車４の最も外
側の流路１２を構成する羽根１０に、この羽根１
０の厚み方向に貫通し、隣接している流路間を連
通する連通孔１４を設けて、製作の容易化を図つ
ている。この連通孔１４は羽根車４の外周面から
羽根車４の中心Ｏに向つて見たときに、見える部
分に設ける。このような構成を取ると中子製作時に中子砂を
連通孔１４を通して出口１５側から流路１２内に
供給、あるいは、流路１２内の空気を連通孔１４
を通して流路１２外に排出することができるた
め、中子砂の回りが良くなり中子製作が容易とな
り、しかも、中子砂を高密度に詰め込むことによ
り製作した中子の強度が向上する。したがつて、
鋳込時に中子の受ける湯の浮力に対する強度が増
し、鋳物不良をなくすことができる。なお、羽根
１０の負荷分布を羽根の入口先端１１側に集中さ
せているため負荷の小さな出口末端１３の近くに
連通穴１４を設けても、ポンプ性能にはほとんど
影響しないものである。以上説明した実施例では主に羽根車を鋳物によ
り構成してゆく例を説明したが、本発明はこれに
限ることなく鋼板を必要な形状に加工し、この各
部材をかしめ作業あるいは溶接作業により組み立
てて構成することもできる。また、本発明の羽根車の羽根は前・後面シユラ
ウドに垂直に配置するばかりでなく、ある程度傾
斜させて設けても良い。［発明の効果］以上の説明から明らかなように、本発明では後
面シユラウドと前面シユラウドとを有する遠心ポ
ンプの羽根車に於いて、羽根枚数を特に７枚と多
くし、相隣り合う羽根に内接する円を流路内に描
くとき、前記流路の入口より出口に向かうにした
がい円の直径が、一旦大きくなつた後に小さくな
るように構成してあり、更に各羽根は、各羽根の
負圧面側の出口末端から羽根車の中心に向けて伸
ばした各線上に、前面シユラウドまで至る３枚の
前記羽根の重なりが存在するように各羽根の巻き
角を大きく構成してあり、且つ隣接する前記羽根
間の間隔は、前記線上で見た場合、羽根車の内側
から外側に向うに連れて次第に小さくなるように
構成した。従つて、本発明の羽根車は、損失が少なく低流
量域で羽根の出口端から吐出された水が、隣の羽
根の出口端から逆流することを防止することがで
き、低流量域での吐出圧力が高く、吐き出し量−
全揚程特性曲線が、右下がりの急勾配を持つ特性
を示す効果がある。[Table] From this it can be seen that the internal efficiency improves as the number of cards approaches from 5 to 7, is highest at 7, and then decreases when it reaches 8. In addition, 7 pieces showed the highest value in terms of lifting height. This is the reason why the number of blades is specified as seven in the present invention. In addition, since the width of the flow path is determined as described above, according to the present invention, the blade exit angle β ₂ is also small, and the exit width A is also sufficiently small. Therefore, water discharged from the outlet end of a blade in a low flow rate region can be prevented from flowing backward from the outlet end of an adjacent blade, increasing the discharge pressure in the low flow rate region and reducing loss. Become. [Example] An example of the present invention is shown in FIGS. 3 and 4 below.
This will be explained with reference to FIG. Fig. 3 is a sectional view of the impeller taken along a line passing through its rotation center O, and Fig. 4 shows the impeller in a plane perpendicular to its rotation center line l, that is, Fig. 3. FIG. 5, which is a sectional view taken along the X-X plane, is a graph in which the horizontal axis represents the discharge amount, and the vertical axis represents the values of shaft power, pump efficiency, and total head. The figure shows an example of a cast impeller 4.
1 is a front shroud constructed in the shape of a disk, with a suction port 6 provided in the center. Reference numeral 7 denotes a rear shroud having a disk shape, and is provided with a boss 8 at the center for connection to a rotating shaft (not shown). of course,
This boss 8 has a through hole 9 for fitting the rotating shaft.
is provided. 10 is a blade provided between the front shroud 5 and the rear shroud 7;
It extends in a spiral shape from the inside to the outside.
According to the invention, the number of blades is particularly selected to be seven. Further, the leading edge of the blade 10 on the side of the suction port 6, that is, the inlet tip 11, is formed in a spiral shape so as to gradually move away from the center of the impeller 4 (rotation center O) as it goes from the rear shroud 7 to the front shroud 5. It is provided. A curved flow path is formed between the blades 10 toward the inside of the impeller 4, that is, toward the outside from the suction port 6. Further, the distance g between the front shroud 5 and the rear shroud 7 is configured to gradually decrease from the inlet tip 11 of the impeller 4 toward the outlet end. Further, to continue the explanation with reference to FIG. Three blades 10 are overlapped to reach the front shroud. The intervals l ₁ , l ₂ , l ₃ between adjacent blades are configured to gradually become narrower from the center O of the impeller toward the outer peripheral surface when viewed on each line h. Further, when the impeller 4 draws a circle inscribed in the adjacent blades 10, 10 in the flow path, the diameters of the circle E ₁ , E ₂ , E ₃ from the inlet to the outlet of the flow path.
The width f of the flow path is formed such that the width f increases once and then decreases. Now, on each line h extending from the outlet end 13 on the suction surface side of the blade 10 toward the rotation center O of the impeller 4, wind each blade so that there is an overlap of three blades extending to the front shroud. The angle is large, and the spacing between adjacent blades is configured so that it gradually becomes smaller from the inside to the outside of the impeller when viewed on each line h, so the exit angle β ₂ of the blades is This can be made sufficiently small, and together with the fact that the number of blades is set to seven, the flow path f at the outlet end can also be made sufficiently narrow. Therefore, the possibility of occurrence of separation or backflow within the flow path 12 decreases, and the cut-off pressure increases. As a result, the discharge amount-total head characteristic becomes a steep downward slope to the right, as shown in FIG. 5, and the controllability of the centrifugal pump improves. In addition, when manufacturing a centrifugal pump with different characteristics using this impeller 4, the outer diameter side of the impeller 4 is ground down, but in the case of the impeller 10 of the impeller 4 of the embodiment. Since the load distribution is biased toward the inlet end 11 side from the outlet end 13 side of the impeller 10, even if the outer diameter side of the impeller 4 is shaved off, the highest efficiency point of the pump efficiency will shift to the small discharge amount side. This means that there is no need to store water, and a sufficient amount of water can always be efficiently delivered. Furthermore, since the gradient of the discharge rate vs. total head characteristic is large, the increase in shaft power slows down after the pump's maximum efficiency point. The danger of sudden overload of the motor when the load exceeds the point of use is avoided, improving the safety of the pump equipment. Now, in the impeller of the present invention, the outlet width A is smaller than that of the conventional impeller, and furthermore, the trailing edge 1 of the blade 10
Since the channel width f on the third side is small and the channel 12 is long, in the embodiment shown in FIG.
A communication hole 14 is provided which penetrates in the thickness direction of 0 and communicates between adjacent channels, thereby facilitating manufacturing. The communication hole 14 is provided in a visible portion when viewed from the outer peripheral surface of the impeller 4 toward the center O of the impeller 4. If such a configuration is adopted, core sand is supplied into the flow path 12 from the outlet 15 side through the communication hole 14 during core manufacturing, or air in the flow path 12 is fed into the flow path 12 through the communication hole 14.
Since the core sand can be discharged to the outside of the flow path 12 through the core sand, the core sand can circulate easily and the core can be manufactured easily, and the strength of the manufactured core can be improved by densely packing the core sand. Therefore,
The strength against the buoyancy of the hot water that the core receives during casting increases, and casting defects can be eliminated. In addition, since the load distribution of the vane 10 is concentrated on the inlet tip 11 side of the vane, even if the communication hole 14 is provided near the outlet end 13 where the load is small, it will hardly affect the pump performance. In the embodiments described above, the impeller is mainly constructed of cast metal, but the present invention is not limited to this, and the present invention is not limited to this, but the present invention is not limited to this, and each member is formed by caulking or welding. It can also be assembled and configured. Further, the blades of the impeller of the present invention may not only be arranged perpendicularly to the front and rear shrouds, but may also be arranged at a certain degree of inclination. [Effects of the Invention] As is clear from the above description, in the present invention, in the impeller of a centrifugal pump having a rear shroud and a front shroud, the number of blades is particularly increased to 7, and the number of blades is increased to 7, and the number of blades is When drawing tangent circles in the flow channel, the diameter of the circle increases once from the inlet to the outlet of the flow channel, and then becomes smaller. The winding angle of each blade is configured to be large so that there is an overlap of the three blades up to the front shroud on each line extending from the side outlet end toward the center of the impeller, and The spacing between the blades was configured to gradually become smaller from the inside to the outside of the impeller when viewed along the line. Therefore, the impeller of the present invention has low loss and can prevent water discharged from the outlet end of the blade in the low flow range from flowing back from the outlet end of the adjacent blade, and can prevent water discharged from the outlet end of the blade in the low flow range. High discharge pressure and discharge amount -
This has the effect that the total head characteristic curve exhibits a characteristic with a steep slope downward to the right.

[Brief explanation of drawings]

第１図は従来の羽根車の構造を説明するための
断面図、第２図は従来の羽根車を組み込んだ遠心
ポンプの諸特性を説明するため横軸に吐出し量、
縦軸に全揚程・ポンプ効率・軸動力を取つた図、
第３図は本発明の一つの実施例の羽根車の回転中
心Ｏに沿つて切断した断面図、第４図は第３図に
示す羽根車を回転中心線ｌにほぼ垂直なＸ−Ｘ面
で切断した断面図、第５図は第３図・第４図に示
す羽根車を組み込んだ遠心ポンプの諸特性を説明
するため横軸に吐出し量、縦軸に全揚程・ポンプ
効率・軸動力を取つた図、第６図は第３図・第４
図に示す実施例をさらに改良した実施例を説明す
るための断面図である。４……羽根車、１０……羽根、１１……羽根の
入口先端、１２……流路、１３……羽根の出口末
端、１４……連通孔、１５……流路の出口、１６
……流路の入口、Ａ……出口幅、l₁，l₂，l₃……
隣接する羽根間の間隔、ｌ１，ｌ２，ｌ３……羽
根の間隔、E₁，E₂，E₃……円の径、ｆ……流路
幅、ｈ……線。 Fig. 1 is a cross-sectional view to explain the structure of a conventional impeller, and Fig. 2 is a cross-sectional view to explain various characteristics of a centrifugal pump incorporating a conventional impeller.
Diagram showing total head, pump efficiency, and shaft power on the vertical axis,
FIG. 3 is a sectional view taken along the rotation center O of an impeller according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view of the impeller shown in FIG. Figure 5 is a sectional view taken at Figure 6 shows the power taken from Figure 3 and Figure 4.
FIG. 3 is a cross-sectional view for explaining an embodiment that is a further improvement of the embodiment shown in the figure. 4... Impeller, 10... Vane, 11... Inlet tip of the vane, 12... Channel, 13... Outlet end of the vane, 14... Communication hole, 15... Outlet of the channel, 16
...Inlet of flow path, A...Outlet width, l ₁ , l ₂ , l ₃ ...
Spacing between adjacent blades, l1, l2, l3... Spacing between blades, E ₁ , E ₂ , E ₃ ... Diameter of circle, f... Channel width, h... Line.

Claims

[Claims]

1. A rear shroud configured in the shape of a disk, a front shroud facing the rear shroud and having a suction port in the center, and a plurality of blades arranged between the rear shroud and the front shroud. The blade is configured such that the distance between the rear shroud and the front shroud gradually decreases from the inlet tip to the outlet end, and extends from the suction port toward the outer green of the front shroud. In the impeller in which a curved flow path is formed between the blades, the number of blades is seven, and when a circle inscribed in the adjacent blades is drawn in the flow path, The diameter of the circle increases from the inlet to the outlet of the flow path, and then decreases. The winding angle of each of the blades is configured to be large so that the three blades extending up to the front shroud overlap each other on each line stretched out, and the spacing between adjacent blades is An impeller for a centrifugal pump characterized in that the impeller is configured to gradually become narrower from the center of the impeller toward the outer circumferential surface.