水輪機的有效水頭(外文翻譯)

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中文： 5200字
英文： 14000字符



毛水頭就是壩前水位與尾水管水位的差值。
有效水頭就是毛水頭減去蝸殼前多產(chǎn)生的所有損失。如果尾水管的水位只能不準確的測量或者根本不能被測量，那么這部分發(fā)生在出口斷面與被測點之間的損失應(yīng)該加進那部分被扣除的損失內(nèi)。
雖然水輪機能利用的水頭既能量水頭不能被準確的定義為靜水頭或者凈水頭或有效水頭，我們還是要確定能量水頭因為要校驗轉(zhuǎn)輪保證效率。有效水頭被定義為兩個能量水頭之差，既蝸殼進口斷面的能量水頭與尾水管出水口斷面的能量水頭之差，用表1的符號我們可以寫出凈水頭的表達式......



EFFECTIVE HEAD OF WATER TURBINE

1. The gross head is the difference between headwater elevation immediately before the station and tail-water elevation immediately after the exit from the draft tube.

Fig.1 Net or effective head

2. The static head can be derived from the gross head by subtracting all the losses occurring in the passage before the scroll case. If the elevation of water immediately below the draft tube can be gauged only inaccurately, or not at all, the losses between the exit section and the site of actual gauging shall be added to the amount of losses to be subtracted.
3. Since the energy head actually available for the turbine cannot precisely be defined by the static head either, the net head, or effective head, shall also be determined in order to check the guaranteed wheel efficiency. The effective head is defined as the difference between two energy heads, viz., between the energy head at the entrance to the scroll case and the one at the exit of the draft tube. Using notations of Fig.1 we can write for the net head ......