英语翻译Because the vortex rope appearing in the drafttube is a

英语翻译
Because the vortex rope appearing in the draft
tube is a common phenomenon for most Francis
turbines in the part load zone,and the rotating
frequency of the rope is about 1/4 to 1/3 multiple of
runner rotation frequency
,it may be concluded
that the low-frequency component of vibration,
oscillation and pressure fluctuation existing in the
investigated turbine is induced by draft tube vortex
rope.Generally,it could not be avoided completely in
this part load zone.Some technical means should be
applied to control the unsteady features.This content
will be included in another article in the future.
In addition to the above low frequency,another
characteristic frequency,1.25 Hz (or 1.0f),was found
in the frequency spectrum of vibration and pressure
fluctuation,as shown in Figs.3 and 7.It is very
possible to correlate this frequency and the runner
passing frequency.
Considering the 5.7 Hz (or 4.56f) characteristic
frequency existeing at load 540 MW-542 MW,it is
not found in the numerical simulation results.It is
should be noticed that this special frequency exists
only at the head 68.3 m according to the experimental
investigation.The 4.56 multiple frequency exists
neither in draft tube pressure fluctuation nor in head
cover vibration when the head exceeds 68.3 m.It may
be concluded that the head cover vibration is mainly
resulted from high-frequency pressure fluctuation of
the draft tube.This vibration area may be classified as
a special vibration area,and the corresponding
frequency is recognized as a special vibration
frequency.
It should be mentioned that this special vibration
area appears in the designed normal running range.
Therefore,this vibration area should be avoided by
carefully allocating load.

Because the vortex rope appearing in the draft tube is a common phenomenon for most Francis turbines in the part load zone,and the rotating frequency of the rope is about 1/4 to 1/3 multiple of runner rotation frequency,it may be concluded that the low-frequency component of vibration,oscillation and pressure fluctuation existing in the investigated turbine is induced by draft tube vortex rope.Generally,it could not be avoided completely in this part load zone.Some technical means should be applied to control the unsteady features.This content will be included in another article in the future.
在部分载荷区,由于在吸出管出现涡带（涡流绳）对大部分弗兰西斯水轮机而言是一种常见的现象,且绳的旋转频率约为转轮旋转频率的1/4至1/3倍,可以认定,存在于所研究的水轮机上的振动,摆动和压力波动的低频成分是由尾水管的涡带引起的.一般来说,在这种部分负荷区是不可能完全避免的.应采取一些技术手段来控制其不稳定特征.该部分内容将放在将来的另一篇文章中（论述）.
In addition to the above low frequency,another characteristic frequency,1.25 Hz (or 1.0f),was found in the frequency spectrum of vibration and pressure fluctuation,as shown in Figs.3 and 7.It is very possible to correlate this frequency and the runner passing frequency.
除上述低频外,在振动和压力波动的频谱中发现另一个特征频率,1.25赫兹（或1.0f）,如图3和图7所示.该频率这很可能与转轮通过频率相关.
Considering the 5.7 Hz (or 4.56f) characteristic frequency existing at 540 MW-542 MW load,it is not found in the numerical simulation results.It is should be noticed that this special frequency exists only at the head 68.3 m according to the experimental investigation.The 4.56 multiple frequency exists neither in draft tube pressure fluctuation nor in head cover vibration when the head exceeds 68.3 m.It may be concluded that the head cover vibration is mainly resulted from high-frequency pressure fluctuation of the draft tube.This vibration area may be classified as a special vibration area,and the corresponding frequency is recognized as a special vibration frequency.
至于存在于540 MW-542 MW负荷的5.7赫兹（或4.56f）特征频率,数值模拟结果中没有发现.应该注意的是,根据实验研究,这个特殊频率只存在于水头68.3米之时.当水头超过68.3米时,尾水管压力波动和盖罩振动均不会出现这种4.56多频.可以认定,盖罩的振动主要是由尾水管的高频压力波动引起的.这一振动区可归为特殊振动区,相应的频率被视为特殊振动频率.
It should be mentioned that this special vibration area appears in the designed normal running range.Therefore,this vibration area should be avoided by carefully allocating load.
应该提及的是,该特殊振动区出现在设计的正常运行范围内.因此,该振动区应通过仔细分配负荷而加以避免.
再问： ˮͷ��
再答： 对，head=水头，专业术语，=water head