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　　What is the throttling device of orifice flowmeter and how should we define it?Xi'an Huaheng Instrument Manufacturing Co.,Ltd.

 

　　孔板流量計是將標準孔板與多參數差壓變送器(或差壓變送器、溫度變送器及壓力變送器)配套組成的高量程比差壓流量裝置，可測量氣體、蒸汽、液體及引的流量，廣泛應用于石油、化工、冶金、電力、供熱、供水等領(lǐng)域的過(guò)程控制和測量

 

　　Orifice plate flowmeter is a high range ratio differential pressure flowmeter which is composed of standard orifice plate and multi-parameter differential pressure transmitter(or differential pressure transmitter,temperature transmitter and pressure transmitter).It can measure the flow of gas,steam,liquid and drainage.It is widely used in process control and measurement in petroleum,chemical industry,metallurgy,electric power,heating,water supply and other fields.

 

　　管道的前后壓差較大時(shí)，往往采用增加節流孔板的方式，其原理是:流體在管道中流動(dòng)時(shí)，由于孔板的局部阻力，使得流體的壓力降低，能量損耗，該現象在熱力學(xué)上稱(chēng)為節流現象。該方式比采用調節閥要簡(jiǎn)單，但必須選擇得當，否則，液體容易產(chǎn)生汽蝕現象，影響管道的安全運行。

 

　　When the pressure difference between the front and back of the pipeline is large,the throttle orifice plate is often added.The principle is that when the fluid flows in the pipeline,the local resistance of the orifice plate reduces the pressure and energy loss of the fluid.This phenomenon is called throttle phenomenon in thermodynamics.This method is simpler than using control valve,but it must be selected properly.Otherwise,the liquid is prone to cavitation,which affects the safe operation of the pipeline.

 

　　節流孔板的作用，就是在管道的適當地方將孔徑變小，當液體經(jīng)過(guò)縮口，流束會(huì )變細或收縮。流束的最小橫斷面出現在實(shí)際縮口的下游，稱(chēng)為縮流斷面。在縮流斷面處，流速是最大的，流速的增加伴隨著(zhù)縮流斷面處壓力的大大降低。

 

　　The function of throttle orifice plate is to reduce the diameter of the orifice in the proper place of the pipeline.When the liquid passes through the shrinkage orifice,the flow beam will become smaller or shrink.The minimum cross-section of the beam appears downstream of the actual contraction,which is called the contraction cross-section.At the condensation section,the velocity is the largest,and the pressure at the condensation section decreases greatly with the increase of the velocity.

 

　　當流束擴展進(jìn)入更大的區域，速度下降，壓力增加，但下游壓力不會(huì )完全恢復到上游的壓力，這是由于較大內部紊流和能量消耗的結果。

 

　　When the beam expands into a larger region,the velocity decreases and the pressure increases,but the downstream pressure will not completely restore to the upstream pressure,which is due to larger internal turbulence and energy consumption.