轮机英语（二三管轮）Lesson 30 Typical Examples of Automatic Control.pptx

MarineEngineeringEnglish《轮机英语》APracticalCourseforEngineersWorkingonBoardShips

MarineElectricalSystemandAutomatizationLesson30TypicalExamplesofAutomaticControlSystem第30课典型的自动控制系统

LearningObjectives:1.Graspsomeusefulwordsandexpressionsinthewholetext.2.Afterstudyingthelesson,heorshewillhaveabetterunderstandingofAutomaticControlSystem.3

4part1NewWordsandExpressions

5part2TextAnalysis

L30ExamplesofAutomaticControlBoilerwaterlevelcontrol锅炉水位控制

L30ExamplesofAutomaticControlAmodernhighpressure,hightemperaturewaterbuckboilerholdsasmallquantityofwaterandproduceslargequantitiesofsteam.#现代高压高温的水管锅炉装少量的水却产生大量的蒸汽。

L30ExamplesofAutomaticControlVerycarefulcontrolofthedrumwaterlevelisthereforenecessary.#因此有必要对锅筒水位仔细控制。

L30ExamplesofAutomaticControlThereactionsofsteamandwaterinthedrumarecomplicatedandrequireacontrolsystembasedonanumberofmeasuredelements.#锅炉中水与蒸汽的作用是复杂的，因此需要有多个测量元件的控制系统。

L30ExamplesofAutomaticControlWhenaboilerisoperatingthewaterlevelinthegaugeglassreadshigherthanwhentheboilerisshutdown.#当锅炉运行时，玻璃水位计的显示水位比停炉时高。

L30ExamplesofAutomaticControlThisisbecauseofthepresenceofsteambubblesinthewater,asituationwhichisacceptedinnormalpractice.#这是因为水中有气泡，这在实际运行中是允许的。

L30ExamplesofAutomaticControlIfhoweverthereoccursasuddenincreaseinsteamdemandfromtheboilerthepressureinthedrumwillfall.Someofthewaterpresentinthedrumatthehigherpressurewillnow“flashoff”andbecomesteam.Thesebubblesofsteamwillcausethedrumleveltorise.#然而，如果锅炉的用汽量突然增加，锅筒压力下降。处在高压下的炉水就会“闪发”成汽，并造成水位高涨。

L30ExamplesofAutomaticControlThereducedmassofwaterinthedrumwillalsoresultinmoresteambeingproduced,whichwillfurtherraisethewaterlevel.#锅筒中炉水量的减少促使产生更多的蒸汽，这将使水位进一步升高。

L30ExamplesofAutomaticControlThiseffectisknownas“swell”.#这种效应就是所谓的“泡涨”。

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