简介：Whenthehigh-pressuregasisexhaustedtothevacuumchamberfromthenozzle,theunderexpandedsupersonicjetcontainedwiththeMachdiskisgenerallyformed.Theeventualpurposeofthisstudyistoclarifytheunsteadyphenomenonoftheunderexpandedfreejetwhenthebackpressurecontinuouslychangeswithtime.ThecharacteristicoftheMachdiskhasbeenclarifiedinconsiderationofthediameterandpositionofitbythenumericalanalysisinthispaper.ThesonicjetoftheexitMachnumberMe=1isassumedandtheaxisymmetricconservationalequationissolvedbytheTVDmethodinthenumericalcalculation.ThediameterandpositionoftheMachdiskdifferswiththeresultsofasteadyjetandtheinfluenceonthecontinuouslychangingofthebackpressureisevidencedfromthecomparisonwiththecaseofsteadysupersonicjet.

简介：光线的汽轮机阶段经常例如为要求离开设计操作的应用被使用，作为turbocharging。如此的阶段的离开设计能力通常通过传统的汽轮机地图被分析，阴谋减少对压力比率集体流动，为还原剂速度线。然而，一些选择是可能的，例如流动系数()到负担系数()压力比率排队的图实际上是直线，执行的很方便的性质预言。柔韧的方法re-creating这张地图从一预言-图被需要。最近的工作证明了没有任何损失模型的使用，这背推理质量取决于中间的压力比率的知识。这个参数的modelization然后被建议。比较与试验性并且CFD结果被介绍与为集体流动率和旋转速度的相当好的同意，并且为中间的压力比率。纸的最后部分被奉献给到压力比率的推理的改进的知识排队在的中间的压力比率的申请-图。在这改进旁边，古典地图的背推理方法被组织，使用并且评估。

简介：Weproposeapositionsensorlesscontrolschemeforafour-switch,three-phasebrushlessDCmotordrive,basedonthezerocrossingpointdetectionofphaseback-EMFvoltagesusingnewlydefinederrorfunctions(EFs).Thecommutationin-stantsare30°afterdetectedzerocrossingpointsoftheEFs.DevelopedEFshavegreatermagnituderatherthanphaseorlinevoltagessothatthesensorlesscontrolcanworkatalowerspeedrange.Moreover,EFshavesmoothtransitionsaroundzerovoltagelevelthatreducesthecommutationerrors.EFsarederivedfromthefilteredterminalvoltagesvaoandvbooftwolow-passfilters,whichareusedtoeliminatehighfrequencynoisesforcalculationoftheaverageterminalvoltages.Thefeasibilityoftheproposedsensorlesscontrolisdemonstratedbysimulationandexperimentalresults.