In　this　study,　a　method　that　taking　use　of　local　low-pressure　auxiliary　entrainment　for　improving　the　performance　of　steam　ejectors　is　proposed,　and　the　internal　flow　fields　in　the　steam　ejector　with　and　without　auxiliary　entrainment　were　numerically　investigated　using　commercial　software　FLUENT.　Analysis　and　research　are　mainly　focused　on　the　influences　of　different　auxiliary　entrainment　way　on　the　mass　flow　rate　of　primary　steam,　entrained　steam　and　auxiliary　entrained　steam,　the　entrainment　ratio,　the　internal　pressure　field　and　the　shock　wave　phenomena　under　the　back　pressure　fluctuation　condition　of　double-critical　range.　It　is　found　that　the　mixing　chamber　auxiliary　entrainment　is　not　effective　for　improving　the　performance　of　steam　ejector,　but　the　throat　and　diffuser　auxiliary　entrainment　can　increase　the　entrainment　ratio　of　the　steam　ejector　under　the　simulated　operation　conditions.　And　there　is　an　optimal　auxiliary　entrainment　scheme　under　different　back　pressure.　©　2017,　Science　Press.　All　right　reserved.