Theoretical and numerical study was carried out based on a linear turbine cascade(the Basic cascade)to compare the influences of the increased cascade pitch and turning angle in this paper.On one hand,the two highly-l...Theoretical and numerical study was carried out based on a linear turbine cascade(the Basic cascade)to compare the influences of the increased cascade pitch and turning angle in this paper.On one hand,the two highly-loaded designs both reduced the stability of flow field through enhancing adverse pressure gradient and span-wise pressure gradient of the fluid near suction surface.Therefore,the two highly-loaded designs would both result in thicker boundary layer and stronger secondary flow,so the secondary loss would be increased and more difficult to suppress in the highly-loaded cascades.On the other hand,the two highly-loaded designs showed different influences on the pitch-wise migration of the fluid near the endwall(cross flow)because of the different load enhancing mechanisms.In other words,the increased cascade pitch(TCx highly-loaded design)would delay the pitch-wise migration of the horseshoe vortex because of the increased channel width,while the increased turning angle(Turn highly-loaded design)would do the opposite because of the increased pitch-wise pressure gradient.As a result,the enhancement of the interaction between the fluid near the suction surface and the cross flow would be much stronger in the Turn highly-loaded design than the TCx highly-loaded design,and the span-wise developing tendencies of vortexes and fluid near the suction surface would show much stronger enhancing tendency in the former than the latter.展开更多
文摘Theoretical and numerical study was carried out based on a linear turbine cascade(the Basic cascade)to compare the influences of the increased cascade pitch and turning angle in this paper.On one hand,the two highly-loaded designs both reduced the stability of flow field through enhancing adverse pressure gradient and span-wise pressure gradient of the fluid near suction surface.Therefore,the two highly-loaded designs would both result in thicker boundary layer and stronger secondary flow,so the secondary loss would be increased and more difficult to suppress in the highly-loaded cascades.On the other hand,the two highly-loaded designs showed different influences on the pitch-wise migration of the fluid near the endwall(cross flow)because of the different load enhancing mechanisms.In other words,the increased cascade pitch(TCx highly-loaded design)would delay the pitch-wise migration of the horseshoe vortex because of the increased channel width,while the increased turning angle(Turn highly-loaded design)would do the opposite because of the increased pitch-wise pressure gradient.As a result,the enhancement of the interaction between the fluid near the suction surface and the cross flow would be much stronger in the Turn highly-loaded design than the TCx highly-loaded design,and the span-wise developing tendencies of vortexes and fluid near the suction surface would show much stronger enhancing tendency in the former than the latter.
