In this paper,the aero-thermal performance of squealer tips with deep-scale depth is numerically investigated in an axial flow turbine,which is compared with the squealer tip with traditional cavity depth.Numerical me...In this paper,the aero-thermal performance of squealer tips with deep-scale depth is numerically investigated in an axial flow turbine,which is compared with the squealer tip with traditional cavity depth.Numerical methods were validated with experimental data.The effect of cavity depth and tip clearance was considered.The numerical results show that for the squealer tip with conventional cavity depth,the size of the reflux vortex enlarges as the cavity depth increases.The velocity and uniformity of high entropy production rate(EPR)inside the cavity reduce obviously with the cavity developing into deep-scale.However,the increase of depth 10%of the blade span(H)leads to enlargement of cavity volume,which increases the total entropy production rate.And the overall dimensionless entropy production rate(DEPR)of gap and cavity obtains a maximum increase of 43.54%in contrast to the case with 1%H depth cavity.As a result,the relative leakage mass flow rate reduces by 20.6%as the cavity depth increases from 1%to 10%.Given the heat transfer,as the cavity significantly increases to 10%H,the enhanced cavity volume results in a more enormous cavity vortex with low velocity covering the floor,which weakens the convective heat transfer intensity and reduces the area of high heat transfer.The normalized average heat transfer coefficient at the cavity bottom reduces by 40.26%compared to the cavity depth of 1%H.In addition,the deep-scale cavity is more effective in inhibiting leakage flow at smaller tip clearance.The reduction amplitude of normalized average heat transfer coefficient at the squealer floor decreases as tip clearance increases,which reduces at most by about 72.6%for the tip clearance of 1%H.展开更多
The steady and unsteady leakage flow and heat transfer characteristics of the rotor blade squealer tip were conducted by solving Reynolds-Averaged Navier-Stokes(RANS) equations with k-ω turbulence model.The first sta...The steady and unsteady leakage flow and heat transfer characteristics of the rotor blade squealer tip were conducted by solving Reynolds-Averaged Navier-Stokes(RANS) equations with k-ω turbulence model.The first stage of GE-E3 engine with squealer tip in the rotor was adopted to perform this work.The tip clearance was set to be 1% of the rotor blade height and the groove depth was specified as 2% of the span.The results showed that there were two vortexes in the tip gap which determined the local heat transfer characteristics.In the steady flow field,the high heat transfer coefficient existed at several positions.In the unsteady case,the flow field in the squealer tip was mainly influenced by the upstream wake and the interaction of the blades potential fields.These unsteady effects induced the periodic variation of the leakage flow and the vortexes,which resulted in the fluctuation of the heat transfer coefficient.The largest fluctuation of the heat transfer coefficient on the surface of the groove bottom exceeded 16% of the averaged value on the surface of the squealer tip.展开更多
This paper presents the investigation of the effects of suction side squealer tip on the performance of an axial compressor.The experiment is carried out in a single-stage large-scale low-speed compressor.The investig...This paper presents the investigation of the effects of suction side squealer tip on the performance of an axial compressor.The experiment is carried out in a single-stage large-scale low-speed compressor.The investigated tip geometries include flat tip as the baseline and suction side squealer tip.The tip clearance of the baseline is 0.5% of the blade span.The static pressure rise characteristic curves of both the rotor and the stage are measured.The flow field at the exit of the rotor is measured by a 5-hole probe under design and off-design conditions.The static pressure on the endwall of the rotor passage is also obtained.The results show that the pressure rise characteristic curves obtained by measuring the pressure on the end wall are almost unchanged by using the suction side squealer tip.The measuring results of the 5-hole probe show the static pressure and the total pressure in tip region is slightly greater than that of the flat tip at the design condition at the exit of the rotor.It also leads to greater av-eraged static pressure rise and total pressure.At the near stall condition,the averaged static pressure and total pressure is lower than the baseline which is related to the redistribution of the blade load caused by the suction side squealer tip.展开更多
It is well known that the non-uniform tip geometry is a promising passive flow control technique in turbomachinery.However,detailed investigation of its effects on the unsteady flow field of turbomachinery is rare in ...It is well known that the non-uniform tip geometry is a promising passive flow control technique in turbomachinery.However,detailed investigation of its effects on the unsteady flow field of turbomachinery is rare in the existiug hteratures.This paper presents an experimental investigation of effects of suction side squealer tip configuration on both the steady and unsteady flow field of an isolated compressor rotor.The flow field at 10%chord downstream from the trailing edge was measured using a mini five-hole probe.Meanwhile,the unsteady flow field inside the passage was investigated using stereo particle image velocimetry(SPIV).The steady results show that the SSQ tip configuration exerts positive effect on the static pressure rise performance of this compressor,and the radial equilibrium at the rotor outlet is obviously rearranged.The SSQ tip configuration would create a stronger tip leakage vortex at the formation phase,and it experiences a faster dissipation process around the rear chord.Also,the splitting process of the tip leakage vortex is severer,which is the main cause of the relatively higher probability of the presence of the streamwise reverse flow.The quantitatively analysis of the tip leakage vortex indicates that the velocity loss inside the blockage region is direct response of the evolutionary procedure of the tip leakage vortex.It keeps increasing until the end of the splitting process.Although the blockage coefficient grows sustainably,the velocity loss will reduce once the turbulent mixing procedure is dominant.展开更多
A novel perforated-rib configuration is proposed for controlling the tip leakage flow at the rotor tip of an axial turbine.Three perforated-rib layouts are considered,wherein a perforated rib is installed at(A)the Suc...A novel perforated-rib configuration is proposed for controlling the tip leakage flow at the rotor tip of an axial turbine.Three perforated-rib layouts are considered,wherein a perforated rib is installed at(A)the Suction-Side squealer(SS-rib),(B)the Pressure-Side squealer(PS-rib),and(C)the additional squealer along the blade Camber Line(CL-rib).A numerical method is used to show how the novel rib layouts affect the aerodynamic performance of the tip leakage flow.Results show that the coolant jets issuing from the perforated-rib injection holes penetrate deeper into the tip clearance than those in the baseline squealer-tip case,and how the perforated-rib coolant injection affects the tip leakage flow depends strongly on the rib layout.The PS-rib and CL-rib layouts appear promising for controlling the tip leakage flow,playing a significant role in reducing the total pressure loss and improving the turbine blade’s isentropic efficiency.In particular,under an injection mass flow ratio of 1%and a tip clearance of 1%blade span,the PS-rib layout reduces the leakage mass flow rate by 27%and increases the isentropic efficiency by 1.25%compared with those in the baseline squealer-tip case.Meanwhile,the advantages of the PS-rib layout in tip leakage control are confirmed under small and large tip clearances.展开更多
基金the financial supports for the project from the National Science and Technology Major Project of China(2017-Ⅲ-0010-0036)China Postdoctoral Science Foundation(NO.2020TQ0147)Natural Science Foundation of Jiangsu Province(NO.BK20200454)。
文摘In this paper,the aero-thermal performance of squealer tips with deep-scale depth is numerically investigated in an axial flow turbine,which is compared with the squealer tip with traditional cavity depth.Numerical methods were validated with experimental data.The effect of cavity depth and tip clearance was considered.The numerical results show that for the squealer tip with conventional cavity depth,the size of the reflux vortex enlarges as the cavity depth increases.The velocity and uniformity of high entropy production rate(EPR)inside the cavity reduce obviously with the cavity developing into deep-scale.However,the increase of depth 10%of the blade span(H)leads to enlargement of cavity volume,which increases the total entropy production rate.And the overall dimensionless entropy production rate(DEPR)of gap and cavity obtains a maximum increase of 43.54%in contrast to the case with 1%H depth cavity.As a result,the relative leakage mass flow rate reduces by 20.6%as the cavity depth increases from 1%to 10%.Given the heat transfer,as the cavity significantly increases to 10%H,the enhanced cavity volume results in a more enormous cavity vortex with low velocity covering the floor,which weakens the convective heat transfer intensity and reduces the area of high heat transfer.The normalized average heat transfer coefficient at the cavity bottom reduces by 40.26%compared to the cavity depth of 1%H.In addition,the deep-scale cavity is more effective in inhibiting leakage flow at smaller tip clearance.The reduction amplitude of normalized average heat transfer coefficient at the squealer floor decreases as tip clearance increases,which reduces at most by about 72.6%for the tip clearance of 1%H.
基金supported by China National Basic Research Program (973 Program),Project No.2007 CB 210107
文摘The steady and unsteady leakage flow and heat transfer characteristics of the rotor blade squealer tip were conducted by solving Reynolds-Averaged Navier-Stokes(RANS) equations with k-ω turbulence model.The first stage of GE-E3 engine with squealer tip in the rotor was adopted to perform this work.The tip clearance was set to be 1% of the rotor blade height and the groove depth was specified as 2% of the span.The results showed that there were two vortexes in the tip gap which determined the local heat transfer characteristics.In the steady flow field,the high heat transfer coefficient existed at several positions.In the unsteady case,the flow field in the squealer tip was mainly influenced by the upstream wake and the interaction of the blades potential fields.These unsteady effects induced the periodic variation of the leakage flow and the vortexes,which resulted in the fluctuation of the heat transfer coefficient.The largest fluctuation of the heat transfer coefficient on the surface of the groove bottom exceeded 16% of the averaged value on the surface of the squealer tip.
基金funded by the National Natural Science Foundation of China,Grant No.51161130525 and 51136003supported by the 111 Project,No.B07009
文摘This paper presents the investigation of the effects of suction side squealer tip on the performance of an axial compressor.The experiment is carried out in a single-stage large-scale low-speed compressor.The investigated tip geometries include flat tip as the baseline and suction side squealer tip.The tip clearance of the baseline is 0.5% of the blade span.The static pressure rise characteristic curves of both the rotor and the stage are measured.The flow field at the exit of the rotor is measured by a 5-hole probe under design and off-design conditions.The static pressure on the endwall of the rotor passage is also obtained.The results show that the pressure rise characteristic curves obtained by measuring the pressure on the end wall are almost unchanged by using the suction side squealer tip.The measuring results of the 5-hole probe show the static pressure and the total pressure in tip region is slightly greater than that of the flat tip at the design condition at the exit of the rotor.It also leads to greater av-eraged static pressure rise and total pressure.At the near stall condition,the averaged static pressure and total pressure is lower than the baseline which is related to the redistribution of the blade load caused by the suction side squealer tip.
基金co-supported by the National Natural Science Foundation of China(Grant No.51161130525/No.51136003)the 111Project(No.B07009)
文摘It is well known that the non-uniform tip geometry is a promising passive flow control technique in turbomachinery.However,detailed investigation of its effects on the unsteady flow field of turbomachinery is rare in the existiug hteratures.This paper presents an experimental investigation of effects of suction side squealer tip configuration on both the steady and unsteady flow field of an isolated compressor rotor.The flow field at 10%chord downstream from the trailing edge was measured using a mini five-hole probe.Meanwhile,the unsteady flow field inside the passage was investigated using stereo particle image velocimetry(SPIV).The steady results show that the SSQ tip configuration exerts positive effect on the static pressure rise performance of this compressor,and the radial equilibrium at the rotor outlet is obviously rearranged.The SSQ tip configuration would create a stronger tip leakage vortex at the formation phase,and it experiences a faster dissipation process around the rear chord.Also,the splitting process of the tip leakage vortex is severer,which is the main cause of the relatively higher probability of the presence of the streamwise reverse flow.The quantitatively analysis of the tip leakage vortex indicates that the velocity loss inside the blockage region is direct response of the evolutionary procedure of the tip leakage vortex.It keeps increasing until the end of the splitting process.Although the blockage coefficient grows sustainably,the velocity loss will reduce once the turbulent mixing procedure is dominant.
基金supported by the National Science and Technology Major Project,China(No.2017-III-0001-0025)the Interdisciplinary Innovation Foundation for Graduates at Nanjing University of Aeronautics and Astronautics in China(No.KXKCXJJ202002).
文摘A novel perforated-rib configuration is proposed for controlling the tip leakage flow at the rotor tip of an axial turbine.Three perforated-rib layouts are considered,wherein a perforated rib is installed at(A)the Suction-Side squealer(SS-rib),(B)the Pressure-Side squealer(PS-rib),and(C)the additional squealer along the blade Camber Line(CL-rib).A numerical method is used to show how the novel rib layouts affect the aerodynamic performance of the tip leakage flow.Results show that the coolant jets issuing from the perforated-rib injection holes penetrate deeper into the tip clearance than those in the baseline squealer-tip case,and how the perforated-rib coolant injection affects the tip leakage flow depends strongly on the rib layout.The PS-rib and CL-rib layouts appear promising for controlling the tip leakage flow,playing a significant role in reducing the total pressure loss and improving the turbine blade’s isentropic efficiency.In particular,under an injection mass flow ratio of 1%and a tip clearance of 1%blade span,the PS-rib layout reduces the leakage mass flow rate by 27%and increases the isentropic efficiency by 1.25%compared with those in the baseline squealer-tip case.Meanwhile,the advantages of the PS-rib layout in tip leakage control are confirmed under small and large tip clearances.
