The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of th...The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of the straight stator stages are investigated and compared to those of the bowed stator stages. The results show that using bowed stator stages could alleviate the flow separation at both upper and low corners of the suction surface and the endwalls, and decrease the losses along the flow passage as well as the outlet flow angle. As the rotor/stator axial gap decreases, although the diffusion capacity of the compressor increases obviously, the outlet flow field in the straight stator stages deteriorates quickly. By contrast, little changes occur in the bowed stator stages, indicating that as the rotor/stator axial gap decreases, improved performance is achieved in the bowed stator stages.展开更多
A comparison of the results of a computational simulation and an experimental measurement indicates a good agreement between them： the bowed blade lowers the energy loss coefficient of engine by 11% in the simulation...A comparison of the results of a computational simulation and an experimental measurement indicates a good agreement between them： the bowed blade lowers the energy loss coefficient of engine by 11% in the simulation and by 13% in the measurement. To further discuss the application conditions of bowed blade in compressor, with incidence equal to zero and other boundary conditions unchanged, a computational investigations on four series of linear stators with different aerofoil turning angles are achieved. It is found that the bowed blade has much positive effect in high airfoil turning angle cascade, for example, the optimal retrofit of 30° bow angle highly reduces the energy loss coefficient by 17.9%, when the aerofoil turning angle is 59.5 °. But the optimal retrofit of 15° has only 0.7% reduction when the aerofoil turning angle is 39.5°, or even the compressor performance will get worse with the bow angle gradually increasing. Consequently, it is verified that the turning angle is one of the important factors to decide whether to apply the bowed blade into compressor at low Math number.展开更多
To improve the performance of the Turbofan engine,several measures should be considered during design process.Such measures,relating to aerodynamic characteristic design,include the maximum enthalpy per stage,the shor...To improve the performance of the Turbofan engine,several measures should be considered during design process.Such measures,relating to aerodynamic characteristic design,include the maximum enthalpy per stage,the shortest axial length,the minimum blade rows and the highest efficient in design and off design condition.To satisfy theses design characters,the meridian geometry of the engine will be excurvature at a high degree transition part between HP and LP turbines.The study is to investigate the effect of blade bowing on flow loss at blade tip and root of the type of turbine.Such turbine,tending towards separation,with severe secondary flow at the tip and strong radial flow at exit,was simulated by the 3D N-S solver Numerca,and there were several different stacking line bowing schemes in all.The results show that tip negative bowing and root positive bowing is able to weaken radial flow,consequently reduce the flow loss at the tip and root.展开更多
A commercial Navier-Stokes flow solver has been employed for simulating steady subsonic flow characteristics and analyzing the comparative features of flow fields between straight and bowed blades applied to the stato...A commercial Navier-Stokes flow solver has been employed for simulating steady subsonic flow characteristics and analyzing the comparative features of flow fields between straight and bowed blades applied to the stator of a high pressure steam turbine. For comparison, we have studied the effects of bowed blades on the wakes of stator trailing edge and horse shoe vortex in the rotor. It was found that the position of wakes for bowed blades is shifted toward the blade suction side. Also, we have discussed and compared the entropy generation and energy loss caused by dissipation mechanism within the boundary layers on the hub and shroud; and temperature gradient in meridional plane.展开更多
BACKGROUND In bow hunter’s syndrome(BHS),also known as rotational vertebral artery(VA)syndrome,there is dynamic/rotational compression of the VA producing verte-brobasilar insufficiency.Most occurrences involve atlan...BACKGROUND In bow hunter’s syndrome(BHS),also known as rotational vertebral artery(VA)syndrome,there is dynamic/rotational compression of the VA producing verte-brobasilar insufficiency.Most occurrences involve atlantoaxial rather than mid-cervical VA compromise,the latter being rarely reported.Herein,we detail successful VA decompression at mid-cervical spine,given a departure from its usual course.CASE SUMMARY The patient,a 45-year-old man,presented to our hospital with occipital headache and vertigo.Computed tomography angiography showed anomalous C4 entry of right VA,with compression upon head rotation to that side.Thyroid cartilage and anterior tubercle of C5 transverse process were visibly at fault.We opted for sur-gery,using an anterior cervical approach to remove the anterior tubercle.Patient recovery was uneventful and brought resolution of all preoperative symptoms.CONCLUSION BHS is an important consideration where aberrant coursing of VA and neurologic symptoms coexist.展开更多
基金National Natural Science Foundation of China (50646021)Chinese Specialized Research Fund for the Doctoral Pro-gram of Higher Education (20060213007)
文摘The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of the straight stator stages are investigated and compared to those of the bowed stator stages. The results show that using bowed stator stages could alleviate the flow separation at both upper and low corners of the suction surface and the endwalls, and decrease the losses along the flow passage as well as the outlet flow angle. As the rotor/stator axial gap decreases, although the diffusion capacity of the compressor increases obviously, the outlet flow field in the straight stator stages deteriorates quickly. By contrast, little changes occur in the bowed stator stages, indicating that as the rotor/stator axial gap decreases, improved performance is achieved in the bowed stator stages.
基金National Natural Science Foundation of China(50236020).
文摘A comparison of the results of a computational simulation and an experimental measurement indicates a good agreement between them： the bowed blade lowers the energy loss coefficient of engine by 11% in the simulation and by 13% in the measurement. To further discuss the application conditions of bowed blade in compressor, with incidence equal to zero and other boundary conditions unchanged, a computational investigations on four series of linear stators with different aerofoil turning angles are achieved. It is found that the bowed blade has much positive effect in high airfoil turning angle cascade, for example, the optimal retrofit of 30° bow angle highly reduces the energy loss coefficient by 17.9%, when the aerofoil turning angle is 59.5 °. But the optimal retrofit of 15° has only 0.7% reduction when the aerofoil turning angle is 39.5°, or even the compressor performance will get worse with the bow angle gradually increasing. Consequently, it is verified that the turning angle is one of the important factors to decide whether to apply the bowed blade into compressor at low Math number.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50576017)
文摘To improve the performance of the Turbofan engine,several measures should be considered during design process.Such measures,relating to aerodynamic characteristic design,include the maximum enthalpy per stage,the shortest axial length,the minimum blade rows and the highest efficient in design and off design condition.To satisfy theses design characters,the meridian geometry of the engine will be excurvature at a high degree transition part between HP and LP turbines.The study is to investigate the effect of blade bowing on flow loss at blade tip and root of the type of turbine.Such turbine,tending towards separation,with severe secondary flow at the tip and strong radial flow at exit,was simulated by the 3D N-S solver Numerca,and there were several different stacking line bowing schemes in all.The results show that tip negative bowing and root positive bowing is able to weaken radial flow,consequently reduce the flow loss at the tip and root.
文摘A commercial Navier-Stokes flow solver has been employed for simulating steady subsonic flow characteristics and analyzing the comparative features of flow fields between straight and bowed blades applied to the stator of a high pressure steam turbine. For comparison, we have studied the effects of bowed blades on the wakes of stator trailing edge and horse shoe vortex in the rotor. It was found that the position of wakes for bowed blades is shifted toward the blade suction side. Also, we have discussed and compared the entropy generation and energy loss caused by dissipation mechanism within the boundary layers on the hub and shroud; and temperature gradient in meridional plane.
文摘BACKGROUND In bow hunter’s syndrome(BHS),also known as rotational vertebral artery(VA)syndrome,there is dynamic/rotational compression of the VA producing verte-brobasilar insufficiency.Most occurrences involve atlantoaxial rather than mid-cervical VA compromise,the latter being rarely reported.Herein,we detail successful VA decompression at mid-cervical spine,given a departure from its usual course.CASE SUMMARY The patient,a 45-year-old man,presented to our hospital with occipital headache and vertigo.Computed tomography angiography showed anomalous C4 entry of right VA,with compression upon head rotation to that side.Thyroid cartilage and anterior tubercle of C5 transverse process were visibly at fault.We opted for sur-gery,using an anterior cervical approach to remove the anterior tubercle.Patient recovery was uneventful and brought resolution of all preoperative symptoms.CONCLUSION BHS is an important consideration where aberrant coursing of VA and neurologic symptoms coexist.
