With application of the lock-up clutch in the torque converter（TC）, fuel economy is not much determined by its high-speed ratio transmission efficiency. As a benefit, more researches are focused on its low-speed rat...With application of the lock-up clutch in the torque converter（TC）, fuel economy is not much determined by its high-speed ratio transmission efficiency. As a benefit, more researches are focused on its low-speed ratio performance so as to improve vehicle gradeability and launching acceleration performance. According to the results of computational fluid dynamics（CFD） analysis, hydrodynamic loss inside the stator cascade accounts for 42% of the total energy loss at stalling speed ratio. It is found that upstream flow with large impingement angle results in boundary layer separation at the leading edge, which aggregates hydrodynamic loss and decreases circular flow rate dramatically at low-speed ratio. In this paper, a dual-blade stator is proposed to suppress the boundary layer separation, which is parameterized by using the non-uniform rational B spline（NURBS） method. The mean camber line and blade profile curve are expressed by a three control points quadratic open NURBS and a cubic closed one respectively. The key design parameters included the slot width and suction side shape of the primary blade are analyzed. The most effective slot width is found to be between 4% and 8% chord length, and the boundary layer separation can be suppressed completely by decreasing distribution of momentum moment at the primary blade and adding it to the leading edge of the secondary blade. As a result, circular flow rate and impeller torque capacity is increased by 17.9% and 9.6% respectively at stalling speed ratio, meanwhile, low-speed ratio efficiency is also improved. Maximum efficiency at high-speed ratio decreases by 0.5%, which can be ignored as the work of lock-up clutch. This research focuses on using the dual-blade stator to optimize low-speed ratio performance of the TC, which is benefit to vehicle power performance.展开更多
The methodology of calculation of the velocity distribution for the stream frictionless and the drops in the flow line, on the basis of the frictionless, two-dimensional, stationary, transonic and homogenous flow is e...The methodology of calculation of the velocity distribution for the stream frictionless and the drops in the flow line, on the basis of the frictionless, two-dimensional, stationary, transonic and homogenous flow is established. The knowledge of conditions that govern the low pressure section of steam turbines in the last stage to have an approximate movement of the droplets in the blade cascades and the accumulation of droplets on the stator blades, flowing through the steam, is presented. This study is used for developing a code in Fortran about the velocity distribution in the output of stator blades that have flow conditions of wet steam, in order to understand the causes that originate the erosion on the blades of the last stages in the low pressure section of steam turbines.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
基金Supported by National Natural Science Foundation of China(Grant No.51575393)
文摘With application of the lock-up clutch in the torque converter（TC）, fuel economy is not much determined by its high-speed ratio transmission efficiency. As a benefit, more researches are focused on its low-speed ratio performance so as to improve vehicle gradeability and launching acceleration performance. According to the results of computational fluid dynamics（CFD） analysis, hydrodynamic loss inside the stator cascade accounts for 42% of the total energy loss at stalling speed ratio. It is found that upstream flow with large impingement angle results in boundary layer separation at the leading edge, which aggregates hydrodynamic loss and decreases circular flow rate dramatically at low-speed ratio. In this paper, a dual-blade stator is proposed to suppress the boundary layer separation, which is parameterized by using the non-uniform rational B spline（NURBS） method. The mean camber line and blade profile curve are expressed by a three control points quadratic open NURBS and a cubic closed one respectively. The key design parameters included the slot width and suction side shape of the primary blade are analyzed. The most effective slot width is found to be between 4% and 8% chord length, and the boundary layer separation can be suppressed completely by decreasing distribution of momentum moment at the primary blade and adding it to the leading edge of the secondary blade. As a result, circular flow rate and impeller torque capacity is increased by 17.9% and 9.6% respectively at stalling speed ratio, meanwhile, low-speed ratio efficiency is also improved. Maximum efficiency at high-speed ratio decreases by 0.5%, which can be ignored as the work of lock-up clutch. This research focuses on using the dual-blade stator to optimize low-speed ratio performance of the TC, which is benefit to vehicle power performance.
文摘The methodology of calculation of the velocity distribution for the stream frictionless and the drops in the flow line, on the basis of the frictionless, two-dimensional, stationary, transonic and homogenous flow is established. The knowledge of conditions that govern the low pressure section of steam turbines in the last stage to have an approximate movement of the droplets in the blade cascades and the accumulation of droplets on the stator blades, flowing through the steam, is presented. This study is used for developing a code in Fortran about the velocity distribution in the output of stator blades that have flow conditions of wet steam, in order to understand the causes that originate the erosion on the blades of the last stages in the low pressure section of steam turbines.
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.
