Hydrodynamic Design of Thrust Ring Pump for Large Hydro Turbine Generator Units

Xide Lai,Xiang Zhang,Xiaoming Chen,Shifu Yang 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.1

Thrust-ring-pump is a kind of extreme-low specific speed centrifugal pump with special structure as numerous restrictions from thrust bearing and operation conditions of hydro-generator units. Because the oil circulatory and cooling system with thrust-ring-pump has a lot of advantages in maintenance and compactness in structure, it has widely been used in large and medium-sized hydro-generator units. Since the diameter and the speed of the thrust ring is limited by the generator set, the matching relationship between the flow passage inside the thrust ring (equivalent to impeller) and oil bath (equivalent to volute) has great influence on hydrodynamic performance of thrust-ring-pump. On another hand, the head and flow rate are varying with the operation conditions of hydro-generator units and the oil circulatory and cooling system. As so far, the empirical calculation method is employed during the actual engineering design, in order to guarantee the operating performance of the oil circulatory and cooling system with thrust-ring-pump at different conditions, a collaborative hydrodynamic design and optimization is purposed in this paper. Firstly, the head and flow rate at different conditions are decided by 1D flow numerical simulation of the oil circulatory and cooling system. Secondly, the flow passages of thrust-ring-pump are empirically designed under the restrictions of diameter and the speed of the thrust ring according to the head and flow rate from the simulation. Thirdly, the flow passage geometry matching optimization between thrust ring and oil bath is implemented by means of 3D flow simulation and performance prediction. Then, the pumps and the oil circulatory and cooling system are collaborative hydrodynamic optimized with predicted head-flow rate curve and the efficiency-flow rate curve of thrust-ring-pump. The presented methodology has been adopted by DFEM in design process of thrust-ring-pump and it shown can effectively improve the performance of whole system.

Investigation of pressure pulsations in a reactor coolant pump with mixed-flow vaned diffuser and spherical casing

Xide Lai,Daoxing Ye,Bo Yu,Xiaoming Chen,Yaguang Heng 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.1

Pressure pulsations are an important factors that cause unstable phenomena such as vibration and noise in the reactor coolant pump (RCP), which is much more complex than inside a general mixed-flow pump due to its structure and actual operating conditions. It is necessary to figure out its characteristics at different operating conditions in order to meet the high requirements of reliability and safety in both design and operation phases. Pressure pulsations inside the impeller and diffuser vanes was carefully investigated by using 3D unsteady flow simulations of the completed pump at 5 operating conditions. To seek the relationship between the pressure pulsations characteristics and operating conditions, the timedomain and frequency-domain characteristics of pressure pulsations at different locations inside the RCP were analyzed. It has been shown that the dominant frequency of pressure pulsations is mainly governed by the blade-passing frequency due to rotor-stator interaction (RSI) between the impeller and diffuser vanes at all operating conditions, and the amplitude of pressure pulsations mainly depends on the operating discharges. The influence on the peak amplitude of its higher harmonics can be neglected when operating at the design discharge, but cannot be negligible for operating at the smaller discharge. The behavior of pressure pulsations at the inlet of the impeller in circumferential direction is not the same and more intensive on the suction side than the pressure side of a blade at different operating conditions, but it is almost the same at the outlet of the impeller as the interaction between the impeller and diffuser vanes. The maximum amplitude of pressure pulsations mainly depends on the operating discharge and reaches the smallest level at the design operating condition. Due to geometric features of the spherical casing, the vortex flow inside the spherical casing leads to the highly irregular and unsteady pressure pulsations inside flow channel of the impeller and diffuser under the smaller discharge operating conditions, and the amplitude of pressure pulsations in higher frequencies increases with the decreasing of the operating discharge. The amplitude of pressure pulsations inside the whole flow channel distinctly increases when the RCP is operating at the extreme small operating discharge. The spherical casing does have influence on the pressure pulsations inside the impeller and diffuser vanes, the effect is stronger under smaller discharge operating conditions than at larger ones.

Hydrodynamic Design of Thrust Ring Pump for Large Hydro Turbine Generator Units

Lai, Xide,Zhang, Xiang,Chen, Xiaoming,Yang, Shifu Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.1

Thrust-ring-pump is a kind of extreme-low specific speed centrifugal pump with special structure as numerous restrictions from thrust bearing and operation conditions of hydro-generator units. Because the oil circulatory and cooling system with thrust-ring-pump has a lot of advantages in maintenance and compactness in structure, it has widely been used in large and medium-sized hydro-generator units. Since the diameter and the speed of the thrust ring is limited by the generator set, the matching relationship between the flow passage inside the thrust ring (equivalent to impeller) and oil bath (equivalent to volute) has great influence on hydrodynamic performance of thrust-ring-pump. On another hand, the head and flow rate are varying with the operation conditions of hydro-generator units and the oil circulatory and cooling system. As so far, the empirical calculation method is employed during the actual engineering design, in order to guarantee the operating performance of the oil circulatory and cooling system with thrust-ring-pump at different conditions, a collaborative hydrodynamic design and optimization is purposed in this paper. Firstly, the head and flow rate at different conditions are decided by 1D flow numerical simulation of the oil circulatory and cooling system. Secondly, the flow passages of thrust-ring-pump are empirically designed under the restrictions of diameter and the speed of the thrust ring according to the head and flow rate from the simulation. Thirdly, the flow passage geometry matching optimization between thrust ring and oil bath is implemented by means of 3D flow simulation and performance prediction. Then, the pumps and the oil circulatory and cooling system are collaborative hydrodynamic optimized with predicted head-flow rate curve and the efficiency-flow rate curve of thrust-ring-pump. The presented methodology has been adopted by DFEM in design process of thrust-ring-pump and it shown can effectively improve the performance of whole system.

Diagnostics of nuclear reactor coolant pump in transition process on performance and vortex dynamics under station blackout accident

Daoxing Ye,Xide Lai,Yimin Luo,Anlin Liu 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10

A mathematical model for the flowrate and rotation speed of RCP during idling was established. The numerical calculation method and dimensionless method were used to analyze the flow, head, torque and pressure and speed changes under idle conditions. Regularity, using the Q criterion vortex identification judgment method combined with surface flow spectrum morphology analysis to diagnose the vortex dynamic characteristics on RCP blade. On impeller blade, there is two oscillations in the pressure ratio on pressure surface in blade outlet region. The velocity on the suction surface is two times more oscillating than the inlet of blade, and there is an intersection with the velocity ratio curve on pressure surface. On blade of guide vane, the pressure ratio increases along the inlet to outlet direction, and the speed ratio decreases with the increase of idle time. There is a vortex that rotates counterclockwise on the suction surface, and the streamline on the suction surface of blade is subjected to the entrainment and blocking action of the vortex creates a large reverse flow in the main flow region. There are two vortices at the outlet of guide vane suction side and the vortices are in opposite directions.

Effect of guide vane profile on the hydraulic performance of moderate lowspecific-speed Francis turbine

Xiaoming Chen,Xide Lai,Qiuqin Gou,Dongmei Song 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

The matching between the guide vane (GV) and runner is essential for the stable and efficient operation of hydraulic turbines. To investigate the compatibility between GV and runner, we have conducted the numerical calculations of a moderate low-specific-speed Francis turbine at 25 operating points within the operating range of 130-190 m head and 3-19° GV outflow angle. The energy characteristics, flow field characteristics, and static pressure variation of turbines with different GV profile types have been comparatively analyzed. The results show that moderate low-specific-speed Francis turbines with symmetrical and negative curvature GV demonstrate higher efficiency under medium to high head, 55-100 % rated output operating conditions. Under small opening and medium head conditions, the static pressure in the blade leading edge is smaller, and the low-pressure area is larger for the Francis turbine with positive curvature GV. When the GV opening increases, the relationship between the comparative values of static-pressure and low-pressure areas reverses. The turbine with positive curvature GV is more favorable for increasing static-pressure and narrow low-pressure areas, which can reduce the cavitation damage. Our study provides guidelines to optimize the design of GVs and runner for hydraulic turbines.