In order to improve the efficiency of pump-as-turbine (PAT), a specific speed 193 centrifugal pump with noncircular section spiral volute is chosen as a research object and one kind of special impeller is designed for the turbine's working condition. The relational expression between trapezoidal geometry characters and radius of equivalent circle is derived based on the area equal principle. The velocity moment at impeller inlet is acquired on the basis of constant velocity moment theory. And the relational expression between blade inlet angle and rated flow rate is derived. Considering the relatively large inlet width of blade, the blade axial projection draw is divided into two parts. Three outlet angles at the intersection of the three meridional streamline and blade trailing edge are calculated, respectively. The new special turbine impeller is modeled by using ANSYS BladeGen and NX software. The impeller is manufactured and the performance test is carried out on an open PAT test rig. To understand how the performance is improved, a verified computational fluid dynamics technique is adopted in the turbine mode performance prediction of PAT with the two impellers. The comparison of new impeller and the original PAT experimental results shows that the highest efficiency is raised from 71.9% to 77.3%. The best efficiency is increased by 7.5%. Compared with original PAT performance curves, the efficiency curve of PAT with new impeller is flat, and the high efficiency operating range of the special impeller is wider than that of the original impeller. The new impeller can adapt to large variation range of flow rate. The efficiency of PAT with new impeller is above 72% between 75-130 m3/h operating ranges. Numerical calculation results show that the new special impeller blade inlet angle can match well with the flow of the spiral volute outlet. The energy transformation is more uniform from the blade inlet to the blade outlet in new impeller. Hydraulic loss analysis shows that the hydraulic loss within the new special impeller is significantly less than that of the original impeller at a high flow rate. The experimental best efficiency point is consistent with the given design flow rate. Thus, it is verified that the impeller design theory and method proposed in this paper is reasonable. Research results have important meaningful to enrich the PAT impeller design theory and method.
WANG Tao
,
KONG Fanyu
,
YANG Sunsheng
,
CHEN Kai
,
LIU Yingying
. Design and Experiment of Impeller of Centrifugal Pump as Turbine with Trapezoidal Cross-section Volute*[J]. Journal of Mechanical Engineering, 2018
, 54(10)
: 202
-210
.
DOI: 10.3901/JME.2018.10.202
[1] ELBATRAN A H, YAAKOB O B, AHMED Y M, et al. Operation, performance and economic analysis of low head micro-hydropower turbines for rural and remote areas:A review[J]. Renewable and Sustain Energy Reviews, 2015, 43:40-50.
[2] GIOSION D R, HENDERSON A D, WALKER J M, et al. Design and performance evaluation of a pump-as-turbine micro-hydro test facility with incorporated inlet flow control[J]. Renewable Energy, 2015, 78:1-6.
[3] WANG Tao, KONG Fanyu, XIA Bin, et al. The method for determining blade inlet angle of special impeller using in turbine mode of centrifugal pump as turbine[J]. Renewable Energy, 2017, 109:518-528.
[4] BUONO D, FROSINA E, MAZZONE A, et al. Study of a pump as turbine for a hydraulic urban network using a tridimensional CFD modeling methodology[J]. Energy Procedia, 2015, 82:201-208.
[5] NAUTIYAL H, VARUN K A. Reverse running pumps analytical, experimental and computational study:A review[J]. Renewable and Sustain Energy Reviews, 2010, 14:2059-2067.
[6] SINGH P, NESTMANN F. An optimization routine on a prediction and selection model for the turbine operation of centrifugal pumps[J]. Experiment Thermal and Fluid Science, 2010, 34:152-164.
[7] DERAKHSHAN S,MOHAMMADI B.The comparison of incomplete sensitivities and genetic algorithms applications in 3D radial turbo machinery blade optimization[J]. Computers & Fluids, 2010, 39(10):2022-2029.
[8] YANG Sunsheng, DERAKHSHAN S, KONG Fanyu. Theoretical, numerical and experimental prediction of pump as turbine performance[J]. Renewable Energy, 2012, 48:507-513.
[9] 杨军虎,龚朝晖,夏书强,等.导叶对液力透平性能影响的数值分析[J].排灌机械工程学报,2014,32(2):113-118. YANG Junhu, GONG Zhaohui, XIA Shuqiang, et al. Numerical analysis on influence of guide vanes on performance of centrifugal pump acting as hydraulic turbine[J]. Journal of Drainage and Irrigation Machinery Engineering, 2014, 32(2):113-118.
[10] GIOSION D R, HENDERSON A D, WALKER J M, et al. Design and performance evaluation of a pump-as-turbine micro-hydro test facility with incorporated inlet flow control[J]. Renewable Energy, 2015, 78:1-6.
[11] 陈凯,孔繁余,王桃,等. 叶轮外径对前弯型液力透平性能的影响[J]. 机械工程学报, 2016, 52(22):198-204. CHEN Kai, KONG Fanyu, WANG Tao, et al. Numerical research on impeller diameter influencing the performance of hydraulic turbine with forward-curved blades[J]. Journal of Mechanical Engineering, 2016, 52(22):198-204.
[12] WANG Tao, WANG Chuan, KONG Fanyu, et al. Theoretical, experimental, and numerical study of special impeller used in turbine mode of centrifugal pump as turbine[J]. Energy, 2017, 130:473-485.
[13] 王桃,孔繁余,杨孙圣,等.叶片安放角变化规律对液力透平性能影响的研究[J].农业机械学报,2015,46(10):75-80. WANG Tao, KONG Fanyu, YANG Sunsheng, et al. Effects of the blade angle distributions on performance of pump as turbine[J]. Transactions of the Chinese Society for Agricultural Machinery, 2015, 46(10):75-80.
