The impact of inlet angle and outlet angle of guide vane on pump in reversal based hydraulic turbine performance

Transcription

1 IOP Conference Series: Earth and Environmental Science The impact of inlet angle and outlet angle of guide vane on pump in reversal based hydraulic turbine performance To cite this article: F X Shi et al 2012 IOP Conf. Ser.: Earth Environ. Sci Related content - Research of performance prediction to energy on hydraulic turbine H Quan, R N Li, Q F Li et al. - Research on the effect of wear-ring clearances to the performance of centrifugal pump W G Zhao, Y B Li, X Y Wang et al. - The hydraulic design of pump turbine for Xianyou pumped storage power station J S Zheng, W C Liu, Z Y Fu et al. View the article online for updates and enhancements. This content was downloaded from IP address on 01/10/2018 at 22:10

2 The impact of inlet angle and outlet angle of guide vane on pump in reversal based hydraulic turbine performance F X Shi 1, J H Yang 1, X H Wang 1, R H Zhang 1 and C E Li 2 1 School of Energy and Power Engineering, Lanzhou University of technology, GanSu, Lanzhou,730050, P.R.China 2 School of civil engineering, Lanzhou University of technology, GanSu, Lanzhou, P.R.China lzyangjh@lut.cn, shifengxia_168@126.com Abstract. In this paper, in order to research the impact of inlet angle and outlet angle of guide vane on hydraulic turbine performance, a centrifugal pump in reversal is adopted as turbine. A numerical simulation method is adopted for researching outer performance and flow field of turbine. The results show:inlet angle has a crucial role to turbine,to the same flow,there is a noticeable decline for the efficiency and head of turbine with the inlet angle increases. At the best efficiency point(efp),to a same inlet angle,when the inlet angle greater than inlet angle, velocity circulation in guide vane outlet decreases, which lead the efficiency of turbine to reduce, Contrarily, the efficiency rises. With the increase of inlet angle and outlet angle, the EFP moves to the big flow area and the uniformity of pressure distribution becomes worse. The paper indicates that the inlet angle and outlet angle have great impact on the turbine performance, and the best combination exists for the inlet angle and outlet angle of the guide vane. 1. Introduction In recent years, Hydraulic turbine have been used widely in oil coal chemical and petroleum processing industry. The research on hydraulic turbine has become more and more deep than before, Which mainly focused on how to improve turbine efficiency how to improve the uniformity of runner inlet circulation and how to improve the controllability of the rotation speed[1]-[7]. Both runner entrance edge rounded and shroud and hub rounded can improve turbine efficiency[4]-[5]. When pump is used as a turbine(pat), PAT should be equipped with a guide vane, pressure coefficient changes little and efficient changes greatly with flow coefficient changes, but the efficient of best efficient point is improved[6]. Pump with guide vane in reversal drained better than volute [7]. The turbine(pat) with a guide vane can make the circulation in runner inlet well distributed and efficiency improved,but no documents mentioned the guide vane shape, the influences of blade numbers, inlet and outlet angle and speed circulation on turbine. In this paper,under the circumstance that the basic geometry parameter of runner is uniform, the impact that the inlet and outlet angle on turbine performance is researched by numerical simulation. 2. Research approach Published under licence by Ltd 1

3 In order to research the impact of guide vane inlet and outlet angle on hydraulic turbine, a single stage centrifugal pump ( n = 51) in reversal is adopted as a turbine (PAT). The design parameter of pump: s rotating speed n = 2950r / min,flow Q = 63m 3 / h, head H = 81m. As a turbine, pump inlet is thought of turbine outlet, pump outlet is thought of turbine inlet. According to the difference of guide vane inlet angle and outlet angle, four troops of schemes are designed for turbine. The thickness of Guide vane blade is accordant with that of runner blade: S = 4mm, Guide vane blade numbers: Z = 6. For the guide vane length: it will not be able to hold the flow if it is too short, but if it is too long, which will increase the volute size and flow losses. given a consideration to runner and volute sizes, guide vane length is designed for 30mm and 40mm. In order to link volute and guide vane well, round shape is adopted for volute section. Further more, In order to prevent liquid separation and less decrease of impact losses, Non impact inlet is adopted for guide vane,guide vane inlet angle equals to Volute helical angle,and the calculation results show:inlet angle equals to 13 and outlet angle equals to 18. The criteria of guide vane outlet angle selection: Speed circulation adds or subtracts doesn t depend on guide vane form, but depends on guide vane inlet angle and outlet angle [8]. Two conditions are considered to the guide vane outlet angle selection: speed circulation increasing and speed circulation decreasing. The calculation value of inlet angle outlet angle and length of guide vane is given in table 1, four schemes are indicated by A B C D Table 1. The value of guide vane A B C D Length(mm) Inlet angle( ) Outlet angle( ) Numerical simulation and method Firstly, pro/e software is adopted for founding entity model,secondly,gambit software is adopted for meshing, Finally fluent6.3 is adopted for number simulation to four models. Continuity equation and Reynolds time-averaged Navier Stokes equations (RANS) are included for Control Equations. RNG k ε turbulent model and SIMLEC algorithm are adopted, Velocity field and pressure field are coupled. Boundary condition: velocity condition is defined in inlet, the value of which is calculated by the ratio of flow and inlet area, and pressure condition is defined in outlet. For boundary condition, it is should be non-slip in solid wall surface. the calculation region is included from volute inlet to runner outlet,one time for completing calculation. Table 2. The value for calculation at EFP flow(m 3 h -1 ) torque(n m) head(m) η A B C D Results and discussions The results for performance parameter of four schemes at the best efficiency point (EFP) are shown in table 2. 2

4 4.1. The impact for inlet angle and outlet angle on turbine outer performance Q H characteristic Curves Q η characteristic Curves are shown in figure 1 and figure 2. The efficiency of PAT begins to increase and then decreases with the increasing of flow,the head increases rapidly when flow increases,to the same flow,there is a noticeable decline in efficiency when inlet angle increases. At the best efficiency point(efp),scheme A has the highest efficiency, scheme D has the lowest efficiency,scheme A is 7 percent higher on efficiency than scheme D. However,speed circulation in guide vane outlet increases for scheme A,and decreases for scheme D. With the increasing for inlet angle,the best efficiency point (EFP) moves to big flow area. This shows it is benefit for raising efficiency if increase speed circulation in guide vane outlet Speed circulation decreases does not benefit for increasing turbine efficiency, inlet and outlet angle increasing makes against turbine performance Figure 1. Q H characteristic Curve for A B C and D Figure 2. Q η characteristic Curves for A B C and D Turbine characteristic comparison Curves were shown in figure 3, in which inlet angle is identical,but the outlet angle was different. Turbine characteristic Curves changes with the change of outlet angle Comparing scheme A and scheme B,both the Q H characteristic Curves and Q η characteristic Curves are more smooth. Before the best efficiency point(efp),both the efficiency and head of scheme A are higher than that of scheme B,after the best efficiency point(efp),turbine characteristic curves of scheme A and scheme B almost have no differences. At the best efficiency point(efp),the flow of scheme A and scheme B is equal,but the head of scheme A is lightly higher than scheme B. Comparing scheme C and scheme D, both the efficiency and head characteristic curves of scheme D are more smooth than that of scheme C,but the best efficiency point of scheme D moves to right, the highest efficiency of which also lower than that of scheme C. 3

5 (A) (B) (C) (D) Figure 3. Turbine characteristic-curves for scheme A B C and D compared by figure 3, the inlet angle and outlet angle of scheme A is the most suitable,fig 3 shows if the selection of inlet angle is appropriate,the impact of outlet angle on turbine is lesser. On the contrary,if the selection of inlet angle is not appropriate,outlet angle has an deep effect on turbine performance. Generally speaking,to the same inlet angle,inlet angle greater than outlet angle,that is to say the circulation increasing in guide vane outlet is benefit for turbine performance. So to the PAT,the optimal combination exists for guide vane inlet angle and outlet angle 4.2. The impact of guide vane inlet angle and outlet angle on static pressure distribution of turbine runner and blades The static pressure distributions in guide vane and runner of scheme A B C and D are shown in figure 4. The pressure decreases gradually from runner inlet to outlet,both guide vane and runner pressure distributes evenly in scheme A, scheme B weakly inferior to that of scheme A,the pressure doesn t distribute evenly in flow field of guide vane of scheme C, and scheme D is the worst,further more,low pressure existed in partial area in scheme D. All above comparison:the change of guide vane inlet angle and outlet angle led the pressure to change of runner flow field. Inlet angle increases,the uniformity of pressure distribution in flow field of guide vane and runner becomes worse. To the same inlet angle,the uniformity of pressure distribution when outlet angle greater than inlet angle was better than that of outlet angle lesser than inlet angle. This shows speed circulation increase is benefit for turbine performance. (A) (B) (C) (D) Figure 4. Static pressure distribution for Guide vane and runner of A B C and D 4

6 (A) (B) (C) Figure 5. Static pressure distribution in radial direction of blade pressure side and suction side for A B C and D 5. Conclusions On the basis of other basic sizes of turbine are definite,the impacts on hydraulic turbine outer performance and flow field by guide vane inlet angle and outlet angle are researched. Which are summarized as follows: (1) Changes of inlet angle and outlet angle lead speed circulation in guide outlet to change, Change of speed circulation lead outer performance parameters of turbine to change. To the inlet angle of the guide vane purely,inlet angle increases, efficiency and head are noticeable declined, the best efficiency points move to big flow area. To the same inlet angle, when outlet angle greater than inlet angle, it will leads speed circulation in runner inlet to decrease and leads turbine efficiency to decline, which is not benefit for turbine performance. (2) Changes of inlet angle and outlet angle lead speed circulation in guide outlet to change, and which will leads pressure distribution of runner to change. With the increasing of guide vane inlet angle, the uniformity of static pressure in runner becomes worse than before. To the same inlet angle, when outlet angle greater than inlet angle, speed circulation in runner inlet decreases, the pressure distribution is less even than that of outlet angle lesser than inlet angle. (3) To PAT, when other sizes are definite, the best optimal Combination for inlet angle and outlet angle exists. That is, the optimal value for speed circulation exists in runner inlet. In this paper, given consideration to outer performance and flow field static pressure, the optimal value for inlet angle and (D) 5

7 outlet angle is 13 and9, namely scheme A is the best. Too big inlet angle and outlet angle doesn t benefits for turbine performance, inlet angle of guide vane is crucial for turbine performance. Acknowledgements This research is supported by Lanzhou University of Technology (No. 1112RJZ027) and the Natural Science Foundation of China (No ). These supports are gratefully acknowledged. Reference [1] Van Antwerpen H J and Greyvenstein G P 2005 Energy Conversion and Management [2] Predeep B and Nick M 2010 Applied Energy [3] Gong S H 1989 Small Hydropower 5 25 (in Chinese) [4] Shahram D, Bijan M and Ahmad N 2009 J. of Fluids Engineering [5] Xin B R 2000 Foreign Heavy Motor 2 72 (in Chinese) [6] Ferandez J and Blance E 2010 J. of Power and Energy [7] Ventrone G, Ardizzon G and Pavesi G 2000 Proc. Instn. Mech. Engrs [8] Cao K, Yao Z M 1991 Water-Turbine Principle and hydraulic design (Beijing: Tsinghua University press) pp