S. Pudasaini et al.: Computational Fluid Dynamics (CFD) analysis of Pelton runner of Khimti Hydro-power Project of....... Rentech Symposium Compendium, Volume 4, September 2014 91 Computational Fluid Dynamics (CFD) analysis of Pelton runner of Khimti Hydro-power Project of Nepal Sanam Pudasaini* 1 , Hari Prasad Neopane 1 , Amod Panthee 1 , Anuj Pathak 1 and Bhoj Bahadur Chaudhary 1 1 Turbine Testing Laboratory, Department of Mechanical Engineering, School of Engineering, Kathmandu University, Dhulikhel, Nepal Abstract - Nepal, with its diverse topological features and rich water resources, boasts a huge hydro energy potential with ability to generate 42000 MW of electricity. Higher mountains providing higher heads and seasonal variation in flow rates appropriates thechoice of Pelton turbines for hydro power projects in the country. The flat efficiency curve maintained by Pelton turbine on wide operating ranges counters for the seasonal variations seen in the rivers of Nepal. However, the design and manufacturing cost of actual Pelton prototype is very high. Redesigning and optimization process becomes even more costly and time consuming. However, the introduction of numerical tools has changed the design engineer’s procedures in the process of new Pelton turbines design. The research was carried out in order to perform CFD analysis of Pelton runner of Khimti Hydropower. The runner was scaled down by meeting IEC 60193 standard. Whole simulation was performed in ANSYS-CFX. The results obtained from simulation showed high pressure in splitter and deep face of the bucket. The torque calculation was further used to calculate the efficiency and analytical validation of the runner. Index Terms - KhimtiHydropower, Pelton turbine, Computational Fluid Dynamics (CFD) andInternational Electrotechnical Commission (IEC) I. INTRODUCTION The Pelton turbine is an impulse turbine and uses kinetic energy of water for power extraction. It is used for sources with low flow rates and high heads. They have relatively lower efficiency than Francis turbine at its best efficiency operation. However, their flat efficiency curve widens application for varying operating conditions.The simulation is the process of developing virtual environment of real world process. The simulation is important before the actual operation of turbine as it helps to optimize the design according to obtained values of flow velocities, pressure distribution and efficiency. The results obtained from CFD are of great interest since these findings can be used to minimize testing time and cost as well as to analyze failure conditions. The research was performed to calculate and validate torque by computational method. ANSYS-CFX was used for the simulation process and drawing out the conclusion. Equations 1, 2 and 3 represent Navier Stokes equations of conservation of mass, momentum and energy respectively [1]. Reynolds Averaged Navier-Stokes (RANS) turbulence modeling is the appropriate choice for a Pelton turbine simulation [2]. The fluid used is incompressible and there is not significant change in temperature. Equations 4 and 5 are the modification for incompressible fluid and by neglecting energy equation. * Corresponding author: Sanam.pudasainee@gmail.com   +  =  (1)    =  +  ∙ ′  −  (2)    =   +  +  (3) ∙= (4)    =  +    −  (5) II. METHODS 2.1 Model studies and scaling down Scaling down of the prototype is important to reduce the time consumption and to ease the computational processing in normal computers. It is difficult to simulate with the actual condition in CFD. Equations 6,7 and 8 represents head coefficient, flow coefficient and power coefficient for model studies. The model is presumed to have same values of speed ratio, flow ratio and specific speed [3].      = !"#$%"$ (6) &  ’  = !"#$%"$ (7) (  ) * + = ,-./0. (8) The scaling factor of 0.35 was used. The factor greater than 0.28 was found to satisfy IEC 60193 criteria for Pelton turbines[4]. Table1 shows the values for prototype and model with same speed of 600 rpm. Table 1: Different parameters for prototype and model Parameters Unit Prototype Model Pitch circle diameter (PCD) mm 1400 490 Head (H) m 660 80.85 Discharge (Q) Ltr/s 2150 92.18 Power (P) kW 12000 63.02