5kW and 100kW Pelton Turbine Design and Performance Analysis for Air Injected Operation

Abstract

In this study, a new efficiency improvement method by means of air injection into Pelton turbine jet is presented. In the penstock, when a certain percentage of air is injected into the water the flow rate of the combined air water mixture will increase. Then this increased velocity of mixture produces more power on the runner. In order to analyze air injected jet performance, firstly, micro size 5kW Pelton turbine was designed and analyzed. Similarly the analysis was carried out on a small size 100kW turbine. Furthermore, Cavitation analysis was performed for both water injected jet analysis and normal jet analysis, in order to determine if there is tendency for vapor to form with the air injected method.

In the hydraulic industry, there isn’t a specific designing method of Pelton turbine available and commercial Pelton turbine design is secure within manufacturers due to high competitive market. However, there are some literature available relating to general thumb rules of design of Pelton turbine. Recent model of Pelton turbine was designed according to general rules. Specific section of the bucket such as bucket profile, bucket back side and notch is based on designer’s idea. For the 100kW Pelton turbine, 5kW model was scaled up based on the jet diameter and rotational speed. 5kW performance analysis was performed under several rotational speed. After achieving optimized rotational speed. Air injected jet analysis was performed for rated rotational speed condition. Air injection rate was 1%, 5%, 10%, 15% of the water volume flow rate. Efficiency increase rate was reliable, therefore same analysis performed for a 100kW Pelton turbine. The 100kW turbine was designed in two types, one jet and two jets systems. Air injection rate was made same and also found to have a reliable increase in efficiency. ICEM CFD meshing tool was used for meshing and CFX 13 commercial tool was used for numerical analysis.