소수력용 프란시스 수차의 고성능화를 위한 직접설계법의 개발 및 적용에 관한 연구

Abstract

In order to strengthen the national competitiveness of natural disasters such as earthquakes and typhoons, which are frequently occurring at home and abroad, energy independence and the acquisition of clean energy using new and renewable energy Interest is growing.

Especially in Korea, due to the saturation of the hydro energy market, entry of foreign competitors into the market, lack of fundamental technology related to hydro power and lack of professional technical personnel, technology is becoming more and more important.

In this study, we propose a new design process that combines the fundamental design technology and the latest design technology for the francis turbine, which is widely used in the hydropower market, and confirm its feasibility.

The design theories that were applied to the francis turbine was reestablished for small hydropower generation, and design by applying 1 pitch analysis method of the stay vanes, guide vane, runner was confirmed possible by using ANSYS BladeGen and CFD.

Especially, in the flow analysis performed based on the design data, the efficiency of the francis turbine measured by considering the loss of leakage was 90.62%.

Based on the results of the flow analysis, was measured at 88.9% under the 73kW turbine output design condition. Therefore, it was confirmed that the design of the francis turbine was performed very well as a result of the analysis of the turbine through the analysis and the experiment.

In order to apply the direct design method, the height of inlet, design flow-rate, and theoretical drift for the blade inlet and outlet velocity triangles based on the theoretical head calculation, we can easily determine the shape of the runner blade and determine the adoption of the selected shape through the flow analysis to the extent that the outflow angle of the runner satisfies 90 degrees. This method can confirm the result in a very short time compared with the existing design method, and confirms the same result as full domain analysis in an error range of less than 2%.

The results show that the leakage loss of inside of the francis turbine is mainly occupied by the leakage loss in runner inside and can be expected to improve the efficiency of the turbine by reducing the leakage loss.

In particular, according to the results of the loss distribution analysis, it was confirmed that the efficiency of the turbine can be improved most remarkably when the performance of the runner, the guide vane and the draft tube is improved. In this study, it is confirmed that the efficiency loss due to leakage loss reaches 1.66%, and the efficiency is more than 90% because the loss is decreased when the output and flow rate increase.

Therefore, it is possible to supply high performance turbine when the improvement method of the turbine is applied through the loss analysis in the design stage. And when the direct design method is applied, the high efficiency francis turbine can be supplied in market with a short time delivery.

In addition, it is expected that the high efficiency francis turbine can be applied to the low specific speed range of less than 70 (lower than Ns70) and the high specific speed range of which the speed is higher than 300. The efficiency of francis turbine will be increase and it will be able to secure various economic benefits by expanding the scope of application.