Determination of Casting Parameters for Affirmative Directional Solidification in 750 KW Francis Runner

Abstract

Abstract Entangled by a web-like pattern of rivers and rivulets, Nepal’s energy sector currently is dominated by hydroelectricity which sustains a major portion of the country’s economy. But still, after more than a hundred years of its operation, the sector’s dependence on imports is uncanny. This not only upsizes the project cost but also the time and human resources. The research, therefore, aims to aid the cause by examining the prospect of manufacturing runners using local industrial expertise in synchronization with available data and research. Here, the paper focuses on the sand casting of a 750KW Francis runner and the design of its parameters namely gating and feeding system to ensure directional solidification. Apart from the conventional procedure, the casting of the runner was proceeded as three separate parts: hub, shroud, and blade which were later welded together. The gate and riser placement for each of the parts was designed independently and analysed for any shrinkage porosities and possible voids using computer simulation with several iterations each. Specifically, temperature variations during three major stages of solidification assigned as 0, 50, and 100 were tested for a total of 195 nodes. The design was then transferred into the mould and casting was performed. The procedure resulted in a cast with a clean surface finish and minimal visible defects. The study, thus, suggests the possibility of manufacturing runners through metal casting and its substantial implications in the improvement of the hydropower industry in Nepal.