58. Optimizing Pelton Turbines for Refurbishment by Numerical Analysis

Conventional CFD packages available in the market solve 3-D Navier stokes equation for closed channel flows and for open channel flows and can be applied to evaluate flow parameters in reaction turbines like Francis & Kaplan type turbines. No commercially available computer package can be used directly to evaluate the two species (air & water) mixed flow phenomena encountered in jet/bucket interaction in Pelton turbines. Flow phenomena occurring in a pelton turbine runner is a very complex as it combines two species (air-water) flow interactions coupled with separation of water into droplets of various sizes and their subsequent miscibility & coalescing to form more droplets or streams. There is an element of randomness in this behaviour and a factor of non-commutativeness in modelling this, in terms of hydrodynamic flow equations. This is further complicated by the fact that the amount of refinement of geometrical & flow data, within which, this phenomena can be captured accurately, by means of a mathematical model, requires immense computer resources. Hence an alternative methodology has been worked out, to circumvent these problems. BHEL has developed a system of computer codes which has been used to analyse and improve the performance of Pelton runner bucket profiles. A high performance, efficient replacement runner has been designed, using suite of computer codes. This meets all stipulated customer requirements and provides a cost effective solution to the needs of renovation & refurbishment of Pelton type hydro turbines.