Recent approach to refurbishments of small hydro projects based on numerical flow analysis  Virtual hydraulic laboratory, developed in collaboration with turbine manufacturer by Jacek Swiderski Swiderski Engineering Ottawa, Canada  Study and analysis of the results allow developing an upgrade strategy  Selected practical applications of Computational Fluid Dynamics (CFD) based on commercial CFX-TASCflow software package.  Computational Fluid Dynamics (CFD) already established its strong presence in the hydropower industry as trusted engineering tool.

Why would older turbines need to be upgraded – would classical design methods be a reason ? (a) Aerodynamics theories adequate for a very limited range of water turbines (compressibility) (b) Existence of 3rd dimension component of the flow within the blade-to-blade space of a turbine runner (c) The upstream influence no classical, published design method takes it into account.

Design based on CFD verification Major design strategies exercised by the industry: A) Classical design approach: (i) model tests – modifications (loop: lab-shop) (ii) CFD analysis-model tests – modifications (loop:CFD-lab-shop) B) Newer approach – generic algorithms: model generation – CFD analysis – decision on shape modification (loop: CFD - Decision Program - CFD) C) Attempts to solve reverse problem: should there be a strict mathematical solution to the N-S equations, finding a shape of flow channel to achieve certain effect would be possible.

Practical methodology for an upgrade 1) Numerical model – full geometry of the turbine including - Intake - Spiral casing - Distributor (all stay vanes and wicket gates) - Runner - Draft tube 2) Tune-up of the numerical model - Grid quality: verification and refinement. Based on couple of runs of the flow analysis, the nodes distribution is adjusted according to the velocity/pressure field. - Operating parameters. In the non-dimensional factors, the CFD results must be within a certain range from the field measurements. 3) CFD analysis – flow solver 4) Analysis of results - Energy dissipation field (losses). - Pressure gradients – estimate possibilities for cavitation - Determination of the flow areas, where the velocity field has highest non-uniformity 5) Strategy for upgrade based on expected cost/benefit ratio - Intake shape - Distributor (wicket gates profile, stay vanes set-up) - Runner design - Draft tube shape

Modification of the stay vanes position resulted in 8% increase of energy production Upgrades implemented S piral Case Kaplan Unit – stay vanes replacement

Upgrades implemented Semi-spiral Case Kaplan Unit – blades replacement OLDNEW Hnet = 41 ft Generator output = 3000 kW Courtesy of NORCAN hydraulic turbine inc.

Courtesy of NORCAN hydraulic turbine inc.

Upgrades implemented Francis turbine – runner replacement Hnet = 50m Generator output guaranteed = 1615 kW (was 1500 kW) Generator output achieved = 1725 kW Output increase: 15% Courtesy of NORCAN hydraulic turbine inc.

Upgrades implemented Francis turbine – runner replacement Courtesy of NORCAN hydraulic turbine inc. Hnet = 105m Output before the upgrade = 4500 kW Output after the upgrade = 5200 kW (only runner replaced)

CFD diagnostics Classical Kaplan – erosion on the throat ring Tracking reason for cavitation

CFD diagnostics Classical Kaplan – leading edge tip: reasons for erosion

Bad inflow conditions on one side of the runner and very good on the other side CFD diagnostics Semi - Spiral Case Kaplan Unit