THE ENERGY APPROACH FOR ASSESSMENT OF DYNAMIC STRESSES IN HYDRAULIC TURBINES

Determination of dynamic stresses is an important step in assessing the strength, reliability and lifetime of hydraulic turbines. The diversity and complexity of dynamic processes in the flow part of hydraulic units cause major difficulties in their formalization and numerical simulations even for the steady state near the best efficient point. Experimental methods for determining dynamic stresses in the critical elements of full-scale hydraulic turbines, primarily the blade runner system, have a high cost, and the equipment has to be stopped for a long time for preparatory operations to be performed. Model experiments are usually carried out only at the design stage, which does not reflect all the specifics of hydraulic unit operation at the HPP. The approach to determining the actual dynamic stresses in the runner blades of a hydraulic turbine proposed in this article allows carrying out a quick estimate “from above” on the basis of the Hill chart of the turbine. The approach is based on the relationship between the level of dynamic perturbation flow in the flow part of the hydraulic turbine and the total energy losses affecting the efficiency value for this regime, and also the linear dependence of maximum stresses in the blade on the power for the given head values and rotation speed. A comparison of the experiments and the estimates conducted by the author proves the validity and feasibility of the proposed approach.