Kukhtenkov Y. Forecasting of low-frequency pulsations of pressure in Francis turbine and a way of their reduction

Object of research - low-frequency processes of pulsations of pressure in a draft tube caused by movement vortical swirl. The purpose of research - forecasting pulsations characteristics of draft tube on the basis of spatial mathematical model of movement vortical swirl in a draft tube and decrease in a level of swirl pulsations due to application of constructive actions. Methods of research - mathematical and physical modelling which have allowed to predict swirl pulsations of pressure in a draft tube on the basis of models of current of an ideal liquid. The experimental method was applied at definition of amplitudes and frequencies of pulsations of pressure from vortical swirls and their geometrical and kinematic parameters to forecasting swirl pulsations of pressure in draft tube of hydraulic turbines. Novelty - is developed mathematical model of calculation of swirl pulsations of pressure in view of any number vortical swirl and additional ax symetrical a stream in draft tube Francis hydraulic turbines that allows to predict more precisely characteristics; it is offered for numerical realization of a problem on forecasting pulsations of pressure to find intensity of a vortical surface which models a wall of the draft tube, as set lines Furie with unknown factors at the decision of equation Fredholm, and intensity vortical swirl - from simplified ax symetrical tasks; for the first time laws of change of the basic geometrical parameters vortical swirls in the draft tube in a wide range of operating modes of the hydraulic turbines are determined and received approximations dependences for forecasting pulsations characteristics on the basis of the lead experiments on modelling hydraulic turbines. Results - the technique allowing with sufficient accuracy to expect and analyze pulsations of the characteristic in Frencis hydraulic turbines is developed; comparison the forecast characteristics with results of modelling and natural experiments specifies their satisfactory coordination is enables to define more precisely a zone of operation of the hydraulic turbines and to use these data in calculations on durability of elements of the hydrounit; the technique of construction of the peak and frequency characteristic of pulsations of pressure from several vortical swirls in draft tube Frencis hydraulic turbines of the water-wheel is developed in view of borders of transition that allows to estimate a level unstability in a wide range of operating modes; on the basis of experiments in modelling hydraulic turbines on pressures of 100-300 meters are determined dependences of geometrical parameters vortical swirls in a draft tubes from operating modes that enables to carry out calculations on forecasting pulsations of pressure; application of various practical actions - lengthened flower the driving wheel, different designs Frencis of driving wheels with rotary elements, an admission of air under the driving wheel allows to reduce considerably pulsations of pressure in a sucking away pipe of the water-wheel. Introduction - has been developed by Hydromachine Machinery Department of NTU " KhPI", OAS "Turboatom" Kharkov. Branch - power mechanical engineering.