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Numerical aided design of Pelton nozzle jet deflector

Popovski Boro, Lipej Andrej

Journal of Mechanical and Energy Engineering

2021

Vol. 5, No 2

149--156

Hydro energy still occupies an important place among renewable energy sources. In special operating conditions, Pelton turbines are irreplaceable and can be used for extremely small hydropower plants and also large hydro power plants. Pelton turbines can operate with high head and relatively small flow rates. In many cases, the height differences of the water are very large. Sometimes it is necessary to stop the operation of the turbine very quickly and the consequences of water hammer can be very severe. The responsible part to minimize the consequences of this phenomena is jet deflector, which can be in two different technical designs. The steps for 3-D geometry definition, pre-processing and post-processing, flow modelling and FEM analysis are presented. In the paper is presented the new optimized design of push-out jet deflector shape. Optimization consider 3-D CFD analysis of free surface flow and stress analysis. The main goal of the research was to minimize the influence of all force components on the torque of deflector servomotor. The final results present the geometry of the deflector, with a significant reduction in the stresses and deformations. These have been achieved with a crucial reduction in the hydrodynamic force and torque.

Analysis of numerical instability of centrifugal pumps operational characteristics

Lipej Andrej

Journal of Mechanical and Energy Engineering

2020

Vol. 4, No 4

357--364

In recent years, computational fluid dynamics has been increasingly used in the development of various types of rotating machines. In the case of water turbines and pumps, a large number of researches have been published recently, related to the use of different numerical methods for prediction of efficiency, cavitation characteristics and different dynamic phenomena. For basic analysis an accurate result near the optimal operating regime is sufficient, but for detailed analysis the numerical analyses in the wider field of operating conditions are necessary. Thus, some otherwise known physical phenomena that occur in the part-load and full-load regime may be encountered. In these areas, due to the nature of the flow, various non-stationary phenomena occur that are dominant for such operating regimes. This paper presents the problems that arise if only stationary results are taken into account, and some recommendations for avoiding subsequent problems in the operation of centrifugal pumps.