Numerical assessment of transient flow and energy dissipation in a Pelton turbine during startup

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(9)

Published: Sept. 1, 2024

The Pelton turbine, known for its high application water head, wide efficient operating range, and rapid start-stop capability, is ideal addressing intermittent stochastic load issues. This study numerically analyzes the transient two-phase flow energy dissipation during startup of a turbine. Dynamic mesh technology controlled nozzle opening changes, momentum balance equations managed runner rotation. Findings showed that speed initially increased rapidly then more slowly, rate matched variations. Runner torque first rose linearly, decreased, with fastest decline closing. Hydraulic efficiency peaked early in reduction but dropped sharply. Strong vortices formed due to upstream inflow downstream backflow impact distributor pipe. jet needle guide vane improved converging section nozzle, began diffuse stroke. Initially, spread fully on bucket surface, later only affected tips. Pressure fluctuations supply mechanism were primarily motion, higher amplitude movement lower when stationary. These propagated upstream, weakening over distance. Reynolds stress work turbulent kinetic generation, respectively, dominated transmission dissipation, their maximum contribution exceeding 96% 70%. High-energy clusters corresponded positions, highlighting jet-bucket interference as crucial transport. established performance evaluation method turbine startups, supporting further investigation into characteristic parameters, evolution, patterns.

Language: Английский

Investigation into unsteady inter-blade vortex in Francis turbines: Insight from unit speed effect and alleviation strategy

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(12)

Published: Dec. 1, 2024

Inter-blade vortex is a special cavitation within the Francis turbine runner, which can trigger high-amplitude pressure fluctuations, significantly limiting flexible regulation capability. This paper numerically investigates impact of attack angle variations on evolution inter-blade vortices by varying unit speed. The volume, indicating intensity, initially decreases sharply, then diminishes before rising swiftly with volume pulsations. Two types emerge: type A observed at low speed, attaching intersection blade leading edge and runner crown, B, mid-crown channel high variational mode decomposition technology identifies frequencies, approximately 5.0fn B around 1.0fn. Hydraulic instability, primarily driven fluctuations from vortices, more influenced during transient simulations. Furthermore, an optimization approach including multi-objective multi-condition was developed to reduces strength, improving hydraulic efficiency 1.63% 3.84%, decreasing volumes 88.91% 70.19%, maximum fluctuation amplitudes reduced 57.7% 82.6% for respectively. These findings enhance stability across wide operating range.

Language: Английский

DESIGN OF HIGH HEAD RUNNERS OF FRANSIC TURBINES

Bulletin of the National Technical University KhPI Series Hydraulic machines and hydraulic units, Journal Year: 2024, Volume and Issue: 1, P. 20 - 27

Published: Nov. 29, 2024

The energy characteristics of the hydroturbine, reflecting total effect interaction flow with working bodies, allow us to judge operation machine as a whole. Information about qualities individual elements space is provided by balance. Using data balance, it possible identify most favorable conditions for joint space, that is, achieve their agreement increase level efficiency – important indicator hydroturbine. In order improve performance designed various analyzes are conducted, dependence kinematic and hydroturbine on its geometric parameters investigated. Such an analysis carried out find rational options space. paper presents design high head FR400, performed help programs developed at department "Hydraulic machines named after G. F. Proskura". method analysis, based application dimensionless parameters, described. To indicators preliminary stage hydro turbine design, multivariate calculations influence runner formation out. substantiate analyze results, predictive universal characteristic built. hydroturbines, general properties spatial lattices, well regularities fluid runner, were used. losses in Francis: spiral case, guide vane, draft tube optimal operating mode changes was performed. given results calculation study confirm efficiency, while maintaining mode, necessary change both position starting edge impeller law distribution angles along it.

Language: Английский