Hydraulic Model Test of the Bottom Outlet of Sivand Dam
This paper presents the results of hydraulic test of bottom outlet of the Sivand Dam. The aims of the hydraulic model test are, gate discharge characteristics and gate loading. Results for different gate openings are also compared with calculated values obtained by a finite element method. Key-Words: Hydraulic model test, Dam, Finite element method, Gate, Gate Discharge
A design criterion for dynamic stability of Tainter gates
Abstract Elastically suspended Tainter gates (radial gates) may induce a rigid-body vibration around the trunnion pin, accompanied by discharge variations. The fluctuating discharge causes a fluctuation of pressure acting on the gate which may induce gate vibrations. Such a small-amplitude flow-induced vibration of Tainter gates is described by a homogeneous integral-differential equation. In this study, this homogeneous equation is approximately solved to obtain solutions for the excitation ratio (negative damping ratio) and vibration frequency. The solutions are given for a variety of parameters, such as basic Froude number, mass ratio and equivalent damping ratio. The predictions are compared with experimental data on Tainter-gate vibrations. A design criterion is presented, which ensures the stability of Tainter gates with respect to a significant source of self-excited vibration that was previously ignored.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.