Pressure-slope ventilation shafts used in lock chambers in high-head spillway tunnels

Abstract

The invention discloses a pressure slope type ventilation shaft used for a mid-gate chamber in a high-water-head flood discharging tunnel. The pressure slope type ventilation shaft comprises a vertical shaft section which is arranged on the downstream part of a gate shaft of the mid-gate chamber of the flood discharging tunnel and is located above the mid-gate chamber of the flood discharging tunnel. A main part of the vertical shaft section is located in a mountain at the top of the flood discharging tunnel. The upper end of the vertical shaft section stretches out of the mountain at the top of the flood discharging tunnel and communicates with the atmosphere. The pressure slope type ventilation shaft further comprises a flaring section and a pressure slope section. The lower end of the flaring section is larger than the upper end of the flaring section. The lower end of the flaring section is provided with an air outlet and is located at the position, located in the mid-gate chamber of the flood discharging tunnel, on the top wall of the flood discharging tunnel . The flaring section is gradually and smoothly changed and contracts from the lower end to the upper end to form a funnel type structure with the upper end capable of being jointed with the lower end of the vertical shaft section. The upper end of the flaring section is connected with the lower end of the vertical shaft section, so that the pressure slope section is located at the position, between the lower end of the flaring section and the gate shaft, of the top wall of the flood discharging tunnel and inclines from high to low in the water flowing direction. The requirement for the height of the ventilation shaft can be lowered, the possibility of cavitation and cavitation erosion is further lowered, meanwhile, the air speed is reduced, and vibration and noise of the mid-gate chamber structure are lowered.

Description

technical field [0001] The invention belongs to the field of ventilation systems for medium-pressure sluice chambers in water conservancy and hydropower projects, and in particular relates to a ventilation shaft used for medium-pressure sluice chambers in high-head pressure flood discharge tunnels. Background technique [0002] In the construction of high-head hydropower stations, it is common to use flood discharge tunnels for flood discharge projects, but there are also special hydraulic problems such as cavitation and erosion. In order to avoid the occurrence of cavitation erosion, it is necessary to set up aeration facilities. Ventilation wells are often set at the rear of the pressurized sluice chamber in the flood discharge tunnel, but if the ventilation wells are improperly set, two problems will arise: on the one hand, when the sluice chamber in the flood discharge tunnel is fully open (full load) and operates normally, the ventilation shaft entrance Cavitation or e...

AI Technical Summary

Problems solved by technology

Ventilation shafts are often installed at the back of the pressurized sluice chamber in the spillway tunnel, but if the ventilator shaft is not properly set up, it will cause two problems: on the one hand, when the sluice chamber in the spillway tunnel is fully open (full load) and operates normally, the ventilation shaft entrance Cavitation and even cavitation damage will occur due to the high-speed water flow in the flow channel; on the other hand, when the gate of the middle lock chamber is partially opened, the ventilation volume is insufficient or the wind speed in the ventilation shaft is too high, causing strong pulsation and hydraulic jump and rolling impact behind the gate. Unfavorable hydraulic phenomena such as cave roofs

This setting method has the following problems: (1) When the gate of the middle lock chamber is fully opened, the entire flood discharge tunnel will be filled with water flow. Since the flood discharge tunnel is a pressurized tunnel, the water pressure at the ventilation shaft will also be very high at this time, so The water level in the ventilation shaft will also reach a very high level

This requires the height of the ventilation shaft to be very high, which not only increases the construction cost of the ventilation shaft, but also restricts its use by the terrain; (2) When the gate is fully opened and the water flow fills the flood discharge tunnel, since the ventilation shaft is directly installed in the middle lock chamber At the top of the spillway tunnel, the junction between the ventilation shaft and the top of the spillway tunnel is prone to cavitation erosion due to the sudden change in shape; (3) When the gate is partially opened, the wind speed of the ventilating shaft in the high-speed spillway tunnel is relatively high, resulting in The structural vibration and strong noise of the gate and the middle lock chamber affect the normal operation and safety of the project

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