The flap gate can automatically control the water level and is mainly used to intercept or discharge water flow in reservoirs, rivers, reservoirs, etc.
It can achieve automatic control of water level, mainly using reservoirs, rivers, and reservoirs
Basic principles
The most widely used flap gate now is the hydraulic self controlled flap gate, which works by balancing and rotating the lever. Specifically, the hydraulic self controlled flap gate uses hydraulic and gate weight to balance each other, and achieves the goal of regulating water level by adding a damping feedback system: when the upstream water level rises, the gate gradually opens around the "horizontal axis" to release water; On the contrary, as the upstream water level drops, the gate gradually closes to store water, keeping the upstream water level within the design requirements. For example, the roller link type flap gate is a type of gate with double pivot points and connecting rods, consisting of panels, legs, piers, rollers, connecting rods, and other components. It automatically controls the opening and closing of the gate based on hydraulic action according to changes in the gate water level. When the upstream flow rate increases, the water level upstream of the gate rises, and the moment of the dynamic water pressure on the fulcrum is greater than the moment of the gate weight and various damping on the fulcrum, the gate automatically opens to a certain inclination angle until the moment of the dynamic water pressure on the fulcrum is equal to the moment of the gate weight fulcrum at that inclination angle, reaching a new equilibrium at that flow rate. When the flow rate remains unchanged, the opening angle also remains unchanged. When the upstream flow rate decreases to a certain extent, causing the moment of the gate weight on the fulcrum to be greater than the moment of the dynamic water pressure and various damping on the fulcrum, the hydraulic self-control flap gate can automatically close to a certain inclination angle, thereby achieving a new equilibrium at that flow rate.
development history
The hydraulic self controlled flap gate is an energy-saving and environmentally friendly gate developed by Chinese hydraulic engineering technicians after more than 40 years of hard work and possessing completely independent intellectual property rights. Since the birth of the first generation of hydraulic automatic control flap gate in the early 1960s, it has gone through four stages of development: horizontal double hinged type, multi hinged type, roller linkage type, and sliding block type hydraulic automatic control type. Since 1982, the third-generation roller link gate has been widely used. Especially since 1990, a large number of engineering and technical personnel have diligently studied and repeatedly experimented, from theory to hydraulic model experiments, and then to engineering practice. In recent years, they have finally designed and developed the fourth generation of new sliding block flap gate. The gate has made a qualitative leap in terms of technical design, production process, and performance.
From a technical perspective, there have been several significant advancements in the development of flap gates:
(1) Double pivot roller linkage gate with vertical water flow direction designed in early 1982:

Vertical water blocking flap gate

This type of flap gate adopts a double pivot with connecting rod method, which can basically meet the engineering needs during actual operation. However, it cannot be denied that this type of gate still has some shortcomings, mainly due to the easy occurrence of small opening vibration and tapping under certain hydraulic conditions. Although it does not affect the safety of the entire gate dam in the short term, long-term small opening vibration tapping can cause fatigue damage to the bottom of the flap gate and the fixed dam, resulting in serious water leakage of the gate dam and even causing damage to the entire flap gate dam project. In addition, the initial startup water level is high, while the closing water level is low, which makes it difficult to meet the user's usage requirements.
(2) The roller link gate with a certain pre tilt angle towards the downstream of the panel designed in the second half of 1983:
The following improvements have been made to address the issues with the vertical roller linkage gate of the panel:
a) The flap gate has been improved to a type that tilts downstream at an angle. After multiple hydraulic model tests, it has been found that it can effectively prevent the small opening vibration and tapping phenomenon of the flap gate, and lower the initial opening water level and increase the closing water level;

Pre tilt link roller gate

b) There is a sloping drop at the top of the gate weir, which transforms the weir type from a wide top weir to a practical trapezoidal cross-section weir, increasing the flow coefficient and reducing the upstream flood level compared to other forms of flap gates, thereby reducing inundation losses;
c) Multiple modifications and adjustments have been made to the length of the connecting rod, the position of the hinge, and the diameter of the roller, resulting in more accurate and reliable operation. Moreover, the opening water level of the flap gate can be designed to be any value within 5-30cm higher than the normal water level according to the owner's requirements. The difference between the design result and the actual water level used can be controlled within 5cm, usually only one or two centimeters;
d) Add protective piers in front of the gate, which can effectively prevent upstream objects from hitting the gate and floating objects from blocking the gate hinge and causing damage.
After nearly 40 years of operation in nearly 30 provinces and cities across the country, it has been proven that the roller link type flap gate with pre tilt angle panel is quite mature and reliable, and has the value of wide promotion and application.