Drainage device and system for controlling discharging of concentrated water in water purification process

A drainage device, comprising:

• a valve cavity, a flowmeter, a transmission shaft, and a control unit, wherein:
• an inner cavity wall of the valve cavity is provided with an inner shoulder, and the inner shoulder divides the inner cavity of the valve cavity into a first cavity and a second cavity which are communicated;
• the first cavity is provided with a first water inlet hole penetrating through the cavity wall;
• the second cavity is provided with a first water outlet hole penetrating through the cavity wall and a first shaft hole, and the first shaft hole is a cylindrical hole, and arranged on an opposite face of a communication port between the first cavity and the second cavity;
• the flowmeter is arranged in a space formed by the first cavity and the second cavity, and comprises a first cylinder, a first baffle, a first flow hole, and a second flow hole;
• the first baffle forms an outer shoulder of the flowmeter;
• and the outer shoulder is matched, and hermetically, movably and fixedly connected with the inner shoulder of the first cavity;
• the first cylinder penetrates through the first baffle, an inner cavity of the first cylinder is in a cylindrical shape, and the cylindrical shape is coaxial with the first shaft hole;
• the first cylinder comprises a first portion and a second portion;
• the first portion extends into the first cavity, and a side wall of the first portion is provided with a through first flow hole;
• and the second portion extends into the second cavity, an opening of the second portion faces the first shaft hole, and a side wall of the second portion is provided with a through second flow hole;
• and
• the transmission shaft is a cylinder, which passes through the first shaft hole and the first cylinder, and is hermetically and movably connected with the first shaft hole and the first cylinder, one end of the transmission shaft entering the first cylinder is provided with a diversion portion, and the other end of the transmission shaft extending from the first shaft hole outside the valve cavity is matched with the control unit to control a motion of the transmission shaft, so that the diversion portion is matched with the first flow hole and the second flow hole to control a liquid flow, so as to divert the liquid from the first cavity to the second cavity.