Shenyang Getai Hydropower Equipment Co., Ltd.

Causes of Cavitation in Turbine Runner Chamber and Repair Technology

Jan. 21, 2020

Water turbine is a power machine that converts the energy of water flow into rotating mechanical energy. It belongs to turbine machinery in fluid machinery. The turbine part of the bulb tubular turbine unit consists of a runner room, Guide Vane mechanism, runner, and tailpipe. The generator shaft is directly connected to the runner and is installed on the steel bulb housing. The wheel is at the rear end of the bulb. The generator bearing is fixed on the bulb housing through a bearing support ring. The runner end bearing is fixed on the bulb end housing. The front end of the generator shaft is connected to the motor slip ring and the oil circuit device of the rotor pitch control . The steel light bulb is fixed in the concrete foundation through the upper and lower pillars, and the upper pillar is also a passage for people to enter and exit the bulb. After the water flow enters, it evenly passes around the bulb to reach the runner, and the runner is driven to rotate to do work and then discharged from the tailpipe. It is suitable for low-head large and medium-sized hydropower stations.

Guide Vane

Guide Vane

The runner chamber refers to the connection between the bottom ring and the draft tube in the axial flow and diagonal flow turbine to form a hydraulic channel, and to form a proper gap with the outer edge of the runner blade. The runner room is prone to cavitation problems during operation, and there are hidden dangers that threaten the safe and stable operation of the power plant. What causes cavitation in the turbine runner chamber? How should we respond? Let the Hydraulic Turbine Generator Supplier tell everyone about it.

1. What causes cavitation in the turbine runner chamber?

The runner and blade of the hydropower station are made of stainless steel, and the main material of the runner chamber is Q235, which has poor toughness and anti-cavitation performance. Due to the limited amount of water stored in the reservoir and long-term operation at ultra-high design heads, a large amount of air bubbles appeared in the tail water. During operation, the pressure of the water flow in the turbine flow process was lower than the vaporization pressure zone, and the water passing through the blade gap was evaporated Boiling produces vapor bubbles, generates local impact pressure, and produces periodic impact and water hammer pressure on the metal, subjecting the metal surface to repeated impact loads, causing material damage and causing metal crystals to cavitate and fall off. Cavitation occurs repeatedly in the runner chamber with the blades in and out of the water. Therefore, under long-time super-high head operation, cavitation gradually occurs and deepens continuously.

2. How to fix the cavitation problem in the turbine runner chamber?

Case of cavitation in the turbine runner chamber: Since the turbine chamber of a hydropower station's cross-flow turbine unit has been put into operation, the cavitation problem has occurred in the runner chamber at the inlet and outlet sides of the same blade, forming a width of 200mm and a depth of 1-6m. The unequal cavities show cavitation bands all around the perimeter, especially in the upper part of the runner chamber. The cavitation depth is 10-20mm.

Technology and process of cavitation repair in the turbine runner chamber: With the excellent performance of the material and targeted repair process, Soleil carbon nano-polymer material repair technology has achieved good application results in the cavitation repair of the turbine runner chamber. The whole repair process is also relatively simple: dismantling the runner room, checking the cavitation situation in the runner room-surface degreasing treatment, shaving off the cavitation layer with carbon arc gouging, removing loose metal layers-sandblasting and rusting on the surface- -Special primer for brushing--Sorley carbon nano-polymer material is blended to the proportion, and the material is applied to the part to be repaired, and it is scraped along with the reference ruler. The material is cured, and the repair size can be checked to complete the repair.

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