Intermittent Controllable Magnetically Levitated Turbine Generator System in Water Injection Wells

Abstract To address the critical challenge of sustainable power supply for downhole wireless sensor networks in intelligent oilfields, this study proposes an intermittently controllable magnetically levitated turbine generator system specifically designed for water injection wells. Targeting limitations of conventional turbine generators—including mechanical wear, low-flow-rate sensitivity, and spatial constraints in narrow wellbores—the system integrates three key innovations: (1) A magnetically levitated turbine design where the impeller and rotor are suspended via magnetic coupling, significantly reducing rotational friction and enabling a low startup flow rate of 24.5 m³/d; (2) Intermittent power generation control using an eccentrically positioned flow path selector valve to direct fluid between a central bypass channel and a power generation channel, supporting on-demand operation; (3) Intelligent energy management where a main control chip monitors battery state-of-charge (SOC) and temperature, toggling between bypass mode (SOC >25%) and charging mode (SOC <25%) with Maximum Power Point Tracking (MPPT). Experimental validation on a simulated well platform demonstrated: stable power generation across 25–45 m³/d flow rates, with output voltage and rotation speed exhibiting electromechanical coupling and load-dependent behavior; linear current regulation via PWM control ensuring efficient charging; successful valve-actuated mode switching between generation and bypass states; and continuous charging capability. This system overcomes key limitations of conventional downhole power solutions, providing a reliable, maintenance-free energy source for long-term well monitoring in water injection applications.