A Magnetic Levitation Turbine Generator for Downhole Electronic Devices

Abstract

Abstract Stable and reliable power supply is essential for downhole electronic devices to fully function. A downhole generator can transform the available ambient energy in the downhole environment into electricity, which is an ideal way of downhole power supply. Turbine generators have proven useful in many different environments, but they have drawbacks such as large start-up flow rate, low energy conversion rate and short life expectancy that make them unsuitable for harsh downhole environments. This paper presents a new method for the long-term energy supply of downhole electronic devices by using a magnetic levitation turbine generator. In this scheme, a turbine is used to convert the continuous wellbore flow into electricity and a permanent magnetic bearing is employed so that the turbine can float in the current, thus completely eliminating contact friction and allowing free rotation of the turbine, which then lead to a reduced start-up flow rate. The design of magnetic levitation structure also solves the contradiction between dynamic sealing and efficient rotation, thus achieving efficient energy conversion under different working conditions. An experimental prototype was fabricated and tested in a closed cycle pipeline using water as the medium. The experimental results showed that the turbines can rotate smoothly at high speed and the magnetic levitation structure showed relatively high stability. At a flow rate of 20-45m3/d, the output power was 0.5-13W. With a rectifier circuit, such a generator can meet the requirements of charging the downhole electronic devices. This magnetic levitation turbine generator has the advantages of simple structure, high conversion efficiency, easy processing and high feasibility. It is expected to offer an intriguing alternative for long-term downhole power supply, which is an important prerequisite for a wide range of future production systems and applications.