Aiming at the difficulty in designing the internal spray system inside the telescopic cut-off head of coal mine machinery, this study proposes a mechanical seal switching principle based on the permanent magnetic eddy current effect, which realizes the switching and sealing between the cylinder’s expansion state (without rotation) and the internal spray condition (with rotation). This work can solve the current problem that the inner spray cannot be arranged inside the external rotor structure mining equipment. Firstly, the mechanical seals of the two working conditions are designed, and the requirements for the torque and axial force of the permanent magnet eddy current structure are proposed, and the sealing conditions and mutual switching conditions of the cylinder working condition and spray working condition are revealed. Secondly, the mathematical description of the eddy current magnetic field of the permanent magnet eddy current valve is established, and the calculation equations of the torque and axial force of the permanent magnet eddy current transmission are proposed, and a calculate study is carried out by using the finite element method, and the calculation results show that in the low-slip region, the analysis of the electromagnetic torque and axial force characteristics of the permanent magnet eddy current and the finite element results are in good agreement. Finally, example simulations show that the permanent magnet eddy current switch can realize the sealing and its switching between the two operating conditions as desired, and can realize the low leakage operation.

Fracturing truck is an important part of all electric drive shale gas stimulation system. As the main bearing structure of fracturing truck, the frame bears complex loads, and its fatigue life determines reliability of the system. Taking the frame of 7000hp full electric drive fracturing truck as the research object, this paper establishes the finite element simulation model of the frame, determines the load spectrum of the frame, analyzes the transient stress of the frame, and then calculates the fatigue life of the frame by using S-N curve analysis method and fatigue cumulative damage theory.

To address the problem of problematic spray design inside mining anchor-digging equipment, a switching seal using a permanent magnet eddy current drive is initially presented here. The layer model of the permanent magnet eddy current structure is established, the subdomain analysis model is introduced, the permanent magnet eddy current structure is divided into six regions along the axial direction, and the boundary equations are established at the interfaces of each region. The vector magnetic potential equations in each region are deduced, along with the electromagnetic torque and axial force equations. The computational results are compared and analyzed with the results of finite element simulation, verifying the accuracy of the theoretical model. The design of experiments is used to verify the feasibility of the switching seal using the permanent magnet eddy current structure.