Comparative analysis of the results of numerical and physical experiments on study of gas-lubricated radial bearing properties

Статья посвящена увеличению несущей способности опор с газовой смазкой. Рассматриваются результаты физического эксперимента, выполненного для подтверждения адекватности теоретических результатов, получаемых с помощью численного эксперимента, который основан на математической модели. Приводятся описание экспериментального стенда и методика проведения эксперимента. Результаты представлены в виде кривых, отображающих зависимость эксцентриситета оси вала (цапфа) от давления наддува.

Analytical and Modelling Study on the Spatial Stress Distribution and Failure Process of Disc Specimen in the Brazilian Splitting Test

To correctly obtain the spatial stress distribution and failure process of disc specimen in the Brazilian splitting test, an analytical solution of three-dimensional stress is deduced. Then, the effects of height-diameter ratio and clamp radian on the spatial stress distribution and failure process are analyzed and studied combined with numerical modelling. At last, the influence of spatial effect on the tensile strength of disc specimen is discussed. The results show that the cracks firstly generate at the two ends of the specimen in the axial direction and then extend due to the nonuniform distribution of tensile stress. The macrocracks coalescence does not mean the capacity loss of radial bearing. The maximum radial bearing capacity of the disc specimen decreases with the increase of height-diameter ratio due to the spatial effect. The tensile strength obtained by the two-dimensional calculation formula is significantly smaller. Therefore, when the commonly-used height-diameter ratio of 0.5 is used in the Brazilian splitting test, a correction factor k = 1.15 − 1.25 is suggested.

Development of a Passive Magnetic Radial Bearing System for Electric Submersible Pumps ESPs

This development is the result of a DeepStar program to build and test a new radial passive magnetic bearing system (PMB) for downhole tools. While slated for the Magnetic Drive System (MDS) ESP, an advanced high-speed ESP that uses magnetic fields to increase performance, reliability and retrievability, this technology is applicable to conventional ESPs. The PMB supports the motor rotor across large clearances with no physical contact via magnetic fields in the ESP. An MDS ESP preliminary design was developed, from which the size and integration requirements of the PMB were defined. These requirements guided the analysis, design and testing of the full-scale components. Empirical analysis tools were used for initial iterations in size and performance of the PMB, followed by detailed magnetic finite element analysis (FEA) using commercial validated tools for the final performance prediction. With analytical validation of performance, detail designs were developed and hardware fabricated. Hardware testing was done to validate performance predictions and alignment with system requirements. The feasibility, preliminary design and analysis of the PMB were conducted in Phase 1 of the DeepStar Program and has continued with the full-scale design, build and test results of Phase 2. PMB performance results include load capability and deflection during static load events, all in relation to validating performance for use in the MDS system. This test data is used to validate the analysis approach used as well as to finalize the integration size of the PMB to meet the performance requirements of the MDS system. With the PMB large (>14mm) clearance between rotor and stator magnets, testing also includes variations in axial and radial position of the rotor in relation to the stator to account for installation variations in the MDS as well as use of sealing materials on both the rotor and stator. Integration is planned for use of the PMB in the MDS, so integration testing is planned to validate performance for each of these areas. This technology offers a radial bearing that can greatly enhance ESP performance and reliability. The PMB is a contact-less bearing system that does not require lubrication, can operate with large clearances to allow free fluid flow, is easily fully sealed from the environment, has virtually no bearing rotating losses, and has no operating life limits.

Research on combination of passive magnetic bearing and mechanical bearing for vertical axis wind turbine

Aiming at the “light wind start, light wind power generation” of vertical axis wind turbine, a new T-shaped radial passive magnetic bearing with high suspension characteristics is proposed. Passive magnetic bearings used in vertical axis wind turbines usually have small bearing capacity and difficult magnetization. The new T-shaped radial PMB can improve the radial bearing capacity, and the three magnetic rings all adopt simple axial magnetization. The new T-shaped radial PMB is combined with mechanical auxiliary bearing to form the suspension system of wind turbine. In the stable state, the suspension system can realize radial and axial stable suspension. The structure and working principle of the suspension system are briefly described. Through the finite element simulation, the characteristics of the new T-shaped radial PMB, the traditional double-ring PMB and the T-shaped PMBs are compared. Taking the high bearing capacity and high stiffness of the new T-shaped radial PMB as the optimization objective, the multi-objective optimization of the new T-shaped radial PMB was carried out by changing its geometric parameters (inner diameter, magnetization length and air gap). The research results show that: Under the same bearing capacity, the volume of the new T-shaped radial PMB is reduced by about 78.64%. Under the same volume, its bearing capacity increased by about 30.7%, and its stiffness increased by about 96.1%. After optimization, its radial bearing capacity increased to 101.38 N, and its stiffness increased to 202.76 N/mm.