Jakub Łagodziński

Theoretical and Experimental Investigations of Oil-Free Bearings and their Application in Diagnostics of High-Speed Turbomachinery

In order to reduce the risk of failures, the optimal design selection from the viewpoint of machine reliability must be conducted. Therefore, one should analyze thoroughly the dynamics of the rotor-bearing-casing system in the whole operating range of the machine. The rotating system presented in the paper is supported in non-conventional bearings. The actual study consists in the investigation of new coating materials in the bearing design and the improvement in rotating system dynamics to increase the total efficiency, maintain the cleanness of the working medium and ensure operation of bearings in wide temperature ranges. Despite many advantages, air-foil bearings meet problems of friction and wear in critical moments of their operation, furthermore their complete theoretical model is difficult to establish. Different modeling theories of such bearing dynamic characteristics are shortly described. The current tendency in numerical and experimental methods for diagnostics of rotor support systems of low power rotating machinery is outlined.

Magnetic Thrust Bearing for the ORC High – Speed Microturbine

The paper is devoted to the FEM modeling of a magnetic thrust bearing for the small power, high-speed microturbine, working in the Organic Rankine Cycle. The microturbine is used to produce electricity in small dissipated power generation systems.

Oil-free bearing development for high-speed turbomachinery in distributed energy systems – dynamic and environmental evaluation

Abstract Modern distributed energy systems, which are used to provide an alternative to or an enhancement of traditional electric power systems, require small size highspeed rotor turbomachinery to be developed. The existing conventional oil-lubricated bearings reveal performance limits at high revolutions as far as stability and power loss of the bearing are concerned. Non-conventional, oil-free bearings lubricated with the machine working medium could be a remedy to this issue. This approach includes a correct design of the machine flow structure and an accurate selection of the bearing type. Chosen aspects of the theoretical and experimental investigations of oil-free bearings and supports; including magnetic, tilting pad, pressurized aerostatic and hydrostatic bearings as well as some applications of oil-free bearing technology for highspeed turbomachinery; are described in the paper.

Application of a compliant foil bearing for the thrust force estimation in the single stage radial blower

Abstract The paper presents the application of a compliant foil bearing for estimation of the thrust force in a single stage radial blower under operational conditions. The bump foil of the thrust bearing behaves as a nonlinear spring. The knowledge of the spring deflection curve allows estimation of the actual thrust force for a measured bump deflection at the given rotational speed. To acquire the deflection curve, static calibration of the axial shaft displacement sensor was performed. During the calibration, the information about voltage signals of the sensor for the given loading force was collected. The measured voltage values at different speeds and loadswere then converted into the thrust force. The results were verified by comparison to the thrust force resulting from the pressure distribution on the impeller.

Model of Kinetic Energy Recuperation System for City Buses

Energy consumption is a significant issue for public transport providers, because of the relatively high mass of the vehicles and the huge amounts of energy used to overcome inertial forces. In city buses, the kinetic braking energy is usually transformed into waste heat. In this paper, we propose a system to enable the recovery of braking energy in city buses, using a Kinetic Energy Recuperation System (KERS). The main assumptions of the system were elaborated in a Matlab/Simulink model of city bus dynamics, based on the real driving cycles of buses in Lodz (Poland). The following components were modelled: the flywheel supported in an active magnetic bearing, two reverse electric motors, the high ratio gears and the control system. The main objective of the control system was to balance operation of the braking and drive systems with optimal usage of the flywheel system. The charging and discharging phases of the KERS were analysed, as well as the energy stored. Fuel consumption savings were calculated via a comparison with normal city bus driving cycles without KERS. This model could be a very useful tool for research into city bus dynamics with KERS systems, providing a wide range of operational parameters for city bus powertrains.

A Self-Acting Gas Journal Bearing with a Flexibly Supported Foil — Numerical Model of Bearing Dynamics

The work is devoted to an analysis of the journal bearing dynamics, while factors related to motion and friction of nonrotating elements of the sleeve are taken into account. Based on the originally established numerical model devoted to bearing static simulations, the thickness of gas film was determined as well as the pressure distribution in the bearing and its lift capacity. Moreover, the numerical program developed for dynamic simulations led to an analysis of forced vibrations of the system under consideration. It was possible to visualize a journal trajectory for the dynamic harmonic input function. The relationship between the frequency of excitation force and bearing stiffness has been identified numerically and compared with the experimental results. The Fast Fourier Transform (FFT) analysis of vibrations was implemented. In the spectrum, only a frequency of the input function was observed, whereas and a lack of subsynchronous frequencies pointed to the stable operation of the bearing. The established numerical model yields the basis for simulations carried out in order to determine correctly dynamic characteristics of an oil-free machine rotating system at the early stage of its design and during its operation.

Influence of Intermediate Foil on Air-Foil Bearings Performance and Exploitation Properties

Air-foil technology is an interesting substitute for classic rolling or oil bearings in turbomachinery. It ensures low power losses, and does not require external lubrication or pressurization and is capable of working with high rotational speeds. Numerous studies brought significant improvement in materials and design solutions for the aerodynamic shaft support system. The paper presents effects of modification performed by adding intermediate foil to typical structure of air-foil bearing. The main aim of the investigation was focused on analyze of its influence on characteristic parameters and exploitation properties of operating bearing, i.e., bearing load capacity and bearing resistance to thermal runaway phenomenon (DellaCorte in Design, Fabrication and performance of open source generation I and II compliant hydrodynamic gas foil bearings 2008). The thermal runaway is also known as foil bearing thermal instability. The tests confirmed proper behavior of the modified device and brought new knowledge in the air-foil technology field of knowledge.

Solenoid Actuator for a Camless Control System of the Piston Engine Valve

Simulation and experimental results of a camless valve control system for the piston engine are presented. The valve is designed to be used as a bleed valve for an additional energy recuperation system. The use of electromagnetic and not mechanical actuator follows from the need to close and open the valve on demand. The electromagnetic valve control allows for valve opening and closing independently of the engine cycle.

Estimation of External Forces in the Rotating System with an Active Magnetic Suspension

A method for estimating external forces acting on a rotating machine system with an additional active magnetic support is described. The verification of the method was carried out on the test stand. The force exerted with an impedance hammer and the effect of its action was compared to the estimated results of the magnetic reaction forces determined with the module of the diagnostic software. Obtained results of the investigations have confirmed the usefulness of the proposed method, which leads to finding the right diagnostic balance between the symptom and the cause and securing a rotating system from damage.