Zbigniew Kozanecki

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.

Integrated Diagnostics of the Rotating System with an Active Magnetic Bearing

Nowadays rotating systems are equipped with diagnostic systems that are based on collecting and recording measurement data and that process a huge amount of data during the machine operation. An analysis of these data and their interpretation, as well as finding a correlation between process parameters and dynamics of the machine is a very important problem. In the paper, a concept of the integrated diagnostics of the rotating system with an active magnetic bearing is presented.

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.

Technical and Aerodynamical Aspects of a High Pressure Synthesis Gas Turbocompressor Modernization

The article is devoted to the description of the modernization of a multihull process centrifugal compressor for synthesis gas. The main reason for the revamp was the desire to adapt the conventional machine (45 years of operation) for newer operational requirements: the decrease of compressor discharge pressure to the level of 140 bar from the level of 211 bar with the corresponding alteration of the mass flow rate. The scheme accepted as a final modernization conception required the manufacturing of three completely new rotor and casing assemblies. Major design modifications concerned the impellers’ geometry, introduction of vaneless diffusers and the abradable labyrinth seals. Most of the stages were “optimized” using the in-house semi-empirical 1D code and ANSYS CFX commercial code. The performance of a single optimized stage was tested experimentally. The paper reveals the main results of these measurements and their comparison to numerical simulations results. The start-up tests of the modernized assembly showed its almost 100% conformity to the requirements in the output and the efficiency rise of about 5%.

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.

Technical aspects of a large size industrialprocess turbo compressor revamp

Abstract This paper describes several modernization aspects of the process 8 MW air compressor and its driver. The main aim of the revamp was to increase internal efficiencies of both the compressor and turbine and increase the load of the compressor without additional power consumption. The original pressure ratio was preserved. To meet these requirements a redesign of the flow path of both machineswas necessary.Moreover, the turbineworking conditions were changed from extraction-condensing to condensing. In terms of compressor, impeller blade redesign, adaptation of diffusers and Abradable seals were a part of the scope. The revamp was completed in April 2014 with all the requirements met. This paper covers the general outline and a comparison of the original and modernized machine operating parameters, design and technical assumptions and also describes some problematic issues which occurred during the realization of the project.

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.

Monitoring and Diagnostics of the Rotating System with an Active Magnetic Bearing

In the paper, a concept and selected procedures of the specialized software using advanced information technology for the diagnostic system dedicated for systems of rotating machines with active magnetic bearings will be presented. It is used in the actual operation of the machine, enabling an increase of its reliability. The paper presents some selected results of control of the proper operation of the mechatronic rotating system, carried out in the automatic mode.

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.