A novel rotating piston-type compressor is presented. The conventional rolling piston architecture was redesigned to allow oil-free operation. The spring activated vane was replaced by a directly driven swinging vane to provide constant contact to the rotating piston. The model of the compressor was implemented in the AMESim simulation platform. Experiments were conducted on prototypes and the data were evaluated based on the simulation results. Directly unobservable geometric dimensions were estimated by adjusting the mathematical model parameters to the measured thermodynamic state variables with the use of a multi-parametric genetic algorithm. The simple genetic algorithm proved fast and adequate solutions. According to the collected results, the oil-free rotating piston architecture is significantly more sensitive to the sealing clearances compared to the conventional oil lubricated rolling piston compressors. Therefore, the theoretically estimated performance can only be achieved with extremely small manufacturing tolerances, which has to be maintained during the operation.

A new type of thermodynamic machine was designed and prepared for testing to evaluate its capability in extracting mechanical energy from low enthalpy heat sources. The system was completed with a newly designed rotary piston compressor and expander to improve efficiency. A numerical model was set up using commercially available CFD code ANSYS Fluent to evaluate the performance of the compressor and to identify the fluid dynamic related loss sources. In attempt to increase computational efficiency 3D and 2D computations were compared to find the simplest model which provides sufficient information to capture the important heat transfer and fluid mechanical features.

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Rolling piston compressors are small capacity volumetric machines used mainly in household refrigerator and heat-pump units. One of the main characteristics of the compressor is the way how the pressure builds up within the cylinder. This information can be used in more complex models for further investigations, e.g. to analyse the mechanical and thermal stresses of the compressor components. Modelling methods to resemble the pressurisation process of the rolling piston compressor with non-linear oscillators is presented in this paper. The mathematical description of the non-linear oscillators can be used to produce a continuous signal resembling the pressure fluctuations within the cylinder. For the definition of the necessary functions, the main characteristics of the typical rolling piston pressurisation diagram were identified. At first the pressurisation process was approximated by using the mathematical formula of the common Van der Pol oscillator. The oscillator was modified and extended with a linear second order differential equation to improve the resemblance between the target and model functions. To achieve better agreement with the target diagrams, Morphed non-linear oscillators were established. Polynomial and constructive incremental learning method was used to achieve adequate data fitting and the results of both methods were compared. The results show acceptable conformity and proved to be adequate to provide input data for further investigations i.e. for parametric studies of the compressor design. Besides modelling rolling piston compressors, this method can be applied for other volumetric compressors with cyclic pressurization sequence.

Electrostatic precipitator (ESP) models have improved signicantly in the past years. The dramatic development of the capacity of computers made it possible to increase the complexity of ESP models. Recently the dierent interactions between the gas, the electric eld with ion space charge and the charged particles to be precipitated can be described more accurately by the newly developed complex approach. However even some of the newest computer models are limited; they are not able to follow the interactions of the complicated physical phenomena properly. For example pulse energisation of short time impulses cannot be described correctly with models assuming continuous corona current. There is another important problem, namely the examined duration of operation. Some of the models determine the trajectories of dust particles assuming that they are unchanged during the operation of an ESP. The validity of this assumption is very limited in such cases, where the development of certain phenomena is time dependent (e.g. back corona formation). In this paper the authors focus on the "long term" models, analysing such situations in which it is vital to investigate a longer period of operation of ESP-s. Using the newly developed model the eect of back corona, rapping, etc. can be analysed with higher reliability than it has been performed in previous ESP models.