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To thermodynamical analysis of important thermal cycles
Bayer, Zdeněk
On examples of gas turbine cycles the paper shows the importance of thermodynamic optima definition and deals with possibilities of their formulations. The next part introduces the fundamentals of the combined cycles theory and with help of cycles formed by three reversible processes points out their properties. The last part introduces the fundamentals and results of Nekolný´s analytical thermodynamics of advanced Rankine cycles.
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The alternative thermodynamic analysis of thermal cycles for internal combustion engines: generalized definition of heat supply
Bayer, Zdeněk
An innovative model of the heat supply to the ideal thermal cycles is based on the following principles: a) heat is proportional to the expansion work, b) it is also proportional to the temperature difference between the working fluid and the cylinder wall, and c) the irreversibility of the hermodynamic processes is considered. The principle a) is worked up in detail. The thermodynamic analysis shows some important relations between the cycle parameters and the cycle criteria. The development of the model with regard to the principles b) and c) is undergoing.
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The development of the new type of simple, middle accurate approximations of caloric functions of state of wet steam
Bayer, Zdeněk
The study presents the continuation of the new method of analysis of ideal thermal cycles of the piston combustion engines. The method is based on the following principles: i) use of the temperature ratio of the cycle as the basic thermodynamic parameter, ii) use of the specific performance as an additional criterion (besides the thermal efficiency), and iii) the complex thermodynamic optimization of the cycle. These principles are used to perform the analysis of the cycle in the off-design regimes and the derivation of the most important thermodynamic formulae for the ideal thermal cycle of supercharged engines.
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Some possibilities of analytical description of strong non-adiabatic gas compression
Bayer, Zdeněk
Paper deals with modelling of the gas state- and thermodynamic behaviour in cavitation bubbles. After recent presentation of model M3 based on the more realistic idea of the heat transfer in the course of bubble compression, introduces its advanced version M4. The comparison of the polytropic and M4 model of process shows the results for high volume compression ratios may differ in tenths of percent. In a like range lies the discrepancy caused by using more accurate state equation and temperature dependence of the heat capacity.
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Description of state behavior along the critical isotherm and along the saturation curve using simple equations of state. Part II
Bayer, Zdeněk
The contribution deals with a group of 13 equations of state (EOS), predominantly of the van der Waals type, both classical and also newly developed in the IT AS ČR. In the region from the triple- to the critical points, the changes in the temperature functions (1st criterion), deviations of the derivate from the correct value, (2nd criterion), and the course of the liquid spinodal are investigated. Ordinary water substance is used as the model medium. The data and/or equations following from the critical point and saturation curve conditions are given. The calculations showed that considerable improvements may be arrived at separately applied criteria but at their simultaneous application the improvement has been not gained.
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Description of state behavior along the critical isotherm and along the saturation curve using simple equations of state ů part I
Bayer, Zdeněk
The contribution deals with a group of 13 equations of state (EOS), predominantly of the van der Waals type, both classical and also newly developed in the Institute. In the region from the triple- to the critical points, the changes in the temperature functions (1st criterion), deviations of the derivate (2nd criterion), and the course of the liquid spinodal are investigated. Ordinary water substance is used as the model medium. The possibilities of improving EOS of this type are searched. While at separately applied criteria some improvements were arrived at, the simultaneous application of criteria gave no satisfactory results.
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