Wyniki wyszukiwania - BazTech

1

The Szymkowiak’s over-expanded cycle in the rocker engine with the variable compression ratio - kinematics

Szwaja Stanisław, Szymkowiak Mirosław

Combustion Engines

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2022

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R. 61, nr 2

68--72

EN

The article discusses the innovative concept of the over-expanded thermodynamic cycle, the author of which is the Polish engineer-designer Mirosław Szymkowiak. This cycle is realized on the basis of a new and innovative, previously unknown design, of a piston-crankshaft linkage mechanism with the aid of an additional element known as a rocker arm. Additionally, the proposed mechanism allows for a smooth change of the compression/expansion ratio of the engine during its operation. In the beginning, the earlier conceptions of the rocker engine developed by Szymkowiak were presented, and then the main construction assumptions and kinematic calculations were described. It was confirmed, that the developed linkage has big potential in improving the engine's thermal efficiency by approximately 12% relative. Additionally, it significantly reduces the exhaust gas pressure, when the exhaust valve is opened, therefore, contributes to the reduction of the noise emitted by the engine.

2

Modelling of the over-expanded cycle combustion engine

Jamrozik A., Tutak W., Grab-Rogaliński K.

Journal of KONES

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2018

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Vol. 25, No. 3

237--245

EN

The study concerns numerical tests of an internal combustion engine operating according to the over-expanded cycle carried out in the AVL Fire software. The research covered the modelling of a full working cycle of a conventional engine operating in accordance with the classic Otto cycle and an engine operating on the basis of an over-expanded cycle – the Atkinson cycle. As part of the work, three cases of Atkinson’s cycle were analysed, by closing the inlet valve before BDC (21º before BDC) and closing the valve after BDC (41º and 75º after BDC). As a result of modelling, space-time distributions of velocity, pressure and temperature in the cylinder of the modelled engine were obtained. Optimizations of the analysed cycles were carried out, finding the best ignition timing, at which it is possible to obtain the highest efficiency and the highest indicated mean effective pressure. The calculations showed that the engine operating according to the over-expanded cycle in order to obtain the best operating parameters requires earlier ignition timing compared to the conventional engine. In addition, in the engine operating according to the Atkinson cycle, there is a drop in the indicated mean effective pressure and an increase in the indicated thermal efficiency compared to the engine operating by the classical cycle.

3

Influence of intake valve closure angle on IC engine indicated parameters

Grab-Rogaliński K., Szwaja S.

Journal of KONES

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2015

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Vol. 22, No. 3

29--35

EN

The paper presents results of modelling study of influence of an intake valve closure angle on IC engine indicated parameters. The modelled engine was Andoria S231, which was working on methane. At first, optimizations of the model were done by comparison of the indicated mean effective pressure for real engine and modelled engine. Next, modelling was done for early intake valve closure angle in comparison to original closure angle. The engine was simulated as a naturally aspirated one and for the cases such indicated; parameters as indicated efficiency, mean indicated pressure, fuel consumption were calculated. During the modelling ignition, timing and air-fuel ratio were fixed. For better comparison for two cases of early intake valve closure angle the engine was modelled as super-charged one where mean indicated pressure was fixed at the same level as for the naturally aspirated engine working with original valve timing and indicated parameters were calculated and compared with in parameters determined from this naturally aspirated engine. Because of the calculations, characteristics of indicated parameters vs. intake valve closure angle were computed. As a result of this research, both the decrease in indicated efficiency, indicated mean effective pressure were shown, temperature of fresh charge, end of compression stroke and maximum in-cylinder temperature were observed for naturally aspirated engine with early intake valve closure angle.