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Hydraulic resistance analyses of selected elements of the prototype Stirling engine

Furmanek Mariusz, Kropiwnicki Jacek

Archives of Thermodynamics

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2019

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Vol. 40, no 3

123--136

EN

The paper presents the results of simulation tests of hydraulic resistance and temperature distribution of the prototype Stirling alpha engine supplied with waste heat. The following elements were analyzed: heater, regenerator and cooler. The engine uses compressed air as a working gas. Analyses were carried out for three working pressure values and different engine speeds. The work was carried out in order to optimize the configuration of the engine due to the minimization of hydraulic resistance, while maintaining the required thermal capacity of the device. Preliminary tests carried out on the real object allowed to determine boundary and initial conditions for simulation purposes. The simulation assumes that there is no heat exchange between the regenerator and the environment. The solid model used in simulation tests includes the following elements: supply channel, heater, regenerator, cooler, discharge channel. Due to the symmetrical structure of the analyzed elements, simulation tests were carried out using 1/6 of the volume of the system.

2

Analysis of start energy of Stirling engine type alpha

Kropiwnicki Jacek

Archives of Thermodynamics

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2019

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Vol. 40, no 3

243--259

EN

The Stirling engine type alpha is composed of two cylinders (expansion space E and compression space C), regenerator that forms the space between the cylinders and the buffer space (under the pistons). Before the start-up and as a result of long-term operation, the average pressure in the working space (above the pistons) and in the buffer space is the same. However, in the initial phase of operation, the average pressure in the working space is different then the average pressure in the buffer space depending on the crankshaft starting position (starting angle). This, in turn, causes a large variation in the starting torque. An additional unfavorable factor caused by a large variation in the course of the indicated torque is the rotational speed variation and the formation of torsional vibrations in the drive system. After some time, depending on the quality of the engine piston sealing, the average pressure in the working and buffer space will equalize. The occurrence of the above-described phenomenon affects the selection of the starting electric motor, which can be significantly reduced, when the crankshaft starting position is optimized (the starting torque is several times greater than the average torque occurring in the generator operation mode). This paper presents the analysis of the impact of the crankshaft starting position on the course of the indicated torque and the resulting start-up energy. Starting the engine at an unfavorable position of the crankshaft may, in extreme cases, increase the starting torque even three times.

3

Wybrane aspekty projektowania urządzeń pracujących w obiegu Stirlinga

Wrona J.

Rynek Instalacyjny

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2016

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Nr 5

83--88

PL

Maszyny Stirlinga mogą stanowić realną alternatywę dla stosowanych obecnie technologii silników cieplnych oraz urządzeń chłodniczych. Zapomniana, niemal dwustuletnia konstrukcja, która w chwili powstania przerastała możliwości ówczesnej technologii, przeżywa obecnie prawdziwy renesans. Potwierdzają to liczne wdrożenia komercyjne w różnych dziedzinach techniki – od urządzeń chłodniczych po silniki przemysłowe. Perspektywiczne jest wykorzystanie silników Stirlinga w kotłach dla mikrokogeneracji. W tego typu urządzeniach znajdują zastosowanie niewielkie silniki o mocy do kilku kWe. Ze względu na swoje własności silniki Stirlinga mogą stanowić doskonałą alternatywę dla silników ze spalaniem wewnętrznym oraz turbin gazowych.

EN

Stirling machines can be a viable alternative to currently used technologies of heat engines and refrigeration equipment. Forgotten almost two-hundred years old construction, which in its inception surpassed the possibilities of contemporary technology is currently enjoying a renaissance. This is confirmed by the increasing number of commercial deployments in various technical fields from refrigeration to industrial heating engines. Stirling engines shall be employed in cogeneration system boilers. In such boilers only small engines of only several kWe of power may be employed. Because of many favourable attributes Stirling cycle engines possess, they represent an excellent alternative to internal combustion engines and gas turbines.