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1

Stirling engines - the state of technology development and computational models

Furmanek Mariusz, Kropiwnicki Jacek

Combustion Engines

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2022

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R. 61, nr 1

3--12

EN

Stirling engines represent a technologically important solution in combined heat and power systems. Their use enables the achievement of over 90 percent efficiency in the management of the primary energy source with a very high durability of the device, mainly due to the lack of contact of the working gas with external factors and a very small number of mechanical components. The use of a Stirling engine may be equally important when applying renewable energy sources or waste heat from other processes. The first part of the work presents an overview of available commercial Stirling engine solutions. The second part of the work presents an overview of numerical models of Stirling engine operation, which enable the correct selection of the main geometrical features of the devices and the improvement of the structure in order to maximize efficiency or power.

2

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.

3

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.

4

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.

5

Energy costs savings by use of micro - CHP units in domestic households

Błasiński T., Kaźmierczak A., Krakowian K., Cienciała M.

Journal of KONES

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2013

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Vol. 20, No. 3

41--46

EN

Prices of thermal and electric energy delivered to households are constantly increasing, and it will probably not change over the next few years. Due to this fact, people had been forced to find different ways to reduce costs of buying energy. The paper contains description of the most popular systems which are already in use from many years and some innovative systems which are implemented now, or which may be probably installed in nearly future – for example: internal combustion engines, Stirling engines, proton exchange membrane fuel cells, gas turbines, engines with Rankine cycle, etc. Each of mentioned above appliances is necessary to create CHP system which advantages and disadvantages are also described. In this publication, the most promising units have been compared to show their performance, flexibility, profitability and range of using ability. In this paper, approximate money and energy savings that may occur by using modern solutions compared to traditional systems are also shown. As always, during design and development of this kind of devices, there are a lot of problems related to various issues. Main problems and potential solutions have been also presented in this article. In summary further research, directions are suggested due to improve performance of this kind of systems.

6

Konstrukcje i zastosowania współczesnych silników Stirlinga

Kropiwnicki J.

Combustion Engines

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2013

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R. 52, nr 3

243--249

PL

W pracy omówione zostały przyczyny rosnącego zainteresowania komercyjnego wykorzystania silników Stirlinga. Scharakteryzowane zostały podstawowe typy silników Stirlinga ze względu na układ przestrzeni roboczej i cylindrów. W pracy przedstawione zostały przykłady współczesnych konstrukcji tych silników, dokonano również analizy aktualnych i planowanych zastosowań silników Stirlinga. Omówiono podstawowe zalety i wady wykorzystania silników Stirlinga w różnych dziedzinach techniki.

EN

The reasons for the growing interest in commercial use of Stirling engines have been discussed in this paper. Basic types of Stirling engines due to the workspace and cylinders configuration have been presented. The paper includes examples of contemporary designs of these engines, also an analysis of current and future applications of Stirling engines. The basic advantages and disadvantages of the use of Stirling engines in various fields of technology have been presented.

7

Possibilities of applications of stirling engine in cogeneration systems

Boruta G., Drogosz P., Nitkiewicz S., Piętak A.

Journal of KONES

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2012

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Vol. 19, No. 2

67-75

EN

This study takes into account engines working in Stirling cycles in cogeneration systems. Stirling engines have been selected because of their characteristics of exploitation. The possibility of their use in cogeneration systems is more favourable in comparison with other combustion engines because they can avoid usage of industrial and transport fuels. The Stirling engines enable the use of biomass, agricultural and other waste energy sources in micro tri- and cogeneration plants dedicated for the use in agriculture and forestry. Considering such applications, three types of usage structures of Stirling engines are proposed. All three structures are dedicated to install in small residential or farm buildings. These three types of structure are named: “type master”, “type slave” and “type customer”. In accordance with the proposed structures, different types of engine constructions are discussed, too. At the same time, the authors described the dependences between Stirling engines and electric power energy systems. The arguments of grid power systems and dispersed energy resource in text were reviewed. After that overview, some legal problems are discussed. Finally, the conception of independent dispersed micro agropower system and some technical equipment were described. Technical realization of the proposed conception requires: proper type, installation and usage of Stirling engines and proper expectations of achieved results.

8

The selection of stirling engines applied to cogeneration systems

Drogosz P., Nitkiewicz S., Piętak A.

Journal of KONES

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2011

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Vol. 18, No. 4

85-90

EN

The cogeneration systems of energy production are built and developed to achieve the highest economic and ecologic efficiency. These two aims can be realized by increasing energetic efficiency of transforming different sources of energy into technical systems and optimizing usage of own energy. These can be achieved by the usage of different equipment. The search for new constructions, structure and systems is still developing. This article describes the basic principles for use of Stirling engines in micro immobility cogeneration systems. This attempt is made because the Stirling engines seem to be a convenient equipment of optimizing usage of own energy in micro agropower plants. Especially we try to determine which type of the Stirling engine seems to be the best to fulfil the demands in practice. For this purpose a procedure of selection and adjustment of Stirling engines was formulated. In the described procedure many steps ought to be taken for correct choice of all technical arrangements. In this paper the following topics were considered: energetic demands of small houses, maximum instantaneous electric power, consumption of electric energy throughout a year, maximum instantaneous heating power, consumption of heat energy of the year, selection and choice of construction of Stirling engines, selection and choice of pressure of working gas.

9

Estimation of the possibility of Stirling engine applications in LNG carrier power systems

Zmuda A.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2010

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nr 21 (93)

98-104

EN

The article presents a preliminary estimation of the possibility of using Stirling engines in power and waste heat utilization systems of LNG carriers. Flexibility of applying heat sources, very silent operation and very low exhaust gas emission are to the advantage of applying Stirling engines in marine power plants. Unquestionably, one strong point of Stirling engines is the fact that various heat sources can be used to feed them, including waste heat generated by the main and auxiliary engines and burning boil-off gas (evaporated cargo), which is especially important in the LNG carrier power systems. The discussed issues include gas demand by the main propulsion of LNG carriers together with the amount of boil-off, main propulsion power and electric power demand of LNG carriers of various sizes. Finally, an example system for waste heat utilization and reduction of toxic exhaust gases emission of the employing a Stirling engine is described.

PL

Artykuł przedstawia wstępną ocenę możliwości zastosowania silników Stirlinga w układach energetycznych i w systemach utylizacji ciepła odpadowego gazowców LNG. Elastyczność w możliwości zastosowania źródeł ciepła, bardzo cicha praca oraz bardzo niska emisja szkodliwych składników spalin stwarza duże możliwości zastosowania silników Stirlinga w elektrowniach okrętowych. Niewątpliwą zaletą silników Stirlinga jest fakt, że do ich zasilania można wykorzystać różnorodne źródła ciepła, w tym ciepło odpadowe generowane przez silniki główne i pomocnicze oraz spalanie odparowanego ładunku, co jest istotne szczególnie w układach energetycznych gazowców LNG. Przedstawiono m.in. zapotrzebowanie na ilość gazu do napędu głównego gazowców LNG na tle ilości odparowanego ładunku, moc napędu głównego i zapotrzebowanie na energię elektryczną dla różnej wielkości gazowców LNG oraz przykład systemu do utylizacji ciepła odpadowego i ograniczenia emisji składników toksycznych spalin wylotowych silników okrętowych z wykorzystaniem silnika Stirlinga.