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1

Modelling and analysis of rotating systems with gas foil bearings under transient operating conditions

Żywica G., Bogulicz M., Bagiński P.

Tribologia

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2017

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nr 2

167--173

EN

Gas foil bearings are on the cutting edge of bearing systems that spread worldwide. Although it is a common practice to apply such systems to high-speed fluid-flow machinery, their modelling and analysis still pose a number of problems. This article describes the methodology used to assess dynamic properties of a rotor-bearings system supported by foil bearings. Particularly close attention has been paid to the system operation in a transitional state during which a gaseous lubricating film is formed. The conception for the description of the rotor support characteristics was implemented in a computer program that is still under development. The approach that has been taken makes it possible to analyse the system properties throughout a whole range of rotational speeds. Another approach used in the past enabled for analyses of the dynamic performance of rotors, but only on the condition that bearing operation is correct (i.e. only fluid friction in bearing is present). The new model allows for much broader analyses of bearings operation, as confirmed by the obtained results. The article discusses exemplary results of analyses and shows a way one can assess the dynamic properties of rotating machinery equipped with foil bearings even when analysed under transient operating conditions.

PL

Gazowe łożyska foliowe są innowacyjną i coraz częściej stosowaną metodą łożyskowania wysokoobrotowych wirników, ale ich modelowanie i analiza wciąż sprawia wiele trudności. W niniejszym artykule przedstawiono koncepcję ciągłego opisu właściwości dynamicznych wirnika podpartego na łożyskach foliowych. Szczególną uwagę poświęcono pracy układu w obszarze stanu przejściowego, gdy gazowy film smarny zaczyna się tworzyć. Opracowana koncepcja opisu charakterystyk podparcia wirnika została zaimplementowana w rozwijanym programie komputerowym, co umożliwia analizę właściwości układu w pełnym zakresie prędkości obrotowych. Wcześniej stosowane podejście pozwalało na analizę właściwości dynamicznych wirników tylko pod warunkiem poprawnej pracy łożyska, tzn. w obszarze tarcia płynnego. Opracowany model ma znacznie szersze zastosowanie, co zostało potwierdzone w przeprowadzonych badaniach. W artykule przedstawiono przykładowe wyniki analiz pozwalających na ocenę właściwości dynamicznych układów wirujących z łożyskami foliowymi także w stanach przejściowych.

2

Experimental research on gas foil bearings with polymer coating at an elevated temperature

Żywica G., Bagiński P., Andrearczyk A.

Tribologia

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2016

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nr 3

217--227

EN

As demand for high-performance fluid-flow machines (including micro-turbines) increases across the globe, new non-conventional bearing systems are needed. In the last years, specialized technical solutions involving the use of gas foil bearings have been progressively introduced. The application of carefully selected, thin foils as key parts of foil bearings ensures stable operation of the rotor, which is supported by such bearings, even at very high rotational speeds. The article discusses the tests performed on the foil bearings incorporating a friction relieving polymer coating. The research was conducted on an advanced test rig allowing the experiments to be run at high speeds and elevated temperatures, which is in conditions that are typical for micro-turbine operation. The measurements of bearing components’ temperature and vibration levels were carried out at various rotational speeds. The tested bearings were also assessed from the point of view of wear and durability. Conducted research demonstrated that the carefully selected materials that were used to manufacture foil bearings’ key components have successfully contributed to achieving reliable operation within a wide range of rotational speeds, providing very good dynamic properties for the rotor.

PL

W artykule omówiono badania eksperymentalne łożysk foliowych ze specjalną powłoką polimerową zmniejszającą tarcie. Powłoką polimerową została pokryta jedna strona foli ślizgowej, która współpracuje z czopem. Badania zostały wykonane na specjalistycznym stanowisku badawczym umożliwiającym prowadzenie eksperymentów przy wysokich prędkościach w podwyższonej temperaturze, a więc w warunkach typowych dla mikro-turbin. Podczas badań prowadzono pomiar temperatury elementów łożyska oraz drgań czopa przy różnych prędkościach obrotowych. Badane łożyska foliowe były również oceniane pod kątem zużycia i trwałości. Przeprowadzone badania wykazały, że przy odpowiednio dobranych materiałach łożyska foliowe mogą pracować przy minimalnym zużyciu, zapewniając bardzo dobre właściwości dynamiczne wirnika w szerokim zakresie prędkości obrotowych.

3

Prototype of the domestic CHP ORC energy system

Kicinski J., Zywica G.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2016

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Vol. 64, nr 2

417--424

EN

The Institute of Fluid-Flow Machinery (IMP PAN) in Gdansk pursues its own research in fields such as technologies that use renewable energy sources efficiently, including in particular the small-scale combined heat and power (CHP) systems. This article discusses the design concepts for the prototype of small CHP ORC (organic Rankine cycle) energy system, developed under the research project. The source of heat is a boiler designed for biomass combustion. Electricity was generated using specially designed oil-free vapour micro-turbine. The turbo-generator has compact structure and hermetical casing thanks to the use of gas bearings lubricated by working medium. All energy system components are controlled and continuously monitored by a coherent automation and control system. The article also discusses selected experimental results conducted under laboratory conditions. Thermal-flow tests were presented that allow for an assessment of the operation of energy system components. Additionally, energy performance results of the turbo-generator were given including power obtained at various cycle parameters. The achieved results have shown that the developed energy system operated in accordance with design solutions. Electricity derived from the energy system prototype was around 2 kW, with boiler’s thermal power of 25 kW. The research has also confirmed that this system can be used in a domestic environment.

4

Analiza obiegów kogeneracyjnych z silnikami tłokowymi i mikroturbinami

Cieśliński A., Kosowski K., Piwowarski M., Stępień R., Włodarski W.

Rynek Energii

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2015

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Nr 6

41--46

PL

Przeprowadzono analizę dla układów kogeneracyjnych z mikroturbinami wykorzystującymi ciepło odpadowe z silników tłokowych. Rozważono cztery główne źródła ciepła odpadowego z silników tłokowych: spaliny wylotowe, woda chłodząca silnik, olej smarny i ciepło z systemu turbodaładowania. Obliczenia przeprowadzono dla silników General Electric Jerbacher typów: J320 GS-C25 i J416 GS-B05. Uwzględniono różne czynniki robocze siłowni (zarówno “suche”, jak i “mokre”) oraz różne cycle termodynamiczne. Nasze badanie wykazały, że wykorzystując ciepło odpadowe silników, można nie tylko podgrzewać wodę, ale także wytwarzać energię elektryczną. W ten sposób można podnieść sprawność ogólną wytwarzania energii elektrycznej nawet o 20%.

EN

The analysis was carried out for Combined Heat and Power generation systems with micro-turbines power plants working on heat rejected from the reciprocating engine. There are four main sources of heat rejected from the stroke engines: exhaust gases, engine cooling water, lubricating oil and intercooler. The calculations were performed for GE Jerbacher engines of J320 GS-C25 and J416 GS-B05 types. We considered different working media (both wet and dry fluids) and different thermodynamic cycles. Our results proved that using the heat rejected from the engines is possible not only to warm up water but also to produce some electric power and, in this way, increase the total electric output by even 20%.

5

The laboratory test stand of the ORC micro power plant

Breńkacz Ł., Bykuć S., Żywica G., Kaczmarczyk T., Bagiński P.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2014

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nr 146

47--56

EN

The article presents the design and implementation of the laboratory test stand of the micro power plant with an Organic Rankine Cycle (ORC). The test stand was created to research different constructions of micro-turbines operating on a low-boiling agent. The electric power of these micro-turbines is 2-3 [kW]. There are measuring sensors connected to the test stand, which are necessary to collect information about the work of the whole ORC system. This laboratory test stand was built in the Szewalski Institute of Fluid Flow Machinery in Gdansk. The research on the newly constructed test stand were performed and some of the results are shown in this article.

6

The Dynamic Performance Analysis of the Foil Bearing Struture

Żywica G.

Acta Mechanica et Automatica

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2013

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Vol. 7, no. 1

58-62

EN

Foil bearings are a variety of slide bearings in which an additional set of foils is applied between journal and bush, in order to improve the selected static and dynamic properties. Engineers and researchers from all over the world investigate bearings of this type since many years - both from numerical as well as experimental point of view. Due to the complexity of construction, the reliable simulation models are all the time being searched for. This paper discusses the important stages of elaboration of the structural supporting layer numerical model of the foil bearing as well as results of verification tests. The main goal of the conducted study was assessment of reliability of the elaborated numerical model, in scope of dynamic properties. In the near future it will be used for elaboration of the numerical model of the entire foil bearing, which will take into account also phenomena in fluid-film layer. Those models will be used together to describe bearing system in operation.

7

New method of analysis of dynamic state of power micro-devices

Kiciński J.

Mechanics and Mechanical Engineering

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2011

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Vol. 15, nr 3

259-271

EN

Main energy conversion machinery used and to be used in cogeneration systems are schematically described. Some assets of distributed generation are pointed out and small-scale cogeneration systems designed for energy units of distributed cogeneration are described. In the small scale, turbines and bearings are a source of specific problems connected with securing stable rotor operation. Accepted has been two kind of high speed microturbines of electric power about 3 KW with multistage axial and radial rotors supported on foil bearings. A concept which becomes more and more attractive takes into account low-boiling agent, which is normally used in the thermal cycle of the microturbine, as a lubricating liquid in the bearings (so called ORC based systems). The scope of the present article is limited to the discussion of dynamic characteristics of the selected design. The properties of the rotor combined with slide bearings (foil bearings in this particular ease) were taken under investigation. A combination of this type is a certain novelty, since a typical modal analysis of such objects refers to a rotor itself. Analysing the dynamic state of the "home" power plants requires qualitatively novel research tools. It turned out that the situation, in that the rotor - after losing its stability - stabilizes again when the rotational speed increases, is possible. This is a phenomenon determined by the author as multiple whirls.

8

Cogeneration in Small Scale - High Speed Microturbines Dynamic Analysis

Kiciński J.

Archives of Acoustics

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2010

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Vol. 35, No. 2

175-182

EN

Main energy conversion machinery used and to be used in cogeneration systems are schematically described. Some assets of the distributed generation are pointed out and small-scale cogeneration systems designed for energy units of distributed cogeneration are described. In the small scale, turbines and bearings are a source of specific problems connected with securing stable rotor operation. Accepted has been two kinds of high speed micro-turbines of electric power about 3 KW with multistage axial and radial rotors supported on foil bearings. A concept which becomes more and more attractive takes into account a low-boiling agent, which is normally used in the thermal cycle of the micro-turbine, as the lubricating liquid in the bearings (so-called ORC based systems). Of some importance is the operation of these machines at a low noise emission level, sine being parts of the household equipment they could disturb the calm of the residents. The scope of the present article is limited to the discussion of dynamic characteristics of the selected design. The properties of the rotor combined with slide bearings (foil bearings in this particular case) were taken under investigation. A combination of this type is a certain novelty since a typical modal analysis of such objects refers to a rotor itself. Analysing the dynamic state of the "home" power plants requires qualitatively novel research tools.