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From Beale Number to Pole Placement Design of a Free Piston Stirling Engine

Zare S., Tavakolpour-Saleh A., Omidvar A.

Archive of Mechanical Engineering

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2017

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Vol. LXIV, nr 4

499--518

EN

In this paper, pole placement-based design and analysis of a free piston Stirling engine (FPSE) is presented and compared to the well-defined Beale number design technique. First, dynamic and thermodynamic equations governing the engine system are extracted. Then, linear dynamics of the free piston Stirling engine are studied using dynamic systems theory tools such as root locus. Accordingly, the effects of variations of design parameters such as mass of pistons, stiffness of springs, and frictional damping on the locations of dominant closed-loop poles are investigated. The design procedure is thus conducted to place the dominant poles of the dynamic system at desired locations on the s-plane so that the unstable dynamics, which is the required criterion for energy generation, is achieved. Next, the closed-loop poles are selected based on a desired frequency so that a periodical system is found. Consequently, the design parameters, including mass and spring stiffness for both power and displacer pistons, are obtained. Finally, the engine power is calculated through the proposed control-based analysis and the result is compared to those of the experimental work and the Beale number approach. The outcomes of this work clearly reveal the effectiveness of the control-based design technique of FPSEs compared to the well-known approaches such as Beale number.

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Gas-condensate banking and well deliverability : a comparative study using analytical- and numerical models

Ursin J. R.

AGH Drilling, Oil, Gas

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2016

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Vol. 33, no. 2

259--289

EN

Reservoir condensate blockage in the reservoir and in particular in the close vicinity of the wellbore may result in significant loss of well deliverability for medium to tight gas reservoirs. The dynamics of fluid flow in these types of reservoirs are investigated by way of analytical description and by numerical simulation of radial two phase flow behavior. The analytical model is based on a single phase semi steady-state solution, being revised for two phase flow of gas and condensate oil. As the liquid is dropping out of the gas, a saturation distribution of immovable oil is seen to develop radially in the reservoir with time. Condensed oil not being part of this saturation distribution is produced to the surface. The numerical model is a cylindrical, single well, fine gridded, simulation model run on the Eclipse E300 compositional simulator. The base case study comprises a rich gas condensate fluid (GOR ~ 1000 Sm3/Sm3), an initial gas-in-place volume of 750 MSm3, and reservoir permeability of 10 mD. A gas flow rate of 0.5 MSm3/day is leading to a production period of about 4 years. A comparative study is performed by varying parameters such as pressure development, development of bank of immovable oil both radially and as function of time, condensate blockage effects, and gas and condensate oil production and onset of reduced well deliverability. Sensitivity analysis are performed by studying variation in the productivity index, non-Darcy and mechanical skin, and sensitivities related to permeability. It has been confirmed in this study that condensate blockage has a direct and negative impact on well deliverability, where both the plateau period and the bottom hole pressure are reduced. We also show that the analytical model compares well with the numerical models and that many features describing gas-condensate banking and well deliverability are adequately described in the model. The analytical model also offers insight into the process of reservoir liquid storage in gas condensate reservoirs.

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Wyniki rozwoju Abaqus w analizie dużych zadań liniowej dynamiki

Kąkol W.

Górnictwo Odkrywkowe

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2010

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R. 51, nr 3

270-272

PL

W artykule przedstawiono najnowsze wyniki rozwoju programu Abaqus w realizacji dużych zadań z dynamiki liniowej. Zwrócono szczególną uwagę na postęp w ulepszaniu solwera AMS, który pozwala w niezwykle efektywny sposób na wyznaczanie dużej liczby wartości częstotliwości i postaci drgań własnych dla dużych i bardzo dużych modeli. Uznane procedury rozwiązywania zadań nieliniowych znajdują zastosowanie w zadaniach liniowej dynamiki, dla których istotny jest stan przed wyznaczaniem odpowiedzi dynamicznej (pre-loading). Pokazano istotne różnice dla takich zadań, z i bez uwzględnienia tych efektów.

EN

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