Wyniki wyszukiwania - BazTech

1

On the internal efficienty of a turbine stage: classical and computational fuid dynamics definitions

Nastałek L., Karcz M., Sławiński D., Zakrzewski W., Ziółkowski P., Szyrejko C., Topolski J., Werner B., Badur J.

Transactions of the Institute of Fluid-Flow Machinery

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2012

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nr 124

17--39

EN

Almost entire fleet of steam turbines in Poland was designed between 1950_1980 with the use of the so-called zero-dimensional (0D) calculation tools. For several years, design and modernization of the turbines occur in assistance with the state-of-the-art methods that describe working fluid flow field based on three-dimensional (3D) models and computational fluid dynamics (CFD) codes. This cooperation between 0D and 3D codes requires exchange of overall, integral information such as: power, efficiency, heat and mass fluxes. In consequence the question arises regarding the cohesion of definitions, and particularly regarding the correctness of the definition for internal efficiency of the turbine's stage and the turbine as a whole. In the present paper we formulate basic definitions reason of efficiency that are naturally adapted to the numerical 0D and 3D models. We show that the main reason of differences between the definitions in 0D and 3D is the definition of the theoretical work of the stage lt. In the classical 0D models, mostly employed is the isentropic approach, and hence the isentropic efficiency occurs. Meanwhile, in the increasingly common 3D approach (most likely by CFD), we use more physically correct pathway by subtracting energy loss from the available energy, that leads to the polytropic definition of efficiency. We show an example of computing the efficiency and the 3D losses, denoted with additional subscript CFD, we also discuss benefits of this definition in comparison with the isentropic classical definition in 0D.

2

Power augmentation of PGE Gorzow’s gas turbine by steam injection – thermodynamic overview

Ziółkowski P., Lemański M., Badur J., Nastałek L.

Rynek Energii

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2012

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Nr 1

161--167

EN

The impact of steam injection upon a gas turbine and a combined power plant performance has been investigated. This article describes and summarizes possibilities of modification for current gas turbine in PGE Gorzow power plant into the Cheng cycle. Our modification deals with a thermal cycle, in which steam produced in a heat recovery steam generator is injected into the gas turbine’s combustion chamber. It has been proved that an increase of the mass flow rate of the expanded exhaust gases causes an increase in both the power and efficiency of gas turbine. Steam injection also helps to reduce NOx formation and is profitable from a thermodynamic, economic and ecological standpoint. The numerical analysis of thermal cycles, before and after the modification, has been carried out by means of an in-house COM-GAS code and Aspen Plus commercial package.

PL

W artykule zbadano wpływ wtrysk pary wodnej na wydajność turbiny gazowej i obiegu gazowo-parowego. Artykuł opisuje i podsumowuje możliwości zmodyfikowania turbiny gazowej elektrociepłowni PGE Gorzów do obiegu Chenga. Modyfikacja związana jest z obiegiem cieplnym, w którym produkowana para w kotle utylizacyjnym wtryskiwana jest do komory spalania turbiny gazowej. Udowodniono, że wzrost strumienia masy ekspandujących spalin powoduje wzrost mocy i sprawności turbiny gazowej. Dodatkowo, wtrysk pary wodnej powoduje obniżenie tlenków azotu NOx i z punktu widzenia termodynamicznego, ekonomicznego i ekologicznego jest zabiegiem korzystnym. Obliczenia numeryczne obiegu cieplnego przed i po modyfikacji wykonano za pomocą własnego kodu COM – GAS oraz komercyjnego programu Aspen Plus.

3

Modeling of Baumann’s turbine stage operation. Part I - Flow

Zakrzewski W., Nastałek L., Badur J., Jesionek K., Straś K., Masłyk M.

Archiwum Energetyki

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2012

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T. 42, nr 2

175--183

EN

A Baumann stage is one of the way, to increase the turbine’s output without an increase of the last stage blade length. Due to the complicated design, the Baumann’s blade technology is complex, and its efficiency is lower in comparison to a free-standing blade. Currently that stage is used mostly in back pressure cogeneration heating turbines. This paper presents the operation of low pressure part steam turbine in different conditions, calculated with two models of steam and compared to measurements and TURBINA 0D code.

PL

W pracy nawiązano do stopnia Baumanna i całej części niskoprężnej turbiny kondensacyjnej typu 13K215, w której występują różnice między pomiarami a danymi projektowymi określonymi na podstawie klasycznych narzędzi obliczeniowych typu „0D TURBINA”. Dlatego celem artykułu jest próba wyjaśnienia tych różnic poprzez, dokładniejszą niż 0D, symulację 3D przepływu kondensującej pary w części niskoprężnej turbiny.

4

Foundations of the Navier-Stokes boundary conditions in fluid mechanics

Badur J., Karcz M., Lemański M., Nastałek L.

Transactions of the Institute of Fluid-Flow Machinery

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2011

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nr 123

3-55

EN

Until recently it was believed that Navier’s boundary condition could be given as a rigorous foundation for slip phenomena. Due to the latest measurements in the mass flow rate of a gas flowing through nano- and microchannels, several discrepancies in the mathematical modelling have been found. Thus, in the literature, the opinion persists for the Navier slip condition to be correct only under certain circumstances, particularly those restricted to the first order boundary conditions. One of many ways to eliminate this discrepancy, which is extensively employed in the contemporary literature, is to develop a variety of the so-called second order boundary conditions. This path, however, seems incorrect since it lacks consistency between the bulk stress tensor and its boundary representation. In the paper we propose to replace the classical Navier slip condition with the new, more general Navier-Stokes slip boundary condition. Instead of the usual method of consideration, the boundary condition is presented as following from the mass and momentum balances within a thin, shell-like moving layer. Owing to this, the problem of consistency between the internal and external friction in a viscous fluid is solved within the framework of new layer balances, and a proper form of constitutive relations for friction and mobility forces. Finally, the common features of the Navier, Stokes, Maxwell and Reynolds concepts of a boundary slip layer are compared and revalorized. The classifications of different mobility mechanisms, important for flows in nano-, microchannels are also discussed.