Experimental and Numerical Study of Swirling ... - Solid Mechanics
Experimental and Numerical Study of Swirling ... - Solid Mechanics Experimental and Numerical Study of Swirling ... - Solid Mechanics
Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke Marine Diesel Engines Chapter 1 The goal of this study is to study and develop a simplified steady state and isothermal case of in-cylinder swirling flow. The focus is to Characterize the in-cylinder confined swirling flow in the test setup. Obtain experimental data. Study the capability and performance of different turbulence models. Identify key design aspects to develop future test models. 1.7 Thesis Layout This thesis has been divided into three major sections. (1) Introduction and Theory of Swirl Flows: introduce the background of the problem studied and provide a theoretical basis for the analysis of experimental and Numerical results. (2) Experimental Section: describes the experimental setup design and presents and analyses the experimental results. (3) Numerical Section: gives the results of computational fluid dynamics (CFD) models and compares them with experimental results and discusses the performance of different turbulence models for predicting the in-cylinder swirling flow. 10 Introduction
Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke Marine Diesel Engines Chapter 2 Swirling Flows This chapter gives a brief overview of flows having swirling motion. A general classification of different swirling flow regimes have been given based on the tangential velocity profile. Different swirl generation methods have also been presented. Aspects of swirling flows related to current study have been discussed based on experimental results available in the scientific literature. Some of the challenges regarding the numerical modeling of swirling flows with focus on RANS based models are also discussed. According to American Heritage Dictionary of English Language, the word ‘swirl’ means ‘‘to move with a twisting or whirling motion’’. In fluid mechanics the term ‘swirling flow’ can in general be defined as a class of different flow types that involve an ‘overall’ twisting or whirling motion because in many flows localized twisting or whirling motion of fluid exist as a result of mixing or turbulence is observed yet they are not considered as swirling flows. The main characteristic of swirling flows as defined by Baker et al. (1974) and Ito et al. (1986) is that the flow has a combination of tangential/ vortical and axial motions. Thus the presence of ‘vortex’ is an important characteristic of swirling flows. Vanyo (1993) defines a vortex as a mass of fluid whose elements are moving in nearly circular path lines about a common axis. Care must be taken in distinguishing a vortex from vorticity because vorticity is the rotation of infinitesimal fluid elements (Vanyo, 1993). Greitzer et al. (2004) has further characterized the swirling flow as can be having a large variation in static pressure through the vortex core compared to an essentially uniform static pressure across a thin shear layer or boundary layer in a non-swirling flow. In nature, swirling flows can be observed in case of cyclones, dust devils, whirlpools and tornados etc. In engineering applications, the swirling flows exist in many engineering applications both as confined (cyclone separators and swirl tubes, rotary kilns, co-axially rotating cylinders, hydraulic turbine draft tubes etc.) and un-confined (swirling jets in combustors and tornado like flow upstream of the intake of a gas turbine etc.) (Escudier et al. 2006, Lam, 1993). Swirl in the flow enhances heat transfer in heat exchangers, homogenizes mixtures in casting and reactants in chemical industry, and in combustion processes breaks fuel droplets and stabilizes the flame (Cazan et al., 2009). Contrarily, the swirl/ vortices generated in some engineering applications e.g. at the intakes of liquid pumps, draft tubes of hydraulic turbines, weirs and draining of reservoirs etc. are by-product of the fluid motion and can severely affect the main function of the equipment (Lam, 1993). Therefore, swirl and its effect on the flow field containing it is very important to be studied. As discussed in Chapter 1, the in-cylinder flow during scavenging process of large two-stroke diesel engine is also a confined 11 Swirling Flows
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<strong>Experimental</strong> <strong>and</strong> <strong>Numerical</strong> <strong>Study</strong> <strong>of</strong> <strong>Swirling</strong> Flow in Scavenging Process for 2-Stroke<br />
Marine Diesel Engines<br />
Chapter 1<br />
The goal <strong>of</strong> this study is to study <strong>and</strong> develop a simplified steady state <strong>and</strong><br />
isothermal case <strong>of</strong> in-cylinder swirling flow. The focus is to<br />
Characterize the in-cylinder confined swirling flow in the test setup.<br />
Obtain experimental data.<br />
<strong>Study</strong> the capability <strong>and</strong> performance <strong>of</strong> different turbulence<br />
models.<br />
Identify key design aspects to develop future test models.<br />
1.7 Thesis Layout<br />
This thesis has been divided into three major sections.<br />
(1) Introduction <strong>and</strong> Theory <strong>of</strong> Swirl Flows: introduce the background <strong>of</strong> the<br />
problem studied <strong>and</strong> provide a theoretical basis for the analysis <strong>of</strong><br />
experimental <strong>and</strong> <strong>Numerical</strong> results.<br />
(2) <strong>Experimental</strong> Section: describes the experimental setup design <strong>and</strong> presents<br />
<strong>and</strong> analyses the experimental results.<br />
(3) <strong>Numerical</strong> Section: gives the results <strong>of</strong> computational fluid dynamics<br />
(CFD) models <strong>and</strong> compares them with experimental results <strong>and</strong><br />
discusses the performance <strong>of</strong> different turbulence models for predicting<br />
the in-cylinder swirling flow.<br />
10<br />
Introduction
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