Experimental and Numerical Study of Swirling ... - Solid Mechanics

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Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke Marine Diesel Engines ændring begynder dog ved tværsnit tæt på cylinderudløbet, og flytter til opstrømspositioner. Ved 50% porttildækning, antager den gennemsnitlige aksiale hastighed i hele cylinderen en jet-lignende profil. Den tangentiale hastighed ligner mere en væg-jet end et tvungent hvirvelprofil. Ved 75% porttildækning, ændres den jet-lignende aksielle hastighedsprofil ved tværsnittet tæt på indtagsporten tilbage til et slipstrømslignende profil ved det tilstødende tværsnit og videre nedstrøms. Dette indikerer en strømning som ligner et ’’vortex breakdown’’ Den tangentielle hastighed har derefter tvungent hvirvelprofil. De ikke-dimensionelle profiler af hastighedskomponenterne har ingen betydelig ændring med variationen i Reynolds tal. Numeriske simuleringer udføres kun for de tilfælde hvor indtagsportene er helt åbne. Turbulensmodellerne inkluderer RNG k og Reynolds stress modeller. Resultaterne af simulationerne viser dog ikke tilfredsstillende overenstemmelse med de eksperimentelle data. Simuleringerne viser en større hvirvel kerne størrelse for en tilbagestrømning. Henfaldet af rotation nedstrøms er mindre end hvad der blev observeret eksperimentelt. Men der er nogle kvalitative egenskaber såsom distribution af modelberegnede Reynolds stress komponenter, der til en vis grad, stemmer overens. De faktorer, der påvirker resultaterne af CFD modellerne ligger muligvis både i behandlingen af turbulens og de numeriske aspekter.
Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke Marine Diesel Engines Preface This dissertation is submitted in partial fulfillment of the requirement for the degree of Doctor of Philosophy in Mechanical Engineering. The dissertation is based on the research work carried out during the period from 2006 to 2010 at the Technical University of Denmark (DTU). The work was carried out under the supervision of Associate Professor Knud Erik Meyer, Associate Professor Jesper Schramm and Assistant Professor Dalibor Cavar along with useful suggestions from Professor Valery Okulov and PhD Stefan Mayer Manager Basic Research at MAN Diesel & Turbo. The dissertation consists of six chapters excluding the conclusions and appendices. Bibliography is given after the summary and conclusions. Chapter 1 gives and introduction to the scavenging process in two stroke marine diesel engines and identifies the scope of the work. Chapter 2 provides a brief overview of swirling flows based on theoretical and experimental work from scientific literature. Chapter 3 gives a description of the experimental test model used in this research work. Chapter 4 presents the results of the first stereoscopic PIV experiment where the length of the cylinder is changed. Chapter 5 gives the results from second experiment where the measurements are conducted at different intake port closures while keeping the cylinder length constant. Chapter 6 provides the description and results of the numerical simulations carried out. Finally the Summary and conclusions will summarize the results of the research work and point out the potential future work. Due to limited space, all the results from the experiments in Chapter 4 & 5 could not be given in the respective chapters and are instead given in Appendix A & B respectively. Appendix C includes the manuscript of the article ready to be submitted to a related scientific journal.
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DTU Mechanical Engineering Section
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