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

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Experi imental and Numerical N Stud dy of Swirling g Flow in Scaveenging Processs for 2-Stroke Marin ne Diesel Engin nes Figure 5.3: Cartoon n of flow at pisto on interfac ce with partially closed cylinder c inlet. Figu ure 5.4: Tange ential Velocity for r Intake e port 25% Closed. Chapter 5 Since th he flow rate is kept constantt, the average the cylin nder will incre ease at the inllet port compa The dec crease in the ra adial velocity wwill result in t vortex core c at positi ion close to the cylinder Reynold ds numbers, th he magnitude of mean tang The pro ofile shows a less l distinct ppeak at the int comparatively bigger vortex core aat z . The 1 origin is different and indica distribu ution. The size of the fo downstr ream and at position p z the 5 solid bo ody rotation. V velocity of thhe flow enterinng ared to when it is fully openn. the increase inn the size of thhe inlet i.e. z . For the giveen 1 gential velocityy has decreased. terface of outeer region and a profile on booth sides of thhe ates asymmettry in tangeential velocity forced vortex increases allong the floow e in-cylinder taangential veloocity changes tto 112 Effect of Piston Position
Experi imental and Numerical N Stud dy of Swirling g Flow in Scaveenging Processs for 2-Stroke Marin ne Diesel Engin nes Fig gure 5.5: Axial Velocity for Inta take port 25% 2 Closed. The axia al velocity at z still has wakke-like profile, , however, thee velocity deficcit 1 in the vo ortex core region has reduceed indicating more mass enntering into that region. The T maximum m value of V has also increeased compareed to fully opeen z intake port. p Between positions z aand z there is a rapid decreease in the axiial 1 2 velocity peak. The di ifference betwween the V mminimum in the vortex corre z and the peak V valu ue outside thee core has alsoo decreased. This differencce z continu ues to reduce e until at z where the wwake-like proofile at z has 6 5 transfor rmed into jet- like profile duue to entrainmment of moree mass into thhe wake re egion. Further r, Escudier et aal. (1982) alsoo observed a siimilar behavioor in one of the experimental resultts, however, wwith a nearly axis-symmetrric swirling g flow. 50% Por rt Closure Chapter 5 With th he piston covering 50% of tthe intake porrt, the shift in the asymmetrry in the distribution of V at z increeases further (FFigure 5.6). Allong positive XXv 1 /R, the profile p is still having h a singlle peak. Howeever, along neggative Xv /R, thhe tangential velocity has h two peakss. One compparatively smaaller peak is at Xv/R=0.2 2 and the oth her larger peakk in the near wwall region. TThis is probabbly due to the t effect of th he cylinder wall. For confinned swirling fflows, the effect of prese ence of wall on o the vortexx is like the eeffect of a ‘mmirror vortex’ as discusse ed in section 2.3.6. 2 In case of helical swirling flows, wwhen the vorteex core pos sition is at a larger l distancee from the cyllinder axis or in other wordds closer to o the cylinder r wall, the effeect of wall willl enhance on the vortex sidde closer to t wall. This picture gets more complicated when we consider a precessing and helical l vortex. At z an nd further do ownstream thee tangential vvelocity profille changes annd 3 attains a solid body li ike profile. In figure 2.1d, thhe profile alsoo resembles too a 113 Effect of Piston Position
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Manuscript J Mar Sci Technol manus
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50 % and 75 % partially closed inta
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V θ / V b V θ / V b V θ / V b 1.
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V θ / V b V θ / V b V θ / V b 1.
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DTU Mechanical Engineering Section
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Experimental and Numerical Study of Swirling ... - Solid Mechanics

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