Experimental and Numerical Study of Swirling ... - Solid Mechanics
Experimental and Numerical Study of Swirling ... - Solid Mechanics Experimental and Numerical Study of Swirling ... - Solid Mechanics
Experi imental and Numerical N Stud dy of Swirling g Flow in Scaveenging Processs for 2-Stroke Marin ne Diesel Engin nes Fig gure 5.8: Tan ngential Velocity for f Inta ake port 75% Clo osed. Chapter 5 At z in n figure 5.9, the jet-like pprofile of axiaal velocity hass a sharp peaak 1 compare ed to 50% int take port clossure in figure 5.7. The maggnitude of axiial velocity has increased d further. Withh port coveredd by 75%, theere is very smaall opening g at the inlet port. p The pistoon outer wall diverts the floow to enter thhe cylinder r through the e small openiing. The floww enters the ccylinder with a strong axial a compone ent at the inleet and it is verry likely to havve a fluid jet iin the near r wall region. At posit tion z , the axi ial velocity proofile changes to wake-like. This indicates 2 a vortex x breakdown like l characteriistic between the two meassuring positionns z and z where the vortex core wwith a jet-like upstream pprofile becomes 1 2 unstable e and the core e flow underggoes a shock-likke transition (Escudier et al., 1982). This T characteri istic is oppositte to the one oobserved at z for 25% closeed 6 ports where w a wake-l like axial veloocity profile, aalong the floww downstreamm, changed d to a jet li ike. At 75% intake port t closure, unnfortunately nno measure ements have been b taken in the cylinder ccross-sections in between thhe two mea asuring positio ons z and z wwhere a changge in the axial velocity profiile 1 2 occurs. Therefore, the type of the vortex breakddown (spiral, bubble shapeed etc.) in this experime ent cannot bee found out. Physically, dduring the PIIV experim ment for 75% piston p closuree, the glycerinn tracer particcle started to bbe deposite ed on the cylin nder internal wwalls close to the intake porrt (Figure 5.100). That req quired cleanin ng the internall walls after shhort intervals bbecause the raate of deposition was fast and otherwiise could not make it possible to take PIIV measure ements. For a real engine sccavenging, succh a phenomeenon can resuult in cond densation of certain exhauust gas speciees (high heat loads) on thhe cylinder r liner wall close c to scaveenge ports. HHowever, due to presence oof dynamic c effects of pis ston motion aand stratificatiion etc. it cannnot be said that if such vortex break kdown is haappening duriing real engine scavenginng process. 116 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 Figu ure 5.9: Axial Velocity V for Intak ke port 75 5% Closed. Figu ure 5.10: Glyceri in particles deposit tion on internal cylinde er wall. For pos sitions z to z , the V 3 6 z ccontinues to exhibit a waake-like profille, however r, the peak val lues are observved at large raadial positions indicating that the core e radius has increased to be mmore than r/RR= 0.8. Trace partticles depositionn on internal wwalls Chapter 5 In gene eral, for a give en port closurre and measurring position, the normalizeed tangent tial and axial velocity profiles are nearly the same for both Reynolds number rs ReA and Re eB. Small variaations in maggnitude are obbserved at somme radial positions p for a given measuriing position. 117 Effect of Piston Position
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Experi imental <strong>and</strong> <strong>Numerical</strong> N Stud dy <strong>of</strong> <strong>Swirling</strong> g Flow in Scaveenging<br />
Processs<br />
for 2-Stroke<br />
Marin ne Diesel Engin nes<br />
Figu ure 5.9:<br />
Axial Velocity V for Intak ke<br />
port 75 5% Closed.<br />
Figu ure 5.10:<br />
Glyceri in particles<br />
deposit tion on internal<br />
cylinde er wall.<br />
For pos sitions z to z , the V 3 6 z ccontinues<br />
to exhibit a waake-like<br />
pr<strong>of</strong>ille,<br />
however r, the peak val lues are observved<br />
at large raadial<br />
positions indicating that<br />
the core e radius has increased<br />
to be mmore<br />
than r/RR=<br />
0.8.<br />
Trace partticles<br />
depositionn<br />
on<br />
internal wwalls<br />
Chapter 5<br />
In gene eral, for a give en port closurre<br />
<strong>and</strong> measurring<br />
position, the normalizeed<br />
tangent tial <strong>and</strong> axial velocity pr<strong>of</strong>iles<br />
are nearly the same for both Reynolds<br />
number rs ReA <strong>and</strong> Re eB. Small variaations<br />
in maggnitude<br />
are obbserved<br />
at somme<br />
radial positions p for a given measuriing<br />
position.<br />
117<br />
Effect <strong>of</strong> Piston Position
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