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 Figur re 5.37: Normalized Reynolds Shear Stress S at z and 1 Re . A Chapter 5 The exp perimental re esults show thhe complexityy of the incyllinder confineed swirling g flow even without w the ddynamic effecct of a moving piston. Thhe variatio on of both axi ial and especiially the tangeential velocityy with different piston positions p indic cate that in adddition to enggine rpm and sscavenging poort angle, as a studied by Nishimoto N et aal. (1984), thee incylinder floow also changges during a single scave enging cycle. IImproving the performance of scavenginng process thus cannot be b possible byy considering the velocity pprofile averageed over a scavenging cyc cle. Additionall challenge wiill be for the mmodeling task to develop p a model th hat performs better for different regimmes of confineed swirling g flow. The results of thhis experimennt can be a test bench ffor perform mance of different turbulence models in simulating diifferent swirlinng flow. 146 Effect of Piston Position
Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke Marine Diesel Engines Chapter 6 Numerical Modeling This chapter presents the results from the numerical modeling of the swirling flow test case. Unsteady simulations are conducted using two RANS based approaches and the results are compared with the experimental data. The simulations results only represent the case with fully open cylinder intake port and at Reynolds number of 65,000. A discussion has also been made on the possible approaches for improving the simulation results. The results of the numerical models included in this chapter are those obtained until the time of writing this thesis. For mesh generation, Ansys ® GAMBIT v2.4 is used and for CFD processing Ansys ® FLUENT v12.1 is used. The post processing of the numerical data is done in Fieldview ® v 12. The computational domain does not include the guide vanes and the inlet to the domain is defined at a radial distance of 200 mm from the axis of rotation (Figure 6.1). In the experimental setup the inlet to the setup is at a radial distance of 300 mm with guide vanes mounted at 250mm radial distance from the cylinder axis/ axis of rotation (Figure 4.1). This is adopted to avoid the inlet to be in the region with large wake effects behind the guide vanes and also not close to the contraction section. The LDA measurements in section 4.1 show a very small wake effect at this radial distance. Another purpose is to see if it is possible to achieve good results by neglecting the guide vanes region in the computational mesh and defining the magnitude of radial and tangential velocity components at some radial position after the guide vanes region. The computational mesh has Y-axis as its rotational axis, therefore, the velocity component along Y-axis represents the axial component and for velocity component along Z-axis it is vice versa. 147 Numerical Modeling
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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 />
Figur re 5.37:<br />
Normalized<br />
Reynolds<br />
Shear Stress S at z <strong>and</strong> 1<br />
Re . A<br />
Chapter 5<br />
The exp perimental re esults show thhe<br />
complexityy<br />
<strong>of</strong> the incyllinder<br />
confineed<br />
swirling g flow even without w the ddynamic<br />
effecct<br />
<strong>of</strong> a moving<br />
piston. Thhe<br />
variatio on <strong>of</strong> both axi ial <strong>and</strong> especiially<br />
the tangeential<br />
velocityy<br />
with different<br />
piston positions p indic cate that in adddition<br />
to enggine<br />
rpm <strong>and</strong> sscavenging<br />
poort<br />
angle, as a studied by Nishimoto N et aal.<br />
(1984), thee<br />
incylinder floow<br />
also changges<br />
during a single scave enging cycle. IImproving<br />
the<br />
performance<br />
<strong>of</strong> scavenginng<br />
process thus cannot be b possible byy<br />
considering the velocity ppr<strong>of</strong>ile<br />
averageed<br />
over a scavenging<br />
cyc cle. Additionall<br />
challenge wiill<br />
be for the mmodeling<br />
task to<br />
develop p a model th hat performs better for different<br />
regimmes<br />
<strong>of</strong> confineed<br />
swirling g flow. The results <strong>of</strong> thhis<br />
experimennt<br />
can be a test bench ffor<br />
perform mance <strong>of</strong> different<br />
turbulence<br />
models in simulating diifferent<br />
swirlinng<br />
flow.<br />
146<br />
Effect <strong>of</strong> Piston Position
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