Numerical Solutions for Two- and Three-Dimensional Non-Reacting Flowfields in an Internal Combustion Engine
Numerical Solutions for Two- and Three-Dimensional Non-Reacting Flowfields in an Internal Combustion Engine
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Date
1977
Authors
Griffin, Michael Douglas
Advisor
Anderson, John D. Jr
Jones, Everett
Jones, Everett
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DRUM DOI
Abstract
The numerical solution for the flowfield established in a spark-
ignition internal combustion engine during the four-stroke (intake,
compression, power, exhaust) cycle is considered. Only fluid-dynamic
effects are treated with combustion simulated by constant- volume heat
addition near top-dead-center on the compression stroke. The working
fluid is assumed to be air of constant specific heat, with both viscous
and inviscid models considered. Two- and three-dimensional engine models
are examined, with the three-dimensional models including both rectangular
and cylindrical geometries. The difficulties associated with obtaining
numerical solutions in cylindrical coordinates for three-dimensional
non-axisymmetric problems when the centerline is included in the region
of interest are discussed. A new method which avoids the coordinate-
singularity problems associated with such cases is presented and used
to obtain the first known four-stroke inviscid-flow solution for a
three- dimensional cylindrical engine model. Similar results are presented
for a three-dimensional rectangular model, and for the first known
two-dimensional four-stroke calculation for a viscous fluid. The inviscid
three-dimensional results are compared with each other and with
previously obtained two-dimensional inviscid-flow calculations. The use
of two-dimensional models is found to be justified for the non- reacting
flowfields considered, since the results obtained from a two-dimensional
calculation in the valve plane are apparently not strongly dependent on
the flowfield perpendicular to the valve plane. It is found that significant
flowfields do exist in all I.C. engine models considered. It is
shown that the unit-cell-Reynolds-number criterion limits viscous flow
calculations to Reynolds numbers of approximately one ten-thousandth
the realistic value, and that this produces flowfields which are strongly
piston-dominated. In contrast, inviscid results show marked circulatory
patterns, which are more realistic. The velocity patterns which develop
in the three-dimensional cylindrical engine model are shown to exhibit
a marked swirl in planes parallel and perpendicular to the cylinder
axis.