Large-eddy simulation of motored flow in a two-valve piston engine

POD analysis and cycle-to-cycle variations

Kai Liu, Daniel C. Haworth, Xiaofeng Yang, Venkatesh Gopalakrishnan

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Large-eddy simulation (LES) has been performed for a single-cylinder, two-valve, four-stroke-cycle piston engine through 70 consecutive motored cycles. Initial comparisons of ensemble-averaged velocity fields have been made between LES and experiment, and proper orthogonal decomposition (POD) has been used to analyze the complex in-cylinder turbulent flows. Convergence of POD modes has been quantified, several POD variants have been explored, and sensitivity of results to analyzing different subsets of engine cycles has been studied. In general, it has been found that conclusions that were drawn earlier from POD analysis of a simplified non-compressing piston-cylinder assembly with a fixed valve carry over to the much more complex flow in this motored four-stroke-cycle engine. For the cases that have been examined, the first POD mode essentially corresponds to the ensemble-averaged mean velocity. The number of engine cycles required to extract converged POD modes increases with mode number, and varies with phase (piston position). There is little change in the lower-order phase-invariant POD modes when as few as 24 phases per cycle (30 between samples) are used, and complex 3-D time-dependent in-cylinder velocity fields through full engine cycles can be reconstructed using a relatively small number of POD modes. Quantification of cycle-to-cycle variations and insight into in-cylinder flow dynamics can be extracted through analysis of phase-invariant POD modes and coefficients.

Original languageEnglish
Pages (from-to)373-403
Number of pages31
JournalFlow, Turbulence and Combustion
Volume91
Issue number2
DOIs
Publication statusPublished - 09-2013

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piston engines
Engine pistons
Large eddy simulation
large eddy simulation
Decomposition
decomposition
cycles
Engine cylinders
engines
Engines
pistons
strokes
Pistons
velocity distribution
turbulent flow
Turbulent flow
set theory
assembly

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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title = "Large-eddy simulation of motored flow in a two-valve piston engine: POD analysis and cycle-to-cycle variations",
abstract = "Large-eddy simulation (LES) has been performed for a single-cylinder, two-valve, four-stroke-cycle piston engine through 70 consecutive motored cycles. Initial comparisons of ensemble-averaged velocity fields have been made between LES and experiment, and proper orthogonal decomposition (POD) has been used to analyze the complex in-cylinder turbulent flows. Convergence of POD modes has been quantified, several POD variants have been explored, and sensitivity of results to analyzing different subsets of engine cycles has been studied. In general, it has been found that conclusions that were drawn earlier from POD analysis of a simplified non-compressing piston-cylinder assembly with a fixed valve carry over to the much more complex flow in this motored four-stroke-cycle engine. For the cases that have been examined, the first POD mode essentially corresponds to the ensemble-averaged mean velocity. The number of engine cycles required to extract converged POD modes increases with mode number, and varies with phase (piston position). There is little change in the lower-order phase-invariant POD modes when as few as 24 phases per cycle (30 between samples) are used, and complex 3-D time-dependent in-cylinder velocity fields through full engine cycles can be reconstructed using a relatively small number of POD modes. Quantification of cycle-to-cycle variations and insight into in-cylinder flow dynamics can be extracted through analysis of phase-invariant POD modes and coefficients.",
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Large-eddy simulation of motored flow in a two-valve piston engine : POD analysis and cycle-to-cycle variations. / Liu, Kai; Haworth, Daniel C.; Yang, Xiaofeng; Gopalakrishnan, Venkatesh.

In: Flow, Turbulence and Combustion, Vol. 91, No. 2, 09.2013, p. 373-403.

Research output: Contribution to journalArticle

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