Comparing the simulated and measured motored-flow kinetic energy in the TCC-III research engine

Paper #:
  • 2018-01-0192

Published:
  • 2018-04-03
Abstract:
A large eddy simulation computed 35 consecutive motored cycles for comparison with PIV velocity measurements in the TCC-III engine. As a most basic comparison, this study focuses on the intracycle evolution and cycle to cycle variability, CCV, of the volume average kinetic energy. One purpose is to assess efficacy of comparing the kinetic energy of the two-component two-dimensional velocity in the restricted regions of the PIV measurements, with the three-component three-dimensional data of the LES. A second is to examine how well this simulation captured the kinetic energy production and dissipation through the motored cycles. The volume-averaged kinetic energy from the three-dimensional three-component LES is sampled from the entire cylinder volume and in slabs. These slabs are volumes with areas and thickness equal to the PIV field-of-view and laser sheet thickness. The differences between samples using different slab thickness and cutting planes are assessed. Also, the differences between the simulated kinetic energy, KE = 0.5U2, specific kinetic energy, ke = U2, and KE = 0.5 ρ ̌U^2 are shown, where  and ρ ̌ are the local and volume averaged densities. The measured and simulated KE dependence on crank angle had the same general trends, but notable differences during the intake stroke in the plane of the intake jet. This particular simulation underestimated both the average and range of KE compared to the measured values during the compression stroke. This was most severe just prior to TDC, where MBT spark timing would have occurred had the engine had been fired. However, the simulated KE in the plane normal to the cylinder axis was overestimated during the motored expansion stroke prior to exhaust valve opening.
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