High Resolution Scalar and Velocity Measurements in an IC Engine

High resolution planar laser-induced fluorescence (PLIF) and particle-image velocimetry (PIV) measurements were acquired during the intake stroke in a motored engine to investigate the mixing behavior of in-cylinder flows. The data were analyzed to determine the scalar energy and kinetic energy spectra, which were used to find the corresponding dissipation spectra. The results were compared to a model turbulent spectrum. The scalar energy and scalar dissipation spectra were shown to be resolved through the full dissipation range, enabling the determination of the Batchelor / Kolmogorov length scale, and agreed well with the model turbulent spectrum at all but the highest wavenumbers where the effects of random noise were present. The 2% point in the scalar dissipation spectra was used to estimate the Batchelor scale, which was found to be approximately 32 μm. The PIV data, which had a 675 μm interrogation region, were used to calculate a one-dimensional kinetic energy spectrum. The kinetic energy spectrum agreed well with the scalar energy spectrum and the model spectrum up to wavenumbers corresponding to approximately 2× the PIV interrogation region size. For the present measurements, this meant that the PIV data were not able to resolve the peak in the dissipation spectrum, i.e. the full high-wavenumber part of the inertial subrange.