Cycle Resolved Turbulence Measurements in a Ported Engine With and Without Swirl

Abstract

Measurements are presented of mean velocity and of turbulence intensity, energy spectrum, time scales and length scales in a ported engine with flat head and piston, motored at 1200, 1800 and 2400 RPM both with and without swirl. The measurements were made using laser Doppler velocimetry at data rates which were sufficiently high to allow the mean velocity in each cycle to be determined which enables one to separate the cyclic fluctuations of the mean velocity from the turbulence. The turbulence measurements near top dead center both with and without swirl showed relatively homogeneous turbulence intensity and time scales, approximately linear scaling of the turbulence intensity with RPM, decreasing time scales with increasing RPM and a shift in the turbulent energy spectrum to higher frequencies with increasing RPM. With swirl however, 25% to 50% greater turbulence intensity, higher frequency content and smaller cyclic fluctuations in the mean velocity were found.