Cyclic variability measurements of in-cylinder engine flows using high-speed particle image velocimetry

In this paper we present full-field flow measurements for cyclic variability analysis within in-cylinder flows. A high-speed particle image velocimetry system has been developed with a framing rate of 13.5 kHz to allow single pulse multiple frame cross-correlation processing. This framing rate produced velocity vector maps at approximately 1° crank angle temporal resolution for engine speeds up to 2000 rpm. A novel processing scheme employing the temporal product of correlation functions is shown to increase vector validation rates enabling a statistical flow analysis. Velocity data have been obtained over 15 engine cycles for two engine conditions to demonstrate the operation of the instrumentation and processing algorithms. The data obtained show that changing the axial swirl level via the inlet port geometry has a significant effect on the cyclic variability of the flow in the latter half of the compression stroke. The technique allows the acquisition and processing of the flow data within a single working day representing orders of magnitude time and cost savings compared to using single point optical velocimeters. © 2004 IOP Publishing Ltd.