Cyclic Variability Measurement in I.C. Engine In-Cylinder Flows Using High Speed PIV

This paper describes the application of a high speed PIV system to the measurement of internal combustion engine in-cylinder flows. The PIV system has a framing rate of 13.5 kHz allowing single pulse multiple frame cross-correlation processing. The framing rate produces a velocity vector map at less than 1 crank angle degree temporal resolution for engine speeds up to 2000 rpm. With instantaneous, whole field vector maps at this temporal resolution and over a sufficient number of engine cycles it is possible to separate the total flow variability into quantitative measures of cyclic variability and per-cycle turbulence. To enable automatic vector processing a novel approach has been developed using the product of correlation functions from the same spatial region in temporally consecutive pairs of frames. This is the temporal equivalent of the original Hart process. A description of the optical system is given and some initial results.