Optical studies of turbulence in an internal combustion engine

Abstract

A relatively simple and reliable technique is described that has allowed spatially and temporally resolved measurements of the charge flow in the cylinder of a motored internal combustion engine to be made. the experiment uses real fringe laser doppler anemometry with single photon counting and digital autocorrelation for data capture. Measurements of mean and turbulent velocities for different positions, engine speeds, throttle settings and engine crank angles are presented. The experimental autocorrelation functions have been processed by curve fitting to a Gaussian velocity profile and by direct Fourier transformation which yields the velocity distribution without prior assumption of its form. The ability of such a technique to process very poor signal to noise ratios makes it a likely choice for measurements in firing engines.