The Development of Scanning LDA for the Measurement of Turbulence in Engines

A scanning Laser Doppler Anemometer system has been developed for the measurement of spatial velocity profiles in motored internal combustion engines. Tests were carried out on a single cylinder engine with a disc shaped combustion chamber, at an engine speed of 1200 rev/min.

Ensemble averaged mean and RMS velocity estimates show good agreement with conventional LDA measurements. Longitudinal and transverse autocorrelation functions have been calculated, and estimates have been made of turbulence length scales. These have been found to be comparable with length scales measured in engines by other techniques. This investigation has demonstrated that scanning LDA is a powerful technique for characterising in-cylinder air motion in engines.