LASER-DOPPLER TECHNIQUES FOR THE COMBINED MEASUREMENT OF INLET FLOW AND VALVE MOTION IN IC ENGINES

A measurement methodology and a test set-up for the experimental inves tigation of internal combustion engines are presented. This system is based on a laser Doppler anemometer and a laser Doppler vibrometer whi ch measure in a co-ordinated or simultaneous mode both the velocity of the intake flow and the motion of the inlet poppet valve. A synchroni zed data acquisition procedure allows the use of two optical instrumen ts to analyse the effects of valve jumps and bounces on the inlet flow field. At high rpm, anomalous valve behaviour may appear. Fluid veloc ity measurements are taken inside the cylinder and the manifold of a m otored automotive engine head at different rpm, up to a speed at which anomalous valve behaviour regularly occurs. Velocity data are process ed in both time and frequency domains. This measurement system also re presents a valuable tool to study resonance phenomena in ducts.