MEASUREMENT OF AXIAL-FLOW VELOCITY IN CYLINDER OF RECIPROCATING-ENGINE BY SINGLE INCIDENCE-BEAM REFERENCE-MODE LDA

In order to measure flow velocity in the swirl and radial directions o f a cylinder of an engine in practical use by means of a laser Doppler anemometer(LDA) through a small measuring window on the cylinder head , a back scattering fringe mode LDA is used. This LDA, however, can no t be used to measure the velocity component in the axial direction of the cylinder. A single incidence-beam reference-mode LDA is developed to measure the velocity component along the optical axis of the LDA an d is applied to measure the fluctuating flow velocity in the axial dir ection of the cylinder. Ensemble-averaged mean velocity and fluctuatio n intensity of the velocity as measured using the LDA show good agreem ent with those measured using the conventional fringe-mode LDA. Based on these results, it can be concluded that the reference-mode LDA is a pplicable to measurements of the flow velocity in the axial direction of the cylinder through the small window on the cylinder head.