Direct measurements of in-cylinder integral length scales of a transparent engine

 This paper presents a hardware technology and its accompanying software developed to measure the in-cylinder integral length scales of the flow inside a transparent four-stroke engine directly, using a fiber laser Doppler velocimeter (LDV). A traverse table was designed to combine two 1-component fiber optical probes to form an LDV system with the capability of both 2-component single-point and 1-component two-point simultaneous measurements for velocities. This paper demonstrates the evaluation of radially separated lateral and longitudinal integral length scales. The location was at a mid-plane of the top dead center (TDC) clearance height, and the engine was motored at a speed of 500 rpm. Data analysis was processed using statistical techniques and the physical meaning of the results was explained. Received: 27 August 1996/Accepted: 6 December 1996