Engine-Based Image Acquisition for Piloted Diesel Fuel Spray Analysis

An optically-accessible research engine, image acquisition, and a control system are designed to acquire two-dimensional images of a pilot and main Diesel fuel sprays. This paper presents the engine-based apparatus, image acquisition techniques, and preliminary results of analysis performed upon interacting Diesel fuel sprays. The engine is a single-cylinder compression-ignition two-stroke with optically-accessible head mounted on a high speed CFR engine crankcase. It is equipped with a special dual-injection system for production of in-cylinder interacting sprays (main and pilot) with a high degree of adjustability with regard to the sprays fuel quantities and injection timings. The engine construction permits illumination of the sprays by a thin sheet of laser light from a pulsed Nd:YAG laser frequency doubled to operate at the visible wavelength of 532 nm. Light scattered from the droplets passes through a top-mounted viewing window on a diode array camera, yielding a digital image which defines the boundary of the spray plumes. Within the plumes the varying scattered-light intensity permitted acquisition of spatially-resolved images of the interacting sprays. Personal-computer-based programs control injector activation times, synchronize operation of the laser illumination system, and acquire/process and display of the spray plume images. Two dimensional images are presented and discussed for a selected condition.