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For high-speed imaging a newly developed eight-fold CCD camera, which permits framing rates of up to one million pictures per second, was used to obtain pictures of the injected sprays during the operation of a diesel engine. For the particular case studied here the framing rate was set at 50,000 pictures per second. This rate was sufficient to resolve the temporal development of the sprays in the transparent version of the four-cylinder, in-line, 1.9 litre DI production diesel engine of Volkswagen. The advantage of the camera is that it needs no light pulses for illumination, but can operate with a continuous light source. Each of the CCD chips is arranged around a central eight face reflecting pyramid, which splits the light coming from the camera lens to each CCD chip. The chips can be shuttered freely (asynchronously) at programmable inter-frame spacings thus permitting operation with continuous illumination. In this particular case a 30 Watt halogen lamp was used.

The paper describes detailed studies about the spray formation of a direct-injection high-pressure gasoline injector and the interaction of the droplets with the surrounding compressed air in pressure chamber experiments and inside an optically accessible research engine. Different optical techniques, like stroboscopic video technique, high-speed filming with flood-light illumination or with light-sheet illumination by a copper vapour laser, particle image velocimetry of the droplets, laser-induced fluorescence of the liquid phase, and spontaneous Raman spectroscopy for the measurement of the fuel/air ratio are used. From the recorded images spray characteristics such as spray penetration and spray cone angle are evaluated for different settings of the chamber pressure and temperature and for different rail pressures. The results show that all techniques are suitable to derive the quantities mentioned above.