Transient dynamics of two injection flows, upstream and downstream from a swirl injector, are investigated. Capillary n-heptane pipe flow is measured using laser Doppler anemometer to obtain the instantaneous time series of centerline velocity and to reconstruct a series of instantaneous and integrated flow rates and pressure gradients. A collimated laser sheet and a high-speed video camera visualize injected spray flow. Finally, the phase Doppler anemometer measurements are introduced to analyze instantaneous patterns of droplets, velocity-size and number density in the fuel spray.

All measurements are employed at similar temporal resolution close to 30 μs. Results indicate that both flows are strongly time-dependent and well correlated in time-phases. Initial transitions are completed by 100 μs. Opening or closing of the injector valve affects both flows as strong delta oscillation causes spray penetration dynamics and a post injection effect.

A combination of non-intrusive laser-based techniques allows indication of the basic injection and spraying characteristics needed to optimize high-pressure fuel injectors and the late injection combustion mode.

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