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Phase-resolved DGV Measurements of an Engine Exhaust Flow

The aim of this application of Doppler global velocimetry was to provide three-component, phase-averaged velocity data of the engine exhaust flow with a phase-resolution of 5-10^o for direct comparison with numerical simulations, ultimately providing a means of validating numerical simulations used in the industrial design process. The test object chosen for this application was an unfired, externally driven four cylinder, turbo-charged engine driven at 2000 rpm (partial power) and 6000 rpm (maximum power). Phase-averaged DGV measurements were made possible by adding an acousto-optic modulator (Bragg cell) to an existing DGV system that was previously optimized for the measurement of time-averaged velocities. CCD cameras with a high signal-to-noise ratio and low dark current (background signal) allowed for integration times up to one minute thereby obtaining velocity averages of more than 1000 cycles. The DGV measurements were performed at the exit plane of the exhaust manifold for cylinders 3 and 4.

Further details can be found in our paper presented at the 10th Intl. Symp. on Applications of Laser Technique to Fluid Mechanics which is available for download (PDF-Format, 1.2 MB).

Figures and Images:

Optical arrangement for DGV measurements on engine exhaust manifold. Image of the setup	Phase-averaged, three-component velocity data obtained by DGV at the exit plane of an exhaust manifold after the junction of cylinders 3 and 4. The data on the left was obtained for an engine speed of 2000 rpm (partial load) and 6000 rpm (full load) on the right. The crank angles in both cases are identical. The averaging interval covers 5° of the cam-shaft’s rotation.
Animation of results at 2000 rpm (Animated GIF, 1.3MB)	Animation of results at 6000 rpm (Animated GIF, 1.4MB)