Swirl velocity measurements in a firing production diesel engine by laser anemometry

Laser anemometry instrumentation and techniques have been developed for the investigation of swirling air motion in production diesel engines. Swirl measurements were taken in a Perkins 4.236 diesel engine operating under both motoring and firing conditions. Data were collected over many engine cycles to produce velocity histograms at 1000 and 1600 rpm for 50% of full fuel loading. Swirl velocity profiles under motoring conditions were found to be very close to the profiles obtained prior to injection in the firing case. After injection, a stratification in the flow appears relative to the motoring velocities with a marked reduction in the flow velocity in the region between the cylinder head and the spray. After combustion, the swirl velocity is always less than in the motoring case. The onset of turbulence causes a sharp increase in the measured turbulence intensity. Problems encountered in the use of the laser anemometry are also discussed.