The Effect of Engine Speed on the TDC Flowfield in a Motored Reciprocating Engine

Measurements of three velocity components have been obtained by forward-scatter laser Doppler anemometry in the transparent cylinder of a modified production engine motored in the speed range 300-2000 rpm with a disc-type combustion chamber and a compression ratio of 7.4. The in-cylinder flow development has been examined in detail with and without induction swirl at an engine speed of 1000 rpm. In both cases turbulence was non-isotropic during compression with a tendency towards isotropy at TDC. The swirl velocities at TDC of compression scaled linearly with engine speed while the volume-averaged turbulence intensity varied more than linearly with engine speed for both induction system configurations, increasing from 0.45 to 0.6 times the mean piston speed in the absence of induction swirl and from 0.4 to 0.5 with induction swirl.