Turbulent Flow Measurements by Laser-Doppler Anemometry in Motored Piston-Cylinder Assemblies

Laser-Doppler anemometry has been used to quantify the mean velocity and turbulence characteristics of the isothermal, incompressible flow within a piston-cylinder arrangement motored without compression at 200 rpm and with idealized inlet geometries corresponding to a pipe and to an annular port located in the centre of the cylinder head. The results indicate that the pipe entry gives rise to a strong vortex near the piston as the indrawn air is deflected radially along the piston face and cylinder wall; this, in turn, gives rise to a weaker, counter-rotating vortex near the cylinder head which grows appreciably as the piston approaches bottom-dead-centre. With the annular-port entry, the inlet jet is angled and results in a flow pattern with a large vortex occupying nearly all of the flow space with much smaller vortices at the corners between the wall and the piston and cylinder heads. The effect of a piston bowl was also investigated for the port entry and is shown to be small.