Steady Intake Flow Characteristics Through a Diesel Four-Valve Cylinder Head
The annular flow around the two intake valves of a production four-valve diesel cylinder head has been investigated by laser Doppler velocimetry under steady flow conditions at a mass flowrate of 85 Kg/h corresponding to an engine speed of 1000 rpm. The results showed that the primary velve generates much stronger swirl than the secondary valve, which in turn generates more than 20% higher mass flow rate. When both valves are open, the generated swirl and mass flow levels fall between those obtained with the primary and secondary valves but much closer to the former than to the latter. The exit flow around the intake valves was found to be non-uniform, with more pronounced the case of the primary valve with the maximum exit flow at the planes towards the end of the helical ramp of the port. Similar non-uniform flows were observed when both valves were open except for the two planes of the primary valve which are affected by the jet flow exiting from the secondary valve. Turbulence, in general, was anisotropic with maximum levels of about 5Vp(Vp=mean piston speed) near the cylinder head.
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