Intake Air Velocity Measurements for a Motored Direct Injection Spark Ignited Engine 1999-01-0499

Velocity measurements have been made in a motored engine intended for direct injection spark ignited (DISI) operation. Previous experiments showed the effect of intake gas velocities on direct injection spray plumes in this engine, without directly quantifying the gas velocities involved. This work documents the intake velocities in the vicinity of the spray plume, although the spray was not present in these experiments.

The measurements were made using an LDV system. Two velocity components were measured, though not simultaneously, through two orthogonal windows in the cylinder of an optical engine equipped with a head designed for DISI engine use. This engine had 4-valves and a pent-roof; the injector (when installed) was positioned slightly off-center in the head, with the spark plug located near by. Three different operating conditions were simulated: a low load, low speed condition (29 kPa MAP, 750 RPM), a medium load and speed condition (41 kPa MAP, 1500 RPM) and a high load, medium speed condition (100 kPa MAP, 1500 RPM). Velocity measurements were made along 3 cylinder diameters through the “side” window and along 2 cylinder diameters from the “front” window. All measurements were made in a plane 39 mm below the tip of the injector in the head.

The results of the velocity measurements show mean velocity and fluctuating velocity values for each measurement point. The general flow pattern at high load (high intake flow rate) showed high tumble, particularly as the piston moved towards TDC of compression. The magnitude of the fluctuating velocities was, in general, quite high, particularly in tangential flow directions.