Flow characteristics of a motored spark ignition engine with a prechamber.

To understand the effect of a torch jet on the flow characteristics in a prechamber spark ignition engine, a laser Doppler anemometer (LDA) is used to measure the velocity in a main chamber under the motored condition. The engine is operated at a constant speed of 1000 rpm with a wide open throttle (WOT). The mean velocity, turbulence intensity and turbulence scales are calculated by a cycle-resolved analysis with a cut-off frequency of 650 Hz. The reasonable selection of the cut-off frequency is based on the ensemble-averaged power spectra. During the expansion stroke, the mean velocity, turbulence intensity and integral length scale are found to be strongly affected by the torch jet flow, which is dominated by the torch nozzle area size.