Measurement of unburned hydrocarbons in a lean burn natural gas engine with prechamber by using PLIF technique

A producing process of unburned hydrocarbons in the cylinder of a natural gas engine with prechamber was investigated. Distribution of unburned hydrocarbons (UHC) was measured by the planer laser induced fluorescence (PLIF) and acetone was selected as a tracer in fuel, after investigating of characteristic of acetone. The effects of acetone concentration in fuel and ambient pressure on laminar burning velocity were investigated. Furthermore, the effects of laser energy, ambient pressure and equivalence ratio on fluorescence were conducted. A single cylinder gas engine with 170 mm bore was used and the UHC was visualized by attaching a cylinder made of quartz on the top of the liner. The result obtained from the PLIF measurement showed that the UHC from the prechamber was little despite of rich mixture in the prechamber. In the main chamber, the UHC from the crevice of top land between the piston and the cylinder liner during expansion stroke was confirmed. And a little amount of UHC was observed in the burned gas at the end of combustion. This was also confirmed by the images with a high-speed video camera.