Cycle-Resolved Flow Measurements in the Exhaust Pipe of Single Cylinder Two Stroke Engines

The instantaneous flow from the exhaust pipe of a single cylinder two stroke engine was studied in this research. Three exhaust pipes were investigated. One is a simple pipe with an expansion chamber, and the other two are commercial exhaust pipes. The flow field in the exhaust pipe was calculated using the one-dimensional unsteady gas dynamic model. The instantaneous velocity of the exhaust flow was detected using a hot wire anemometer located at the exit of the exhaust pipe.

The calculated pressure variations inside the chambers of the exhaust pipe agreed quite well with the measured data. The calculated instantaneous exhaust velocity also matched the measured velocity variations in cases where reverse flow did not occur. However, discrepancies occurred at low engine speeds because the hot wire anemometer can not distinguish between forward and reverse flow. If the measured cycle-resolved velocity was adjusted to account for the effect of reverse flow, both the total flow in the entire cycle and the instantaneous flow rates obtained from model calculations agreed quite well with the measured data.