Experimental Investigation on Unsteady Gas Flow in Small Two-Stroke Petrol Engines

The unsteady gas flow phenomenon in the gas exchanging process for a small two-stroke petrol engine with crankcase-scavenge is very complex. And the effect of its flow state on engine performances is extremely sensitive. In this paper, the effect of the intake and exhaust system for several small twostroke petrol engines on engine performances is investigated through the engine bench test. The airfuel equivalence ratios of engine carburators are statistically analyzed on the basis of a many of Measured data under different operating behaviours. Experimental investigation has indicated that the unsteady gas flow in the intake and exhaust system has influence on the characteristic of airfuel ratio, therefore, in the same time of utilizing the gas dynamic effect of unsteady gas flow for improving the engine performances, the carburator characteristic of airfuel ratio should be modified.