The working principle of a two-stroke engine

There are three holes on the engine cylinder block, namely the intake hole, exhaust hole, and air change hole, which are closed by the piston at a certain time. Its working cycle includes two strokes:
1. First stroke: The piston moves upwards from the bottom dead center, and after the three air holes are simultaneously closed, the mixture entering the cylinder is compressed; When the intake hole is exposed, the combustible mixture airflow enters the crankcase.
2. Second stroke: When the piston is compressed near the top dead center, the spark plug ignites the combustible mixture, and the gas expands to push the piston down to do work. At this point, the air inlet is closed, and the combustible mixture sealed in the crankcase is compressed; When the piston approaches the bottom dead center, the exhaust hole opens and exhaust gas rushes out; Subsequently, the air vent is opened, and the pre compressed combustible mixture is flushed into the cylinder to drive away the exhaust gas and carry out the air exchange process.