Cylinder structure of internal combustion engine

A cylinder structure of an internal combustion engine comprising:

• a body die casted and including a combustion chamber surrounded by a peripheral fence and a cylinder head, a gas inlet and a gas outlet which are defined on two sides of the combustion chamber respectively, two gas purge units arranged beside the combustion chamber and between the gas inlet and the gas outlet, each of the two gas purge units having a first purge orifice and a second purge orifice, the gas outlet being proximate to the combustion chamber and being higher than the gas inlet, two height positions of the first purge orifice and the second purge orifice of each gas purge unit being between the gas inlet and the gas outlet respectively;
• a titanium plating layer located on the second internal fringe of the peripheral fence of the body;
• and
• two shells, each of the two shells covering each gas purge unit so as to close the first purge orifice and the second purge orifice and to define a gas conduit among the first purge orifice, the second purge orifice, and the peripheral fence, such that when the internal combustion engine purges gas, exhaust gas flows through the gas conduit from the first purge orifice and discharges out of the gas outlet from the second purge orifice;
• wherein each gas purge unit further has a groove and a rib horizontally connected on a middle section of the groove, the first purge orifice and the second purge orifice are defined between two sides of the rib and the groove, a thickness of the rib is less than a depth of the groove, and a first internal fringe of the rib flushes with a second internal fringe of the combustion chamber.