The invention relates to a
natural gas engine, in particular to a
lean burn layered
combustion chamber structure of a direct injection
natural gas two- valve engine. The
combustion chamber structure comprises a
piston, an air cylinder cover, an air cylinder, an intake valve and an
exhaust valve, and is characterized in that a top face of the
piston is provided with a flow guide pit; a
natural gas nozzle part is arranged on the air cylinder cover closes to a part with a larger curvature
radius of the flow guide pit; a
spark plug is also arranged on the air cylinder cover at a position corresponding to that of the natural gas
nozzle and is close to a part with a smaller curvature
radius of the flow guide pit. In the structure, the flow guide pit 8 is arranged on the top of a protruding
piston, and the natural gas
nozzle aligns with the part with a larger curvature
radium of the flow guide pit 8 and can cooperate with the spray
time and motion of the piston to guide a spray beam and with the flow of
compressed air to increase the concentration of the natural gas near the
spark plug so as to form uneven layered mixed gases during lean burning to improve ignition performance and
combustion performance of the engine.