In order to improve the operating safety of diesel engines in methane-rich mines

three-dimensional computational fluid dynamics (CFD) software

CONVERGE， was used to simulate the influence of diesel engine intake blended with different volume concentrations of methane on engine performance and emissions. Results show that when the temperature of methane on fire is greater than 1000K

the blending of methane will increase the number of hydroxyl (OH) groups

which can promote the combustion of diesel engines. When the engine is running at 1200r/min and with 80% load

increasing the methane blending ratio to a volume concentration of 1.00% can shorten the ignition delay period from 7.35° in crank angle to 7.07° in crank angle

and increase the peak heat release rate by 0.1%

resulting in the maximum combustion pressure in the cylinder increased from 16.05MPa to 16.45MPa

and the maximum combustion temperature risen from 1737K to 1771K. For exhaust emissions

the use of methane increases NOx emission from 10.55g/(kW·h) to 11.36g/(kW·h) and hence CO emission from 0.12g/(kW·h) to 1.34g/（kW·h）

but soot emissions can be decreased from 1.21×10-3g/(kW·h) to 7.85×10-4g/(kW·h). Considering that the volume concentration of methane in the air of mines is generally less than 0.7%

so it has little influence on operating safety of diesel engines.