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The equivalent effects of initial temperature and dilution ratio on premixed combustion of natural gas in the constant volume combustion bomb are studied. The initial pressure pu and equivalence ratio  are set to be 0.3 MPa and 1.0 in experiment, respectively, and the ball type flame extension method by high speed schlieren photography is used in the experiment. Stretched flame propagation velocity Sn, unstretched flame propagation velocity SL, Markstein length Lb, laminar combustion velocity uL and NOx emission are analyzed in detail. The results show that SL, flame development duration and combustion duration are nearly identical, but the laminar burning velocity uL has a big difference at the operating points that have similar Sn value. The influence of dilution ratio on SL and uL is greater than that of initial temperature when the dilution ratio is small. Further research finds that the temperature difference ΔTu= 50 K has equivalent effect on combustion process compared with dilution ratio ΔDR=2%. Under the boundary conditions of the similar Sn, the NOx emission is lower under the conditions of higher initial temperature and dilution ratio compared with the smaller initial temperature and dilution ratio. [ABSTRACT FROM AUTHOR]

The effects of atmospheric pressure, unburned mixture temperature and equivalence ratio on the sec-butanol-air laminar flow combustion were investigated by the smear method and the spherical flame diffusion method. The coupling effects of environmental parameters and equivalence ratio on the unstretched laminar burning propagation velocity and the change value, change rate and ratio of change rate of unstretched laminar burning propagation velocity were mainly analyzed. The results show that the larger the pressure is, the smaller the variation of unstretched laminar propagation velocity is under the coupling of ambient pressure and equivalent ratio. The ratio of change rate of unstretched laminar burning propagation velocity is increased with the increasing of equivalence ratio with downward trend for the equivalence ratio around 1.10. When the equivalence ratio is less than 1.05, the low pressure environment has greater influence on the laminar flow combustion. Under the coupling of ambient temperature and equivalence ratio, the propagation velocity of unstretched flame is more affected by higher ambient temperature when the equivalence ratio is in the range from 0.75 to 1.15. When the equivalence ratio is less than 0.85 or greater than 1.45, the equivalent ratio has great influence on the rate of non-tensile laminar flow combustion. [ABSTRACT FROM AUTHOR]