Influence of Mixture Gas Conditions on the Laminar Combustion Characteristics of Natural Gas

Natural gas is a promising alternative fuel for the internal combustion engine, and natural gas engine has become an efficient and feasible measure to deal with the energy shortage and climate change. Since the laminar flame characteristics are the foundation of the turbulent flame, the laminar flame characteristics of natural gas have a significant impact on the combustion status and efficiency of the engine. A visual constant volume bomb was used to study the influence of the gas components, different excess air coefficient (lambda), and initial conditions on the laminar combustion characteristics of natural gas. The experimental results showed that when the initial pressure and temperature were 0.1 MPa and 300 K respectively, compared to propane, ethane had a remarkable influence on the equivalent-combustion laminar-combustion-speed, with an average increase of approximately 5.1% for every 2.5% increase in the ethane proportion. The laminar combustion velocity of the natural gas under different excess air coefficients had a maximum value at about lambda=1.0, and the Markstein length of the flame decreased with the increase of the lambda. The increase in the initial pressure of the mixture resulted in a decrease in the equivalent-combustion laminar-combustion-speed of the flame, a significant decrease in the Markstein length. The increase of the initial temperature of the mixture led to a rapid increase of the equivalent-combustion laminar-combustion-speed, but the effect on the flame Markstein length was not dominant.