Fundamental characteristics of combustion under a spark ignition engine generator fueled by hydrogen-added biogas

The lean burn capability of spark ignition engines fueled with biogas was investigated using a one-dimensional (1D) cycle simulation and Latin hypercube sampling. The dominant variables were hydrogen contents, spark timing, and relative air fuel ratio. The fundamental effects of hydrogen were first investigated in terms of the in-cylinder temperature, heat release rate, and flame shape. To describe the combustion behavior, a user-defined combustion model was input based on the laminar flame speed of the biogas-H-2 mixture. Hydrogen acted as an enhancer of thermodynamic properties in the combustion phase by increasing the temperature and heat release rate with H-2 addition for up to 15% volume ratio. By varying spark timings, the maximum torque timing was retarded with hydrogen addition. By varying the relative air-fuel ratio, the mass fraction of the fuel burned could be enhanced in the lean burn region.