An Assessment of Hydrogen Addition to Methane Combustion with Argon as a Working Fluid in a Constant Volume Combustion Chamber

Abstract

ABSTRACT Combustion of natural gas in combination with hydrogen, coupled with argon as a working fluid, is a promising approach to increasing the efficiency of internal combustion engines while decreasing emissions. The use of argon as a working fluid effectively eradicates NOx, extends the flammability limits, and increases the thermal efficiency due to its high specific heat ratio. Additionally, the hydrogen addition aids in emissions reduction and enhances the flammability range. In this study, premixed CH4-H2-O2-Ar combustion is experimentally investigated in an optically accessible constant volume combustion chamber to determine the effect of hydrogen addition on laminar burning velocity, flame morphological structure, and instabilities when argon replaces nitrogen as the working fluid. A numerical thermodynamic model is applied to calculate the laminar burning velocity and an image processing technique is used to quantify the flame speed. The experiments show that, in comparison to methane alone, the addition of hydrogen (40%) to the mixture at atmospheric pressure (1 bar) and room temperature (298 K) increases the maximum laminar burning velocity by 37%, increases the maximum flame speed by 35%, and extends the lower and upper flammability limits from equivalence ratio of 0.4 to 0.3 and 1.6 to 1.7, respectively.