Investigating the combustion stability of shale gas engines under HHO

Abstract

Brown gas (HHO) contains H2 and O2, as well as a small amount of active oxygen radical hydroxyl (·OH), which not only promotes the flame propagation process, but also affects the stability of the shale gas engine combustion process. In this paper, we investigate the combustion stability of shale gas engines by adjusting the HHO blending ratio. In particular, the influence of HHO content on the in-cylinder pressure and heat release process of a shale gas engine is analyzed, the combustion cycle trends are discussed, and the dynamic characteristics of the combustion process are evaluated. The influence of HHO content on the stability of the flame propagation process in the cylinder is then determined. Results demonstrate that the in-cylinder pressure increases, heat release rate and the engine combustion stability increase with the HHO blending ratios, while the average indicated pressure distribution range, and pressure coefficient of variation in the combustion phase decrease. Furthermore, the increase in HHO content leads to the gradual tightening of the reconstructed phase space trajectory distribution, improves the periodicity of the engine working process, enchances the certainty of the front and back cycles in the combustion process, and improves the stability of the engine working process. Moreover, an increase in the HHO content enhances the cylinder heat release rate, the combustion temperature, the temperature distribution area, the fire core radius, the peak flame surface density, and the flame propagation.