The influence of jet medium disturbance on combustion of hydrogen-doped natural gas in low temperature environment

Abstract

Ambient winds, obstructions or the operation of mechanical devices can induce turbulent disturbances in the flow field of hydrogen-doped natural gas combustion. The effects of the initial turbulent environment formed by two types of jet medium, N₂ and compressed air (CA), on the combustion characteristics of Natural Gas-H₂-Air mixtures at about 0 °C are investigated by combining experiments and dynamic simulations for the flow field. While at P_jet (jet intensity) = 0.6 MPa, the X_N2 (Molar fraction of nitrogen) in the flow field of the N₂ jet increases by 0.39 % in comparison with the CA jet. The jet enhances the flame instability of the gas mixture by inducing turbulent disturbances, which in turn increases the frequency of flame cell splitting. The P_max (Peak overpressure) and τ (The time required to reach the peak overpressure) of mixtures show an increasing trend with rising P₀ (initial pressure)when P_jet < 0.4 MPa. For the N₂ jet medium, the k (Turbulent kinetic energy) of the flow field at the moment of ignition is higher than 1.25 m²/s² when P_jet > 0.4 MPa, and the inerting effect gradually dominates, this phenomenon is more significant at higher P_0.. The I (The impulse accumulation during the combustion)shows an increasing initially and then decreasing trend and reaches the maximum decreasing rate when P_jet increases from 0.4 MPa to 0.5 MPa. With the increase of P_jet to 0.6 MPa, the introduction of jet has an inhibiting effect on the P_max, which is reduced by 5.12 % compared with the static conditions. The research results can provide important reference for the safe use of hydrogen-doped natural gas and quantitative analysis of combustion risks in low-temperature environments.