Effect of a magnetostatic field on laminar premixed hydrogen–air flames

Magnetic fields have shown potential to affect flame characteristics. However, the mechanisms of interaction between a magnetic field and a flame are not fully understood. This paper investigates the effect of magnetic fields on premixed hydrogen–air flames that are prone to intrinsic instabilities, with a focus on the impact of magnetic forces on the flame behavior. The study is conducted using direct numerical simulations. Two flame conditions, both with an equivalence ratio of 0.5, are studied: one with reactants at atmospheric conditions and the other with reactants at high pressure and high temperature. Different configurations of the magnetic field are investigated, each characterized by different values of the gradient of the square of the magnetic field. In all configurations with a magnetic field, this gradient is oriented in the direction opposite to the velocity of the incoming reactants. Results show that the investigated magnetic fields can reduce the flame consumption speed through a reduction in flame area, an effect that is substantial for the atmospheric pressure case. Conversely, in the high-pressure case, no significant effects of the magnetic fields are observed. Analysis of the force contributions demonstrates that the change in the flame area is caused by the rotational component of the magnetic forces, which alter the vorticity of the flow such that the hydrodynamic instability tends to reduce. These forces, which require a gradient of magnetic susceptibility not aligned with the gradient of the magnetic field magnitude, are significant at atmospheric pressure, while they become negligible compared to the pressure gradient at high pressure. Ultimately, the results of this work indicate that magnetic forces have the potential to change the flame behavior, a mechanism that could be used for active control of flame characteristics.