Theoretical analysis and experimental investigation of flame trajectory of horizontal subsonic jet diesel spray under sub-atmospheric pressure

The safety of a horizontal spray combustion flame and the design of a heating device for a low-pressure area of a plateau have both been widely examined. The shape equation and length of a flame's trajectory are the two most important indexes. Regardless of the atomization and evaporation process of fuel, the analytical formula of trajectory for a horizontal spray flame supplied by forced swirling air is derived, and the numerical solution is obtained. The variation in flame trajectory and its uplifted characteristics with atmospheric pressure are analyzed theoretically and verified experimentally. The flame trajectory length and its coincidence degree at 0.05 and 0.08 MPa of atmospheric pressure are compared. The results show that the flame trajectories coincide when the rated volume air flow is maintained under different atmospheric pressures. Keeping the same equivalence ratio, the slope of the uplifted trajectory is proportional to the atmospheric pressure. If flame trajectories coincide at any two atmospheric pressures, the ratio of equivalence is the inverse ratio of air density. Finally, based on the air entrainment theory, the flame trajectory length equations for different atmospheric pressures and equivalence ratios are unified. This study is of great theoretical significance to research into low-pressure spray flames and the design of a high-altitude oil burner.