Experimental investigation on horizontal jet spray flame characteristics with a constant air-fuel ratio in different sub-atmospheric pressures

•Morphological features of horizontal spray flame at different atmospheric pressures.•A dimensionless representation of flame stability in flame fluctuation region.•Flame trajectory dimensionless temperature reflect the horizontal buoyancy uplifted.•Unique air entrainment data revealed for varying air-fuel ratios and air pressures. It is hoped that horizontal liquid fuel spray burners can be better applied to small heating and heat transfer equipment in high-altitude areas. The morphology and temperature characteristics of diesel horizontal spray flame were investigated in a low-pressure chamber (0.05–0.10 MPa). The results show that when the air-fuel ratio is constant, the horizontal projection length of the and uplifted feature of the flame are proportional to the atmospheric pressure, which is completely contrary to the change rule when only the volume flow of air is kept constant. When the air-fuel ratio is constant, the flame trajectory at different atmospheric pressures can be normalized into two equations with 0.08 MPa as the dividing line. The dimensionless flame fluctuation length β can reveal the stability of the horizontal spray flame. An increase of β indicates that the diameter of the flame holder and swirling intensity need to be moderately increased at high altitudes. That is also confirmed from the perspective of the air entrainment coefficient. In addition, an accurate flame length prediction model is established. Dimensionless temperature analysis reveals that the air-fuel ratio needs to be closer to the stoichiometric ratio when compared with normal pressure.