Laminar Burning Velocity Mechanism and Flame Instability of LPG/DME Blended Gas Under Sub-Atmospheric Pressure

As a promising clean fuel, LPG/DME mixtures are increasingly used, with pressure being a key factor in combustion dynamics. This study investigates their fundamental combustion characteristics under sub-atmospheric pressures typical of plateau and mountainous regions. This paper investigates the propagation mechanism and instability law of spherical expanding flames of LPG/DME blended gases under different equivalence ratios (φ = 0.7–2.0) and initial pressures (P0 = 0.5–1.0 atm) by combining experimental studies and numerical simulations. The results showed that the laminar burning velocity (SL) showed an inverted “U”-shaped change with the increase of φ and peaked at φ = 1.0 (P0 = 0.5 atm, 50.85 cm/s), and the SL decreased significantly with the increase of P0. In addition, flame destabilization occurs mainly at flame-rich concentrations with P0 ≥ 0.5 atm, when hydrodynamic instability effect dominates compared to the diffusive-thermal instability, and flame destabilization implies an increased level of fire-explosion risk. The study reveals the correlation between SL of LPG/DME blends and key radical concentrations under sub-atmospheric pressure. Through the analysis of reaction sensitivity, it is found that an increase in pressure promotes the combustion of LPG/DME blended gas, while a sub-atmospheric pressure environment inhibits its combustion reaction. The study offers a key theoretical basis for optimizing combustion and predicting fire/explosion risks of LPG/DME blends under sub‑atmospheric conditions.