The spray combustion characteristics of “inside-out" effervescent atomizer at low injection pressure have been investigated in the present study. The atomizer is mounted on experimental furnace cooled by separate segments water jacket the plain orifice atomizer is powered by diesel fuel and air as atomizing gas. The study shows the influence of A/F ratio, atomizing gas to liquid mass ratio (GLR), injection pressure, and exit orifice diameter on flame temperature
distribution inside the furnace. cooling water heat flux, stack temperature, and combustion efficiency. The air to fuel mass ratio (A/F) varies from 20 to 50 Kgair/Kgfuel, and operating pressure varies from 0.5 to 2 bar. The results show that the increasing on A/F ratio decreases the flame length, and exhaust gas temperature, while the combustion efficiency increases. It was found also that, when using A/F ratios higher than 30 the combustion efficiency becomes greater than 90%. Where, the increasing on operating pressure increases the flame maximum temperature and heat transfer to
cooling water. Moreover, increasing the combustion efficiency. The results could enrich our knowledge of effervescent spray combustion characteristics and achieving higher combustion efficiency with low pollutant emissions.