As the limit on combustion generated pollutants is becoming more strict, a potentially ecological as well as economical new technology to decrease combustion generated pollutants by liquid fuel combustion is to adopt a fuel pre-vaporized. premixed combustion. This paper presents a study on the liquid fuel vaporizing and mixing processes. An effective method for the calculation of turbulent two phase evaporating flow has been developed, based on a realistic droplet vaporization model and a comprehensive turbulence-particle interaction model. Using the method, the influences of inlet gas swirling and heating on water droplets evaporation and mixing processes are numerically studied and compared with our experimentally measured data which show a reasonable agreement. Then : fuel droplets evaporation and mixing processes in the pre-vaporized, premixed oil burner at different confinement conditions are simulated. According to our studies, a strong inlet air swirl can greatly enhance mixing between the droplets, the air, and the recirculated flue gas which enters the burner. It also sharply reduces the droplet velocity, and thus prolongs the droplet vaporizing and mixing time to maintain a stable premixed combustion, proper combustion chamber confinement should be designed to ensure that sufficient recirculated flue gas is supplied to fully vaporize the fuel droplets before exiting from the burner and the actual mass fraction of the gaseous fuel is higher than the flammability limit one.