Research Of Short Flame And Low NO_x Combustion Technology For Small Oil Stoves

Small oil stoves are used widely as heating source in many fields.However,commercial oil burners used now are designed with long flame length which could not fit the structure and size of the hearth,resulting in some bad consequences,such as more serious coke phenomena in the burner and hearth,incomplete combustion of the fuels and the low efficiency of the stove system.Moreover,people are caring more about the notion of energy conservation and emission reduction,which leads to more strict emission standard.Therefore,it is of great importance to develop the technology of combustion with short flame and low NO_x emission level.The theories about the flame length and NO_x emission are summed up and the relative combustion technology and the research method are concluded.On this basis,the structures of swirl-blade flame holder and the inject combustion cylinder are designed.CFD method is employed to investigate the air dynamic field of new structures with RNG k-? two equation model.The research shows that the new structure of swirl-blade flame holder has more percentage of swirl air and the intention of recirculation becomes stronger.As the blade angle ? reduces,the swirling intensity of the flame holder becomes stronger and the recirculation zone the velocity peak becomes bigger.The structure of inject combustion cylinder could inject the smoke to the bottom of the flame effectively.The inject coefficient ? is influenced by the structures of inject slot and flame holder,ranging from 20~30%.On the basis of cold state research,various combustion characteristic parameters are studied to find their relationship with flame length and NO_x emission level.Research shows that when the blade angle ?=25°,the flame length is shorter then that of the primary structure by 35.5%,which is the peak value.Other methods which could shorten the flame length are rising the inlet air temperature,raising the excess air coefficient ?,enlarging the spray angle ? and using air-blast atomizer.When the inject coefficient ? is valued 27.38%,which is peak value,the NO_x emission level could be reduced by 63.3%.When the spray angle ? is 50°~60°,the NO_x emission level is at its lowest value.Other methods which could reduce NO_x emission level are decreasing the swirling intensity S of the flame holder,raising the percentage of inert air ratio ? at inlet,choosing bigger excess air coefficient ? and using air-blast atomizer.The requests of “short flame” and “low NO_x emission level” are consistent in some areas,while they are contradictory in some other areas.In the process of designing,the designer could refer to the method concluded in this paper.