Motion model for describing the quantity of air in droplets through changing the structure of air induction nozzle

Air induction nozzles possess good anti-drift performance,the throat and orifice sizes of the nozzles are the main design parameters that affecting atomization.Therefore,Venturi tube nozzles and conventional flat fan nozzles were assembled together to investigate the flow rate,droplet size,the quantity of air in droplets affected by a single design parameter of nozzles with applying high speed camera and Spraytec laser diffraction system.The results showed that:the flow rate of the air induction nozzle depended only on the throat size of Venturi tube and pressure,and it was proportional to the throat size of Venturi tube at the same pressure;The flat fan nozzle’s orifice size and Venturi tube size significantly affected volume median diameter of droplets,which generally increased after adding surfactant;A new model was established after optimizing classical equation for calculating the percentage of intake air in droplets and studying the effects of throat and orifice size of air induction nozzles on spray characteristics.By variance analysis,it was verified that the new model of quantity of air in droplets produced by all connected nozzles was correct.The calculation showed that the bubbles sizes ranged at 200-900μm and were in proportion to the droplet size with the percentage of intake air of 10%to 90%.Contrast to the change of volume median diameter and droplet velocity,the existence of intake air could influence their change degree to some extent.

Experimental Study on Preheated Combustion of Pulverized Semi-coke

In a test rig,pulverized semi-coke was preheated to 850℃in a circulating fluidized bed(CFB)and then cornbusted at 1100℃in a down-fired combustor(DFC).Experiments were conducted to reveal the effects of three secondary air nozzle cases(co-axial jet,top circular jet and wall circular jet)on the NO emission.The results show that the optimized secondary air nozzle can reduce NO emission.O_2 concentration profile is the major factor affecting NO generation and emission,which is led by the secondary air nozzle.The lower O_2 concentration led to the generation of lower initial NO.The NO emission at the exit of the DFC was reduced from 189 to 92mg/m^3(@6%O_2)with the decrease of initial generation.The peak of NO at 100 mm below the nozzle should be attributed to the oxidization of NH_3 in the syngas,rather than the oxidization of fuel-N in the char.The low and well-distributed O_2 concentration contributes to the reduction of initial NO,which helps to reduce the NO emission.The combustion effieiencies of the eases of the co-axial jet,the top circular jet,and the wall circular jet are97.88%,98.94%and 98.74%,respectively.