Numerical Simulation On The Performance Of Oxy-fuel Combustion Of Natural Gas In The Swirl Burner

Sustained development is the focus of global attention today,and energy structural reformation is the most imminent problem.Oxygen-enriched combustion has excellent application prospects,as a new combustion technology that can significantly increase combustion efficiency and reduce emission of exhaust.This study combined with oxygenenriched combustion technology and natural gas energy,using computational fluid dynamics methods to investigate the effects of swirl parameters and oxygen concentration on oxy-fuel combustion of natural gas in swirl burner.In this study,according to the burner design theory and design formula,a double swirl burner is designed for a 1.5MW natural gas heating furnace.The Ansys Fluent numerical simulation software was used to calculate the oxygen-enriched combustion process using the PDF combustion model,and the NOx emissions were calculated using the ISAT algorithm and the GRI 3.0 database.The influence of various factors on the combustion flow field and component concentration field was studied by changing the straight flow speed(7m/s,8m/s,9m/s,10m/s),primary swirl intensity(0.60,0.87,1.04),secondary swirl intensity(0.63,0.93,1.11)and oxygen concentrations(21%,23%,25%,27%).The study shows that straight flow is directly mixed with primary swirl flow.If the velocity of straight flow is too fast,the vortex energy transmission and shear layer formation will be affected.If the velocity of straight flow is too slow,the nozzle outflow will be suppressed and diffused;The primary swirl flow dominates the production of the central recirculation zone and the primary mixed combustion.Its swirl intensity determines the initial shape and the expansion angle of the central recirculation zone.The primary swirl intensity has a great influence on the axial size of the recirculation zone.Enhancement of the primary mixing increase the velocity of the flame,and reduces the generation of rapid NO,leading to a earlier timing of secondary mixing;The secondary swirl flow dominates the secondary mixed combustion and brings in the supplemental gas and fluid kinetic energy.The secondary swirl intensity has a great influence on the radial size of the recirculation zone.Considering the mixing of secondary air flow and the large amount of high temperature flue gas,the region of high temperature and heterogeneous mixing was generated with a large amount of thermal NO emmisions.Changing of the oxygen concentration affect the primary and secondary combustion intensities and create lean and rich combustion zones,which have a greater impact on NOx emissions.The result shows that the designed double-swirl burner plays a control role in the combustion and mixing process,and has excellent adaptability to combustion in an oxygen-rich environment.The influence of operating parameters such as straight flow speed,primary swirl intensity,secondary swirl intensity,and oxygen concentration on the combustion flow field,temperature field,and pollutant discharge was obtained.This study provides a theoretical reference for oxygen-enriched swirl combustion characteristics and industrial practice.