Investigation On Flow Characteristics And Combustion Characteristics Of Jets Issuing From A Sudden Expansion Chamber Of Noncircular Inlet

The patent of "Naturally oscillating jet devices" is proposed by Professor Mi Jianchun in1998. The long-term operation in the foreign industrial furnace shows that self-excitedoscillating-jet burners have simple structure and good performance. They can deliver areduction of20%~70%of NOxemissions and also less fuel consumption by5%~20%. Thereare only few reports and papers on self-excited oscillating jet in China and abroad up to now.In this subject, PIV cold-state experimental research was developed, and self-excitedoscillating-jet burners were designed and manufactured based on PIV experiments,combustion experiments were conducted in the gas-fired boiler of Changsha University ofScience and Technology. The flow characteristics and combustion characteristics ofself-excited oscillating jet is thorough analyzed and researched in this subject.First, PIV research using air as media, and olive oil droplets as trace particles werecarried out of jets issued from sudden expansion chamber of different chamber aspect ratios,different inlet expansion ratios, different inlet Reynolds numbers and different inlet shapes,such as equilateral triangle, diamond, notched-rectangular etc. The geometric structureparameters and physical parameters that self-excited oscillating jet occurred is obtained in thisPIV research.Next, self-excited oscillating-jet burners were designed and manufactured based on PIVexperiments, and combustion experiments using liquefied petroleum gas as media wereconducted in the gas-fired boiler of Changsha University of Science and Technology, theexperiment results are compared with traditional burner. The results show that, the furnacetemperature using burner of triangle inlet chamber is lower than using burners of diamond andnotched-rectangular inlet chamber. But the flame fullness is inferior to the latter two. And thefurnace temperatures present the trend that decrease, rise, decrease and rise. But the furnacetemperature of simple jet burner is decreased with furnace depth increased, and only increasedin furnace tail due to the return of flue gas.