LPP燃烧室振荡燃烧火焰和流场相互作用的实验和数值研究

Experimental and Numerical Investigations on the Interaction of Flame and Flowfield Under Combustion Oscillation in the LPP Combustor

本文开展了贫预混预蒸发(LPP)燃烧室振荡燃烧时火焰–流场相互作用的实验和数值研究。利用数值模拟研究了稳定燃烧时的热态流场和火焰结构,以及振荡燃烧时的燃烧室压力波动及主频,与实验中用PIV、OH-PLIF和压力传感器测得的热态流场、火焰结构和压力波动及主频吻合得较好。对振荡燃烧工况的大涡模拟研究发现:在一个振荡燃烧周期内,燃烧室内压力波动导致了预混预蒸发段前后压差波动,进而引起了预混预蒸发段出口处轴向速度波动和流场扭曲,并伴随着剪切层附近的旋涡形成、发展和脱落。旋涡改变了火焰形状和位置,导致放热率的周期性波动,进而引起流场的周期性波动。周期性波动的放热率和流场耦合,形成火焰–流场的相互作用,使得振荡燃烧持续下去。

Experimental and numerical simulations were conducted to investigate the flame-flowfield interaction in a lean premixed prevaporized(LPP)combustor under oscillating condition.Numer-ical simulation was used to study the reactive fowfield and fame structure under stable condi-tion,as well as the time series pressure fuctuation and frequency spectrum of dynamic pressure under oscillating condition.It was found that reactive fowfields,fame structures,pressure fluc-tuations and the dominant frequency measured by PIV,OH-PLIF and dynamic pressure sensor in experiment were in good agreements with LES results.Large Eddy Simulation results show that the pressure fluctuation in the LPP combustor leads to the pressure difference fluctuations of the premixer,which causes the axial velocity fuctuations and fowfield distortion at the outlet of the premixer,accompanied by the formation,development,and detachment of vortex near the shear layer.The vortex changes the fame shape and position,which leads to the periodic fuctuation of the heat release rate,and causes the periodic fuctuation of the fowfield.The periodic fuctua-tions of heat release rate and flowfield are coupled together,which makes the combustion oscillation continue.