An Investigation On Cold Flow Characteristic Of Afterburner With Cavity/Strut Hybrid Flameholders

With the development of aviation engine, afterburner inlet total pressure and total temperatureincreasing, the working environment of afterburner even worse. The fuel supply facility as well asbluff body flame stabilizer of traditional afterburner were placed in the flow path, it will inevitablybring some problems, such as higher total pressure loss, auto ignition. In order to obtain a moresuperior performance under severe conditions, it is necessary to develop new concepts based ontraditional afterburner. To investigate the flow characteristics of afterburner with cavity/strut hybridflameholders, theoretical, experimental and numerical simulation study are conducted.Particle imaging velocimetry (PIV) measurement was carried out to investigate the cold flowcharacteristics of the model afterburner. The results showed that:1) When the inlet Mach number increases, the trapped vortexes in cavity become more stableand the radial penetrating depth of the air from the cavities increases, the width of therecirculation zone increase, while in the mainstream section,the size of recirculation zone incavity increases;2) When the inlet deflective angle increases, the rectificaion of flameholders get worse, theflow field became less uniform, when the angle is less than9°, the rectification offlameholders get better;3) When it is in strut-only model, it can form a complete recirculation zone in cavity and thevortex structure in recirculation zone will not be affected by the high-speed airflow ofmainstream.A comparison between the numerical results and the experimental results demonstrates thesuperiority of the standard k-ε turbulence model in TVC flow prediction. The cold flow characteristicof afterburner with cavity/strut hybrid flameholders were obtained using numerical simulationmethods. The following conclusions were obtained：1) When the length of the cavity increases, the flow rate in cavity increases, the radialpenetrating depth of the air from the cavities increases, the size of recirculation zonebecomes larger, the axial distance of vortex core becomes larger, the radial distanceincreases slightly;2) When the height of the cavity increases, the flow rate in cavity increases, the air flowvelocity becomes large, the residence time is shorter, the ability of momentum and energyexchanging between cavity and main stream enhances, the vortex core axial distance increases, radial distance decreases;3) When the angle of cavity back wall increases, the flow rate in cavity increases, the vortexcore axial distance and radial distances increases, and the change of axial distance is about2times as the change of radial distance;4) When in strut-only mode,the strut of65°has better performance, However, in cavity+strutmode,the strut of90°has better performance. When the angle increase in cavity+strut mode,the flow rate in cavity increases, the total pressure loss decrease,the rectificaion offlameholders gets better;5) When the inclination angle of strut increases, the total pressure loss in afterburner decreases,the flow rate in cavity decreases, the radial penetrating depth of the air from the cavitiesincreases, the axial vorticity behind the strut increased, the ability of momentum and energyexchanging between cavity and main stream enhances, the rectification of flameholders getworse;6) Optimized parameters of afterburner with cavity/strut hybrid flameholders are obtained bynumerical simulations methods. The axial position of the cavity is200mm dowmstream ofinlet, the height of cavity is45mm, the length of cavity is60mm, the angle of cavity backwall is135°, the back angel of strut is90°,the inclination angle of strut is30°. The resultsshow that the the afterburner has a lower total pressure loss, while the flow rate of cavity is5.52%of total flow rate, the recirculation zone can be well formed in cavity, so the cavitycan be used as the pilot stabilizer.