Investigation On Mixing And Combustion Performances Of Lobe Forced Mixer For The Afterburner

With the development of aeronautical science and technology,the structure and combustion organization of the turbofan afterburner are gradually improved and perfected.Due to the high mixing feature,the lobed mixer is regarded to be one of the advanced mixers used in turbofan afterburner.The current study performed a numerical and experimental investigation on the asymmetric lobe mixer with center cone in front of afterburner.The influences of lobed geometric parameters on the aerodynamic mixing and combustion characteristics of the afterburner are analyzed.On a two-dimensional lobed forced mixer with an internal central cone,a series of model experiments are performed to investigate the mixing and combustion performances on an experimental setup simulating the afterburner.Besides,a conventional mixer is also adopted for comparison.The results show that the lobed forced mixer makes the distribution of total pressure and total temperature of the mixing flow between the primary stream and bypass stream tend to uniform along the passage height.The total l pressure loss produced by the lobed forced mixer is a little bigger than the conventional mixer.By using the lobed forced mixer,the combustion efficiency is increased approximately 10% related to the conventional mixer under the same fuel-air ratio.It is also revealed that the lobed forced mixer is benefit for improving the igniting and combustion stability.On a two-dimensional lobed forced mixer with an internal central cone,a series of numerical simulations are performed to investigate the effects of lobe angle on the mixing performance between inner primary flow and outer secondary flow for a non-symmetric lobe configuration.In the present,the half up-angle corresponding to the lobe peak is varied from 8? to 14? and the half down-angle corresponding to the lobe trough is varied from 20? to 35?.The results show that: besides a counter-rotating streamwise vortex pair with large scale commonly observed downstream of the lobe exit,an additional streamwise vortex pair is also induced near the lobe trough.The increase of lobe up-angle has a very weak influence on the total pressure recovery coefficient and improves the thermal mixing efficiency a little.The increase of lobe down-angle has a significant influence on the mixing enhancement,paying very little mixing loss.A numerical simulation is also performed on the combustion characteristics with the use of eddy dissipation model.The influences of lobed mixer geometric parameters on the combusting flow fields,such as fuel distribution,O2 distribution and pre-combustion temperature distribution and so on,are illustrated.The results show that the combustion efficiency is improved generally with the increase of the lobe width and the half down-angle corresponding to the lobe trough.As the increase of the half up-angle corresponding to the lobe peak,the combustion efficiency takes on complex variation,decreasing firstly and then increasing.