Research On Combustion Characteristics Of Solid Fuel Ramjet Effect By Swirl Flow

Solid fuel ramjet(SFRJ)has the characteristics of high specific impulse,long running time of engines,wide operating range,simple structure,high reliability,high safety and good economic Performance.For swirl-flow,the axial-momentum would decrease the tangential-momentum would increase compared with non-swirl flow.Due to the increasing of tangential-momentum the high intensity centrifugal force were produced.And centerline recirculation were generate.The reach of the influence of swirl intensity on combustion process in solid fuel ramjet,the working performance of SFRJ influenced by structure,stability of combustion in SFRJ influenced by swirl intensity were conducted.(1)For the study of issues discussed above,the swirler with adjustable swirl intensity were designed,and variable conditions of experiment were conducted by using High Density Polyethylene(HDPE)as fuel.The results reflect that for swirl operating condition the Carbon accumulation of surface is more serious than that of non-swirl operating condition,and distinct swirling characteristics was performed.The swirl flow could enhance the regression rate compared with non-swirl flow,and the swirl intensity would decrease at the middle and the end of fuel,and the regression rate at the middle and the end of HDPE would decrease.The stability of flame in swirl flow was affect by the step height of inlet,if the step height was too low,the engine might not work normally.With moderate step height,swirl flow could increase the stability of pressure in engine.(2)Simulation of steady for four conditions and simulation of unsteady for six conditions were conducted by using CFD code.The results indicated that for shorter HDPE bar,the mass fraction of O2 in swirl flow case was decreased gradually form upstream to downstream,which means the combustion becomes more efficiency,when the longer HDPE bar were used,the combustion near the surface was not efficiency than that of shorter case.(3)Comprehensive analysis the results of simulation and experiment,for swirl flow cases,the reattachment point moved forward than the case of non-swirl flow,higher temperature distribution and heat flux of fuel surface are both larger and higher than non-swirl flow cases.For swirl flow the relative position of reattachment point to the inlet of the chamber was not changing with the length of HDPE bar.However for non-swirl flow the reattachment point located at 50%of the total length,all changed with length of HDPE.According to the result of simulation,for 10mm step height,when the ignition process finished,temperature of chamber decrease,and recirculation zone was not stable,then ignition failed.For 15mm,20mm step height,when the ignition process finished,the recirculation zone was stable,and could be self-sustained burning.Under the operating condition of 70mm inner diameter and swirl number 0.6,the heat flux along the fuel surface and average regression rate was higher than the other operating conditions,for this operating condition reached the optimum combustion characteristics.