| The Turbine Based Combined Cycle(TBCC)engine is considered to be the most promising propulsion device of hypersonic vehicle at present with high unit thrust,broad flight envelop,reusability and other advantages.However,its main components,the multi-mode combustion chamber,faces many problems.This paper,deals with the problem of wide-range operating conditions,and researches the outer cavity stabilizer ignition as well as flame stabilization technology by means of numerical simulation and experimental research.The main work is shown below:The flow behavior of the outer cavity stabilizer and the outer cavity-radial groove stabilizer under different structural and flow parameters were investigated through numerical simulation.The results show that the size of the recirculation zone in the cavity increases with the increase of the length to depth ratio,while the variation of the trailing edge angle has less effect on the recirculation zone.The mass exchange rate of the cavity increases with the increase of ratio of length to depth,and decreases with the increase of edge angle and inflow velocity.For the outer cavity-radial groove stabilizer,the recirculation zone in the cavity after the radial groove decreases as the axial distance,S,between the trailing edge of the radial groove and the leading edge of the cavity decreases,and the vortex core moves outside the concave cavity as S decreases.When S is less than 0,the recirculation zone in the concave cavity disappears.The mass exchange decreases with the increase of S and the decrease of the sweep angle,and which is less affected by the flow parameters.The PIV flow field test results show that there is axial recirculation zone in the cavity of the outer cavity stabilizer with a structure of D =15mm,L/D =5 and θ =30 ° under the flow condition of V = 50m/s.The vortex center of the recirculation zone is located in front of the center of the cavity.The cavity mass exchange rate is 1.997%,and the return flow is 0.920%.The recirculation zone in outer cavity-radial groove stabilizer disappears when the system has a structure of S =0mm,β =20 °.In the radial groove central section,the air flows from the cavity along the radial groove rear wall to the axial center.The total pressure characteristics of the outer cavity stabilizer and the cavity-radial groove stabilizer were test-measured.Experimental results show that the total pressure recovery coefficient of the cavity stabilizer decreases with the increase of the flow velocity,and the structural parameters have little effect on it.The total pressure recovery coefficient of the cavity-radial groove stabilizer decreases with the increase of the velocity of flow,and increases with the increase of S.The ignition and blowout performance with different structure stabilizers under different flow conditions(V=50~150m/s,T=600~900K)were tested.The experimental results of the outer cavity stabilizer show that for the L/D =5 and 7 structure the flow rate increases,while the ignition equivalence ratio decreases,and for the L/D =3 structure the ignition equivalence ratio decreases and then levels.The equivalence ratio of ignition and blowout at low speed(V≤100 m/s)increases with the increase of flow temperature and L/D and decreases with the increase of the trailing edge angle.The cavity when L/D =3 has the lowest ignition and blowout equivalence ratio,and the cavity when L/D =5 has the widest range of ignition and blowout at high speed(V=150 m/s).The cavity when θ=90° has relatively low ignition and extinguishing equivalence,and the cavity when θ =30° has the widest range of ignition and blowout at high speed(V=150 m/s).Experimental results of the cavity-radial groove stabilizer show that the structure of S = 10 mm and β =20 ° is successfully ignited in all the incoming flows,and that the ignition equivalence ratio decreases with increasing velocity and increases with increasing temperature.Increasing the radial groove swept angle and reducing the spacing S is not conducive to ignition and flame stability in high speed and low temperature conditions,and increasing S is not conducive to flame propagation.Based on the research results of the cavity and radial groove stabilizer,a plan for the multi-mode combustion chamber structure is designed.The flow characteristics,fuel spray distribution and combustion characteristics of multi-mode combustion chamber under typical operating conditions were studied by the numerical simulation method.The results show that the low velocity recirculation zone is formed in the cavity under each working condition,which satisfies the flow conditions of ignition and flame propagation.The calculation results of the concentration field show that the fuel spray concentration in the cavity is 0.05 under different conditions,and that there are the local rich fuel zone and the lean zone downstream of the radial groove.The calculation results of temperature field show that the ignition is successful under all working conditions,and the flame in the cavity propagates along the radial groove to the medial axis of the burner after ignition;the flame connects successfully between adjacent radial grooves at 220 mm downstream of the radial groove. |
