Investigation On Design Methodology Of Hypersonic Inward Turning Inlets With Controlled Pressure Rise Law

The key of designing hypersonic inward turning inlet is to design its basic flowfield. A new kindof design methodology of axisymmetric basic flowfield with controlled wall pressure rise law isinvestigated using the rotational method of characteristics. Parametric study is performed to obtain thelaws of overall performance variation with design parameters of basic flowfield using pressure riselaw of two-order curve, and the effect of viscosity is also studied.With this design methodology of basic flowfield, in combination with streamline tracingtechnique, a circular inward turning inlet is designed and simulated numerically. Results show that theinward turning inlet can maintain the same law of pressure rise as its basic flowfield. The inlet withpressure rise law of pressure gradient increasing has the high compression efficiency, but low masscapture ratio, and the inlet with pressure rise law of pressure gradient decreasing is opposite.With basic flowfield based on the pressure rise law of three order curve, a hypersonic inwardturning inlet with rectangular to circular shape transition is designed and investigated with numericalsimulation and experimental method. The numerical results indicate that this inlet has weak leadingshock wave, and good overall performance. And the experimental results show that the inlet’s totalpressure recovery is0.45, it can generate a compression ratio of41.2and withstand a back pressureratio of200relative to the tunnel static pressure at Mach6with angle of attack of4degree.According to the investigation of three order curve law of pressure rise, the pressure rise law oftarc tangent curve is proposed. Numerical simulation is performed to study the performance ofaxisymmetric basic flowfield with this kind of pressure rise law. This curve has three parameters,whose effects on the performance parameters such as total pressure recovery, static pressure ratio,contraction ratio and internal contraction ratio was studied. Then, a circular inward turning inlet withthis basic flowfield is designed and numerically simulated to get the flow characteristics and totalperformance. The result shows this inlet has weak leading shock wave and small internal contractionratio, as well as high mass capture ratio and compression efficiency at both on-design point andoff-design conditions. In addition, a hypersonic inward turning inlet with rectangular to circular shapetransition integrated to a wedge forebody was designed and studied by numerical simulation, andtested in a hypersonic wind tunnel. Numerical results indicate that this inlet has high total pressurerecovery, mass capture ratio and good performance with angle of attack from Mach4to Mach7.Wind tunnel test data turn out that this inlet has similar pressure rise law as arc tangent curve, a totalpressure recovery of0.517, and a compression ratio of37relative to tunnel static pressure at Mach6. The starting performance with and without bleeding on top wall in the internal compression section isstudied at Mach5,8degree angle of attack. The results indicate that the inlet can not start withoutbleeding. But when the bleed slots in the zone where shock wave and boundary layer interaction ontop wall were open, the inlet can start with about1.2%mass flow rate of the flow entering the cowlclosure section lost.An innovative basic flowfield with controlled centre body is designed and studied, which ishelpful to weak the reflection shock wave and increase the compression efficiency. A circular inwardturning inlet using the new basic flowfiled is designed and numerically studied. The results indicatethe new inlet has weaker cowl shock wave/boundary layer interaction, better flowfield, highercompression efficiency, and better starting performance than the previous inward turning inlets. Basedon this new kind of baisic flowfield, a hypersonic inward turning inlet with rectangular to circularshape transition is designed and studied by numerical simulation, and tested in a hypersonic windtunnel at Mach6and Mach5. The inlet has a total pressure recovery of0.518, a compression ratio of52at Mach6with4degree angle of attack, and can start with about1.2%of the flow entering thecowl closure section lost at Mach5with8degree angle of attack.An inlet system with waveride forebody and hypogastric hypersonic inward turning inlets withrectangular to circular shape transition is designed and numerically simulated, the leading shock waveattaches to the leading edge of forebody at design point, the three dimensional flowfield produced bythe forebody make the inlets’ flowfield be asymmetric. Then another inlet system for hypersonicaircraft with waverider forebody and lateral hypersonic inward turning inlets is designed andnumerically simulated. The results indicate that, at high Mach numbers the external flowfiled offorebody is independent from the inlet’s internal flowfiled, but at low Mach numbers the shock wavesfrom forebody leading edge and inlet leading edge are coupling. Because the boundary layer does notenter the inlets, and then interactions of shock wave and boundary layer are weak, there is noseparation in the flowfield, which is helpful for improving compression efficiency, the L/D of the inletsystem nearly does not change with the free stream Mach number.