To answer my own question....
1 Bump inlet design principle
Bump inlet is based on cone flow theory [5-7], using multiplication Wave machine principle design. Convert a cone into an equivalent Compressing the surface, the resulting flow field is still a conical flow, a cone shock Attached to the edge of the compressed surface (see Figure 3). Due to the cone flow itself Characteristics, there are normal and horizontal on the compressed surface of the Bump inlet To the pressure gradient, the combined effect of the two is equivalent to the presence of a passive surface Layer blowing device that blows most of the fuselage cover layer out of the intake port. In addition, there is no boundary layer on the Bump inlet.
Good performance can also be obtained by means of blowing and blowing/puffing measures.
Figure 3 Buff inlet "passing wave" principle configuration
2 Xiaolong Aircraft Bump Inlet Design Features
The Bump inlet design points are: Maximum Mach number Ma=1. 7, pre-compression drum package equivalent compression half cone angle is 20 °, height H = 11 km and determine the capture area; in Ma = 0.8 to 1.2
Within the circumference, the throat area is determined according to the flow rate at the maximum state of the engine. The Mach number of the throat is controlled at 0. 6～0. 7; 04 aircraft inner tube The road is also different from the 01 / 03 frame, for the station 6 146 mm The front compression body, lip cover and inner pipe profile were redesigned;
After the station is 6 146 mm, it is consistent with the original, so that The structural changes are small.
2.1 Integrated design of intake port and front fuselage
In order to reduce the resistance of the front fuselage and the thickness of the boundary layer, the front machine The body has been modified and the fuselage layer is removed. The inclined plane is changed to the curved surface (see
Figure 4), and the bulge profile is combined with the fuselage profile. Combined, the front fuselage shape is smoother.
Figure 4 Comparison of front fuselage profile changes
2. 2 lip design of the inlet
Unlike the straight lip design of the conventional air intake, Bump The lip of the airway is designed in a forward swept form with the lip adjacent to the fuselage Divided into peaks and valleys, which allows most of the boundary layer to be removed from the valley. The shape is shown in
Figure 2(c).
2. 3 further exclusion design of the surface layer on the compression drum pack
In order to better eliminate the boundary layer on the compression bulge, reduce the super Shock/surface interference at the speed of sound, compression bulge profile a method of combining a lateral pressure gradient design with a suction hole method, The suction holes are evenly distributed in the forward swept range of the lips, staggered.
2. 4 no venting door design
Because the Bump inlet uses a cone-shaped flow-passing design, the lip Three measures of mouth plucking and bulging and punching, and the surge of the intake port The degree is greatly increased, so there is no need to add a venting system.
3 Bump inlet flow characteristics
Drum symmetry plane pressure coefficient map calculated from CFD (see Figure 5) It can be seen that: the first shock compression shape of the Bump inlet The formula is progressive compression, the shock loss is small, and the total pressure is restored. Explicit cone flow characteristics; end shock angle and lip sweep angle To, and close to the lip, the wave is subsonic, should be a strong solution to the oblique shock.
Figure 5 Ma = 1. 7 inlet wave system structure (CFD calculation results)
Can be seen from the surface pressure distribution map of the bulge (see
figure 6), the pressure distribution on the bulge is: high intermediate pressure, pressure on both sides Low, the fuselage boundary layer is removed by the pressure gradient on the surface of the bulge.
4 Wind tunnel test analysis
High and low speed wind tunnels were carried out on the Bump inlet of the Xiaolong aircraft Test, test Ma range 0 to 1. 8, test model in the wind tunnel The photo is shown in Figure 7.
Bump inlet total pressure recovery coefficient and comprehensive distortion index
A comparison with the 01 / 03 swash plate inlet is shown in Figure 8. From the picture It can be seen that the total pressure recovery coefficient of the Bump inlet is superior to the supersonic speed section.
Figure 6 Ma = 1. 7 compression drum surface pressure distribution (CFD calculation results)
Figure 7 Bump inlet in high speed wind tunnel test
Figure 8 Inlet performance changes with flight Ma
Inclined plate inlet, e increased from 0. 02 to 0. 04, its comprehensive distortion index At the same level as the swash plate inlet, much lower than the engine distortion Limit requirements.
Figure 9 shows the Bump inlet oil flow test results, from the figure It can be seen that most of the fuselage boundary layer is discharged outside the outlet.
Figure 9 Bump inlet oil flow diagram
5 Conclusion
The design of the Bump inlet of the Xiaolong aircraft has reached the expected level. Purpose, the results of the wind tunnel test show: the performance of the Bump inlet Excellent, the total pressure of the inlet is restored high, compared with the swash plate inlet, e High 0. 02～ 0. 04; low comprehensive distortion index, good matching performance Well, work is stable and meets the requirements of aircraft and engines.
references:
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