Numerical simulation of effect of flow field on discharge characteristics in pressure relief door of nacelle
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摘要:
在采用NACA TN4007报告中的试验数据验证了CFD方法正确性的基础上，通过计算研究了不同来流马赫数、总压比、挡板开启角度对挡板排放特性的影响规律，并通过流场分析了形成这些规律的原因。结果表明：当总压比大于一定值后，相同总压比下排放系数（DFR）随来流马赫数的增加而下降，是因为在排放通道形成壅塞流量受限后所致。而在不同总压比下，排放系数随挡板阀开启角度增大而发生复杂变化趋势，究其原因是因为挡板阀开启角度变大造成排放通道实际最小喉道位置和型线发生变化，导致最小几何面积处的平均马赫数在不同速度区间调整变化，同时挡板上表面发生分离后的分离涡回流如果进入到最小截面处，还会造成排放流量的减小。
Abstract:On the basis of verifying the correctness of CFD method by using the experimental datum in NACA TN4007 report, the influence laws of different incoming Mach number, total pressure ratio and flap angle on the discharge pressure relief characteristics were studied through calculation, and the causes of these laws were analyzed through flow field. Results showed that when the total pressure ratio was greater than a certain value, the discharge flow ratio (DFR) decreased with the increase of incoming Mach number under the same total pressure ratio, due to the formation of choke-out in the discharge channel after the total pressure ratio promoted the discharge speed to transonic speed. The DFR increased to a certain value with the increase of the flap angle, and then began to fall back and then rose slowly, because when choke-out happened, the flap angel became larger, the average Mach number at the minimum geometric area of the discharge channel first lied in the subsonic section, then transited from the transonic section to the supersonic section, and then moved back to the transonic section and even the subsonic section. At the same time, the separated vortex reflux on the upper surface of the flap also reduced the DFR if it occurred at the minimum geometric area.
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Key words:
- nacelle /
- flap /
- pressure relief door /
- discharge characteristic /
- total pressure ratio /
- discharge flow ratio /
- choke-out
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图 3 试验装置计算半模网格及挡板局部放大
Figure 3. Computational half model grid and partial amplification of flap in experimental equipment
图 4 排放特性随网格数量的变化趋势
Figure 4. Varying trend of discharge characteristics with mesh number
图 7 将总压比Rp扩大至1以上的CFD计算结果
Figure 7. CFD calculation results of expanding the total pressure ratio Rp to more than 1
图 8 流场对称面的马赫数云图（Ma∞=0.55、Rp=0.88）
Figure 8. Mach number cloud on the symmetry plane of the flow field （Ma∞=0.55, Rp=0.88）
图 9 流场对称面的马赫数云图（Ma∞=0.7、Rp=0.88）
Figure 9. Mach number cloud on the symmetry plane of the flow field （Ma∞=0.7, Rp=0.88）
图 10 流场对称面的马赫数云图（Ma∞=0.55、Rp=1.4）
Figure 10. Mach number cloud on the symmetry plane of the flow field （Ma∞=0.55, Rp=1.4）
图 11 流场对称面的马赫数云图（Ma∞=0.7、Rp=1.4）
Figure 11. Mach number cloud on the symmetry plane of the flow field （Ma∞=0.7，Rp=1.4）
图 12 不同马赫数和总压比情况下的排放系数随挡板阀开启角度变化
Figure 12. DFR varies with the flap angle for different pressure ratios and Mach numbers
图 13 不同挡板阀开启角度时流场对称面的马赫数云图（Ma∞=0.4、Rp=0.9）
Figure 13. Mach number cloud on the symmetry plane of the flow field with different flap angles （Ma∞=0.4, Rp=0.9）
图 14 不同挡板阀开启角度时流场对称面的马赫数云图（Ma∞=0.4、Rp=0.97）
Figure 14. Mach number cloud on the symmetry plane of the flow field with different flap angles （Ma∞=0.4, Rp=0.97）
图 15 挡板阀开启角度时为45º时流场对称面局部放大马赫数云图（Ma∞=0.4、Rp=0.97）
Figure 15. Enlarged view of Mach number cloud on the symmetry plane of the flow field with flap angle of 45º （Ma∞=0.4, Rp=0.97）
图 16 不同挡板阀开启角度时流场对称面的马赫数云图（Ma∞=0.4、Rp=1.2）
Figure 16. Mach number cloud on the symmetry plane of the flow field with different flap angles （Ma∞=0.4, Rp=1.2）
图 17 挡板阀开启角度为45º时流场对称面局部放大马赫数云图（Ma∞=0.4、Rp=1.2）
Figure 17. Enlarged view of Mach number cloud on the symmetry plane of the flow field with flap angle of 45º （Ma∞=0.4, Rp=1.2）
图 18 挡板阀开启角度为15º时流场对称面局部放大马赫数云图（Ma∞=0.4、Rp=1.6）
Figure 18. Enlarged view of Mach number cloud on the symmetry plane of the flow field with flap angle of 15º （Ma∞=0.4, Rp=1.6）
图 19 挡板阀开启角度为20º时流场对称面局部放大马赫数云图（Ma∞=0.4、Rp=1.6）
Figure 19. Enlarged view of Mach number cloud on the symmetry plane of the flow field with flap angle of 25º （Ma∞=0.4, Rp=1.6）
图 20 挡板阀开启角度为40º时流场对称面局部放大马赫数云图（Ma∞=0.4、Rp=1.6）
Figure 20. Enlarged view of Mach number cloud on the symmetry plane of the flow field with flap angle of 40º （Ma∞=0.4, Rp=1.6）
图 21 挡板阀开启角度为45º时流场对称面局部放大马赫数云图（Ma∞=0.4、Rp=1.6）
Figure 21. Enlarged view of Mach number cloud on the symmetry plane of the flow field with flap angel of 45º （Ma∞=0.4, Rp=1.6）
表 1 不同网格数量下计算结果误差
Table 1. Calculation results error of different mesh numbers
参数 网格数量/万 网格理论收敛值 1037万网格与理论值误差/% 560 1037 2026 Cdr 0.441 0.434 0.430 0.422 2.9 Ct −0.202 −0.199 −0.1984 −0.1974 −0.8 Cm 0.204 0.201 0.198 0.195 2.9 
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