Integrated Design of Aerodynamic Stealth for UCAV Considering Inlet and Exhaust System

doi:10.3969/j.issn.1009-086x.2026.03.011

Abstract

Abstract:

Aerodynamic performance and stealth capability are two critical objectives in the design of modern unmanned combat air vehicles （UCAVs）. This study develops parametric geometric models of the UCAV airframe， inlet， and nozzle through secondary development of CAD software， and conducts aerodynamic numerical simulations of integrated internal and external flow coupling using a 1D engine model. An aerodynamic-stealth integrated optimization framework is implemented through design of experiments （DoE） and surrogate modeling techniques for the UCAV airframe， inlet and exhaust system. The results demonstrate that the proposed optimization framework achieves significant improvements in both aerodynamic and stealth performance， validating its effectiveness in multi-objective aerodynamic-stealth optimization for aircraft with highly-integrated airframe-propulsion configurations. Furthermore， this methodology shows promising potential for accelerating design iterations and reducing developmental expenditures.

Key words: inlet and exhaust system design, integrated interior and outflow design, parametric modeling, one-dimensional engine model, aerodynamic stealth integrated design, unmanned combat air vehicle（UCAV）

摘要：

气动和隐身性能是现代无人战斗机（unmanned combat air vehicle, UCAV）设计的两大关键目标。利用几何建模软件的二次开发技术，建立了UCAV机体、进气道和喷管的参数化几何模型，利用一维发动机模型开展UCAV内外流一体化的气动数值模拟。采用设计实验（design of experiments，DoE）和代理模型对UCAV机身和进排气系统进行了气动隐身一体化优化设计。结果显示优化方案在UCAV气动和隐身性能上均有显著提升，能较好地应用于机体和进排气高度融合的飞行器气动隐身多目标优化，有望缩短设计周期减低开发成本。

关键词: 进排气系统设计, 内外流一体化设计, 参数化建模, 一维发动机模型, 气动隐身一体化设计, 无人战斗机

CLC Number:

Li ZHENG, Hanpu YU, Qixin ZHANG, Shuanghou DENG, Guoxu FENG, Yannian YANG. Integrated Design of Aerodynamic Stealth for UCAV Considering Inlet and Exhaust System[J]. Modern Defense Technology, 2026, 54(3): 115-130.

郑力, 虞涵普, 张祺忻, 邓双厚, 冯国旭, 杨延年. 考虑进排气系统的UCAV气动隐身一体化设计[J]. 现代防御技术, 2026, 54(3): 115-130.

Figures/Tables 41

Fig. 1 Definition of plane geometric shape parameters for airframe

Fig. 2 Comparison between clean configuration and inlet configuration

Fig. 3 Main parameters of the inlet shape of the intake duct

Fig. 4 Spline distribution of bulge shape control

Fig. 5 Cross-sectional shape and curvature distribution of the inlet duct

Fig. 6 Plane shape and parameters of nozzle

Fig. 7 Schematic diagram of cross-sectional area of nozzle inlet and outlet

Fig. 8 Parameterized generation model for intake duct

Fig. 9 Schematic diagram of separated exhaust turbofan engine structure

Fig. 10 RCS variation law with ka

Table 1 Optimization variables and ranges of the airframe

参数	下限	初始构型	上限
b/C₁	1.3	1.5	1.7
$χ 1$ /（°）	45	50	60
T₃/（°）	-8	-5	0

Table 1 Optimization variables and ranges of the airframe

参数	下限	初始构型	上限
b/C₁	1.3	1.5	1.7
$χ 1$ /（°）	45	50	60
T₃/（°）	-8	-5	0

Fig. 11 Aircraft body grids with different degrees of grid density

Table 2 Calculate the lift to drag ratio under different numbers of grids

网格数	L/D计算值
200万	16.44
320万	17.09
437万	17.08

Fig. 12 Electromagnetic calculation grid and incident wave distribution of the aircraft body

Table 3 Initial values and optimization range of variables for inlet and bulge optimization of intake duct

参数	下限	初始构型	上限
L_in/mm	500	800	1 200
H_in	0	0.4	0.8
H_gb	0	0.4	0.8
Z_y	0.2	0.5	1.0
$χ i n$	30	32	36

Table 3 Initial values and optimization range of variables for inlet and bulge optimization of intake duct

参数	下限	初始构型	上限
L_in/mm	500	800	1 200
H_in	0	0.4	0.8
H_gb	0	0.4	0.8
Z_y	0.2	0.5	1.0
$χ i n$	30	32	36

Table 4 Initial value and optimization range of variables for optimizing the internal passage of intake duct

参数	下限	初始构型	上限
A	-5	-4	5
A′	-5	-4	5
b₂	-16	0	4
c₂	-16	-15	4

Fig. 13 Tail edge of fuselage section under different control parameters Al，6

Fig. 14 Variation of lift to drag ratio of the Body with the control coefficient Al，6 of the section trailing edge

Table 5 Initial value and optimization range of variables for optimizing the internal passage of the nozzle

参数	下限	Baseline	上限
A	-10	0	10
A′	-10	0	10
b₂	50	60	70
c₂	50	60	70

Fig. 15 Establishment and optimization process of proxy model

Fig. 16 Optimization design framework based on ISGHT

Fig. 17 Sample distribution and feasible region for optimizing the organism

Table 6 Initial and optimized parameter combinations for each sample

参数	b/C₁	$χ 1$ /（ $°$ ）	T₃/（ $°$ ）
初始构型	1.50	50.00	-5.00
1#	1.56	54.40	-3.64
2#	1.54	53.91	-4.14
3#	1.54	53.45	-3.60

Table 6 Initial and optimized parameter combinations for each sample

参数	b/C₁	$χ 1$ /（ $°$ ）	T₃/（ $°$ ）
初始构型	1.50	50.00	-5.00
1#	1.56	54.40	-3.64
2#	1.54	53.91	-4.14
3#	1.54	53.45	-3.60

Table 7 Initial RCS calculation results for each sample combination

编号	L/D	RCS/dBsm
编号	L/D	400 MHz	2 GHz	10 GHz
Baseline	17.11	-5.27	-22.23	-29.41
1#	19.57	-4.39	-20.37	-30.06
2#	19.13	-5.69	-20.40	-29.40
3#	18.94	-5.32	-20.80	-30.00

Fig. 18 RCS distribution of the aircraft at a forward 90 ° azimuth angle in each frequency band

Fig. 19 Comparison of pressure distribution between optimized configuration and initial configuration

Fig. 20 Comparison of RCS distribution between optimized configuration aircraft and initial configuration aircraft

Fig. 21 Optimization samples and feasible regions for inlet and bulge parameters of intake duct

Table 8 Initial and optimized sample parameter combinations for intake duct inlet and bulge

参数	L_in	H_in	H_gb	$χ i n$	Z_x	Z_y
初始构型	800	0.40	0.40	30	0.50	0.50
1#	653	0.42	0.21	35.78	1.00	1.00
2#	667	0.40	0.29	30	1.00	0.98
3#	634	0.50	0.14	30.46	1.00	0.95

Table 8 Initial and optimized sample parameter combinations for intake duct inlet and bulge

参数	L_in	H_in	H_gb	$χ i n$	Z_x	Z_y
初始构型	800	0.40	0.40	30	0.50	0.50
1#	653	0.42	0.21	35.78	1.00	1.00
2#	667	0.40	0.29	30	1.00	0.98
3#	634	0.50	0.14	30.46	1.00	0.95

Table 9 Calculation results of initial and optimized sample combinations for inlet and bulge of intake duct

编号	L/D′	$σ$	DC₆₀
初始构型	15.10	0.957	0.29
1#	16.12	0.965	0.19
2#	15.99	0.961	0.13
3#	16.23	0.964	0.18

Table 9 Calculation results of initial and optimized sample combinations for inlet and bulge of intake duct

编号	L/D′	$σ$	DC₆₀
初始构型	15.10	0.957	0.29
1#	16.12	0.965	0.19
2#	15.99	0.961	0.13
3#	16.23	0.964	0.18

Fig. 22 Comparison of pressure distribution and streamline between optimized configuration inlet and initial configuration inlet

Fig. 23 Comparison of total pressure recovery coefficient distribution at the outlet section of the inlet duct between the imported and bulge-optimized Configurations and the initial Configuration

Fig. 24 Sample distribution of various parameters for optimizing the internal channel of the intake duct

Table 10 Comparison of initial and optimized configuration calculation results for the internal channel of the intake duct

组合	$σ$	DC₆₀
初始构型	0.945	0.34
优化构型	0.956	0.19

Table 10 Comparison of initial and optimized configuration calculation results for the internal channel of the intake duct

组合	$σ$	DC₆₀
初始构型	0.945	0.34
优化构型	0.956	0.19

Fig. 25 Comparison of Mach number and streamline between optimized internal channel configuration and initial configuration with symmetric cross-section

Fig. 26 Comparison of total pressure recovery coefficient distribution at the outlet of optimized and initial intake configurations

Fig. 27 Optimization configuration and initial configuration of Mach number and streamline distribution in each section of the inlet channel

Fig. 28 Comparison of cross-sectional area， curvature， and configuration centerline before and after optimization

Table 11 Comparison of Cfx results between initial and optimized nozzle configurations

组合	Cf_x
初始构型	0.683
优化构型	0.712

Fig. 29 Comparison of nozzle cross-sectional models and Mach number distribution before and after optimization

Fig. 30 Comparison of Mach number distribution on nozzle surface before and after optimization

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