【作者】 张阳；

【导师】 周洲；

【作者基本信息】 西北工业大学 ， 飞行器设计， 2021， 博士

【摘要】 固定翼垂直起降飞行器以其灵活的起降方式和长续航、高速的优势备受军用和民用领域的青睐。尽管固定翼垂直起降技术已经发展了半个多世纪,但是其完全依赖动力系统实现垂直起降的方式却一成不变,由此带来的过大的动力代价和结构死重依然是固定翼垂直起降飞行器设计中亟需解决的问题。针对这一问题,本文尝试采用分布式动力与气动面强耦合设计来实现零来流条件下的动力诱导增升。首先对分布式涵道风扇的复杂流场特性进行研究,探索了低雷诺数、高湍流度流动的特征,发展了适合于多个涵道风扇-机翼耦合构型的数值模拟方法;其次通过大量的分布式“动力翼”构型布局参数的研究,对“动力诱导增升”的流动机理形成了深入的认知;再次分别对分布式涵道风扇-分布式诱导翼构型和翼上分布式涵道风扇构型进行了前飞/垂起多模态的气动耦合设计,大幅改善了动力系统/气动面耦合构型的拉力特性和气动特性;最后开展了耦合分布式动力的飞翼和鸭式-宽体构型三模态的数值模拟和流场分析,形成了“参数/部件气动影响——前/后分块气动特性——全机过渡策略”的设计思想,同时全机构型三模态的气动特性反映了“动力诱导增升”设计思想的可行性和有效性,对同类型的多分布式动力、多气动面、变构型固定翼垂直起降飞行器的气动设计具有一定的借鉴意义和参考价值。主要研究工作如下:（1）分布式动力诱导增升计算方法及流动特性研究。通过与实验数据的对比,验证并发展了适用于多个涵道风扇的耦合k-ωSST湍流模型求解RANS方程的多重参考系/动量源的高效、高精度的准定常数值模拟方法。对不同来流速度、风扇转速等工况下的涵道风扇计算模型进行了数值模拟,对比了涵道风扇拉力特性的变化,详细分析了喷流流场的轴向、径向、旋向速度分布、静压分布以及湍流度的分布。另外,针对剥离了涵道风扇旋转效应的二维低雷诺数、高湍流度特征的流动,发展了耦合γ-（?）_θt转捩模型求解RANS方程的数值模拟方法,通过不同雷诺数、湍流度下绕流流场形态、翼型压力分布、表面摩擦阻力系数等流动参数的对比,开展了雷诺数、湍流度、湍流度梯度等对翼型的气动影响研究,并通过翼型上的转捩和分离等现象进一步认识了涵道风扇的喷流对翼型绕流的气动影响。（2）分布式动力诱导增升构型中的布局参数影响研究。对涵道风扇-单机翼构型的气动特性和布局参数影响的研究,证明了动力诱导增升具有一定可行性。在此基础上,通过分别对分布式涵道风扇动力参数、分布式诱导翼的布局参数的研究,认识到动力诱导增升的效果主要来源于上游翼段对喷流的偏折而带来下游翼段安装角及升力的增大,动力诱导增升的效果仅取决于翼段对涵道风扇喷流偏折的程度,而与翼段的数量、尺度相关性不大;合理利用喷流的上/下区域可以获得一定升力特性的收益,但是由于喷流在翼面的摩擦损失,流动动能的耗散等,由喷流动能转化而来的诱导升力总是小于涵道风扇的净拉力。另外,对翼上涵道风扇的布局参数在有/无来流条件下气动特性的研究表明,涵道风扇通过对气流的抽吸和喷射作用对构型的气动特性起到了决定性作用:一方面被加速的气流能够使机翼获得额外的诱导升力,另一方面则弱化了涵道壁面对气流产生的阻滞效果,降低机翼的阻力。（3）前飞/垂起双模态下分布式动力与气动面强耦合的气动设计。在前飞模态下,通过缩短双侧机翼的间距、构造C型翼面、加长涵道唇口、收缩喷管等设计,提高了耦合涵道风扇的双层鸭翼构型的气动特性和拉力特性。通过涵道上侧短翼的下偏缩小涵道风扇喷管的截面积,通过半埋边界层吸入式机身的设计,在减小了构型迎风面积的同时增大了机身上表面曲率,获得了构型气动特性的提高。耦合涵道风扇的双层鸭翼构型在垂起模态下的气动特性也较好。通过喷流影响下的二维翼型优化,改善了诱导翼面的流动状态,并结合襟翼设计的思路,对三维的涵道风扇-诱导翼构型进行了气动验证对比,依据倾转策略,获得了更大的垂直起飞的竖直合力。（4）耦合分布式涵道风扇的全机构型三模态气动特性及过渡模态下的气动特性、动力配置/诱导气动面回收的策略研究。通过对耦合升力风扇-分布式涵道风扇的垂直起降飞翼构型三模态的气动特性研究,发现机身升力风扇的存在严重破坏了机身中部截面翼型的完整性,使得在各个模态下对全机的气动特性和流场特性都起到了非常不利的影响。基于此,进一步开展了对耦合半埋分布式涵道风扇的双层鸭翼-宽体诱导增升垂直起降改进构型三模态气动特性及过渡策略选择的研究。针对这种多动力、多气动面、变构型的固定翼垂直起降飞行器,在前飞模态下,涵道风扇动力的增大对全机的影响显著,在一定范围内变化时对全机的俯仰特性和纵向稳定性影响较小。在垂直起飞模态下,前后动力大小决定了全机的垂直起飞特性,相互间的气动耦合效果较弱;在离地高度超过平均气动弦长后,地面效应的影响较小。在过渡模态下,本文形成了“参数/部件气动影响——前/后分块气动特性——全机过渡策略研究”的设计思想。首先从气动特性、动力特性和俯仰稳定性等方面厘清了各参数、各部件在全机过渡过程中的气动影响,然后以分块划分的思路探讨了前/后动力的匹配关系和前/后气动面的回收策略,最后以满足上升力和俯仰稳定性的要求深入研究了全机的过渡策略,形成了该类垂直起降飞行器过渡模态具有参考价值的设计思想,很大程度上缓解了多参数影响带来的设计维度的剧增和计算代价过大的问题。更多还原

【Abstract】 Fixed wing vertical takeoff and landing aircraft is favored by military and civil fields because of its flexible takeoff and landing mode and the advantages of long endurance and high speed.Although the fixed wing VTOL technology has been developed for more than half a century,its way of realizing VTOL completely relying on the power system remains unchanged.The resulting excessive power cost and structural dead weight are still urgent problems to be solved in the design of fixed wing VTOL aircraft.To solve this problem,this paper attempts to use the strong coupling design of distributed power and aerodynamic surface to realize the power induced-lift under the condition of zero-speed flow.Firstly,the complex flow field characteristics of distributed ducted fan are studied,the characteristics of low Reynolds number and high turbulence flow are explored,and a numerical simulation method suitable for multiple ducted fan wing coupling configurations is developed.Secondly,through the large number of research on the configuration and layout parameters of distributed"power wing",a deep understanding of the flow mechanism of"power induced-lift"has been revealed.Thirdly,the forward flight/vertical takeoff dual-mode aerodynamic coupling design is carried out for the distributed ducted fan-distributed induced wing configuration and the distributed ducted fan configuration on the wing,which greatly improves the aerodynamic characteristics of the power/aerodynamic surface coupling configuration.Finally,the numerical simulation and flow field analysis of the coupled distributed ducted fan flying wing and canard wing-wide body configuration are carried out,and the design idea of"aerodynamic influence of parameters and components-the front/rear block aerodynamic characteristics-the transition strategy of aircraft"is formed.At the same time,the improvement of aerodynamic characteristics in three modes reflect the feasibility and effectiveness of the idea of"power induced-lift",which has reference value on aerodynamic design of VTOL airfcraft with mulit propulsions,multi aerodynamic surface,and variable configuration.The main research is as follows:I.Numerical simulation method of power rotating parts&Study on flow characteristics of low Reynolds number and high turbulence intensity.Compared with the experimental data,a suitable numerical simulation method of multiple reference frame/momentum source for distributed ducted fans is verified and developed,which coupled with k-ωSST Turbulence model to solve RANS equation.The calculation models of ducted fan under different flow velocity and rotation speed are numerically simulated,the changes of thrust of ducted fan are compared,and the axial,radial,rotational velocity distribution,static pressure distribution and turbulence distribution of jet flow field are analyzed in detail.In addition,for the two-dimensional flow with low Reynolds number and high turbulence intensity characteristics stripped of the rotation effect of ducted fan,a numerical simulation method is developed,which coupled withγ-(?)θ_ttransition model to solve RANS equation.Through the comparison of flow parameters such as flow field,airfoil pressure distribution and surface friction coefficient under different Reynolds numbers and turbulence intensities,the Reynolds number,turbulence intensity and turbulence gradient on the aerodynamic characteristics of airfoil is studied,and the aerodynamic influence of the jet of ducted fan on the airfoil is further understood through the phenomena of transition and separation on the airfoil.II.Layout parameters study on the power-induced-high-lift configuration of distributed ducted fan power-wing and configuration of distributed ducted fan on the wing.The study on the aerodynamic characteristics and layout parameters of ducted fan-wing configuration proves that the power induced-lift is feasible.Based on the original study,further study of the power parameters of the distributed ducted fan and the layout parameters of the distributed induced wing is launched.It is recognized that the effect of the power induced-lift mainly comes from the deflection of the upstream wing to the jet,resulting in the increase of the installation angle and lift of the downstream wing.And the effect of the power induced-lift only depends on the deflection of the wing to the ducted fan jet,It has little correlation with the number and scale of wing segments.Reasonable use of the upper/lower region of the jet can obtain certain benefits of lift characteristics.However,due to the friction loss of the jet on the wing and the dissipation of flow kinetic energy,the induced lift converted from the jet kinetic energy is always less than the net thrust of the ducted fan.In addition,the study on the aerodynamic characteristics of the layout parameters of the ducted fan on the wing with/without incoming flow shows that the ducted fan plays a decisive role in the aerodynamic characteristics of the configuration through the suction and injection of the air flow.On the one hand,the accelerated air flow can make the wing obtain additional induced lift.On the other hand,it weakens the blocking effect of the ducted wall on the air flow,and reduce the drag of the wing.III.Aerodynamic design of strong coupling between power system and aerodynamic surface under forward flight/vertical-takeoff dual mode.In the forward flight mode,the aerodynamic and thrust characteristics of the double canard configuration coupled with the ducted fan are improved by shortening the spacing between the two wings,constructing the C-shaped wing surface,lengthening the ducted lip and shrinking nozzle.Through the deflection of the short wing on the upper side of the duct,the cross-sectional area of the ducted fan nozzle is reduced.Through the design of the embed boundary layer injection fuselage,the windward area of the configuration is reduced,the upper surface curvature of the fuselage is increased,so that the aerodynamic characteristics of the configuration are improved.The double canard configuration of the coupled ducted fan also has good aerodynamic characteristics in the vertical mode.Through the two-dimensional airfoil optimization under the influence of jet,the flow state of the induced wing surface is improved.Combined with the idea of flap design,the aerodynamic verification and comparison of the three-dimensional ducted fan-induced wing configuration is carried out.According to the tilting strategy,a greater vertical resultant force for vertical takeoff is obtained.IV.Study on aircraft aerodynamic characteristics and strategy selection of forward flight/vertical-takeoff/transition multi-mode.By studying the aerodynamic characteristics of the three modes of the vertical takeoff fly wing configuration with lift fan and distributed ducted fan,it is found that the existence of the fuselage lift fan seriously destroys the integrity of the airfoil in the middle section of the fuselage,which makes the aerodynamic characteristics and the flow field characteristics of the whole machine extremely adverse under three modes.Based on this,a further research on the three mode aerodynamic characteristics and transition strategy selection of the double canard-wing wide body vertical takeoff and landing configuration is carried out.For this multi propulsions,multi aerodynamic surfaces and variable configuration fixed wing configuration,in the forward flight mode,the increase of ducted fan power has a significant impact on the whole aircraft,and has little impact on the pitching characteristics and longitudinal stability of the whole aircraft when it changes within a certain range.In the vertical takeoff mode,the front and rear thrust determine the vertical takeoff characteristics of the whole aircraft,and the aerodynamic coupling effect between them is weak.When the height above the ground exceeds the average aerodynamic chord length,the influence of ground effect is small.In the transition mode,the design idea of"parameter/component aerodynamic influence-front/rear block aerodynamic characteristics-whole machine transition strategy"is formed in this paper,which greatly alleviates the problems of sharp increase in design dimension and excessive calculation cost caused by the influence of multiple parameters.更多还原