轴对称矢量喷管内流特性的模型试验

在喷管落压比1．5～17的情况下，对3组不同几何尺寸的轴对称矢量喷管模型试验件内流特性进行了试验。结果表明：气动矢量角与几何矢量角呈正比关系；当落压比小于设计落压比时，气动矢量角会出现大于几何矢量角的峰值，并随落压比的增加而逐渐趋近几何矢量角，推力系数并不随几何矢量角增加而显著下降，且与非矢量状态相当；矢量状态下，推力系数与面积比呈正比关系，而对喉道面积的变化不敏感。     

基于遗传算法和空间推进方法的单壁扩张喷管优化设计研究

 将单目标遗传算法和多目标遗传算法（包括NSGA-II和NCGA），与高效、高精度的空间推进流场数值模拟方法——SSPNS方法相结合，对二维超燃冲压发动机尾喷管即单壁扩张喷管（SERN）进行了气动优化设计研究。在巡航点（Ma=6.0）讨论了推力系数C_T最大单目标模型，推力系数C_T最大升力系数C_L最大两目标模型，以及推力系数C_T最大升力系数C_L最大俯仰力矩系数C_m最小三目标模型，分别得到了喷管的最大推力设计和关于多个目标性能的Pareto最优前沿。结果表明，扩张壁初始扩张角θ_r,i和外罩长度L_c对C_T影响较大；较小的L_c和较大的θ_r,i设计，将降低外罩内表面的负升力作用而使得SERN的C_L较大；较长外罩和较小的θ_r,i，对应Pareto最优设计的C_M较小。     

单边膨胀喷管气动和红外辐射特性数值研究

通过计算流体动力学/红外辐射(CFD/IR)数值模拟的方法,研究了单膨胀边倾角、喉道高度、侧壁长度和落压比(NPR)对单边膨胀喷管(SERN)气动性能和红外辐射特性的影响.研究结果表明:轴向推力系数随着单膨胀边倾斜角度增大而急剧减小,推力矢量角随着单膨胀边倾斜角度增大而增大;随着喷管落压比的增大,轴向推力系数先增大后减小,推力矢量角减小;随着喷管侧壁长度的增加,轴向推力系数可略微提高;单膨胀边对尾焰和喷管内壁有显著的遮挡作用,喷管下方的整体红外辐射仅为上方的10%左右;随着喷管落压比的增加,喷管上方的整体红外辐射降低.      

脉冲爆震发动机尾喷管的实验

选取3类10种有代表性的脉冲爆震发动机尾喷管进行了试验.研究结果表明, 各种喷管对性能均有提高;对每类喷管均存在一最佳面积比, 使推力增益最大;在受试的尾喷管中, 收敛-扩张喷管增益最大, 达24%;填充系数对喷管性能增益影响甚微.      

Thrust measurement method verification and analytical studies on a liquid-fueled pulse detonation engine

In order to test the feasibility of a new thrust stand system based on impulse thrust mea- surement method, a liquid-fueled pulse detonation engine （PDE） is designed and built. Thrust per- formance of the engine is obtained by direct thrust measurement with a force transducer and indirect thrust measurement with an eddy current displacement sensor （ECDS）. These two sets of thrust data are compared with each other to verify the accuracy of the thrust performance. Then thrust data measured by the new thrust stand system are compared with the verified thrust data to test its feasibility. The results indicate that thrust data from the force transducer and ECDS system are consistent with each other within the range of measurement error. Though the thrust data from the impulse thrust measurement system is a litter lower than that from the force transducer due to the axial momentum losses of the detonation jet, the impulse thrust measurement method is valid when applied to measure the averaged thrust of PDE. Analytical models of PDE are also discussed in this paper. The analytical thrust performance is higher than the experimental data due to ignoring the losses during the deflagration to detonation transition process. Effect of equivalence ratio on the engine thrust performance is investigated by utilizing the modified analytical model. Thrust reaches maximum at the equivalence ratio of about 1.1.     

Comprehensive optimization design of aerodynamic and electromagnetic scattering characteristics of serpentine nozzle

Comprehensive optimization design of serpentine nozzle with trapezoidal outlet was studied to improve its aerodynamic and electromagnetic scattering performance. Serpentine nozzles with different center offsets and different ratios of the bases of the trapezoidal outlet were generated based on curvature control regulation. Computational Fluid Dynamics (CFD) simulations have been conducted to obtain the flow field in the nozzle, and Forward-Backward Iterative Physical Optics (FBIPO) method was applied to study the electromagnetic scattering characteristics of the nozzle. Guarantee Convergence Particle Swarm Optimization (GCPSO) algorithm based on Radial Basis Function (RBF) neural network was used to optimize the geometry of the nozzle in consideration of its aerodynamic and electromagnetic scattering characteristics. The results show that the GCPSO method based on RBF can be used to optimize the aerodynamic characteristics of the internal flow and the scattering characteristics of the cavity of the serpentine nozzle with irregular outlet. The optimized model has a higher center offset and a lower ratio of the bases of the trapezoidal outlet after optimization compared to the original model. The optimized model leads to a slight change in aerodynamic performance, with a total pressure recovery coefficient increase of 0.31% and a discharge coefficient increase of 0.41%. In addition, the Radar Cross Section (RCS) decreases also by around 83.33% and the overall performance is significantly improved, with a decrease of the optimized objective function by around 38.74%.     

两相流环缝塞式喷管设计方法

 在常滞后两相流假设下,提出改进的Angelino理想型面法和改进的“二次曲线+三次曲线”造型法设计两相流环缝塞式喷管;计算了这两种改进方法设计的塞式喷管性能。算例表明:在两相流条件下与未考虑两相流效应的气相理想方法设计的型面相比，改进的Angelino法设计的型面长度缩短近33%，推力增大约1%；改进的“二次曲线+三次曲线”造型法设计的型面长度减小近6%，性能提高约4%。     

双S弯喷管的流固耦合特性研究

为了明晰S弯喷管的流固耦合特性,数值模拟了流固耦合作用下双S弯收敛喷管的结构变形特征及其内/外流特性。结果表明：S弯喷管的圆转方弯曲构型产生了非均匀的流场分布,并增强了结构的弹性特征,它们通过交换气动载荷与变形位移数据形成了S弯喷管流固耦合的作用机理。在气动载荷作用下,S弯喷管沿Y向的最大变形位移为25.3mm,它位于喷管出口上壁面的中心位置。当喷管的结构变形稳定时,第二弯转弯处下壁面的气流加速至局部超音速,壁面静压大幅降低;第一弯下游上壁面附近形成了气流分离区;喷管出口喷流沿轴向向上偏转。流固耦合作用导致S弯喷管的流量系数减小0.6%,推力系数降低1.8%。矩形截面与弯曲构型是影响S弯喷管流固耦合特性的主要几何特征,其中矩形截面能够显著增大喷管的变形位移;S形弯曲构型虽然能够有效抑制变形特征,但它导致喷管多个区域出现变形,喷管的结构变形分布变得更加复杂。     

涡轮发动机可调收扩喷管最优面积比

为了分析影响可调收扩喷管最优面积比的因素及其对最优面积比的影响程度,应用MATLAB软件对特定结构喷管的推力系数进行了最优值求解,得到了特定状态下喷管面积比的最优解(对应最大推力系数)。不同于传统的固定喷管,特定结构的可调喷管推力系数最大值并非对应完全膨胀状态,而是对应略微欠膨胀的状态。给出了使用这一优化结果的可调收扩喷管推力系数与使用1维等熵完全膨胀公式计算的推力系数的对比分析。结果表明:采用最优面积比的喷管具有更大的推力系数且对最优面积比影响较大的因素是可用落压比和喉道面积。     

叶栅稠密度及进出口气流角对反推性能的影响

导流叶栅几何及气动参数的选取直接关系到叶栅式反推力装置的性能,本文选取冲击式对称叶栅进行数值模拟,采用混合网格生成技术,研究叶栅稠密度、叶片进口气流角和出口气流角对轴向反推力系数和流量系数的影响。计算结果表明,叶栅稠密度在一定范围内变大时,流量系数减小,轴向反推力系数增加;在反推气流不被进气道吸入的情况下,当气流角增大,流量系数变大,轴向反推力系数降低。双曲非等厚叶片的气动性能要好于单曲等厚叶片。     

外形设计对微喷管性能的影响

利用直接模拟蒙特卡罗法对钟形、喇叭形和锥形等三种不同形状微喷管进行管内气体流动模拟,并对不同温度及入口压力下各形状喷管的性能变化进行模拟分析,模拟中采用与实际分子碰撞过程更为接近的内能松弛模型及CLL物面反射模型。研究结果表明钟形微喷管因扩张段回流区的存在,其推力性能明显低于喇叭形和锥形微喷管,锥形微喷管的推力性能同喇叭形微喷管较为相近。三种形状的微喷管推力值都随着入口温度的升高而降低,而微喷管的推力效率随着入口温度的升高而上升,入口压力的变化对微喷管推力有较大影响,但对微喷管的推力效率影响并不显著。     

Airside pressure drop characteristics of three analogous serpentine tube heat exchangers considering heat transfer for aero-engine cooling

This study explores the design, analysis, and air pressure drop assessment of three analogous air–fuel heat exchangers consisting of thin serpentine tube bundles intended for use in high Mach number aero-engines. In high speed flight, the compressor bleed air used to cool high temperature turbine blades and other hot components is too hot. Hence, aviation kerosene is applied to precool the compressor bleed air by means of novel air–fuel heat exchangers. Three light and compact heat exchangers in...     

Acoustic measurements of models of military style supersonic nozzle jets

Modern military aircraft jet engines are designed with variable-geometry nozzles to provide optimal thrust in different operating conditions, depending on the flight envelope. How- ever, acoustic measurements for such nozzles are scarce, due to the cost involved in making full- scale measurements and the lack of details about the exact geometries of these nozzles. Thus the present effort at Pennsylvania State University （PSU） in partnership with GE Aviation and the NASA Glenn Research Center is aiming to study and characterize the acoustic field produced by supersonic jets issuing from converging-diverging military style nozzles, and to identify and test promising noise reduction techniques. An equally important objective is to develop methodology for using data obtained from small- and moderate-scale experiments to reliably predict the full-scale engine noise. The experimental results presented show reasonable agreement between small-scale and medium-scale jets, as well as between heated jets and heat-simulated ones.     

球型收敛调节片喷管静态内性能数值研究

基于CFD数值计算软件,针对喉部宽高比为2.083的球型收敛调节片喷管,进行了矢量与非矢量状态下的内性能数值研究。考察了在不同俯仰和偏航矢量状态下,喷管推力系数、流量系数的变化及落压比对气动矢量角的影响。结果表明:俯仰和偏航两种矢量状态对喷管的推力系数、流量系数产生的影响都在3%以内。喷管的俯仰是通过同时转动上下扩张板来实现的,其与偏航作动相比表现出对性能更大的影响;另外发现在设计压比之前,气动俯仰角出现了随落压比先增大后减小的趋势,而设计压比之后渐渐趋于不变,基本和几何俯仰角相等,但落压比对气动偏航角却没有表现出太大的影响。     

二元收-扩喷管与球形收敛调节片喷管的性能对比研究

为了对比二元收-扩喷管(2DCD)与球形收敛调节片喷管(SCFN)的性能,基于CFD数值计算软件对2种喷管在相同工作点下进行了内外流场计算与分析。数值模拟结果表明:在相同高度及飞行马赫数条件下,SCFN的流量系数相较于2DCD呈现出较大不同,推力系数则略差于2DCD;在低落压比条件下,2种喷管内流对后体阻力特性影响不大;在高落压比条件下,2种喷管内流对后体阻力特性影响较大。     

固体火箭发动机反向喷管推力终止技术

本文讨论了打开反向喷管时推力终止过程的燃烧室压力衰减和推力瞬变的计算方法。对理论计算与试验结果进行比较,表明经过修正的理论计算结果与试验结果符合得较好。      

基于Kriging代理模型的单边膨胀喷管尾缘切角优化

在设计点落压比25和非设计点落压比15条件下,对单边膨胀喷管（SERN）不同尾缘切角模型进行了三维数值模拟,并采用Kriging代理模型以SERN轴向推力系数为目标,对尾缘切角进行多目标优化。研究结果表明:尾缘切角会影响SERN后气体的膨胀,增强流动的三维效应,恰当的尾缘切角会使SERN后气体更充分膨胀,有利于提高SERN的轴向推力系数,改善SERN的性能;通过优化,SERN的轴向推力系数由0.94达到了0.975以上,比优化之前提高了约5%,基于Kriging代理模型的SERN优化方法是有效的。      

超声速喷流啸声的控制方法

通过实验比较了几种超声速喷流啸声的控制方法,包括附加三角凸台和开V形槽的收敛喷嘴。实验结果表明,带三角凸台和V槽的喷嘴对啸声幅值有明显的抑制,尤其是凸台喷嘴对啸声的模态也产生了明显的影响,但是啸声成分仍然存在,并且在上游方向依然占主导地位。在此基础上提出了一种新的控制方法——凸台加V槽的组合喷嘴,实验结果表明,组合喷嘴完全抑制了啸声,而且对于其它超音速喷流噪声成分的幅值也有一定程度的降低。最后还对各种结构喷嘴的气动推力损失进行了综合评估,结果表明组合喷嘴的推力损失介于V槽喷嘴和三角凸台喷嘴之间,平均推力损失在3%左右。     

轴对称分开排气喷管改混合排气喷管设计方法

为将涡扇发动机轴对称分开排气喷管改型设计为混合排气喷管以获取混合推力增益且改变其红外辐射(IR)特征,提出了一套基于CFD数值计算评估的轴对称分开排气喷管改型设计方法。研究结果包括:①提出了内、外涵气流不同程度掺混时推力的估算方法,估算值与真实值的误差在所研究参数范围内不超过0.005;②分析了内、外涵气流掺混对改型设计的影响,喷管外涵气流与内涵气流的总压比在0.8~1.5之间且掺混度大于0.1时混合排气最有可能产生推力增益,且掺混越好,增益越高;③轴对称分开排气喷管改型设计为带环形混合器的混合排气喷管后,推力系数增加0.0087~0.0126,而采用波瓣混合器时喷管的推力系数则增加0.0289;④相比于分开排气,混合排气喷管在0°~15°方向上的红外辐射强度有所增加,但在其他所有方位角上均大幅下降,最大降幅为77.5%。      

V型尾缘喷管流场特性数值模拟

模拟计算了一系列V型尾缘(Chevron)收敛喷管的详细涡结构(包括流向涡和展向涡)、引射系数、推力损失等性能,并与相关实验结果进行了对比验证。采用有限体积QUC IK格式和标准k-ε湍流模型,结合壁面函数求解雷诺平均的N-S方程。通过模拟计算与实验结果的对比,验证了计算方法的可行性。通过计算得出:V型尾缘喷管齿弯角越大,核心区长度越短,喷管出口下游的流向涡和展向涡的强度和尺度也越大。V型尾缘的齿弯角每增加1°,对应的喷管的堵塞比约增加0.98%,喷管的推力损失约增加1.71%,引射系数约增加3.45%。