Inverse design of low boom configurations using proper orthogonal decomposition and augmented Burgers equation

Mitigation of sonic boom to an acceptable stage is a key point for the next generation of supersonic transports. Meanwhile, designing a supersonic aircraft with an ideal ground signature is always the focus of research on sonic boom reduction. This paper presents an inverse design approach to optimize the near-field signature of an aircraft, making it close to the shaped ideal ground signature after the propagation in the atmosphere. Using the Proper Orthogonal Decomposition(POD) method, a guessed input of augmented Burgers equation is inversely achieved. By multiple POD iterations, the guessed ground signatures successively approach the target ground signature until the convergence criteria is reached. Finally, the corresponding equivalent area distribution is calculated from the optimal near-field signature through the classical Whitham F-function theory. To validate this method, an optimization example of Lockheed Martin 1021 is demonstrated. The modified configuration has a fully shaped ground signature and achieves a drop of perceived loudness by 7.94 PLdB. This improvement is achieved via shaping the original near-field signature into wiggles and damping it by atmospheric attenuation. At last, a nonphysical ground signature is set as the target to test the robustness of this inverse design method and shows that this method is robust enough for various inputs.     

等离子体射流作用下光壁面超声速燃烧室点火试验研究

针对光壁面超声速燃烧室的点火需求，利用中心嵌入式等离子体射流在模拟马赫数6，总温1860K的直连式试验台上实现了煤油燃料的可靠点火和稳定燃烧，研究了超声速燃烧室起动过程中等离子体建立与维持特征，获取了不同当量比下火焰传播与燃烧特性。试验表明：在自身工质的高压射流维持下，等离子体点火器可以在点火起动的不同压力变化环境中保持稳定；中心等离子体射流产生一定尺度的高温区域且含有丰富的自由基，但需要在恰当的中心喷油流量形成的混气当量比下产生等离子体诱导火焰；诱导火焰沿燃烧室轴向传播进而发展形成了稳定的超声速燃烧。     

多介质气体微小流量标准装置设计探讨CSCD

介绍了气体流量计量发展的特点及需求,提出建立一套多介质气体微小流量标准装置。结合实际装置指标需求,比较分析了常用气体流量标准原理特点,确定采用了PVTt法原理,根据设计指标需求及原理提出了多介质气体微小流量装置整体初步设计方案,并进行了测量不确定度分析。     

基于灰色模型的故障预测方法研究

随着人们对系统发生故障所带来财产损失、人员伤亡以及危害性的无法承受,故障预测与健康管理（PHM）技术应用越来越广泛。介绍了灰色模型,并利用某型号发控设备压控振荡器电路检测积分器输入信号检测的历史数据作为研究依据,验证了灰色模型在故障预测中的应用是可行的,准确度能够达到要求。     

水下超声速燃气射流气泡的生长及压力波传播特性实验研究

为获取燃气射流对上游水域的影响特性,采用燃气发生器和水下实验系统,研究了水下超声速燃气射流的气泡生长及演变过程,以及气泡压力波在水中的传播特性,并研究了压力波在水介质中的衰减规律。研究表明,燃气泡生长和"破碎"伴生着压力脉动在水介质中传播,气泡压力波的能量在水介质中快速衰减。     

污染空气对乙烯燃料超声速燃烧影响的试验

为了评估污染组分对乙烯燃料超声速燃烧性能的影响,利用西北工业大学电阻加热直连式超声速燃烧室试验平台,模拟飞行Ma=4条件下的燃烧室进口条件(总压pt=760kPa,总温Tt=800K,Ma=2),开展了来流分别为纯净空气和污染空气的乙烯燃料超声速燃烧对比试验。完成了当量油气比ER=0.57,来流分别为纯净空气和污染空气(CO2摩尔浓度分别为3%,7.5%,H2O摩尔浓度为7.5%)条件下的对比试验。试验匹配了纯净空气来流与污染空气来流燃烧室进口总压、总温、氧气摩尔浓度(21%)、Ma数与当量油气比。给出了燃烧室壁面压力分布对比试验结果与分析。     

射流推力矢量喷管中粒子运动轨迹的数值模拟

用颗粒轨道模型对基于激波控制的二维收缩-扩张(2-DCD)喷管中的气固两相流动进行了数值模拟,研究了1～60 μm不同直径颗粒的运动轨迹.研究表明,颗粒尺寸越小,粒子的随流性越好;颗粒尺寸越大,主流中的粒子与收缩段壁面碰撞越剧烈,无粒子区越大,二次流中的粒子对下壁面的碰撞越剧烈.     

晶振式非接触表面轮廓传感器的动态特性

从理论上对线性伸展模式的石英振子的动态特性进行了分析，讨论了在近场效应作用下，影响晶振品质因数的各种阻尼，并将所获得的解析模型与实验结果进行了比较。     

Numerical investigation on cavity structure of solid-fuel scramjet combustor

The influences of miscellaneous combustor structures for solid fuel scramjet combustion on the performance are investigated, including a detailed interaction analysis between shocks/waves and combustion. Hydroxyl-terminated polybutadiene is chosen as the solid fuel with the non-premixed equilibrium probability density function combustion model. The results show combustion enhancement when structure of combustor is modified. The radical emphasis is to examine the sensitivity of the properties due to variations on the length-to-depth ratio of cavity, aft wall angle, and offset ratio. It is noted that there is an appropriate structure of cavity (L/D=4, θ=45°, and D_d/D_u=1.25–1.5) regarding the combustion efficiency, total pressure loss and specific impulse. The observation of function for combustor components provides instructional insight into the design considerations for a combustor of a solid-fuel scramjet.     

超音叶栅激波结构研究及叶型优化设计

对于进口相对马赫数较高的超音叶栅,合理组织激波结构是设计中的重要课题.为探索削弱激波损失的途径,建立不同激波结构的计算模型,计算得到了激波结构对叶栅性能的影响规律和特点.为设计性能良好的超音叶型,利用叶型参数化方法构造出中弧线为“S”型预压缩叶型,实现叶栅通道内预压缩及一道斜激波加一道正激波增压;利用优化软件对上述叶型进行优化,叶栅性能提升明显;优化结果显示,正激波位置对超音叶栅性能有较大的影响.