液氧/甲烷火焰和燃烧不稳定性试验

为了解液氧/甲烷火焰在外界扰动作用下的表现,增进对燃烧不稳定性的理解,分别对两种喷剪切同轴式喷嘴结构进行了试验,试验采用单喷嘴矩形模型燃烧室,液氧以液态从中心喷嘴喷注,甲烷以气态从同轴的环形腔喷注。试验中,压力调节装置上的齿轮间断性地堵住和打开安装在燃烧室底部和主喷管旁边的辅助喷管出口,分别向燃烧室输入高频扰动。采用高速照相机记录火焰的OH辐射量,并采用阴影和纹影技术记录液氧的喷雾过程。试验成功激发起了燃烧室一阶横向和一阶纵向振型,在高频扰动作用下,还产生了两次强低频振荡。讨论了分离火焰的特征及其液氧射流在外界扰动作用下的表现和影响参数。     

冷气喷射对直叶栅型面压力分布影响的实验研究

对一个具有典型涡轮导向器叶片型线的直叶栅,由叶片表面不同位置以不同的质量流量比喷射冷气,进行型面压力分布变化规律的实验研究。结果表明,前缘正对来流方向喷射冷气时压力变化较小。压力梯度和主流速度的不同使得压力面喷射冷气对压力分布的影响要小于吸力面喷射冷气时的情况。冷气射流对主流的滞止作用所造成的压力升高值比卵型涡导致的压力降低值小。从型面压力降低程度可以定性看出不同位置喷射冷气时卵型涡强度的大小。     

主燃孔对模型燃烧室流场的影响

为了深入了解主燃孔参数变化对双级轴向旋流器模型环形燃烧室内气流组织与气动性能的影响,采用PIV测速仪对该燃烧室内冷态和液雾燃烧流场进行测量,试验研究在冷、热态情况下不同主燃孔参数对模型燃烧室内回流区的形成、轴向平均速度u,轴向脉动速度Urms,雷诺剪切应力u′v′分布的影响。研究结果表明:主燃孔参数变化对燃烧室内冷、热态流场有着重要的影响;燃烧室在燃烧情况下所得的中心回流区长度要比冷态短,但回流负速度、脉动速度和雷诺应力都明显大于冷态,所得的研究结果可为燃烧室优化设计提供有用的依据。     

Consideration on aircraft tire spray when running on wet runways

The tire spray produced by aircraft running on wet runways may enter the intake of engines, which may lead to the compressor stall, surge, or even combustion flameout. Therefore, it is necessary to do some research work on the tire spray to help to solve this problem. Firstly, the mechanism of tire spray is analyzed, and some parameters are defined to describe the spray pattern. Secondly, the numerical model of tire spray is established by coupled Smoothed Particle Hydrodynamics (SPH) and Finite Element Method (FEM) in LS-DYNA software, and the model is validated by a simplified water spray experiment. Then some influence factors on the spray pattern are studied by numerical simulation. Finally, some suggestions are proposed on different types of aircraft to avoid too much tire spray being ingested into the engine intakes.     

Transient performance and intelligent combination control of a novel spray cooling loop system

Effective thermal control systems are essential for the reliable working of insulated gate bipolar transistors （IGBTs） in many applications. A novel spray cooling loop system with integrated sintered porous copper wick （SCLS-SPC） is proposed to meet the requirements of higher device level heat fluxes and the harsh environments in some applications such as hybrid, fuel cell vehicles and aerospace. Fuzzy logic and proportional-integral-derivative （PID） policies are applied to adjust the electronic temperature within a safe working range. To evaluate the thermal control effect, a mathematical model of a 4-node thermal network and pump are established for predicting the dynamics of the SCLS-SPC. Moreover, the transient response of the 4 nodes and vapor mass flowrate under no control, PID and Fuzzy-PID are numerically investigated and discussed in detail.     

喷射成形电子封装Si-Al合金凝固过程模拟研究

为了优化喷射成形Si—Al合金成形工艺，获得优良的显微组织，本文模拟了喷射成形Si-30wt％ Al合金的凝固过程。研究了雾化压力和沉积距离对熔滴冷却过程中的温度和固相分数的影响。模拟计算结果得到实验验证。     

旋流数对小限制率旋流喷雾及火焰特性的影响

分布式贫油直喷（Distributed Lean Direct Injection,DLDI）燃烧室是国外多点贫油直喷（MLDI）燃烧室的实用发展形式。本文对DLDI燃烧室的主燃级单元LDI开展研究,主要关注外旋流器旋流数（Sn）从0.65降低到0.33对流场、喷雾和火焰结构的影响。利用FLUENT软件、采用雷诺平均方程（RANS）对时均流场进行求解;利用离散相模型（Discrete Phase Model）对喷雾散布进行模拟;利用Mie散射和激光粒度测量仪对喷雾散布和SMD（Sauter Mean Diameter）进行测量,并对仿真结果进行验证;利用高速摄像机拍摄火焰结构。研究结果显示Sn变化直接改变流场结构：随着Sn的减小,外旋流射流对内旋流射流的压制逐渐变强,内旋流射流的张角和中心回流区尺寸都逐渐缩小;尤其在Sn为0.33时,角涡回流区演化成壁面回流区。流场变化影响液雾散布：Sn在0.38~0.65区间时,喷雾核心主要由内旋流射流输运,喷雾张角由内旋流射特性决定;当Sn为0.33时,喷雾核心会在自身惯性下射入外旋流射流,在外旋流射流以及壁面回流区的作用下均匀散布。喷雾散布结果表明喷雾核心射入外旋流射流时更有利于液雾的散布。火焰结构的研究结果显示在小限制率条件下,Sn为0.33时,中心回流区回流量不足、无法稳定火焰,此时形成的壁面回流区创造了新的稳火点来帮助稳定火焰。     

气泡雾化喷嘴液雾特性

为了研究静止空气中气泡雾化喷嘴的液雾特性，利用粒子多普勒分析仪(PDA)和Mie散射显示法，对气泡雾化喷嘴在水压2．5MPa和3．4MPa条件下，较宽气液比范围内的液雾的张角、粒度及速度分布进行了测量，分析了水压、气液比、两股射流相互作用对液雾的影响。结果表明，气泡对液体射流的雾化具有较大的增强作用，同时发现存在-临界气液比(介于3％～4％之间)，当气液比达到临界值后，射流的雾化突然增强，且运行稳定。     

直射式喷孔后方燃油浓度场计算及其分析

由于直射式喷油孔的结构简单、布置和调整方便,因此已被广泛地应用于冲压发动机的燃烧室中,而且喷孔后方的燃油浓度分布对火焰稳定及燃烧效率有很大影响,由此预知喷孔后方燃油浓度分布对喷孔布置、确定喷孔与稳定器的相对位置是十分重要的。根据试验结果,推导得到了直射式喷孔后方燃油浓度分布的计算公式,编制燃油浓度分布的计算程序,以分析直射式喷油孔后方的燃油浓度场分布。     

Spray characteristics of jet–swirl nozzles for thrust chamber injector

Thrust chamber injector is very critical component since that small differences in its design can result in dramatically different performance. This paper presents a preliminary investigation of a mono-propellant jet–swirl nozzle for thrust chamber using the existing commercial nozzle made of brass with little modification. The performance of two types of spray pattern, i.e. hollow cone and solid cone were investigated under cold flow test. Two solid cone injectors were studied at various purely axial orifice diameter with all other parameters remaining constant. This investigation reveals that decrease in the breakup length increased the spray angle. Higher injection pressure leads to shorter breakup length and higher value of discharge coefficient, except for hollow cone nozzle which shows mild fluctuating trend. Experimental data also tells that solid cone nozzle with diameter ratio 0.14 has the highest average discharge coefficient (0.60), followed by hollow cone nozzle (0.25). Solid cone nozzle with diameter ratio of 0.1 has an average discharge coefficient of 0.21.