针栓式喷嘴喷雾燃烧特性研究进展

针栓式喷嘴具有深度节流、结构简单、燃烧稳定等优点,主要用于变推力液体火箭发动机。本文首先介绍针栓式喷嘴的工作原理和发展历程,紧接着总结针栓式喷嘴的雾化特性和燃烧特性,最后展望针栓式喷嘴未来的研究方向。目前针栓式喷嘴的雾化特性研究较多,重点分析了工况参数和结构尺寸对破碎形态、喷雾锥角、SMD、液滴速度等的影响,针对针栓式喷嘴液膜破碎机理的研究相对较少;针栓式喷嘴燃烧特性研究主要集中于燃烧流场结构、燃烧性能和热防护等方面,对针栓式发动机固有燃烧稳定性机理以及动态燃烧特性的研究还较为欠缺。     

局部规则涂层对气冷叶片测温影响的数值研究

为研究微细热电偶测温安装涂层对其测量精度的影响机理,基于气固耦合传热(CHT)方法,建立了接近真实气膜冷却叶片的三维模型,选择SST(shear stress transport) γ -θ湍流模型,对未喷涂氧化铝涂层与在叶片吸力面前缘、压力面前缘、压力面尾缘处喷涂氧化铝涂层后的气冷叶片表面温度进行数值研究。无涂层工况的数值计算结果与实验结果误差控制在5%以下,验证了数值方法的有效性。研究结果表明:涂层对近壁面燃气的流动特性产生显著影响;三种有涂层工况的数值计算结果表明,压力面前缘处比吸力面前缘处温差波幅小,且比压力面尾缘处测温误差降低35.5%;在压力面及吸力面前缘处,最佳测温区域为涂层中部至下端之间的部位,而在压力面尾缘处,最佳测温区域尽量选择靠近涂层上端部位。      

Effect of turbulence models on predicting convective heat transfer to hydrocarbon fuel at supercritical pressure

A variety of turbulence models were used to perform numerical simulations of heat transfer for hydrocarbon fuel flowing upward and downward through uniformly heated vertical pipes at supercritical pressure. Inlet temperatures varied from 373 K to 663 K, with heat flux rang-ing from 300 kW/m2 to 550 kW/m2. Comparative analyses between predicted and experimental results were used to evaluate the ability of turbulence models to respond to variable thermophys-ical properties of hydrocarbon fuel at supercritical pressure. It was found that the prediction per-formance of turbulence models is mainly determined by the damping function, which enables them to respond differently to local flow conditions. Although prediction accuracy for experimental results varied from condition to condition, the shear stress transport (SST) and launder and sharma models performed better than all other models used in the study. For very small buoyancy-influenced runs, the thermal-induced acceleration due to variations in density lead to the impairment of heat transfer occurring in the vicinity of pseudo-critical points, and heat transfer was enhanced at higher temperatures through the combined action of four thermophysical properties: density, viscosity, thermal conductivity and specific heat. For very large buoyancy-influenced runs, the thermal-induced acceleration effect was over predicted by the LS and AB models.     

进口边界层对采用弯叶片的平面扩压静叶栅流场性能的影响

给定不同型式的进口边界层,在两种不同亚音速条件下对一平面扩压静叶栅的弯叶片流场进行了数值模拟。结果表明弯叶片对扩压叶栅的改善的能力受进口边界层的特征影响。这种影响分为两个方面:(1)边界层厚度的影响和(2)边界层动量损失厚度的影响。边界层越厚或动量损失厚度越大,在低马赫数条件下弯叶片对吸力面角区密流增加越明显,从而更大程度地提高了端区的流动性能,降低了叶栅损失。在高马赫数条件下,若边界层越厚或动量损失厚度越大,角区密流虽变化不大,但因端区损失较大,其性能的提高会给叶栅总性能的改善带来较大的收益。      

Assembly Variation Identification of High Pressure Spool by Response Surface Based Model Updating Using IV-optimal Designs

This article, in order to improve the assembly of the high-pressure spool, presents an assembly variation identification method achieved by response surface method (RSM)-based model updating using IV-optimal designs. The method involves screening out non-relevant assembly parameters using IV-optimal designs and the preload of the joints is chosen as the input features and modal frequency is the only response feature. Emphasis is placed on the construction of response surface models including the interactions between the bolted joints by which the non-linear relationship between the assembly variation caused by the changes of preload and the output frequency variation is established. By achieving an optimal process of selected variables in the model, assembly variation can be identified. With a case study of the laboratory bolted disks as an example, the proposed method is verified and it gives enough accuracy in variation identification. It has been observed that the first-order response surface models considering the interactions between the bolted joints based on the IV-optimal criterion are adequate for assembly purposes.     

The Mercury Electron Analyzers for the Bepi Colombo mission

Bepi Colombo is a joint mission between ESA and JAXA that is scheduled for launch in 2014 and arrival at Mercury in 2020. A comprehensive set of particle sensors will be flown onboard the two probes that form Bepi Colombo. These sensors will allow a detailed investigation of the structure and dynamics of the charged particle environment at Mercury. Onboard the Mercury Magnetospheric Orbiter (MMO) the Mercury Electron Analyzers (MEA) sensors constitute the experiment dedicated to fast electron measurements between 3 and 25,500 eV. They consist of two top-hat electrostatic analyzers for angle-energy analysis followed by microchannel plate multipliers and collecting anodes. A notable and new feature of MEA is that the transmission factor of each analyzer can be varied in-flight electronically by a factor reaching up to 100, thus allowing to largely increasing the dynamical range of the experiment. This capability is of importance at Mercury where large changes of electron fluxes are expected from the solar wind to the various regions of the Mercury magnetosphere. While the first models are being delivered to JAXA, an engineering model has been tested and proven to fulfill the expectations about geometrical factor reduction and energy-angular transmission characteristics. Taking advantage of the spacecraft rotation with a 4 s period, MEA will provide fast three-dimensional distribution functions of magnetospheric electrons, from energies of the solar wind and exospheric populations (a few eVs) up to the plasma sheet energy range (some tens of keV). The use of two sensors viewing perpendicular planes allows reaching a ¼ spin period time resolution, i.e., 1 s, to obtain a full 3D distribution.     

FL-26风洞条带悬挂支撑內式天平研制

FL-26风洞条带悬挂支撑內式六分量天平采用管状结构的试验方案,有效地解决了天平的静校问题;天平内腔采用扁圆结构,有效地解决了天平轴向力元件处的强度和刚度问题,较好地降低了前后测量梁上下应变不对称的程度,同时增大了侧向力及偏航力矩的输出;用关于天平轴向对称布置的双铰链梁测量滚转力矩,提高了滚转力矩分量的测量精准度。本文主要介绍条带悬挂支撑內式六分量天平研制难点、解决方案及天平动校结果。     

液体静压导轨热特性有限元分析

为了减少超精密机床中液体静压导轨热变形对机床加工精度的影响,本文建立了液体静压导轨动导轨有限元模型,利用有限元分析软件ANSYS对动导轨在不同工作环境下做不同运动时的热变形进行仿真分析,仿真结果表明,当动导轨做高速变加速运动时,动导轨热变形较大,会对加工精度产生较大影响,为此,提出了降低液体静压导轨热变形的方法.     

紧凑布局核心机驱动风扇级设计参数影响分析

以某核心机驱动风扇级(Core driven fan stage,简称CDFS)的气动方案为例,使用新版Denton程序通过数值模拟分析了气动布局、预旋分布和转子径向负荷分布对CDFS性能的影响。数值结果表明:利用CDFS静子取代高压压气机进口导叶是一种紧凑高效的CDFS气动布局;CDFS效率所受的影响主要来自转子效率的变化,工作裕度所受的影响主要来自静子负荷的变化;增加CDFS转子叶根的设计压比可以降低CDFS静子叶根的气动负荷,从而使CDFS获得更为均衡的性能。     

PW400010级防涡管卡槽孔探工装开发

主要阐述PW4000发动机HPC10级防涡管卡槽孔探工装的设计思路和开发过程,介绍了开发成果的实际应用效果,并对开发过程中的经验进行了总结。