基于CFD技术的鼻腔输药的流动特性研究

鼻腔输药作为一种新颖的输药方式,具有方便可靠的特点,不仅可以适用于局部而且适用于全身用药,已经受到广泛的重视。但由于人类的呼吸道复杂的立体结构使得鼻腔输药成为生物医药研究的一个长期的挑战。利用CFD(计算流体动力学,Computational Fluid Dynamics)技术对鼻腔输药的流动特性进行研究,对一个基于真实的人类鼻腔解剖的3D模型的输药的流动过程进行了分析,着重研究了不同的药物颗粒的流动和沉淀特性。利用CFD的商用软件FLUENT在层流情况下对不同的密度、直径和流动速率的药物颗粒在鼻腔中流动进行了数值模拟,并对计算结果进行了比较分析。CFD研究的结果为鼻腔输药这种新颖的药物输送方式的优化设计提供了依据。     

Application of multi-objective optimization to axial compressor preliminary design

The axial compressor is one of the most challenging components for aero engine design. The highly complex and multi-disciplinary design process is built up from several separate design phases differing with respect to the number of details. Typically, meanline prediction is the first step of the aerodynamic design process where the goal is to provide a first guess and proper choice of basic design parameters. As a preliminary design procedure it is one of the most important parts of the compressor design process since a poor design decision on these parameters cannot be corrected by subsequent development efforts. The design of a compressor is always a compromise between contradicting requirements like high efficiency, low number of stages and high surge margin. This is typical for multi-criterion optimization problems requiring a high number of design analyses and a well-designed procedure for finding trade-off solutions. The paper will show how to automate a given Rolls-Royce preliminary design process in order to find Pareto-optimal trade-off solutions for design conditions. The aspect of process acceleration is also an important goal to release the design engineer from time-consuming parameter studies. Essential elements for speeding up the design process are the use of modern process integration tools, multi-criterion decision concepts, and nonlinear programming algorithms. Results will be shown based on a given Rolls-Royce compressor design for multi-objective optimization with respect to maximum efficiency, maximum surge margin, and maximum overall pressure ratio, where different deterministic and stochastic algorithms are used.     

Effect of protrusion amount on gas ingestion of radial rim seal

In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO₂ concentration and pressure, in order to obtain the optimal protrusion amount. The parameters of different dimensionless sealing flow were measured under the condition that the annulus Reynolds number was 4.39 × 10⁵ and the rotating Reynolds number was 1.05 × 10⁶. The results show that the change of the amount of protrusions has little effect on the static pressure in the cavity, and the static pressure change near the sealing ring is almost negligible. But the total pressure and sealing efficiency increase first and then decrease with the increase of the amount of protrusion. The variation of power consumption is the same. A complex vortex structure will appear at the high radius region when the protrusion is installed. On the other hand, the protrusion can effectively reduce the minimum sealing flow of the rotor–stator cavity. Furthermore, considering the sealing efficiency and power consumption, the best range of the protrusion amount is about 36. The ratio near this range can optimally balance the alleviation of the gas ingestion and the reduction of the power consumption.     

热力学排气系统中节流效应及其冷量利用分析

为更好地理解热力学排气系统(TVS)的运行机理，优化其运行参数，针对节流装置，建立了热力学模型，讨论了节流过程中状态参数的变化规律，对比了单相气体、单相液体节流的性能特性，进一步揭示了焦汤节流效应的原理，分析了不同节流背压下节流前低温工质(液氢和液氧)压力和温度对节流性能的影响，并结合TVS实际应用，阐述了节流最大制冷量的利用效果，提出了优化的TVS工作区间。研究表明：在节流过程不发生相变情况下单相气体节流制冷效应要比单相液体节流制冷效应更加显著；而在节流过程发生相变情况下液体节流至两相后，由于空化吸热导致流体温度降低，对于液氢，0.5MPa的压降可产生接近3 K的温降。对于液体节流，节流前压力对节流过程影响可忽略，〖JP2〗而节流前温度和节流背压对节流过程起主导作用；对于液氢在在轨运行工况下，考虑到节流制冷量的充分利用，同时保证换热过程体积含气率不高于90%，推荐TVS系统中节流背压范围为75～143 kPa。     

Experimental study on plasma jet deflection and energy extraction with MHD control

This paper presents an integrated research scheme for vector deflection and energy extraction in a gas plasma jet under Magneto-Hydrodynamic (MHD) control. A MHD-controlled thrust-vector test rig was used to conduct the experimental research. A gas plasma was obtained by injecting ionization seeds of Cs₂CO₃ into the combustion chamber via artificially forced ionization. The effects of the gas temperature and ionization seed mass fraction on the plasma jet deflection and energy extraction were experimentally verified under an applied magnetic field. The experimental results were analyzed theoretically. The results showed that the deflection amplitude of the gas plasma jet and the extracted voltage signal intensity increased with increasing gas temperature and the ionization seed mass fraction. The extracted dynamic voltage signals proved that the ionization seeds of Cs₂CO₃ induced gas ionization at 1173 K. The experiment verified that it is feasible to simultaneously achieve jet deflection and extract energy under the action of an external magnetic field.     

涡扇发动机极值限制保护闭环控制设计

现代高性能涡扇发动机采用分段组合多变量控制计划,以发挥发动机工作在整个飞行包线范围内的气动热力设计潜力。为保证发动机在过渡态工作的安全性,控制系统中必须考虑极值限制保护控制的设计问题。为避免直接限制保护控制引发的不同控制通道切换带来的系统震荡问题,提出1种高回路稳态增益的滞后-超前频域校正间接极值限制保护控制器设计方法,在保证限制回路足够的稳态精度和抗噪声能力的同时,又避免了引入积分环节导致相角裕度损失过大的缺点。通过发动机线性模型和非线性模型的控制系统仿真,验证了所述方法设计限制控制器的有效性。     

涡轴发动机双回路PI控制器多发功率匹配

为了应对多个发动机共同驱动同一直升机时,单个发动机性能衰退所引发的输出功率不平衡问题,以控制2个转子转速的双回路结构PI控制器为基础,将外回路改为直接功率控制回路,搭配能够计算旋翼在一定转速下需求功率的机载模型,构建了1种涡轴发动机多发功率平衡匹配控制系统.内回路分别采用燃气发生器转子转速控制回路和动力涡轮转子转速控制回路,得到参数不同的控制器并进行了仿真验证和对比.结果表明:所设计的双回路PI控制器能够在保证涡轴发动机动力涡轮转速恒定的同时,使性能衰退程度不同的2台发动机输出相同的功率.     

跨声速串列转子失速机制的数值研究

为了解决跨声速串列转子的低裕度问题,就必须了解跨声速串列转子的流场结构与失速机制.设计了叶尖切线速度为450m/s,负荷系数为0.56的高负荷跨声速串列转子.基于数值模拟的结果,分析了该串列转子在0.5mm叶尖间隙下的叶尖流场结构与失速机制,并在此基础上分别探讨了叶尖间隙和前、后排叶片周向位置对串列转子特性的影响和失速机制的变化.结果表明:前排叶片的叶尖区域是 影响串列转子稳定性的关键;随着叶尖间隙的增加,串列转子的失速机制也发生变化,从前排叶片叶尖区域的尾迹与径向潜流堵塞后排叶片通道转变为前排叶片叶尖泄漏流堵塞;在较大周向相对位置(后排叶片压力面周向远离前排吸力面)的情况下,串列转子获得最好的效果,随着周向相对位置(PP)的增加,失速部位从后排叶片转移至前排叶片.      

叶片反扭对跨声速大涵道比风扇性能的影响

使用基于流固耦合算法的叶片反扭程序,考虑了非定常气动力对叶片变形的非线性作用,研究了叶片反扭对跨声速大涵道比风扇性能的影响.以冷态叶型为起点,先计算离心力作用下的叶片变形,在此基础上使用流固耦合程序获得非定常气动力作用下的变形.考察了3个转速下叶片的动态变形对大涵道比风扇气动性能的影响.结果表明:在跨声速工况下,叶片表面激波位置的变化对叶片反扭角有很大作用,在考察的转速范围内,堵塞点使用设计叶型计算的流量大于动态叶型下的流量,数值达7%,将导致发动机起飞推力小于预测值.结果表明在大涵道比风扇设计阶段,预测气动性能使用准确叶型的重要性.      

基于虚拟样机技术的航空发动机放气活门机构仿真及故障分析

针对某型航空发动机放气活门机构主动摇臂的多起断裂故障,为寻找故障原因并尽可能缩短排故周期与降低排故成本.借助虚拟样机技术建立此机构的动力学仿真模型,利用动力学仿真软件ADAMS与有限元分析软件ANSYS的联合仿真分析,实现放气活门机构摇臂断裂故障再现,并找出断裂件受力的主要影响因素及其影响规律,估算各受力水平下断裂摇臂的疲劳寿命.最终,分别给出保证摇臂最低使用寿命与全寿命使用情况下的改进建议,即将摇臂与放气活门之间间隙B增大至0.273mm与0.279mm,从而为实际工程排故提供理论依据.