环绕式涡桨进气道主流道设计及优化方法

为研究环绕式涡桨进气道主流道设计方法,使用环形截面设计方法进行参数化设计,使用型线方程和3次B样条曲线构建进气道气动型面。使用数值模拟的方法,开展不同上、下型线参数方程和圆心扩展角变化规律对进气道性能影响的研究,通过调整参数得到进气道优化后的构型。结果表明：优化后得到的进气道模型相较于初始模型总压恢复系数提高0.13%,总压畸变降低8.4%。     

尾缘弯折角对宽攻角范围涡轮叶片气动性能影响的数值研究

采用数值模拟方法研究了涡轮尾缘弯折角对宽攻角叶型气动性能的影响,对比研究了尾缘弯折角和攻角变化对涡轮叶型载荷、出口气流角和损失系数的影响。计算结果表明:当攻角小于7°时,涡轮叶栅损失系数随尾缘弯折角增大而减小;当攻角大于7°时,涡轮叶栅损失系数随尾缘弯折角增大而增大。当尾缘弯折角一定时,涡轮叶栅损失系数先减小后增大,攻角为-23.35°处损失系数最小。随着攻角增加,出口气流角减小,叶片载荷后移。在全攻角范围内,尾缘弯折角增大,涡轮叶栅出口气流角增大,叶片载荷后移。     

非均匀来流下TBCC变几何进气道的数值优化

为提高内并联式涡轮基组合循环发动机进气道的工作特性,设计了一种带多级楔板的扩压段二维进气道。采用数值模拟方法研究了非均匀来流对其流场特性及性能参数的影响,并与非均匀来流对常规型进气道特性的影响进行了比较。模拟结果表明:采用带多级楔板的扩压段二维进气道性能受非均匀来流影响更小,扩压段内出口流场有明显的提升;模态转换状态下,与常规型进气道相比,进气道出口总压恢复系数平均增大10%,总压畸变指数平均降低15%左右,冲压出口马赫数均小于0.41,出口温升比降低。从而使得发动机推力增加,耗油率降低,改善了TBCC发动机的性能。     

肋片影响下的压气机静子叶栅流动特性研究

研究了肋片结构对带静子容腔的压气机静子叶栅的影响,采用数值模拟方法分析进气攻角及马赫数变化带来的流动性能变化。结果表明：增加肋片后,低能流体的发展变得复杂,有肋片时出口总压损失下降了4.53%,叶根处叶片载荷增大,叶根角区流场恶化得到缓解。从总体来看总压损失随攻角增大均有所增加,正攻角时叶根处流场性能严重恶化。随马赫数增加,100%轴向弦长处的总压损失逐渐增大,10%叶高处叶片载荷逐渐降低。     

一种曲面压缩的定几何宽速域进气道设计研究

对一种Ma=2.5～5.0范围工作的飞行器推进系统曲面压缩定几何进气道设计开展了初步研究,获得了该进气道的内外波系、流场性能及攻角特性,并对其前体构型做了相关研究。二维仿真模拟结果显示,采用曲面压缩设计的定几何进气道在Ma=2.5～5.0范围内均可正常工作,且具有较高的流量捕获能力;在二维构型基础上,开展了进气道三维构型设计,研究了攻角对三维进气道气动性能的影响,并对进气道三维构型开展了前体构型设计,对比分析了前体构型对进气道气动性能的影响。三维数值模拟结果显示,三维进气道同样可以在Ma=2.5～5.0范围内正常工作,但气动性能略低于二维流动情况;喉道总压恢复在α=-4°时达到极值; Case3的升阻比系数对于攻角变化较为敏感,在α<-4°时,Case3的升阻比系数占据优势地位。     

45°周向压力畸变对轴流压气机流动影响的试验研究

借助于某高速轴流压气机试验台,研究了45°周向总压畸变对轴流压气机转子绝对流动角的影响,初步探索了周向压力畸变引起的转子进口/出口绝对流动角变化的规律.结果表明,在45°周向总压畸变情况下,压气机转子的进口绝对流动角在周向受到影响的范围大约为90°(即畸变扰动区),转子出口的气流绝对流动角的畸变扰动区沿着周向大约为75°.气流绝对流动角在沿转动方向进入畸变扰动区时开始增加,在畸变网边缘达到正向最大值(与转动方向同为正);然后逐渐减小,在跨出畸变网的边缘得到负的最大值;随后又慢慢增加,跨出畸变扰动区.并且,随着换算质量流量的减少,转子进口绝对流动角变化不明显,而转子出口的绝对流动角则明显增加.     

某型无人机S型进气道流动特性研究

通过数值模拟研究了某无人机S型进气道,探讨了该型进气道在各种攻角和侧滑角下的流动情况。经过研究发现,此无人机S型进气道内部流动易分离,且随着攻角和侧滑角的变化,该进气道出口的气流流动更容易分离,旋流畸变很大,得出该S型进气道有抗攻角和侧滑角能力较小的特点。     

几何参数对S弯进气道气动特性的影响研究

采用数值仿真方法对某无人机S弯进气道内流场结构进行了分析,对出口截面流场特征及出口参数进行了研究。利用三维数值仿真方法,对几何参数对S弯进气道气动特性的影响进行了对比,其中包括S弯偏移距离和S弯进气道长度的影响。研究结果表明:S弯进气道内部存在典型的横向涡结构。S弯长度的增加会显著降低涡结构区域及分离区域,改善流场结构,同时提升出口总压恢复系数,控制出口畸变。     

大气雨浓度与飞行迎角对发动机风扇影响的数值研究

民机在降雨环境下的起飞和爬升过程中，雨水和飞行迎角耦合形成的复杂进气畸变对发动机性能有着不可忽视的影响，探究降雨浓度和飞行迎角对发动机风扇性能的影响具有积极意义。以某小型高涵道比涡扇发动机为研究对象，基于两相流原理，利用数值模拟方法研究了不同飞行迎角和大气雨浓度对进气道、风扇级的影响。结果表明，在适航规定要求的大气雨浓度和飞行迎角的共同影响下，飞行迎角增大使得雨滴在风扇各通道内周向分布不均匀，受进气总压畸变影响的通道内雨滴数目减少，非畸变区通道内雨滴数目增加，且迎角越大，雨滴分布越不均匀。雨水没有明显增强受总压畸变影响通道内的流场畸变程度，而是主要恶化总压畸变影响较弱区域的风扇和出口导叶的性能。     

雷诺数对风力机专用翼型气动性能影响的研究

雷诺数是影响翼型气动特性的主要参数之一,当雷诺数在5×10~5～1×10~7范围内变化时,基于N-S控制方程,对S827翼型在攻角α为-14°～45°范围内变化时的气动特性进行数值计算,研究了雷诺数对该翼型的升力特性、阻力特性、最大升力系数、最大升阻比、流动分离特性、失速特性等气动特性的影响.     

对旋式通风机性能试验分析

介绍了对旋式通风机的性能测试方法。并对其在相同流量的条件下，两级叶轮同时工作时的全压与每一级叶轮单独工作时的全压之和进行了分析、比较，从而为安全使用对旋式通风机提供了理论依据。     

冷气掺混对涡轮叶栅气动损失影响的试验研究

对某型涡轮平面叶栅,在不同的主流雷诺数下,以多种喷射方式和不同的流量比喷射冷气,研究型面压力分布及出口气流场参数的变化。试验结果表明,冷气入射对叶片表面静压分布几乎没有影响,只对冷气孔位置附近压力产生影响,相对来说,压力面入射冷气导致的变化小于吸力面。随进口马赫数升高,在相同的冷气流量比下流动总压降低。然而,在相同的马赫数下,随着冷气流量比增大,压力面入射跟吸力面入射导致的总压变化规律不一样。     

Total pressure fluctuations and two-phase flow turbulence in self-aerated stepped chute flows

Current knowledge in high-velocity self-aerated flows continues to rely upon physical modelling. Herein a miniature total pressure probe was successfully used in both clear-water and air-water flow regions of high-velocity open channel flows on a steep stepped channel. The measurements were conducted in a large size facility (θ=45°, h=0.1 m, W=0.985 m) and they were complemented by detailed clear-water and air-water flow measurements using a Prandtl-Pitot tube and dual-tip phase-detection probe respectively in both developing and fully-developed flow regions for Reynolds numbers within 3.3×10⁵ to 8.7×10⁵. Upstream of the inception point of free-surface aeration, the clear-water developing flow was characterised by a developing turbulent boundary layer and an ideal-flow region above. The boundary layer flow presented large total pressure fluctuations and turbulence intensities, with distributions of turbulence intensity close to intermediate roughness flow data sets: i.e., intermediate between d-type and k-type. The total pressure measurements were validated in the highly-aerated turbulent shear region, since the total pressure predictions based upon simultaneously-measured void fraction and velocity data agreed well with experimental results recorded by the total pressure probe. The results demonstrated the suitability of miniature total pressure probe in both monophase and two-phase flows. Both interfacial and water phase turbulence intensities were recorded. Present findings indicated that the turbulence intensity in the water phase was smaller than the interfacial turbulence intensity.     

Multi-objective optimization of an axial compressor blade

Numerical optimization with multiple objectives is carried out for design of an axial compressor blade. Two conflicting objectives, total pressure ratio and adiabatic efficiency, are optimized with three design variables concerning sweep, lean and skew of blade stacking line. Single objective optimizations have been also performed. At the data points generated by D-optimal design, the objectives are calculated by three-dimensional Reynolds-averaged Navier-Stokes analysis. A second-order polynomial based response surface model is generated, and the optimal point is searched by sequential quadratic programming method for single objective optimization. Elitist non-dominated sorting of genetic algorithm (NSGA-II) with ε-constraint local search strategy is used for multi-objective optimization. Both objective function values are found to be improved as compared to the reference one by multi-objective optimization. The flow analysis results show the mechanism for the improvement of blade performance.     

Numerical study on performance of supersonic inlets with various three-dimensional bumps

Numerical investigations were performed with a supersonic inlet system installed with a three-dimensional bump which was substituted for a diverter or conventional ramp-type compression systems at Mach 2. The modified inlets were designed to have two oblique shocks and a terminal normal shock followed by a subsonic diffuser, with a circular cross-section throughout. A numerical analysis was conducted to understand the three-dimensional flow field including shock/boundary layer interactions that occur around a three-dimensional bump and to evaluate the performance of the supersonic inlets. The current numerical simulations showed a bump-type inlet based on a conventional ramp-type inlet can provide an improvement in total pressure recovery downstream of the shock/boundary-layer interaction over a ramp-type inlet.     

跨声速涡轮级三维流场的数值模拟

采用FLUENT软件对某变循环发动机的高压跨声速涡轮级的三维粘性流场进行了数值模拟计算,使用混合平面法实现涡轮级动、静三维流场联算,计算中分别采用两个典型的双方程模型RNGk-ε模型和realizable k-ε模型,并将计算结果进行了对比,结果在一定程度上表明在分离流计算和带二次流的复杂流动计算中,Realizable k-ε模型的计算结果更精细一些.同时分析了其内部流场以及通道内总压损失的分布情况,为进一步改进叶型设计提供了理论依据.     

Simple heuristic to minimize total tardiness in a single machine scheduling problem

This paper discusses a simple heuristic to minimize the total tardiness in a single machine scheduling problem. The problem of minimizing total tardiness in single machine scheduling is a combinatorial problem. Hence, heuristic development for such problems is inevitable. In this paper, an attempt has been made to develop a simple heuristic, alternatively called greedy heuristic, to minimize the total tardiness in a single machine scheduling problem with n independent jobs, each having its processing time and due date. Further, its solution accuracy is compared with the optimal solution of a set of randomly generated problems using an ANOVA experiment. From the ANOVA experiment, it is observed that the solution of the simple heuristic proposed in this paper does not differ significantly from the optimal solution at a significance level of 0.05.     

Optimising Operating Conditions by Selection of Optimal Threshold Value for Digital-Digital Dynamic Characteristic

In this paper, three models for the establishment of the optimal operating conditions by selection of the optimal threshold value for digital–digital dynamic quality characteristic are provided. The optimal threshold value is compared with the threshold value of the Taguchi method and the following results are obtained. When either the standard deviation of the two distributions or the cost of the error of the two input signals are different, the optimal threshold value is better than the one provided by Taguchi. When the standard deviation of the two distributions and the cost of the error of the two signals are equal, the optimal threshold value is the same as the threshold value provided by Taguchi.     

LIMS项目成功的关键

站在系统工程的高度，对大连石化LabWare LIMS项目在软件选型、项目准备、项目目标制定及项目实施过程中一些很有特色的方法进行了剖析，这些对于LIMS项目的成功实施和应用具有普遍的指导意义。     

逆变器输出波形失真度的单片机测量研究

本文提出了利用单片机技术测量逆变器输出波形失真度的一种方法 ,导出了测量的数学模型 ,讨论了测试系统的硬件及软件结构 ,并研制成功了专用测试仪 ,实测结果表明这种测量方法简单 ,测量精度高