Validation and modification of the Blade Element Momentum theory based on comparisons with actuator disc simulations

A comprehensive investigation of the Blade Element Momentum (BEM) model using detailed numerical simulations with an axis symmetric actuator disc (AD) model has been carried out. The present implementation of the BEM model is in a version where exactly the same input in the form of non‐dimensional axial and tangential load coefficients can be used for the BEM model as for the numerical AD model. At a rotor disc loading corresponding to maximum power coefficient, we found close correlation between the AD and BEM model as concerns the integral value of the power coefficient. However, locally along the blade radius, we found considerable deviations with the general tendency, that the BEM model underestimates the power coefficient on the inboard part of the rotor and overestimates the coefficient on the outboard part. A closer investigation of the deviations showed that underestimation of the power coefficient on the inboard part could be ascribed to the pressure variation in the rotating wake not taken into account in the BEM model. We further found that the overestimation of the power coefficient on the outboard part of the rotor is due to the expansion of the flow causing a non‐uniform induction although the loading is uniform. Based on the findings we derived two small engineering sub‐models to be included in the BEM model to account for the physical mechanisms causing the deviations. Finally, the influence of using the corrected BEM model, BEM_cor on two rotor designs is presented. Copyright © 2009 John Wiley & Sons, Ltd.     

Aerodynamic characteristics and thermal structure of nonpremixed reacting swirling wakes at low Reynolds numbers

The aerodynamic characteristics and thermal structure of uncontrolled and controlled swirling double-concentric jet flames at low Reynolds numbers are experimentally studied. The swirl and Reynolds numbers are lower than 0.6 and 2000, respectively. The flow characteristics are diagnosed by the laser-light-sheet-assisted Mie scattering flow visualization method and particle image velocimetry (PIV). The thermal structure is measured by a fine-wire thermocouple. The flame shapes, combined images of flame and flow, velocity vector maps, streamline patterns, velocity and turbulence distributions, flame lengths, and temperature distributions are discussed. The flow patterns of the no-control case exhibit an open-top, single-ring vortex sitting on the blockage disc with a jetlike swirling flow evolving from the central disc face toward the downstream area. The rotation direction and size of the near-disc vortex, as well as the flow properties, change in different ranges of annulus swirl number and therefore induce three characteristic flame modes: weak swirling flame, lifted flame, and turbulent reattached flame. Because the near-disc vortex is open-top, the radial dispersion of the fuel-jet fluids is not significantly enhanced by the annulus swirling flow. The flows of the reacting swirling double-concentric jets at such low swirl and Reynolds numbers therefore present characteristics of diffusion jet flames. In the controlled case, the axial momentum of the central fuel jet is deflected radially by a control disc placed above the blockage disc. This arrangement can induce a large near-disc recirculation bubble and high turbulence intensities. The enhanced mixing hence tremendously shortens the flame length and enlarges the flame width.     

Raising the Reliability, Efficiency, and Ecological Safety of Operation of the BKZ-210-140F Boiler Transferred to Stage Firing of Kuznetsk Coal in a U-Shape Flame

The BKZ-210-140F boiler of the West-Siberian Cogeneration Plant was equipped initially with four uniflow tangentially oriented burners and tertiary air nozzles. In order to raise the efficiency of operation and lower harmful emissions the boiler was reconstructed. U-shape aerodynamics was organized in the furnace by mounting 8 burners, 8 secondary air nozzles, and 8 tertiary air nozzles on the front and rear walls of the furnace. The reconstruction ensured higher stability of ignition of pulverized coal without flame division and rated temperatures of the superheater metal, lowered the optimum excess air factor at the outlet from the superheater to 1.2 – 1.25, decreased the concentration of nitrogen oxides in the combustion products to 360 – 380 mg/m³, and increased the gross efficiency of the boiler to 91.5 – 91.7%.     

机载布撒器翼身组合体亚音速气动特性计算

采用有限基本解方法对机载布撒器身组合体亚音速气动特性进行了数值计算。利用回转体对称特性，在体轴上布置线源和基元旋涡，模拟布撒器弹身的纵横向气动力。弹翼的升力问题采用涡格法，布置马蹄涡予以解决厚度问题用简化的线源模拟。     

建筑物周围风致静压场的分布及振动特性研究

对均匀流及湍流中风洞内有和无建筑物时的静压状况进行了研究,针对目前无法精确测量静压的情况,提出了一种无量纲化方法,给出了静压场的分布规律,运用幅值域及频域方法详细分析了建筑物周围各区域的流场特性,之后给出了静压场主要方向的分布函数型式,并推断了静压场的静力及动力边界。研究结果显示:在风洞中进行风压测试时,有可能激发风洞气柱自振模态并对测试结果产生误导;建筑物迎风区脉动主要取决于来流脉动;背风区脉动则与湍流来流脉动较为相像,但能引起更多非高斯特性;地面粗糙度由小变大时,建筑物侧风区脉动由小振幅周期振动向大振幅随机振动转变;地面粗糙度越大,静压场的静力作用越小而动力作用越大。所提静压场分布函数可对风工程实测参考静压的测试及建筑群体的风致干扰问题提供参考。     

Comparing different dynamic stall models

The dynamic stall phenomenon and its importance for load calculations and aeroelastic simulations is well known. Different models exist to model the effect of dynamic stall; however, a systematic comparison is still lacking. To investigate if one is performing better than another, three models are used to simulate the Ohio State University measurements and a set of data from the National Aeronautics and Space Administration Ames experimental study of dynamic stall and compare results. These measurements were at conditions and for aerofoils that are typical for wind turbines, and the results are publicly available. The three selected dynamic stall models are the ONERA model, the Beddoes–Leishman model and the Snel model. The simulations show that there are still significant differences between measurements and models and that none of the models is significantly better in all cases than the other models. Especially in the deep stall regime, the accuracy of each of the dynamic stall models is limited. Copyright © 2012 John Wiley & Sons, Ltd.     

A comprehensive preference-based optimization framework with application to high-lift aerodynamic design

An integral component of transport aircraft design is the high-lift configuration, which can provide significant benefits in aircraft payload-carrying capacity. However, aerodynamic optimization of a high-lift configuration is a computationally challenging undertaking, due to the complex flow-field. The use of a designer-interactive multiobjective optimization framework is proposed, which identifies and exploits preferred regions of the Pareto frontier. Visual data mining tools are introduced to statistically extract information from the design space and confirm the relative influence of both variables and objectives to the preferred interests of the designer. The framework is assisted by the construction of time-adaptive Kriging models, which are cooperatively used with a high-fidelity Reynolds-averaged Navier–Stokes solver. The successful integration of these design tools is facilitated through the specification of a reference point, which can ideally be based on an existing design configuration. The framework is demonstrated to perform efficiently for the present case-study within the imposed computational budget.     

基于FLUENT的某型空空导弹空气动力分析

FLUENT是目前功能最强大、适用范围最广、国内使用最多的CFD软件之一;对某型空空导弹建立了适当模型,并对其进行了非结构化网格划分;在不同舵偏角下,利用FLUENT软件对导弹模型气动力参数进行了计算。为导弹的控弹道计算提供有力的依据。     

火箭弹不同尾翼气动特性分析及优化

主要介绍了固定翼、卷弧翼和马刀翼3种常用的尾翼结构,并分别对固定翼、卷弧翼及马刀翼这3种不同尾翼的火箭弹进行了气动特性分析,分析结果表明马刀翼具有较好的气动特性;并进一步对马刀翼进行了气动优化分析。     

AFRL高超声速技术基础科研现状研究

首先对美国空军研究实验室(AFRL)研究高超声速技术的动机和挑战进行分析和讨论,随后梳理了AFRL对高超声速技术相关基础科研和试验的管理情况。结论认为在NHFRP计划的引导下,AFRL负责的项目之间形成相互支撑、验证和推动的总体形式。HIFiRE项目良好匹配了地面试验、数值计算和飞行试验之间的关系。STAR项目对一些国家级的技术演示验证项目提供了独到的见解和分析。这些研究形成的合力使美国的高超声速基础技术研究和项目不断进步。