基于流激振荡现象的流体动能收集技术研究

针对偏远地区及特殊场景下的低功耗无线传感节点电源维护不易的问题,该文对一种基于流激振荡现象的流体动能收集技术进行了研究,结合压电技术可实现流体动能转换至电能的过程。通过对流激振荡现象进行数值模拟及实验研究,分析了空腔结构中的流场及声场分布特性,探究了流体速度对声振荡频率及幅值的影响规律。利用COMSOL软件对声电转换过程进行仿真,实现了完整的流体动能-电能的转换过程。研究结果表明,在一定的速度条件下存在频率稳定的声振荡区间,可驱动压电换能装置输出频率稳定的电压,当气体流速为30.5 m/s时(相当于高压输气管道的流速范围),声场压力振幅可达6.12 kPa,对应的输出开路电压为2.62 V。当外接15 kΩ电阻时,最高输出功率可达0.29 mW。

垂直轴流体动能转换装置设计

"垂直轴流体动能转换装置"是一种叶片和回转轴都垂直设置的流体动能转换装置。它可以是风力机,也可以是水轮机。它的特征是能实现目前国内外所有同类装置中最高的转换效率。本文简单介绍了"水平轴螺旋桨式风力机"存在的一些缺陷,以及"垂直轴流体动能转换装置"可以获取很高风能利用率的原因。

利用流体动能充电的管道机器人的设计要求

输油管线常年运行，久而久之就会出现油垢、结蜡现象，影响石油的输送。本文针对管道机器人的工作环境提出了对管道机器人的设计要求。

流体环境中结构附加质量的计算

采用弱耦合法来分析流体与结构的耦合作用,探讨了流体环境中影响结构附加质量的因素,并推导了流体动能的计算方法.文中计算了椭圆柱体和平坦薄膜屋盖的附加质量,得到附加质量对薄膜结构的动力特性有重要影响的结论.

学科知识输出影响力分析: 基于交叉知识的学科归属度测度

[目的/意义]新文科建设背景下,量化与评价学科在科学体系中的影响力,有利于推动学科交叉融合发展及话语体系构建。[方法/过程]首先,从研究持续性、均衡性、关注度三方面构建知识的学科归属度测度模型;其次,引入流体动能理论,基于归属度构建目标学科知识输出动能模型,从知识输出密度和知识输出速度两方面综合识别此学科知识主要影响了哪些学科,进而分析目标学科影响力;最后,以图书情报学2017—2022年数据为例,进行实证分析。[结果/结论]对比发现提出的研究方法较同类研究具有一定优势,并识别到管理科学与工程等是图书情报学影响的主要学科,法学等受图书情报学影响呈上升趋势,自然科学受图书情报学影响较小,尤其理科。由此,提出学科影响力提升策略建议。

265 m^(2)烧结机提质降耗生产实践

为降低烧结机工序能耗,提高烧结矿产质量,柳钢在对265 m^(2)烧结机采取了厚料层烧结、微负压点火、漏风治理、提高环冷机余热利用等多项工艺协同改造。通过合理配矿、探索熟熔剂的配加比例,提高混合料料温和透气性;增加一、二混合圆筒提升条数量提高物料下落高度,加强混合料制粒效果;自主开发应用混合圆筒高动能流体在线清理系统,实现在线清理混合圆筒内结圈,提高了混合圆筒内物料填充率,同时杜绝了大块料跌落影响生产顺行的情况;将烧结机点火炉膛整体抬高170 mm,并在布料段两边增加边缘压料装置,使烧结机在不改变原有台车挡板高度的情况下具备厚料层烧结的条件;合理调节环冷机冷却风量,降低1段2段自然风鼓风量,增大余热发电返回环冷机的循环风量,避免因快速冷却造成烧结矿强度差;在环冷机卸灰阀间加装双层卸灰阀,减少风管积料;在环冷机烟罩上增加密封钢刷,减少烟罩和环冷机台车间的漏风,提高环冷机密封效果从而提高余热利用。改造后,烧结矿的产质量得到明显提高,工序能耗由48.6 kgce/t降低到45.2 kgce/t。

深腔流激振荡特性研究及能量采集初步分析

针对深腔流激振荡现象的内部声场特性及其流体动能利用方法进行了研究,通过对谐振空腔内部的流场和声场进行数值模拟,探究腔体结构尺寸和流速对内部声振荡响应特性的影响,选用合适的空腔结构安装压电换能器初步实现声电能量转换过程,并进行实验验证。结果表明,当谐振腔开口尺寸H_(R)=30 mm,长度L_(R)=230 mm时,可在相当于高压输气管道的流速范围内获得属于第一水力模态和第一声学模态的稳定声振荡;当气体流速为32.26 m·s^(-1)时,声场压力振幅可达4.62 kPa;选用压电陶瓷厚度hp=1.0 mm的压电片进行实验测试,可得开路电压为1.99 V;实验结果与模型预测结果趋势一致。该方法丰富了环境流体动能的利用方式,且有望在低功耗、远距离、低维护等特殊场合的微型无线电子设备中实现无源供电。

基于解析复势的Joukowski翼型的附加质量

附加质量是影响水下运动物体受力的重要参数之一。为了高效准确地计算无限域理想流体中Joukowski翼型的附加质量,在推导出基于势流理论的流场复势解析解后,采用复变函数计算流体动能,并根据流体动能与附加质量的关系求解物体的附加质量。通过计算单个圆柱在无限域理想流体中运动的附加质量,验证了采用此方法的便捷性和准确性。运用这个动能推导公式着重研究了不同形状的Joukowski翼型以任意攻角运动的附加质量,得到翼型厚度参数R/a、弧度参数β及翼型运动方向α与附加质量的关系。计算结果表明:水平运动即(α=0)时,Joukowski翼型的附加质量随着R/a、β的增大而增大;竖直运动即(α=π/2)时,附加质量随着R/a的增大、β的减小而减小;除α=0、α=π/2外,此方法还能计算机翼以任意其他攻角运动时的附加质量,具有很好的适用性。

Numerical Simulation of a Planing Vessel at High Speed

Planing vessels are applied widely in civil and military situations.Due to their high speed,the motion of planning vessels is complex.In order to predict the motion of planning vessels,it is important to analyze the hydrodynamic performance of planning vessels at high speeds.The computational fluid dynamic method（CFD） has been proposed to calculate hydrodynamic performance of planning vessels.However,in most traditional CFD approaches,model tests or empirical formulas are needed to obtain the running attitude of the planing vessels before calculation.This paper presents a new CFD method to calculate hydrodynamic forces of planing vessels.The numerical method was based on Reynolds-Averaged Navier-Stokes（RANS） equations.The volume of fluid（VOF） method and the six-degrees-of-freedom equation were applied.An effective process was introduced to solve the numerical divergence problem in numerical simulation.Compared with experimental results,numerical simulation results indicate that both the running attitude and hydrodynamic performance can be predicted well at high speeds.

Automatic Generation of the Planning Tunnel High Speed Craft Hull Form

The creation of geometric model of a ship to determine the characteristics of hydrostatic and hydrodynamic, and also for structural design and equipments arrangement are so important in the ship design process. Planning tunnel high speed craft is one of the crafts in which, achievement to their top speed is more important. These crafts with the use of tunnel have the aero-hydrodynamics properties to diminish the resistance, good sea-keeping behavior, reduce slamming and avoid porpoising. Because of the existence of the tunnel, the hull form generation of these crafts is more complex and difficult. In this paper, it has attempted to provide a method based on geometry creation guidelines and with an entry of the least control and hull form adjustment parameters, to generate automatically the hull form of plarming tunnel craft. At first, the equations of mathematical model are described and subsequent, three different models generated based on present method are compared and analyzed. Obviously, the generated model has more application in the early stages of design.

Combustion and energy balance of aluminum holding furnace with bottom porous brick purging system

For acquiring the details in aluminum holding furnace with bottom porous brick purging system,efforts were performed to try to find out the potential optimal operation schemes.By adopting transient analysis scheme and constant boundary temperature,combustion in the furnace was investigated numerically using computational fluid dynamics(CFD).The predicted gas temperature shows good agreement with the measured results,and the predicted energy distribution of the furnace is consistent with that obtained from energy balance experiment,which confirms the reliability of the numerical solution.The results show that as the fuel-air mixture temperature rises up from 300 K to 500 K,the energy utilization of the furnace could increase from 34.55% to 37.14%.However,as the excess air coefficient increases from 1.0 to 1.4,energy utilization drops from 34.55% to 29.56%.Increasing the combustion temperature is the most effective way to improve the energy efficiency of the furnace.High reactant temperature and medium excess air coefficient are recommended for high operation performance,and keeping the furnace jamb sealed well for avoiding leakage has to be emphasized.

Experimental Study on Hydrodynamics of L-type Podded Propulsor in Straight-ahead Motion and Off-Design Conditions

Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the authors for podded propulsors, a ship model towing tank, and under water particle image velocimetry （PIV） measurement systems. Under the three types of conditions, the main parameters of an L-type podded propulsor were measured, including the propeller thrust and torque, as well as the thrust, side force, and moment of the whole pod unit.In addition, the flow field on the section between the propeller and the strut was analyzed. Experimental results demonstrate that the dynamic azimuthing rate and direction and the turning direction affect the forces on the propeller and the whole pod unit. Forces are asymmetrically distributed between the left and right azimuthing directions because of the effect of propeller rotation. The findings of this study provide a foundation for further research on L-type podded propulsors.

Spray Evaporation of Different Liquids in a Drying Chamber--Effect on Flow, Heat and Mass Transfer Performances

Almost without exception literature data and modeling effort are understandably devoted to water as the sprayed liquid since it constitutes the most common liquid used in spray drying applications. In selected applications, however, the liquid making up the solution or suspension may not be water. The objective of this work is to examine the differences in flow patterns, thermal behavior and drying rates caused by different liquids having different thermo-physical properties spray into a spray dryer using a computational fluid dynamic model.Numerical experiments were carried out for water (base case), ethyl alcohol and isopropyl alcohol-the latter two as model non-aqueous liquids. The chamber geometry was cylinder type with a co-current axial pressure nozzle and also an axial central exit so that the configuration is two dimensional and axi-symmetric. It is shown that the liquid properties can have major influence on the thermal field, droplet trajectories, residence times and overall evaporation capacity when all parameters of the problem are held fixed. Deviations from the single phase turbulent airflow in the same chamber without spray are different for the three liquids examined.

Magneto-hydrodynamic flow of squeezed fluid with binary chemical reaction and activation energy

The present exploration is conducted to describe the motion of viscous fluid embedded in squeezed channel under the applied magnetics effects.The processes of heat and mass transport incorporate the temperature-dependent binary chemical reaction with modified Arrhenius theory of activation energy function which is not yet disclosed for squeezing flow mechanism.The flow,heat and mass regime are exposed to be governed via dimensionless,highly non-linear,ordinary differential equations (ODEs) under no-slip walls boundary conditions.A well-tempered analytical convergent procedure is adopted for the solutions of boundary value problem.A detailed study is accounted through graphs in the form of flow velocity field,temperature and fluid concentration distributions for various emerging parameters of enormous interest.Skin-friction,Nusselt and Sherwood numbers have been acquired and disclosed through plots.The results indicate that fluid temperature follows an increasing trend with dominant dimensionless reaction rate σ and activation energy parameter E.However,an increment in σ and E parameters is found to decline in fluid concentration.The current study arises numerous engineering and industrial processes including polymer industry,compression and injection shaping,lubrication system,formation of paper sheets,thin fiber,molding of plastic sheets.In the area of chemical engineering,geothermal engineering,cooling of nuclear reacting,nuclear or chemical system,bimolecular reactions,biochemical process and electrically conducting polymeric flows can be controlled by utilizing magnetic fields.Motivated by such applications,the proposed study has been developed.

Effect of fin attachment on thermal stress reduction of exhaust manifold of an off road diesel engine

The effect of fin attachment on the thermal stress reduction of exhaust manifold of an off road diesel engine(Komatsu HD325-6) was investigated.For doing this,coupled thermo-fluid-solid analysis of exhaust manifold of the off road diesel engine was carried out.The thermal analysis,including thermal flow,thermal stress,and the thermal deformation of the manifold was investigated.The flow inside the manifold was simulated and then its properties including velocity,pressure,and temperature were obtained.The flow properties were transferred to the solid model and then the thermal stresses and the thermal deformations of the manifold under different operating conditions were calculated.Finally,based on the predicted thermal stresses and thermal deformations of the manifold body shell,two fin types as well as body shell thickness increase were applied in the critical induced thermal stress area of the manifold to reduce the thermal stress and thermal deformation.The results of the above modifications show that the combined modifications,i.e.the thickness increase and the fin attachment,decrease the thermal stresses by up to 28% and the contribution of the fin attachment in this reduction is much higher compared to the shell thickness increase.

Simulation of Hydrodynamic Performance of Drag and Double Reverse Propeller Podded Propulsors

The unsteady performance of drag and double reverse propeller podded propulsors in open water was numerically simulated using a computational fluid dynamics （CFD） method. A moving mesh method was used to more realistically simulate propulsor working conditions, and the thrust, torque, and lateral force coefficients of both propulsors were compared and analyzed. Forces acting on different parts of the propulsors along with the flow field distribution of steady and unsteady results at different advance coefficients were compared. Moreover, the change of the lateral force and the difference between the abovementioned two methods were mainly analyzed. It was shown that the thrust and torque results of both methods were similar, with the lateral force results having the highest deviation

Theoretical Investigation on Internal Leakage and Its Effect on the Efficiency of Fluid Switcher-Energy Recovery Device for Reverse Osmosis Desalting Plant

This work is focused on the theoretical investigation of internal leakage of a newly developed pi lotscale fluid switcherenergy recovery device （FSERD） for reverse osmosis （RO） system. For the purpose of in creasing FSERD efficiency and reducing the operating cost of RO, it is required to control the internal leakage in a low level. In this work, the internal leakage rates at different leakage gaps and retentate brine pressures are investigated by computational fluid dynamics （CFD） method and validating experiments. It is found that the internal leak age has a linear relationship with the retentate brine pressure and a polynomial relationship with the scale of leakage gap. The results of the present work imply that low internal leakage and high retentate brine pressure bring benefits to achieve high FSRD efficiency.

Effect of Structural Parameters on the Performance of NS High-efficiency Composite TraysⅠ.The Effect of Aperture and Opening Ratio on NS High-efficiency Composite Trays

In this paper,the structure and characteristics of the NS high-efficiency composite trays based on the doublelayer aperture jet sieve plate and compositely structured packing were investigated.The effect of aperture and opening ratio of plate on the fluid dynamics of the NS high-efficiency composite trays,such as the dry tray pressure drop,the wet tray pressure drop,the entrainment,the froth height,the leakage and mass transfer characteristics,were investigated.As a result, the low pressure drop,the high efficiency and the high capacity are the main advantages of the NS high-efficiency composite trays compared to other types of trays.According to this study,small aperture is useful for reducing the pressure drop and entrainment with a high mass transfer efficiency;while large aperture can achieve high capacity and efficiency in a broader operating range at the same pressure drop and entrainment.

A new approach to quantifying vehicle induced turbulence for complex traffic scenarios

Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultimately the chemical and physical fate of pollutants by altering the conditions in the microenvironment. This study used a computational fluid dynamics(CFD) software FLUENT to model the vehicle-induced turbulence(VIT) generated on roadways, with a focus on impact of vehicle-vehicle interactions, traffic density and vehicle composition on turbulent kinetic energy(TKE). We show, for the first time, that the overall TKE from multiple vehicles traveling in series can be estimated by superimposing the TKE of each vehicle, without considering the distance between them while the distance is greater than one vehicle length. This finding is particularly significant since it enables a new approach to VIT simulations where the overall TKE is calculated as a function of number of vehicles. We found that the interactions between vehicles traveling next to each other in adjacent lanes are insignificant,regardless the directions of the traffic flow. Consequently, simulations of different traffic scenarios can be substantially simplified by treating two-way traffic as one-way traffic, with less than 5% difference in the overall volume-averaged TKE. We also developed equations that allow the estimation of the overall volume-averaged TKE as a function of the number and the type of vehicles.

Numerical simulation of effect of bionic V-riblet non-smooth surface on tire anti-hydroplaning

Inspired by the idea that bionic non-smooth surfaces(BNSS) can reduce fluid adhesion and resistance, and the effect of bionic V-riblet non-smooth structure arranged in tire tread pattern grooves surface on anti-hydroplaning performance was investigated by using computational fluid dynamics(CFD). The physical model of the object(model of V-riblet surface distribution, hydroplaning model) and SST k-ω turbulence model were established for numerical analysis of tire hydroplaning. With the help of a orthogonal table L16(45), the parameters of V-riblet structure design compared to the smooth structure were analyzed, and obtained the priority level of the experimental factors as well as the best combination within the scope of the experiment. The simulation results show that V-riblet structure can reduce water flow resistance by disturbing the eddy movement in boundary layers. Then, the preferred type of V-riblet non-smooth structure was arranged on the bottom of tire grooves for hydroplaning performance analysis. The results show that bionic V-riblet non-smooth structure can effectively increase hydroplaning velocity and improve tire anti-hydroplaning performance. Bionic design of tire tread pattern grooves is a good way to promote anti-hydroplaning performance without increasing additional groove space, so that tire grip performance and roll noise are avoided due to grooves space enlargement.