共查询到19条相似文献，搜索用时 218 毫秒
1.
机室开有通风口的土工离心机的风阻功率 总被引：3，自引：0，他引：3
基于旋臂与机室中气体的力矩平衡关系,导出了离心机的电机输出的总机械能向热能的转化关系,分析、找出了利用文献中已有公式计算土工离心机的风阻功率时,计算值比实际值偏小的原因,建立了机室开有通风口的土工离心机的新的随流比方程和风阻功率公式。采用新建公式和文献中相关公式计算了一台已建成的机室开有通风口的土工离心机的风阻功率,将计算数据与实际数据进行对比,表明本文的新公式避免了以前计算公式中的不足,能够大幅度提高风阻功率的计算精度。 相似文献
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《绵阳师范学院学报》2017,(11):1-7
土工离心机运行时会产生热量,热量引起机室内温度升高,会影响土工模型试验的效果,因此需要分析和控制机室温度.在顶板或侧壁开有通风口的土工离心机,由于运行时存在空气压力差和流速沿通风口方向的分量,机室内空气会自动由通风口排出,影响机室温度.基于一套土工离心机的实测转速、功率和机室温度数据,结合机室温度的理论公式,计算、分析了自然排风量及其效应和特征,给出了相应的结果 .比较不考虑与考虑自然排风量时的理论结果及实测结果,指出:自然排风量随转速增大而增大;自然排风对机室温度具有很强的影响;等效排风速度与通风口处空气旋转线速度之比基本不变,可作为自然排风的一个特征量.这些研究和结果为土工离心机机室温度的准确预估和通风设计提供了概念指导和理论依据. 相似文献
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为研究6061-T4铝合金方管压弯构件平面内稳定力学性能,建立ANSYS有限元模型,分析初始缺陷幅值和单元划分精度对数值计算稳定承载力的影响,并通过现有试验数据对ANSYS有限元模型加以验证。在此基础上,进一步分析构件长细比和荷载偏心率对构件稳定承载力的影响。将《铝合金结构设计规范》GB50429-2007压弯构件面内稳定计算公式得到的相关曲线与数值计算的相关曲线进行比较,发现规范公式偏保守较多。基于大量参数分析,建议对于强硬化铝合金,GB50429相关公式中修正系数η1改取0.8,将文中建议结果和数值计算结果进行比较,较原公式吻合更好。 相似文献
6.
对蜜蜂悬停飞行时二维柔性翅气动特性进行了研究．建立了昆虫飞行的4种坐标系,包括地面坐标系、贴体坐标系、固定翼坐标系和柔性翼坐标系,分别表示昆虫的位置、姿态、翅膀运动形式及变形．对4种坐标系间的变换进行了研究,并指出在二维刚性翅研究中利用椭圆坐标系可以提高计算精度,减少计算量．建立了二维柔性翅模型,分析了气动力、力矩及功率变化情况．对计算结果进行了分析,并指出扑动开始及结束阶段大的升力和阻力峰值的产生是平动加速、加速旋转及马格纳斯效应的叠加;小的峰值归因于凸向来流和凹向来流作用;与压力、压力力矩和平动功率相比,黏性力、黏性力矩及转动功率较小,可以忽略． 相似文献
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朱辉 《中学生数理化(高中版)》2012,(1):25-26
在近几年的高考试题中经常出现计算连接在电路中的用电器（白炽灯或电阻）消耗的实际功率问题．我们知道，连接在电路中白炽灯灯丝的电阻随通过其电流的增大而非线性增大，不能应用一般的公式计算白炽灯的实际功率，若采用由伏安特性曲线求用电器的实际功率则较为方便．下面谈谈由伏安特性曲线求实际功率的原理和方法，请同学们参考． 相似文献
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设计了基于物联网的农业环境数据收集系统,该系统使用支持向量机回归(SVMR)算法来处理原始数据,并预测日常空气温度、相对空气湿度和风速值,以帮助预测有害病菌在农田的传播。结果表明:预测的平均空气温度值和实际测量值平均绝对误差为1℃;预测的平均相对空气湿度值和实际测量值平均绝对误差为5%;预测的平均风速值和实际测量值平均绝对误差为1 km/h。该系统通过物联网访问环境数据,有助于田间作物管理人员更好地管理和预防病菌蔓延。 相似文献
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葛晓宏 《鹭江职业大学学报》2000,8(3):26-30
在[日]臼井英治切削温度场研究基础上，对直角自由切削温度场进行了探讨，建立起新的直角自由切削平均温度理论公式。经实验验证，基本解决了臼井体系理论公式计算值偏低于实际值的问题，为预测金属切削过程中的平均温度提供了更准确的途径。 相似文献
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为建立空气源热泵热水器COP随室外环境温度和水箱温度变化的动态模型,先测定了某一空气源热泵热水器随环境温度和水温变化的COP,引入了卡诺因子,得出了COP的拟合公式,并与测试数据进行了对比,对比表明COP的拟合公式精确度较高,能够满足实际工程应用需要。同时．为使该拟合公式对不同性能的空气源热泵热水器具有普适性,在上述公式的基础上引入COP修正系数,得出了适合不同性能空气源热泵热水器COP的拟合公式．经实验对比．表明该公式也能较好的满足实际工程应用需要。 相似文献
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本文探索了共轴直升机气动力参数估算技术,用以确定其疲劳载荷谱。首先给出了气动力计算的主控方程和数值方法,然后,分别建立了共轴直升机机身与旋翼的三维层流和湍流流场模拟的物理模型和计算网格模型,采用计算流体力学(CFD)方法,进行了共轴直升机机身与旋翼的层流和湍流流场数值模拟,估算了其气动力参数曲线,并对计算结果进行了分析对比,以检验建模技术的有效性,分析结果表明:该项技术实用可行,能得到一些与工程实际吻合的现象和结论。 相似文献
12.
JIANG Zhi-chao DOI Yasuaki ZHANG Shu-you 《浙江大学学报(A卷英文版)》2007,8(9):1414-1421
Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especially for the existence of dynamic stall. How to get better aerodynamic performance arouses lots of interests in the design procedure of a straight Darrieus wind turbine. In this paper,mainly the effects of number of blades and tip speed ratio are discussed. Based on the numerical investigation,an assumed asymmetric straight Darrieus wind turbine is proposed to improve the averaged power coefficient. As to the numerical method,the flow around the turbine is simulated by solving the 2D unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC (Marker-and-Cell) method is used. O-type grid is generated for the whole calculation domain. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine. 相似文献
13.
When aerodynamic braking works, the braking wings can change the flow field around the train, which may impact on the comfort
and safety. Based on a sliding mesh, the pressure wave and flow field around high-speed trains with aerodynamic braking are
analyzed. By comparing three typical intersection situations, the pressure wave of a high-speed train during braking (with
or without aerodynamic braking) is studied. The analyses indicate that the pressure wave around the high-speed train body
will change while using the aerodynamic braking, causing several pressure pulses on the surface of crossing high-speed trains.
The distances between the pressure pulses are equal to the longitudinal distances of the brake wings, but the magnitudes of
the fluctuations are less than those induced by the head of crossing trains. During the crossing, a train without aerodynamic
braking will not impact the crossing train. 相似文献
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S. P. Govinda Raju 《Resonance》2008,13(12):1107-1116
A study of air flow past simple bodies provides a background for the understanding and interpretation of aerodynamic forces
on airplanes. In this article some simple flows are studied by treating air as a viscous and compressible fluid subject to
the laws of mechanics. The importance of two dimensionless parameters, the Reynolds number and the Mach number, respectively
representing the viscous and compressibility effects is clearly brought out. The different flow phenomena associated with
specific ranges of the Reynolds and Mach numbers are indicated and explained. 相似文献
15.
Ananth Ramaswamy 《Resonance》2009,14(9):840-848
Eiffel is best remembered for engineering the tower that is a Paris landmark and bears his name. However, Eiffel has many
other firsts to his credit. He was one of the first to experimentally obtain material properties of wrought iron that permitted
him to proportion structural members in bridges and buildings that he built to sustain the service loads experienced by them.
Having struggled to get a good estimate of wind forces on the many tall structures that he designed and constructed during
his career, Eiffel was among the first to experimentally obtain data on fluid flow around an object and establish accurately
the drag on a body dropped in air in his later years. He developed one of the earliest versions of the ‘wind tunnel’ that
today plays a pivotal role in aerodynamic studies. This article traces the evolution of Alexandre Gustave Eiffel as an engineer
and scientist. 相似文献
16.
Xue-jun ZHANG Ke-qing ZHENG Ling-shi WANG Wei WANG Min JIANG Sheng-ying ZHAO 《浙江大学学报(A卷英文版)》2013,14(8):583-588
In this paper, a novel system using direct contact heat transfer between air and water solution was proposed to generate ice slurry. The heat transfer process and the system performance were studied; energy efficiency coefficients of 0.038, 0.053, and 0.064 were obtained using different solutions. An empirical relationship between the volumetric heat transfer coefficient Uv and the main parameters was obtained by fitting the experimental data. The Uv calculated from the empirical formula agreed with the experimental Uv quite well with a relative error of less than 15%. Based on the empirical formula, a laboratory-scale direct contact ice slurry generator was then constructed, with practical application in mind. If the air flow rate is fixed at 200 m3/h, the ice production rate will be 0.091 kg/min. The experimental results also showed that the cold energy consumption of the air compressor accounted for more than half of the total amount. To improve the system energy efficiency coefficient, it is necessary to increase the air pipes insulation and the solution＇s thermal capacity, and also it is appropriate to utilize the free cold energy of liquefied natural gas （LNG）. 相似文献
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以VDS-A01客车前空气悬架为研究对象,充分考虑了其他系统和外界条件对悬架计算结果精度的影响,计算了前空气悬架的刚度、固有频率和侧倾刚度,计算结果与实验结果相对偏差在3％以内,计算结果满足设计要求.该参数计算方法对客车空气悬架开发与设计具有良好的借鉴意义. 相似文献
18.
针对某型空地导弹机动性分析时气动参数的非线性特性,提出采用逐步逼近最终达到力矩平衡求解最大平衡攻角及可用法向过载的方法,解决了具有非线性气动特性导弹的可用法向过载计算问题,通过弹道仿真,对需用法向过载和可用法向过载进行了计算和对比．计算结果表明该导弹具有足够的机动能力,为总体设计和控制系统设计提供了依据． 相似文献
19.
雷玉勇 《重庆大学学报(英文版)》2003,2(1)
1. Introduction With the development of transportation, more and more road tunnels, especially the long tunnels, such as Erlangshan Tunnel (4176 m, China), Arlberg Tunnel (13972 m, Austria), Kan-etsu Tunnel (11055 m, South tube, Japan) and Laerdal Tunnel (24510m, Norway) have been built on the highway lines [1]. In a road tunnel, the exhaust gases given off by automobile engines, such as smoke, carbon monoxide (CO), oxynitride (NOx), hydrocarbon, etc., and dust produced by the passing a… 相似文献