运动通勤两不误:千里达平把公路车MIRA 3.0横向测评

车架几何构造--“瓜车”基因从头管角度、前叉的OFFSET值(偏移量)以及前后轮轴距,包括整个非对称后下叉、低重心五通等数据来看,MIRA 3.0为妥妥的“瓜车”无疑。长途耐力几何车架的优势在于舒适性、应用性好,尤其是拉长后下叉长度后稳定性更好。小后三角的优势被进一步拉大,而且整车搭配的4.0越野胖胎、铝合金胖圈组合,让越野性能进一步提升。整车的几何性能对比传统平把公路车更上了一个层级。

轮胎隔花磨损的原因及预防措施

奇怪的磨损现象 有一些小四轮拖拉机有时会出现轮胎“隔花磨损”的情况,即轮胎花纹不是均匀磨损,而是间隔着剧烈磨损。有时是一个轮胎隔花磨损。

CFD Simulation of Fixed and Variable Pitch Vertical Axis Tidal Turbine

In this paper, hydrodynamic analysis of vertical axis tidal turbine （both fixed pitch ＆ variable pitch） is numerically analyzed. Two-dimensional numerical modeling ＆ simulation of the unsteady flow through the blades of the turbine is performed using ANSYS CFX, hereafter CFX, which is based on a Reynolds-Averaged Navier-Stokes （RANS） model. A transient simulation is done for fixed pitch and variable pitch vertical axis tidal turbine using a Shear Stress Transport turbulence （SST） scheme. Main hydrodynamic parameters like torque T, combined moment CM, coefficients of performance Cp and coefficient of torque Cr, etc. are investigated. The modeling and meshing of turbine rotor is performed in ICEM-CFD. Moreover, the difference in meshing schemes between fixed pitch and variable pitch is also mentioned. Mesh motion option is employed for variable pitch turbine. This article is one part of the ongoing research on tm＇bine design and developments. The numerical simulation results are validated with well reputed analytical results performed by Edinburgh Design Ltd. The article concludes with a parametric study of turbine performance, comparison between fixed and variable pitch operation for a four-bladed turbine. It is found that for variable pitch we get maximum Ce and peak power at smaller revolution per minute N and tip sped ratio 2.

Effect of blade pitch angle on aerodynamic performance of straight-bladed vertical axis wind turbine

Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.

公路桥梁汽车的轮轴特征

论述了对公路桥梁汽车轮轴特征进行研究的必要性和汽车类型划分及轮轴特征参数的选取原则。针对实际公路上复杂多变的汽车轮轴重和轮轴距，介绍了对其概率分布进行统计推断的非线性最小二乘拟合的原理与数值实现方法，以及采用多峰正态分布对其进行拟合的可行性。由动态称重系统（WIM）从现场实测大量汽车的轮轴距和轮轴重量信息，对实际公路上的汽车轮轴特征进行统计分析，将汽车按轴数划分为2—6轴车辆，其中2轴车辆按照轴距进一步划分为2轴小车和2轴货车。以汽车总重、车长、各轴重与总重比值、各轴距与车长比值作为轮轴特征参数，根据各轮轴特征参数的概率分布类型，分别采用单峰、双峰或三峰正态分布进行拟合，给出各类型汽车轮轴特征的概率分布类型及和分布参数。