三维参数化造型技术在圆柱齿轮方面的研究

以双渐开线斜齿轮为例,着重介绍了圆柱齿轮三维参数化造型的两种方法-扫描成型及范成法.对这两种方法在原理、步骤、效果等方面进行了深入的分析,指出了各种方法的优缺点及应用场合.     

滚切小螺旋角斜齿轮的原理与方法（二）

滚切β＜３°的小螺旋角斜齿轮，附加运动速度太小，使用普通机床调整方法，差动挂轮挂不上。本文通过对滚齿机滚切斜齿轮原理的分析，提出了滚切小螺旋角斜齿轮的方法以及机床调整精度的计算方法。     

大型发电机组可靠性预测方法与应用

提出发电机组可靠性预测的数学模型和预测方法.该方法在统计分析发电机组运行可靠性历史数据的基础上,确定检修系数的统计值与数学模型的待定参数.根据发电机组的计划检修天数与检修系数的数学模型,预测今后3年发电机组的等效可用系数.给出亚临界300 MW、超临界600MW、亚临界600MW火电机组和550 MW水电机组以及984...     

On the lateral instability of a thin beam under periodic bending loads

The lateral instability of a thin beam under periodic bending loads was investigated. Physical evidences of the instability were observed previously by experiments. But an analytical study has not been reported. The object of this study is to demonstrate the nature and existence of dynamic lateral instability. The harmonic balance method is applied to bifurcation modes which result from the stability change of torsional mode of a beam and then compared with numerical simulations. It is found, in a certain frequency range, that a small bending load results in the lateral instability when damping is small. Inha University     

蜗轮齿面积分温度的计算与分析

介绍了平面二次包络环面蜗杆传动齿面接触线上平均闪温的计算公式和蜗轮齿面积分温度的计算公式。分析了蜗轮齿面接触线上平均闪温及齿面积分温度的变化规律。     

基于SolidWorks的异形瓶转瓶螺杆设计

分件供送螺杆装置可完成规则或不规则的成批量包装容器的增距、减距、分流、合流、升降、起伏、转向、翻身等动作。基于SolidWorks软件,利用范成法原理完成复杂瓶形的转向螺杆设计。将操作过程模板化,直接修改对应的模型即可完成新瓶形的螺杆设计。通过对比分析转动加速度曲线,提供了一种合适的转动曲线。同时,对建模误差和输送平稳性进行了分析。     

一种抑制风电功率波动的直流侧电压控制方法

本文提出一种风力发电系统中抑制功率波动的控制策略。这种控制策略充分利用直流侧的储能元件,允许直流侧电压在一定范围内波动,从而抑制风力发电系统输出功率的波动,同时它也不影响风力发电系统的最大风能跟踪。仿真和实验都验证了这种控制策略的正确性。     

基于全控型变流器件的发电机组次同步振荡抑制方法

介绍一种采用全控型变流器件的发电机组次同步振荡抑制方法,该方法以发电机组的转速信号的变化量为控制量,将该转速信号变化量经控制器进行滤波、移相、比例放大、运算处理,得到以电压同步信号为基准控制变流功率单元的控制信号,使全控型变流装置产生次同步模态调制电流,该电流经功率传输单元影响发电机组的转速,达到抑制发电机组次同步振荡的目的。     

Optimization of China's generating portfolio and policy implications based on portfolio theory

This paper applies portfolio theory to evaluate China's 2020-medium-term plans for generating technologies and its generating portfolio. With reference to the risk of relevant generating-cost streams, the paper discusses China's future development of efficient (Pareto optimal) generating portfolios that enhance energy security in different scenarios, including CO₂-emission-constrained scenarios. This research has found that the future adjustment of China's planned 2020 generating portfolio can reduce the portfolio's cost risk through appropriate diversification of generating technologies, but a price will be paid in the form of increased generating cost. In the CO₂-emission-constrained scenarios, the generating-cost risk of China's planned 2020 portfolio is even greater than that of the 2005 portfolio, but increasing the proportion of nuclear power in the generating portfolio can reduce the cost risk effectively. For renewable-power generation, because of relatively high generating costs, it will be necessary to obtain stronger policy support to promote renewable-power development.     

Performance limitations in electric power generating systems imposed by high temperature corrosion

The increasing cost of fuel has resulted in a renewed interest in improving the efficiency of electric power generating equipment. In most cases, this involves increasing the maximum temperature in the cycle. Examples include the increase in gas turbine inlet temperatures, the increase in steam temperature and pressure in boilers and the move towards higher temperature gasification in combined-cycle plants. In all these cases, the limits are set by the properties of the available materials. Among these limiting properties, the high temperature corrosion resistance ofmetals and alloys is vel}' significant.

High temperature oxidation rates set an absolute limit, but there are processes which can lead to accelerated corrosion, often associated with impurities in the fuel or air, which lower the available temperatures still further. A number of specific cases are discussed, the underlying principles are outlined and methods of overcoming the various problems are suggested.