共线式热电发电机在侧面散热情况下的性能

热电材料是一种环境友好型功能材料,其可以实现热能与电能的相互转化,在热电发电、热电制冷中具有许多应用.传统的热电发电机为$\pi$型结构,要求热电腿的长度相等,在某些情况该结构不利于热电发电机的优化设计.热电发电机在高温工况下会引起强烈的热应力甚至应力集中,从而缩短了其工作寿命.另外,热电发电机的工作温度于环境温度,这样必然会有一部分热量散失到环境中,从而影响热电发电机的性能.针对该现象,本文建立了考虑散热的新型共线式热电发电机模型,该模型的热电腿可以独立进行优化,基于有限元方法,对考虑侧面散热的共线式热电发电机进行了仿真模拟,分析了其在狄利克雷边界条件下的热电性能和力学性能,得到了热电发电机的温度场、电势场、应力场,探究了不同强度的对流散热系数对热电发电机热电性能和力学性能的影响.结果表明,对流散热会降低热电发电机的能量转化效率,当对流换热系数达到~100W/(m$^{2}\cdot$\textcelsius) 时,效率为~0.0479,该值比绝热状态的转化效率0.066 7 低28%.对流散热使热电发电机侧面热损失增加,降低了热应力.在实际应用中,应合理优化设计隔热系统,提高能量的转化效率.      

Validation of reduced mechanisms for nitrogen chemistry in numerical simulation of a turbulent non-premixed flame

In this paper, the formation of nitrogen pollutants in computational fluid dynamics simulation of turbulent non-premixed flame was modelled by coupling reduced nitrogen chemical reaction mechanisms with comprehensive combustion model.     

主转动角与主转动轴的显式表示

本文利用Ｃａｙｌｅｙ＿Ｈａｍｉｌｔｏｎ定理,给出了两种直接获得转动张量显式表示的方法·一种为只含变形梯度较低次幂的表达形式,利用此表示,获得了主转动角的计算公式和主转动轴的显式表示·而另一种则是不含复杂系数且含变量个数较少的高效获得转动张量的方法·进一步,给出了主转动角和主转动轴的一些性质     

Synergistic improvement of fire retardancy and mechanical properties of ferrocene‐based polymer in intumescent polypropylene composite

The ferrocene‐based polymer (PDPFDE) accompanied with traditional intumescent flame retardant (IFR) system (ammonium polyphosphate (APP)/pentaerythritol (PER) = 3/1, mass ratio) has been used as additive flame retardant in polypropylene (PP), aiming to lower the total loading amount. The thermal stability and fire retardant properties were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical combustion (UL‐94), and cone calorimetry (CONE). The fire retardant mechanism was studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The results showed that the PP1 with 25 wt% IFR only passed the UL‐94 V‐1 rating, but the PP6 loaded by 0.5 wt% PDPFDE and 22.5 wt% IFR possessed an LOI value of 28.5% and passed the UL‐94 V‐0 rating; the peak heat release rate (pHRR) and total heat release (THR) are decreased by 63% and 43%, respectively, compared with pure PP. In addition, the char residue of PP6 manifested a very compact and smooth surface, indicating a more effective barrier layer. Meanwhile, it was interesting that the addition of PDPFDE evidently improved the impact strength and elongation at break of PP/IFR composites.     

Composite layers consisting of polyaniline and poly(o-phenylenediamine): Electrochemical deposition, electrochromic and electrocatalytic properties

The composite polymer layers consisting of polyaniline (PANI) and poly(o-phenylenediamine) (poly(o-PDA)) were electrodeposited on a platinum electrode by simultaneous electrochemical oxidation of corresponding monomers from aquaeous hydrochloric solutions. The growth of PANI and poly(o-PDA) occurs separately resulting in layers with two distinct, finely distributed phases. The first deposited layers are composed mainly of poly(o-PDA) and become richer in PANI as the electropolymerization proceeds. The aniline/o-PDA copolymer was not formed during electrodeposition, as evidenced by cyclic voltammetry and Fourier-transformed IR spectroscopy. It was demonstrated that the electrochromic properties of resulting composite layers are the combination of yellow/brown-reddish and green/dark blue observable color transitions which are characteristics of poly(o-PDA) and PANI, respectively. Electrocatalytic properties of the electrosynthesized composite layers were investigated on quinone/hydroquinone (Q/H₂Q) redox system and it was shown that the composite layers increase the heterogeneous electron transfer rate with a magnitudes ranging from those obtained on pure poly(o-PDA) to those obtained on pure PANI layer.     

The explicit representation to the principal rotation angle and the principal rotation axis

By using Cayley-Hamilton theorem, two kinds of explicit representation for the rotation tensor are proposed. One contains the lower powers of deformation gradient, by which the formula of the principal rotation angle and the explicit representation of principal axis are obtained; the other, a high efficient method to obtain the rotation tensor, does not contain the complicated coefficients and uses few variables. Some properties about the principal rotation angle and the principal rotation axis are obtained.     

有效弹性模量微分法的一种近似解法

鉴于Eshelby张量在整个微分法的"取出-添入"过程中的变化对等效模量变化影响较小,论文推出了微分法的近似显式解.该近似解形式简捷,计算方便,不仅适用于球形颗粒夹杂,对随机短纤维夹杂等情况也同样适应,所得结果与实验数据非常接近.     

Basis-free expressions for derivatives of a subclass of nonsymmetric isotropic tensor functions

The present paper generalizes the method for solving the derivatives of sym- metric isotropic tensor-valued functions proposed by Dui and Chen(2004)to a subclass of nonsymmetric tensor functions satisfying the commutative condition.This subclass of tensor functions is more general than those investigated by the existing methods.In the case of three distinct eigenvalues,the commutativity makes it possible to introduce two scalar functions,which will be used to construct the general nonsymmetric tensor func- tions and their derivatives.In the cases of repeated eigenvalues,the results are acquired by taking limits.     

用CCD摄像机动态估算测量云雾含水量的初步试验

云雾含水量是一个研究和定义云雾微物理结构的关键物理量 ,它与云雾的强度直接有关。介绍一种以 CCD数字摄像机为核心器件的光学图像传感系统 ,该系统通过基于数字摄像的能见度自动测量技术 ,可以有效反演出云雾的含水量。在报告系统的测量原理、理论方法和系统基本构成后 ,给出了用该系统动态估算测量两次大雾过程的雾含水量与实测雾含水量的对比分析结果。实验结果表明 :用仪器系统动态估算测量的结果与实测值吻合得相当好。两者的均方根差小于 0 .1g/ m3,相对均方根偏差小于 2 0 %