某商用车冷却系统一维数值分析与性能优化

利用一维数值分析与整车热平衡试验解决某车型发动机出水温度过高的问题。以整车许用环境温度为评价指标,考虑发动机台架热平衡数据为边界,搭建整车冷却系统换热分析模型并基于整车热平衡试验进行标定。通过分析得出风量是影响许用环境温度的主要因素,从风扇性能优化与空气侧流通条件改善两方面提高某车型许用环境温度。结果表明:外特性最大扭矩点工况下,新型无轮毂风扇提高许用环境温度2.5℃;前下挡网结构优化与空滤器右置方案分别提高许用环境温度1.7℃和2.4℃,经过优化该车许用环境温度满足设计要求。

Experimental study on visco-elastic constitutive relationship and its parameters for geogrids

Geogrids are used as reinforcement materials widely in geotechnical and civil engineering fields. In this paper, a series of comparative tests on creep behavior of specific geoOgrids are conducted in the laboratory under different combinations of loading levels and environmental temperature. Based on the test results,comparative analyses are made to study long-term behaviors of isochronous load-strain curves, creep curves and relaxation curves for the specified geogrids. Furthermore, a constitutive model based on theory of visco-elasticity and tests results is proposed for geogrids and a rational procedure is presented in detail for determining the relevant parameters of the proposed model. Finally, the effect of tests temperature on model parameter values is investigated.

Experimental Study to Evaluate the Performance of Iraqi Passive House in Summer Season

lraq locates in hot arid region （30 °N-37 °N）, where the hot summer season is very long and the ambient temperature is about 50 ℃. Cooling of building needs A/C （air-conditioning） system which consumes more than 60% of the total electricity supplied to residential building. So, there is really need to minimize the energy consumption by enhancement the performance of Iraqi buildings using passive house technique. This paper presents the thermal performance ofa Passivhaus model built in Kirkuk （35 °N）. The design depends on the using of suitable materials, sufficient insulation, well airtightness and underground air cooling. The experimental measurements take in consideration several parameters like ambient temperature, solar radiation, orientation of the building and duration. The results give good indication of the benefit of using this technique of passive cooling system in Iraqi residential buildings. The indoor temperature could be reduced to 30 ℃, while, the energy consumption for cooling could be saved up to 80%.

单模光纤环热应力双折射仿真分析

光纤陀螺在温度场作用下产生零位偏移,降低了光纤陀螺的精度。光纤环是光纤陀螺产生温度误差的主要根源。分析了温度场作用下,单模光纤环产生热应力双折射的机理。基于有限元方法仿真出光纤环在特定加热条件下的热应力双折射的大小及其随时间的变化。最后结合仿真结果提出了减小光纤环热应力双折射的几种方法,对提高光纤陀螺温度环境性能有较大的指导意义。

The influence of environment temperatures on single crystalline and polycrystalline silicon solar cell performance

The influence of the cell temperature (named interior environment temperature) and ambient air temperature (named exterior environment temperature) on the open-circuit voltage,short-circuit current,and output power has been carefully studied for the Si solar cells.The results show that one of the environment temperatures plays the major role,and the temperature dependence of device performance parameters is different for single crystalline and polycrystalline Si solar cells.Furthermore,the ambient air temperature builds a bridge for the comparison of the effect between the cell temperature and the illumination intensity on solar cell performance.Based on the experimental results,the reasons which cause the difference of the environment temperatures dependence are analyzed.

The influence of substrate and atmosphere on the properties of FeSiB(Cu,Nb) alloy melts

The surface tensions and contact angles of Fe_(78)Si_9B_(13) and Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9 alloy melts were studied as a function of temperature in various atmospheres(vacuum, Ar and N_2 gas) and on different substrates(Si C, Al_2O_3 and BN). It is indicated that Si_3N_4, NbN, Fe_2 Al B and B_(13)C_2 are generated as new phases at the interface between the melt and substrate, and reactive wetting behaviour exists during the heating process. The surface tensions of two alloy melts on BN substrate both firstly decrease and then increase along with increasing temperature, leading to V-shaped surface tension versus temperature, which results from atomic diffusion effects in the surface layer during the oxidation of BN and formation of C-rich layer. Comparably, the surface tensions on Al_2O_3 and Si C substrates decrease with increasing temperature throughout the entire temperature range. Among three substrates, BN exhibits the mildest wetting behaviour. The vacuum environment has the strongest protective effect on melt stability among the tested atmospheres. These findings enrich our knowledge about the effects of the substrate and atmosphere on Fe-based alloy melts at a high temperature, and provide theoretical reference for designing jet nozzles in melt-spinning techniques.

An experimental investigation on decoupling performance for a lateral axis micromachined gyroscope with varying environmental parameters

This paper carries out an experiment study of decoupling performance for a novel lateral axis micromachined gyroscope with varying environmental parameters. The non-ideal mathematical model for the coupling mechanism of the gyroscope is estab-lished through the gyro dynamic response matrix. The coupling components varying with ambient pressure and temperature induced by stiffness coupling, damping coupling and electrostatic force coupling are semi-analytically discussed. The overall coupling ratio is evaluated via experiments in the custom-built installation. The testing results show that the decoupling per-formance of the gyroscope is sensitive to the environmental parameters and all the non-ideal errors are determined as a function of ambient pressure and temperature. The coupling error varies from 0.05% to 0.25% within the pressure range of 100 Pa-100 kPa. The characteristics of coupling with temperature are measured from 20℃ to 100℃ with a variation from 0.35% to 0.41%. The results also indicate that within the range of measured ambient pressure and temperature, the minimum coupling ratio occurs at 100 Pa and room temperature. The overall performance of the gyroscope is tested under the pressure of about 2000 Pa and room temperature to achieve a relatively low coupling ratio. The scale factor is measured to be 7.8 mV （°）-1 s-1 with nonlinearity about 0.45% in the full-scale range of 600 （°） s-1. The short-term bias stability is approximately 0.06 （°）s-1 （1σ） for 20 min with noise equivalent angular rate evaluated to be 0.077 （°） s-1 Hz-1/2.

Modeling of mechanical behaviors for natural fiber reinforced composites under hygrothermal ageing

In recent years,natural fiber reinforced composites have been widely applied to various industrial products for their excellent environmental-friendly performance.It is essential to understand the mechanical properties of natural fiber reinforced composites under their in-service environment.Compared with synthetic fibers,the hydrophilicity of natural fibers could result in a much larger quantity of water absorption from the moisture atmosphere,which would have adverse consequences for the durability of natural fiber reinforced composites[1].The environmental temperature would affect the