Effect of Air Gap under Fabric on Thermal Protective Performance Using an Improved Apparatus

The bench top test is one of the most important and effective methods to evaluate the total thermal protective performance(TPP) of firefighters' protective clothing,which is greatly influenced by the air gaps entrapped.In this paper,to investigate the effect of air gap width on TPP,a new improved apparatus with two height changeable buttons to hold the thermal sensor was developed to get a series of air gap sizes from 0 mm to 40 mm.The TPP of two types of flame-resistant outer fabrics was measured with TPP test apparatus respectively.Analysis of temperature rise with each air gap width was made to determine the effects of different air gaps on protective performance.It was indicated that air gap size had great effect on TPP of fabrics in the bench top test.An air gap width above 8 mm was suggested for the thermal protective clothing design.

THERMAL PERFORMANCE OF GREEN ROOF PANELS IN SUB-ZERO TEMPERATURES

To date,much of the research on green roof technology has focused on the capacity for these systems to contribute to the cooling of buildings during summer months.The thermal performance of green roofs in cold climate conditions is critical to understanding the potential of these roofs to decrease energy use in buildings during winter.This paper compares the behavior of two green roof systems with that of a conventional built-up roof by making use of a novel hot box testing apparatus.The green roofs tested are classified as extensive systems.Each system included:a 3 mm thick styrene butadiene rubber waterproofing membrane,0.2 mm thick polyethylene slip sheet,a 76 mm thick extruded polystyrene insulation layer,2 mm thick filter fabric,a 51 mm drainage layer followed by a 2 mm thick filter cloth,either 100 mm or 150 mm growing medium,and a 25 mm thick wild flower vegetated mat.The conventional roof consisted of a 2 mm thick layer of Kraft™vapour retarder bonded with insulation adhesive,51 mm of isocyanurate insulation,25 mm of fibreboard,a three ply(2 mm)cold-applied built-up roof membrane,and a gravel ballast finish 51 mm thick.Each roof was subjected to temperatures between 0℃ and–25℃,while the temperature within the hot box was held at 21℃.The effect of vegetation on a green roof to reduce wind speeds or increase snow cover were not considered in this study.The power required,as well as the temperatures throughout each system at steady state conditions,were monitored for 5 hours.The data collected from thermal testing suggests that the R-value of green roofs with 100 mm or 150 mm thick layers of growing medium is 37%higher than a conventional roof when subjected to temperatures of 0℃ to–25℃.

EVALUATION OF SELECTED DYNAMIC MODELS IN COMPARISON WITH HOT BOX TEST RESULTS FOR MEASUREMENT OF BUILDING ENVELOPE THERMAL PROPERTIES

This research is mainly focused on the experimental measurement of R-value by several different models.Building energy consumption accounts for about 40%of the total energy use in the U.S,and therefore accurate energy simulation is desired.The R-value is one of the key parameters that can influence the energy simulation results and therefore is of great importance.The Average Model has long been the most widely accepted method to measure the thermal properties of building components.However,its steady-state assumption and dependence on temperature difference limit its use especially for in-situ measurement.In this study,several dynamic models,including the Pentaur Model and R-C Network Models,are studied with test data obtained from a series of hot box tests performed in the Building Enclosure Testing Laboratory.The results show that the 3R2C model has the best performance and a desirable stability of accuracy with respect to different levels of temperature difference,and therefore is recommended for practical measurement.The results also indicate that unlike the Average Model,the accuracy of dynamic models does not necessarily depend on the level of temperature difference.

Numerical Efficient Thermal Network for Calculating the Brake Disc Temperature

The simulation of the brake disc temperature is an important tool in the development of passenger cars.Nowadays thermal models of brake discs are real-time applications,running on electronic control units(ECUs)of cars to improve the vehicle safety in several ways.These models are often working with full empirical methods,leading to large deviations between calculation and measurement.To meet the requirements of automotive safety integrity levels(ASILs),these thermal models cannot rely on the state of the art ambient air temperature sensors,which causes unacceptable deviations.Focusing on numerical efficient thermal simulations,a new approach of a semi-analytical thermal network for simulating the brake disc temperature with minimal effort is proposed.The thermal network is based on lumped parameters,using two thermal capacity nodes and a constant ambient temperature.Using semi-analytical correlations,the model can be adapted to different geometries and car lines effortlessly.The empirical parameters of the model result only from two standardized tests.These parameters are used to evaluate the estimation accuracy in real driving situations.Additionally,the adaptability is tested for two different car lines and four brake disc dimensions.These tests are initially performed with unchanged parameters and afterwards with refitted parameters.The model shows a good estimation for the tested load cases.Compared to the state of the art,the proposed model is less accurate than complex finite element method(FEM)models and computational fluid dynamic(CFD)approaches,but shows a higher accuracy and better adaptability than other lumped parameter models with comparable numerical effort.Hence,possible applications can be dimensioning the brake system in the development process of new car lines or a real-time simulation on the latest ECU in the vehicle.

国产Zn-5%Al-混合稀土合金镀层高钒封闭索丝耐久性研究

以国家速滑馆首次应用的国产Zn-5%Al-混合稀土合金镀层高钒封闭索丝为研究对象,对其使用性能、基本特性及耐久性等进行研究。采用了国家速滑馆内部高空索体实际服役环境处的大气暴露试验方式,综合考虑索在加工安装过程中易产生的损伤,对索丝试件进行了划痕、刮擦、焊点的预制缺陷设计,研究了含预制缺陷的国产Zn-5%Al-稀土合金镀层高钒封闭索丝在真实使用环境中的大气腐蚀行为规律,并采用力学性能测试研究了索丝在服役环境大气腐蚀作用下的力学性能变化规律及不同缺陷对力学性能的影响。结果表明,加工安装过程中在索丝表面合金镀层产生的划痕、刮擦、焊点等损伤,会破坏合金镀层的完整性。大气暴露试验和力学性能试验中,三类缺陷对索丝金属镀层防大气腐蚀性能和单丝抗拉强度均有负面影响,其中焊点缺陷影响最大,单丝抗拉强度下降约40%。

永磁辅助同步磁阻电机优化设计及试验

永磁辅助同步磁阻电机具有高效率、高功率密度、低维护需求等优点,在电机的电磁设计时,由于涉及的参数变量较多,如磁通密度、线圈匝数、永磁材料的选择等,尤其是在追求最大化效率和输出功率的同时,还需要考虑到成本、物料的可获得性以及设计的可行性。该文基于永磁辅助同步磁阻电机基本工作原理及结构估算模型,以提高电机额定工况下运行效率为优化目标,采用田口法对电机相关参数进行优化设计,并对优化后的结果与原始方案进行对比。测试结果表明,与原始设计相比,优化后的电机在效率、温升控制和输出扭矩方面均有明显改进,尤其是在高负载条件下,优化电机展现出更稳定的性能和更高的能效。研究结果旨在通过采用先进的设计方法和试验验证,为永磁辅助同步磁阻电机性能的优化提供相关参考和建议。

一种基于Al_(2)O_(3)/SiC气凝胶的热防护系统隔热性能研究

飞行器再入大气层时,高速气流的冲刷作用会在其表面产生极高热流密度和压力,这种双重载荷可能对飞行器的结构材料造成严重的热损伤,甚至导致飞行事故。针对该问题,文章设计了以Al_(2)O_(3)/SiC复合气凝胶作为隔热层的轻质三明治结构热防护系统,并通过氧−乙炔烧蚀试验对典型高温条件下该热防护系统的隔热性能进行测试,结果显示:热防护系统的线烧蚀率和质量烧蚀率随隔热层厚度的增加而逐渐减小,当系统厚度为14 mm时,线烧蚀率和质量烧蚀率分别为0.0019 mm·s^(-1)和0.0031 g·s^(-1),且烧蚀形貌整体性较好,说明热防护系统具有优异的隔热及力学性能。同时,通过有限元仿真方法对热防护系统进行热力耦合分析,对烧蚀试验结果进行了验证。

基于不同发泡剂种类与掺量的发泡活性粉末混凝土性能研究

为探究发泡活性粉末混凝土在过碳酸钠、铝粉、缓释发泡剂3种发泡剂的不同掺量条件下对其力学性能、热工性能及耐久性能的影响,在基础配合比保持不变的情况下,分别以4%~6%过碳酸钠掺量、0.05%~1.50%铝粉掺量及1%~2%缓释发泡剂掺量为参数展开试验研究。结果表明:发泡活性粉末混凝土的干密度、导热系数、抗压强度、抗折强度随着发泡剂掺量的增加逐渐降低;掺入缓释发泡剂的发泡活性粉末混凝土力学性能、热工性能最优;缓释发泡剂的掺量为1.5%时,发泡活性粉末混凝土干密度为1381 kg/m^(3),导热系数为0.078 W/(m·K),28 d抗压、抗折强度分别为13.97 MPa和4.88 MPa,抗冻性最好,电通量为505.4 C。提出的最优配合比可为发泡活性粉末混凝土在外围护墙板中的应用提供参考。

抛物面槽式太阳能集热器球形接头测试系统的研制与应用

球形接头是抛物面槽式太阳能集热器的关键部件,针对球形接头易发生运转卡涩和导热油泄漏问题,研制了一套球形接头性能测试系统。该测试系统可以实现球形接头在旋转、摆转或旋摆联动模式下,以及在导热油温度达393℃和压力达4.1 MPa工况条件下的加速寿命测试。以导热油为传热流体,开展了球形接头在导热油温度为393℃和压力为2.3 MPa工况条件,以及温度、压力变化条件下的性能测试研究,分析了球形接头在模拟12年寿命期的扭矩特性和密封性能,验证了该测试系统运行的稳定性和可靠性,并且关键技术参数的控制精度和测量精度满足使用要求,为球形接头的性能评价提供了技术支撑。

CR 200J用树脂基摩擦材料的正交试验及多指标加权优选

为制备CR 200J用高耐磨树脂基摩擦材料,采用正交试验法设计不同含量的减摩组分(鳞片石墨、石油焦)与增摩组分(NFJ高温黏结剂、腰果壳油摩擦粉)的树脂基摩擦材料配方。通过热压成型法制备出样品,在制动压力0.8 MPa和转速3300、4200、5400 r/min下测试试样的平均摩擦因数,并计算试样的体积磨损率、热衰退性能及对偶质量磨损。对试样的平均摩擦因数、体积磨损率、热衰退性能及对偶质量磨损进行极差分析及均一化处理,使用多指标权重优选了综合性能优异的配方。结果表明:鳞片石墨在高转速下对材料的平均摩擦因数起稳定作用及降低材料的热衰退性能,而石油焦在低速制动过程中可稳定材料的平均摩擦因数;NFJ高温黏结剂对材料的各项性能影响不显著,而腰果壳油摩擦粉在高转速下表现出优异的黏弹性,有利于提高材料的平均摩擦因数,降低材料的体积磨损率及对偶质量磨损。使用多指标权重优选得到较好的配方,其中鳞片石墨、石油焦、NFJ高温黏结剂、腰果壳油摩擦粉的质量分数分别为1%、4%、3%、6%。

建筑用金属面绝热夹芯板耐久性试验研究

建筑用金属面绝热夹芯板广泛应用于工业与民用建筑的屋面和墙体。现行的国家标准中没有建筑用金属面绝热夹芯板耐久性试验方法及评价指标的要求。根据金属面夹芯板实际用途,选择3种不同芯材的金属面夹芯板,在4种不同环境条件下进行耐久性试验,并对芯材的密度、质量吸湿率、导热系数以及金属面夹芯板的粘结强度进行测试。通过对试验数据的分析,找出影响试验数据的主要因素,并对金属面夹芯板耐久性评价指标的确定提出建议。

沥青路面热反射涂层开发及耐久性能评价

为开发高性能沥青路面热反射涂层,研究了功能填料配比对隔热性能的影响、粘结材料配比对粘结强度的影响以及功能填料掺量对隔热性能和粘结强度的影响,并在此基础上制备热反射涂层,对其耐久性能进行评价。结果表明:不同TiO_(2)和SiO_(2)质量比例下,随着TiO_(2)质量的增加,热反射涂层的隔热性能升高。相同固化剂掺量下,在增韧剂掺量为20%~30%时,粘结强度最大;相同增韧剂掺量下,当固化剂掺量为30%~40%时,粘结强度最大。随着功能填料掺量的增加,热反射涂层隔热性能升高,粘结强度先缓慢降低,后加速降低。根据各组分最佳配比制备热反射涂层,涂层磨耗率随磨耗次数的增加而升高,前期升高速率快;隔热性能随磨耗率的增大而线性减小;抗滑性能随磨耗次数的增加先迅速上升后缓慢下降。

高性能柴油发动机耐久性能改进策略

本文旨在探讨如何改进高性能柴油发动机的耐久性能。从材料选用、润滑系统优化和热管理控制等方面出发,分析了高强度材料与耐磨性材料的平衡运用、表面处理技术的改进、润滑油性能选择与润滑系统参数优化设计,以及热管理控制下的散热系统和燃烧室温度控制。通过深入讨论这些关键领域,旨在为提升高性能柴油发动机的耐久性能提供有效的改进策略。

Analysis on the development of chemically-improved soil in railway engineering

Purpose-Explore the development trend of chemically-improved soil in railway engineering.Design/methodology/approach–In this paper,the technical standards home and abroad were analyzed.Laboratory test,field test and monitoring were carried out.Findings–The performance design system of the chemically-improved soil should be established.Originality/value–On the basis of the performance design,the test methods and standards for various properties of chemically-improved soil should be established to evaluate the improvement effect and control the engineering quality.

Jet CAT P80 Thermal Analyses and Performance Assessment Using Different Fuels Types

The micro gas turbine propulsion systems represent a good choice for the unmanned aerial vehicles(UAVs). The present work monitors the engine parameters, correlating them with other important engine instrumentation data. The aim of this research was to study the operation of the Jet CAT using various types of fuels under various operating conditions: normal acceleration and sudden acceleration. The measured parameters were monitored under different conditions:(A) Engine operation at two different ambient temperatures – outdoor at 0oC and inside at 19oC; and(B) Using 4 fuel types: kerosene, diesel fuel, kerosene with 5% gasoline and kerosene with 10% gasoline. The relevance of this work is given by the fact that a detailed analysis is performed for the idle regime. The paper will present the detailed test plan used and the most relevant charts with the obtained results for: start time, force, temperature before turbine, fuel flow, depending on micro turbo engine speed.

基于热误差补偿的行星滚柱丝杠综合性能试验台设计与分析

行星滚柱丝杠综合性能是丝杠性能的主要指标,现有测试系统多以静态测量法进行测量,操作复杂且偶然误差较高。通过对行星滚柱丝杠综合性能动态测试系统的试验原理、硬件设计、软硬件通讯、软件界面结构的研究,设计了一套行星滚柱丝杠综合性能动态测试系统。基于LabVIEW设计上位机人机交互与控制监测软件对丝杠热伸长量进行了检测,并使用最小二乘法分析丝杠温升与位移的关系,对定位精度试验进行误差补偿。实验结果表明,所设计的试验台系统可以测量行星滚柱丝杠定位精度、噪声、温升、极限转速、加速度,同时热误差测量补偿系统可以减小温度变化对测量位置的影响,补偿前后精度测量指标提升均在30%以上,偶然性误差较小并且精度提高。

新能源装载机用IGBT水冷板场协同优化与节能

为提升国产某款水冷板(liquid-cooled plate,LCP)的传热特性,降低功耗,对其建立3D模型,通过实验进行数值模拟。考虑水冷板结构特性,提出放大系数、散热柱宽度、散热柱数量、流道高度和宽度等因素组成的结构参数,确认对应的16组正交试验改进方案,并获取对应数据;基于场协同原理,利用传热协同角β和压力协同角θ筛选出传热性能好、功耗低的方案,同原始方案进行综合性能对比。数值模拟与实验数据的吻合程度较好,最大误差为6.61%;改进方案10(improvement scheme 10,IS10)的平均传热协同角和压力协同角分别下降0.97%和1.04%。综合性能方面,IS10的最大差异为0.372%;优化后,水冷板出口温度高4.62~5.93℃,速度高0.1 m/s,压力损失降低161.89 Pa。

高性能混凝土耐久性检测中电化学阻抗谱技术的应用探究

以高性能混凝土耐久性检测新技术的应用为目的,结合某沿海地区跨海大桥建设工程实例,利用电化学阻抗谱(Electrochemical Impedance Spectroscopy,EIS)技术,分析阻抗谱图,从而表征混凝土的离子迁移情况与腐蚀状态,以验证此工程所用的混凝土耐久性。结果显示,在该大桥主桥墩、连桥处应力集中位置,电荷转移电阻较低,存在被腐蚀风险,其内部电化学行为相对复杂,存在离子迁移情况,表示耐久性有待加强。针对此类问题,利用Abaqus有限元分析软件优化混凝土配合比,确定最佳硅灰掺量为7%、粉煤灰掺量为25%、水灰比为0.38、高效减水剂掺量为1.5%,并采取防腐涂层,以提高混凝土耐久性。由此可见,应用EIS技术及相关改进措施,能够有效地提高混凝土耐久性,保障大桥安全。

机制砂制备高强度高性能混凝土的性能试验研究

为探究高强度高性能混凝土制备过程中,机制砂取代天然河砂的可行性,对机制砂制备高强度高性能混凝土的性能展开研究。结果表明,机制砂混凝土板的单位面积开裂面积为43mm^(2)/m^(2),抗裂等级达到L-V级,显著低于河砂混凝土。机制砂混凝土制备试件的电通量达Q-Ⅳ级,DRCM达RCM-Ⅳ级,且数值均低于河砂混凝土。河砂混凝土和机制砂混凝土抗硫酸盐等级均能够达到KS150级以上,且耐蚀系数相差不大。

床上用品恒温性能测试方法研究

恒温纺织品是指根据人体过热或过冷的情况,将身体的热量重新吸收存储或者重新释放,以达到主动保温效果的一种功能性新型纺织品。设计一种恒温性能测试方法,通过平板式织物保温仪、温度传感测试仪等设备进行恒温性能测试,研究6类床上用品的恒温性能。结果表明,设计的恒温性能测试方法能够较好地表征床上用品的恒温保暖性能;具有恒温性能的床上用品,能够在较短的时间内升温至30.0℃以上,且在一段时间内能够保持相对恒温。