模型桨叶温热特性试验研究

桨叶除冰技术是一项重要的直升机研究课题,桨叶温热特性是其中重要一环。本文详细介绍了桨叶测温传感器设计,测点布置,测试控制原理,温热特性试验内容及结果等。试验取得了真实可信的数据,得到了一套完整的试验方法。

市政污泥低温热干化特性及废气成分检测

市政污泥低温热干化是一种有效的污泥处理技术,但其特性及废气成分检测尚未完全探索。本文旨在深入研究市政污泥低温热干化的特性,并对其废气成分进行全面检测。通过此研究更好地了解市政污泥低温热干化的运行机理,为其在实际应用中提供科学依据和技术支持,为环境保护和污泥处理提供参考。

加热卷烟叶丝等温热失重及关键成分释放特性分析

为在加热过程中有效调控叶丝关键成分含量,在180℃、200℃和220℃加热温度下,利用宏量型烟草高温热转化热重技术考查加热温度对加热卷烟叶丝(含水率1.5%)热失重过程及关键成分热释放特性的影响。结果表明:升高加热温度,会增加叶丝质量分数变化值,提高叶丝质量分数变化率,降低叶丝热失重过程的稳定性;当加热温度分别为200℃和220℃时,各关键成分的质量分数变化值和变化率由大到小依次为烟碱、甘油、水分、其他成分,其中烟碱基本完全释放;当加热温度为180℃时,叶丝关键成分质量分数变化值和变化率由大到小依次为烟碱、水分、甘油、其他成分,其中烟碱、甘油、水分的质量分数变化值较高,其他成分的质量分数变化值较低。

加热卷烟烟叶原料低温热解特性及其与感官品质相关性分析

采用热重技术对烤烟、白肋烟、香料烟、雪茄烟原料的低温热解特性进行分析,同时对烟叶原料在加热条件下的感官品质进行评价,并进一步统计分析热解特性与感官品质之间的相关关系。结果表明:各烟叶在线性升温-恒温烘焙的加热条件下均经历4个失重阶段(脱水干燥阶段、挥发性成分脱除阶段、纤维素类成分分解阶段和恒温烘焙阶段),但在不同失重阶段中的热解特征参数存在一定差异;随着甘油施加量的升高(0%~15%),各烟叶原料在挥发性成分脱除阶段的最大失重速率及失重率均有所增大,烤烟的最大失重温度有所提高,而白肋烟、香料烟、雪茄烟则有所降低;当甘油施加量为15%时,其对烤烟在该阶段的失重率影响最大,对香料烟的影响最小;随着甘油施加量的增大,各烟叶样品的感官品质总分均有所提高;甘油施加量与烟气量、香气量、均匀性得分及感官品质总分呈极显著正相关,最大失重速率与杂气、刺激性、劲头得分及感官品质总分之间存在明显正相关关系,纤维素类成分分解阶段的最大失重速率与香气量、杂气、刺激性、纯净度、劲头得分及感官品质总分间存在负相关关系。

背壁5-II材料高温热物理性能及微结构特征

研究了背壁5-II材料的密度、失重率和孔隙率随温度的变化规律,测试了温度对比定压热容、热导率的影响,研究了不同温度下和发动机长时间热试车下5-II材料的微结构特征。结果表明,5-II材料密度随温度升高而降低,热解后密度降至1.28 g/cm3,开孔率在30%左右;比定压热容随温度升高而增大,热导率随温度缓慢降低;随温度升高,其微结构特征表现为孔隙的大量增加和贯通,密度和孔隙率可作为固体发动机背壁热解失效的主要参量。

寒冷地区日光暖棚羊舍设计与暖棚环境控制

雁门关寒冷地区应用暖棚养羊,可以保持适宜的温热环境,显著提高生产效率。暖棚的设计决定其采暖性能,通过不同屋面角设计暖棚,并比较其温热特性,以及暖棚对肉羊生产性能的影响,结果表明,屋面角为60°和50°的暖棚均有较好的采暖功能,50°屋面角暖棚温热环境稍次于60°屋面角。雁门关地区最佳屋面角应为60°。

GRP温室覆盖膜温光性能测试分析

该文在实验基础上,初步研究了GRP温室覆盖薄膜的温光性能.结果表明,GRP膜具有良好的温热性与透光性,在弱光条件下,透光率增强,因而提高了室内温度,而在强光照条件下,透光率减小,抑制了室内高温的出现;另外,在实验期间,试验温室未见起雾,滴水也很少,说明新材料具有良好的防雾、防滴性能.因此,GRP膜具有明显的增产效应,与对照温室相比,增产幅度高达16.2%.

Dielectric properties and temperature increase characteristics of zinc oxide dust from fuming furnace

Cavity perturbation method was used to determine the dielectric properties （ε′,ε″, and tanδ） of zinc oxide dust in different apparent densities. The process was conducted to study the microwave-absorption properties of zinc oxide dust and the feasibility of microwave roasting zinc oxide dust to remove fluorine and chlorine. The dielectric constant, dielectric loss, and loss tangent were proportional to the apparent density of zinc oxide dust. The effects of sample mass and microwave power on the temperature increase characteristics under the microwave field were also studied. The results show that the apparent heating rate of the zinc oxide dust increases with the increase in microwave roasting power and decreases with the increase in the sample mass. The temperature of the samples reaches approximately 800 ＆#176;C after microwave treatment for 8 min, which indicates that the zinc oxide dust has strong microwave-absorption ability.

Experimental study on thermal characteristics of a double skin faade building

An experimental study of the thermal characteristics of an existing office building with double skin facade DSF were conducted in hot summer daytime in Nanjing China. The temperature distributions of the DSF and indoor environment were measured at different control modes of DSF.The results show that the energy consumption of the air conditioning system in room B with opened exterior vents a closed interior facade and an air cavity with shading was 21.0% less than that in room A with closed exterior vents a closed interior facade and air cavity without shading in 9.5 h. The temperature distributions of the DSF and indoor environment in both horizontal and vertical directions were decisively influenced by shading conditions. The usage of shading devices strengthens the stack effect on the air cavity. Compared to room A the temperature distribution in room B is more uniform with smaller fluctuations.Meanwhile the problem of overheating in the air cavity of the DSF is still present in all tested conditions.

Experiment on Effect of Tip Clearance Leakage Flow on Heat Transfer of Turbine Outer Ring

The cascade model was tested using transient liquid crystal temperature measurement technology.The effects of main flow Reynolds number,blowing ratio and tip clearance height on the convective heat transfer coefficient of the turbine outer ring were studied.Two feature lines were marked on the turbine outer ring corresponding to the position of the blade.The conclusions are as follows:The tip clearance leakage flow has a great influence on the convective heat transfer coefficient of the turbine outer ring.When the clearance height and the blowing ratio are kept constant,gradually increasing the main flow Reynolds number will result in an increase in the convective heat transfer coefficient of the turbine outer ring.When the clearance height and the main flow Reynolds number are kept constant and the blowing ratio is gradually increased,the convective heat transfer coefficient of the turbine outer ring is almost constant.The heat transfer coefficient of the turbine outer ring surface is little affected by the blowing ratio;The clearance height has great influence on the heat transfer characteristics of the turbine outer ring.Under the typical working condition in this paper,when the tip clearance height ratio is 1.6%,the convective heat transfer coefficient of the outer surface of the turbine is the highest.

Heat Transfer Characteristics of Dropwise Condensation of Steam on Vertical Polymer Coated Plates

The plasma polymerization method and dynamic ion-beam mixed implantation method were employed to coat ultra-thin polymer films on copper plates. Experiments indicated that steady dropwise condensation of steam at atmospheric pressure occurred. The condensation heat transfer coefficients increased by approximately 3 and 5－7 times for the polytrimethylvinylsilane film and polytetrafluoroethylene film respectively, compared with the value for film condensation under the same experimental conditions. The temperatures on the condensing surface and inside the test block were found to be rapidly and randomly fluctuated. The properties of the coated films and advantages of the methods used in this investigation were discussed briefly.

Combustion characteristics of semicokes derived from pyrolysis of low rank bituminous coal

Various semicokes were obtained from medium-low temperature pyrolysis of Dongrong long flame coal.The proximate analysis,calorific value and Hardgrove grindability index(HGI) of semicokes were determined,and the ignition temperature,burnout temperature,ignition index,burnout index,burnout ratio,combustion characteristic index of semicokes were measured and analyzed using thermogravimetry analysis(TGA).The effects of pyrolysis temperature,heating rate,and pyrolysis time on yield,composition and calorific value of long flame coal derived semicokes were investigated,especially the influence of pyrolysis temperature on combustion characteristics and grindability of the semicokes was studied combined with X-ray diffraction(XRD) analysis of semicokes.The results show that the volatile content,ash content and calorific value of semicokes pyrolyzed at all process parameters studied meet the technical specifications of the pulverized coal-fired furnaces(PCFF) referring to China Standards GB/T 7562-1998.The pyrolysis temperature is the most influential factor among pyrolysis process parameters.As pyrolysis temperature increases,the yield,ignition index,combustion reactivity and burnout index of semicokes show a decreasing tend,but the ash content increases.In the range of 400 and 450 °C,the grindability of semicokes is rational,especially the grindability of semicokes pyrolyzed at 450 °C is suitable.Except for the decrease of volatile content and increase of ash content,the decrease of combustion performance of semicokes pyrolyzed at higher temperature should be attributed to the improvement of the degree of structural ordering and the increase of aromaticity and average crystallite size of char.It is concluded that the semicokes pyrolyzed at the temperature of 450 °C is the proper fuel for PCFF.

磁光记录新材料

介绍了磁光记录的物理原理和最新技术。非晶态稀土—过渡金属合金膜的发现加速了磁光记录的发展 ,在高密度多层膜记录中 ,由于他的宽温热磁特性 ,他记录的热磁斑直径仅数十纳米。为读出这么小的斑点 ,还必须加快发展更新的读出技术。

Pyrolysis and co-pyrolysis of lignite and plastic

The study firstly discusses the pyrolysis characteristics and kinetics by thermogravimetric analysis （TGA）, and then investigates the pyrolysis of lignite and co-pyrolysis with plastic （polyethylene or polypropyl- ene） in tube furnace. Meanwhile, the research focuses on the co-pyrolysis products under different mix- ing ratios as well as pyrolysis products at different testing temperatures and heating rates. The results show that higher final testing temperature and lower heating rate contribute to bond fission in lignite pyrolysis, resulting in less char product. In co-pyrolysis, lignite acts as hydrogen donor, and the yields of char and water rise with increasing amount of plastic in the mixture, while the yields of gas and tar decrease; and a little admixture of plastic will promote the production of gas and tar. Kinetic studies indi- cate that in temperature range of 530-600℃, activation energies of lignite are higher than those of lig- nite/plastic blends, and as plastic mass ratio increases from 0% to 10%, samples need less energy to be decomposed during co-pyrolysis.

Transient thermal behavior of radial fins of rectangular,triangular and hyperbolic profiles with temperature-dependent properties using DTM-FDM

This work focuses on transient thermal behavior of radial fins of rectangular,triangular and hyperbolic profiles with temperature-dependent properties.A hybrid numerical algorithm which combines differential transformation(DTM) and finite difference(FDM) methods is utilized to theoretically study the present problem.DTM and FDM are applied to the time and space domains of the problem,respectively.The accuracy of this method solution is checked against the numerical solution.Then,the effects of some applicable parameters were studied comparatively.Since a broad range of governing parameters are investigated,the results could be useful in a number of industrial and engineering applications.

Thermodynamic Performance Characteristics of a Brownian Microscopic Heat Engine Driven by Discrete and Periodic Temperature Field

A Brownian microscopic heat engine with a particle hopping on a one-dimensional lattice driven by adiscrete and periodic temperature field in a periodic sawtooth potential is investigated.In order to clarify the underlyingphysical pictures of the heat engine, the heat flow via the potential energy and the kinetic energy of the particles areconsidered simultaneously.Based on describing the jumps among the three states, the expressions of the efficiency andpower output of the heat engine are derived analytically.The general performance characteristic curves are plotted bynumerical calculation.It is found that the power output-efficiency curve is a loop-shaped one, which is similar to onefor a real irreversible heat engine.The influence of the ratio of the temperature of the hot and cold reservoirs and thesawtooth potential on the maximum efficiency and power output is analyzed for some given parameters.When the heatflows via the kinetic energy is neglected, the power output-efficiency curve is an open-shaped one, which is similar to onefor an endroeversible heat engine.

Effect of Mesa Size on Thermal Characteristics of Ver tical-cavity Surface-emitting Lasers

The effect of mesa size on th e thermal characteristics of etched mesa vertical-cavity surface-emitting lase rs(VCSELs) is studied. The numerical results show that the mesa size of the top mirror strongly influences the temperature distribution inside the etched mesa V CSEL. Under a certain driving voltage, with decreasing mesa size, the location o f the maximal temperature moves towards the p-contact metal, the temperature in the core region of the active layer rises greatly, and the thermal characterist ics of the etched mesa VCSELs will deteriorate.

Rheological characterization of A201 aluminum alloy

The thermodynamic characterization as well as the rheological characterization of the A201 alloy were conducted.Thermodynamic simulations (CALPHAD method) and calorimetric experiments were performed to determine the solidus and liquidus temperatures, the melting range and the sensitivity of the solid fraction at the thixoforming temperatures.The rheology of aluminium alloy A201 was examined using a high temperature Searle rheometer.The flow behaviour was analyzed with concentric cylinders of graphite to avoid chemical interactions with the liquid or semi-solid aluminium.The rotational body was grooved to prevent a phenomenon called wall slippage.Continuous cooling experiment was used to observe the shear rate effects on the flow behaviour.It can be seen that the viscosity level decreases at higher shear rates.Shear rate jump experiment was carried out to evaluate the steady state flow curve within the analyzed shear rate range from 60 s-1 to 260 s-1.It is found that the power law indexes are-1.35 and-1.49 for 35% and 45% solid fraction, respectively.Finally, some mechanical property data of as-cast and as-thixoformed A201 alloy are included indicating the potential for high strength applications.

Characteristics of hot tensile deformation and microstructure evolution of twin-roll cast AZ31B magnesium alloys

High temperature tensile properties and microstructure evolutions of twin-roll-cast AZ31B magnesium alloy were investigated over a strain rate range from 10-3 to 1 s-1.It is suggested that the dominant deformation mechanism in the lower strain rate regimes is dislocation creep controlled by grain boundary diffusion at lower temperature and by lattice diffusion at higher temperatures,respectively.Furthermore,dislocation glide and twinning are dominant deformation mechanisms at higher strain-rate.The processing map,the effective diffusion coefficient and activation energy map of the alloy were established.The relations of microstructure evolutions to the transition temperature of dominant diffusion process,the activation energy platform and the occurrence of the full dynamic recrystallization with the maximum peak efficiency were analyzed.It is revealed that the optimum conditions for thermo-mechanical processing of the alloy are at a temperature range from 553 to 593 K,and a strain rate range from 7×10-3 to 2×10-3 s-1.

Experimental study of viscosity characteristics of hightemperature heat transfer molten salts

In this paper several kinds of high temperature molten salts were investigated experimentally on viscosity-temperature characteristics with high-temperature viscometer.The viscosities of the molten salts were measured and compared with those from references to verify the reliability of the viscometer and measuring methods,and a good agreement was observed from the comparisons.Then,two new high-temperature molten salts were made from the HITEC salt by some additives and the viscosity-temperature profiles of them were obtained by experiments.The results show that the new molten salts have much lower viscosities,thus suitable for reducing the flow resistance in transportation system of high-temperature solar thermal power generation.