采用两段式引射器的跨临界CO_2两相流制冷系统性能的数值模拟

对两相流引射器内部工质流动特性进行了数值模拟,通过在不同几何尺寸和不同工况条件下引射器性能分析来确定影响其性能的因素。分析了两段式喷嘴引射器在不同第一喉部流通面积和不同工况条件下的性能,以及两段式喷嘴引射制冷系统性能随着各参数的变化趋势:在固定气冷器出口压力9.00 MPa,温度43℃和蒸发温度6℃条件下,两段式喷嘴引射器性能随着第一喉部流通面积的增加先增大后减小,并在第一流通面积为1.54 mm2时取得最大引射比;当两段式喷嘴引射器第一喉部流通面积为1.54 mm2时,在模拟工况范围内引射器的引射比随着气冷器出口温度的增加而增大,随着蒸发温度的降低而减小;当气冷器出口压力和蒸发温度分别为9.00 MPa和6℃时,引射器的引射比在气冷器出口温度为43℃工况下取得最大值。     

几何参数对引射器及两相流引射制冷系统性能的影响

用两相流引射器代替膨胀阀,可回收两相流引射制冷循环中高压工质的压力能,提高制冷系统效率。对以R134a为工质的两相流引射制冷系统性能进行了实验研究,分析了喷嘴喉部直径和混合室直径对R134a两相流引射器及引射制冷系统性能的影响。实验结果表明,在固定工况条件下,存在使引射比达到最大的最佳喷嘴喉部直径和混合室直径组合。在蒸发温度为3℃、冷凝温度为55℃的工况下,当喷嘴喉部直径为2.0mm、混合室直径为16mm时引射器的引射比最大。在固定工况条件下,使引射比达到最大值的喷嘴喉部直径和混合室直径的最佳组合与使系统COP达到最大值的几何参数组合并不一致。这可能是由于在引射器中产生了激波等因素引起的,其中机理尚需要进行更深入的研究。     

跨临界CO2两相流引射制冷系统性能实验研究

对跨临界CO2两相流引射制冷系统性能进行了实验,分析了工况及引射器几何参数对系统性能的影响,结果表明:在实验工况范围内,跨临界CO2两相流引射制冷系统制冷量和COP随气体冷却器压力的升高而升高,随气体冷却器出口温度的升高而降低。对于使用不同喉部直径喷嘴的系统,在相同工况下,引射器喷嘴喉部直径较大的系统的性能较好。对于使用不同直径混合室的系统,随着气体冷却器压力的升高,使用小直径混合室的系统COP变化较大;当气体冷却器压力较低时,使用大直径混合室的系统COP较高,而当气体冷却器压力较高时,使用小混合室直径的系统性能较好。在相同工况下,与传统跨临界CO2循环进行比较,两相流引射制冷循环系统COP最大可提高14%。     

跨临界CO2两相流引射制冷系统性能实验研究

对跨临界CO2两相流引射制冷系统性能进行了实验,分析了工况及引射器几何参数对系统性能的影响,结果表明:在实验工况范围内,跨临界CO2两相流引射制冷系统制冷量和COP随气体冷却器压力的升高而升高,随气体冷却器出口温度的升高而降低.对于使用不同喉部直径喷嘴的系统,在相同工况下,引射器喷嘴喉部直径较大的系统的性能较好.对于使用不同直径混合室的系统,随着气体冷却器压力的升高,使用小直径混合室的系统COP变化较大;当气体冷却器压力较低时,使用大直径混合室的系统COP较高,而当气体冷却器压力较高时,使用小混合室直径的系统性能较好.在相同工况下,与传统跨临界CO2循环进行比较,两相流引射制冷循环系统COP最大可提高14%.     

基于延迟均衡的CO_2两相引射器模型研究

引射器对跨临界CO_2引射制冷系统性能有极大的影响。本文考虑CO_2两相引射器中存在的非平衡相变、超音速和壅塞等复杂流动现象,构建了CO_2两相引射器的1D分布模型,并采用延迟均衡理论分析喷嘴中的非平衡相变过程。与实验结果比较显示,所建立的延迟均衡模型能够很好的预测引射器的性能。此外,通过与均衡模型的相比显示,在本文所选工况下,延迟均衡模型计算所得的主动流流量比均衡模型预测值低12.39%~25.30%,同时非平衡现象将延缓喷嘴中的膨胀过程,使得喷嘴出口压力比均衡模型预测值高。本文采用所建模型进一步分析了引射器的结构对性能的影响,结果显示在一定的工况下存在最优的混合室直径使得引射系数和升压比都较高;而当混合室直径一定时,较长的混合室有利于提高引射器的升压比。     

两段式喷嘴几何参数对引射制冷系统性能的影响

用引射器代替膨胀阀可以提高制冷系统COP,而影响引射制冷系统性能的重要因素是引射器性能。对使用不同喉部直径喷嘴的引射制冷系统性能进行实验研究,分析引射器两段式喷嘴第一和第二喉部直径对引射器和系统性能的影响。实验结果表明,在冷凝温度40℃、蒸发温度-10℃工况下,随着第一喉部直径增大,引射比先升高后降低,制冷量和COP均降低,喉部直径为1. 8 mm时系统性能最佳;随着第二喉部直径增大,引射比先升高后降低,制冷量和COP均先降低后升高,喉部直径为1. 4 mm时系统性能最佳。     

两段式喷嘴引射器及其引射制冷系统性能实验研究

对采用两段式喷嘴引射器的两相流引射制冷系统进行了实验研究,并将两段式喷嘴的引射比及其系统COP分别与拉法尔喷嘴引射器的引射比及其系统COP进行了比较。实验结果表明：在冷凝/蒸发温度为45 ℃/1 ℃工况下,使用不同几何尺寸两段式喷嘴引射器的引射比均大于拉法尔喷嘴引射器的引射比,最大提高了约18%;使用两段式喷嘴引射器的制冷系统COP大于使用拉法尔喷嘴引射器的制冷系统COP,最大提高了约12%;在蒸发温度为1 ℃条件下,两段式喷嘴引射器及拉法尔喷嘴引射器的引射比均在冷凝温度为45 ℃时达到最大值,而在冷凝温度为50 ℃条件下,两种引射器的引射比均在蒸发温度为3 ℃时达到最大值。     

气-液引射器性能模拟研究

以满液式冷水机组中压缩机回油环路的引射器为研究对象,建立气-液引射器的三维数学模型,模拟引射器出口压力、喷嘴出口直径和流体动力黏度等因素对引射器性能的影响。模拟结果表明,随着引射器出口压力的升高,引射系数略有下降,工作流体的压差快速下降,但引射流体的压差基本不变;喷嘴出口直径增大时,引射系数急剧下降,工作流体的压差快速下降,而引射流体的压差快速增大;随着流体动力黏度的增加,引射系数急剧下降,工作流体的压差快速上升,而引射流体压差快速下降。     

液-气引射制冷系统实验研究

流体力学伯努力方程表明,采用较高密度的工作流体可以在相同的速度变换下,获得较大的压力变化。根据这一原理,针对液-气引射制冷系统中的引射器,通过采用高密度的盐溶液和室温液态金属替代传统工作流体水来探究高密度工作流体工作过程中系统的运行特性。并通过结构优化,将喷嘴从简单喷嘴替换成内环型喷嘴,增大喉嘴距等改进措施,提高系统制冷性能。实验研究发现,驱动流体密度对系统制冷性能具有重要影响;内环型喷嘴较简单喷嘴具有明显优势;喉嘴距从5 mm增加到13 mm过程中,系统制冷性能并不是单调提高的,而在10 mm出现最优值;实验得到了几种工作流体的制冷特性,为液-气引射制冷系统的改进提供了参考。     

几何结构参数对喷射器性能影响实验研究

在自行搭建的喷射器性能测试实验台上,以CO_2、N_2及R290为工质,通过改变喷射器喷嘴临界截面直径,总结喷射器喷射系数在不同的引射流体入口压力、工作流体入口压力及工质种类条件下的变化规律。实验设定工作流体温度为90℃,喷射器背压为3. 9 MPa,工作流体入口压力变化范围为8. 0—10. 0 MPa,引射流体入口压力变化范围为2. 4—2. 9 MPa,喷嘴临界截面直径变化范围为0. 68—0. 72 mm。实验结果表明:当保持喷射器的基本工作参数不变,引射流体入口压力为一定值时,喷射器喷射系数随喷嘴临界截面直径的减小而逐渐增大;当保持喷射器的基本工作参数不变,工作流体入口压力为一定值时,喷射器喷射系数随喷嘴临界截面直径的增大而逐渐减小;在相同工作压力下,喷射系数大小依次是N_2、CO_2、R290;在相同引射压力下,N_2、CO_2先达到稳定状态;在保持喷射器的基本工作参数不变时,工作流体入口压力及引射流体入口压力的提高对喷射器喷射系数均有提升作用。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.