Enhance liquid nitrogen fracturing performance on hot dry rock by cyclic injection

Producing complex fracture networks in a safe way plays a critical role in the hot dry rock (HDR) geothermal energy exploitation. However, conventional hydraulic fracturing (HF) generally produces high breakdown pressure and results only in single main fracture morphology. Furthermore, HF has also other problems such as the increased risk of seismic events and consuption of large amount of water. In this work, a new stimulation method based on cyclic soft stimulation (CSS) and liquid nitrogen (LN2) fracturing, known as cyclic LN2 fracturing is explored, which we believe has the potential to solve the above issues related to HF. The fracturing performances including breakdown pressure and fracture morphology on granites under true-triaxial stresses are investigated and compared with cyclic water fracturing. Cryo-scanning electron microscopy (Cryo-SEM) tests and X-ray computed tomography (CT) scanning tests were used for quantitative characterization of fracture parameters and to evaluate the cyclic LN2 fracturing performances. The results demonstrate that the cyclic LN2 fracturing results in reduced breakdown pressure, with between 21% and 67% lower pressure compared with using cyclic water fracturing. Cyclic LN2 fracturing tends to produce more complex and branched fractures, whereas cyclic water fracturing usually produces a single main fracture under a low number of cycles and pressure levels. Thermally-induced fractures mostly occur around the interfaces of different particles. This study shows the potential benefits of cyclic LN2 fracturing on HDR. It is expected to provide theoretical guidance for the cyclic LN2 fracturing application in HDR reservoirs.

Air/CO2 cooling garment: Description and benefits of use for subjects exposed to a hot and humid climate during physical activities

The severity of the hot and humid conditions to which miners are exposed increases as the depth of the work site increases.This can cause heat stress that can greatly affect the health and safety of workers.To resolve this,a cooling garment has been developed that uses an atmospheric discharge of liquid CO2 to create a cool microclimate with an average temperature of 12.5(±0.4)℃ beneath the garment.To evaluate the garment's cooling efficiency,19 male subjects participated in an experimental procedure.The two modes,cooling on and off,were compared.Significant physiological differences were found between the two modes after minute 27(p<0.05)until the end of the recovery phase for the heart rate(maximum difference of 10 beats per minute)and the internal body temperature(maximum difference of 0.33℃).It was found that the modes also affected the subjects'perceptions.The ON-mode was associated with better well-being and thermal comfort,and reduced humidity sensation.Perceptions of exertion were lower in the ON-mode condition from minute 2.The findings provide strong evidence of the ability of this cooling garment to reduce heat stress in hot and humid conditions similar to those encountered in deep mines.

Effect of Zn/Mg/Cu Additions on Hot Cracking Tendency and Performances of Al-Cu-Mg-Zn Alloys for Liquid Forging

During the process of liquid forging, a host of hot cracking defects were found in the Al-CuMg-Zn aluminum alloy. Therefore, mechanical tests and analyses by optical microscope, scanning electron microscope, and X-ray diffraction were performed to research the influences of zinc, magnesium, and copper(three main alloying elements) on hot cracking tendency and mechanical properties. It was concluded that all the three alloying elements exerted different effects on the performances of newly designed alloys. And the impact of microstructures on properties of alloys was stronger than that of solution strengthening. Among new alloys, Al-5 Cu-4.5 Mg-2.5 Zn alloy shows better properties as follows: σb=327 MPa, δ=2.7%, HB=107 N/mm^2, and HCS=40.

Influence of Medium Used during Ferritic Nitro-Carburizing of AISI H-13 Hot Work Tool Steel

Ferritic nitro-carburizing is one of the most popular surface hardening methods used to improve lifespan of hot work tool steels.Different types of mediums like gas,liquid,plasma and fluidized bed are generally used during ferritic nitro-carburizing process.In this paper,various ferritic nitro-carburizing methods were compared where gas,salt bath and fluidized are used as mediums.AISI H-13 hot work tool steel specimens were treated by using these different methods of nitro-carburizing and their performance was evaluated by using micro-structural and mechanical analysis.Optical microscopy,micro-hardness testing and X-ray stress analyzer were used for specimen characterization.Moreover,pin on disk dry sliding wear tests were performed to compare wear performance of specimens treated with different nitro-carburizing methods.It is perceived that,medium used during nitro-carburizing has significant influence on the final surface properties that can be achieved by ferritic nitro-carburizing.

Role of tensile forces in hot tearing formation of cast Al-Si alloy

The instrumented applied rod casting apparatus （ARCA） was developed to investigate the effects of tensile forces in the hot tearing formation of cast AI-Si alloys. The obtained data of tensile forces/temperature was used to identify hot tearing initiation and propagation and the fracture surface of samples was also investigated. The result shows that the applied tensile forces have a complex effect on load onset for the hot tearing initiation and propagation. During the casting solidification, the tensile forces are gradually increased with the increase of solid fraction. Under the action of tensile forces, there will appear hot tearing and crack propagation on the surface of the sample. When the tensile forces exceed the inherent strength of alloys, there will be fractures on the sample. As for the A356 alloy, the critical fracture stress is about 0.1 MPa. The hot tearing surface morphology shows that the remaining intergranular bridge and liquid films are thick enough to allow the formation of dendrite-tip bumps on the fracture surface.

Electrochemical migration behavior and mechanism of PCB-ImAg and PCB-HASL under adsorbed thin liquid films

The electrochemical migration（ECM） behavior and mechanism of immersion silver processing circuit board（PCB-ImAg）and hot air solder leveling circuit board（PCB-HASL） under the 0.1 mol/L Na2SO4 absorbed thin liquid films with different thicknesses were investigated using stereo microscopy and scanning electron microscopy（SEM）.Meanwhile,the corrosion tendency and kinetics rule of metal plates after bias application were analyzed with the aid of electrochemical impedance spectroscopy（EIS）and scanning Kelvin probe（SKP）.Results showed that under different humidity conditions,the amount of migrating corrosion products of silver for PCB-ImAg was limited,while on PCB-HASL both copper dendrites and precipitates such as sulfate and metal oxides of copper/tin were found under a high humidity condition（exceeding 85%）.SKP results indicated that the cathode plate of two kinds of PCB materials had a higher corrosion tendency after bias application.An ECM model involving multi-metal reactions was proposed and the differences of ECM behaviors for two kinds of PCB materials were compared.

Review on studies of reducing Cu-induced surface hot shortness in steel

There is an increasing trend for producing copper-containing steels, with copper being either a residual element from scraps or an intentional addition, i. e. , in weathering steel. The issue of surface hot shortness occurs during the hot working of steels containing copper, and a significant amount of work has been performed on this topic. This paper provides a review of related studies on this phenomenon. The formation mechanism, as analyzed, is the liquid metal embrittlement caused by the liquid copper penetration into austenite grain boundaries at the metal surface, where the copper originates from the selective oxidation of the steel at high temperature. On the basis of the mechanism, more importance is placed on analyzing the effect on the phenomenon by varying the controlling factors, including the heating process, alloying additions, and deformation conditions. Possible solutions to the problem are finalized, and some further work must be performed in the future.

Liquid mean velocity and turbulence in a horizontal air-water bubbly flow

The liquid phase turbulent structure of an air-water bubbly horizontal flow in a circular pipe has been investigated experimentally. Three-dimensional measurements were implemented with two "X" type probes oriented in different planes, and local liquid-phase velocities and turbulent stresses were simultaneously obtained. Systematic measurements were conducted covering a range of local void fraction from 0 to 11.7%. The important experiment results and parametric trends are summarized and discussed.

烧结机烟气循环技术

伴随着钢铁行业微利时代的到来,同行之间竞争更加激烈,国家对环保要求日益严苛,该背景下,在占钢铁企业能耗大户的烧结工序实施烟气循环烧结技术显得尤为重要。烧结烟气循环技术是将全部或选择性收集的部分温度和氧含量较高,污染物浓度较低的风箱烟气,返回到烧结烟气罩后再次进入烧结料层循环利用的技术。该技术不仅能有效利用烧结烟气余热,还能显著降低烟气中的污染物排放。以天铁360 m^(2)烧结机配备的烟气循环系统为研究对象,分析了烟气循环技术应用后对CO、SO_(2)以及NO_(x)的减排效果及机理。结果表明,烟气循环后,风箱烟气中CO的平均含量较常规烧结上升了15.6%,一方面循环烟气中本就含有少量CO,另一方面由于循环烟气相较空气其氧含量较低导致燃料不完全燃烧比例增加,自带与新生的CO随着循环烟气重新进入料层参与了烧结过程。烟气循环对SO_(2)和NO_(x)等污染物的减排率分别达到29.5%和31.2%,有效降低了烧结过程SO_(2)和NO_(x)排放量,同时热烟气的循环对提高烧结矿质量及降低燃耗有利,烧结固耗由应用前的49.01 kg/t降低到48.19 kg/t,产量提升2.2%。在烧结烟气循环技术运用后,实现了烧结提质、降耗和减排的综合效果,有助于企业满足日益严格的环保要求。

“双碳”背景下热轧厂能源管理体系构建与实施

现阶段,中国能源体系和发展模式进入崭新阶段。热轧是钢铁企业的关键工序,热轧厂绿色、低碳、高效能源体系建设尤为重要。在“双碳”背景下,通过建立健全能源管理制度、构建“1+14”能源管理模式、建设多终端能源管理平台、产能提升助力高效节能、推行节能技术革新、建立精细化多重预警机制、强化体制机制保障等多措并举,成功构建实施了绿色、低碳、高效热轧厂能源管理体系,创新了管理理念,优化了管理架构,创新了管控模式,热轧厂综合工序能耗降幅明显,取得了显著的经济效益。

生物技术对造纸法烟草薄片的浓缩液影响研究

从生物技术中提取的某些物质能够有效地去除造纸法烟草薄片的浓缩液中的有害物质。为对造纸法烟草薄片的化学组成进行合理调整,提高其质量,以产香酵母为原料,对其发酵过程中常见的化学组分及香气物质进行分析,确定最佳发酵工艺,将醇化与产香酵母发酵相结合,并进行感官评价,研究其对烟叶质量的影响。结果表明,在70℃下进行48 h的热醇化处理,可以明显增加浓香型物质的种类及含量,增加呈香物质的种类及含量。采用产香酵母发酵78小时,提取出的香气物质最多达53种,其总量达到1061.69µg/mL。采用生物技术能有效地去除浓缩液中的苯酚、氯酚、多酚类等有害物质,同时还能提高烟草薄片的品质,降低了烟草薄片中的有害物质含量。

液态金属改性微米Al-氟聚物的3D打印及性能表征

为了研究镓基液体金属(GLM)-Al-氟聚物的能量释放性能,制备了GLM质量分数分别为1%、3%、5%、7%的GLM-Al,通过3D打印获得了GLM-Al-氟聚物复合反应性材料;采用SEM、EDS、XRD、XPS、DSC-TG、高速摄影仪和万能拉伸仪对GLM-Al及GLM-Al-氟聚物的微观结构、燃烧性能、力学性能等进行测试。结果表明,质量分数3%的GLM改性的GLM-Al放热量和氧化增重均最大,分别为6181 J/g和42.92%;改性前的Al-氟聚物不能被点燃,改性后GLM-Al-氟聚物可以点燃且可以持续稳定燃烧,在当量比为3.5时的燃速最大,为6.0 mm/s;此时GLM-Al-氟聚物的抗拉强度和断裂伸长率均最大,分别为1.73 MPa、11486%,是改性前Al-氟聚物的1.5倍和1.3倍。

基于Hot-disk的液体导热系数测量装置实验研究

基于Hot-disk热物性分析仪,开发了一种应用于液体导热系数测定的装置。应用该装置对液体进行导热系数测定时,可以较好地避免自然对流的影响,且制作简便,成本低廉。使用该装置对26℃的去离子水进行了5次测量,并分析了其测量结果。最大测量误差为8.5%,最小测量误差为2.05%,测量误差平均值为5.84%,5次测试的结果平均值为0.573 1 W/m·K,与文献标准值的偏差仅为3.72%。测试精确度较公式法取得很大进步,可以满足工程应用。

液态CO_(2)-水蒸气循环冲击煤体增透及瓦斯抽采效果模拟

【目的】为解决液态CO_(2)煤层增透技术应用时煤层内部孔隙水受冷凝结为冰阻塞瓦斯运移通道这一问题,提出液态CO_(2)-高温水蒸气冷热循环冲击煤体增透技术。【方法】利用低场核磁共振仪、煤岩渗透率自动测试仪、接触角测试仪和三维CT扫描仪分析液态CO_(2)-高温水蒸气冷热循环冲击煤体渗透率演化规律。【结果和结论】结果表明:(1)液态CO_(2)-高温水蒸气冷热循环冲击煤体T2曲线面积随冷热循环冲击次数增加而增加。(2)煤体渗透率增量与液态CO_(2)-高温水蒸气冷热循环冲击次数指数相关,循环冲击次数增加,煤体渗透性和润湿性均增强。(3)液态CO_(2)-高温水蒸气冷热循环冲击次数达到12次时,渗流孔体积比例增加23.57%,渗透率增加0.009 3×10^(-3)μm^(2),接触角减小39.45°。(4)煤体渗透性与渗流孔体积比例、接触角相关,渗流孔体积比例与煤体渗透率正相关,接触角与煤体渗透率指数相关。基于实验研究结果,利用COMSOL软件数值模拟低温液态CO_(2)-高温水蒸气冷热循环冲击煤层工程现场应用。依据试验结果确定恢复到室温25℃时的有效作用半径为0.719 8 m,以此数据模拟矿井煤层瓦斯抽采,结果显示煤层温度与瓦斯抽采效率成正比。试验及模拟结果揭示了液态CO_(2)-高温水蒸气冷热循环冲击煤体增透技术的现场钻孔布置及瓦斯抽采运移规律,为该技术下一步现场应用提供参考。

液体火箭发动机热试车启动中导流锥对燃气管路流动特性影响研究

双推力室液体火箭发动机启动过程中,若出现两支管流量分配不均等现象,极易引起点火失败,造成重大损失。因此,燃气管路分叉处内部流动特性和在分叉处布置导流锥对改善流动特性影响的研究具有重要意义。本文针对某双推力室液体火箭发动机热试车启动过程中的燃气管路,以试验数据作为边界条件,开展了瞬态流动数值仿真研究。结果表明,火箭发动机热试车启动过程中,燃气管路流动呈现出4个典型阶段,分别为点火前的平稳期、点火后的一次上升期、下降期和二次上升期。在启动过程中,无导流锥时,导流罩进口存在预旋回流区、一侧出口存在滞止回流区,导流罩与燃气支管衔接处内侧存在转弯回流区,三者相互作用是造成两支管间压力分布不对称及出口质量流量分配不平衡的主要原因;有导流锥时,预旋回流区被导流锥约束而缩小,滞止回流区消失。有导流锥与无导流锥时相比,在启动过程中约0.2 s与0.6 s时刻,两支管对称测点压差均值分别降低约80.0%与80.0%,两支管出口质量流量差值分别降低约55.0%与80.8%。导流锥有效改善了流动特性,使得两支管压力分布的对称性提高,流量分配平衡性增强。导流锥对双推力室液体火箭发动机稳定性提高有重要作用。

770 MPa级调质铸钢液态金属致脆失效原因及相应防护对策

采用金相显微镜、电子扫描显微镜等对某大型截面铸钢工件裂纹成因进行了分析。结果表明:开裂高强度调质铸钢,在热浸锌过程中,基体产生了垂直于表面的裂纹,裂纹长度约为3 mm,且裂纹沿晶开裂。能谱结果表明,裂纹中富含大量锌,为典型的液态金属致脆现象。针对此情况,在热浸锌工艺、焊接工艺、成型工艺、涂装体系等方面给出了避免产生液态金属致脆的防护对策。

冷热喷雾疗法对头面部烧伤患者的康复效果

目的探讨冷热喷雾疗法对头面部烧伤患者的康复效果。方法选择2022年1月-2023年10月我科收治的头面部Ⅱ度烧伤患者120例,采用随机数字表法分为观察组和对照组,各60例。两组患者头面部创面均采用暴露疗法,给予抗菌、生长因子等药物治疗,对照组入院后即进行创面湿敷冷疗30min,观察组早期采用冷喷治疗,每日2次,每次30min,持续3天后使用热喷治疗,每日2次,每次30min,持续至患者创面脱痂。观察两组头面部创面疼痛、肿胀、脱痂和瘙痒情况。结果观察组疼痛程度轻于对照组,肿胀程度低于对照组,痂皮脱落时间少于对照组,瘙痒程度轻于对照组(P<0.05)。结论头面部烧伤患者早期进行冷喷治疗能减轻创面疼痛,后期进行热喷治疗可缓解创面瘙痒症状,促进创面恢复,效果良好。

复方黄柏液联合磺胺嘧啶银乳膏对烧伤合并多重耐药菌创面感染患者创面愈合及炎性因子的影响

目的探讨复方黄柏液联合磺胺嘧啶银乳膏对烧伤合并多重耐药菌(MDROS)创面感染患者创面愈合及炎性因子的影响。方法选取2019年7月—2022年1月本院收治的86例烧伤合并MDROS创面感染患者,采用数字奇偶法分为对照组(给予磺胺嘧啶银乳膏治疗)和观察组(给予复方黄柏液联合磺胺嘧啶银乳膏治疗),每组各43例。比较2组患者创面中医症状评分、创面面积、创面愈合率、炎性因子[降钙素原(PCT)、C反应蛋白(CRP)]水平、创面分泌物细菌培养结果和不良反应。结果治疗后观察组主症、次症评分及总分均低于对照组(P<0.05),观察组总有效率高于对照组(P<0.05);治疗后观察组创面面积低于对照组(P<0.05),观察组创面愈合率高于对照组(P<0.05);治疗后观察组PCT和CRP水平均低于对照组(均P<0.05);治疗后观察组革兰阳性菌、革兰阴性菌感染病例数低于对照组(P<0.05);2组不良反应发生率相近(P>0.05)。结论烧伤合并MDROS创面感染患者采用复方黄柏液、磺胺嘧啶银乳膏联合治疗有利于促进创面愈合,降低炎性因子水平,控制创面细菌感染,缓解临床症状,提高临床疗效,且安全可靠。

液体火箭发动机故障诊断系统冗余容错技术研究综述

综述了液体火箭发动机故障诊断系统冗余容错技术研究,介绍了液体火箭发动机故障诊断系统在航天任务中的重要性及其不断发展的需求,强调了高可靠性和安全性对于航天任务成功的关键作用,详细分析了当前国内外在这一领域的研究现状,展示了不同国家和研究机构在故障诊断系统冗余容错技术方面的最新进展和具体应用实例,阐述了冗余容错技术对于火箭发动机故障诊断系统的重要性并探讨了该技术的发展历程、关键技术及当前研究成果;通过对比几种经典冗余容错手段,指出各冗余结构对于火箭发动机故障诊断系统的可行性与优缺点,详细介绍了发动机故障诊断系统的双机热备实现方案,为相关研究者提供参考依据;从理论基础到实际应用,从当前研究遇到的技术挑战再到未来发展方向的展望,为液体火箭发动机故障诊断系统冗余容错技术的研究提供了全面的综述和分析。