Analysis of sensitivity to hydrate blockage risk in natural gas gathering pipeline

During the operational process of natural gas gathering and transmission pipelines,the formation of hydrates is highly probable,leading to uncontrolled movement and aggregation of hydrates.The continuous migration and accumulation of hydrates further contribute to the obstruction of natural gas pipelines,resulting in production reduction,shutdowns,and pressure build-ups.Consequently,a cascade of risks is prone to occur.To address this issue,this study focuses on the operational process of natural gas gathering and transmission pipelines,where a comprehensive framework is established.This framework includes theoretical models for pipeline temperature distribution,pipeline pressure distribution,multiphase flow within the pipeline,hydrate blockage,and numerical solution methods.By analyzing the influence of inlet temperature,inlet pressure,and terminal pressure on hydrate formation within the pipeline,the sensitivity patterns of hydrate blockage risks are derived.The research indicates that reducing inlet pressure and terminal pressure could lead to a decreased maximum hydrate formation rate,potentially mitigating pipeline blockage during natural gas transportation.Furthermore,an increase in inlet temperature and terminal pressure,and a decrease in inlet pressure,results in a displacement of the most probable location for hydrate blockage towards the terminal station.However,it is crucial to note that operating under low-pressure conditions significantly elevates energy consumption within the gathering system,contradicting the operational goal of energy efficiency and reduction of energy consumption.Consequently,for high-pressure gathering pipelines,measures such as raising the inlet temperature or employing inhibitors,electrical heat tracing,and thermal insulation should be adopted to prevent hydrate formation during natural gas transportation.Moreover,considering abnormal conditions such as gas well production and pipeline network shutdowns,which could potentially trigger hydrate formation,the installation of methanol injection connectors remains necessary to ensure production safety.

Estimation of enhanced low dose rate sensitivity mechanisms using temperature switching irradiation on gate-controlled lateral PNP transistor

The mechanisms occurring when the switched temperature technique is applied,as an accelerated enhanced low dose rate sensitivity(ELDRS)test technique,are investigated in terms of a specially designed gate-controlled lateral PNP transistor(GLPNP)that used to extract the interface traps(Nit)and oxide trapped charges(Not).Electrical characteristics in GLPNP transistors induced by ^(60)Co gamma irradiation are measured in situ as a function of total dose,showing that generation of Nit in the oxide is the primary cause of base current variations for the GLPNP.Based on the analysis of the variations of Nit and Not,with switching the temperature,the properties of accelerated protons release and suppressed protons loss play critical roles in determining the increased Nit formation leading to the base current degradation with dose accumulation.Simultaneously the hydrogen cracking mechanisms responsible for additional protons release are related to the neutralization of Not extending enhanced Nit buildup.In this study the switched temperature irradiation has been employed to conservatively estimate the ELDRS of GLPNP,which provides us with a new insight into the test technique for ELDRS.

Uniaxial compressive behavior of equal channel angular pressing Al at wide temperature and strain rate range

Uniaxial compressive experiments of ultrafine-grained Al fabricated by equal channel angular pressing(ECAP) method were performed at wide temperature and strain rate range. The influence of temperature on flow stress, strain hardening rate and strain rate sensitivity was investigated experimentally. The results show that both the effect of temperature on flow stress and its strain rate sensitivity of ECAPed Al is much larger than those of the coarse-grained Al. The temperature sensitivity of ultrafine-grained Al is comparatively weaker than that of the coarse-grained Al. Based on the experimental results, the apparent activation volume was estimated at different temperatures and strain rates. The forest dislocation interactions is the dominant thermally activated mechanism for ECAPed Al compressed at quasi-static strain rates, while the viscous drag plays an important role at high strain rates.

Effect of body material and temperature variation on the performance of the time delay pyrotechnic compositions

Significance of body material and temperature variation on burning time and burning rate of Si/Pb O/Pb_3O_4/FG and B/BaCrO_4/FG pyrotechnic delay compositions were experimentally studied. Brass and stainless steel were used as delay body materials. High resolution oscilloscope and a customized chronometer were simultaneously used for the measurement of burning time and burning rate. Results reveal that brass material with controlled column dimensions reduced the variation in burning time of Si/Pb O/Pb_3O_4/FG delay mixture from 7.43% to 4.17% and that of B/Ba CrO_4/FG mixture from 16.83% to 9.39%.Similarly the variation in burning rate was reduced from 7.57% to 4.12% and from 17% to 9.69% for Si/Pb O/Pb_3O_4/FG and B/BaCrO_4/FG mixtures respectively. Si/PbO/Pb_3O_4/FG delay mixture was also subjected to temperature ranging from -54℃ up to+100℃. The burning rate of this composition varied linearly with temperature. Burning rate increased from 28.01 mm/s to 34.38 mm/s when the temperature was varied from -54℃ to +100℃.

Flow behavior and fracture of Al−Mg−Si alloy at cryogenic temperatures

The tensile and fracture behaviors of AA6061 alloy were investigated in order to provide quantitative data about this alloy at cryogenic temperatures.Specimens of AA6061 alloy were solution heat treated before tensile tests at 298,173 and 77 K and tested at strain rates in the range from 0.1 to 0.0001 s^(−1).The results indicate the suppression of the Portevin−Le Chatelier(PLC)effect and dynamic strain aging(DSA)at 77 K.In contrast,at 298 K,a remarkable serrated flow,characteristic of the PLC effect,is observed.Furthermore,the tensile behavior at 77 K,compared with that observed at 173 and 298 K,shows a simultaneous increase in strength,uniform elongation,modulus of toughness,strain-hardening exponent and strain rate sensitivity,which is related to a decrease in the dynamic recovery rate at low temperature.These responses are reflected on the fracture morphology,since the dimple size decreases at 77 K,while the area covered by dimples increases.Comparisons of the Johnson−Cook model show that a good agreement can be obtained for tests at 173 and 77 K,in which DSA is suppressed.

Effect of CO_(2) dilution on laminar burning velocities,combustion characteristics and NO_(x) emissions of CH_(4)/air mixtures

The laminar combustion characteristics of CH_(4)/air premixed flames with CO_(2) addition are systemically studied.Experimental measurements and numerical simulations of the laminar burning velocity(LBV)are performed in CH_(4)/CO_(2)/Air flames with various CO_(2) doping ratio under equivalence ratios of 1.0–1.4.GRI 3.0 mech and Aramco mech are employed for predicting LBV,adiabatic flame temperature(AFT),important intermediate radicals(CH_(3),H,OH,O)and NO_(x) emissions(NO,NO_(2),N2O),as well as the sensitivity analysis is also conducted.The detail analysis of experiment and simulation reveals that as the CO_(2) addition increases from 0%to 40%,the LBVs and AFTs decrease monotonously.Under the same CO_(2) doping ratio,the LBVs and AFTs increase first and then decrease with the increase of equivalence ratio,and the maximum of LBV is reached at equivalence ratio of 1.05.The mole fraction tendency of important intermediates and NO_(x) with equivalence ratio and CO_(2) doping ratio are similar to the LBVs and AFTs.Reaction H+O_(2)⇔O+OH is found to be responsible for the promotion of the generation of important intermediates and NO_(x) under the equivalence ratios and CO_(2) addition through sensitivity analysis.The sensitivity coefficients of elementary reactions that the increasing of CO_(2) doping ratio promotes or inhibits formation of intermediate radicals and NO_(x) decreases.

Effect of temperature on mechanical behavior of AZ31 magnesium alloy

Strain rate sensitivity and tension/compression asymmetry of AZ31 magnesium alloy at different temperatures and strainrates were investigated.Both of mechanical behaviors are temperature dependent.Strain rate sensitivity increases with increasingtemperature.Thermally activated slip is the source of strain rate sensitivity.At the temperature below or near 373 K,strain ratesensitivity is very little.Tension/compression asymmetry in yielding decreases with increasing temperature.Twinning is the reasonof tension/compression asymmetry.At the temperature above or near 573 K,the material shows little tension/compressionasymmetry of the flow stress.

Factors Influencing the Outcrossed Seed-Setting Obstacles of Photo-thermo Sensitive Genie Male Sterile Rice

Using photo-thermo sensitive genie male rice (PTGMS) Pei' ai 64S, W7415S, W6154S, N26S, Annong S, Nongken 58S, 7001S and 5088S as female parents and conventional indica lines 8258 and U89 as male parents, the factors affecting outcrossed seed-setting were analyzed. The PTGMS had obstacles in outcrossed seed setting influenced by inheritance and environment at varying degrees. Environmental temperature was regarded as the main factor that resulted in the outcrossed seed-setting obstacles. The sensitive stage was at the early stage of grain filling for outcrossed seed setting. There existed remarkable differences at the sensitivity stage, the duration of sensitive period, the sensitive level and the effective level of outcrossed seed-setting obstacles caused by environmental temperature among different PTGMS lines. Therefore, attention should be paid to outcrossed seed-setting obstacles in selection and utilization of PTGMS lines.

EFFECT OF HYDROGEN ON HIGH TEMPERATURE PLASTICITY OF Ti-6Al-4V ALLOY

The effects of various hydrogen contents on the flow stress(σ),strain rate sensitivity expo- nent(m)and the tensile elongation(δ)of Ti-6Al-4V alloy were studied.The microstructure of the alloy was also investigated.The results indicate that,a suitable amount of hydrogen in the alloy can reduce the flow stress in the temperature range 800—860℃. Consequently,the superplastic temperature can be decreased and the ductility improved.

Spatial distribution and driving factors of sediment net nitrogen mineralization in riparian zone of the Three Gorges Reservoir

Inorganic nitrogen(N)loss through sediment N mineralization is important for eutrophication surrounding riparian zone.Sediment physicochemical properties have been changed at water-level elevation in riparian zone of the Three Gorges Reservoir(TGR)due to differences in hydrological stress and human activity intensity.However,spatial distribution and driving factor of net N mineralization rate(Nmin)and its temperature sensitivity(Q10)based on the changes in sediment physicochemical properties are still unclear at waterlevel elevation in the riparian zone.A total of 132 sediment samples in the riparian zone were collected including 11 transections and 12 water-level elevations on basin scale of the TGR during drying period,to conduct a 28-day incubation at 15℃,22℃,29℃and 36℃.Nmin,total N(TN)and substrate quality(SQ)increased with water-level elevation,while Q10 showed an opposite trend(P<0.001).Results of the structural equation model showed that water-level elevation had direct positive effects on TN and SQ(P<0.01).In addition,TN was the major factor that had a direct positive effect on Nmin,and SQ was the crucial factor that had a direct negative effect on Q10(P<0.001).In conclusion,increases in TN and SQ were major driving factors of Nmin and its Q10 at water-level elevation,respectively,in riparian zone of the TGR during drying period.

Dynamic Tensile Behavior and Constitutive Modeling of TC21 Titanium Alloy

The dynamic tensile behaviors of a newly developed Ti-6 Al-2 Sn-2 Zr-3 Mo-1 Cr-2 Nb-Si alloy（referred as TC21 in China） over a wide range of strain rates from quasi-static to dynamic regimes(0.001-1 200 s-1) at different temperatures were experimentally investigated. A split Hopkinson tension bar apparatus and a static material testing system were utilized to study the stress-strain responses under uniaxial tension loading condition. The experimental results indicate that the tensile behavior of TC21 titanium alloy is dependent on the strain rate and temperature. The values of initial yield stress increase with increasing strain rate and decreasing temperature. The effects of strain rate and temperature on the initial yield behavior are estimated by introducing two sensitivity parameters. The phenomenological-based constitutive model, Johnson-Cook model, is suitably modified to describe the rate-temperature dependent constitutive behavior of TC21 titanium alloy. It is observed that the modified model is in good agreement with the experimental data subjected to the investigated range of strain rates and temperatures.

环氧树脂固化促进剂的研究及应用

环氧树脂由于其优异的性能,使其在胶粘剂、涂层以及复合材料等领域获得了广泛的应用。为了提高固化速率,同时对于一些热敏感的部件来说,温度是一个重要的指标,需要降低固化温度,因此,加入固化促进剂是必要的。本文主要综述了环氧树脂固化促进剂的研究进展及应用情况,包括叔胺及其盐类固化促进剂、三苯基膦及其鏻盐固化促进剂、取代脲固化促进剂、咪唑及其盐类固化促进剂、三氟化硼胺络合物固化促进剂等,并指出了未来的发展方向。

不同放牧强度对荒漠草原土壤呼吸速率及其温度敏感性的影响

在气候变暖影响下,研究放牧对草原土壤呼吸速率(Soil respiration rate,Rs)及其温度敏感性系数(Temperature sensitivity,Q 10)的影响,对阐述草原生态系统碳收支具有重要意义。以荒漠草原为研究对象,设置无牧、轻度放牧和重度放牧3个处理,运用全自动变温培养土壤温室气体在线测量系统,测定不同放牧处理区0~30 cm土壤变温(-10~25℃)培养下的呼吸速率并计算Q 10。结果表明:放牧处理9年后的Rs及其Q 10值为:重度放牧Rs显著高于无牧和轻度放牧(P<0.05),重度放牧显著增加0~10 cm土层Q 10值;与无牧相比,轻度放牧显著降低20~30 cm土层Q 10值;主成分分析表明:放牧强度主要影响土壤pH值、粉粒含量,进而影响Rs。轻度放牧可降低土壤呼吸Q 10值,从而减少荒漠草原土壤CO_(2)排放。因此,建议实施轻度放牧管理策略以减少荒漠草原的碳排放。

含MgO膨胀剂的水泥砂浆在恒温和变温养护制度下的限制膨胀率

温度对MgO膨胀剂在水泥基材料中补偿效果的影响至关重要。本文通过测试不同养护制度下水泥砂浆的限制膨胀率、水化产物矿物组成、产物形貌和分布以及MgO膨胀剂的水化程度,揭示了MgO膨胀剂在水泥基材料中的温度敏感性。结果表明,随着养护温度升高,含8%(质量分数)中速型MgO水泥砂浆的限制膨胀率显著增加,特别是在50℃养护条件下,其28 d限制膨胀率是25℃下的1.7倍。不同养护制度对MgO膨胀性的影响规律存在差异,在高温升-慢冷却的变温养护制度中,含快速型MgO的水泥砂浆限制膨胀率最大,且降温过程膨胀率降低趋势明显,而在低温升-快冷却的变温养护制度下,体系水化持续进行,MgO膨胀效果可持续发挥。此外,MgO在水泥净浆中的反应程度也随养护温度的升高而增加,为25%~65%,水化产物Mg(OH)_(2)主要以凝胶状态存在,但随着温度升高到50℃,部分凝胶状的Mg(OH)_(2)转化为片状晶体,从而进一步优化了水泥基材料的微观结构和膨胀性能。该研究为理解和优化MgO膨胀剂在水泥基材料中的应用提供参考。

温控化学压裂液滤失特性实验研究

为研究温控化学压裂液的滤失特性,首次利用动态滤失仪分析了相变压裂液体积分数、温度、滤失压差、渗透率对滤失过程的影响。结果表明,相变压裂液体积分数越小、温度越高、滤失压差越大、渗透率越高,化学压裂液的滤失系数越大,且相变压裂液体积分数影响相对较小,而滤失压差和渗透率影响较为显著。因此,高温储层可通过注前置液的方式降低化学压裂液的滤失,且在高渗储层或采用大排量施工时有必要采取一定的降滤措施以提高液体效率。

凋落物C/N对土壤有机碳矿化的影响

凋落物输入会影响土壤有机碳(SOC)矿化过程,其影响程度主要受凋落物C/N、土壤肥力和温度条件的影响,然而,这三因素的综合影响仍不清楚。以低肥力土壤(LF)和高肥力土壤(HF)为研究对象,分别添加7种不同C/N的凋落物,并设置培养温度为23℃和33℃,进行恒温避光培养,期间动态监测CO_(2)排放的变化,以揭示SOC矿化过程应对三因子的响应机制。结果显示,凋落物添加显著增加CO_(2)峰值排放速率,且与C/N>30的凋落物相比,添加C/N<30的凋落物对CO_(2)的峰值排放速率的促进作用更显著。CO_(2)峰值排放速率同时受土壤肥力和培养温度影响,HF-33℃条件下的CO_(2)峰值排放速率最高。添加C/N<30的凋落物显著增加了CO_(2)累积排放量,在LF-23℃、LF-33℃、HF-23℃和HF-33℃条件下,最大增幅分别为407%、304%、345%和160%。相关分析显示,SOC矿化率与凋落物C/N间呈负相关关系,这说明低质量凋落物会抑制SOC矿化。在LF-23℃、LF-33℃、HF-23℃和HF-33℃处理下,与凋落物C/N最低的CN1相比,添加C/N最高的CN7后,SOC矿化率的降幅分别达3.53、3.04、1.71和2.06倍。土壤肥力影响SOC矿化,HF的SOC矿化率较LF高1.29-2.66倍。培养温度对SOC矿化的影响在HF中表现出显著差异,与CK相比,在HF中添加凋落物显著降低了SOC矿化温度敏感性(Q10)。综合PLS-PM模型可知,SOC矿化是凋落物C/N、土壤肥力和培养温度综合作用的结果。其中,凋落物的C/N比对SOC矿化产生显著的负效应,土壤肥力则对SOC矿化产生主要的正效应,而温度的正效应则相对较小。研究结果有助于进一步理解不同土壤肥力和温度背景下,C/N不同的外源有机物输入对SOC矿化的影响及其背后的综合效应。

MSCR试验对不同老化程度高黏沥青高温性能分析

基于多重应力蠕变恢复试验(MSCR)研究3种高黏沥青在不同老化程度下的高温性能的影响,采用蠕变恢复率及不可恢复柔量评价不同老化条件下高黏沥青高温抵抗外界荷载作用能力,并分析高黏沥青的应力敏感性。研究表明:经短期老化与长期老化后,高黏沥青老化后变得更坚硬,且Ⅰ型高黏沥青在不同应力和不同老化条件下抗变形能力最优。不同老化条件下,Ⅰ型与Ⅱ型高黏沥青的平均蠕变恢复率均高于SBS改性沥青,平均不可恢复柔量均小于SBS改性沥青,表明添加高黏改性剂对提高沥青的弹性恢复性能与高温抗流动变形能力具有明显作用。3种高黏沥青在不同老化程度下的应力敏感性大小为Ⅱ型<Ⅰ型<SBS改性沥青,与其蠕变恢复率大小顺序相反,说明应力敏感性与平均蠕变恢复率具有良好的负相关性。结果表明:多重应力蠕变恢复试验考虑不同老化条件下高黏改性沥青的高温黏弹特性,采用平均蠕变恢复率、平均不可恢复柔量和应力敏感系数指标,对全面评价高黏改性沥青的不同老化程度下高温性能具有重要作用。

RDX-CMDB推进剂燃速温度敏感系数的实验研究

为了揭示RDX-CMDB推进剂中各常见组分对其燃速温度敏感系数的影响规律,制备了一系列含RDX、铝粉及燃烧催化剂的CMDB推进剂样品。采用氮气靶线法测得其在2~14MPa下的燃速温度敏感系数（σp）。讨论了RDX含量、铝粉、燃烧催化剂对RDX-CMDB推进剂燃速温度敏感系数的影响。结果表明,提高工作压强、增加RDX含量、添加燃烧催化剂均有助于降低RDX-CMDB推进剂在一定初始条件下的燃速温度敏感系数。配方中引入铝粉后可降低中低压下RDX-CMDB推进剂的燃速温度敏感系数,且燃速温度敏感系数几乎不随压强变化而变化。选用含邻苯二甲酸铅和没食子酸铋锆作燃烧催化剂,均可在2~10MPa下降低RDX-CMDB推进剂的燃速压强指数,同时降低燃速温度敏感系数。

高氯酸铵(AP)基复合改性双基(AP/CMDB)推进剂燃速控制与降感研究

测试了加入不同粒度AP、不同品种催化剂的推进剂的燃速和加入不同降感材料的推进剂的机械感度,分析了影响AP/CMDB推进剂燃烧性能和机械感度的主要影响因素。结果表明AP粒度是影响AP/CMDB推进剂燃速的主要因素;加入纳米催化剂与某含铜化合物复配能进一步提高燃速,燃速压强指数不提高;推进剂中含能材料的比例和材料颗粒形貌对推进剂机械感度有明显影响。采用某低感增塑剂部分代替NG并加入某高导热碳基材料进行协同降感,能明显降低AP/CMDB推进剂的摩擦感度和撞击感度。

初始油温对变压器油燃烧特性的影响

为了研究变压器油初始油温对燃烧特性的影响,搭建了油池火燃烧实验平台,开展了不同初始油温及不同油池直径的池火实验,系统地分析了初始油温对油池火灾发展规律的影响,具体探讨了燃烧发展阶段、燃烧速率以及沸腾层厚度等参数随初始油温的变化规律。结果表明,变压器油池火的整个发展过程可分为:初始发展阶段、稳定燃烧阶段和火焰熄灭阶段。对于初始发展阶段,随着初始油温的升高,燃烧速率会不断增加,这主要是由于初始油温的升高降低了用于加热油品的热量;对于稳定燃烧阶段,燃烧速率会随着初始油温的升高而增加,但增幅较小。实验尺度范围内,前两个阶段的燃烧速率都会随着燃烧尺度的增加而显著增加。对于稳定燃烧阶段,除了直径20 cm的油池外,变压器油的沸腾层厚度接近2.17 mm,与初始油温无关。因此,在变电站消防设计中,应提高变压器火灾发展初期的灭火效率;同时,采用相应的阻隔措施避免泄漏油品的扩散蔓延。