Analysis of Gas Flow Rate and Pressure Loss of Medical Mask Differential Pressure Tester

The objective of this study is to find a suitable method to overcome the pressure loss problem in the gas pipe during the gas exchange detection of medical masks.Based on the European Standards EN 14683,the parameters of a medical mask differential pressure tester were selected,subsequently two schemes of gas pipe layouts were designed,including four kinds of pipe diameter which are 4,5,6.5,and 8mm respectively.Lastly,the models of each scheme were established and imported into Fluent,and the relevant parameters were set for simulation.After data analysis,the results showed that among the four different pipe diameters,the pressure loss of 8mm diameter of the pipe was lower in both the schemes,additionally the pressure loss of the second scheme(the gas pipe was short and smooth)was lower under the same pipe diameter.At the flow rate of v=8L/min,the pressure loss from the inlet to the measurement point is less than 200Pa,and the estimated measurement error is less than 1.5%.In conclusion,shortening the length of the pipe,and increasing the diameter of the pipe can reduce the gas pressure loss,subsequently improve the measurement accuracy of the medical mask differential pressure tester.

Experimental Analysis of the Flow Characteristics of an Adjustable Critical-Flow Venturi Nozzle

The response of an adjustable critical-flow Venturi nozzle is investigated through a set indoor experiments aimed to determine the related critical flow rate,critical pressure ratio,and discharge coefficient.The effect of a variation in the cone displacement and liquid content on the critical flow characteristics is examined in detail and it is shown that the former can be used to effectively adjust the critical flow rate.The critical pressure ratio of the considered nozzle is above 0.85,and the critical flow control deviation of the gas flow is within±3%.Liquid flow can reduce the gas critical mass flow rate accordingly,especially for the cases with larger liquid volume and lower inlet pressure.The set of results and conclusions provided are intended to support the optimization of steam injection techniques in the context of heavy oil recovery processes.

Analysis of Maximum Liquid Carrying Capacity Based on Conventional Tubing Plunger Gas Lift

China’s unconventional gas fields have a large number of low-productivity and low-efficiency wells, many of whichare located in remote and environmentally harsh mountainous areas. To address the long-term stable productionof these gas wells, plunger-lift technology plays an important role. In order to fully understand and accurately graspthe drainage and gas production mechanisms of plunger-lift, a mechanical model of plunger-liquid column uplift inthe plunger-lift process was established, focusing on conventional plunger-lift systems and representative wellboreconfigurations in the Linxing region. The operating casing pressure of the plunger-lift process and the calculationmethod for the maximum daily fluid production rate based on the work regime with the highest fluid recovery ratewere determined. For the first time, the critical flow rate method was proposed as a constraint for the maximumliquid-carrying capacity of the plunger-lift, and liquid-carrying capacity charts for conventional plunger-lift withdifferent casing sizes were developed. The results showed that for 23/8 casing plunger-lift, with a well depth ofshallower than 808 m, the maximum drainage rate was 33 m3/d;for 27/8 casing plunger-lift, with a well depth ofshallower than 742 m, the maximum drainage rate was 50.15 m3/d;for 31/2 casing plunger-lift, with a well depthof shallower than 560 m, the maximum drainage rate was 75.14 m3/d. This research provides a foundation for thescientific selection of plunger-lift technology and serves as a decision-making reference for developing reasonableplunger-lift work regimes.

On the Development of a Model for the Prediction of Liquid Loading in Gas Wells with an Inclined Section

The ability to predict liquid loading in horizontal gas wells is of great importance for determining the time of drainage and optimizing the related production technology.In the present work,we describe the outcomes of experiments conducted using air-water mixtures in a horizontal well.The results show that the configuration with an inclined section is the most susceptible to liquid loading.Laboratory experiments in an inclined pipe were also conducted to analyze the variation of the critical gas flow rate under different angles,pressure and liquid volume(taking the equal liquid volume at inlet and outlet as the criterion for judging on the critical state).According to these results,the related angle of the inclined section ranges from 45°to 60°.Finally,a modified approach based on the Belfroid model has been used to predict the critical gas flow rate for the inclined section.After comparison with field data,this modified model shows an accuracy of 96%,indicating that it has better performances with respect to other models used in the past to predict liquid loading.

Delivery of inert gas through a vertical borehole using inert gas generator: A theoretical study

The delivery of the inert gas through a vertical borehole using inert gas generator or IGG is investigated.Potential limitations and/or transient effects are highlighted.During the analysis,the borehole diameter,borehole length,type of borehole and partial condensation prior to entering the borehole were varied.A choked flow will occur for a contraction exit or borehole of 0.3 m in diameter if no condensation prior to the contraction occurs.If partial condensation takes place,a borehole diameter of 0.3 m will be possible if almost 50%of the water vapour condensates.However,pressure losses along boreholes with a diameter of 0.3 or 0.4 m are significant and could pose a challenge if trying to mitigate the pressure losses.Adding a booster fan prior to the inlet of the 0.4 m lined borehole would still be a challenge.The corresponding case with a 0.5 m borehole presents much more favourable pressure losses.The 0.5 m diameter lined borehole should be regarded as the lower threshold.The rapid heating of the unlined borehole surface will increase the risk of thermal spallation and possibly imposing restrictions.Understanding the mechanisms during gas delivery will increase the likelihood of a successful inertisation.

Research of Drainage Gas Recovery Technology in Gas Wells

Drainage gas recovery technology is the main method of gas recovery process in gas field, which has domestically and internationally been the main gas recovery processing measure in later stage of gas field production. In this context, produced water or condensate liquid will not be carried out of pit shaft by natural gas with the gradual drop of gas reservoir pressure and natural gas flow velocity, thus they will remain in pit shaft and form the so-called “gas well gathered liquid”. This fluid severely affects natural gas output and leads to the decline of oil field economic benefits, thus drainage gas recovery measure must be taken to increase gas well or even gas field output. It becomes the primary problem to be solved to select the best drainage gas recovery measure which can maximize gas field benefits and optimize gas well safety.

Oxidation Kinetics of Aluminum Powders in a Gas Fluidized Bed Reactor in the Potential Application of Surge Arresting Materials

In this technical paper, the oxidation mechanism and kinetics of aluminum powders are discussed in great details. The potential applications of spherical aluminum powders after oxidation to be part of the surging arresting materials are discussed. Theoretical calculations of oxidation of spherical aluminum powders in a typical gas fluidization bed are demonstrated. Computer software written by the author is used to carry out the basic calculations of important parameters of a gas fluidization bed at different temperatures. A mathematical model of the dynamic system in a gas fluidization bed is developed and the analytical solution is obtained. The mathematical model can be used to estimate aluminum oxide thickness at a defined temperature. The mathematical model created in this study is evaluated and confirmed consistently with the experimental results on a gas fluidization bed. Detail technical discussion of the oxidation mechanism of aluminum is carried out. The mathematical deviations of the mathematical modeling have demonstrated in great details. This mathematical model developed in this study and validated with experimental results can bring a great value for the quantitative analysis of a gas fluidization bed in general from a theoretical point of view. It can be applied for the oxidation not only for aluminum spherical powders, but also for other spherical metal powders. The mathematical model developed can further enhance the applications of gas fluidization technology. In addition to the development of mathematical modeling of a gas fluidization bed reactor, the formation of oxide film through diffusion on both planar and spherical aluminum surfaces is analyzed through a thorough mathematical deviation using diffusion theory and Laplace transformation. The dominant defects and their impact to oxidation of aluminum are also discussed in detail. The well-controlled oxidation film on spherical metal powders such as aluminum and other metal spherical powders can potentially become an important part of switch devices of surge arresting materials, in general.

不同特征波纹管内流动特性分析

为探究不同特征波纹管内部流场的分布特性,基于ANSYS CFX软件,采用进口质量流量和自由出流的数值计算条件,通过对k-ε湍流模型的数值模拟,揭示了不同弯度、波节数和大小的波纹管内部流动特性和压力场分布规律,计算了相应工况下的水头损失。结果表明:(1)波纹管的弯度、波节数和大小都对其内部流场和产生的水头损失有较大影响;(2)不同弯度波纹管内部流体域的静压和流速分布趋势整体相同,从进口至出口,管内流体的静压和流速逐渐减小,随着弯度增加,进口端流体的静压逐渐增大,出口端流体的静压逐渐减小,不同弯度波纹管波节边缘流体流速都较小,中间部位流体的流速较大;(3)波纹管弯度为180°时,随着波节数的增加,管内流体域静压的变化趋势整体相同,平均最大流速呈递增趋势;(4)波纹管弯度为180°且波节数为25时,随着波纹管整体逐渐缩小,管内流体静压与流速迅速增大,X-Y截面流体静压与流速变化趋势整体不变;(5)波纹管内流场产生的水头损失与弯度和波节数呈正相关,与大小呈负相关。为波纹管的优化设计和改进以及安装使用提供参考与合理建议。

高压含水气井两相流态节流判断与控制方法

井筒气水两相管流节流前后动态特性分析与控制,对保障致密气等高压含水气井高效稳定安全开采和水合物防治具有重要意义。考虑等熵绝热、等压热容、等容热容、不同井深节流能量等因素,推导气水两相流体流经喷嘴的能量、动能和温度动态变化等热力学微分方程组,建立高压含水气井两相节流能量、节流系统热量、节流物质平衡和流体质量流量变化等井下节流场数学模型,提出一种气水两相井筒节流前后动态特性分析与控制方法,为优化井下节流器及其节流喷嘴的结构参数和保障气井流动安全提供理论依据。最后依据数值模拟手段及其判断结果,以鄂尔多斯盆地东缘大宁-吉县区块为例进行验证,以揭示高压含水气井喷嘴尺寸和深度、含水率、节流前压力和温度对节流前后动态特性的影响规律。结果表明:高压含水气井气水两相流体质量流量先是随节流压力比减小而呈指数级增大,并在压力比降至0.55阈值附近时达到最大值,增大喷嘴下入深度和含水率、同时降低节流前压力和温度,可提高节流后温度,有利于抑制水合物生成;且节流过程临界质量流量受喷嘴内径的影响最大,含水率和节流前压力次之,而节流前温度和喷嘴深度的影响最小,且增加含水率会提高临界质量流量,但产气量也随之下降;大宁–吉县区块现场工程实例分析表明,井下节流喷嘴内径由3.0 mm扩至5.0 mm和节流前压力由14 MPa增至18 MPa时,气水两相流体的临界质量流量提升幅度分别为179.3%和27.8%,而利用地层温度等将节流前温度由313 K升至333 K时,节流过程临界质量流量反而小幅下降且下降幅度仅为5.15%,为此,增大喷嘴内径及其下入深度和节流前压力同时降低节流前温度,有利于提高气水两相流体节流过程中临界质量流量,并提升高压含水气井的产气量。

有压管道内的泥沙冲淤特性

为明确复杂地形条件下有压管道内泥沙的运动特征与临界不淤流速,采用模型试验研究了不同粒径泥沙在不同运动状态下的水流流速,分析了泥沙粒径、加沙量与泥沙级配对临界不淤流速的影响。结果表明,间歇式运动状态下,粒径介于(0.075~0.600)mm的泥沙在管道上升段与水平段呈多个椭圆状运动,较陡的下降段呈带状分布,粒径介于(0.600~1.250)mm的泥沙在管道内呈山丘状运动;泥沙运动状态的临界水流速度随泥沙粒径的增大呈增加趋势,且连续式推移状态为最佳泥沙输送状态;临界不淤流速均随泥沙粒径、加沙量、泥沙级配的增大而增大,泥沙粒径是影响临界不淤流速的主要因素,加沙量与泥沙级配是影响临界不淤流速的次要因素。研究结果可为复杂地形条件下有压引水管道工程的设计和应用提供参考。

不同结构压力式比例混合器的流动特性研究

结合压力式比例混合器特点建立了3种不同结构的节流部件几何模型,采用Fluent软件对含有不同节流部件的比例混合器内部流场进行数值模拟计算,分析在设计工况下的压力分布和速度分布状态,并通过试验对3种不同结构比例混合器的混合比和压力损失进行了研究,分析不同压力式比例混合器结构特性对主要性能参数的影响。在模拟和试验结果对比验证中,在大流量下压力损失相对误差在±10%以内,为比例混合器设计计算、选型和结构优化提供了理论参考。

A modified predictive model for estimating gas flow rate in horizontal drain hole

Accurate prediction of the flow rate of horizontal gas well is necessary for economic feasibility,planning and development of gas field.Most of the early models assumed that the production from the horizontal well is infinitely conductive except few recent models.Some recent models reported in the literature for estimating flow rate in horizontal well where the pressure losses due to friction along horizontal drain hole was considered.An improved model that checks the impact of all possible well bore pressure losses on gas production rate of horizontal well is reported.The neglected impact of well bore pressure losses due to fluid accumulation and kinetic energy in the past models is thought to be a conceivable reason for the inconsistency between computed rates from the models and rates got from production tests.The new model was validated using the same field contextual investigation utilized by Guo et al.and outcome got from the new model yields more satisfactory results.A more realistic results that evident all flow phenomena in gas well include the initial unsteady,pseudo-steady and steady state flow condition hence flow rate at any given production time has been established for flow of gas along horizontal well.The outcomes of the study demonstrate that the percentage deviation of the new model at steady state flow condition is less than 5.0%compared with 11.05%acquired from Guo et al.model following by 259.7%from Furui's model,and 1118.2%got from Joshi's model.This work gives field operators a precise and helpful device for prediction and assessment of production in a gas horizontal well.

双壁管通风计算与风机选型

为了研究双壁管通风系统的流量与压强损失的关系,指导风机的选型,以某主机的双壁管通风系统的通风管路为研究对象,采用混合气体模型在293.15K下研究不同通气流量条件下的吹扫过程,对5种工况进行数值研究。结果表明:双壁管的通气流量与通风管路的压强损失呈非线性关系,随通气流量的增加而增加;通过函数拟合获得通气流量和双壁管通风管路的压强损失的具体公式,并对比4种工况下的数值计算结果和公式预测结果,双壁管通风管路压强损失的误差均小于2.0%,验证了公式的准确性,根据计算结果选择的风机有效地实现双壁管通风系统的经济性和安全性。研究成果对于工程应用具有一定的参考价值。

气井井筒携液临界流速和流量的动态分布研究

随着有水气田的开发,产水气井所占比例逐年增加,准确预测气井的携液临界流量和流速对于气井配产及积液判断有着重要的意义,除了寻找适合本气田的预测模型外,还要考虑最大携液临界流量在井筒中出现的位置。为此,通过对携液临界流量和携液临界流速沿井筒分布规律的研究,认为携液临界流量与沿井筒分布气井的产液量有关,其变化直接改变了井筒温度和压力分布。产液量较小时,井筒的温度损失较大,压力损失较小,温度变化对携液临界流量的分布起主导因素,而随着产液量的增加,温度损失逐渐减小,而压力损失逐渐增加,压力变化逐渐成为影响携液临界流量分布的主导因素;携液临界流量沿井筒分布曲线出现的拐点,就是压力变化起主导因素到温度变化起主导因素的转折点;产液量较大时,最大携液临界流量往往出现在井底。研究表明,在计算气井携液临界流量时要算出沿井筒每个位置的携液临界流量值,并以较大值作为气井的携液临界流量。

气井井筒温度、压力与积液综合预测模型

气井积液是产水气藏开发设计和气井生产管理面临的重要问题,但目前对气井流动机理与携液预测还存在争议.从气液两相流的基本流动机理出发,建立了考虑液滴变形和井斜影响下气井井筒的流型、温度、压力与携液综合预测模型,并用实际井数据对模型进行了验证.结果表明,所建模型可用于直井、斜井和水平井的产水气井井筒温度压力预测,预测误差小于5%;在环雾状流动情况下,井筒内液体以液滴和液膜的形式被完全带出井口,不会出现井筒积液;对常规垂直气井,利用井口数据便能判断气井积液情况,Turner 模型计算气井携液临界值较实际值偏大,李闽模型计算结果明显偏小,建议采用彭朝阳模型计算气井携液临界值;对斜井和水平井,则需要同时考虑液滴变形和井斜的影响,水平井近水平段携液临界流速和流量明显较垂直井段小,而造斜井段携液临界流速和临界流量随井斜角的增大先增大后减小,在井斜角为30°- 60°之间达到最大值,因此造斜井段是气井积液判断的重点部位.

临界携液流量与流速沿井筒分布规律研究

随着大牛地气田的不断开发,气井压力逐渐降低,气井积液越来越严重,准确预测气井的临界携液流量与流速对气井的配产以及积液判断有着重要的意义。除了寻找适合本气田的临界携液流量模型外,还要考虑最大携液流量在井筒中出现的位置。为此,文中通过建立气井临界携液流量模型与井筒压力、温度分布模型,以流压测试数据为基础,对临界携液流量与流速沿井筒的分布规律展开研究。结果表明:当压力梯度小于临界压力梯度时,临界携液流量随井深增加而减小,当压力梯度大于临界压力梯度时,临界携液流量随井深增加而增加;温度梯度为分别为1.5,2.0,2.5,3.0℃/100 m,临界压力梯度分别为0.04,0.05,0.06,0.07 MPa/100 m。

风压作用下的自然通风阻力特性的探讨

探讨了风压作用下大开口的自然通风阻力特性 ,并提出了用局部损失迭加法来计算阻力损失 ,即认为通过建筑物的气流是由不同的突缩段和突扩段的组合 .由此可推出进、出口的流量系数不同 ,从而得到一种简单的估算自然通风量的计算方法 .与试验值进行验证 ,相比通常的计算方法 ,此方法误差更小 .

高压细水雾灭火系统抑制地铁列车车厢火灾的有效性

目的研究地铁列车车厢火灾的特性参数,为高压细水雾灭火系统在地铁列车车厢中的实际应用提供理论依据.方法采用火灾动力学模拟软件FDS(Fire Dynam ic Simulator),以列车车厢为研究对象,模拟自然通风条件下,喷头间距分别为3.5 m和4.0 m,喷头流量为8 L/m in、11 L/m in、13 L/m in和15 L/m in的细水雾灭火效果.结果分析车厢火灾热释放速率、车厢内温度和CO2体积分数变化曲线,得出喷头间距3.5 m的临界流量为11 L/m in,喷头间距4.0m的临界流量为13 L/m in.结论细水雾喷头的流量对灭火有效性的影响显著,应使细水雾喷头的工作流量等于临界流量,以保证最少的用水量和最佳的灭火效果.

真空排污管网水力计算方法及设计程序

真空式排污管网的设计较复杂,各条管线的压力损失、设计流量及真空度等设计参数是不同的,基于其特点提出了真空排污管网水力计算方法,并通过计算程序设计了某真空排污管网工程。

低渗气藏单相气体渗流特征分析

目前对低渗气藏单相气体渗流规律已有初步认识,但在渗流特征方面大多仅限于定性描述,认为渗流曲线由低压力平方梯度下的上凸曲线段和较高压力梯度下的拟线性段组成,存在拟初始流速、临界压力平方梯度和临界渗流速度,未进行定量描述.利用苏里格低渗气田岩心,通过大量室内气体渗流实验,分析了渗透率对渗流曲线的影响,并得出了拟初始流速、临界压力平方梯度与岩心物性参数之间的函数关系.结果表明:拟初始流速与岩心系数呈线性关系,临界压力平方梯度与岩心系数呈负幂函数关系;最终给出分段描述低渗气藏单相气体渗流曲线的方程组.研究结果为更好认识低渗气藏渗流规律提供了理论依据.