To investigate the effects of various random factors on the preventive maintenance （PM） decision-making of one type of two-unit series system, an optimal quasi-periodic PM policy is introduced. Assume that PM is per...To investigate the effects of various random factors on the preventive maintenance （PM） decision-making of one type of two-unit series system, an optimal quasi-periodic PM policy is introduced. Assume that PM is perfect for unit 1 and only mechanical service for unit 2 in the model. PM activity is randomly performed according to a dynamic PM plan distributed in each implementation period. A replacement is determined based on the competing results of unplanned and planned replacements. The unplanned replacement is trigged by a catastrophic failure of unit 2, and the planned replacement is executed when the PM number reaches the threshold N. Through modeling and analysis, a solution algorithm for an optimal implementation period and the PM number is given, and optimal process and parametric sensitivity are provided by a numerical example. Results show that the implementation period should be decreased as soon as possible under the condition of meeting the needs of practice, which can increase mean operating time and decrease the long-run cost rate.展开更多
Maintenance optimization of periodic replacement for mono-unit production system is a widely discussed topic.In practice,the replacement for a parallel production system with multi-unit served by one repairman is univ...Maintenance optimization of periodic replacement for mono-unit production system is a widely discussed topic.In practice,the replacement for a parallel production system with multi-unit served by one repairman is universal.The replacement action is often implemented in a maintenance window at random,although the replacement period appears as a quasi-periodic event.To optimize these maintenance policies,this study analyzes a bivariate quasi-periodic replacement policy (T,W) for a two-unit parallel production system with a maintenance window and one repairman.One unit of the system is replaced when either a failure occurs or a replacement plan comes in the maintenance window,whichever comes first.If one of the two units is in the replacement,the other may continue operating or waiting until the replacement is completed.An optimal replacement window [T*,T* + W*] can be obtained by jointly considering the system's long-running cost rate and the availability using the genetic algorithm.This study also introduces three examples of the production system with different types of units to illustrate the proposed policy.展开更多
以工业规模喷淋塔内醇胺溶液吸收CO_(2)为研究对象,基于欧拉-拉格朗日方法建立了烟气-液滴气液两相流动、相间传热传质和液相化学反应耦合的计算流体力学(CFD)模型。通过与乙醇胺(MEA)溶液吸收CO_(2)实验数据对比验证了CFD模型可靠性,...以工业规模喷淋塔内醇胺溶液吸收CO_(2)为研究对象,基于欧拉-拉格朗日方法建立了烟气-液滴气液两相流动、相间传热传质和液相化学反应耦合的计算流体力学(CFD)模型。通过与乙醇胺(MEA)溶液吸收CO_(2)实验数据对比验证了CFD模型可靠性,在此基础上分析了CO_(2)吸收过程所伴随热质交换和化学反应的基本规律,以及吸收剂化学组成、气液两相流动特性和操作压力对喷淋塔内CO_(2)脱除效率的影响。模拟结果表明:随塔体高度增加烟气中CO_(2)体积分数下降,而烟温和水蒸气体积分数均呈先上升后下降趋势;当贫液中CO_(2)负荷由0.1增至0.4,塔内烟温最大值由70℃降至54℃,贫液负荷大于0.25时喷淋塔脱碳效率显著下降;表观气速大于2.5m/s时烟气停留时间显著缩短且液相侧传质系数减小,传质比表面积的增加对CO_(2)吸收效率提升作用减弱;喷淋塔操作压力由101 k Pa降至70 k Pa,CO_(2)脱除效率降低约15.9百分点。展开更多
基于超声波时差测量流量的方法具有非接触、易安装、不改变流体的运动状态等优点,被广泛应用于油田井下流体流速测量分析领域,能够实时测量流体流速,准确分析管道中流体流量的变化。针对传统的超声波流量计功耗高、电路复杂的缺点,根据...基于超声波时差测量流量的方法具有非接触、易安装、不改变流体的运动状态等优点,被广泛应用于油田井下流体流速测量分析领域,能够实时测量流体流速,准确分析管道中流体流量的变化。针对传统的超声波流量计功耗高、电路复杂的缺点,根据超声波时差法测量流量的原理,结合井下高温测量环境,以及未来测井仪器低功耗、小型化的需求,以dsPIC33EV为主控芯片,设计了一种低功耗、小型化的井下超声波流量测量系统。该系统利用dsPIC33EV的充电时间测量单元CTMU(Charging Time Measurement Unit),实现声波传播时差与流量的高精度测量与计算。室内实验平台测试数据表明,该文设计的井下超声波流量测量系统测量相对误差为±7.2%,典型功耗为20mW,技术指标满足生产井流量监测需求。展开更多
基金The National Natural Science Foundation of China(No.51275090,71201025)the Program for Special Talent in Six Fields of Jiangsu Province(No.2008144)+1 种基金the Scientific Research Foundation of Graduate School of Southeast University(No.YBJJ1302)the Scientific Innovation Research of College Graduates in Jiangsu Province(No.CXLX12_0078)
文摘To investigate the effects of various random factors on the preventive maintenance （PM） decision-making of one type of two-unit series system, an optimal quasi-periodic PM policy is introduced. Assume that PM is perfect for unit 1 and only mechanical service for unit 2 in the model. PM activity is randomly performed according to a dynamic PM plan distributed in each implementation period. A replacement is determined based on the competing results of unplanned and planned replacements. The unplanned replacement is trigged by a catastrophic failure of unit 2, and the planned replacement is executed when the PM number reaches the threshold N. Through modeling and analysis, a solution algorithm for an optimal implementation period and the PM number is given, and optimal process and parametric sensitivity are provided by a numerical example. Results show that the implementation period should be decreased as soon as possible under the condition of meeting the needs of practice, which can increase mean operating time and decrease the long-run cost rate.
基金the National Natural Science Foundation of China(No.71561016)the China Postdoctoral Science Foundation(Nos.2017M613297XB , 2019T120964)。
文摘Maintenance optimization of periodic replacement for mono-unit production system is a widely discussed topic.In practice,the replacement for a parallel production system with multi-unit served by one repairman is universal.The replacement action is often implemented in a maintenance window at random,although the replacement period appears as a quasi-periodic event.To optimize these maintenance policies,this study analyzes a bivariate quasi-periodic replacement policy (T,W) for a two-unit parallel production system with a maintenance window and one repairman.One unit of the system is replaced when either a failure occurs or a replacement plan comes in the maintenance window,whichever comes first.If one of the two units is in the replacement,the other may continue operating or waiting until the replacement is completed.An optimal replacement window [T*,T* + W*] can be obtained by jointly considering the system's long-running cost rate and the availability using the genetic algorithm.This study also introduces three examples of the production system with different types of units to illustrate the proposed policy.
文摘以工业规模喷淋塔内醇胺溶液吸收CO_(2)为研究对象,基于欧拉-拉格朗日方法建立了烟气-液滴气液两相流动、相间传热传质和液相化学反应耦合的计算流体力学(CFD)模型。通过与乙醇胺(MEA)溶液吸收CO_(2)实验数据对比验证了CFD模型可靠性,在此基础上分析了CO_(2)吸收过程所伴随热质交换和化学反应的基本规律,以及吸收剂化学组成、气液两相流动特性和操作压力对喷淋塔内CO_(2)脱除效率的影响。模拟结果表明:随塔体高度增加烟气中CO_(2)体积分数下降,而烟温和水蒸气体积分数均呈先上升后下降趋势;当贫液中CO_(2)负荷由0.1增至0.4,塔内烟温最大值由70℃降至54℃,贫液负荷大于0.25时喷淋塔脱碳效率显著下降;表观气速大于2.5m/s时烟气停留时间显著缩短且液相侧传质系数减小,传质比表面积的增加对CO_(2)吸收效率提升作用减弱;喷淋塔操作压力由101 k Pa降至70 k Pa,CO_(2)脱除效率降低约15.9百分点。
文摘基于超声波时差测量流量的方法具有非接触、易安装、不改变流体的运动状态等优点,被广泛应用于油田井下流体流速测量分析领域,能够实时测量流体流速,准确分析管道中流体流量的变化。针对传统的超声波流量计功耗高、电路复杂的缺点,根据超声波时差法测量流量的原理,结合井下高温测量环境,以及未来测井仪器低功耗、小型化的需求,以dsPIC33EV为主控芯片,设计了一种低功耗、小型化的井下超声波流量测量系统。该系统利用dsPIC33EV的充电时间测量单元CTMU(Charging Time Measurement Unit),实现声波传播时差与流量的高精度测量与计算。室内实验平台测试数据表明,该文设计的井下超声波流量测量系统测量相对误差为±7.2%,典型功耗为20mW,技术指标满足生产井流量监测需求。
