Computational fluid dynamics( CFD) is used to investigate a new type of two-chamber natural gas distributor,which has a natural gas inlet and nine nozzle outlets. The uniformity at the outlet of distributor is practic...Computational fluid dynamics( CFD) is used to investigate a new type of two-chamber natural gas distributor,which has a natural gas inlet and nine nozzle outlets. The uniformity at the outlet of distributor is practice proven to have significant degree influence on its comprehensive performance. To improve the uniformity at the nozzles of the gas distributor,CFD modeling with the RNG k-ε turbulence model is undertaken to understand the mass flow rate of nozzles with reference to different length of chambers and the most optimal length is obtained. The internal flow pattern of the natural gas distributor is analyzed. It is found that the local maximum deviation of the nozzle outflow rate increases with the increase of chambers length when the length is more than 64 mm. The results provide useful suggestions for the optimal design of two-chamber natural gas distributor.展开更多
BACKGROUND Single atrium with single ventricle,or a two-chambered heart,is an extremely rare congenital malformation.Few cases with two-chambered heart surviving to adulthood have been reported.CASE SUMMARY We reporte...BACKGROUND Single atrium with single ventricle,or a two-chambered heart,is an extremely rare congenital malformation.Few cases with two-chambered heart surviving to adulthood have been reported.CASE SUMMARY We reported an adult female patient with a two-chambered heart and situs inversus totalis accompanied by multiple pregnancies and abortions.Magnetic resonance imaging detected a two-chambered heart.B-ultrasound-guided uterine aspiration was performed to absorb 8 g and 10 g of organized villus and decidual tissues,respectively,with a small amount of bleeding.Postoperatively,cyanosis and fatigue-induced shortness of breath were gradually relieved.The patient has currently outlived all similar cases reported so far.CONCLUSION Hemodynamic changes in pregnant women with two-chambered heart impaired cardiac function,responsible for hypoperfusion and miscarriage.展开更多
基金Sponsored by the Beijing Key Lab of Heating,Gas Supply,Ventilating and Air Conditioning Engineering(Grant No.NR2013K04)the Higher School Science and Technology Development Fund of Tianjin(Grant No.20130909)
文摘Computational fluid dynamics( CFD) is used to investigate a new type of two-chamber natural gas distributor,which has a natural gas inlet and nine nozzle outlets. The uniformity at the outlet of distributor is practice proven to have significant degree influence on its comprehensive performance. To improve the uniformity at the nozzles of the gas distributor,CFD modeling with the RNG k-ε turbulence model is undertaken to understand the mass flow rate of nozzles with reference to different length of chambers and the most optimal length is obtained. The internal flow pattern of the natural gas distributor is analyzed. It is found that the local maximum deviation of the nozzle outflow rate increases with the increase of chambers length when the length is more than 64 mm. The results provide useful suggestions for the optimal design of two-chamber natural gas distributor.
基金Supported by Chinese Ministry of Education(No.2020-39)Zunyi Science and Technology Project,No.Zunshi Kehe HZ(2020)246.
文摘BACKGROUND Single atrium with single ventricle,or a two-chambered heart,is an extremely rare congenital malformation.Few cases with two-chambered heart surviving to adulthood have been reported.CASE SUMMARY We reported an adult female patient with a two-chambered heart and situs inversus totalis accompanied by multiple pregnancies and abortions.Magnetic resonance imaging detected a two-chambered heart.B-ultrasound-guided uterine aspiration was performed to absorb 8 g and 10 g of organized villus and decidual tissues,respectively,with a small amount of bleeding.Postoperatively,cyanosis and fatigue-induced shortness of breath were gradually relieved.The patient has currently outlived all similar cases reported so far.CONCLUSION Hemodynamic changes in pregnant women with two-chambered heart impaired cardiac function,responsible for hypoperfusion and miscarriage.
文摘直流分压器是直流输电系统中不可缺少的主设备。目前直流阻容式分压器因结构和工作原理的原因,导致内部出现较大的温度梯度,影响了分压器的误差性能,同时增加了空心绝缘子发生污秽闪络的概率。针对±1 100 kV直流分压器的散热问题,文中进行了内部温度场的结构优化设计,同时在顶部增加散热结构,降低其温度梯度。最后利用Ansys Fluent软件对该结构设计进行温度场和热流场的仿真分析,结果表明:在27℃的环境温度下,与传统结构的直流分压器相比,在额定一次电流为2 m A,热流量为2.2 k W的情况下,其内部温度有明显的降低,最大温差可达到20 K。同时增加的散热翅片显著提高了分压器内部气体的循环流动,提高了散热的效率,优化后的结构满足散热的需求。
