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边界层抽吸和脉动反压作用下隔离段内流动特性研究 被引量:5
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作者 李季 罗佳茂 杨顺华 《推进技术》 EI CAS CSCD 北大核心 2019年第8期1759-1766,共8页
为了解上游边界层抽吸控制和下游周期脉动反压作用下隔离段内流动特性,采用非定常数值模拟和理论分析相结合的方法,对来流Ma=2情况下的隔离段内激波串动态演化特性、激波串形态结构变化以及激波串演化迟滞现象进行了研究。结果表明,在... 为了解上游边界层抽吸控制和下游周期脉动反压作用下隔离段内流动特性,采用非定常数值模拟和理论分析相结合的方法,对来流Ma=2情况下的隔离段内激波串动态演化特性、激波串形态结构变化以及激波串演化迟滞现象进行了研究。结果表明,在脉动反压和边界层抽吸作用下,激波串在上游抽吸狭缝与下游隔离段出口之间周期振荡,振荡频率与脉动反压一致。在振荡过程中,首道激波串形态在规则反射与马赫反射以及马赫反射与弧形激波(包含正激波)之间相互转换。边界层抽吸将激波串固定在抽吸狭缝位置,有效提高了隔离段抗反压性能,脉动频率越大,可承受的瞬态反压峰值越大。在一个振荡周期内,激波串向上移动速度较向下移动更快,且在上下移动过程中形态变化存在迟滞现象。 展开更多
关键词 边界层抽吸 激波串 迟滞现象 隔离段
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隔离段内正激波串受迫振荡特性研究 被引量:9
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作者 熊冰 王振国 +1 位作者 范晓樯 李腾骥 《推进技术》 EI CAS CSCD 北大核心 2017年第1期1-7,共7页
为了解隔离段在真实燃烧室反压作用下的工作特性,通过数值方法模拟燃烧室振荡燃烧引起的脉动反压,在来流Mai=2条件下,探讨了脉动反压引起的激波串受迫振荡特性。结果表明,在反压脉动条件下,激波串前缘位置周期振荡,其振荡频率与反压脉... 为了解隔离段在真实燃烧室反压作用下的工作特性,通过数值方法模拟燃烧室振荡燃烧引起的脉动反压,在来流Mai=2条件下,探讨了脉动反压引起的激波串受迫振荡特性。结果表明,在反压脉动条件下,激波串前缘位置周期振荡,其振荡频率与反压脉动频率一致,振幅与反压脉动频率负相关,反压脉动频率600Hz时,振幅仅为管道长2.97%;就抗反压能力而言,在反压脉动条件下,隔离段能承受比定常状态更大的反压峰值,且脉动频率越大,可承受瞬态反压峰值越大。激波串的受迫振荡包含两种形式:激波串整体位置的前后运动和激波节之间的相对运动。在一定程度内,反压脉动频率较低时(50Hz,100Hz),激波串整体位置的前后运动是主要的受迫振荡形式,激波节之间的相对运动很弱;随反压脉动频率升高(300Hz,600Hz),激波节之间的相对运动加剧,逐渐成为激波串受迫振荡的主要形式。另外,在激波串振荡过程中,激波串往上下游运动经过同一位置时,激波串形态会出现迟滞,这是导致总压恢复系数迟滞的原因。 展开更多
关键词 反压脉动 正激波串 受迫振荡 隔离段
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Clinical study of midazolam sequential with dexmedetomidine for agitated patients undergoing weaning to implement light sedation in intensive care unit 被引量:21
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作者 Xing Lu Jun Li +4 位作者 Tong Li Jie Zhang Zhi-Bo Li Xin-Jing Gao Lei Xu 《Chinese Journal of Traumatology》 CAS CSCD 2016年第2期94-96,共3页
Purpose: To evaluate midazolam sequential with dexmedetomidine for agitated patients undergoing weaning to implement light sedation in ICU. Methods: This randomized, prospective study was conducted in Tianjin Third ... Purpose: To evaluate midazolam sequential with dexmedetomidine for agitated patients undergoing weaning to implement light sedation in ICU. Methods: This randomized, prospective study was conducted in Tianjin Third Central Hospital, China. Using a sealed-envelope method, the patients were randomly divided into 2 groups (40 patients per group). Each patient of group A received an initial loading dose of midazolam at 0.3 3 mg/kg-h 24 h before extubation, followed by an infusion of dexmedetomidine at a rate of 0.2-1 μg/kg-h until extubation. Each patient of group B received midazolam at a dose of 0.3 3 mg/kg.h until extubation. The dose of sedation was regulated according to PASS sedative scores maintaining in the range of-2-1. All patients were continuously monitored for 60 min after extubation. During the course, heart rate (HR), mean artery pressure (MAP), extubation time, adverse reactions, ICU stay, and hospital stay were observed and recorded continuously at the following time points: 24 h before extubation (T1), 12 h before extubation (T2), extubation (T3), 30 rain after extubation (T4), 60 min after extubation (TS). Results: Both groups reached the goal of sedation needed for ICU patients. Dexmedetomidine was associated with a significant increase in extubation quality compared with midazolam, reflected in the prevalence of delirium after extubation (20% (8/40) vs 45% (18140)), respectively (p=0.017). There were no clinically significant decreases in HR and MAP after infusing dexmedetomidine or midazolam. In the group A, HR was not significantly increased after extubation; however, in the group B, HR was significantly increased compared with the preextubation values (p 〈 0.05). HR was significantly higher in the group B compared with the group A at 30 and 60 min after extubation (both, p 〈 0.05). Compared with preextubation values, MAP was significantly increased at extubation in the group B (p 〈 0.05) and MAP was significantly higher at T3, T4, T5 in the group B than group A (p 〈 0.05). There was a significant difference in extubation time ((3.0± 1.5) d vs (4.3 ± 2.2) d, p 〈 0.05), ICU stay ((5.4 ± 2.1 ) d vs (8.0± 1.4) d, p 〈 0.05), hospital stay ((10.1 ± 3.0) d vs (15.3 ± 2.6) d, p 〈 0.05) between group A and B. Conclusion: Midazolam sequential with dexmedetomidine can reach the goal of sedation for ICU agitated patients, meanwhile it can maintain the respiratory and circulation parameters and reduce adverse reactions. 展开更多
关键词 DexmedetomidineMidazolamLight sedationMechanical ventilation
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