The study presents an experimental exploration into the mode transition of an overunder TBCC(Turbine-Based Combined Cycle)inlet,with a specific emphasis on the flow characteristics at off-design transition Mach number...The study presents an experimental exploration into the mode transition of an overunder TBCC(Turbine-Based Combined Cycle)inlet,with a specific emphasis on the flow characteristics at off-design transition Mach number.A systematic investigation was undertaken into the mode transition characteristics in both unthrottled and throttled conditions within a highspeed duct,employing high speed Schlieren and dynamic pressure acquisition systems.The results show that the high-speed duct faced flow oscillations primarily dictated by the separation bubble near the duct entrance during the downward rotation of splitter,leading to the duct’s unstart under the unthrottled condition.During the splitter’s reverse rotation,a notable hysteresis of unstart/restart of the high-speed duct was observed.Conversely,hysteresis vanishes when the initial flowfield nears the critical state owing to downstream throttling.Moreover,the oscillatory diversity,a distinctive characteristic of the high-speed duct,was firstly observed during the mode transition induced by throttling.The flow evolution was divided into four stages:an initial instability stage characterized by low-frequency oscillations below 255 Hz induced by shock train self-excitation oscillation and high-frequency oscillations around 1367 Hz caused by the movement of separation bubble.This stage is succeeded by the“big buzz”phase,comprised of pressure accumulation/release within the overflow-free duct and shock motion outside the duct to retain dynamic flow balance.The dominant frequency escalated with the increase of the internal contraction ratio in the range of 280 Hz to 400 Hz.This was followed by a high-frequency oscillation stage around 453 Hz dominated by a large internal contraction ratio with low pulsating energy,accompanied by a continuous supersonic overflow.Lastly,as the splitter gradually intersected the boundary layer of the first-stage compression surface,the capture area and the turbulence intensity of the incoming flow underwent a sudden shift,leading to a more diverse flow oscillation within the duct,manifested as various forms of mixed buzz.展开更多
目的探讨耳内镜下锤骨柄反向部分脱袜后行I型鼓室成形术的临床效果,并介绍其手术特点。方法回顾性分析2022年3月—2023年9月在湘雅医院耳科行耳内镜下鼓室成形手术的患者32例(32耳)。患者根据手术方式分为两组,观察组16例(16耳)采用耳...目的探讨耳内镜下锤骨柄反向部分脱袜后行I型鼓室成形术的临床效果,并介绍其手术特点。方法回顾性分析2022年3月—2023年9月在湘雅医院耳科行耳内镜下鼓室成形手术的患者32例(32耳)。患者根据手术方式分为两组,观察组16例(16耳)采用耳内镜下蒂在前方的外耳道鼓膜瓣180°掀起、锤骨柄反向部分脱袜至近锤骨短突后行内-外植法鼓室成形术;对照组16例(16耳)采用耳内镜下常规蒂在前下的外耳道鼓膜瓣270°掀起、锤骨柄完全脱袜后行内-外植法鼓室成形术。比较两组患者手术时间、出血量、鼓膜愈合情况、术后听力改善情况及手术并发症。使用SPSS 26.0软件进行数据分析。结果观察组和对照组手术时间分别为(46.9±6.3)、(60.2±12.7)min,差异具有统计学意义(P<0.05);手术出血量分别为(1.9±1.0)、(4.1±1.6)mL,差异具有统计学意义(P<0.05)。术后6个月,两组患者鼓膜愈合率均为100%。观察组术前及术后气导听阈、气骨导差分别为(24.9±7.9)、(15.5±6.1)dB HL和(19.3±6.1)、(9.8±4.7)dB HL,平均提高9.5 dB HL,差异均具有统计学意义(P<0.05)。对照组术前及术后气导听阈、气骨导差分别为(28.6±7.1)、(18.9±6.8)dB HL和(22.9±6.1)、(13.2±5.2)dB HL,平均提高9.7 dB HL,差异均具有统计学意义(P均<0.05)。结论与耳内镜下常规蒂在前下的外耳道鼓膜瓣270°掀起、锤骨柄完全脱袜后行内-外植法鼓室成形术相比,耳内镜下蒂在前方的外耳道鼓膜瓣180°掀起、锤骨柄反向部分脱袜至近锤骨短突后行内-外植法鼓室成形术在手术成功率相同的情况下,具有手术时间短、出血少、创伤更小的优势。展开更多
This study aims to investigate the intricate dynamic characteristics of the high-speed duct during the over-under Turbine-Based Combined Cycle(TBCC)inlet mode transition process while operating in an off-design state ...This study aims to investigate the intricate dynamic characteristics of the high-speed duct during the over-under Turbine-Based Combined Cycle(TBCC)inlet mode transition process while operating in an off-design state under throttled conditions.A typical over-under TBCC inlet,designed for a working Mach number range of 0–6 with a transition Mach number of 3.5,is examined through experimental studies in a supersonic wind tunnel with a freestream Mach number of2.9.The investigation focuses on the complex oscillatory flow and unique hysteresis observed in the mode transition process of the high-speed duct under the mildly throttled condition,utilizing highspeed schlieren and dynamic pressure acquisition system.The findings reveal that the high-speed duct undergoes four distinct oscillation stages akin to those in a higher throttled state during the mode transition,albeit with smaller dominant frequency and energy.Moreover,an irregular alternating“big/little buzz”mode is observed in the early stage of the large oscillation stage.Notably,the mildly throttled state exhibits three intriguing hysteresis properties compared to the unthrottled and higher throttled states.Firstly,hysteresis is observed in the shock train motion stage in the duct before unstart,along with the corresponding inverse process.Subsequently,hysteresis is noted in the unstart and restart of the high-speed duct,with a smaller hysteresis interval than in the unthrottled state.Finally,the hysteresis characteristics of oscillation mode switching and the corresponding inverse process are explored.Based on the analysis,the first two hysteresis phenomena are associated with the formation and dissipation of the separation bubble.The significant adverse pressure gradient constrains the cross-sectional capacity of the channel,rendering the disappearance of the separation bubble more challenging.The hysteresis in oscillation mode switching is linked to not only the channel cross-sectional capacity but also the state of the incoming boundary layer.展开更多
基金funded by the National Natural Science Foundation of China(Nos.12025202,U20A2070 and 12172175)the National Science and Technology Major Project,China(No.J2019-Ⅱ-0014-0035)+2 种基金the Postdoctoral Fellowship Program of CPSF,China(No.GZB20230970)the Science Center for Gas Turbine Project,China(Nos.P2022-C-Ⅱ-002-001 and P2022-A-Ⅱ-002-001)the Young Scientific and Technological Talents Project of Jiangsu Association for Science and Technology,China(No.TJ-2021-052).
文摘The study presents an experimental exploration into the mode transition of an overunder TBCC(Turbine-Based Combined Cycle)inlet,with a specific emphasis on the flow characteristics at off-design transition Mach number.A systematic investigation was undertaken into the mode transition characteristics in both unthrottled and throttled conditions within a highspeed duct,employing high speed Schlieren and dynamic pressure acquisition systems.The results show that the high-speed duct faced flow oscillations primarily dictated by the separation bubble near the duct entrance during the downward rotation of splitter,leading to the duct’s unstart under the unthrottled condition.During the splitter’s reverse rotation,a notable hysteresis of unstart/restart of the high-speed duct was observed.Conversely,hysteresis vanishes when the initial flowfield nears the critical state owing to downstream throttling.Moreover,the oscillatory diversity,a distinctive characteristic of the high-speed duct,was firstly observed during the mode transition induced by throttling.The flow evolution was divided into four stages:an initial instability stage characterized by low-frequency oscillations below 255 Hz induced by shock train self-excitation oscillation and high-frequency oscillations around 1367 Hz caused by the movement of separation bubble.This stage is succeeded by the“big buzz”phase,comprised of pressure accumulation/release within the overflow-free duct and shock motion outside the duct to retain dynamic flow balance.The dominant frequency escalated with the increase of the internal contraction ratio in the range of 280 Hz to 400 Hz.This was followed by a high-frequency oscillation stage around 453 Hz dominated by a large internal contraction ratio with low pulsating energy,accompanied by a continuous supersonic overflow.Lastly,as the splitter gradually intersected the boundary layer of the first-stage compression surface,the capture area and the turbulence intensity of the incoming flow underwent a sudden shift,leading to a more diverse flow oscillation within the duct,manifested as various forms of mixed buzz.
文摘目的探讨耳内镜下锤骨柄反向部分脱袜后行I型鼓室成形术的临床效果,并介绍其手术特点。方法回顾性分析2022年3月—2023年9月在湘雅医院耳科行耳内镜下鼓室成形手术的患者32例(32耳)。患者根据手术方式分为两组,观察组16例(16耳)采用耳内镜下蒂在前方的外耳道鼓膜瓣180°掀起、锤骨柄反向部分脱袜至近锤骨短突后行内-外植法鼓室成形术;对照组16例(16耳)采用耳内镜下常规蒂在前下的外耳道鼓膜瓣270°掀起、锤骨柄完全脱袜后行内-外植法鼓室成形术。比较两组患者手术时间、出血量、鼓膜愈合情况、术后听力改善情况及手术并发症。使用SPSS 26.0软件进行数据分析。结果观察组和对照组手术时间分别为(46.9±6.3)、(60.2±12.7)min,差异具有统计学意义(P<0.05);手术出血量分别为(1.9±1.0)、(4.1±1.6)mL,差异具有统计学意义(P<0.05)。术后6个月,两组患者鼓膜愈合率均为100%。观察组术前及术后气导听阈、气骨导差分别为(24.9±7.9)、(15.5±6.1)dB HL和(19.3±6.1)、(9.8±4.7)dB HL,平均提高9.5 dB HL,差异均具有统计学意义(P<0.05)。对照组术前及术后气导听阈、气骨导差分别为(28.6±7.1)、(18.9±6.8)dB HL和(22.9±6.1)、(13.2±5.2)dB HL,平均提高9.7 dB HL,差异均具有统计学意义(P均<0.05)。结论与耳内镜下常规蒂在前下的外耳道鼓膜瓣270°掀起、锤骨柄完全脱袜后行内-外植法鼓室成形术相比,耳内镜下蒂在前方的外耳道鼓膜瓣180°掀起、锤骨柄反向部分脱袜至近锤骨短突后行内-外植法鼓室成形术在手术成功率相同的情况下,具有手术时间短、出血少、创伤更小的优势。
基金funded by the National Natural Science Foundation of China(Nos.12025202,U20A2070,12172175)the National Science and Technology Major Project,China(No.J2019-Ⅱ-0014-0035)+2 种基金the Postdoctoral Fellowship Program of CPSF,China(No.GZB20230970)the Science Center for Gas Turbine Project,China(Nos.P2022-C-II-002-001,P2022-A-II-002-001)the Young Scientific and Technological Talents Project of Jiangsu Association for Science and Technology,China(No.TJ-2021-052)。
文摘This study aims to investigate the intricate dynamic characteristics of the high-speed duct during the over-under Turbine-Based Combined Cycle(TBCC)inlet mode transition process while operating in an off-design state under throttled conditions.A typical over-under TBCC inlet,designed for a working Mach number range of 0–6 with a transition Mach number of 3.5,is examined through experimental studies in a supersonic wind tunnel with a freestream Mach number of2.9.The investigation focuses on the complex oscillatory flow and unique hysteresis observed in the mode transition process of the high-speed duct under the mildly throttled condition,utilizing highspeed schlieren and dynamic pressure acquisition system.The findings reveal that the high-speed duct undergoes four distinct oscillation stages akin to those in a higher throttled state during the mode transition,albeit with smaller dominant frequency and energy.Moreover,an irregular alternating“big/little buzz”mode is observed in the early stage of the large oscillation stage.Notably,the mildly throttled state exhibits three intriguing hysteresis properties compared to the unthrottled and higher throttled states.Firstly,hysteresis is observed in the shock train motion stage in the duct before unstart,along with the corresponding inverse process.Subsequently,hysteresis is noted in the unstart and restart of the high-speed duct,with a smaller hysteresis interval than in the unthrottled state.Finally,the hysteresis characteristics of oscillation mode switching and the corresponding inverse process are explored.Based on the analysis,the first two hysteresis phenomena are associated with the formation and dissipation of the separation bubble.The significant adverse pressure gradient constrains the cross-sectional capacity of the channel,rendering the disappearance of the separation bubble more challenging.The hysteresis in oscillation mode switching is linked to not only the channel cross-sectional capacity but also the state of the incoming boundary layer.
