当燃气温升已越过高温合金熔点时,涡轮叶片前缘的气膜冷却孔怎样继续保护叶身?
How do film-cooling holes on a turbine blade leading edge keep protecting the airfoil once gas temperature exceeds the alloy melting point?
压气机引气经叶身内部蛇形通道流向倾斜小孔,出流以合适动量比贴附在叶片外表面形成连续低温气膜,将高温燃气与金属壁面隔开,孔内对流又额外带走热量。吹风比过大会使射流脱离壁面反而强化局部换热,故孔的位置、角度与吹风比须同热障涂层一起协同优化,才能支撑持续提高的涡轮前温度。
Compressor bleed air travels through internal serpentine passages into small inclined holes, and the exiting jets attach to the outer surface at a suitable momentum ratio to form a continuous cool film separating hot gas from the metal, while convection inside the holes removes additional heat. An excessive blowing ratio lifts the jet off the wall and worsens local heat transfer, so hole position, angle and blowing ratio are optimized jointly with the thermal barrier coating to support ever-higher turbine inlet temperatures.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
J.-C. Han 等《Gas Turbine Heat Transfer and Cooling Technology》(CRC出版社,第2版)气膜冷却章节
J.-C. Han, S. Dutta & S. V. Ekkad, Gas Turbine Heat Transfer and Cooling Technology, 2nd ed., CRC Press, film-cooling chapters
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780429107115 (2012)
#气膜冷却 #涡轮前温度
为什么现代大涵道比涡扇发动机在高亚声速巡航时比小涵道比发动机更省油?
Why do modern high-bypass turbofans burn less fuel than low-bypass ones during high-subsonic cruise?
巡航推力取决于发动机质量流量与排气速度增量的乘积,涵道比增大后更多空气只经风扇适度增压加速,排气动能损失减小,推进效率随之提高。核心机维持高总压比与高涡轮前温度以保证热效率,二者叠加使单位燃油消耗率显著下降。代价是短舱直径和迎风面积增大,故涵道比的提升受全机阻力与安装空间制约。
Cruise thrust scales with mass flow times velocity increment, so routing most of the airflow through the fan with only modest acceleration cuts the kinetic energy wasted in the exhaust and raises propulsive efficiency. The core keeps a high overall pressure ratio and high turbine inlet temperature to preserve thermal efficiency, and the combination markedly lowers thrust-specific fuel consumption. The price is larger nacelle diameter and frontal area, which limits how far bypass ratio can be pushed.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：作者 / 书名 / 版次 / 出版社 / 年份齐备，仅缺独立比对证据；已在可信度报告单列披露，不再重复核验。
Nick Cumpsty著《Turbojets: The Development of the Turbojet and its Application in Aircraft》第2版,剑桥大学出版社,2013
Nick Cumpsty, Turbojets: The Development of the Turbojet and its Application in Aircraft, 2nd ed., Cambridge University Press, 2013
#涵道比 #推进效率
民用涡扇发动机的涵道比为什么一代接一代不断增大？继续增大的瓶颈在哪里？
Why has the bypass ratio of civil turbofan engines climbed generation after generation, and what bottlenecks limit further growth?
亚音速巡航时推进效率随平均排气速度降低而升高，大涵道比让更多空气仅经风扇适度增压后低速排出，以更小的速度增量获得同等推力，单位燃油消耗率随之下降。代价是短舱直径、重量和阻力一起上涨，风扇转速也受叶尖速度约束，所以齿轮传动风扇和开放式转子成为突破这些约束的主要路线。
In subsonic cruise propulsive efficiency rises as mean exhaust velocity falls, so a large bypass accelerates more air only moderately through the fan, buying equal thrust with a smaller velocity increment and burning less fuel per seat-mile. The price is fan-cowl diameter, weight and drag growing together, with fan speed capped by tip velocity, which is why geared fans and open rotors mark the main routes past these limits.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
廉筱纯、吴虎《航空发动机原理》，西北工业大学出版社，循环分析与效率章节
J. D. Mattingly, Elements of Gas Turbine Propulsion, McGraw-Hill, cycle analysis chapters on bypass ratio
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#涵道比 #推进效率