34.
Turbo-propeller engines use a slightly higher viscosity oil due to the additional requirements of the reduction gear and propeller pitch change mechanism.
33．由于燃气涡轮发动机没有往复运动零件及重载荷齿轮，所以大多数发动机使用低粘度润滑油。这就减少了起动特别在低温条件下起动需要的功率。实际上，可以在温度低达-40℃的条件下正常起动，而无需对滑油预热。
34．涡轮螺桨发动机由于减速齿轮和螺旋浆变距机构的额外要求，使用粘度稍高的滑油。
“马姆巴”(Mamba)轴流式涡轮螺桨发动机是于1945年作为一台1000马力的发动机开始设计的。1946年4月首次运转，“马姆巴”发动机在肖特公司的“海鸥”(Short Seamew)飞机上投入使用，功率为1770当量马力。进一步发展为双“马姆巴”，由两台“马姆巴”组台在一个动力装置中发出3875当量马力。双“马姆巴”发动机装在“塘鹅”(Fairey Gannet)飞机上使用。
罗尔斯-罗伊斯公司RBl62-86发动机
Rolls-Royce RB162-86
阿姆斯特朗-西德利公司
“马姆巴”发动机
Armstrong Siddeley Mamba
The Mamba axial-flow turbo-prop was conceived in 1945 as a 1000 hp engine. First run in April 1946, the single Mamba eventually went into service with the Short Seamew at 1770 ehp. A further development was the Double Mamba, a combination of two single Mambas in one power unit. Providing up to 3875 ehp, the Double Mamba saw service with the Fairey Gannet.
9: Internal air system
第九章 内部空气系统
轴承载荷控制
飞机服务
封严
篦齿式封严件
环形封严件
液压封严件
石墨封严件
刷式封严件
热燃气吸入
涡轮冷却
轴承腔冷却
附件冷却
目录
绪言
冷却
Contents Page
Introduction 85 Cooling 86 Turbine cooling Bearing chamber cooling Accessory cooling Sealing 89 Labyrinth seals Ring seals Hydraulic seals Carbon seals Brush seals
Hot gas ingestion Control of bearing loads 91 Aircraft services 93
2.当空气逐级流过压气机时，对空气做的功在增加，从而提高了其压力和温度。因此，为了减少发动机的性能损失，空气应当按照每个特定的功能要求尽可能从压气机前几级抽取。冷却空气经由通风系统排出机外或在最高可能的压力下进入发动机的主燃气流，这时可以恢复一小部分性能。
INTRODUCTION
1. The engine internal air system is defined as those airflows which do not directly contribute to the engine thrust. The system has several important functions to perform for the safe and efficient operation of the engine. These functions include internal engine and accessory unit cooling, bearing chamber sealing prevention of hot gas ingestion into the turbine disc cavities, control of bearing axial loads, control of turbine blade tip clearances (Part 5) and engine anti-icing (Part 13). The system also supplies air for the aircraft services. Up to one fifth of the total engine core mass airflow may be used for these various functions.
2. An increasing amount of work is done on the air, as it progresses through the compressor, to raise its
冷却
3.在燃气涡轮发动机设计阶段的一项重要考虑是保证发动机的某些零件以及在有的情况下的某些附件吸收的热达不到危及其安全工作的程度。需要空气冷却的主要区域是燃烧室和涡轮。参见第4章燃烧室冷却技术。
pressure and temperature. Therefore, to reduce engine performance losses, the air is taken as early as possible from the compressor commensurate with the requirement of each particular function. The cooling air is expelled overboard via a vent system or into the engine main gas stream, at the highest possible pressure, where a small performance recovery is achieved.
COOLING
3. An important consideration at the design stage of a gas turbine engine is the need to ensure that certain parts of the engine, and in some instances certain accessories, do not absorb heat to the extent that is detrimental to their safe operation. The principal areas which require air cooling are the combustor and turbine. Refer to Part 4 for combustor cooling techniques.
Internal air system
4. Cooling air is used to control the temperature of the compressor shafts and discs by either cooling or heating them. This ensures an even temperature dis-tribution and therefore improves engine efficiency by controlling thermal growth and thus maintaining minimum blade tip and seal clearances. Typical cooling and sealing airflows are shown in fig. 9-1.
Turbine cooling
5. High thermal efficiency is dependent upon high turbine entry temperature, which is limited by the turbine blade and nozzle guide vane materials. Continuous cooling of these components allows their environmental operating temperature to exceed the material's melting point without affecting the blade and vane integrity. Heat conduction from the turbine blades to the turbine disc requires the discs to be cooled and thus prevent thermal fatigue and uncon-trolled expansion and contraction rates. 低压涡轮轴承
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