拉瓦尔的球形叶根
(带锁紧螺钉)
BMW公司空心叶片
(带固定銷钉)
图5-9 几种叶片与涡轮盘连接的各种方法
压气机涡轮匹配
23．为了获得发动机的最大效率及性能，涡轮的流量特性应当和压气机的流量特性非常仔细地匹配。例如，如果导向器叶片允许通过的最大流量太低，便会累积反压，导致压气机喘振(第3章)。流最太高会导致压气机堵塞。无论在那一种情况下，效率的损失都会非常急剧地增加。
Fig. 5-9 Various methods of attaching blades to turbine discs.
材料
24．采用更高涡轮进口温度所遇到的障碍常常是这些温度对于导向器叶片和涡轮工作叶片的影响。向涡轮盘和工作叶片施加拉伸应力的高旋转速度也是一个限制因素。
涡轮盘
26．涡轮盘必须在相对低的温度环境下高速旋转，并承受很大的旋转应力。影响轮盘可用寿命的限制因素是其抗疲劳裂纹的能力。
导向器叶片
25．由于处于静止状态，导向器叶片不像涡轮工作叶片那样承受旋转应力。因此，耐热是其最主要的性能要求。虽然需要采用冷却来防止熔化，但仍使用了镍台金。陶瓷涂层能够加强热阻特性，在相同的工作条件下，可减少需要的冷却空气量，从而改善发动机效率。
图5-10 对转的自由动力涡轮
Fig. 5-10 Free power contra-rotating turbine.
旋转机匣
铸造的叶片环
扩散粘接
粉末冶金轮盘
图5-11 一种双合金涡轮盘的截面图
Fig. 5-11 Section through a dual alloy disc.
Nozzle guide vanes
25. Due to their static condition. the nozzle guide vanes do not endure the same rotational stresses as the turbine blades. Therefore, heat resistance is the property most required. Nickel alloys are used, although cooling is required to prevent melting. Ceramic coatings can enhance the heat resisting properties and, for the same set of conditions, reduce the amount of cooling air required, thus improving engine efficiency.
Turbine discs
26. A turbine disc has to rotate at high speed in a relatively cool environment and is subjected to large rotational stresses. The limiting factor which affects the useful disc life is its resistance to fatigue cracking.
27．在过去，涡轮盘是用铁和奥氏体钢制造的，而近年来则用镍基合金制造。增加合金中镍元素的含量可通过增大抗疲劳特性而延长轮盘的寿命。另一个途径是采用昂贵的粉末冶金盘，它可提高强度10％，允许达到更高的转速。
普通铸造涡轮叶片
图5-12 各种涡轮工作叶片的晶粒结构
Fig. 5-11 Section through a dual alloy disc.
单晶体涡轮叶片
定向凝固涡轮叶片（D.S.叶片）
圆柱形
晶体结构
在纵轴方向有
改进的机械特性
等轴晶体结构
纵轴方向具有优越的
机械特性并改善了耐热性
在各方向机械特性良好
涡轮工作叶片
28．简要叙述关于涡轮工作叶片设计要考虑的某些问题会得到关于正确选用叶片材料重要性的概念。工作叶片尽管已达到红热状态，仍应具备足够的强度来承受高速旋转产生的离心载荷。一片小小的涡轮工作叶片重量仅2盎司，在最高转速下的载荷会超过2吨，它还要承受燃气施加的很高的弯曲载荷，以产生驱动压气机所必须的数千马力的涡轮功率。涡轮工作叶片还应当耐疲劳和热冲击，保证在燃气高频脉动影响下不致损坏。工作叶片还要能耐腐蚀和耐氧化。除了所有这些要求之外，工作叶片应当采用可以精确成形和利用现有制造方法加工的材料制造。
27. In the past, turbine discs have been made in ferritic and austenitic steels but nickel based alloys are currently used. Increasing the alloying elements in nickel extend the life limits of a disc by increasing fatigue resistance. Alternatively, expensive powder metallurgy discs, which offer an additional 10% in strength, allow faster rotational speeds to be achieved.
Turbine blades
28.
A brief mention of some of the points to be considered in connection with turbine blade design will give an idea of the importance of the correct choice of blade material. The blades, while glowing red-hot, must be strong enough to carry the centrifugal loads due to rotation at high speed. A small turbine blade weighing only two ounces may exert a load of over two tons at top speed and it must withstand the high bending loads applied by the gas to produce the many thousands of turbine horse-power necessary to drive the compressor. Turbine blades must also be resistant to fatigue and thermal shock, so that they will not fail under the influence of high frequency fluctuations in the gas conditions, and they must also be resistant to corrosion and oxidization. In spite of all these demands, the blades must be made in a material that can be accurately formed and machined by current manufacturing methods.
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