拉瓦爾的球形葉根
(帶鎖緊螺釘)
BMW公司空心葉片
(帶固定銷釘)
圖5-9 幾種葉片與渦輪盤連接的各種方法
壓氣機渦輪匹配
23．為了獲得發動機的最大效率及性能，渦輪的流量特性應當和壓氣機的流量特性非常仔細地匹配。例如，如果導向器葉片允許通過的最大流量太低，便會累積反壓，導致壓氣機喘振(第3章)。流最太高會導致壓氣機堵塞。無論在那一種情況下，效率的損失都會非常急劇地增加。
Fig. 5-9 Various methods of attaching blades to turbine discs.
材料
24．采用更高渦輪進口溫度所遇到的障礙常常是這些溫度對于導向器葉片和渦輪工作葉片的影響。向渦輪盤和工作葉片施加拉伸應力的高旋轉速度也是一個限制因素。
渦輪盤
26．渦輪盤必須在相對低的溫度環境下高速旋轉，并承受很大的旋轉應力。影響輪盤可用壽命的限制因素是其抗疲勞裂紋的能力。
導向器葉片
25．由于處于靜止狀態，導向器葉片不像渦輪工作葉片那樣承受旋轉應力。因此，耐熱是其最主要的性能要求。雖然需要采用冷卻來防止熔化，但仍使用了鎳臺金。陶瓷涂層能夠加強熱阻特性，在相同的工作條件下，可減少需要的冷卻空氣量，從而改善發動機效率。
圖5-10 對轉的自由動力渦輪
Fig. 5-10 Free power contra-rotating turbine.
旋轉機匣
鑄造的葉片環
擴散粘接
粉末冶金輪盤
圖5-11 一種雙合金渦輪盤的截面圖
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．在過去，渦輪盤是用鐵和奧氏體鋼制造的，而近年來則用鎳基合金制造。增加合金中鎳元素的含量可通過增大抗疲勞特性而延長輪盤的壽命。另一個途徑是采用昂貴的粉末冶金盤，它可提高強度10％，允許達到更高的轉速。
普通鑄造渦輪葉片
圖5-12 各種渦輪工作葉片的晶粒結構
Fig. 5-11 Section through a dual alloy disc.
單晶體渦輪葉片
定向凝固渦輪葉片（D.S.葉片）
圓柱形
晶體結構
在縱軸方向有
改進的機械特性
等軸晶體結構
縱軸方向具有優越的
機械特性并改善了耐熱性
在各方向機械特性良好
渦輪工作葉片
28．簡要敘述關于渦輪工作葉片設計要考慮的某些問題會得到關于正確選用葉片材料重要性的概念。工作葉片盡管已達到紅熱狀態，仍應具備足夠的強度來承受高速旋轉產生的離心載荷。一片小小的渦輪工作葉片重量僅2盎司，在最高轉速下的載荷會超過2噸，它還要承受燃氣施加的很高的彎曲載荷，以產生驅動壓氣機所必須的數千馬力的渦輪功率。渦輪工作葉片還應當耐疲勞和熱沖擊，保證在燃氣高頻脈動影響下不致損壞。工作葉片還要能耐腐蝕和耐氧化。除了所有這些要求之外，工作葉片應當采用可以精確成形和利用現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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