46．發動機設計的主要考慮因索，尤其是對于民用運輸機來說，是低的耗油率和重量。由于采用了內外涵道原理，借助于先進的機械和氣動特性并使用了更好的材料，使發動機設計得到相當大的改進。隨著向更高涵道比即15：1的范圍發展的趨勢，三轉子和對轉的后風扇發動機可達到這種壓力比和涵道比。它們的轉子短而壓氣機級數少，從而得到一種更輕和結構更加緊湊的發動機。
Performance
從這一點至65，617英尺音速不變
從這一點至65，617英尺大氣溫度不變
圖21-10 國際標準大氣
Fig. 21-10 International Standard Atmosphere.
by-pass ratio engine, the weight reduction compared with a pure jet engine is in the order of 20 per cent for the same air mass flow.
49. With a high by-pass ratio engine of the triple-spool configuration, a further significant improvement in specific weight is obtained- This is derived mainly from advanced mechanical and aerodynamic design, which in addition to permitting a significant reduction in the total number of parts, enables rotating assemblies to be more effectively matched and to work closer to optimum conditions, thus minimizing the number of compressor and turbine stages for a 47．耗油率與熱效率和推進效率有直接關系，也就是與發動機的總效率有關。從理論上來說，高的熱效率需要高的壓力，這實際上還意味著高的渦輪進口溫度。在純渦輪噴氣發動機中，這種高溫度將導致高的噴氣速度，因而會降低推進效率(第40段)。然而，正如第43段談到的，利用內外涵道原理，將一定比例的低壓壓氣機或風扇出口空氣從旁路排出。以降低平均噴氣溫度和速度，可以有效地同時達到高的熱效率和推進效率。隨著高涵道比和總增壓比的先進技術發動機的問世，耗油率又得到進一步明顯的改進。
48．純噴氣發動機的渦輪比較重，因為它們要處理所有氣流，而內外涵發動機的渦輪只處理一部分氣流；因而高壓壓氣機、燃燒室和渦輪可以縮小尺寸。增大流過渦輪的每磅空氣的功率以充分利用它們的能力，可采用提高增壓比和渦輪進口溫度的方法來實現。顯然，內外涵發動機比較輕，因為不僅減小了高壓轉動組件的直徑，而且對一定的功率輸出而言。發動機比較短。對一種低涵道比發動機來說，在空氣質量流量相同時，與純噴氣發動機相比，重量減輕的數量級達20％。
Performance
given duty. The use of higher strength light-weight materials is also a contributory factor.
50. For a given mass flow less thrust is produced by the by-pass engine due to the lower exit velocity. Thus, to obtain the same thrust, the by-pass engine must be scaled to pass a larger total mass airflow than the pure turbo-jet engine. The weight of the engine, however, is still less because of the reduced size of the H.P. section of the engine. Therefore, in addition to the reduced specific fuel consumption, an improvement in the power-to-weight ratio is obtained. 49．對三轉子布局的高涵道比發動機來說，單位重量又獲得很大改進。這主要得益于先進的機械和氣動設計，它除了允許大大減少零件的總數外，還使轉動組件能更加有效地匹配并且工作更加接近于最佳狀態，因而在負載一定時，使得壓氣機和渦輪級數最少。采用高強度的輕質材料也是一個重要因素。
50．對一定的質量流量來說，由于排氣速度較低，內外涵發動機產生的推力較小。因此，為了獲得同樣的推力，內外涵發動機必須按比例比純渦輪噴氣發動機通過更大的總質量流量。然而，由于發動機的高壓部分的尺寸減小，發動機的重量仍然較輕。因此，除了耗油率減少外，功率重量比也得到提高。
Rolls-Royce RB168 Mk202/Mk203
Rolls-Royce RB39 Clyde
Encouraged by results obtained from the Trent, Rolls-Royce decided to go ahead with an engine designed from the start as a turbo-prop. Named the Clyde it utilized the axial compressor from the Metrovick F2 as first stage and a scaled up supercharger impeller from a Merlin as second stage. First running in August 1945 at 2000 shp, later engines produced up to 4200 shp.
緒言
1．在航空燃氣渦輪發動機的設計階段，設計、制造、發展和產品支援之間應保持密切聯系，以確保最后的設計在工程規范和制造工藝能力之間的協調。
22: Manufacture
第二十二章 制造
Contents Page
Introduction 229 2．由于這種發動機具有很高的推重比，所以其功能要求每個部件具有盡可能高的性能。為了符合這種要求，每個部件必須造得重量盡可能輕，費用盡可能低，而且在很長的使用壽命期中具有機械完整性。因此，制造中采用的方法是多種多樣的，通常取決于每個部件必須完成的任務。
緒言
制造策略
Manufacturing strategy 230 Forging 231 鍛造
鑄造
Casting 233 Fabrication 234 組裝加工
焊接
Welding 235
Tungsten inert gas (T.I.G.) welding Electron beam welding (E.B.W.)
Electro-chemical
machining (E.C.M.) 237 Stem drilling Capillary drilling
Electro-discharge machining (E.D.M.) 238 Composite materials and sandwich casings 240 鎢惰性氣體(T.I.G.)焊接
電子束焊接(B.E.W.)
電化學加工(E.C.M.)
深孔鉆削
微孔鉆削
電火花加工(E.D.M.)
復合材料和夾芯殼體
檢驗
Inspection 240
INTRODUCTION 3. No manufacturing technique or process that In any way offers an advantage is ignored and most
1. During the design stages of the aircraft gas available engineering methods and processes areturbine engine, close liaison is maintained between employed in the manufacture of these engines, Indesign, manufacturing, development and product some instances, the technique or process may support to ensure that the final design is a match appear by some standards to be elaborate, time between the engineering specification and the man-consuming and expensive, but is only adopted after ufacturing process capability.
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