工作循環
2．燃氣渦輪發動機的工作循環類似于4沖程活塞發動機。然而，在燃氣渦輪發動機中，燃燒在等壓下進行，而在活塞發動機中，燃燒時體積不變。這兩種發動機循環(圖2-1)表明每一種循環里都有進氣、壓縮、燃燒和排氣。這些過程在活塞發動機中是間歇性的，而在燃氣渦輪中是連續進行的�；钊l動機只有一個沖程用于產生功率，其余沖程用于工作流體的充填、壓縮和排放。相反，渦輪發動機取消了三個“不做功”沖程，因而能在更短時間內燃燒更多的燃油；所以，就一給定尺寸的發動機而言，它產生更大的功率輸出。
3. Due to the continuous action of the turbine engine and the fact that the combustion chamber is not an enclosed space, the pressure of the air does not rise, like that of the piston engine, during combustion but its volume does increase. This process is known as heating at constant pressure. Under these conditions there are no peak or fluctuating pressures to be withstood, as is the case with the piston engine with its peak pressures in excess of 1,000 lb. per sq. in. It is these peak pressures which make it necessary for the piston engine to employ cylinders of heavy construction and
3.由于渦輪發動機的連續作用和燃燒室不是一個封閉空間這一事實，在燃燒過程中，空氣壓力不象在活塞發動機中那樣上升，而其體積卻要增加。這種過程稱之為等壓加熱。在這些狀態下，沒有峰值壓力或波動壓力要承受。而活塞發動機的峰值壓力超過1000磅／平方英寸。就是這些峰值壓力使活塞發動機必須采用結構笨重的氣缸和高辛烷值燃油。相反，低辛烷值燃油和輕結構的燃燒室用于渦輪發動機。
4．圖2-2用最簡單的形式表示了燃氣渦輪發動機運行的工作循環。也即在壓力-體積圖上畫出來的循環。點A表示大氣壓下的空氣，它沿AB線得到壓縮。從B到C靠引入燃油并在等壓下燃燒向空氣加熱，因而空氣的體積增加很多。燃燒室(第4章)中的壓力損失用B和C間的壓降表示。從C到
D表示燃燒產生的燃氣通過渦輪和噴管膨脹并且排入大氣。在循環的這 一部分，膨脹燃氣中的部分能量靠渦輪轉變成機械功率；其余的能量，在它排入大氣時提供推進噴氣流。
排氣
間歇的
排氣
燃燒
空氣／燃油進入 壓縮
進氣道
壓縮
連續的
燃燒
Working cycle and airflow
工作循環和氣流
燃燒(增加熱能)
圖2-1渦輪噴氣發動機和活塞發動機工作循環比較
Fig. 2-1 A comparison between the working cycle of a turbo-jet engine and a piston engine.
to use high octane fuels, in contrast to the low octane fuels and the light fabricated combustion chambers 壓力
used on the turbine engine.
4. The working cycle upon which the gas turbine engine functions is, in its simplest form, represented by the cycle shown on the pressure volume diagram in fig. 2-2. Point A represents air at atmospheric pressure that is compressed along the line AB. From B to C heat is added to the air by introducing and burning fuel at constant pressure, thereby consider-ably increasing the volume of air. Pressure losses in the combustion chambers (Part 4) are indicated by the drop between B and C. From C to D the gases resulting from combustion expand through the turbine and jet pipe back to atmosphere. During this part of the cycle, some of the energy in the Fig. 2-2 The working cycle on a pressure-expanding gases is turned into mechanical power by volume diagram. 膨脹(通過渦輪和噴管)
壓縮(增加壓力能)
外部空氣
容積
圖2-2 壓力體積圖上的工作循環
5.因為渦輪噴氣發動機是熱力發動機，燃燒溫度愈高，燃氣膨脹得愈多。然而，燃燒溫度必須不超過渦輪部件的設計和材料所適合的渦輪燃氣進口溫度值。
6．在渦輪部件中使用氣冷工作葉片允許更高的燃氣溫度，從而得到更高的熱效率。
工作循環和氣流
Working cycle and airflow
the turbine; the remainder, on its discharge to THE RELATIONS BETWEEN PRESSURE, 壓力、體積和溫度間的關系
atmosphere, provides a propulsive jet. VOLUME AND TEMPERATURE
7.在渦輪發動機的工作循環過程中，空氣流或“工作介質”接受并放出熱量，從而引起其壓力、體積和溫度變化。這些變化在其發生時密切相關，因為它們遵循在波伊爾和查里斯組合定律中所闡述的一項共同的原理。簡言之，它意指，工作循環各階段中空氣的壓力和體積之乘積與這些階段中空氣的絕對溫度成正比。不論用什么方式來改變空氣的狀態，這一關系都能適用。例如，無論是通過燃燒或者壓縮來加入能量，或者通過渦輪來抽取能量，熱能的變化總是與加入到燃氣或者從燃氣中抽取的功成正比。
5.
Because the turbo-jet engine is a heat engine, the higher the temperature of combustion the greater is the expansion of the gases. The combustion temperature, however, must not exceed a value that gives a turbine gas entry temperature suitable for the design and materials of the turbine assembly.
6.
The use of air-cooled blades in the turbine assembly permits a higher gas temperature and a consequently higher thermal efficiency.
7. During the working cycle of the turbine engine, the airflow or 'working fluid' receives and gives up heat, so producing changes in its pressure, volume and temperature. These changes as they occur are closely related, for they follow a common principle that is embodied in a combination of the laws of Boyle and Charles. Briefly, this means that the product of the pressure and the volume of the air at the various stages in the working cycle is proportion-al to the absolute temperature of the air at those
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