加力燃油
(顏色的變化
表示活門前后
的壓力降低)
低壓燃油
由主系統來的高壓燃油
限制的高壓燃油
高壓壓氣機出口壓力(P3)
噴管壓力(P6)
催化劑點火器
蒸汽槽
主壓降
調節器
主燃油總管
加力燃燒室
燃油控制裝置
蒸汽槽壓降調節器
燃油泵
蒸汽槽節流活門
到噴口
滑油泵
總流量節流活門
伺服活塞
進口油門
壓力比控制裝置
可調小孔
選擇加力
和關閉活門
停車
駕駛員
操縱桿
燃油點燃
控制活門
正常
工作范圍
加力燃燒室
工作范圍
圖16-6 一種簡化的典型的加力燃燒室燃油控制系統
Fig. 16-6 A simplified typical afterburner fuel control system.
176
21．可通過裝有加力燃燒裝置的低涵道比發動機獲得高達70％的靜推力增加，且在高的前進速度時能獲得比這一增加量大幾倍的推力增加。在低涵道比發動機上獲得的推力增加量大，是因為在排出的燃氣流中有大量的氧氣以及排氣流的較低初始溫度。
20．假設加力燃燒前的燃氣溫度為640℃（913deg. K.），開加力后為1269℃（1542deg. K.），則溫度比=1542/913=1.69。噴氣流的速度按溫度比的平方根增加。因此，噴氣速度的增加倍數=根號1.69＝1.3。即噴氣流的速度增加了30％，這時發動機的靜推力也增加了30％(圖16-8)。
圖16-7 一種簡化的典型的加力燃燒室噴口控制系統
Fig. 16-7 A simplified typical afterburner nozzle control system.
20.
Assuming a gas temperature before afterburn-ing of 640 deg. C. (913 deg. K.) and with afterburn-ing of 1,269 deg. C. (1,542 deg. K.). then the
temperature ratio = 1,542 = 1.69. 913
The velocity of the jet stream increases as the
square root of the temperature ratio. Therefore, the
jet velocity = ^/T.69 = 1.3. Thus, the jet stream
velocity is increased by 30 per cent, and the increase
in static thrust, in this instance, is also 30 per cent
推力增加％
(fig. 16-8).
21.
Static thrust increases of up to 70 per cent are obtainable from low by-pass engines fitted with after-burning equipment and at high forward speeds several times this amount of thrust boost can be obtained. High thrust boosts can be achieved on low by-pass engines because of the large amount of oxygen in the exhaust gas stream and the low initial temperature of the exhaust gases.
噴管魚鱗片
油箱壓力
低壓滑油
中壓滑油
高壓滑油
噴口作動筒
噴口滑油泵
低壓滑油泵
從滑油箱來
到壓力比控制裝置
旁路活門
圖16-8 推力增加和溫度比的關系圖
177 22. It is not possible to go on increasing the amount of fuel that is burnt in the jet pipe so that all the available oxygen is used, because the jet pipe would not withstand the high temperatures that would be incurred and complete combustion cannot be assured.
溫度比
22.繼續增加在噴管中燃燒的燃油量以致完全用完可用的氧氣是不可能的，因為噴管經受不住其造成的高溫，完全燃燒也無法保證。
FUEL CONSUMPTION
23. Afterburning always incurs an increase in specific fuel consumption and is, therefore, generally limited to periods of short duration. Additional fuel must be added to the gas stream to obtain the required temperature ratio (para. 19). Since the temperature rise does not occur at the peak of compression, the fuel is not burnt as efficiently as in the engine combustion chamber and a higher specific fuel consumption must result. For example, assuming a specific fuel consumption without after-burning of 1,15 lb./hr./lb. thrust at sea level and a speed of Mach 0,9 as shown in fig. 16-9. then with 70 per cent afterburning under the same conditions of flight, the consumption will be increased to
Fig. 16-9 Specific fuel consumption圖16-9 燃油消耗率比較
comparison.
高度×1000英尺
耗油率
磅/小時/磅推力
70％的加力
圖16-10 加力及其對爬升率的影響
Fig. 16-10 Afterburning and its effect on the rate of climb.
approximately 2.53 lb./hr./lb. thrust. With an increase this additional fuel consumption is combined with the in height to 35,000 feet this latter figure of 2.53 improved rate of take-off and climb (fig. 16-10), it is lb./hr./lb. thrust will fall slightly to about 2.34 lb./hr./lb. found that the amount of fuel required to reduce the 23.加力燃燒總是造成耗油率的增加，因此，使用加力一般都限制在很短的一段時間內。必須給燃氣流增加額外的燃油以獲得所要求的溫度比（第19段）。由于溫度升高不是發生在壓力的峰值狀態，因此燃油的燃燒不如在發動機燃燒室中燃燒得那樣有效，結構造成耗油率較高。比如：假設在海平面速度為馬赫數0.9每一打開加力時燃油消耗率為1.15磅/小時/磅推力，如圖16-9所示，在同樣的飛行條件下，如有70％的加力，則耗油率將增加到大約2.53磅／小時／磅推力。高度增加到35000英尺時，由于進口空氣溫度減小的緣故，這個2.53磅／小時／磅推力的耗油率會稍微下降一點，為2.34磅／小時／磅推力。當額外的油耗與提高了的起飛和爬升率(圖16-10)結合在一起考慮時，就會發現，為了減少達到作戰高度的時間所需要的燃油量并不過多。 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：勞斯萊斯噴氣引擎－中英(88)
