加力燃油
(颜色的变化
表示活门前后
的压力降低)
低压燃油
由主系统来的高压燃油
限制的高压燃油
高压压气机出口压力(P3)
喷管压力(P6)
催化剂点火器
蒸汽槽
主压降
调节器
主燃油总管
加力燃烧室
燃油控制装置
蒸汽槽压降调节器
燃油泵
蒸汽槽节流活门
到喷口
滑油泵
总流量节流活门
伺服活塞
进口油门
压力比控制装置
可调小孔
选择加力
和关闭活门
停车
驾驶员
操纵杆
燃油点燃
控制活门
正常
工作范围
加力燃烧室
工作范围
图16-6 一种简化的典型的加力燃烧室燃油控制系统
Fig. 16-6 A simplified typical afterburner fuel control system.
176
21．可通过装有加力燃烧装置的低涵道比发动机获得高达70％的静推力增加，且在高的前进速度时能获得比这一增加量大几倍的推力增加。在低涵道比发动机上获得的推力增加量大，是因为在排出的燃气流中有大量的氧气以及排气流的较低初始温度。
20．假设加力燃烧前的燃气温度为640℃（913deg. K.），开加力后为1269℃（1542deg. K.），则温度比=1542/913=1.69。喷气流的速度按温度比的平方根增加。因此，喷气速度的增加倍数=根号1.69＝1.3。即喷气流的速度增加了30％，这时发动机的静推力也增加了30％(图16-8)。
图16-7 一种简化的典型的加力燃烧室喷口控制系统
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.
喷管鱼鳞片
油箱压力
低压滑油
中压滑油
高压滑油
喷口作动筒
喷口滑油泵
低压滑油泵
从滑油箱来
到压力比控制装置
旁路活门
图16-8 推力增加和温度比的关系图
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.
温度比
22.继续增加在喷管中燃烧的燃油量以致完全用完可用的氧气是不可能的，因为喷管经受不住其造成的高温，完全燃烧也无法保证。
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图16-9 燃油消耗率比较
comparison.
高度×1000英尺
耗油率
磅/小时/磅推力
70％的加力
图16-10 加力及其对爬升率的影响
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.加力燃烧总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时间内。必须给燃气流增加额外的燃油以获得所要求的温度比（第19段）。由于温度升高不是发生在压力的峰值状态，因此燃油的燃烧不如在发动机燃烧室中燃烧得那样有效，结构造成耗油率较高。比如：假设在海平面速度为马赫数0.9每一打开加力时燃油消耗率为1.15磅/小时/磅推力，如图16-9所示，在同样的飞行条件下，如有70％的加力，则耗油率将增加到大约2.53磅／小时／磅推力。高度增加到35000英尺时，由于进口空气温度减小的缘故，这个2.53磅／小时／磅推力的耗油率会稍微下降一点，为2.34磅／小时／磅推力。当额外的油耗与提高了的起飞和爬升率(图16-10)结合在一起考虑时，就会发现，为了减少达到作战高度的时间所需要的燃油量并不过多。 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：劳斯莱斯喷气引擎－中英(88)
