10: Fuel system
目 录
Contents Page
Introduction 95
Manual and automatic control 96
绪言
手动及自动控制
燃油控制系统
Fuel control systems 99
Pressure control (turbo-propeller engine) Pressure control (turbo-jet engine) Flow control Combined acceleration and speed control 压力控制(涡轮螺桨发动机)
压力控制(涡轮喷气发动机)
流量控制
组台式加速及转速控制
压力比控制
Pressure ratio control
发动机电子控制
Electronic engine control 111 Speed and temperature control amplifiers 转速及温度控制放大器
发动机管理控制
Engine supervisory control
低压燃油系统
燃油泵
Low pressure fuel system 112 Fuel pumps 112 Plunger-type fuel pump
柱塞式燃油泵
齿轮式燃油泵
Gear-type fuel pump Fuel spray nozzles 114 Fuel heating 116 Effect of a change of fuel 116 燃油喷嘴
燃油加温
燃油改变的影响
燃气涡轮发动机燃油
Gas turbine fuels 117
Fuel requirements Vapour locking and boiling 燃油的技术条件
蒸气堵塞及沸腾
燃油污染控制
Fuel contamination control
第十章 燃油系统
INTRODUCTION fuel to the fuel spray nozzles, which inject it into the combustion system (Part 4) in the form of an
1. The functions of the fuel system are to provide atomized spray. Because the flow rate must vary the engine with fuel in a form suitable for combustion according to the amount of air passing through the and to control the flow to the required quantity engine to maintain a constant selected engine speed necessary for easy starting, acceleration and stable or pressure ratio, the controlling devices are fullyrunning, at all engine operating conditions. To do automatic with the exception of engine power this, one or more fuel pumps are used to deliver the selection, which is achieved by a manual throttle or 2．为了防止发动机燃气温度、压气机出口压力、及旋转组件的转速超出它们的最大极限值，一些自动安全控制器也是必要的。
4．通常燃油系统还有一些辅助功能，如滑油冷却
(第8章)和发动机的各种控制系统的液压控制；例
如，压气机空气流量控制(第3章)。
手动和自动控制
5．燃气涡轮发动机的功率或推力的控制受注入燃
烧系统的燃油量调节的影响。当需要增大推力时，油门开大，由于增大燃油流量，燃油雾化喷嘴的压力增大。这便产生了增高燃气温度的作用，它进而又增加了通过涡轮的燃气加速度，提高发动机转速，并相应增加空气流量，从而增大发动机的推力。
6．而且，高度、空气温度和飞机速度的变化使流过发动机的空气流量和供应的燃油之间的关系更为复杂。这些变量改变着发动机进口的空气密度，从而改变流过发动机的空气质量。图10-1所示为典型的空气流量随高度的变化曲线。为了适应空气流量的这一变化，燃油流量(图10-2)应当发生相似的变化。否则空气流量与燃油流量之比将会变化，使
发动机转速增大或减小而偏离油门杆位置选定的原定值。
3．对于涡轮-螺桨发动机，由于螺旋桨转速及桨距的变化对发动机功率输出有影响，应将它们纳入考虑。因此，通常将油门杆和螺旋桨控制器相互连接起来。这样，就可以在发动机所有转速下在燃油流量和空气流量之间保持正确的关系，驾驶员控制发动机只要一根油门杆就行。虽然，通常发动机的最大转速是由螺旋桨转速控制器决定的，但其超转最终是用燃油系统中的调节器来防止。
Fuel system
power lever. A fuel shut-off valve (cock) control lever is also used to stop the engine, although in some instances these two manual controls are combined for single-lever operation.
2.
It is also necessary to have automatic safety controls that prevent the engine gas temperature, compressor delivery pressure, and the rotating assembly speed, from exceeding their maximum limitations.
3.
With the turbo-propeller engine, changes in propeller speed and pitch have to be taken into account due to their effect on the power output of the engine. Thus, it is usual to interconnect the throttle lever and propeller controller unit, for by so doing the correct relationship between fuel flow and airflow is maintained at all engine speeds and the pilot is given single-lever control of the engine. Although the maximum speed of the engine is normally determined by the propeller speed controller, over-speeding is ultimately prevented by a governor in the fuel system.
4.
The fuel system often provides for ancillary functions, such as oil cooling (Part 8) and the hydraulic control of various engine control systems; for example, compressor airflow control (Part 3).
MANUAL AND AUTOMATIC CONTROL
5.
The control of power or thrust of the gas turbine engine is effected by regulating the quantity of fuel injected into the combustion system. When a higher thrust is required, the throttle is opened and the pressure to the fuel spray nozzles increases due to the greater fuel flow. This has the effect of increasing the gas temperature, which in turn increases the acceleration of the gases through the turbine to give a higher engine speed and a correspondingly greater airflow, consequently producing an increase in engine thrust.
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