10: Fuel system
目 錄
Contents Page
Introduction 95
Manual and automatic control 96
緒言
手動及自動控制
燃油控制系統
Fuel control systems 99
Pressure control (turbo-propeller engine) Pressure control (turbo-jet engine) Flow control Combined acceleration and speed control 壓力控制(渦輪螺槳發動機)
壓力控制(渦輪噴氣發動機)
流量控制
組臺式加速及轉速控制
壓力比控制
Pressure ratio control
發動機電子控制
Electronic engine control 111 Speed and temperature control amplifiers 轉速及溫度控制放大器
發動機管理控制
Engine supervisory control
低壓燃油系統
燃油泵
Low pressure fuel system 112 Fuel pumps 112 Plunger-type fuel pump
柱塞式燃油泵
齒輪式燃油泵
Gear-type fuel pump Fuel spray nozzles 114 Fuel heating 116 Effect of a change of fuel 116 燃油噴嘴
燃油加溫
燃油改變的影響
燃氣渦輪發動機燃油
Gas turbine fuels 117
Fuel requirements Vapour locking and boiling 燃油的技術條件
蒸氣堵塞及沸騰
燃油污染控制
Fuel contamination control
第十章 燃油系統
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．為了防止發動機燃氣溫度、壓氣機出口壓力、及旋轉組件的轉速超出它們的最大極限值，一些自動安全控制器也是必要的。
4．通常燃油系統還有一些輔助功能，如滑油冷卻
(第8章)和發動機的各種控制系統的液壓控制；例
如，壓氣機空氣流量控制(第3章)。
手動和自動控制
5．燃氣渦輪發動機的功率或推力的控制受注入燃
燒系統的燃油量調節的影響。當需要增大推力時，油門開大，由于增大燃油流量，燃油霧化噴嘴的壓力增大。這便產生了增高燃氣溫度的作用，它進而又增加了通過渦輪的燃氣加速度，提高發動機轉速，并相應增加空氣流量，從而增大發動機的推力。
6．而且，高度、空氣溫度和飛機速度的變化使流過發動機的空氣流量和供應的燃油之間的關系更為復雜。這些變量改變著發動機進口的空氣密度，從而改變流過發動機的空氣質量。圖10-1所示為典型的空氣流量隨高度的變化曲線。為了適應空氣流量的這一變化，燃油流量(圖10-2)應當發生相似的變化。否則空氣流量與燃油流量之比將會變化，使
發動機轉速增大或減小而偏離油門桿位置選定的原定值。
3．對于渦輪-螺槳發動機，由于螺旋槳轉速及槳距的變化對發動機功率輸出有影響，應將它們納入考慮。因此，通常將油門桿和螺旋槳控制器相互連接起來。這樣，就可以在發動機所有轉速下在燃油流量和空氣流量之間保持正確的關系，駕駛員控制發動機只要一根油門桿就行。雖然，通常發動機的最大轉速是由螺旋槳轉速控制器決定的，但其超轉最終是用燃油系統中的調節器來防止。
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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