67．可調(diào)節(jié)流孔面積的控制是壓力比控制裝置的一種功能，它位于燃油流量調(diào)節(jié)器中。壓力比控制活門感受P4和P1壓力，調(diào)節(jié)燃油流量調(diào)節(jié)器膜盤的移動，進而控制可調(diào)節(jié)流孔的面積。以產(chǎn)生油門或功率操縱桿所給定的壓力比。
68．在任何一個穩(wěn)定的運轉(zhuǎn)狀態(tài)，燃油泵的供油輸出總是大于發(fā)動機的需求。壓力降溢流活門的打開，可使過剩的燃油返回到油泵的進口側(cè)。這個動作接燃油流量調(diào)節(jié)器所要求的值控制供油量。
pressure drop control piston. It therefore gives a sat-triangular orifice, known as the variable metering
isfactory idling fuel flow at all altitudes.
64. On engines featuring water injection (Part 17), a reset device (fig. 10-11), operated by a piston and reset cam, increases the loading on the throttle control spring and stirrup arm, thus selecting a higher engine speed during water injection. To prevent the power limiter (fig, 10-9) cancelling the effect of water injection, a capsule in the limiter is subjected to water pressure to raise the compressor delivery pressure at which the power limiter operates.
Pressure ratio control
65. The pressure ratio control (fig. 10-12) is a mechanical system similar to the combined acceler-ation and speed control system, but uses the ratio of
H.P. compressor delivery pressure to air intake pressure (P4/P1) as the main controlling parameter. It needs no separate governor unit for controlling the maximum r.p.m. The controlling mechanism is contained in one unit, which is usually referred to as a fuel flow regulator (F.F.R.). A gear-type pump is used, as described in para. 88, and the pump output to the F.F.R. is controlled by a pressure drop spill valve.
66. The F.F.R. is driven by the engine through a gear train and has two rotating valves. One valve, orifice (V.M.O.), and this sleeve is given axial movement by a capsule assembly. The other valve, known as the pressure drop control valve, is provided with axial movement by a centrifugal governor, known as a pressure drop control governor, Both valves form variable restrictors which control the fuel flow to the spray nozzles.
67.
Control of the V.M.O. area is a function of a pressure ratio control unit housed in the F.F.R. A pressure ratio control valve, subjected to P4 and P1, pressures, regulates the movement of the F.F.R. capsule and thus controls the V.M.O. area to produce the pressure ratio dictated by the throttle or power lever.
68.
At any steady running condition, the output of the fuel pump is greater than the engine requirement. The pressure drop spill valve is open to allow surplus fuel to return to the inlet side of the pump. This action controls the fuel delivery to that demanded by the
F.F.R.
69. When the throttle is slowly opened, the throttle-controlled orifice is increased and the control pressure falls, thus allowing the pressure ratio control valve to move towards the closed position (acceleration stop). F.F.R. capsule chamber pressure 水
高壓
空氣
圖10-11 噴水調(diào)整對轉(zhuǎn)速控制調(diào)節(jié)器的影響
Fig. 10-11 Effect of water reset on speed control governor.
低壓燃油
油泵供油(高壓燃油)
高壓燃油去燃油
流量調(diào)節(jié)器進口
初級燃油
主燃油
Fuel system
降低高壓壓氣機
出口壓力(部分P4)
燃油流量調(diào)節(jié)器
膜盒腔內(nèi)壓力
控制壓力
去低壓系統(tǒng) 來自低壓系統(tǒng) 減壓活門 作動筒 放大器
燃油流量調(diào)節(jié)器膜盒
69．當(dāng)油門緩慢打開時，被油門控制的孔增大，控制壓力下降，因而允許壓力比控制活門向關(guān)閉位置移動(停止加速)。燃油流量調(diào)節(jié)器膜盒腔的壓力增加，膜盒帶動節(jié)流套筒，來增大可調(diào)節(jié)流孔的面積。打開可調(diào)節(jié)流孔的效果是減小壓力差。壓力差由壓力降調(diào)節(jié)器感測，它打開壓力降控制孔。降低了的系統(tǒng)壓力差直接由壓力降溢流活門感測，它向關(guān)閉位置移動，由此增加燃油輸出。增加的燃油流量使發(fā)動機加速，隨之增大壓力比(P4／P1)。當(dāng)達到要求的壓力比之后，壓力比控制活門打開，燃油流量調(diào)節(jié)器膜盤腔的壓力降低。膜盒組件發(fā)生膨脹，移動可調(diào)節(jié)流孔套筒，以減小孔的面積。由此增加的壓力差由壓力降控制調(diào)節(jié)器感測，它將壓力降控制孔調(diào)節(jié)到某一點上，在這一點時能使壓力降溢流活門給出的燃油供油量符臺穩(wěn)態(tài)運轉(zhuǎn)的要求。
控制膜盒
壓降控制調(diào)節(jié)器
減速止動釘
壓比控制器
噴嘴
加速止動釘
壓比控制活門
真空膜盒
油門控制孔
高壓燃油
停車活門
慢車調(diào)節(jié)器
油門桿
壓降控制孔
通氣口
地面慢車電磁閥
P1控制孔
微調(diào)活門
可調(diào)節(jié)流套筒
真空膜盒
燃油量調(diào)節(jié)器
可調(diào)節(jié)流孔
進氣道(P1)
高壓壓氣機進口(P3)
高壓壓氣機出口(P4)
燃氣溫度熱電偶
輔助油門開關(guān)
空氣壓力控制
低壓軸轉(zhuǎn)速
壓力降
溢流活門
燃油壓力
可調(diào)限流器
燃油泵及
活門組件
圖10-12 一種壓力比控制裝置
110
而活門碰到加速止動銷。燃油流量調(diào)節(jié)器膜盒腔內(nèi)壓力增加，膜盒移動，將可調(diào)節(jié)流孔的面積增加。這個動作一直繼續(xù)進行到達到要求的壓力比P4／P1時為止。增加的P4壓力使壓力比控制膜盒重新膨脹，活門返回到穩(wěn)定運轉(zhuǎn)位置。
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