37.
During a rapid acceleration, the sudden decrease in throttle pressure difference is sensed by the A.S.U., causing the spill valve to close, Such a rapid increase in fuel supply would, however, create an excessive gas temperature and also cause the compressor to surge (Part 3). This occurs because the inertia of the rotating assembly results in an appreciable time lag in the rate of airflow increase. It is essential therefore, to have an acceleration control to override the A.S.U. to give a corresponding lag in the rate of fuel flow increase.
38.
The rapid initial increase of fuel flow causes a rise in the pressure difference across the fuel metering plunger and this is sensed by a diaphragm in the pressure drop control section. At a fixed value of over fuelling, the pressure drop control diaphragm opens its servo spill valve to override the A.S.U, and maintains a constant pressure difference across the metering plunger.
39.
The increased fuel supply causes the engine to accelerate and the fuel metering plunger gives the maximum permissible fuel flow to match the increasing compressor delivery pressure. This it achieves through the A.C.U. servo system, which is under the control of a spill valve operated by compressor delivery air pressure acting on a capsule.
40.
As the compressor delivery pressure continues to rise, the capsule is compressed to open the spill valve and to bleed pressure from above the metering plunger. Pump delivery pressure acting underneath the plunger causes it to lift, this increases the area of the main fuel flow passage.
37.當(dāng)快速加速時，高度傳感裝置感測到油門壓差突然降低，導(dǎo)致溢流活門關(guān)閉。然而，燃油供應(yīng)如此急速的增加會產(chǎn)生過高的燃氣溫度，并導(dǎo)致壓氣機喘振(第3章)。這種情況發(fā)生的原因是，旋轉(zhuǎn)組件的慣性使得空氣流量增加的速率有相當(dāng)大的時間滯后。因而必須有一套加速控制器來超控高度傳感裝置，使燃油流量增加的速率也有相應(yīng)的滯后。
104
氣機出口壓力相匹配。這一功能是通過加速控制裝置的伺服系統(tǒng)而實現(xiàn)的。該伺服系統(tǒng)由溢流活門控制，而該活門由作用在膜片上的壓氣機出口空氣壓力來操作。
40．當(dāng)壓氣機供氣壓力繼續(xù)提高時，膜片受壓縮，將溢流活門打開，從節(jié)流柱塞上方釋放壓力。作用在柱塞下方的油泵的供油壓力將其升起，這樣便增大了主燃油流動通道的面積。
38．燃油流量快速地開始增加導(dǎo)致燃油節(jié)流柱塞前后的壓差增加，這由壓降控制部分的膜片感測。在過量供油的某個定值下，壓降控制膜片打開它的伺服溢流活門，超控高度傳感裝置的控制，并使節(jié)流柱塞前后的壓差保持恒定。
39．增大了的燃油供應(yīng)量導(dǎo)致發(fā)動機加速，同時，燃油節(jié)流柱塞供應(yīng)允許的最大燃油流量，使之與增加著的壓
Fuel system
41. The pressure drop control spill valve closes to the fuel output in the same way as the gas increase the fuel pump delivery and maintains the temperature control. 41．壓降控制溢流活門關(guān)閉，使燃油泵供油增加，并保持柱塞前后的控制壓差。因此，燃油流量隨著壓氣機空氣流量的增加逐漸增加。通過負責(zé)增大膜片上壓力信號的空氣開關(guān)能自動改變過量供油的程
度。現(xiàn)在，壓氣機供氣壓力的全部數(shù)值已傳遞給加速控制裝置的膜片組件，從而增加了節(jié)流柱塞的開啟率。
42．當(dāng)受控的過量供油繼續(xù)進行時，油門活門前后的壓差增大。當(dāng)其到達控制值時，高度傳感裝置由于增加了比例流量而起作用，重新為噴嘴提供穩(wěn)定的燃油流量。
43．發(fā)動機轉(zhuǎn)速調(diào)節(jié)器可以是第15段所述的壓力控制式，也可以是第23段所述的液壓機械式的。
44．液壓機械調(diào)節(jié)器的伺服壓力控制，與壓力控制調(diào)節(jié)器非常相似，但調(diào)節(jié)器壓力由油泵供油流過一個限制器之后取得，限制壓力受旋轉(zhuǎn)式溢流活門的控制；這種調(diào)節(jié)器不受燃油比重改變的影響。
controlling pressure difference across the plunger. The fuel flow, therefore, progressively rises as airflow through the compressor increases. The degree of overfuelling can be automatically changed by the air switch, which increases the pressure signal on to the capsule. The full value of compressor delivery pressure is now passed on to the A.C.U. capsule assembly, thus increasing the opening rate of the metering plunger.
42. As the controlled overfuelling continues, the pressure difference across the throttle valve increases. When it reaches the controlling value, the
A.S.U. takes over due to the increasing proportional flow and again gives a steady fuel flow to the spray nozzles.
43.
The engine speed governor can be of the pressure control type described in para. 15, or a hydro-mechanical governor as described in para. 23.
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