齿间集油容量
(在供油泵中的滑油或在回油泵中的空气／滑油)
图8-5 一种齿轮泵的工作原理
Fig. 8-5 Principle of a gear pump.
cylinder is achieved by a spring forcing the piston to its original position. This reduces the pressure between the cylinder and the oil tank which allows the oil replenshing valves to open until the cylinder is recharged.
20.
The most common type of oil distribution device is a simple orifice which directs a metered amount of oil onto its target. These jet orifices are positioned as close to the target area as possible to overcome the possibility of the local turbulent environment deflecting the jet of oil. The smallest diameter of a jet orifice is 0.04 inch which allows a flow of 12 gallons per hour when operating at a pressure of 40 lb. per sq. in. The use of restrictors upstream can reduce the flow rate if required.
21.
All engines transfer heat to the oil by friction, churning and windage within a bearing chamber or gearbox. It is therefore common practice to fit an oil cooler in recirculatory oil systems. The cooling medium may be fuel or air and, in some instances, both fuel-cooled and air-cooled coolers are used.
低压进口
低压滑油
高压滑油
机匣
高压出口
21.所有的发动机都会因轴承腔或齿轮箱内的摩擦、搅动和风阻向滑油传热。因此，一般的做法是在循环滑油系统中装一个滑油散热器。冷却介质可以是燃油或空气，在某些情况下同时使用燃油冷却的和空气冷却的散热器。
23．燃油冷却滑油散热器(图8-7)有一个蜂窝散热组件，由折流板分隔成段。大量的导管穿过蜂窝散热器输送燃油，滑油在折流板的引导下经一系列通道流过这些管子外面。热量由滑油传给燃油，因此降低了滑油温度。
22．某些同时使用两种散热器的发动机，可以设一套电子监控系统，只在需要的时候才将空气冷却的散热器打开。这样可保持理想的滑油温度和提高总的热效率。
24．燃油冷却滑油散热器在滑油的进口和出口之间装有一个旁通活门。该活门在预先设定的散热器前后压差下工作，从而防止在堵塞的情况下发动机缺滑油。通常在散热器的输油路上还安装一个压力保持活门，它保证滑油压力总是高于燃油压力。在散热器发生内部故障的情况下，滑油会漏入燃油系统，而不是燃油漏入滑油系统发生潜在的危险。
25.空气冷却滑油散热器与燃油冷却式相比，两者在结构和工作上都相似。主要差别是利用空气作为冷却介质。
Lubrication
图8-6 一次压射式滑油泵
Fig. 8-6 A single-shot oil pump.
22.
Some engines which utilize both types of cooler may incorporate an electronic monitoring system which switches in the air-cooled cooler only when it is necessary. This maintains the ideal oil temperature and improves the overall thermal efficiency.
23.
The fuel-cooled oil cooler (fig. 8-7) has a matrix which is divided into sections by baffle plates. A large number of tubes convey the fuel through the matrix, the oil being directed by the baffle plates in a series of passes across the tubes. Heat is transferred from the oil to the fuel, thus lowering the oil temperature.
24.
The fuel-cooled oil cooler incorporates a bypass valve fitted across the oil inlet and outlet. The valve operates at a pre-set pressure difference across the
高压燃油
低压燃油
cooler and thus prevents engine oil starvation in the event of a blockage. A pressure maintaining valve is usually located in the feed line of the cooler which ensures that the oil pressure is always higher than the fuel pressure. In the event of a cooler internal fault developing, the oil will leak into the fuel system rather than the potentially dangerous leakage of fuel into the oil system.
25.
The air-cooled oil cooler is similar to the fuel-cooled type in both construction and operation; the main difference is that air is used as the cooling medium.
26.
Magnetic plugs, or chip detectors (fig. 8-8), are fitted on the scavenge (return) side to collect ferritic
油泵再次充油
滑油出口
滑油温度传感嚣
滑油旁路活门
滑油进口
燃油进口
蜂窝结构
散热组件
低压燃油
供滑油
折流板
燃油出口
Lubrication
26．磁性堵头，即磁性探屑器(图8-8)装在回油路上，用来收集来自各个轴承腔的铁屑。它们基本上是插在滑油流道中的永久磁铁，固定在甘行封严的活门座上。设计中采用了一些特有的保险办法，以保证探屑器能正确地安置在活门座上。根据检查，它们可以提供故障临近的警告，而无需拆卸和检查油滤。它们设计成在维护检查时拆卸，用于状态监视的目的(第24章)，而不发生滑油损失。另外，它们还可能接通驾驶舱的警告系统，提供飞行中的指示。
图8-7 一种低压燃油冷却滑油散热器
Fig. 8-7 A low pressure fuel-cooled oil cooler.
图8-8 一种磁性探屑器
28．为防止滑油箱、齿轮箱和轴承腔中的空气压力过高，在润滑系统中有通大气的通风口。在空气通往机外之前，空气中的任何油滴将被离心通风机分离出来。有些通风机中有多孔中间体，构成空气分离段，提高了油气分离的效率(图8-10)。
27.在某些发动机上，为了尽量减小从旋转组件传向轴承座的动力载荷的影响，采用了“挤压油膜”式轴承(图8-9)。它们在轴承外圈和轴承座之间留有很小的间隙，该间隙中充满了滑油。该油膜阻尼了旋转组件的径向运动及传向轴承座的动力载荷，因此减低了发动机的振动水平及疲劳损坏的可能性。
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