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两种不同类型的轴承,即多数用于大型机器上的安装在轴的两端的轴承(外置式轴承)和主要用于小型增压器上的安装在压气机叶轮和涡轮轮盘之间的轴承(内置式轴承),在涡轮增压器市场上都已经被证明是成功的。本文利用计算和根据已有经验论述了这两种类型轴承的基本差别,重点讨论其转子动力学特性和轴承需要的条件。外置式轴承的轴承力较小,它允许在压气机叶轮和涡轮处有较小的间隙。轴承的磨擦损失(特别在低负荷时)较小。而外置式轴承,无论是滚动轴承或滑动轴承都可以采用自循环润滑系统,因而轴承的可接近性较好。然而在某些特殊的应用场合下,内置式轴承有其优越之处,这主要是指涡轮增压器可以有更多的方式与柴油机连接。这两种轴承究竟哪一种好,没有公认的结论。在较小型的涡轮增压器上,B.B.C公司两种轴承形式都采用,而在大型机器上则只使用外置式轴承,其理由详述在后。
Two different types of bearings, most of the bearings (external bearings) mounted on both ends of the shaft for large machines, and the bearings mounted on the small supercharger between the compressor wheel and the turbine wheel (Built-in bearings), have proved successful in the turbocharger market. In this paper, the basic differences between the two types of bearings are discussed by calculation and based on the existing experience. The dynamic characteristics of the rotor and the necessary conditions of the bearing are discussed in detail. The external bearing has a small bearing force, which allows for a small clearance between the compressor impeller and the turbine. The bearing friction loss (especially at low loads) is small. The external bearings, whether it is rolling bearings or sliding bearings can be used since the lubrication system, so the proximity of the bearing is better. However, in some special applications, the built-in bearing has its advantages, which mainly means that the turbocharger can have more ways to connect with the diesel engine. Which of these two bearings is good, there is no generally accepted conclusion. On smaller turbochargers, both B.B.C bearings are used, whereas on larger machines only external bearings are used, the reason for which is detailed below.