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1、Marine engines and auxiliary machinery船用发动机及辅机6.1 IntroductionThis Chapter provides an overview and typical examples of the main and auxiliary machinery and equipment found on ships. Machinery is often divided into the main or propulsion engines, electrical generation, systems such as electrical, pi
2、ping, refrigeration and air conditioning, fire fighting and protection, deck machinery and cargo handling equipment, bow thrusters and stabilizers, instrumentation and control, safety equipment and other auxiliary machinery and equipment. The auxiliary machinery may be in support of the main propuls
3、ion engines and include heat exchangers and compressed air, or in support of ship and cargo handling such as propellers and shafting, steering gear and deck cranes, or in support of ship services such as ballast water arrangements and sewage systems.6.1 简介本章主要介绍了船舶主机及辅机和船上其他设备并提供了典型例子。船舶机械通常分为主推进发动机
4、，船舶电站，系统包括电力、管路、制冷和空调、消防和保护、甲板机械和货物装卸设备，船首推进器和稳定器，仪器仪表控制系统，安全设备和其他辅助机械设备。辅机也可以用在主推进装置中，包括热交换器和空气压缩，或用在船舶货物装卸中，如螺旋桨、轴系、舵机、甲板起重机，或用在船舶服侍系统中，例如压载水系统和排污系统。6.2 Propulsion systemsThe range of propulsion systems that are either currently in use or have been under development are reviewed. The principal pro
5、pulsion devices are briefly reviewed by outlining their major features and characteristics together with their general areas of application.6.2 推进系统这一推进系统目前正在使用或者正在研发中的都是被审查的范围。主推进装置通过描绘它们在一般应用领域的功能和特点进行了简要概述。6.2.1 Fixed pitch propellersThe fixed pitch propeller has traditionally formed the basis of
6、 propeller production over the years in either its mono-block or built-up forms. Carlton (2007)6.2.1 固定螺距螺旋桨固定螺旋桨多年来已经形成了以单块或内置式为基础的形式。Carlton (2007)reviews the early development of the screw propeller. Whilst the mono-block propeller is commonly used today the built-up propeller, whose blades are c
7、ast separately from the boss and then bolted to it after machining, is now rarely used. This was not always the case since in the early years of the last century built-up propellers were very common, partly due to the inability to achieve good quality large castingsat that time and partly to difficu
8、lties in defining the correct blade pitch. In both these respects the built-up propeller has obvious advantages. Nevertheless, built-up propellers generally have a larger boss radius than its fixed pitch counterpart and this can cause difficulty with cavitation problems in the blade root section reg
9、ions in some cases.Mono-block propellers cover a broad spectrum of design types and sizes, ranging from those weighing only a few kilograms for use on small power-boats to those, for example, destined for large container ships which can weigh around 130 tonnes and require thesimultaneous casting of
10、significantly more metal in order to produce the casting. Figure 6.1 shows a collage of various types of fixed pitch propellerin use today. These types range from a large four-bladed propeller fitted to a bulk carrier and is seen in the figure in contrast to a man standing on thedock bottom, through
11、 highly skewed propellers for merchant and naval applications, to small high-speedpatrol craft and surface piercing propellers.As might be expected, the materials ofmanufacture vary considerably over such a wide range of designs and sizes. For the larger propellers,over 300 mm in diameter, the non-f
12、errous materialspredominate: high-tensile brass together with the manganese and nickelaluminium bronzes are the most favoured types of materials. However, stainless steel has also gained limited use. Cast iron, once a favourite material for the production of sparepropellers, has now virtually disapp
13、eared from use. Alternatively, for small propellers, use is frequentlymade of materials such as the polymers, aluminium, nylon and more recently carbon fibre composites.For fixed pitch propellers the choice of blade number, notwithstanding considerations of blade-to- blade clearances at the blade ro
14、ot to boss interface, is largely an independent variable and is normally chosen to give a mismatch to the range of hull, superstructure and machinery vibration frequencies which are considered likely to cause concern. Additionally, blade number is also a useful parameter in controlling unwelcome cav
15、itation characteristics. Blade numbers generally range from two to seven, although in some naval applications, where considerations of radiated noise become important, blade numbers greater than these have been researched and used to solve a variety of propulsion problems. For merchant vessels, howe
16、ver, four, five and six blades are generally favoured, although many tugs and fishing vessels frequently use three-blade designs. In the case of small work or pleasure power-boats two and three-bladed propellers tend to predominate. The early propeller design philosophies centred on the optimization
17、 of the efficiency from the propeller. Whilst today this aspect is no less important, and, in some respects associated with energy conservation, has assumed a greater importance, other constraints on design have emerged. These are in response to calls for the reduction of vibration excitation and ra
18、diated noise from the propeller. This latter aspect has of course been a prime concern of naval ship and torpedo propeller designers for many years; however, pressure to introduce these constraints, albeit in a generally less stringent form, into merchant ship design practice has grown in recent yea
19、rs. This has been brought about by the increases in power transmitted per shaft; the use of after deckhouses; the maximization of the cargo carrying capacity, which imposes constraints on the hull lines; ship structural failure and international legislation. For the majority of vessels of over 100 t
20、onnes displacement it is possible to design propellers on whose blades it is possible to control, although not eliminate, the effects of cavitation in terms of its erosive effect on the material, its ability to impair hydrodynamic performance and it being the source of vibration excitation. In this
21、latter context it must be remembered that there are very few propellers which are free from cavitation since the greater majority experience cavitation at some position in the propeller disc: submarine propellers when operating at depth, the propellers of towed array frigates and research vessels wh
22、en operating under part load conditions are notable exceptions, since these propellers are normally designed to be subcavitating to meet stringent noise emission requirements to minimize either detection or interference with their own instruments. Additionally, in the case of propellers operating at
23、 significant water depths such as in the case of a submarine, due account must be taken of the additional hydrostatic pressure-induced thrust which will have to be reacted by the ships thrust block.For some small, high-speed vessels where both the propeller advance and rotational speeds are high and
24、 the immersion low, a point is reached where it is not possible to control the effects of cavitation acceptably within the other constraints of the propeller design. To overcome this problem, all or some of the blade sections are permitted to fully cavitate, so that the cavity developed on the back
25、of the blade extends beyond the trailing edge and collapses into the wake of the blades in the slipstream. Such propellers are termed supercavitating propellers and frequently find application on high-speed naval and pleasure craft. Figure 6.2(c) illustrates schematically this design philosophy in c
26、ontrast to non-cavitating and partially cavitating propeller sections, shown in Figure 6.2(a) and (b) , respectively. When design conditions dictate a specific hydrodynamic loading together with a very susceptible cavitation environment, typified by a low cavitation number, there comes a point when
27、even the supercavitating propeller will not perform satisfactorily: for example, if the propeller tip immersion becomes so small that the propeller tends to draw air from the surface, termed ventilation, along some convenient path such as along the hull surface or down a shaft bracket. Eventually, i
28、f the immersion is reduced sufficiently by either the design or operational constraints the propeller tips will break surface. Although this condition is well known on cargo vessels when operating in ballast conditions and may, in these cases, lead to certain disadvantages from the point of view of
29、material fatigue and induced vibration, the surface breaking concept can be an effective means of propelling relatively small high-speed craft. Such propellers are termed surface piercing propellers and their design immersion, measured from the free surface to the shaft centre line, can be reduced t
30、o zero; that is, the propeller operates half in and half out of the water. In these partially immersed conditions the propeller blades are commonly designed to operate such that the pressure face of the blade remains fully wetted and the suction side is fully ventilated or dry. This is an analogous
31、operating regime to the supercavitating propeller, but in this case the blade surface suction pressure is at atmospheric conditions and not the vapour pressure of water. 回顾了螺旋桨的早期发展。在单块式螺旋桨普遍使用的今天，但那些叶片来自不同地方的内置式螺旋桨已经很少被人所用了。这并非总是如此，因为在上个世纪内置式螺旋桨相当的普遍，部分原因是无法实现那是的大型铸件保证好的质量和确定正确的螺距有困难度，在这两个方面内置式螺旋桨有
32、着明显的优势。然而，内置式螺旋桨的毂比相对应的固定螺距大，这可能会导致在某些情况下，存在叶根在部分地区空间化问题的难度。单块式螺旋桨的设计规模和类型覆盖广泛，从小功率艇用的几公斤重的螺旋桨到为大集装箱船设计的重130吨的，同时要求有着更多金属的铸造来生产铸件。数据6.1显示了现在正在使用的大量的各种模式的固定螺旋桨。这些类型的范围从一个安装大的四桨叶螺旋桨的一艘散货船，并且看到的轮廓是对比从一个人站在码头底部来看的，通过大侧斜螺旋桨的商用和海军的应用，到小型高速巡逻艇和半浸式螺旋桨。正如所料，生产的材料从设计和尺寸有很大的变化。对于直径超过300mm的大型螺旋桨，非有色金属占主导地位：高强度的
33、黄铜锰合金和镍铝青铜合金材料是最被看好的材料。然而，不锈钢也一直在被有限的使用。铸铁，曾经是生产螺旋桨的最喜欢的备用材料，现在已几乎很少使用了。另外，对于小型螺旋桨，经常使用的生产材料，如聚合物，铝，尼龙，和最近使用的碳纤维复合材料。对于固定螺旋桨桨叶数量的选择，尽管考虑了叶片根部到轮毂间的叶片间隙，在很大程度上它是一个独立的变量，而且通常选择给不匹配的船体，船楼建筑和容易引起关注的机械振动频率。此外，叶片数也是一个用来控制不合理的空化特性的非常有用的参数。叶片数一般为2至7，尽管在某些海军的应用，其中辐射噪声的考虑变得重要，叶片数量比那些被用来研究和解决各种推进问题的东西重要得多。对于商船，
34、然而，四、五、六的叶片数普遍存在，虽然很多拖船和渔船经常使用的三叶片设计。至于小工作或娱乐动力船通常使用两到三叶螺旋桨。早期的螺旋桨设计理念都集中在螺旋桨的效率优化方面。虽然在今天这方面同样重要，且在某方面与节约能源有关系，它已经承担了更大的重要性，而且对设计其他方面的限制已经出现。这是在回应要求减少螺旋桨的振动激励和辐射噪声。这一先进的发面已经理所当然的多年来成为了军舰和鱼雷设计师最关注的；然而，尽管通常在一个较为宽松的形式下，但把这些制约引进商船实践设计的压力近年来是越来越大了。这是轴功率增加;后甲板室的使用，货物的运载能力最大化所引起的，其中规定对船体的型线限制;船舶结构失效和国际立法。
35、对于多数排水超过100吨的船只，是有可能设计这样的螺旋桨，它的桨叶可以控制空化作用关于材料腐蚀的影响，它能削弱水动力性能，而且它能成为振动激励源。在后一种情况下，我们需要记住的是有极少数螺旋桨能够免除空化作用，因为大多数空泡在螺旋桨中的某个位置：当潜艇螺旋桨在水深的地方工作时，拖曳的阵列护卫舰和部分负荷工况下运行时的考察船的螺旋桨是明显的例外，因为这些推进器通常设计成亚空泡，以满足严格的噪声排放标准，以用他们的设备减少检测或干扰。此外，螺旋桨在水深处工作时，如在一艘潜艇中，在适当的情况下必须考虑船舶的推力块附加的静水压力诱导推力也会作出反应。对于小型、高速船的螺旋桨推进和转速都很高、浸泡低。达
36、到这样一个目的，不可能控制空泡效应在螺旋桨设计可接受的约束范围内。为克服这个问题，全部或部分叶片部分允许充分抽空，使空泡沿叶片背部发展，延伸到叶片尾部边缘，并且收缩到叶片的后面在滑流中。这种螺旋桨被称为超空泡螺旋桨推进器，并且这种螺旋桨经常发现用在高速海军舰艇和游艇中。数表6.2c说明了这种设计理念与非空泡和部分空泡螺旋桨相比之下的部分差别。当设计条件决定一个特定的水动力载荷和一个非常敏感空化环境一起时，代表一个低的空泡数，有时候甚至超空泡螺旋桨时将运转的不那么令人满意：例如，如果螺旋桨的尖端浸泡变得如此之小以至于螺旋桨倾向于吸取表面的空气，即所谓的通风，以及一些方便的路径，如沿船体表面或向下
37、一轴支架。最终，如果浸泡降低了很多的设计或运作上设下的限制那么螺旋桨将立即出现破裂面。虽然这种情况在货船为众人所知，当压载作业条件在这种情况下可能导致某些缺陷，从材料疲劳观点到振动，表面碎裂的概念可能是推进较小的的高速船舶的有效手段。这种螺旋桨被称作为表面穿孔螺旋桨，而且它们的设计浸泡-从自由面到轴中心线测量-可以减少到零，也就是说，螺旋桨在工作的时候必须有一半要露在水面以上才好。在这些部分浸泡的条件下，螺旋桨的桨叶一般都设计成这样工作使得叶片的压力表面仍然保持充分浸润和吸力面保持通风或者干燥。这是一个类似于超空泡螺旋桨的工作模式，但在这种情况下，叶片表面的吸入压力为大气压力条件，而不是水蒸汽
38、压力。6.2.2 Ducted propellersDucted propellers, as their name implies, generally comprise two principal components: the first is an annular duct having an aerofoil cross section which may be either of uniform shape around the duct and, therefore, symmetric with respect to the shaft centre line, or have
39、 certain asymmetric features to accommodate the wake field flow variations. The second component, the propeller, is a special case of a non-ducted propeller in which the design of the blades has been modified to take account of the flow interactions caused by the presence of the duct in its flow fie
40、ld. The propeller for these units can be either of the fixed or controllable pitch type and in some special applications, such as torpedo propulsion, may be a contra-rotating pair. Ducted propellers, sometimes referred to as Kort nozzles by way of recognition of the Kort Propulsion Companys initial
41、patents and long association with this type of propeller, have found application for many years where high thrust at low speed is required; typically in towing and trawling situations. In such cases, the duct generally contributes some 50% of the propulsors total thrust at zero ship speed, termed th
42、e bollard pull condition. However, this relative contribution of the duct falls to more modest amounts with increasing ship speed and it is also possible for a duct to give a negative contribution to the propulsor thrust at high advance speeds, see Section 5.3.4.3. This latter situation would nevert
43、helessbe a most unusual design condition to encounter.There are nominally two principal types of duct form, the accelerating and decelerating duct, and these are shown in Figure 6.3(a), (b), (c) and (d) , respectively. The underlying reason for this somewhat artificial designation can be appreciated
44、, in global terms by considering their general form in relation to the continuity equation of fluid mechanics. This can be expressed for incompressible flow in a closed conduit between two stations a-a and b-b。By undertaking a detailed hydrodynamic analysis it is possible to design complex duct form
45、s intended for specific application and duties. Indeed, attempts at producing non-symmetric duct forms to suit varying wake field conditions have been made which result in a duct with both varying aerofoil section shape and incidence, relative to the shaft centre line, around its circumference. Howe
46、ver, with duct forms it must be appreciated that the hydrodynamic desirability for a particular form must be balanced against the practical manufacturing problem of producing the desired shape if an economic, structurally sound and competitive duct is to result. This tenet is firmly underlined by ap
47、preciating that ducts have been produced for a range of propeller diameters from 0.5 m or less up to around 8.0 m. For these larger sizes, fabrication problems can be difficult, not least in maintaining the circularity of the duct and providing reasonable engineering clearances between the blade tip
48、s and the duct: recognizing that from the hydrodynamic viewpoint that the clearance should be as small as possible.When the control of cavitation and more particularly the noise resulting from cavitation is of importance, use can be made of the decelerating duct form. A duct form of this type, Figur
49、e 6.3(d), effectively improves the local cavitation conditions by slowing the water before passing through the propeller. Most applications of this duct form are found in naval situations, for example, with submarines and torpedoes. Nevertheless, some specialist research ships also have needs which can be partiall