Marine engines and auxiliary machinery.doc
《Marine engines and auxiliary machinery.doc》由会员分享,可在线阅读,更多相关《Marine engines and auxiliary machinery.doc(18页珍藏版)》请在三一文库上搜索。
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
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Marine engines and auxiliary machinery
链接地址:https://www.31doc.com/p-2375265.html