第12章 推进与舵机外文翻译资料

Chapter 12 propulsion and steering gear

第12章 推进与舵机

1. Ship resistance

1.航行阻力

The power required to move a ship through the water depends on the propulsive efficiency and the total resistance of the ship. Resistance is a complex function of displacement, shape and speed.

船舶通过水面移动所需的动力取决于推进效率和船舶的总阻力。而阻力是位移、形状和速度的复杂函数。

The various components of resistance can be divided as follows:

阻力有以下组成部分：

1. Frictional resistance

The friction between the water and the ship#39;s hull is the resistance. The water in the boundary layer is accelerated by the ship#39;s speed, dragged by the molecular friction. This boundary layer is thicker, and the resistance higher when the shell is fouled. Resistance is least directly after delivery of the ship. During the ship#39;s lifetime, the roughness of the hull normally increases, due to paint-layers covering older paint-layers, damage, corrosion, etc. This results in a gradual drop in speed and efficiency.

1. 摩擦阻力

水与船体之间的摩擦产生阻力。边界层中的水是由船的速度而加速，被分子摩擦牵引。当船体受到污染时，边界层越厚，所受阻力越大。刚交付的船舶阻力最小。由于油漆层覆盖了较旧的油漆层以及损坏、腐蚀等，在船舶使用期间，船体的粗糙度通常会增加。这便造成了船舶速度和效率逐渐下降。

1. Pressure (form) resistance

The ship#39;s momentum pushes the water aside at the bow and as a result, the pressure of the water increases. This increase in pressure also occurs aft. The pressure will drop where the boundary layer is released.

b. 压力(形状)阻力

船的动量把船头的水推到一边，导致水的压力增加。压力的增加也发生在船尾。边界层被释放的地方，压力会下降。

1. Wave resistance

This is a result of wave systems along the hull that originate from the differences in pressure.

On certain ships the use of a bulb at the bow can significantly decrease the wave-making resistance.

The bulb generates its own wave system, which is designed to interfere negatively with the ship#39;s wave system. The two wave systems then neutralize each other.

c. 兴波阻力

这是由于船体上的波动系统产生压力上的差异。某些特定船只在船头使用球鼻艏可以显著降低兴波阻力。

球鼻艏产生它自己的波系统，它被设计成对船的波浪系统产生负面干扰。然后这两个波系统相互中和。

d.Additional resistance in waves

This type of resistance is caused by the pitching, heaving and rolling of the ship.

1. 波浪附加阻力

这种阻力是由船舶的俯仰、起伏和横摇引起的

1. Air resistance

This depends on the vertical area above the waterline, which varies with the draft. Resistance components as mentioned in d. and e. are variable, depending on wave and wind direction.

N.B.With regard to frictional resistance, the newest hull paint, so-called non-stick paint, is silicon-based, which does not allow fouling of the paint and keeps the frictional resistance constant throughout the lifetime of the paint. This paint can also be applied on the propeller, resulting in a smooth hull and propeller, in this way keeping hull efficiency constant. Speed does not drop over time and the fuel consumption of the engine remains constant. It is, however, a very expensive system, only paying off large, fast ships.

e. 空气阻力

这取决于吃水线上方的垂直区域，水线随着吃水的不同而变化。

d和e所提到的阻力组分都是可变的，它们取决于波浪和风向。

注意，在摩擦阻力方面，最新的船体漆，即所谓的不粘漆，这是一种硅基漆，在这种油漆的正常使用期间内，它不允许油漆沾污，并保持摩擦阻力不变。这种油漆也可以涂在螺旋桨上，从而使船体和螺旋桨光滑，从而保持船体效率不变。速度不会随着时间的推移而下降，发动机的油耗也保持不变。然而，这是一个非常昂贵的系统，只会给大型、快速的船只带来利润。

2. Propulsion

2.推进

2.1 Propeller

2.1 螺旋桨

In order for a ship to obtain a certain constant speed, a force needs to be exerted on the ship. The magnitude of this force depends on the ship#39;s resistance applicable to that particular speed. If the ship is moving through the water at a constant speed the force exerted on the ship equals the resistance of the ship.

The force that moves the ship can come from an outside source like a towing line or the wind, but generally the force is generated by a power source (engine) on the ship itself. The propulsion system usually consists of an engine or turbine, reduction gearing and if applicable, a propeller shaft and propeller.

The efficiency of a propeller holds an important place in the design of the propulsion because its efficiency and the ship#39;s fuel consumption are directly related.

为了使船舶获得恒定的速度，需要在船舶上施加一定的力。这种力的大小取决于有特定速度的船舶阻力。如果船舶以恒定的速度通过水面，施加在船舶上的力等于船舶所受的阻力。

移动船舶的力可以来自像拖曳线或风这样的外部来源，但通常这种力是由船舶本身的动力源(发动机)产生的。推进系统通常由发动机或涡轮机、减速传动装置以及适用的螺旋桨轴和螺旋桨组成。

螺旋桨的效率直接关系到船舶的燃油消耗，因而在推进设计中占有重要的地位。

Looking at oil tankers, bulk carriers and container ships it can be clearly seen that the bulb prevents an increase in pressure near the bow. The improved streamline of the ship#39;s underwater body reduces a wave system around the ship. In suppliers and hopper suction dredgers, there is a large wave system present around the ship.

If the rate of flow of water (or air) is higher, then the pressure will be lower compared to the pressure in parts of the water where the rate of flow is lower. Therefore, in waves, water in a trough has a higher speed than water in a wave top. (see chapter 4 “design”and Bernoulli#39;s law).

观察油轮、散货船和集装箱船，可以清楚地看到球鼻艏防止船头附近的压力增加。改进船舶的水下船体的流线型减少了船周的波浪系统。

水(或空气)的流速较高部分的压力低于流速较低的部分的压力。因此，在波浪中，水在波谷的速度比在波峰的速度更高。

（见第四章 设计和伯努利定律）

Efficiency depends on the flow field of the propeller, which depends on:

- the shape of the ship#39;s underwater body - the power delivered to the propeller

- the number of blades

- rotations per minute

- the maximum possible propeller diameter

- the blade surface area and smoothness of the blade

- the ship#39;s speed

In general can be stated that the highest efficiency in propulsion is achieved w

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