燃油喷射外文翻译资料

英文原文

译文

Chapter 8 Fuel injection

第八章 燃油喷射

The emphasis in this chapter is on medium speed engines with camshaft actuated individual jerk pumps for each cylinder. Higher speed engines are also covered, including those which use camshaft pumps (or block pumps): those in which all the jerk pump elements are grouped into one or more complete units, each equipped with a common camshaft. This section does not apply (except in a general way) to low speed two-stroke engines whose systems are described later under individual makes.

本章的重点是凸轮轴驱动的每个缸独立的高压燃油喷射泵的中速发动机。同时包括高速发动机，还有那些使用凸轮轴泵(或梭心转子泵):那些所有的燃油喷射泵元件被组合成一个或多个完整的单位，每个配备一个共同的凸轮轴。本节不适用于低速二冲程发动机(一般情况下除外)，其系统稍后将在单独制造下介绍。

INJECTION AND COMBUSTION

喷油及燃烧过程

The essence of a diesel engine is the introduction of finely atomized fuel into the air compressed in the cylinder during the pistonrsquo;s inward stroke. It is, of course, the heat generated by this compression, which is normally nearly adiabatic, that is crucial in achieving ignition. Although the pressure in the cylinder at this point is likely to be anything up to 200 bar, the fuel pressure at the atomizer will be of the order of 1300–1800 bar.

柴油机的要点是在活塞向内行程时，将雾化良好的燃料引入气缸内压缩的空气中。当然，由压缩过程产生的热量，通常是接近绝热的，这对实现点火十分重要。虽然此时气缸内的压力可能高达200 bar，但雾化器处的燃油压力大概有1300-1800bar。

There is a body of evidence to suggest that high injection pressure at full load confers advantages in terms of fuel economy, and also in the ability to digest inferior fuel. Most modern medium speed engines attain 1200–1800 bar in the injection high-pressure pipe. Some recent engine designs achieve as much as 2300 bar when pumping heavy fuel. For reasons of available technology, the earliest diesel engines had to use compressed air to achieve atomization of the fuel as it entered the cylinder (air blast injection), and while airless (or solid) injection delivered a significant reduction in parasitic loads it also presented considerable problems in the need for high precision manufacture, and the containment of very high and complex stresses.

有大量的证据表明，满负荷时的高喷射压力在燃油经济性方面具有优势，而且在消化劣质燃油方面也有优势。大多数现代中速发动机在高压喷射管中压力可达到1200-1800bar。一些最新的发动机设计实现了在泵入重质燃料时压力达到2300bar。由于现有技术的原因，最早的柴油发动机当燃料进入气缸时(鼓风注入)，不得不使用压缩空气来实现燃料雾化,当没有空气（或固体）注入时在寄生负载上会产生显著的下降。它也出现了相当大的问题，例如需要高精度制造，并且能够承受非常高且复杂的压力。

The very high standard of reliability and lifetime now attained by modern fuel injection systems, notwithstanding their basic simplicity, reflects a considerable achievement in Ramp;D by fuel injection equipment manufacturers.

现代燃油喷射系统在其可靠性和寿命上拥有非常高的标准，尽管它们的要素很简单，这反映出燃油喷射设备制造商在研发方面取得了相当大的成就。

In the early days of airless injection many ingenious varieties of combustion chamber were used, sometimes mainly to reduce noise or smoke, or to ease starting; but often in part to reduce, or to use modest, injection and combustion pressures. A growing emphasis on economy and specific output, coupled with materials development and advances in calculation methods allowing greater loads to be carried safely, has left the direct injection principle dominant in modern medium speed and high speed engine practice.

在无空气喷射的早期，使用了许多巧妙的燃烧室，有时主要是为了减少噪音或烟雾，或为了方便启动;但通常部分是为了降低或使用适当的喷射和燃烧压力。随着对经济和特定输出的日益重视，再加上材料的发展和计算方法的进步，使得更大的负荷可以安全地进行，使得直喷原理在现代中速和高速发动机实践中占据主导地位。

Direct injection is what it says it is: the fuel is delivered directly into a single combustion chamber formed in the cylinder space (Figure 8.1), atomization being achieved as the fuel issues from small drillings in the nozzle tip.

直喷正如它字面意思所说:燃料被直接送入到气缸里面的单独燃烧室(图8.1)，当燃料从喷嘴尖端的小钻出时，实现燃料雾化。

For complete combustion of the fuel to take place, every droplet of fuel must be exposed to the correct proportion of air to achieve complete oxidation, or to an excess of air. In the direct injection engine the fuel/air mixing is achieved by the energy in the fuel spray propelling the droplets into the hot, dense air. Additional mixing may be achieved by the orderly movement of the air in the combustion chamber, which is called lsquo;air swirlrsquo;. Naturally aspirated engines usually have a degree of swirl and an injection pressure of around 800 bar. Highly turbocharged engines with four-valve heads have virtually no swirl, but have an injection pressure of 1200–1800 bar to provide the mixing energy. Where indirect injection is exploited, some high speed engines retain a pre-chamber in the cylinder head into which fuel is injected as a relatively coarse spray at low pressure, sometimes using a single hole. Combustion is initiated in the pre-chamber, the burning gases issuing through the throat of the chamber to act on the piston (Figure 8.2).

为了实现燃料的完全燃烧，每一滴燃料都必须暴露在正确比例的空气中以实现完全氧化，或者暴露在过量的空气中。在直喷式发动机中，燃料/空气混合是通过燃料喷雾中的能量将液滴推进到热的稠密空气中来实现的。额外的混合可以通过燃烧室中空气的有序运动来实现，这被称为空气涡流。自然吸气式发动机通常有一定程度的涡流和800bar左右的喷射压力。带有四个气门的高涡轮增压发动机几乎没有涡流，但是有1200-1800bar的喷射压力来提供混合的能量。在采用间接喷射的情况下，一些高速发动机在气缸盖上保留一个预燃室，燃料以相对粗糙的低压喷雾注入，有时使用单孔。燃烧在预燃室中开始，燃烧气体通过预燃室的喉部喷出，作用于活塞(图8.2)。

Fuel/air mixing is achieved by a very high air velocity in the chamber, the air movement scouring the walls of the chamber and promoting good heat transfer. Thus the wall can be very hot-requiring heat resistant materials—but it can also absorb too much heat from the air in the initial compression strokes during starting and prevent ignition. It is these heat losses that lead to poor starting and in

剩余内容已隐藏，支付完成后下载完整资料

资料编号：[238276]，资料为PDF文档或Word文档，PDF文档可免费转换为Word