History of the Diesel Engine

For most of us, living means working. So to get the most out of life, men look for a way of making machines do some of their work. Wind was one answer, but it was not always reliable. They turned to another form of energy. And discovering that heat could drive machines, they opened up a great new reservoir of reliable power. New industries were born and new towns built to serve them. The arrival of the heat engine changed the whole way of life for people in many parts of the world. The first practical heat engines were driven by steam. Fed on coal and water, they were the foundation of the new industrial age. Day and night they worked, pumping, driving, turning, consuming each day thousands of tons of coal. During the 19th century, coal was by far the best fuel available. It also yielded a valuable byproduct, gas for lighting and heating. But this gas was now used for another purpose, as a source of power in the so-called atmospheric gas engine patented by Otto and Langen in 1860. For years, men had been trying to do away with boilers and to burn fuel inside the cylinder. Now, coal gas made this possible. But these early internal combustion engines were temperamental, and their power output was too limited to challenge the power of the steam engine. It was not until 1877, when Otto adopted the principles of the four-stroke cycle theory of the French scientist, Beau de Rochas, that a really practical internal combustion engine was built. The Otto Silent Gas Engine, as it was known, was the forerunner of all modern four-stroke engines. First stroke: induction, a mixture of gas and air is drawn into the cylinder. Second stroke: compression. Third stroke: power. The mixture is ignited and expands, driving the piston outwards. Fourth stroke: exhaust. With the discovery of petroleum, a new source of power was born and the internal combustion engine developed rapidly, similar in principle to the gas engine, the gasoline engine had the advantage of utilising an easy to handle fuel. Thus, it was ideal for use in the motor car. In contrast to the gasoline engine, another type of internal combustion engine was built in 1890. Designed by Akroyd Stuart, this machine was used for driving stationary power plants. It ran on a heavier petroleum fuel and was known as the hot bulb oil engine. The engine comprises a vaporiser, or hot bulb, from which the hot gases pass through a narrow passage into the working cylinder. In the cylinder is a piston joined by a connecting rod to the crankshaft and a heavy flywheel. Before starting, the vaporiser is heated by a blow lamp to high temperature. The flywheel is then turned over by hand. Pure air is sucked into the working cylinder, and the oil fuel is sprayed into the hot bulb. During the second stroke, air and vaporised fuel are mixed together and compressed. The high temperature in the vaporiser causes combustion, and the piston is forced outward by the expanding gases. Finally, the burnt gases are expelled from the cylinder. Once the engine was running, the heat retained in the hot bulb was enough to ensure combustion, and the blow lamp was no longer necessary. These simple engines could run for long periods at a constant speed, and they gained a wide reputation for reliability. The 19th century saw enormous progress in the development of heat engines of all kinds, and towards its close, there were four main types in general use-- The oil engine with hot bulb vaporiser, the steam engine, which was still considered supreme for a wide variety of uses, the gas engine, for stationary power plants, and the rapidly improving gasoline engine. All these engines worked on the same basic principle of turning heat into work. But in each case, the amount of heat turned into work was small. The efficiency was low-- 6% for the average steam engine, 10% for the oil engine, 17% for the gas engine, and 12% for the gasoline engine. Looking at these facts, Rudolph Diesel was certain that it should be possible to build an engine with a very much higher efficiency. From the start, he was convinced of four things. He must get away from the steam engine entirely. Combustion must take place inside the cylinder. Air, not steam, must be the working medium. And finally, the air must be highly compressed so as to permit the greatest possible expansion. You remember the pneumatic match, or fire piston. A small cylinder usually made of wood or glass into which a closely fitting piston or a plunger could be inserted. The head of the piston was recessed so as to hold a piece of dry tinder. When the air in the cylinder was highly compressed, it became so hot as to cause the tinder to ignite. The fire piston gave a clue to a practical means of securing combustion inside the cylinder. Compression, ignition. Diesel adapted this principle to the internal combustion engine and described the cycle for the first time in 1892. A downward stroke of the piston, pure air is sucked into the cylinder. The air is then compressed to the point where it reaches the temperature necessary for combustion. Fuel is introduced into the compressed air. Owing to the high temperature, it takes fire and produces heat. Which is turned into work. During the fourth stroke, the spent gases are forced out of the cylinder. The first experimental engine was built at Augsburg in Germany during 1893. Most people were convinced that no machine would work at the high pressures which Diesel insisted were necessary for combustion and essential for high thermal efficiency. [SPEAKING IN GERMAN] [MACHINE WHIRRING] This engine never ran under its own power. One of the main problems facing Diesel arose from the high pressures inside the cylinder. An exact quantity of oil fuel had to be sprayed finely and accurately through a dense wedge of compressed air. It was found that the fuel pump by itself could not do the job effectively. So an air pump was added which could blow the fuel into the combustion chamber. The principle was similar to that of a perfume atomizer. The method was known as air blast injection. By 1894, a completely new and redesigned engine had been built, and preparations were complete for the first trial run. [MACHINE WORKING] [SPEAKING IN GERMAN] [MACHINE WORKING] Compression ignition was a practical way of securing combustion, and an engine could be made to work on this cycle. By 1897, the first reliable engine had completed its test. Limitations in engineering methods had made some modifications necessary. Nevertheless, the engine had an efficiency of 27%, far higher than any other engine of the day. [MACHINE WORKING] [MUSIC] By the turn of the century, the Diesel engine was in regular production. The first models built under license were large single cylinder units with a maximum speed of less than 200 revolutions per minute. Manufacturers in various countries made some modifications to the original design, and a few horizontal engines were built. These were reminiscent of Akroyd Stuart's earlier engine, but with much higher compression and no hot bulb. The diesel was ideal for driving electric generators. With the rapid expansion of electrical power, there was a demand for larger engines with more than one cylinder. With the development of more power, engineers soon realised that the diesel could be adapted for marine work. By 1912, the first ocean-going diesel ship had been built. [MUSIC] [CHEERING] The Selandia of 7,400 tons was built at Copenhagen by Burmeister and Wain. Her maiden voyage to Bangkok created a sensation in the marine world and marked the beginning of a close association between the diesel engine and the sea. Within a few years, hundreds of new vessels fitted with these engines were to be launched from shipyards all over the world. Today, one ship in every four is diesel driven. The success of the marine diesel was due partly to the adoption of the two-stroke cycle for large high-power engines. During the first stroke, the air inside the cylinder is highly compressed. Injection then takes place. Toward the end of the power stroke, the burnt gases surge from the cylinder and are replaced by the incoming charge of pure air. The first stroke is the same as the compression stroke in the four-cycle engine. The second stroke combines power, exhaust, and induction, and completes the cycle. The advantage of the two-stroke cycle is that it allows a working stroke for each revolution and therefore delivers more power for a given engine size. But more power was not the only requisite. There was a demand for smaller and faster engines for certain purposes. Comparatively light engines for submarines had been built before 1920. But the air blast injection system was cumbersome, inefficient, and unsuited to high speeds. There seemed to be a limit to progress in this direction. During the 20s, however, a new system of airless injection was perfected, and the air blast method was superseded. The so-called jerk-type pump meters an exact quantity of fuel which is delivered at high pressure and broken into a fine spray at the injector nozzle. The injection pulse is synchronised with the engine speed. The development of precision airless injection was a landmark in diesel history. Here, at last, was the opportunity to build an engine which would be light as well as powerful. 10 years of hard work and patient research were necessary before the high-speed engine could go into regular production. These engines are more sensitive than the low-speed types, and a great deal of work on combustion problems and the development of new fuels and lubricants was necessary. Then there were other aspects. For example, trucks, tractors, and small boats fitted with high-speed diesel engines may have to work in regions with temperature well below zero. Practical tests of starting and running at these low temperatures were carried out in special laboratories. This is only one example of a vast field of research and experiments which lies behind the production of the modern diesel. Today, engines of all types and sizes are in large-scale production throughout the world. Medium-speed engines for express trains, small high-speed engines for trucks and buses, diesel for tractors and bulldozers, and agricultural machines, miniature engines for model cars and model aircraft, huge double-acting types for generating electrical power and for driving ships, two-stroke and four-stroke engines for a hundred uses. The diesel has always had a reputation for efficiency and reliability. Like every other machine, it owes much to the past, to Akroyd Stuart, whose early work laid the foundation for the solid injection engine, to the pioneers who discovered how to turn heat into work, to the scientists who learned about the nature of heat, to the engineers who have adapted their theories to practice, and to the petroleum technologists who have constantly developed new and better fuels and lubricants. It is through their work and knowledge that we have the modern diesel, the most efficient and most versatile of all heat engines.