In this blog post, we will look at how Rudolf Diesel revolutionized the diesel engine by utilizing high compression ratios and fuel characteristics.
It was in 1892 that the German inventor Rudolf Diesel came up with the idea for a new engine and patented it. At the time, Europe was in the midst of a rapid mechanization following the Industrial Revolution and was in need of a more efficient and economical power source. The efficiency of the gasoline engine invented by Nikolaus August Otto in 1876 was not very high, and the efficiency of the widely used steam engine was only 10%, and it had the disadvantage of being expensive to operate. These technical limitations were constraining the development of the industry, and the need for a better energy conversion system was growing.
Rudolf Diesel’s goal was to create a highly efficient engine, and his idea was to burn fuel at a much higher compression ratio. His research was not just about improving the engine, but about reestablishing the fundamental principles of energy conversion. Generally, a gasoline engine first mixes air and fuel in a carburetor, then draws the mixed gas into the cylinder and compresses it, and finally sparks a spark plug to generate power. The problem with this process is that the degree of compression is limited. If too much pressure is applied to the vaporized gasoline, it will ignite spontaneously, which is what causes the engine to “knock.” Knocking is an abnormal explosion that occurs in the cylinder, which can seriously impair the performance and durability of the engine.
At this point, Rudolf Diesel felt the need to make major improvements to the existing engine structure. To increase the efficiency of the engine, he devised a method of first strongly compressing the air and then injecting fuel to ignite it naturally. The fact that air becomes hot when compressed was widely known at the time, but the effective application of this to engines was innovative. The basic principle of a diesel engine is to inhale only air into the cylinder, compress it strongly with a piston, and then spray fuel into the compressed air to ignite it on its own. Therefore, diesel engines do not require spark plugs, but are equipped with fuel injectors. Also, since air and fuel are not mixed during the compression process, diesel engines have a compression ratio of about 25:1, which is much higher than that of gasoline engines, which have a compression ratio of up to 12:1. A high compression ratio means a high thermal efficiency, which allows diesel engines to produce more energy with less fuel.
The invention of the diesel engine did not fully realize its potential in the early days. The characteristics of the fuel used are also different. Diesel is much heavier and more viscous than gasoline, and it evaporates more slowly. This is because diesel contains many more carbon atoms connected in long chains than gasoline. In general, gasoline is a mixture of hydrocarbons with 5 to 10 carbons, while diesel is a mixture of hydrocarbons with 16 to 20 carbons. When high-temperature heat is applied to hydrocarbons with many connected carbons, they are decomposed into hydrocarbons with fewer carbons. On the other hand, diesel has a higher energy density than gasoline. One gallon of diesel has about 155 million joules of energy, while gasoline has 132 million joules. These fuel characteristics, combined with the high efficiency of diesel engines, result in diesel engines having better fuel economy than gasoline engines.
Rudolf Diesel thought that diesel engines should be small and economical, but in his lifetime, only large and heavy engines were made. However, his invention opened up new possibilities, and as they became smaller and lighter, they developed into a technology that could be applied to various fields. After that, automakers began to focus on the strengths of diesel engines and apply them to commercial and passenger vehicles. By the mid-20th century, diesel engines were widely used in trucks, buses, and industrial machinery, and diesel technology continued to improve, evolving into more efficient and environmentally friendly engines.
The durability and economic efficiency of diesel engines have been particularly popular in commercial vehicles, which has contributed to the growth of the large-scale logistics industry. In addition, technological advancements in diesel engines are being used in power plants, ships, and trains, and have become an important source of power for modern industries. Diesel engines are more robust and less prone to breakdown than gasoline engines in principle, and they are not sensitive to the quality of fuel and are more economical in terms of fuel consumption, so they have firmly established themselves as the engine of choice for cars today. The issue of diesel engine emissions of particulates, which environmentalists are concerned about, is also gradually being overcome as filter technology improves. The development of alternative fuels such as biodiesel has also opened up the possibility of further reducing the environmental impact of diesel engines.
The development of diesel engines has had a significant impact on society and the economy as a whole, going beyond simple technological innovation. The legacy left by Rudolf Diesel is not just an invention of an era, but also an important lesson in sustainable energy use and efficient resource utilization.
