The diesel engine was, like many things, born of necessity. The main engine types of the day—hot bulb oil, steam, coal gas, and gasoline—were not so thermally efficient or ideal for doing heavy-duty work like driving large-scale electrical generators. But how did the diesel engine come about? Settle in and watch the 1952 documentary “The Diesel Story“, produced by Shell Oil.
The diesel engine is founded on the principle of internal combustion. Throughout the Industrial Age, technology was developing at breakneck pace. While steam power was a great boon to many burgeoning industries, engineers wanted to get away from using boilers. The atmospheric gas engine fit the bill, but it simply wasn’t powerful enough to replace the steam engine.
By 1877, [Nikolaus Otto] had completed work on his coal gas engine built on four-stroke theory. This was the first really useful internal combustion engine and the precursor of modern four-stroke engines. It was eventually adapted for transportation with gasoline fuel. In 1890, the hot bulb oil engine was developed under the name Hornsby-Akroyd and primarily used in stationary power plants. Their flywheels had to be started manually, but once the engine was going, the bulb that drove combustion required no further heating.
By the turn of the 19th century, many engines of the four main types were humming along. But as we said, none were very thermally efficient. As respected as the steam engine was, the Shell Oil company will have you know that its thermal efficiency is the lowest of the low at 6%. Surely there must be a better way of doing work.
[Rudolph Diesel] was well determined to make it happen, and he worked under a set of four personal certainties: get away from steam, engineer combustion to occur inside the cylinder, use pure air, and ensure that air is highly compressed. With the fire piston’s basic design in mind, he went to work creating a combustion engine using ordinary air.
His first prototype didn’t work very well because of the pressure required, so he added an air pump to forcefully push the fuel into the cylinder. This is known as air-blast injection. By 1897, he had perfected his combustion method to the tune of 27% thermal efficiency.
Soon, diesel engines were being manufactured in many countries for use in electrical generation. Engineers realized their potential to do work at sea, and in 1912, the first diesel ship set sail from Copenhagen to Bangkok. The surge in seagoing diesel engines was the result of adapting the design for a two-stroke cycle, which provides more power.
Not all applications call for high power, however. Submarines, trucks, and tractors need high-speed engines, but the air-blast injection method proved inefficient. It was replaced by the jerk type pump, which sends an exact amount of fuel to the cylinder in a high pressure mist. Combustion was revolutionized once again.
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