The diesel engine was first developed by the German engineer Rudolf Diesel, who tried to improve on the efficiency of the steam engine and of the gasoline engine, which was invented shortly before (see Diesel, Rudolf). The modern diesel engine is still very similar to the one described by Diesel in his initial 1892 patent and his 1893 description. The first diesel engine for commercial service was built in the United States and installed in St. Louis, Mo., by a brewing company in 1898. The design of the engine was based on an engine exhibited in Germany. Within a few years thousands of diesel engines were in service. Diesel engines typically range in size from 10 to 1,500 horsepower. They are used widely in buses and trucks where fuel efficiency is important. They drive tractors, power shovels, air compressors, pumps, hoists and winches, air-conditioning and refrigeration equipment, and many other industrial machines. Slow-speed diesel engines are very reliable and are used for both electric power production and for marine applications. Until the development of nuclear power, all submarines were diesel-engine powered. Nearly all railroad locomotives now use a diesel-electric drive in which the engine is coupled to an electric generator that feeds electric power to motors that drive the wheels. In recent years the agriculture of China has been revolutionized by replacing farm draft animals with locally built, 12-horsepower, single-cylinder diesel tractors on a wheelbarrow-like support.

Diesel engines use a conventional cylinder and piston arrangement. The cylinders may be arranged vertically in line, in two banks forming a V, or with the cylinders radiating from the center like spokes in a wheel. (See also Internal-Combustion Engine; Automobile, “Power Plant.”) In the widely used four-stroke engine, the piston draws air into the cylinder during the first stroke. During the second stroke the air is compressed in the cylinder to about one fifteenth of its original volume. Engineers call this a 15:1, or 15 to 1, compression ratio. At the end of compression the air pressure is more than 40 times atmospheric pressure, and the air temperature exceeds 1,000° F (540° C). At this point a predetermined amount of finely atomized fuel, or fuel in the form of very small droplets, is injected into the cylinder through the fuel pump. The very high air temperature in the cylinder causes the fuel to burn very rapidly without the use of a spark plug. The high-temperature, combusted gas pushes the piston to the bottom of the cylinder, delivering power to the crankshaft during the third stroke. During the fourth stroke, the low-pressure, combusted gases are pushed through the exhaust port. Thus only one stroke in four delivers power. In two-stroke engines, which are generally smaller than four-stroke diesel engines, air is admitted just before compression begins, and the burned gases are exhausted near the end of the power stroke. The two-stroke engine therefore delivers power once every second stroke. A two-stroke engine is generally less efficient than a four-stroke engine but can develop greater power for a given engine size and speed. Two-stroke engines are used where small one- or two-cylinder engines are needed and where the intermittent action of a four-stroke engine would require too large a flywheel to keep the engine running at nearly constant speed. The heart of the diesel engine is its fuel-injection system. Each cylinder has a separate fuel pump that can develop pressures in excess of a thousand pounds per square inch (70 kilograms per square centimeter) to force a measured amount of oil through very small nozzle holes into the cylinder. The high pressures coupled with the small holes cause the atomization of the fuel. The amount of fuel injected at every stroke must be varied to meet the power requirements imposed on the engine. Various types of oils can be used for diesel engines. The most commonly used oil, usually called diesel fuel, is similar to that used in home heating systems. The high pressures developed during compression demand large starting motors for automotive diesels. Large, nonautomotive diesel engines are usually started with a supply of compressed air from an auxiliary compressor and air storage tank. For a cold small diesel engine, an in-cylinder heat source called a glow plug is required during start-up to assist the initial combustion. During very cold weather longer warm-up periods are needed, and care must also be taken that the fuel is able to flow readily from the tank to the engine. Diesel engines are therefore not recommended for automotive use in very cold climates unless the fuel can be preheated. The performance of large diesel engines can be improved by the addition of a supercharger, which precompresses the air before it is admitted to the cylinder, thereby increasing the amount of air and fuel available for combustion during each power stroke.

Advantages

Diesels get great mileage. They typically deliver 25 to 30 percent better fuel economy than similarly performing gasoline engines. Diesel fuel is one of the most efficient and energy dense fuels available today. Because it contains more usable energy than gasoline, it delivers better fuel economy. Diesels have no spark plugs or distributors. Therefore, they never need ignition tune-ups. Diesel engines are built to withstand the rigors of higher compression. Consequently, they usually last much longer than gas-powered vehicles before they require major repairs.

Disadvantages

Although diesel fuel used to be cheaper than gasoline, it now often costs the same amount or more. Although diesel fuel is considered to be more efficient because it converts heat into energy rather than sending the heat out the tailpipe as gas-powered vehicles do, it doesn’t result in flashy high-speed performance. Diesels still need regular maintenance to keep them running. You have to change the oil and the air, oil, and fuel filters. If you neglect the maintenance and the fuel injection system breaks down, you may have to pay a diesel mechanic more money to get things fixed than you would to repair a gasoline system because diesel engines are more technologically advanced.

This week the Trudeau government revived plans to completely eliminate the production of new-build gas and diesel cars by 2035. It’s an ambitious goal, given that there isn’t really a solid blueprint that we’re supposed to follow — in fact, the entire announcement was incredibly vague — but it’s aligned with other eco-friendly nations committing to reducing emissions. Omar Alghabra, the minister of transport, explained that the government would be “expanding and strengthening” the existing incentive programs, but other than that it was crickets. So far, there are about 90,000 Canadians driving zero-emissions vehicles, and that’s thanks in part to a $600 million investment from the federal government, which offers drivers a $5,000 incentive.

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