Automotive engines and tractors history and development of engines

During the early part of the twentieth century, some steam-operated [1] automobiles were in use. Since the steam engine can be stopped and started or reversed at will, no clutch or transmission was required. However, the troubles encountered in the operation of the steam engine, along with the development of internal combustion engines [2] and storage batteries [3], resulted in the gradual elimination [4] of the steam-propelled automobile. The development of the automobile in the 1890’s did much to further development of the internal combustion engine. Gradual acceptance of the automobile into our form of living brought about a demand for dependability, economy, smoothness and quietness of operation, and increased power and speeds. Early internal combustion engines used in automobiles had few cylinders, had low-compression pressures, and developed little power. The engines were large and of considerable weight, and were quite noisy and rough in operation.

In order to improve the performance of the automobile, it was necessary to increase the power developed by the engine. This was generally accomplished by increasing the size or number of cylinders or the length of the stroke [5]. However, such improvements usually increased the weight and cumbersomeness [6] of the engine. Regardless of the number or size of the cylinders, these were all low-compression engines approximately, 60 psi (pounds per square inch). Top engine speeds seldom exceeded 2, 000 rpm (revolutions per minute).

The acceptance by the public of the automobile as a means of transportation produced a demand for the improvement and development of roads. As more people began to use and operate automobiles, the demand increased for greater reliability, higher speeds, and economy of operation.

Improvements in fuels permitted higher compression pressures, resulting in increases in power and engine speeds. Higher engine speeds, along with the improved fuels, required changes in the combustion chamber [7] design, resulting in a more even burning of the fuel mixture within the cylinder. As engine speeds increased, the timing of the valves [8] became more critical. High operating speeds required that the valves be held open for longer periods of time in order to allow sufficient time for the fuel charge to enter the cylinder and the burned gases to be expelled.

The demand for better materials resulted in the rapid development of the various sciences. While science, has contributed much to the modern automobile engine, the engine has likewise contributed much to science by creating the need for better materials. The requirements for interchangeable parts to permit mass production have revolutionized manufacturing processes. While it can be said that modern manufacturing methods make possible the present-day automobile engine, it is equally true that the automobile engine has made possible the present methods and standards in manufacturing.

While the internal combustion engine has undergone numerous changes in design and construction, its basic principle of operation has not changed. Many engines operate on the four-stroke-cycle [9] principle patented by Dr. Otto in 1876.

Others operate on the two-stroke-cycle principle. Aside from improvements in materials and methods, the chief changes that have been made in these engines are:

(1) Increased compression ratios.

(2) Improved valve timing.

(3) Better balance of moving parts.

(4) Better mixing and distribution of fuel.

(5) More accurate timing of fuel charge ignition

These changes have resulted in compact, powerful, highly efficient engines, of light weight that can operate at extremely high speeds. The weight per horsepower developed has been reduced to but a fraction [10] of the weight of early engines. Nevertheless, in principle, the modern automobile engine is the same as originally conceived.

Who invented the car?

Two Germans, Carl Benz and Gottlieb Daimler, both took credit for making the first car. Eventually the car companies that they founded combined to become the Daimler-Benz Company, which still produces Mercedes-Benz automobiles more than 100 years later.

Carl Benz was born in 1844, 10 years after Gottlieb Daimler. Both Germans were mechanical engineers who worked to develop internal combustion engines that ran on liquid gasoline. Then they installed the engines on bicycles, carriages and other vehicles that were normally powered by people or animals. When these early experiments worked well, the inventors continued to improve their designs until the first cars were ready to race.

Carl Benz used a gasoline-powered engine with one cylinder to power a three-wheeled car in 1885, but he did not get it patented until 1886. His car had a tiller to steer the front wheel. Carl Benz began selling his cars in 1887. Gottlieb Daimler patented his internal combustion engine in 1885. He also invented a carburetor. Gottlieb Daimler sold one of his first cars to the Sultan of Morocco in 1889. In 1926, the two companies became the Daimler-Benz Company.

Other European and American inventors added innovations to make other versions of early automobiles. Emile Levassor, a French man, was the first person to think of putting the engine in the front of the car. This allowed a more powerful engine than those used by either Benz or Daimler. Levassor’s engine had two cylinders. He showed off his automobile in a 700-mile race in France, which he won in 49 hours.

Automobile races became popular ways for American car makers to test market their designs. They also helped get the onlookers interested in perhaps becoming car owners someday. One famous car race happened in Chicago on Thanksgiving Day in 1895. Two car makers from Springfield, Massachusetts, Charles and Frank Duryea, entered one of the two cars that finished the 49-mile race. The other winner was one of Carl Benz's cars from Germany.

It did not take many years before cars became affordable to regular people. In 1900, 48, 000 people attended the first National Automobile Show in New York's Madison Square Garden. In 1908, Henry Ford started the Ford Motor Company, which became famous for building the Model T, which sold for $850 at first. It got cheaper, though - 8 years later, a Model T Ford only cost $360. New 2009 Fords range in price from $17, 000 to more than $34, 000.

Вариант №2

A COMPARISON OF SPARK-IGNITION [11] AND

COMPRESSION-IGNITION [12] ENGINES

CI and SI Engine Uses. The gasoline engine has been most useful in automobiles, light trucks, a type tractor. The diesel or oil-burning engine has been most popular in boats, in locomotives, and in powerhouses. As the speed of the diesel engine has been increased, it has been used in more farm tractors, particularly in those of the crawler type. Because of other, characteristics the diesel engine is gaining favor for the row or wheel type of farm tractor.

What, essentially, are the differences between the CI and SI engines?

The SI Fuel System. One of the main differences is how the fuel is mixed. In the SI engine we must provide a carburetor or mixer. This is a device for mixing air with fuel. There are several hundred different carburetors in use. Some are quite simple and others are extremely complicated. One characteristic of most carbu­retors is that they must be in operation almost on a level or the liquid fuel will leak out. This sometimes causes faulty operation when the tractor SI engine is tipped at a considerable angle or when the farm truck goes around a corner.

The CI Fuel System. The CI engine does not have a carburetor. The fuel is not mixed with the air outside of the cylinder space as in the SI engine. As a substitute for the carburetor, a pump [13] and an injector [14] are used. There are not as many injectors in use as there are carburetors, but injectors and pumps are very precise instruments. There is an injector or nozzle [15] for every cylinder. Their purpose is to prevent the air within the combustion chamber [16] from leaking out but at the same time inject a stream of fuel into the hot compressed gases at the correct time and interval. It is, therefore, apparent that the air and fuel must mix within the combustion space. The correct mixing of the fuel and air in the space above the piston is a difficult design problem.

Injectors and Carburetors. In the SI engine, air and fuel are compressed together. In the CI engine, the air alone is compressed in the cylinder space the fuel is compressed as a liquid by a pump at the side of the engine. This pump must develop a pressure greater than that of the air within the cylinder. The usual pressure is about 2700 psia (pounds per square inch, absolute). As the pressures in the cylinder before combustion will seldom be higher than 800 psia the liquid fuel can be forced into the cylinder at the proper time. Of course, this pump requires a force to operate it, and it is negative work; that is, it does not add to our output of power. The ordinary carburetor does not require any power to operate; there is some friction loss, however.

Terminology. Usually the term SI means or implies that a carburetor is being used. The CI engine never has a carburetor, - as the fuel is forced into the cylinder space by an injector. The injection of the fuel is sometimes misnamed [17] solid injection. As the fuel is not in solid form, this is a misnomer [18]. A better name is liquid injection.

Throttling [19]. The carburetor of the SI engine must deliver the fuel to the manifold [20] and to the cylinder in rather definite ratios of fuel to air. If this is not done, the engine will not operate correctly. The usual fuel-to-air ratio would be about 1 lb [21] of fuel to 15 lb of air. Not only must the ratio be correct, but also the amount of mixture fed to the cylinder must be controlled. The usual method of controlling the amount of mixture, and therefore the power arid speed of the SI engine, is to install a butterfly valve in the passageway leading from the carburetor to the manifold. By turning this butterfly valve it is possible to regulate the amount of fuel and air from a zero to a maximum. Moving the butterfly valve is called throttling. That is, throttling an engine would imply regulating its speed. A closed throttle would allow the engine to idle a full throttle would allow the engine to develop full power or speed. The manifold throttle is a characteristic of the SI engine. It is not found on the CI engine. It is an important difference between the two types of engines. The throttle has considerable influence on the efficiency of the SI type of engine; for when the throttle is almost fully open, the efficiency is the highest; when the throttle is at idling position; the efficiency is the lowest.

Thus, the SI engine power is varied gaby manifold throttling. This means that the amount of the fuel mixture is varied. In the diesel, only the fuel amount is varied; the air volume remains relatively constant. Thus a diesel can operate on such a small quantity of fuel that the air-to-fuel ratio may became 100: 1, which is a very economical ratio. This explains why the diesel will operate economically at light loads. The large amount of surplus air also causes the diesel to operate at lower temperatures. Thus, because of combustion characteristics, the diesel runs more economically, and cooler at the slower speeds. And, because of the possible higher compression ratio, the diesel is able to convert more of the heat energy of the fuel into work energy at any speed.

Heavier Parts. The diesel engine has to be made heavier than the gasoline engine in order to withstand [22] the higher pressures. These pressures are against the cylinder walls or liners, against the head and valves, and against the piston head. These additional pressures are transferred through the piston head to the piston pin through the connecting rod and to the crankshaft pin. All these parts must be made heavier. The crankshaft [23] is heavier, the rods are stronger, the bearings are thicker and wider, and more bearings are used. Almost every diesel has a main bearing between each crank throw for greater support. All this extra strength requirement means a heavier engine and a more expensive engine.

Вариант №3