THE STUDY of mechanical power

Transcription

1 The Internal Combustion Engine and Its Importance to Agriculture THE STUDY of mechanical power covers a broad area of learning. A basic understanding of engines is important if you are to keep pace with advancements in agricultural mechanics. The first gasoline-powered engine was created in 1860 but was not practical. In 1876 the first practical gasoline-powered engine was invented. Some of the early difficulty in creating engines was getting the piston to return to its original position before repeating the cycle. Objective: Describe the modern internal combustion engine and its effect on agriculture. Key Terms: connecting rod crankshaft cylinder distillation internal combustion engines piston reciprocate Page 1 AgEdLibrary.com

2 The Internal Combustion Engine In 1678 a Frenchman named Jean de Hautefeuille designed the first engine to use heat as a motive force and to be capable of doing continuous work. About 1680 Christian Huygens, a Dutchman, designed the first engine using a cylinder and a piston. Neither of these engines was successful, and attempts to build an internal combustion engine were abandoned. The French inventor Beau de Rochas developed the theory that four distinct events create an operating cycle: intake, compression, power, and exhaust. His theory of operation still applies to modern engines. Strangely, de Rochas never constructed an engine to prove his theory. N. A. Otto, a German, used the theory of Beau de Rochas to build the first successful engine to operate on the four-stroke-cycle principle. This engine was followed by a twostroke-cycle engine patented by Englishman Dugald Clerk. A German, Rudolph Diesel, produced a high-compression engine to ignite the fuel in the cylinder. His efforts were not successful until 1898, when the first diesel engines were produced. A diesel engine was first used in a farm tractor in 193l. Intake open Exhaust Both s Both s Intake Exhaust open Air/fuel mixture in Spark plug Spark Exhaust gases out a b c d Intake Compression Power Exhaust FIGURE 1. The operation of a four-stroke-cycle spark-ignition engine. Internal combustion engines convert the stored energy in fuel to heat, which is then converted to mechanical power. The most common internal combustion engines are the piston-type gasoline engine and the diesel engine. A gasoline engine requires a spark to ignite the fuel-air mixture and is different from a diesel engine that relies on compression to generate the heat required to ignite the fuel-air mixture. Page 2 AgEdLibrary.com

3 The space where the combustion occurs is called a cylinder. Engines are manufactured in single- and multi-cylinder designs. A multi-cylinder engine is typically one of four styles: A single row of cylinders in a vertical position (in-line engine) A double row of cylinders forming a V pattern (V engine) A double zigzag row of cylinders with alternating pairs of opposite cylinders creating two Vs (W engine) Two horizontal rows of cylinders, opposite rows opposed (pancake, flat, or boxer engine) In each cylinder, a piston slides up and down. The piston is connected to the crankshaft using a connecting rod. The crank shape of the crankshaft causes the piston to reciprocate that is, move up and down as the crankshaft rotates. Before the creation of the internal combustion engine, steam engines or animals created rotary power. In the 1870s, engineers successfully created steam traction engines, referred today as steam tractors. These were very large machines and were undesirable for most farms in North America. Steam traction engines were popular for large operations, where they could offset the cost of draft animals. Steam traction engines were slow to be adopted because of their size, their complexity, and the danger of explosion. With the commercialization of the internal combustion engine, a more practical power source was available. Farmers purchased large numbers of stationary gasoline Valves Combustion chamber Piston Connecting rod Crankshaft FIGURE 2. Components of a cylinder in an internal combustion engine. engines in the early part of the twentieth century. A wide variety of household chores were simplified by the use of stationary engines. Companies began developing gasoline-powered traction engines during the same period. These machines became known as tractors. EARLY TRACTORS Early tractors shared similar traits with steam traction engines. They were large, expensive, and difficult to maneuver. These early tractors were quickly reduced in size and cost as engine technology progressed. The Fordson is credited with being the first successful small tractor. The new tractors proved to be excellent at plowing and were capable of other tasks. Page 3 AgEdLibrary.com

4 Competition with Ford forced International Harvester to make improvements in its tractors. A result of the improvements made by International Harvester was the development of a general-purpose tractor, the Farmall, in The other tractor manufacturers, such as Deere, Massey-Harris, and Case rushed to develop general-purpose tractors. The general-purpose tractor had high ground clearance, small front wheels, and minimal weight. It was designed for cultivating, as well as plowing and cutting. By the mid-1930s, the adoption of tractors powered by internal combustion engines was in full progress. During World War II, tractors played a very important part in producing the agricultural products required to support an army at war. IGNITION Early inventors of gasoline engines were constantly looking for better efficiency and a satisfactory method of igniting the fuel charge in the combustion chamber. Open flames, glow plugs, and red-hot wires were used to ignite the fuel charge. Today we have a much more dependable system using electricity. The first device for producing electricity was created by Otto Von Guericke, a German. Italian Count Alessandro Volta developed the first storage battery. Volta s battery was improved and enlarged until it was practical for engine use. Battery voltage must be increased before it will jump between two electrodes. These electrical principles were adapted to engines by placing electrodes in the spark plugs. The spark plugs are screwed into the engine combustion chamber. The electricity jumping the gap across the electrodes creates a spark. The spark at the spark plug ignites the fuel charge. Producing electrical energy and storing it in a battery are important developments for internal combustion engines. LUBRICATION The moving parts of any engine require some lubrication to reduce friction. Friction retards performance and destroys engine parts. The early engines ran slow enough that lubrication was less of a problem than in today s faster-running, more powerful engines. Newer engines require a high-quality lubricant to reduce friction, provide cooling, and cushion the forces created as the fuel is ignited. Whale oil provided lubrication prior to the petroleum industry. The first oil well was dug in The crude oil was primarily for use in lamps. Explosions of the crude lamps showed the presence of a combustible gas. Separating the combustible gas from the crude oil was done by a process called distillation. The products of distillation were engine fuel and oil for lubrication. Oil helped reduce friction and created a seal between the piston and the cylinder. The seal created by the oil made engines more powerful and efficient. As manufacturing technology improved, engines operated faster and became more powerful. The increase in speed and power placed new demands on lubricants to perform at a higher level. Page 4 AgEdLibrary.com

5 THE MECHANIZATION OF TILLAGE AND HARVESTING The development of steam engines made possible the mechanization of some tillage and harvesting operations. Steam engines were heavy and awkward to handle. More versatile and lighter internal combustion engines were developed for farm use in the early part of the twentieth century. These engines had a tremendous influence on the mechanization of agriculture. Today, with modern equipment, less than 2 percent of our population is engaged in farming. Their production provides for domestic use and export. Mechanization has helped make production of farm products possible with a great reduction in the labor required. In FIGURE 3. A modern-day tractor. (Courtesy, AGCO) 1800, about 55 worker-hours were needed to produce an acre of wheat. In 1875, using steam traction engines and horses, about 15 worker-hours were needed. In 1925, using early gasoline tractors, an acre of wheat could be produced in about five worker-hours. Modern machinery requires a little more than one worker-hour to produce the same acre of wheat. Summary: Early on, a need was recognized for suitable mechanical power for farms. The introduction of gasoline-powered tractors enabled farmers to replace horses for tillage and increase production. As engine size became smaller, engines were accepted on farms to perform a large variety of chores. The lighter engines were adapted to power smaller tractors. The general-purpose tractors were capable of many tasks and were rapidly adopted. Internal combustion engines, especially in tractors, have dramatically reduced the demand for labor to produce agricultural commodities. Checking Your Knowledge: 1. Define an internal combustion engine. 2. What caused the decline in popularity of steam traction engines? 3. What were the advantages of general-purpose tractors? 4. How did the invention of the battery affect the development of internal combustion engines? Page 5 AgEdLibrary.com

6 5. How did the development of the internal combustion engine affect the production of farm commodities? Expanding Your Knowledge: Create a timeline and enter the key dates and discoveries pertaining to internal combustion engines in agriculture. Web Links: Inventors Internal Combustion Engine Agricultural Career Profiles Page 6 AgEdLibrary.com