Internal Combustion Engines and Environment Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Internal combustion engines are the family of engines that confine fuel in a chamber, then burn it to convert the expansion of the resulting high temperature gases into work energy through pistons, rotors, turbines or other means. Although the range of fuels for an internal combustion engine (or ICE) is limited only by the need to produce combustion gases, petroleum derivatives are the preferred energy source due to their availability, high energy return, and portability.

Although there are many varieties of ICE, the most common is the Otto Cycle, or four-stroke, engine used in nearly all automobiles and trucks produced today. It is a reciprocating design where one piston drives others through a cam shaft, and the function is as follows: the first stroke of the piston draws in a fuel and air mixture by moving down the combustion chamber; then on the second, upward stroke the piston compresses the aerosolized fuel to the point of combustion (in the case of a diesel engine) or until the mixture is ignited by an electric spark (in a gasoline engine). In both, the expansion of the gases following combustion drives the piston downward, comprising the power stroke of the cycle. A fourth stroke returns the piston upward, and expels the contents of the chamber, preparing the chamber for the next stroke, which commences the cycle again. The two-stroke engine, common in smaller and portable mechanisms, operates using the same principles with the exception that a valve near the bottom of the chamber allows gases to escape at the bottom of the power stroke so that there is no need for a cycle to expel exhaust.

Gasoline engines first found widespread use operating farm machinery and as stationary power sources in factories. A lack of dependable fuel supplies and stations, and some engineering problems, prevented ICEs from out-competing steam and electric power in automobiles until the beginning of the 20th century. The expansion of refinery capacity and improved mechanical efficiency and reliability granted gasoline engines the edge necessary to capture the largest part of the automobile market in the first decade of the century, particularly after the introduction of the Model T in 1908. The basic design of the production gasoline engine has changed very little since it was standardized by the automobile industry in the 1910s, the major structural change being the replacement of carburetors with fuel injector systems. Most changes have instead come in materials, fuel, and peripheral components, often to meet either fuel economy or emissions regulations.

The advantages of petroleum-fueled ICEs in transportation is that they provide significant power using a compact fuel source in a highly reliable format, and allow the consumer to operate within unparalleled economies of scale. However, for almost a century, automobile and oil companies have consistently been among the largest and most profitable, and in the United States they have also been the recipients of large subsidies from the federal government. The disadvantages of widespread ICE use is the unprecedented changes to society and the global climate.

Society and Environment Impact

Socially, the introduction of the automobile coincided with a major shift in the urbanization of the American population. According to many, the automobile changed the traditional “walking city” with its busy pedestrian streets and close-knit neighborhoods into a noisy and dangerous “machine space” engineered to facilitate the efficient movement of motor traffic to the exclusion of other uses. The automobile is also blamed for the flight of residents from the city to suburbs, atomizing the old neighborhood framework and replacing it with a more insular and less community-oriented society.

On the positive side, the arrival of the ICE signaled the end of the era of animal-powered technology, lowering transportation times and costs, and requiring minimal maintenance when idle. Lower transport costs and portable power have linked ICEs directly to the dramatic decrease in real costs for many consumer goods. Affordable personal transportation is now a key component of the American dream, permitting the majority of the population to forego the high urban densities and high property costs common to the walking city for ownership of a freestanding house and yard. The Los Angeles metropolitan area in particular became an icon of car culture in the decades following World War II, and a model of urban development with land uses dedicated to freeways, drive-through conveniences, and single-family homes. Since the oil crises of the 1970s, concerns have arisen about the hidden social costs of dependence upon ICEs, including sprawl development, growing fears of disruption and exhaustion of petroleum supplies, and a reevaluation of the social impacts of automobile-driven development. Solutions include restructuring society away from dependence upon personal transportation and the current standards of dispersed, single-use zoning that encourages sprawl. The current popularity of form-based codes and New Urbanism reflect many of these concerns by encouraging community spaces that de-emphasize reliance upon automobiles.

ICEs are also central to the debate over air quality and global climate change. Long targeted as the majority of nonpoint source air pollution, most changes to ICE design have targeted reducing emissions and improving fuel efficiency. Early improvements included raising piston compression and preheating the fuel/air mixture to return more power and eliminate the products of incomplete combustion, and the addition of catalytic converters to exhaust systems to capture hydrocarbons that still escape the combustion process. However, improvements in engine compression and quality of combustion created new, unintended products that are less immediately noxious but remain dangerous including nitrous oxide (NO2), carbon monoxide (CO), and ozone (O3), which are particularly important causes of urban air pollution and damaging to human health. More recent improvements include computer control of the engine and fuel injection, as well as experiments with hybrid technology that uses the surplus heat energy of the Otto-cycle to generate electricity. These changes were sufficient to drastically reduce the amount of particulate and hydrocarbon emissions produced by ICEs; however, they only partially address the fundamental problem ICEs pose through global warming.

The optimal emissions of a hydrocarbon fueled ICE is a combination of water vapor and carbon dioxide, both of which identified as primary agents of climate change. Improvements to ICE efficiency only forestall the onset of global climate change, but do little to prevent it. This is true also of the alternatives to petroleum fuels, although some attempt to redirect the basis of energy into renewable sources. Because of their relative scarcity, other uses of ICEs have not attracted the same attention as their use in personal transportation, yet pose similar concerns. Commercial aircraft are especially criticized for polluting the upper levels of the atmosphere.

Bibliography:

Grayson, Beautiful Engines: Treasures of the Internal Combustion Century (Devereux Books, 2001);
J. Holt, 100 Years of Engine Developments (Warrendale, PA, Society of Automative Engineers, 2005);
K.W. Ko et al., “Effects of Engine Emissions from High-Speed Civil Transport Aircraft: A Two-Dimensional Modeling Study” (Atmospheric and Environmental Research Inc, 1991);
W. Zuckermann, End of the road: The World Car Crisis and How We Can Solve It (Chelsea Green Co, 1991).