What Is an Internal Combustion Engine and How Have Car Manufacturers Modified It - Assignment Example

The history of internal combustion engines (ICEs) invention can be traced way before the start of commercial production of the commonly used petroleum fuel. However, the application of these engines was limited until in the late 1800s when they were used in various applications. The real practical use of ICEs to power cars started after the modification of an engine concept developed by Nicolaus Otto by Gottlieb Daimler and Wilhelm Maybach in 1885. Since then, car manufacturers have made various improvements to the basic design of the internal combustion engine. This document explains the meaning of internal combustion engine and explores how car manufacturers have modified these types of engines. Internal combustion engine An internal combustion engine (ICE) is a kind of engine in which a mixture of fuel and air is burned within a chamber so that the resultant pressure and temperature exerts force on a movable part that in turn generates mechanical energy. Examples of these movable parts include pistons and turbine rotor blades. Basically, internal combustion engines have four distinct processes that are essential for its operation. These are the intake phase, the exhaust phase, compression phase, and the power phase. In some engine configurations, however, some phases do occur simultaneously. The intake phase allows intake of fuel or air - depending on the type of engine - while the exhaust phase expels out the combustion products. The compression phase increases the pressure and temperature of air in direct injection engines, and of fuel/air mixture in spark plug-based engines. The power phase involves combustion of fuel and air mixture to produce energy that, in turn, is converted into mechanical energy. Internal combustion engines can be grouped into continuous and intermittent types. The continuous combustion engines include the jet engines, gas turbines, and many rocket engines, while the intermittent combustion engines include the common two-stroke and four stroke piston engines, and the Wankel rotary engines. These continuous combustion engines are characterized by a steady flow of fuel and air into the combustions chamber to maintain a stable flame, and hence continuous combustion. On the other hand, intermittent combustion engines involves periodic ignition of discrete amounts of fuel and air. Internal combustion engines are also differentiated by the type of fuel used for combustion. Fuels used on these engines include petroleum fuels, vegoil and biofuel, coal, and hydrogen fuel. Some of the petroleum-based fuels used nowadays are petroleum spirit (which is known as petrol in the United Kingdom and gasoline in the United States), petroleum diesel, liquefied petroleum gas, compressed natural gas, jet fuel, and residual fuel. Biofuels include biogas, biobutanol, biodiesel, bioethanol, and biomethanol. Biobutanol is sometimes used as a replacement to gasoline, while biodiesel is sometimes used in place of petrodiesel. Hydrogen fuel is mostly used in spacecrafts’ rocket engines. ICEs are so much distinct from the external combustion engines (ECE). ECEs, which include Stirling or steam engines, operate by delivering energy to a working fluid that is not composed of, or mixed with combustion elements. These fluids can either be water, air or liquid sodium. They are often heated in a boiler by burning wood, fossil fuel, solar, nuclear, etcetera. ICEs are used in both stationary and mobile applications, although mostly they are used to power cars, boats, and aircrafts. Note that the focus for this essay is on internal combustion engines developed by car manufacturers. How car manufacturers have modified internal combustion engine The original basic design of an automobile internal combustion engine can be attributed to the invention by Gottlieb Daimler and Wilhelm Maybach. Daimler and Maybach developed an internal combustion engine in 1885 that was more or less a modification of the one built by Nicolaus Otto in 1876. Otto’s engine was an effective four-stroke gas engine that he used to power a motorcycle. The engine developed by Daimler and Maybach was small, lightweight and fast. It used a carburetor to inject gasoline into a vertical cylinder. These elements led to a revolution in designs of cars. In 1886, Daimler created the first four-wheeled vehicle when he incorporated the modified engine into a stagecoach. This invention was significant for car manufacturers who have since made various modifications to the original internal combustion engines used to power vehicles. The initial modification to a car internal combustion engine can also be credited to Daimler. In 1889, Daimler built a v-slanted four-stroke engine that had two cylinders and whose valves were shaped like a mushroom. As was the original design, the modified engine used a carburetor for gasoline injection, and a spark plug to ignite a mixture of fuel and air in the engine cylinder. The development of diesel engines is a modification of the original internal combustion engines that use gasoline. A diesel engine was first invented in 1897 by Rudolph Diesel. Unlike in Otto cycle gasoline engines, in Otto cycle diesel engines ignition of fuel occurs as a result of the heat generated during the compression stroke. Only air is compressed in diesel engines and the diesel fuel is injected to cause the combustion. There are also other developments of diesels engines that are not based on the Otto cycle concept. Modification of internal combustion engine has also been characterized by variation in the number of engine strokes. Besides the four-stroke engines, car manufacturers have also developed two-stroke and six-stroke engines to power cars. A two-stroke engine makes a complete working cycle when a piston makes two movements. This is achieved by allowing the intake of fuel/air mixture and exhaust of combustion products to occur simultaneously during the start of the compression phase and the end of the combustion phase. As a result, two-stroke engines often produced remarkably “high specific power” (Bohnet, 2003). However, high specific power has not been a very significant aspect to car manufacturers in the choice of engines to use (Duret, 1993). The six-stroke engines are based on the concept of four-stroke engines, although certain features have been added to minimize emissions and enhance its efficiency. There have been two distinct concepts of the six-stroke engine type developed in the late 20th century. The first concept allows the engine to capture heat that would be otherwise lost in a four-stroke petrol or diesel engine to power two extra piston strokes - power and exhaust strokes within the same engine cylinder. This kind of engine uses either air or steam as the working fluid for the two additional strokes (Lyons, 2006). The other six-stroke engine concept introduces a second piston opposed to the main piston in a single engine cylinder. The opposed piston moves at a speed that is half the cyclical rate of the other piston so that a complete cycle results in six movements of the piston. These engines, however, have not yet been widely used to power cars. Some car manufacturers have made modifications to the Atkinson-cycle engines for use in powering cars. The original design of the Atkinson-cycle engines is characterized by occurrence of the intake, exhaust, power, and compression strokes typical of a four-stroke cycle within a single rotation of the crankshaft. This type of engine was designed and developed to avoid violation of the patent rights granted to Nicolaus Otto for his four-stroke engine design (Jester, 2007). The ideal Atkinson-cycle can be described by four phases namely the reversible adiabatic compression, isochoric heating, isentropic expansion, and the isobaric cooling. Atkinson-cycle engines have the advantage of efficient use of fuel when compared to other engine types (Heywood, 2007). However, the original concept of Atkinson-cycle engines has remained more of an ideal concept than a practical application. Therefore, car manufacturers have made various modifications make use of the fuel efficiency aspect of the Atkinson-cycle concept. One modification is actually a remake of the Otto cycle engine that features some aspects of the Atkinson-cycle. This modification is characterized by the aspects a four-stroke engine (Otto cycle engine) and an intake phase that is longer than usual. The prolonged intake phase is typical of Atkinson-cycle engines, but unusual with Otto cycle engines. This allows the intake air to reverse-flow into the intake manifold. The effect of this arrangement is reduced compression ratio, and one that is less than the expansion ratio. The aim of these modifications is to allow pressure arising at the end of a power stroke due to combustion process to equal the atmospheric pressure; this allows all the obtainable energy from the compression process to be utilized. Furthermore, for any specific air portion, the higher expansions ratio permits conversion of more heat energy into effective mechanical energy implying that this kind of engine is more efficient. Even with this modification of the four-stroke engine to make them more fuel economical, the resultant engine has less power-per-displacement than the Otto Cycle engines (Heywood, 2007). However, car manufacturers have solved this by incorporating electric motors to supplement in situations where more power is required. This kind of engine and arrangement has been used in various car models including Toyota Prius hybrid, Ford Escape, Mercury Mariner, Mazda Tribute, Ford Fusion Hybrid, Mercury Milan Hybrid, Toyota Camry Hybrid, Chevrolet Tahoe Hybrid, Mercedes ML450 Hybrid, and Lexus RX 450h hybrid. The other modification of Atkinson-cycle engine is more less a Miller cycle engine. The Miller cycle engine also resembles an Otto cycle engine with a prolonged intake phase. This basic engine design suffers the disadvantage of internal power loss because of the energy required in compression of the air/fuel mixture during the compression phase of the cycle. However, car manufacturers have incorporated superchargers in such modifications to compensate for the loss of power density. A typical Miller cycle engine is characterized by a compression stroke that has two separate stages; that is, the first part where the intake valve remains open and the final part when the intake valve remains closed. As it would happen with the four-stroke engines (Otto cycle design), leaving the intake valve open during the compression phase would expel the air/fuel mixture back into the intake manifold and consequently cause power loss. Nonetheless, with the Miller design, the loss of power is compensated for by the installed supercharger. Positive displacement supercharges have often been used so as to allow power boost even when the engine is running a relatively low speed. An example of a Miller cycle engine is the Mazda KJ-ZEM V6 that has been built in the Millenia sedan and in Eunos 800 sedan luxury vehicles. Subaru has also used a Miller cycle engine in their Subaru B5-TPH. Modification on internal combustion engine can also be interpreted through the development of the Wankel engines. The basic concept of a Wankel engine is that rotary blades are used to translate pressure into rotational movements rather than using pistons. Similar to an Otto cycle engine, a Wankel engine is characterized by a four-stroke cycle. However, this engine has epitrochoid-shaped (almost oval shape) housing, and within it is a rotor that is shaped like a Reuleaux triangle. The four-stroke cycle of this engine therefore occurs within the space between the housing and the rotor. This type of engine was created by a German engineer known as Felix Wankel who completed it in 1957. Wankel rotary engines have been used in a number of vehicles. Since its invention, various car manufacturers have enhanced the basic design of Wankel rotary engine and used the modified version to power cars. The first person to enhance this type of engine was Curtiss-Wright, although his was just minor improvements. In addition, Rolls Royce made modification to the original version of this engine in the 1960s and came up with a two-phase Wankel engine that run on diesel. Suzuki and Norton Motorcycle have developed Wankel engines that they used to power their motorcycles. Deere and Company have also created a Wankel engine that can use a number of fuels. This engine was used to power combat vehicles used by the United States Marine Corps in 1980s (Hege, 2001). The AvtoVAz of Soviet Union created the VAZ-311, VAZ-411, VAZ-415, VAZ-4132 engines. The VAZ-411 engines had twin rotors. Mercedes Benz used Wankel engines in their C111 prototype car. The Japanese car maker, Mazda, have used Wankel engines extensively to power their vehicles. The first Mazda car to run on Wankel rotary engine was the Cosmo, which was built in 1967. The company continued to manufacture more vehicles based on this type of engine, including a pick-up truck, and a bus. It later stopped producing most of its vehicles with this engine, but continued to use this type of engine on their RX-7 and RX-8 car models. The Mazda RX-8, however, used a Wankel engine known as Regenesis that was more advanced than its previous Wankel engines. Mazda placed the intake and exhaust ports of its previous Wankel engines at the rotary housing periphery. However, its Regenesis engine featured exhaust and intake ports that were placed at the sides of the rotary housing to allow for larger ports, improved inflow, and increased power. While the exhaust and intake ports of the first Wankel engines were also located at the sides, this arrangement resulted in carbon build-up at the rotor side and in the ports. The Regenesis used an advanced seal that scraped off the build-up. Car manufacturers have also made modifications to the gasoline based engines to allow them to use hydrogen as a fuel. A hydrogen internal combustion engine burns hydrogen in the same way that a petrol engine does. The first hydrogen-fueled ICE was designed by Francois Isaac de Rivaz in 1807. Paul Dieges also designed and patented a hydrogen-run engine in 1970, which was simply a modification of the typical gasoline internal combustion engine. Mazda has made modifications to the Wankel engine and come up with a type of engine that runs on hydrogen. Manufacturers have also modified diesel internal combustion engines to run on hydrogen. One example is the hydrogen-based direct injection engine used to power HICE lift trucks; it also has a compressor. Some car manufacturers have also made modifications to internal combustion engines so that direct injection technology can work with gasoline. Traditionally, the direct injection concept was only practical with diesel engines. However, some car manufacturers have attempted to take the advantage of this technology to increase the efficiency of the two-stroke engines. Most car makers have adopted this technology in their two-stroke engines. It is worth to note that the earlier carburetor-based two stroke engines were not very efficient. However, two-stroke engines have been used mainly in motorcycles and some fun vehicles such as the personal watercrafts and snowmobiles (Duret, 1993). Other modifications of the internal combustion engine include the indirect injection technology, forced induction technology, and electronic fuel injection (EFI) technology. Indirect injection engines have a pre-chamber where air/fuel mixture ignites and the combustion spreads into the rest of t he chamber. The effect of pre-chamber mixing is reduced combustion rate that in turn reduces noise and shock of combustion as well as lessens the stress on the engine parts. Forced induction refers to the process of forcing air in to the combustion chamber of an ICE. Modern car manufacturers are using the two common forced induction technologies namely the superchargers and turbochargers. Superchargers and turbochargers are simply an air or gas compressors. However, a supercharger is uses the direct mechanical drive of an engine, while a turbochargers has it compressor driven by a turbine. Fuel injection is a method of mixing air and fuel for combustion. Most ICEs including petrol engines now use this method of fuel/air mixing, especially with the advent of the EFI. EFI technology has revolutionized internal combustion engines, resulting in the unpopularity of the once dominant carburetor system. Some EFI technology allows use of different fuel types in common engines hardware. A fuel injector is simply a nozzle with a valve that relies on a pump to release fuel at high pressure. In EFI injection of fuel is controlled electronically. Conclusion This essay has explained the meaning of an internal combustion engine and explored how car manufacturers have made modifications to it. Thus, internal combustion engines are characterized by combustion of a fuel/air mixture within a combustion chamber. The modifications of ICEs began with Daimler and Maybach, and since then several modifications have been witness to date. These modifications include the diesel engines, Wankel engines, Miller cycle engine, and Atkinson cycle engines as well as variations of the number of piston strokes per working cycle. ICEs have also varied in terms of number of cylinders in an engine and depending on the type of fuels used and the method used to ignite the fuel. References Bohnet, M. (2003). Ullmann's encyclopedia of industrial chemistry. 6th edn. Vol. 20. Wiley, Australia. Duret, P. (1993). A New generation of two-stroke engines for the future?: proceedings of the international seminar held in Rueil-Malmaison, France, November 29-30, 1993, TECHNIP, United States. Hege, J. B. (2001). The Wankel Rotary Engine. McFarland, Carolina. Heywood, J. B (1988). Internal combustion engine fundamentals. McGraw-Hill Science, New York. Jester, R. K. (2007). Aggresive energy recovery from the waste heat of a hybrid automotive powerplant. University of Wisconsin, Madison. Lyons, P. (2006). Inside Bruce Crower’s six-stroke engine. Retrieved 14 January 20101 from http://www.autoweek.com/apps/pbcs.dll/article?aid=/20060227/free/302270007/1023/thisweeksissue. Read More