An automotive engine is a propulsion system responsible for moving automobiles from one place to another. An engine converts energy from a fuel or a battery to the mechanical energy used to spin the wheels, thus setting a vehicle in motion. There are different types of engines used in the automotive industry today. These include internal combustion engines and electricity driven vehicles. The internal combustion engines burn fuels such as petrol, diesel, natural gas or propane. Electric engines are fitted with electromagnetic motors that are powered by electric currents from storage batteries on the vehicle. The sole purpose of an engine is to produce torque, which is then picked up by a system of gears and shafts and transmitted to the wheels. This paper examines different types of engines with regard to how they are powered and their mode of operation.
Internal combustion engines
Powering of an internal combustion engine
Internal combustion engines are powered by a fuel. Liquid fuels such as petrol and diesel are atomized to a gaseous state. The fuel is then cleaned by a device referred to as a carburetor and mixed with air. The air acts as a source of oxygen necessary for combustion. An intake manifold controls the amount of air that goes into a given volume of fuel. The fuel is then injected into the engine and ignited for it to combust. After the air fuel gas mixture combust, flue gases are formed as products of the combustion process with the release of heat energy. When the fuel combust, the energy in the hydrocarbon chemical bonds is released causing a drastic increase in volume (Internal Combustion Engine Basics par.5). The potential energy of the compressed fuel gases is then used to drive the engine.
Operation of an internal combustion engine
Internal combustion engines can be classified into two categories according to their mode of ignition, compression ignition and spark ignition. The compression ignition engines are powered exclusively by diesel while the spark ignition engines are found in petrol vehicles. Compression ignition engines ignite the fuel by applying high amounts of pressure on the gaseous fuel until it ignites. On the other hand, a spark emitted by a spark plug is used to ignite the fuel in petrol engines. The fuel in internal combustion engines is combusted within a confined cylinder in the engine. The cylinder houses an airtight piston, which is coupled to a crankshaft. The average engine has four piston cylinders and operates on a four stroke cycle (Hall par.3).
The four stroke cycle comprises of four consequent processes, the intake, compression, power, and the exhaust stroke. During the intake cycle, the piston moves downwards thereby creating a partial vacuum in the cylinder which causes the fuel to flow in. The piston then moves upwards and compresses the fuel before its ignited. Combustion of the fuel causes an increase in volume, which forces the piston downwards in the power stroke. Finally, the piston moves upwards and pushes the flue gases out of the cylinder in the exhaust stroke (Hall par.5).
Figure 1: A piston and its cylinder housing in an internal combustion engine. Source: Glenn Research Centre
Electric vehicles
Powering of electric vehicles
Electric vehicles are primarily powered by rechargeable lead acid batteries. The batteries are charged from electric mains outlets and they store electric energy through the means of reversible chemical reactions. The batteries contain an electrolyte, such as sulfuric acid, which ionizes to release electrons that run through an external electric circuit thereby generating an electric current (What are Electric Cars par.3).
Operation of electric vehicles
Electric vehicles have three major components, the battery, an electric motor, and a controller. The battery provides the electric energy used to power the motor, which in turn converts the electric current to mechanical torque. On the other hand, the controller regulates the amount of current flowing into the motor in line with the drivers input such as acceleration and deceleration. Also, the controller converts the 300V direct current from the battery to an alternating current of 240V as required by the motor (What are Electric Cars par.5). A system of gears, shafts, and belts transmits the torque from the motor to the wheels.
Fuel cell powered vehicles
Fuel cell vehicles are a form of electric vehicles that use a fuel cell to power a motor instead of a lead acid battery. Fuel cells convert hydrogen fuel to electrical energy suitable for running the motor. Fuel cell powered vehicles are fitted with hydrogen storage tanks and an additional battery to complement the fuel cell. Hydrogen is reacted with oxygen to form water with the release of electrons that form the electric current (Fuel Cell Vehicles par.5). A controller regulates the flow of electric current to the motor as shown in figure 2 below.
Figure 2: Components of a fuel cell powered vehicle. Source: US Department of Energy.
Pneumatic vehicles
Pneumatic vehicles employ compressed air for their operation. The compressed air is used to operate pistons just like in internal combustion engines instead of a burning fuel. The vehicles have a pressure vessel that carries pressurized air, which is fed to the engine as required. The compressed air has potential energy, which is released to the engine as it expands. The engine converts the potential energy to mechanical energy (Stewart par.4).
Conclusion
Engines propulsion systems used to drive vehicles. Internal combustion engines convert the chemical energy of fuels to mechanical energy used to drive vehicles. Internal combustion engines are categorized into two groups, spark ignition for petrol engines and compression ignition for diesel engines. Electrical vehicles are powered by batteries that store electric energy, which is then used to power an electric motor. On the other hand, fuel cells in fuel cell powered vehicles convert hydrogen to electricity for running a motor. Finally, pneumatic vehicles convert the potential energy in compressed air to mechanical energy for running the vehicles.
Works Cited
“Fuel Cell Vehicles.” US Environmental Protection Agency. US Department of Energy, n.d. Web. 7 April 2016.
Hall Nancy. “4-Stroke Internal Combustion Engine” Glenn Research Center. NASA, 5 May 2015. Web. 7 April 2016.
“Internal Combustion Engine Basics.” US Department of Energy. Energy.gov, 22 November 2013. Web. 7 April 2016.
Stewart, Lea. “Top Five Air Powered Vehicles.” Inhabitat. Inhabitat.com, 10 January 2009. Web. 7 April 2016.
“What are Electric Cars?” Conserve Energy Future. Conserve Energy Future, n.d. Web. 7 April 2016.
