Regan Brown
Gasoline is the fuel that powers many cars. It is one of the most energy-rich substances on Earth, with one gallon containing about 132 megajoules of energy. Gasoline is injected into the tank, then brought into the fuel line by a pump. A fuel filter prevents clogging by removing waste, and fuel injectors combine air with fuel before delivering it into pistons. The air-fuel mixture then goes into the combustion chamber, where it is ignited by a spark plug. The exhaust gases are then channelled out through the exhaust system.
| Characteristics | Values |
|---|---|
| Fuel | Gasoline |
| Energy density | 40+ megajoules per kilogram |
| Energy content | 132 megajoules per gallon |
| Octane ratings | 87, 89, 91, 93 |
| Fuel storage | Fuel tank |
| Fuel transfer | Fuel line |
| Fuel injection | Fuel injection system |
| Fuel ignition | Spark plug |
| Fuel/air combination | Fuel injectors/intake stroke |
| Fuel compression | Compression stroke |
| Exhaust | Exhaust valves/exhaust stroke |
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What You'll Learn
Gasoline is energy-rich
Gasoline is a transparent, yellowish, and flammable liquid that is used as a fuel for spark-ignited internal combustion engines. It is derived from the fractional distillation of petroleum and chemically enhanced with additives. Gasoline is energy-rich, and its energy density is significantly higher than that of other fuel sources. For instance, a gallon of gasoline contains approximately 132 megajoules of energy, while the next best liquid fuel source, ethanol, contains about 121 megajoules per gallon. This makes gasoline a highly efficient fuel source for vehicles.
The energy content of gasoline can vary depending on the season and producer, with blends differing by up to 1.75% from the average. On average, a barrel of crude oil yields around 74 liters (20 gallons) of gasoline, with the remainder consisting of products like tar and naphtha. The energy density of gasoline is also much higher than that of lithium batteries, which have an energy density of 1.8 megajoules per kilogram compared to gasoline's 40 megajoules per kilogram.
The energy in gasoline is released through combustion, where gasoline burns in a controlled process called deflagration. This combustion process occurs when gasoline is combined with oxygen from the ambient air, resulting in carbon dioxide and water as exhaust products. The energy released from the combustion of gasoline is approximately 46.7 megajoules per kilogram or 33.6 megajoules per liter when quoting the lower heating value.
The efficiency of gasoline engines can be improved through various mechanisms. For example, higher-octane fuels allow for a higher compression ratio, leading to a higher cylinder temperature and improved efficiency. Additionally, an Atkinson cycle engine uses valve timing to achieve the benefits of a high expansion ratio without the disadvantages of a high compression ratio, such as detonation. These advancements in engine technology have contributed to the widespread use of gasoline as a preferred fuel source for vehicles.
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The fuel's journey
Before the fuel enters the injection system, it goes through a fuel filter to remove waste and prevent clogging. After this, the fuel injectors combine air with the fuel before delivering it into the pistons. This mixture of air and fuel then enters the cylinder, where the piston descends, and the air-fuel mixture is compressed.
The compression of the air-fuel mixture generates heat, and once it reaches a certain temperature, it ignites. This ignition is also aided by a spark from a spark plug, which is unique to gasoline engines. The spark plug ensures the fuel burns at the right time, unlike diesel engines where the fuel can ignite spontaneously.
The ignition of the air-fuel mixture creates an expansion cycle, which increases the pressure and generates more hot gases. These hot gases then need to be released, so they are pushed out through the exhaust valves and exit the vehicle through the exhaust pipes. The exhaust gases are then converted into substances like nitrogen and carbon dioxide before being released into the atmosphere.
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The role of the spark plug
Gasoline is one of the most energy-rich fuel sources available. It is injected into either the intake manifold or the combustion chamber of an internal combustion engine, where it is combined with air. This air-fuel mixture is highly explosive when combined.
Spark plugs are an essential component of a car's ignition system. They are made from durable materials and are capable of withstanding millions of explosions before wearing out or needing to be replaced. They create a spark that ignites the air-fuel mixture, creating an explosion that forces the piston downward, turning the crankshaft and producing the power that makes your car move forward. This process is repeated thousands of times as you drive, with the spark plugs firing and igniting to keep the engine running.
The top of the spark plug contains a terminal that connects to the ignition system. The number of spark plugs in a car depends on the engine size, with most vehicles having at least four and some having as many as sixteen. Spark plugs are generally inexpensive, ranging from $2-3 for cheaper options to $20-$25 for premium plugs with precious metals.
Over time, spark plugs can become corroded or weakened, leading to reduced efficiency or misfiring. It is important to periodically change spark plugs to ensure optimal engine performance. Extended-life spark plugs have a longer lifespan of around 100,000 miles but may cost marginally more.
The heat range of a spark plug, which is affected by its construction, plays a role in preventing fouling and engine knocking. A "hotter" spark plug has less ceramic material, allowing the tip to retain heat better, while a "cooler" spark plug has a more substantial ceramic insulator to carry off heat.
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The four-stroke cycle
During the intake stroke, the piston descends with the inlet valve open, creating a partial vacuum that draws in a mixture of gasoline vapour and air. This stroke begins at the top dead centre (TDC) and ends at the bottom dead centre (BDC).
The compression stroke follows, with the piston ascending and both valves closed. During this stroke, the air-fuel mixture is compressed, increasing its temperature and pressure in preparation for ignition. This stroke begins at the BDC and ends at the TDC.
At the end of the compression stroke, an electric spark ignites the compressed mixture, causing it to burn and expand rapidly. This is the power stroke, where the expanding gases press on the piston head, generating mechanical power. Both valves remain closed during this stroke.
Finally, during the exhaust stroke, the piston ascends with the exhaust valve open, forcing the spent products of combustion out of the cylinder. This stroke begins at the TDC and ends at the BDC, completing one cycle. The four-stroke cycle then repeats itself, with the piston continuously moving up and down within the cylinder.
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Exhaust gases
The emissions of pollutants and greenhouse gases from cars have a harmful impact on the environment and public health. In Kazakhstan, motor vehicles account for 40% of total emissions of pollutants into the atmosphere from all technogenic sources. The number of toxic components in exhaust gas often exceeds the maximum permissible standards by tens or even hundreds of times. The small size of the chemical components in exhaust gases means they can be absorbed into the blood through lung tissue and harm various human organs.
The emissions from petrol-fuelled cars are treated with a three-way catalytic converter, which converts unburnt hydrocarbons, CO, and NOx into CO2, H2O, and N2. Diesel-powered cars, on the other hand, use a two-way catalytic converter, although the oxygen in their exhaust gas makes the conversion of NOx inefficient.
To drive more cleanly, one can consider buying a natural gas vehicle or an electric car, which does not rely on gasoline and thus does not produce exhaust gases.
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Frequently asked questions
Gasoline is the fuel that powers cars. It is one of the most energy-rich substances on Earth.
Gasoline is injected into the tank, then brought into the fuel line by a pump. It goes through a fuel filter to prevent clogging by removing waste, before reaching the fuel injectors, which combine air with fuel and deliver it into pistons. The air-fuel mixture is then ignited by a spark plug, eliciting combustion.
When gas is compressed, it heats up. The more it is compressed, the hotter it gets. The air-fuel mixture is compressed in the cylinder of the engine, which, when combined with the spark from the spark plug, ignites the mixture.
The exhaust system channels the exhaust gases from the engine out through the tailpipe. These gases are then converted into substances like nitrogen and carbon dioxide before being released into the atmosphere.
