For most of us, a car is something we fill up with gas and use to get us from point A to point B. But have you ever stopped to ask yourself: “How does it work?” Unless you already have an electric vehicle as your daily car, the allure of “how car engine works” lies in the internal combustion engine roaring under the bonnet.
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How Car Engine Works Exactly
More specifically, an internal combustion engine is a heat engine because it converts energy from the heat of burning gasoline into mechanical work, or torque. But, how car engine works gradually?
This torque is transferred to the wheels to propel the car. Unless you’re driving an old Saab with a two-stroke engine (that sounds like an old chainsaw and has oily smoke coming out of the exhaust), whether you’re driving a Ford or a Ferrari, engines work on the same basic principles.
An engine has pistons that move up and down inside metal tubes called cylinders. Imagine you’re riding a bicycle. Your feet move up and down to turn the pedals. The pistons are connected to the crankshaft through rods (like shins) and move up and down to turn the engine’s crankshaft, just as your feet turn the crankshaft of a bicycle, which in turn turns the drive wheels of a bicycle or drive the wheels of a car.
Depending on the vehicle, engines usually have between 2 and 12 cylinders, each of which moves up and down.
Where does the power in an engine come from?
What moves the pistons up and down are thousands of small, controlled explosions per minute caused by fuel mixing with oxygen and igniting the mixture. Each ignition of fuel is called a combustion or work cycle. The heat and expansion of gases from these small explosions push the pistons down in the cylinders.
Most modern internal combustion engines (we’ll focus on gasoline engines for simplicity) are four-stroke engines. In addition to the combustion stroke, which forces the piston down from the top of the cylinder, there are three other strokes: intake, compression, and exhaust. The engine needs air (i.e. oxygen) to burn the fuel.
During the intake stroke, a valve opens and acts like a syringe as the piston moves downward, drawing in surrounding air through the engine’s intake system. When the piston reaches the bottom of its stroke, the intake valve closes, effectively closing the cylinder and commencing the compression stroke, which travels in the opposite direction to the intake stroke.
The upward movement of the piston compresses the aspirated charge.
Four-Stroke in a Four-Stroke Engine
In most modern engines today, gasoline is injected directly into the cylinder near the top of the compression stroke. (Other engines premix the air and fuel during the intake stroke.) In either case, a spark plug ignites the mixture just before the piston reaches the highest point of its stroke, called the top dead centre.
The resulting expansion of the hot combustion gases pushes the piston in the opposite direction (downward) during the combustion stroke. This is the beat that turns the wheels of a car, just like when you pedal a bicycle.
When the combustion stroke reaches the bottom dead centre, the exhaust valve opens and the burnt gases are expelled from the engine (like a syringe expelling air) while the piston rises. Once the exhaust gases are expelled, they continue to flow through the car’s exhaust system before exiting the rear of the vehicle.
The exhaust valve closes at the top dead center and the whole process begins again.
In a multi-cylinder car engine, the combustion strokes do not occur simultaneously, and the cycles of the individual cylinders are offset from one another and evenly distributed so that the engine runs as balanced and smooth as possible. But not all engines are the same; they come in all different shapes and sizes.
How Car Engine Works (Details)
Most car engines have cylinders arranged in a straight line, such as an inline-4, or two in-line cylinders combined in a V-shape, such as a V6 or V8 engine. Engines are also classified by their size, or displacement, which is the total volume of the engine’s cylinders. Different Engine Types, Of course, there are exceptions and small differences among commercially available internal combustion engines.
For example, Atkinson cycle engines change the valve timing to produce a more efficient but less powerful engine. Turbochargers and superchargers, which fall under the turbocharger option category, pump additional air into the engine, making more oxygen available and increasing the amount of fuel that can be burned.
The result is more power when you need it and increased efficiency when power is not needed. But no matter what kind of engine it is, as long as it’s an internal combustion engine, the way it works is essentially the same. And now you know her.
How do we get energy from oil?
Cars, trucks, trains, ships, planes — they all run on petroleum fuel. Petroleum, also known as “crude oil,” is a dark, energy-rich liquid found deep underground that became the world’s primary source of energy in the 20th century.
After it’s pumped to the surface, it’s transported by ship or pipeline to refineries, where it’s separated into gasoline, kerosene, diesel fuel, and all kinds of other petrochemicals that are used to make everything from paint to plastics. Petroleum fuels are made from hydrocarbons.
The molecules inside are mostly made up of carbon and hydrogen atoms (with a few other elements, like oxygen, bound to them). Wood, paper, and coal also contain hydrocarbons. Simply burn hydrocarbons to convert them into usable energy. When hydrocarbons are burned in the air, the molecules split apart.
The carbon and hydrogen combine with oxygen from the air to form carbon dioxide gas and water, and the energy that was holding the molecules together is released as heat. This process, called combustion, releases enormous amounts of energy. When you sit around a campfire and warm yourself by the flames, you’re absorbing energy generated by billions of molecules breaking and splitting apart.
People have been burning hydrocarbons to generate energy for over a million years; that’s why fire was invented. But regular fires are usually very inefficient. When you grill sausages over a campfire, you waste an enormous amount of energy. The heat spreads in all directions.
Very little of it ends up in your cooking pot; even less gets into your food. Car engines are much more efficient; they waste less energy and put more of it into work. The clever thing about them is that they burn fuel in a closed container. Most of the heat energy released by the fuel is captured and converted into mechanical energy that can power your car.
How big do the cylinders need to be?
It’s not just how many cylinders a car has that matters, but how much force each cylinder can produce as it pushes the piston out. This depends on the size of the cylinders, which in turn depends on two important measurements: the diameter of the cylinder (called the bore) and the extension of the piston (the stroke).
The area of a circle is π x radius 2, and the inside diameter is twice as large, so the effective volume of a car’s cylinders is (π/4) x inside diameter x inside diameter x stroke. Physically speaking, the volume of a cylinder is determined by how much work the fuel does as it expands, how much energy it transfers to the piston, and (given how often this happens) how much power the car produces.
Therefore, bore and stroke are very important and that is why they are often listed in the technical data of a car engine along with the number of cylinders. These dimensions are often given in the form bore x stroke (for example, 90 x 86 mm means bore 90 mm, stroke 86 mm).
How can I build a cleaner engine?
There is no doubt that Otto’s gasoline engine was a great invention, but today it has become a victim of its success. With around one billion cars on the planet, vehicle pollution is a serious and growing problem. Carbon dioxide, released when fuel is burned, is also a major cause of global warming.
The solution could be electric cars, which get their energy from cleaner sources, or hybrid cars, which use a combination of electricity and gasoline.
So why do we still use gasoline?
- There’s a good reason why the vast majority of cars, trucks, and other vehicles on the planet are still powered by petroleum-based fuels like gasoline and diesel.
- Per kilogram (or litre), it has more energy than virtually any other substance, as the diagram here shows very clearly.
- In theory, batteries sound great, but there’s far more energy in petroleum fuels per kilogram.
How many cylinders does an engine need?
The problem with a four-stroke design is that the crankshaft is only driven by one cylinder out of the four stages. That’s why cars usually have at least four cylinders arranged to fire in time with each other.
At any one time, one cylinder goes through each of the four stages, so there’s always one cylinder driving the crankshaft and no power loss. In a 12-cylinder engine, at least three cylinders are driving the crankshaft at any one time. That’s why these engines are used in fast, powerful cars.
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