What is an internal combustion engine?
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. The engine then converts some of the energy from the combustion into work. The engine consists of a fixed cylinder and a moving piston.
The defining characteristic of an internal combustion engine is that the expanding hot gases do useful work by acting directly to cause movement, such as by acting on pistons, rotors, or even pushing and moving the entire engine itself.
This is in contrast to external combustion engines, such as steam engines, which use the combustion process to heat a separate working fluid, typically water or steam, which in turn does work, for example by pushing on a steam-actuated piston.
The term internal combustion engine (ICE) is almost always used to refer specifically to reciprocating engines, rotary engines, and similar designs where combustion is intermittent. But continuous combustion engines such as jet engines, most rockets, and many gas turbines are also internal combustion engines.
Internal combustion engines are mainly seen in transportation. Several other uses are for any portable situation where you need a non-electric motor. The largest application in this situation would be an internal combustion engine driving an electrical generator. This allows you to use standard power tools powered by an internal combustion engine.
How does an internal combustion engine work?
Specifically, an internal-combustion engine is a heat engine in that it converts energy from the heat of burning gasoline into mechanical work, or torque. That torque is applied to the wheels to make the car move.
And unless you are driving an ancient two-stroke Saab (which sounds like an old chain saw and belches oily smoke out its exhaust), your engine works on the same basic principles whether you’re wheeling a Ford or a Ferrari.
Engines have pistons that move up and down inside metal tubes called cylinders. Imagine riding a bicycle: Your legs move up and down to turn the pedals.
Pistons are connected via rods (they’re like your shins) to a crankshaft, and they move up and down to spin the engine’s crankshaft, the same way your legs spin the bike’s—which in turn powers the bike’s drive wheel or car’s drive wheels.
Depending on the vehicle, there are typically between two and 12 cylinders in its engine, with a piston moving up and down in each.
The Four Strokes of a Four-Stroke Engine
In today’s most modern engines, gasoline is injected directly into the cylinders near the top of the compression stroke. (Other engines premix the air and fuel during the intake stroke.) In either case, just before the piston reaches the top of its travel, known as a top dead center, spark plugs ignite the air and fuel mixture.
The resulting expansion of hot, burning gases pushes the piston in the opposite direction (down) during the combustion stroke. This is the stroke that gets the wheels on your car rolling, just like when you push down on the pedals of a bike.
When the combustion stroke reaches the bottom dead center, exhaust valves open to allow the combustion gases to get pumped out of the engine (like a syringe expelling air) as the piston comes up again.
When the exhaust is expelled it continues through the car’s exhaust system before exiting the back of the vehicle the exhaust valves close at the top dead center, and the whole process starts over again.
Applications of internal combustion engines
Following are the application of the ic engine:
- IC engines are used in Road vehicles like scooters, motorcycles, buses, etc.
- It is also used in Aircraft.
- IC engine is commonly used in Motorboats.
- IC engine has great application in small machines, such as lawnmowers, chainsaws, and portable engine-generators.
Classification Of Internal Combustion Engine
Automobile engines are classified on the following basis.
1. Number of Cylinders
An engine may be a single-cylinder engine or a multi-cylinder engine. In a single-cylinder engine, there is only one cylinder, whereas in a multi-cylinder engine there is more than one cylinder.
The pistons of all the cylinders are connected to the common crankshaft. Therefore, engines may be:
- Single-cylinder Cylinder may be vertical or horizontal
- Multi-cylinder Cylinders may be vertical or inclined to the vertical plane.
2. Cylinder Arrangement
- In-line Cylinder Engine. The in-Line cylinder engine is a multi-cylinder engine, with all the cylinders arranged in one straight line. Each cylinder has an independent crank.
- V Cylinder Engine or V Engine. the V cylinder engine has two cylinders inclined at 90° to each other. The connecting rods are connected to a common crank pin. There is a common crank for both cylinders.
- V-8 Engine. In the V-8 engine design, there are two blocks inclined at 90° to each other and each block has four cylinders.
3. Valve Arrangement in Cylinder Head Assembly
- T-head Engine. In the T-head engine, the valves are arranged. The suction valve (SV) and the exhaust valve (EV) are on the cylinder block in opposite directions.
- F-head Engine. In the F-head engine, one valve is in the cylinder block and the other valve is in the cylinder head.
- L-head Engine. In the L-head engine, the suction and exhaust valves are arranged side by side in the cylinder block.
- I-head Engine. In the I-head engine, the suction and exhaust valves are arranged in the cylinder head.
- Overhead Engine. In the overhead engine, the suction and exhaust valves are arranged in the cylinder head. The cylinder head has a hemispherical shape. The difference between the I-head and overhead valve engines is that the I-head valves are actuated by pushrods whereas the overhead valves are actuated by the cams located above the cylinder head.
4. Cooling Methods
- Air-cooled Engines. Air-cooled engines have fins to radiate heat into the surrounding air. The fins are made triangular in shape as they increase the cooling surface area. These fins are made of aluminum, which is a good conductor of heat. Air-cooled engines run at higher temperatures because air is not a good conductor of heat.
- Water-cooled Engines. Water-cooled engines require the circulation of water. All automobile engines, which are water-cooled, are fitted with radiators. The radiator offers resistance to the flow of air through the passages in between the small diameter tubes carrying hot water. Therefore, an induced draught fan is provided at the back of the radiator. This fan creates the pressure difference required to get an increased flow of air. Similarly, to get pressure difference and to overcome the resistance in the water flow at the jackets of the engine, a water pump is provided which draws water from the radiator and forces it into the water jacket of the engine. Water is not allowed to rise to a higher temperature, as at higher temperatures scale formation takes place. Scale formation causes local heating due to poor cooling as scales are bad conductors of heat. Such local heating may lead to detonation, which may damage engine parts.
5. Fuel Used
- Gasoline Engine. In the gasoline engine, gasoline (petrol) is used as fuel. A mixture of gasoline and air is prepared outside the cylinder and an electric spark plug is used to initiate combustion of the compressed charge.
- Diesel Engine. The diesel engine utilizes a compressed mixture of air and diesel prepared inside the cylinder as fuel. The heat of compression is utilized to initiate the combustion of the mixture.
- Gas Engine. In the gas engine, combustible gases are used as fuel. These engines are not commonly used in automobiles.
6. Thermodynamic Cycles
Engines may be classified as follows based on the thermodynamic cycle used:
- Constant volume combustion cycle engine, which is also called Otto cycle engine.
- Constant pressure combustion cycle engine, which is also called Diesel cycle engine.
- A mixed cycle engine has partial combustion at constant volume and partial combustion at constant pressure.
7. Mechanical Cycles
- Two-stroke Cycle Engine. The two-stroke engines complete a thermodynamic cycle in two strokes of the piston (one revolution of the crank).
- Four-stroke Cycle Engine. The engine which completes its thermodynamic cycle in four strokes of the piston (two revolutions of the crank) is a four-stroke cycle engine.
8. Ignition System
- Spark Ignition Engine. A spark-ignition engine is either a gasoline engine or a gas engine. The electrical energy required to produce a spark in the spark plug is obtained either from a battery or a magneto.
- Compression-Ignition. Engine Compression ignition engines are diesel engines in which air is highly compressed to raise its temperature and initiate combustion when diesel fuel is injected.
9. Lubrication Systems
Three systems for lubricating the moving engine parts are used:
- Petrol lubrication system
- Wet sump lubrication system
- Dry sump lubrication system
A petrol lubrication system is also known as a mist lubrication system. This system is used in two-stroke cycle gasoline engines. The wet-sump lubrication system is of two types: splash lubrication and pressure lubrication system. These systems are used in four-stroke cycle automobile engines. A dry-sump lubrication system is used in heavy-duty engines.