The internal combustion gasoline engine is one of today’s most prevalent and widely used machines. An engine is an old idea that has been refined over the years and can be found in today’s planes, trains and automobiles. The most common type of internal combustion engine is the reciprocating piston engine. The purpose of any engine is to convert the potential energy contained in the stored chemical fuel into kinetic energy to perform useful work.
The incoming energy of an internal combustion engine is gasoline which is a form of chemical energy. The potential chemical energy contained in the gasoline is mixed with air, ignited and converted into heat energy. The heat energy is converted into kinetic mechanical energy by the pistons and connecting rod rotating the engines crankshaft. Unfortunately, not all of the fuel’s chemical energy is converted or outputted to rotational mechanical kinetic energy. Of the 19,000 to 20,000 Btu’s per pound of gasoline, typically less than 1/3 heat ends up as useable horsepower that is applied to rotating the crankshaft. The rest of the heat energy from the combustion process and the heat from friction of the mechanical components is unusable, and is vented to the atmosphere via the radiator along with the fuel’s combustion byproducts which consist of carbon, carbon dioxide, carbon monoxide, nitrous oxide and water vapor.
The main mechanical components in an internal combustion engine are the cylinder(s) and reciprocating piston(s). The piston(s) are sized to fit snugly against the walls of the cylinder(s). The piston(s) slide up and down in the cylinder(s) and are connected to the crank shaft by a connecting rod. The process of converting the chemical energy contained in the fuel into mechanical energy begins when a mixture of air and gasoline is pumped into the cylinder from an opening and is put under extreme pressure. Once the pressure reaches its maximum compression, a spark ignites the fuel air mixture in the cylinders combustion chamber and the piston is forced down by the expanding gases which in turn cause the crankshaft to turn in a circular motion. The combustion process transforms the incoming chemical energy contained in the fuel into outgoing heat energy. Approximately 30 percent of the outgoing heat energy is transformed into mechanical energy and applied to rotate the crankshaft. The remaining output energy and combustion by products are unusable in the engines chemical to mechanical energy transformation and are vented to the atmosphere as waste byproducts.
This same process repeats over and over again in each of the cylinder(s) several thousand times each minute.
As the engines crankshaft revolves, it outputs the rotating mechanical energy to perform some type of useful work such as propelling a vehicle. However, an engine is only around 30% efficient. In cars, trucks, trains and motorcycles the pistons are used to turn the wheels to propel the vehicle. On planes and boats, the pistons are used to spin a propeller in air or water to propel the vehicle. On lawn equipment the pistons spin the wheels that propel the mower and spin a circular blade needed to cut grass, mulch materials such as grass, leaves, sticks and plants. Small industrial generators are usually 1 or 2 cylinders, and are used to create electricity.
Most internal combustion engines found in lawn equipment have only 1 cylinder. Small industrial generators are usually contain 1 or 2 cylinders, and are used to create electricity. Most motorcycles and small boats have 2 or 4 cylinders. Cars generally have between 4 and 8 cylinders. Trains and ships have a large number of cylinders, but they usually run on diesel fuel rather than gasoline. One gallon of Diesel fuel contains more potential chemical energy than one gallon of gasoline.
The parts of an internal combustion engine have very tight tolerances and are timed to hundredths of a second. If one of the parts is out of time, it’s likely the entire engine could fail. That’s why everything is controlled very precisely. Gasoline is stored in a sealed fuel tank. Air is sucked in by a carburetor and the two mix together. The proper ratio of gasoline is mixed with air for the engine to function properly. The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust.
As you can see internal combustion engines are today’s biggest source of making power for vehicles. Unfortunately engines output produce waste exhaust gasses as part of the combustion process. The exhaust gases contain carbon, carbon monoxide, carbon dioxide, nitrous oxide and water vapor which pollute the earth’s atmosphere and contribute to global warming. Predictions are that one day in the near future, many of today’s gasoline internal combustion engines will be replaced by hydrogen fuel cells and electric motors within the next 2-3 decades.