UNDERSTANDING HOW IC AIRCRAFT ENGINE OPERATES
If you are wondering what was powering airplanes before the invention and popular use of jet engines came into existence, this post has the answer.
First of all, the early aircraft was powered by simple reciprocating internal combustion engines of various designs according to the manufacturer.
The use of internal combustion engines to power aircraft lasted for decades and that limited the power of aircraft to be a low weight flying machine that could carry only few kilogram or a ton weight of load to fly.
Though sophisticated inventions and improvements in the reciprocating internal combustion engines came up later to boost the aircraft capacities their best could not match with the power provided by the turbine engines which is a later invention that gave birth to the jet engines used in powering of modern aircraft.
Before the jet age, reciprocating internal combustion engines played vital roles in providing power to almost all machines used in industries as well as automobiles and aircrafts.
From airplanes to helicopters the engine stood as the reliable source of power in areas high power with lesser weight is of great demand.
Unlike its main competitor then which is steam engines that are bulky, less efficient, and produce lesser power, based on its disadvantages, the steam engines were quickly displaced by the internal combustion engines.
Currently, internal combustion engines still play vital role in powering most of the road vehicles, ferryboats, hovercrafts, and auto bikes, etc. notwithstanding the steady rising of potential competitors such as the rechargeable energy in the form of battery cells example is lithium ion battery cells.
And the use of improved solar cells panels, as well as the nuclear reactors.
HOW AIRCRAFT’S INTERNAL COMBUSTION ENGINE OPERATES
The working principle of all internal combustion aircraft engine is the same. The principle is based on the basic principle of the combustion of fuel in the internal combustion engines.
The engine operates in a four stroke cycles which are: The Suction stroke, the compression stroke, the Power stroke, and the exhaust stroke.
The engine rotates its central shaft at great speed up to or more than 5000 rotation per minute through the transmitted motion received from the piston rod.
The piston rod reciprocates to and fro inside a cylinder situated in the engine and transmits the reciprocating motion to the crankshaft bearing the central shaft of the engine.
This is possible through flexible joint arrangement between the bottom part of the piston rod and a section of the crankshaft.
At the top end of the piston rod is a piston fixed to it with a flexible joint arrangement.
The piston is like a round tin of milk or drinking cup that closely sized the cylinder while two or three metal rings are fixed on the outer section of the piston to complete the small clearance between the piston and the cylinder wall such that it makes closed contact with the cylinder wall.
At the top of the cylinder wall are ignition plug, fuel injector, and two valves. One of the valves remain closed when the other is open and vice versa.
The Suction Stroke
The suction stroke is the beginning of the whole action. It sets the engine into motion and without it nothing would commence in the first place. It begins when the piston is forced to move downwards either manually or using an electric motor.
As the piston travels downwards, it will create a vacuum in the space between piston head and the top of the cylinder (this space is known as the combustion chamber) which will force one of the valve to open (the suction valve) the valve allows inflow of dry air and fuel into the combustion chamber in some designs only the air flows in.
In the designs that allow only dry air to flow in a fuel injector injects specific volume of fuel into the chamber at the completion of the suction stroke.
However, the volume of air that flows into the space is determined by the travelling length of the cylinder and distance traveled by the piston downwards as well as the opening size of the valve, this is a great factor that helps to boost the power of the engine and its efficiency.
The Compression Stroke
The compression stroke commences after the suction stroke. As the piston reaches its lowest level in the cylinder, it will start moving upwards to the top of the cylinder.
At this point the two valves at the top of the cylinder will remain closed. This will allow the piston to compress the dry air and injected fuel in the space towards the top of the cylinder.
This will cause the air to become extremely hot and high pressure will be created due to the compression.
This action is very important in achieving great power from the engine.
As the piston reaches the top of the cylinder only tiny space is left between the cylinder top and the piston top and that space bears the compressed hot air and fuel.
At this stage the compression stroke has been completed.
The Power stroke
The power stroke is the stroke that generates power in the engine. It proceeds after the compression stroke.
During the power stroke, the ignition plug (as in the case spark-ignition engine) will produce a spark of electric current which will cause tremendous explosion in the tiny space containing the compressed hot air and the fuel in it.
The kinetic energy generated as a result of the explosion will force the piston to go downwards towards the bottom of the cylinder, during this time the two valves at the top of the cylinder remain closed.
As the piston travels downward with high kinetic energy created from the explosive combustion of the fuel and air mixture, it used the force to push the piston rod downwards which then force the crankshaft section to move downwards as well.
As the crankshaft moves downwards, the counterweight balance in it will force the crankshaft to complete the 180 degrees rotation created by the piston rod to 360 degrees rotation. Thus forcing the piston rod to return back to the top position in the cylinder.
The power stroke is what really keeps the engine shaft rotating and the energy from it helps to complete other strokes effortlessly.
The exhaust Stroke
This is the last stroke of internal combustion engines used in aircraft and other applications. As the crankshaft’s rotation forces the piston to return to the top of the cylinder, the exhaust valve will be opened to allow evacuation of burnt gas (carbon monoxide).
The upwards travel of the piston will force all the burnt gases to escape through the exhaust valve to the atmosphere.
THE DESIGN FEATURES OF INTERNAL COMBUSTION ENGINE USED IN POWERING AIRCRAFT
Though all internal combustion engines work in the same principle, their designs are not the same. There are over fifty designs of internal combustion engines in existence and each design focus on its specific purpose and area of application.
For instance, the IC engine meant to power a power bike is not the same with the one powering cars. The one powering water boats is not the same as the one powering aircraft.
By design, IC engines powering aircraft has circular shape design. The circular shape allows it to have a central shaft that will be rotating the aircraft blades.
The cylinders are arranged along the circular paths as well as their piston. In the sample shown below in a video, the engine has nine combustion chambers arranged along its circular paths.
It is design in such a way that high rotational power can be obtained through properly arranged continuous power strokes from the nine combustion chambers surrounding the central shaft.
The power strokes are sent to the shaft through the piston rods attached to each chamber.
