# The aviation world is growing rapidly along with the development of propulsion. Initially, the aircraft was only driven by a piston engine that turned propellers, but along with the need for higher speed and performance, a gas-propulsion engine with a gas turbine working principle is now being intensively used for both large-scale aircraft (Boeing, Airbus etc.) as well as fighter aircraft up to high speed vessels (supersonic and hypersonic) which includes turbojets, turbofan, turboprop, turboshaft, ramjet and other modifications.
# Then, how do these machines work? to understand it, first we learn first how to work from turbojet. Turbojet has the main components Inlet, Compressor, Combustor, Turbine and Nozzle as shown below:
# How it works is as follows:
# - The air from the front of the plane goes into the turbojet through the inlet. This inlet is a diffuser, which is a part to convert high air velocity into high pressure by lowering speed. Keep in mind that the compressor will optimally work when the air entering low-speed.
# - Low-speed air and high pressure above then enter the compressor to be compressed or raised the pressure, this pressure increase is very high and tight, the higher the engine performance will be better. This pressure increase is accompanied by rising temperatures.
# - Once the air has high pressure and temperature, the air is mixed with fuel so it can easily burn and produce an explosion inside the combustion chamber. Unlike the piston engine, on the gas turbine, the spark plug is only done once at the start of the starter, much like turning on a gas stove.
# - This very hot and high-speed combustion air then drives the turbine. Turbine works to change the energy of heat and energy from the air speed becomes a very high rotation. The turbine is connected to the compressor, so the compressor can perform its function as the 1st explanation so that the machine will rotate continuously.
# - After passing through the turbine, the energy from the air is still quite high. The high pressure and temperature energy is converted into velocity energy using nozzle, out of the nozzle, the air has a very high speed to produce a thrust force or we are familiar with very high thrust as well. This style of thrust is used to drive the aircraft.
# As for, to improve the performance of the turbojet, made some modifications by adding components like the following:
# 1.**Afterburner**
# Afterburner is the fuel combustion made before it reaches the nozzle by utilizing the remaining hot gas turbine, so that the "bursts" of hot gas are directly utilized to push the plane which can be obtained very large thrust, although of course becomes more extravagant. Afterburner is commonly used for very high-speed combat aircraft.
# 2.**Turboprop**
# In addition to rotating the compressor, turboprop engines in turbine rotation are used to rotate propellers, resulting in higher engine efficiency at medium speed.
# This type of turbine is commonly used in speed aircraft and medium passenger capacity.
# 3.**Turboshaft**
# Synonymous with turboprop, turboshaft utilizes turbine spin to rotate shafts for other purposes, such as eg drive components, power plants, and others.
# 4.**Turbofan**
# This machine is also synonymous with turboprop, only turbine rotation is used to rotate the fan. In contrast to the propeller, the fan is inside the engine conduit and produces compression as well as for the compressor, so it is known by the pass ratio, ie the ratio of air through the core engine (turbine) with air not through the turbine. The higher the by-pass ratio, the engine will be more efficient at low speeds, it can be observed also that turboprop has a by-pass ratio that is much larger than the turbofan
# This turbofan is well-known for use in high-capacity, high-speed commercial jets, such as boeing and airbus, as it is efficient at high speeds and long distances.
# 5.**Ramjet**
# Unlike the above machines, ramjet only consists of inlet, combustion chamber and nozzle. This ramjet is used at very high speeds, at very high speeds that the air entering the inlet will be slowed so that the pressure and temperature will increase drastically, therefore no compressors are required. The extremely high pressure and temperature are then mixed with fuel and used immediately to produce high-speed air through the nozzle (note that there are no turbines in this system).
# From the above explanation, of course there is no machine "the best" and most efficient, but it depends on the conditions of work (height, speed, needs and others).
# *Source*: *Aero Engineering*
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