Nozzles perform very specific functions in machines. They help modify or direct gases or liquids, by controlling their rate of pressure, shape, mass, direction, speed and flow of a stream that passes through them. Nozzles are of significant use in the aeronautics industry, and the types used vary in size and design, to meet specific requirements.
Before looking at the nozzle types that are used by the aeronautics industry, lets quickly understand the purpose that nozzles serve in aeronautics.
Nozzles are tubes or pipes of varying cross-sectional area, used to modify or direct the flow of gases or fluids. Nozzles:
Produce kinetic energy by converting thermal energy in hot gas chambers, and direct it along the Nozzle axis.
Allow exhaust gasses to expand and push towards walls to produce thrust.
Allow maximization of exit velocity.
Types of nozzles used in aeronautics
Now that we know what nozzles actually do in aeronautics, lets take a look at the different types of nozzles used.
Low ratio nozzle: Predominantly used in civil aircrafts, and in some low-speed reconnaissance airplanes as well, low ratio nozzles are convergent-divergent nozzles. They have very low inlet-outlet pressure ratio, which prevents the machines from choking at low speeds. Also, they reduce the noise generated from combustion and are very reliable.
Ejector nozzle: This nozzle type is mostly used in jet propelled aircrafts, and is the simpler version of the variable exhaust nozzles, such as the iris nozzles. The spring-loaded petal design makes the ejector nozzles more reliable as well. However, they produce considerable secondary airflow drag, and are considered less efficient as compared to other, more advanced types of nozzles.
Iris nozzle: Falling into the category of variable exhaust nozzles, the iris nozzle is commonly used in fighter jet planes and bombers. They can dilate or shrink their contour through the flexible petal design. This flexible design prevents uneven distribution of pressure (termed as oblique shock) therefore maximizing performance. In fact, in some iris nozzle designs, the angle to aircraft (thrust vector) can also be changed, and air brakes added.
There are many other types of nozzles being considered in aeronautics, such as bell nozzles, aerospike nozzles, linear and annular nozzles, etc. But, they are under testing phase, and may be used in future generation aircrafts.
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What other kinds of nozzles do you know of, that are used in aeronautics industry? Share them with us in the comments below; wed love to hear from you as well.