Why do rocket nozzles diverge?

When M > 1 i.e the speed of gas is greater than the speed of sound; when area decreases there is decrease in velocity. We should use converging nozzle up to M = 1 and then use diverging nozzle to further increase the speed of gas flow. Such nozzle is called a converging diverging nozzle.

Why are convergent-divergent nozzles used in rockets?

It is used to accelerate a hot, pressurized gas passing through it to a higher supersonic speed in the axial (thrust) direction, by converting the heat energy of the flow into kinetic energy. Because of this, the nozzle is widely used in some types of steam turbines and rocket engine nozzles.

What is the purpose of the nozzle at the end of the rocket?

A rocket engine uses a nozzle to accelerate hot exhaust to produce thrust as described by Newton’s third law of motion. The amount of thrust produced by the engine depends on the mass flow rate through the engine, the exit velocity of the flow, and the pressure at the exit of the engine.

Why are converging diverging nozzles used?

Convergent-divergent type of nozzles are mostly used for supersonic flows because it is impossible to create supersonic flows (mach number more than one) in convergent type of nozzle and therefore it restricts us to a limited amount of mass flow through a particular nozzle.

How do converging diverging nozzles work?

A converging diverging nozzle is placed after a subsonic combustion chamber to take the high temperature, high pressure gas, and transform it into an atmospheric pressure, high velocity gas that will provide thrust through its high momentum.

Why is the Mach number 1 at the throat?

When the nozzle isn’t choked, the flow through it is entirely subsonic and, if you lower the back pressure a little, the flow goes faster and the flow rate increases. As you lower the back pressure further the flow speed at the throat eventually reaches the speed of sound (Mach 1).

Why is the nozzle so important?

The nozzle is an important part of any rocket motor: it converts high pressure and high temperature(with slow net velocity) inside the combustion chamber into a high velocity, but low pressure. This is what high pressure is. The nozzle helps align the movement of the molecules to the same direction.

What is the purpose of a nozzle?

The primary function of a nozzle is to control flow rate and convert the spray liquid into droplets (via atomisation) that are of a suitable size for depositing on the intended target.

What is choked flow for a converging diverging nozzle?

Choked flow is a fluid dynamic condition associated with the venturi effect. When a flowing fluid at a given pressure and temperature passes through a constriction (such as the throat of a convergent-divergent nozzle or a valve in a pipe) into a lower pressure environment the fluid velocity increases.

Should we use a converging or diverging nozzle for rocket engines?

Since the velocity is dropping in the diverging section, we should not use a converging-diverging nozzle; instead only use the converging nozzle for the rocket engines. However, the gas flow in a converging-diverging nozzle is not as simple as we explained in the Venturi effect.

Why does the gas come out of a rocket nozzle outward?

Since the gas coming from the exit nozzle is at a higher pressure than the surrounding gas, the gas coming from the nozzle will expand outward as soon as it leaves the nozzle. This flow behavior is also inefficient, since some thrust force goes outward from the rocket instead of going in the opposite direction of the rocket flight.

How does a rocket engine work?

A rocket engine uses a nozzle to accelerate hot exhaust to produce thrust as described by Newton’s third law of motion. The amount of thrust produced by the engine depends on the mass flow rate through the engine, the exit velocity of the flow, and the pressure at the exit of the engine.

What is overextended flow in rocket engines?

However, the flow beyond the exit nozzle becomes a mixture of supersonic and subsonic flow, called overextended flow. During this operation, the nozzle is inefficient, but usually the rocket engines are designed in this mode. This interesting flow pattern can be seen in the following figure.