What is over expansion in nozzle?

When an overexpanded flow passes through a nozzle, the higher atmospheric pressure causes it to squeeze back inward and separate from the walls of the nozzle. In this case, the flow continues to expand outward after it has exited the nozzle.

What does the atmospheric pressure have to do with the size of the bell nozzle?

Atmospheric pressure restricts the expansion of the exhaust gas at low altitudes so the efficiency is much higher at low altitudes . At low altitudes, a vehicle can saves 25-30% more fuel by using a dual bell nozzle.

What is the meaning of over expansion?

overexpansion
Definition of overexpansion : excessive expansion : the act or an instance of expanding too much or too quickly … by 1946 the firm had collapsed and was closed, a victim of overexpansion …—

What is nozzle expansion ratio?

[′näz·əl ik′pan·shən ‚rā·shō] (design engineering) Ratio of the cross-sectional area for gas flow at the exit of a nozzle to the cross-sectional area available for gas flow at the throat.

What is converging diverging nozzle?

A nozzle is a relatively simple device, just a specially shaped tube through which hot gases flow. This nozzle configuration is called a convergent-divergent, or CD, nozzle. In a CD nozzle, the hot exhaust leaves the combustion chamber and converges down to the minimum area, or throat, of the nozzle.

Why does flow separation occur?

Separation occurs due to an adverse pressure gradient encountered as the flow expands, causing an extended region of separated flow. The part of the flow that separates the recirculating flow and the flow through the central region of the duct is called the dividing streamline.

How does the total thrust vary with an extendable nozzle?

How does the total thrust vary with an extendable nozzle? Explanation: Initially as the nozzle is extended, thrust keeps increasing. This is because of the rate of increase in exhaust velocity being high compared to the decrease in exit pressure. Total thrust = 60 + 2.53 = 62.53 N.

Is expansive a real word?

having a wide range or extent; comprehensive; extensive: expansive mountain scenery.

How does an Aerospike engine work?

The idea behind the aerospike design is that at low altitude the ambient pressure compresses the exhaust against the spike. As the vehicle climbs to higher altitudes, the air pressure holding the exhaust against the spike decreases, as does the drag in front of the vehicle.