Under what conditions will the flow through a convergent-divergent nozzle become choked?

Under what conditions will the flow through a convergent-divergent nozzle become choked?

When the back pressure ratio is large enough, the flow within the entire device will be subsonic and isentropic. When the back pressure ratio reaches a critical value, the flow will become choked with subsonic flow in the converging section, sonic flow at the throat, and subsonic flow in the diverging section.

What is the condition at throat in 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. The throat size is chosen to choke the flow and set the mass flow rate through the system. The flow in the throat is sonic which means the Mach number is equal to one in the throat.

What is back pressure in convergent-divergent nozzle?

Gas flows from the chamber into the converging portion of the nozzle, past the throat, through the diverging portion and then exhausts into the ambient as a jet. The pressure of the ambient is referred to as the ‘back pressure’ and given the symbol pb.

What is convergent and divergent nozzle?

Convergent-divergent nozzle. An arrangement in which the forward portion of the nozzle is convergent, which increases the pressure of the exhaust gases, while the aft section is divergent to increase gas velocity to the supersonic speed and avoid losses from underexpansion.

When the back pressure of a nozzle is below the critical pressure the nozzle is said to be?

Explanation: When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be underdamping.

How does a de Laval nozzle work?

The gas flow through a de Laval nozzle is isentropic (gas entropy is nearly constant). As the gas exits the throat the increase in area allows for it to undergo a Joule-Thompson expansion wherein the gas expands at supersonic speeds from high to low pressure pushing the velocity of the mass flow beyond sonic speed.

How does the de Laval nozzle work?

When the back pressure of a nozzle is below the critical pressure the nozzle is it to be?

Does pressure increase in a nozzle?

In a convergent nozzle, there is an increase in velocity and a decrease in pressure, but we know that pressure is inversely proportional to area. To maintain a constant amount of fluid moving through the restricted portion of the nozzle, the fluid must move faster.

What is the critical pressure ratio for initially dry saturated steam?

The value of critical pressure ratio for initially dry saturated steam is. 0.5.

What is the value of critical pressure ratio for superheated steam?

0.5
The value of critical pressure ratio for superheated steam is. 0.5.

How does area of a De Laval nozzle vary with V V ratio where V is the flow velocity and v is the specific volume?

The area of a de Laval Nozzle is directly proportional to the ratio v/V, where v is the flow velocity and V is the specific volume. Explanation: For a de Laval Nozzle, the area is inversely proportional to the ratio v/V. This follows from the continuity equation.

What is a convergent divergent nozzle?

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. The throat size is chosen to choke the flow and set the mass flow rate through the system.

What is the minimum area of the air entering the nozzle?

Air enters the nozzle at stagnation pressure and temperature of 680 kPa and 370 k respectively. If the flow is of 5.2 cm 2, minimum area is 3.2 cm 2 and exit area of 3.87 cm 2. At inlet the a ir velocity 100 m/s, pressure 680 kPa, and temperature 345 k.

What is the throat area of a nozzle?

The nozzle’s throat area refers to the minimum cross sectional area of the constriction in a CD nozzle or in a verturi carburettor. It is in this area where the gas flow gains kinetic energy thus producing supersonic speed after passing through it (see figure 1).

When is the flow through the nozzle subsonic?

Figure 3a shows the flow through the nozzle when it is completely subsonic (i.e. the nozzle isn’t choked). The flow accelerates out of the chamber through the converging section, reaching its maximum (subsonic) speed at the throat.