What is divergent nozzle used for?
Convergent – Divergent nozzles are used to increase the flow of gas to supersonic speeds (as in the case of rockets). Their cross-sectional area first decreases and then increases.
When was nozzle invented?
The nozzle was developed by Swedish inventor Gustaf de Laval in 1888 for use on an impulse steam turbine. A de Laval nozzle was used in the first liquid fuel rocket engine designed and launched in 1926 by Robert Goddard, an American physicist and rocket pioneer.
What is the purpose of nozzle?
A nozzle is often a pipe or tube of varying cross sectional area, and it can be used to direct or modify the flow of a fluid (liquid or gas). Nozzles are frequently used to control the rate of flow, speed, direction, mass, shape, and/or the pressure of the stream that emerges from them.
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 converging nozzle?
Converging nozzles, as shown in Figure 1, are tubes with an area that decreases from the nozzle entry to the exit (or throat) of the nozzle. As the nozzle area decreases, the flow velocity increases, with the maximum flow velocity occurring at the nozzle throat.
Why do we use convergent nozzle?
A convergent nozzle is a nozzle that starts big and gets smaller-a decrease in cross-sectional area. As a fluid enters the smaller cross-section, it has to speed up due to the conservation of mass. To maintain a constant amount of fluid moving through the restricted portion of the nozzle, the fluid must move faster.
Why do rocket nozzles expand?
The nozzle is used to expand the exhaust gas from that high pressure to the very small external pressure. Pressure and temperature are related to velocity. Hence, reducing the pressure allows to gain in exhaust velocity and thus in thrust.
What is a perfectly expanded nozzle?
Ideal Expanded Nozzle: In an ideal nozzle that optimizes performance, the exit pressure (Pexit) will be equal to the ambient pressure of the external atmosphere (P¥). The flow in this case is perfectly expanded inside the nozzle and maximizes thrust.
Why do Jets have variable nozzles?
A variable area nozzle helps to adjust the exit pressure of the combustion gases to ambient pressure. When they leave the turbine, the combustion gases have still some remaining pressure which is converted into speed by a convergent contour of the nozzle.
Do nozzles increase pressure?
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.
What is optimum expansion?
It is under this condition, Pe=Pa where Pe is the pressure at the nozzle exit and Pa is the outside ambient pressure, that thrust is maximum and the nozzle is said to be adapted, also called optimum or correct expansion. When Pe is greater than Pa, the nozzle is under-extended.
What is a de Laval nozzle?
A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube that is pinched in the middle, making a carefully balanced, asymmetric hourglass shape. It is used to accelerate a compressible fluid to supersonic speeds in the axial (thrust) direction, by converting the thermal energy of the flow into kinetic energy.
What is the history of diverging nozzles?
Later, Swedish engineer Gustaf De Laval applied his own converging diverging nozzle design for use on his impulse turbine in the year 1888. Laval’s Convergent-Divergent nozzle was first applied in a rocket engine by Robert Goddard. Most modern rocket engines that employ hot gas combustion use de Laval nozzles.
Do de Laval nozzles choke at the throat?
A de Laval nozzle will only choke at the throat if the mass flow through the nozzle is sufficient, otherwise no supersonic flow is achieved. In addition, the pressure of the gas at the exit of the expansion portion of the exhaust of a nozzle must not be too low.
What type of nozzle is used in rocket engines?
Laval’s Convergent-Divergent nozzle was first applied in a rocket engine by Robert Goddard. Most modern rocket engines that employ hot gas combustion use de Laval nozzles. Its operation relies on the different properties of gases flowing at subsonic, sonic, and supersonic speeds.