Design and CFD Flow Analysis of CD Nozzle

A device that controls the speed of the fluid flow, directions, and flow characteristics is a Nozzle. The nozzle is designed like a pipe with a non-uniform cross-section. This design helps in controlling the velocity, flow rate, pressure ratio, direction, etc. 

Flow characteristics of the nozzle section can be varied with the variation in pressure difference at the outlet and the inlet sections. 

A CD nozzle or convergent-divergent nozzle is shaped like a tube with two bulging ends and a narrow section in the middle. This structure/design gives a balanced shape for the nozzle. Nozzle speeds up hot, pressurized gas passing through it in the axial (thrust) direction, by converting the heat energy of the flow into kinetic energy. A CD nozzle is of most importance to increase the kinetic energy of the medium. 

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But, during this increase in kinetic energy, there is a drop in internal energy and pressure. Due to the demand for high-performance propulsion engines like the rocket has led to the critical assessment of its engine subsystems with the intent of minimizing losses. 

The main losses which are seen in this nozzle are flow rate, speed, pressure, etc. and these are controlled by the nozzle by sending this to the exhaust system. Thus, the main functions of the nozzle are to utilize waste energy and to use it to create pressure that lifts the body.

DESIGN: 

The nozzle’s asymmetric configuration controls the direction and shape and also speeds up the outlet gases. The CD nozzle contains three parts, they are: 

• Converging section 
• Throat and 
• Diverging section 

The converging section of the CD nozzle connects the gas or fluid chamber. At the converging part, the high-pressure gas loses its pressure energy and gains kinetic energy. The pressure drop is due to Bernoulli's principle and the law of conservation of mass. As we know, the force of incoming flow is greater than the throat mass flow rate which increases the flow rate at the convergent section. 

The middle narrow section is the throat section. The throat is the narrowest and the smallest of all the sections in the nozzle.

The throat is the connecting part between the inlet and outlets of the CD nozzle. The Diverging section is for the outlet of the gas which comes out with high pressure and velocity which lifts the object and creates upthrust. 

ANALYSIS: 

Analysis done by using Ansys helps us to know the performance of the nozzle.

• CFD simulation code allows the detailed study of analyzing the performance characteristics of thermo-fluid properties such as the pressure, speed, velocity, temperature, mass flow rate, etc. of an aero-engine nozzle. 
• These parameters of the engine are in charge of maximizing the kinetic energy of the fluid by utilizing the heat and pressure in the combustion chamber as they pass through the nozzle. 
• Yet, one significant challenge is the increase in engine weight as a result of the use of a convergent-divergent nozzle. 
• The reduction in pressure implies that the weight is reduced as it depends on the weight and the area of the body. Hence, if weight decreases it implies that pressure will decrease as well and vice versa.

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Design and CFD Flow Analysis of CD Nozzle