16-08-2014, 10:37 AM
Project Report On CFD Analysis of Conical Nozzle for Mach 3 at Various Angles of Diverrgence with Fluent Software
CFD Analysis of Conical.pdf (Size: 445.96 KB / Downloads: 28)
Abstract
Numerical study has been conducted to
understand the gas flows in a conical nozzle at different degree
of angle using 2 dimensional axi-symmetric models, which
solves the governing equations by a control volume method. The
nozzle geometry co-ordinates are taken by using of method of
characteristics which usually designed for De-Laval nozzle. The
present study is aimed at investigating the supersonic flow in
conical nozzle for Mach 3 at various degree of angle. The throat
diameter and exit diameter is same for all nozzles. The flow is
simulated using Fluent software. The flow parameters, like
pressure ratio, Area of nozzle exit ratio, and the Mach number
of the flow at the nozzle exit is defined prior to the simulation.
The result shows the variation in the Mach no., pressure ratio.
For 40 angles the Mach number at exit is very low compared to
other nozzles and the turbulence intensity is very high for 160 at
exit and it is nearly 3.045e+05. While when the angle is 80 the
mach number at nozzle exit is 2.91 and same as 120 angle but
an angle 160 it gives the mach number at nozzle exit is 2.92 and
it is lowest at an angle 40. The degree of angle for conical nozzle
can be large as 12 to 18 degree maximum so for maximum
thrust we can go with 120 or 160 conical nozzle.
INTRODUCTION
Swedish engineer of French descent who, in trying to
develop a more efficient steam engine, designed a turbine
that was turned by jets of steam. The critical component – the
one in which heat energy of the hot high-pressure steam from
the boiler was converted into kinetic energy – was the nozzle
from which the jet blew onto the wheel. De Laval found that
the most efficient conversion occurred when the nozzle first
narrowed, increasing the speed of the jet to the speed of
sound, and then expanded again. Above the speed of sound
(but not below it) this expansion caused a further increase in
the speed of the jet and led to a very efficient conversion of
heat energy to motion. The theory of air resistance was first
proposed by Sir Isaac Newton in 1726. According to him, an
aerodynamic force depends on the density and velocity of the
fluid, and the shape and the size of the displacing object.
Newton’s theory was soon followed by other theoretical
MATERIAL AND METHODS MATHEMATICAL MODEL
endent and the independent variables and the relevant
parameters that describe some physical phenomenon.
Typically, a mathematical model consists of differential
equations that govern the behavior of the physical system,
and the associated boundary conditions.
To start with fluent, it is necessary to know if the meshed
geometry is correct, so is checked. To ensue with, we are to
define the model, material, operating condition and boundary
condition. Models are to be set in order to define if any
energy equation is dealt with our study, if the flow is
viscous…etc. We have chosen coupled solver, 2d implicit,
absolute velocity formulation, cell based gradient option,
superficial velocity porous formulation. As our flow is dealt
with energy equation so is necessary to check them up. The
material is selected as air and the density as ideal gas to make
the solution simpler. Under the solve command the control is
selected for limiting the pressure to a maximum of 5e+7 and
minimum of 1e+4. The initialization of value is computed
from the inlet. It is also necessary to select the appropriate
approximation required in the residual command under
monitors and check in plot to visualize the progress of
iteration. Once every parameter is described the iteration is
performed till the value gets converged to required
approximation. The figures can be plotted between position
in x-axis and any other function in y-axis from plot command
or else to view vectors, contours or grid display command is
to be chosen.
TOTAL TEMPERATURE
The total temperature almost remains a constant in the inlet
up to the throat after which it tends to increase. Near the walls
the temperature decreases to 5.92e+02 K. In the inlet and the
throat the temperature is 6.00e+02 K. After the throat, the
temperature increases to 6.03e+02 K at the exit. As we move
from the centre vertically upwards at the exit, there is
variation. At the centre it is 6.02e+02 K, at the walls it is
5.92e+02 K and moving inward a little bit from the wall the
temperature reaches a maximum of 6.03+02 K.
VELOCITY MAGNITUDE
There is symmetric flow as observed from the above figure.
There is a constant increase in the velocity magnitude of the
fluid as we move from the inlet of the convergent section
(=1.74e+02 m/s) to the throat (=3.92e+02 m/s) and to the exit
of the divergent section (=8.70e+02 m/s). The flow is
turbulent, so near the wall flow separation takes place
TURBULENT INTENSITY
The turbulent intensity at the convergent section is very
low (=1.04e+03 %). Almost till the throat it remains almost a
constant. At the throat there is a very small increase to
1.25e+03 %. As soon as it crosses the throat, there is a sudden
increase in the turbulent intensity due to the sudden increase
in the area. As we move towards the exit, there is a small
patch in the centre where the turbulent intensity increases
(2.08e+03 %) and then as the fluid stabilizes near the exit,
there is a decrease in the turbulent intensity (1.87e+03 %).
Near the walls the turbulent intensity is high due to the
reversals of flow. At the exit near the walls the turbulent
intensity reaches a maximum (=4.97e+03 %).
CONCLUSION
It is observed that the nozzle which designed for, flow
travel along with the direction and at throat above default
angle Mach number is 1.03
while at 40
Mach number is 1.01 and at 7.1285730
Mach
number is 1.02. From Default angle Mach number is
increasing up to 2.917 at nozzle exit while for 40
the Mach
number at exit is nearly 2.88. At the throat the velocity
magnitude around same for all degree of angle and it is 218
m/s. The divergence loss is very low for 120
and160 for which
the nozzle is designed. Near the wall, the Mach number is
decreasing for all the nozzles. This is due to the viscosity and
turbulence in the fluid. For 40
angle the Mach number at exit
is very low compared to other nozzles and the turbulence
intensity is very high for 160 at exit and it is nearly
3.045e+05. While when the angle is 80 the mach number at
nozzle exit is 2.91 and same as 120 angle but an angle 160 it
gives the mach number at nozzle exit is 2.92 and it is lowest
at an angle 40. The degree of angle for conical nozzle can be
large as 12 to 18 degree maximum so for maximum thrust we
can go with 120
or 160
conical nozzle.