THE BEHAVIOUR OF THE EXHAUST

GASES EVICTED FROM THE SHIP

FUNNEL

PREPARED BY:

Yaşar GUL

M.Sc. Naval Architect

Delta Marine Engineering Co.

Ergin ESIRGEMEZ

B.Sc. Aeronautical Eng.

Delta Marine Engineering Co.

Problem Description

• The gases evicted from the ship funnel is moving inverse and through the

engine room, so that the people in the engine room are complaining about the

gases.

• We investigate the movement of the gases evicted from the exhaust of the ship

funnel by using commercial CFD Software FLUENT 6.0.

• We tried to design the funnel to avoid the inverse movement of the gases

Computational Aspects

• FLUENT CFD Software, based on finite volume

method, is used for all analyses.

• Species transport model is used to investigate the

movement of the gases.

• For viscous model, standart k-e model is chosen.

• Analyses are run in the PC which has dual

proccessor and 2 GB RAM.

• Fluent can model the species transport with or without

chemical reactions.

• In this work since the gases evicted from the funnel are

analyzed, specieaes transport model without chemical

reactions is used.

• For this model FLUENT predicts the local mass fraction of

each species, through the solution of a convection-

diffusion equation for the ith species.

• This conservation equation takes the folloing general form:

Theoretical Aspects

iY

( ) ( )iiiii

SRJYYt

++⋅−∇=⋅∇+∂

∂ rrυρρ

Theoretical Aspects

• Ri is the net rate of production by chemical reaction, Si is the rate of

creation by addition from the dispersed phase plus any user defined

sources, Ji is the diffusion flux of species i, which arises due to

concentration gradients.

ii,miYρDJ ∇−=

r

i

t

t

miiY

ScDJ ∇

+−=

µρ ,

r

An equation of this form will be solved for N-1 species, where N is the

total number of fluid phase chemical species present in the system, and the

Nth mass fraction is determined as one minus the sum of the N-1 solved

mass fractions.

for laminar flow

for turbulent flow

Solution Process

We have tree different cases for the funnel design

First Case Second Case Third Case

Find efficient model for

the same condition

Investigate the efficient

model for the different

condition

Model For The First Case

Figure 1. Grid for the superstructure (Initial Design)

Model For The Second Case

Figure 2. Grid for the superstructure (Second Design)

Model For The Third Case

Figure 3. Grid for the superstructure (Final Design)

Mesh and Analyze Summary

Table 1. Mesh summary for the models

Model Cells Faces Nodes

Initial Model 2257444 6763999 2255751

Second Model 2257444 6763063 2254884

Final Model 2257444 6763483 2255229

Table 2. Analyze Summary

Analyse Method Finite Volume Method

Analyze Type Species Transport

Turbulence Method Standart k-e

PC CPU*2, 1024 MB Ram

Computational Time 25 Hours

Boundary Condition

InletOutlet

Wall

Figure 4. Boundary Condition Type

Boundary Condition

Table 3. The ship velocities for each model

Model Ship Velocity

Initial Model 14 knots

Second Model 14 knots

Final Model 14 knots

Efficient Model (Final Model) 14, 12, 8, 0 knots

Table 4. Gases’ Velocities and Temperatrures

The Gases Evicted From Velocity Temperature

Machine Room 41 m/sn 277 C

Boiler room 6.4 m/sn 340 C

Table 5. Gas contents for air and exhaust gas

Air Exhaust Gas

O2 % 21 % 13

N2 % 79 % 75.8

CO2 % 5.45

H2O % 5.75

Initial Design Results

Figure 5. The gases’ behaviour for the initial design

Figures 6. Velocity Vectors at the different part of the funnel

Ship Velocity = 14 m/sn

Second Design Results

Figure 7. The gases’ behaviour for the second design

Figure 8. Velocity vectors in front of the funnel

Ship Velocity = 14 m/sn

Final Design Results

Figure 9. The gases’ behaviour for final design

Figure 10. Velocity vectors in front of the funnel

Ship Velocity = 14 m/sn

Ship Velocity = 12 m/sn

Ship Velocity = 8 m/sn