THE BEHAVIOUR OF THE EXHAUST GASES EVICTED FROM THE SHIP FUNNEL

Transcription

1 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.

2 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

3 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.

4 Theoretical Aspects 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, Y i through the solution of a convectiondiffusion equation for the ith species. This conservation equation takes the folloing general form: t r ( ρyi ) + ( ρυyi ) = Ji + Ri + Si r

5 Theoretical Aspects R i is the net rate of production by chemical reaction, S i is the rate of creation by addition from the dispersed phase plus any user defined sources, J i is the diffusion flux of species i, which arises due to concentration gradients. r J i r J i = ρd = i,m ρ Di, m Y i µ t + Yi Sc t for laminar flow for turbulent flow 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.

6 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

7 Model For The First Case Figure 1. Grid for the superstructure (Initial Design)

8 Model For The Second Case Figure 2. Grid for the superstructure (Second Design)

9 Model For The Third Case Figure 3. Grid for the superstructure (Final Design)

10 Mesh and Analyze Summary Table 1. Mesh summary for the models Model Cells Faces Nodes Initial Model Second Model Final Model Analyse Method Analyze Type Turbulence Method PC Computational Time Table 2. Analyze Summary Finite Volume Method Species Transport Standart k-e CPU*2, 1024 MB Ram 25 Hours

11 Boundary Condition Outlet Inlet Wall Figure 4. Boundary Condition Type

12 Boundary Condition Model Initial Model Second Model Final Model Efficient Model (Final Model) Table 3. The ship velocities for each model Ship Velocity 14 knots 14 knots 14 knots 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 O 2 % 21 % 13 N 2 % 79 % 75.8 CO 2 % 5.45 H 2 O % 5.75

13 Initial Design Results Figure 5. The gases behaviour for the initial design

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

15 Ship Velocity = 14 m/sn

16 Second Design Results Figure 7. The gases behaviour for the second design

17 Figure 8. Velocity vectors in front of the funnel

18 Ship Velocity = 14 m/sn

19 Final Design Results Figure 9. The gases behaviour for final design

20 Figure 10. Velocity vectors in front of the funnel

21 Ship Velocity = 14 m/sn

22 Ship Velocity = 12 m/sn

23 Ship Velocity = 8 m/sn