[MGF]

Hi guys,
I know that this item has been discussed deeply in several previous posts but I haven't find there any suggestion which fits with my own problem so I hope not to annoying you and to find someone who can help me.
Please find the attached .png file named "geometry" which shows what I need to mesh. This geometry will be used both for a CFX and a Fluent simulation where a hot gas (let's say O2) will enter the channels and flow along the pipe. I attached also two pictures which depict my blocking strategy. Has anybody got a better solution?
I performed no smoothing. I just moved some vertices to obtain a mesh size as uniform as possible. I checked the mesh volume and found no negative volumes as you can see from the figure "volume_check" but had some problems with volume orientation which ICEM could not fix (see "volume_orient.png"). The quality for the elements highlighted in figure "volume_check" is poor but not negative.
I tried to run my simulation with this mesh but CFX gave me the following error:

+--------------------------------------------------------------------+
| ERROR #002100011 has occurred in subroutine cVolSec. |
| Message: |
| A negative SECTOR volume has been detected. Execution will proceed |
| but this is a possible cause of robustness problems. |
| The location of the first negative volume is reported below. |
| Volume : -0.4257E-14 |
| Location : ( -0.51447E-02, 0.28233E-01, -0.12739E-01) |
| This warning may be made fatal by setting the expert parameter |
| 'negative volume option = 1'. |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #002100012 has occurred in subroutine cVolSec. |
| Message: |
| A negative ELEMENT volume has been detected. This is a fatal |
| error and execution will be terminated. The location of the first |
| negative volume is reported below. |
| Volume : -0.4237E-12 |
| Location : ( -0.43662E-02, 0.27965E-01, -0.13327E-01) |
+--------------------------------------------------------------------+

Does anyone have any suggestion about how to fix the problem?
Thanks in advance for any help.