Location of Air Intake Manifold

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Pengze
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Joined: Tue Sep 23, 2008 8:57 pm

Location of Air Intake Manifold

Postby Pengze » Fri Nov 16, 2012 11:33 pm

Air intake manifold.pdf
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Dear Gentlemen,
As per attached drawing, could anyone out there provide valuable comment regarding the location & positioning of the air intake manifold for a 4-stroke medium speed diesel engine.?
We are operating near the equator and with a seawater temperature of 32 deg C. for the main engine air cooler.
We are trying to lower down the engine exhaust temperatures.

1. This is related to the air intake temperature for the engine cylinders.
2. Is the proposal (the lower diagram) feasible and practical ?

Feel free to comment.
Thank you.

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Big Pete
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Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Location of Air Intake Manifold

Postby Big Pete » Sat Nov 17, 2012 1:36 am

Hi again Pengze,

I would definitly discuss this with the Engine Builders technical Department, just Google the engine designer to find their website and look for links to Technical Help, Service department, Installation or something similar, if you can contact anyone technical they will pass you on to the right people to help you. emails are free. When i have done this in the past I have always found people to be very helpful.
Should there be insulation on the partition between the air manifolds before and after the cooler??
If you modify the air inlet you will have to make sure that every part of the new manifold is larger in diameter than the old one, much larger if you fit any bends or elbows in it otherwise you will have an excessive pressure drop in the air manifold.
Do you have the correct air flow through the system? (Differential pressure across the cooler?? Turbine / compressor wheels cropped because of damage = reduced power? The faster the air flow the less heat will be absorbed by the air after the cooler.
What are the makers operating criteria for Tropical operation? Usually you would keep the air temperature after the cooler well over 40, nearer 50C to prevent condensation problems, when in the tropics.

Let us know how you get on.

BP
It is always better to ask a stupid question than to do a stupid thing.

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Big Pete
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Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Location of Air Intake Manifold

Postby Big Pete » Tue Nov 20, 2012 1:13 am

I also forgot to ask have you checked the air inlet valves on the cylinder heads? If they are leaking hot exhaust gas back into the air manifold it could have similar results.

BP
It is always better to ask a stupid question than to do a stupid thing.

Pengze
Mechanic
Posts: 60
Joined: Tue Sep 23, 2008 8:57 pm

Re: Location of Air Intake Manifold

Postby Pengze » Fri Nov 23, 2012 11:31 pm

Dear Sirs,
Firstly, the Japanese maker's service engineer did visited us in our office to discuss some problems but disappointed to say that they are not that helpful as some questions are still unanswered till today. He suggested us to consult with the China maker (under license from Japan) for follow up answers but then again they beat around the bush.
If I am not wrong, since we had a few sister ships having the same type & model of the engine, the operation parameters are okay and as expected, therefore the air inlet manifold should not have been a issue here.
If the air inlet valve is leaking, usually the air inlet manifold will glow red-hot at that particular unit and also will cause turbocharger surging. At the same time, there will be a high exhaust temperature due to poor combustion. Then will lead to inlet valve cut / holed.
Yes, the instruction manual says air inlet temperature to the engine should be between 40~50 deg C but like our case we normally operate at between 38 ~ 42 deg C without condensation.
Thank you for your opinions.

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Big Pete
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Joined: Fri Apr 24, 2009 11:18 pm
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Re: Location of Air Intake Manifold

Postby Big Pete » Sun Nov 25, 2012 12:42 am

Hi again Pengze,

If you have the same type of engine on other ships, and they do not have this problem, it is likely that there is a specific problem relating to this one ship only. The design of the air/exhaust manifold is common to all the engines and so should not be a problem.
When the engine is designed, the flow through th exhaust and inlet manifold will almost certainly have been computer modelled and extensive testing would have been carried out on the prototype engine to ensure that there were no problems, such as pressure pulses, that might effect the operation of the engine or turbocharger. If you fabricate and fit a new air manifold I would suggest that you allow plenty of time for Engine Trials and possibly refitting the old manifold, if you have to.

Big Pete
It is always better to ask a stupid question than to do a stupid thing.


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