Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rating: Thread Rating: 4 votes, 5.00 average. Display Modes
Old 18-04-2012, 06:48   #1
Registered User

Join Date: Dec 2007
Location: Echo Bay, Ontario
Boat: 40' steel Trawler
Posts: 31
Perkins diesel air intake volume

Hi Folks
I don't think my Perkins diesels are breathing very well. Does someone
have a calculation for determining the size of an intake for a given
volume of air?

I have twin Perkins diesel T6-354's in my trawler and have read that they require 400 cfm of air @ X-rpm. Can anyone tell me what size of intake
pipe would be required to alow them to breath properly?

Your help with this little dilema would be much appreciated. Thankyou
__________________

__________________
Capt Nemo is offline   Reply With Quote
Old 18-04-2012, 07:29   #2
Senior Cruiser
 
Rocketman's Avatar

Cruisers Forum Supporter

Join Date: Apr 2011
Location: Naples, FL
Boat: Beneteau Oceanis 400
Posts: 668
Re: Perkins diesel air intake volume

A little more information may be needed to try to determine what is going on. Why do you think you are having an air intake problem? Did you or someone else change the air intake on your engines? Normally the air intake is open to the engine room and draws air from the room, the room vented so air can get in from outside, is your situation different? What are the engines doing that makes you think it is a air intake problem? Normally with diesel engines, if the engines are not running as well as you think they should, the first place to look is at the fuel system.
__________________

__________________
Rocketman is offline   Reply With Quote
Old 18-04-2012, 09:48   #3
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,593
Images: 240
Re: Perkins diesel air intake volume

I suspect you may require About 400 cfm per engine.

A simple calculation for cfm is to multiple the horsepower of your engine by 2.5.
Hence (2 x 150HP) x 2.5 = 750 cfm.

An 80 square inch of Free Area* louvre will deliver 400 cfm @ 720 fpm velocity**.
A 144 square inch of Free Area* louvre will deliver 750 cfm @ 750 fpm.

Dave Gerr determines the minimum vent area (in square inches) by dividing the engine horsepower by 3.3, then adding a 10-percent buffer.
Hence (300 HP ÷ 3.3) x 1.1 = 100 square inches

His smaller louvre, will have a higher velocity (750 cfm @ 1080 fpm), thus be a little noisier.

* If youy don't know the Free Area of your louvres, assume 50% of gross area, for estimation.

** 750 - 850 fpm are considered good "residential" velocities.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is online now   Reply With Quote
Old 18-04-2012, 09:52   #4
Registered User

Join Date: Dec 2007
Location: Echo Bay, Ontario
Boat: 40' steel Trawler
Posts: 31
Re: Perkins diesel air intake volume

Hi Rocketman

Thanks for your timely reply.

The reason for my question is this.

I just purchased this 42 foot steel trawler 5 weeks ago, and am doing some refitting work to prepare for the boating season.
While investigating my new engine room, I noticed that the only fresh
air intake into the room was from any place where air could be Sucked in from other areas through cracks or crevices. NOT a healthy breathing environment for 2 turbo diesel engines. I am somewhat shocked that a fresh air intake was not provided for these engines, or the engine room for that matter. So I am going to install fresh air induction to the engine room
via duct-work. I believe this would make for happier engine breathing and
a healthier engine room. The dimensions of engine room are 6' H x 6' L x 12' W (beam), with twin T6-354 Perkins Diesels in it, and soon to have a small diesel genset installed.
__________________
Capt Nemo is offline   Reply With Quote
Old 18-04-2012, 10:06   #5
Registered User
 
Astrid's Avatar

Join Date: Oct 2008
Location: Northern British Columbia, part of the time in Prince Rupert and part of the time on Moresby Island.
Boat: 50-ft steel Ketch
Posts: 1,885
Send a message via MSN to Astrid Send a message via Yahoo to Astrid
Re: Perkins diesel air intake volume

You should have a dedicated intake for the engine room, not drawing air from other compartments, together with an air exhaust for the engine room.
__________________
'Tis evening on the moorland free,The starlit wave is still: Home is the sailor from the sea, The hunter from the hill.
Astrid is offline   Reply With Quote
Old 18-04-2012, 10:35   #6
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,593
Images: 240
Re: Perkins diesel air intake volume

I recommend that you consult an engine room ventilation expert, such as:
Delta T Systems Engineered Marine Engine Room Ventilation

In addition to Combustion* Air (2 propulsion + 1 generator engine), you’ll also need Cooling* or Ventilation Air (heat rejection) to maintain a delta T** of 30 degrees F or less.

* Cooling air refers to the flow of air that removes radiant heat from the engine, generator, and other engine room components.
Combustion air describes the air that the engine requires to burn fuel.

** delta T = Permissible temperature rise in engine room

See Cat’s excellent guide ➥ http://www.blanchardmachinery.com/pu...entilation.pdf
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is online now   Reply With Quote
Old 18-04-2012, 10:50   #7
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 5,787
Re: Perkins diesel air intake volume

On that note Gord.......Delta T......I have been in on and around several hundred commercial engine installations. While the intended act is to keep engine room temp no more than 30 degrees above ambient this exercise is all but futile in all but the largest and most complex of installations. It is, nonetheless a good target.
__________________
Sailmonkey is online now   Reply With Quote
Old 18-04-2012, 11:35   #8
Registered User

Join Date: Nov 2011
Location: Montegut LA.
Boat: Now we need to get her to Louisiana !! she's ours
Posts: 3,421
Re: Perkins diesel air intake volume

Any piston engine is really nothing but a compressor, and air is what it compresses!along with the fuel. So large amounts of Air are needed for proper combustion, and cooling. So therefor a proper air induction needs to be added, and also a proper outlet for the heated air in the compartment. now the only problem is doing it !LOL you already know ya got a problem now ya just need to find the easyest and most ship shape way to do this job with the amount of money you have to spend !I always like a natrual style inlet to the engine space, and a powerd outlet from the room. But thats me ! I like simple !! so really a large Dorade inlet and a drum style fan and pipeing to the outside where it will fit ! just my 2 cents
__________________
Bob and Connie
bobconnie is offline   Reply With Quote
Old 19-04-2012, 10:09   #9
Registered User

Join Date: Dec 2007
Location: Echo Bay, Ontario
Boat: 40' steel Trawler
Posts: 31
Re: Perkins diesel air intake volume

Hi Gord,
Thankyou for responding to my question about engine air intake.
The info from Cat is most informative reading. It's hard to imagine
a boat being built without engine room ventilation, but they did it.
What is harder to imagine is the fact that previous owners of this
boat have not thought about Air-Supply for engines and the engine room.
But anyway, thanks again for your help, And Thanks to everyone else for
their help as well.
__________________

__________________
Capt Nemo is offline   Reply With Quote
Reply

Tags
diesel, perkins

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 04:03.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.