fuel consumption VS speed change

Going through the licensing process ? Have queries, comments, or do you need an answer to that obscure exam question ? This is the place to post.
QAMER
Bilge Dweller
Posts: 9
Joined: Sun Oct 12, 2008 6:58 pm

fuel consumption VS speed change

Postby QAMER » Tue Mar 01, 2011 8:24 pm

Hi anyone know how to solve this type of question formula/calculation . THANKS



question: If your ship burns 8 tons of fuel per hour at 15 knots, how many tons per hour will it burn at 21 knots?
11.2 tons
22.0 tons
15.7 tons
12.9 tons
Answer Was: B
Your Answer A
Wrong

User avatar
The Dieselduck
Administrator
Posts: 2749
Joined: Sun Jul 22, 2007 1:41 pm
Currently located: Nanaimo, British Columbia, Canada (West Coast of Canada)

Re: fuel consumption VS speed change

Postby The Dieselduck » Thu Mar 03, 2011 7:03 pm

My head is not much into this kind of puzzle these days, but it seems to me the question is missing some information to be able to answer correctly. You would have to know more info to calculate, like coefficent of hull friction and such... I know, from experience that fuel consumption goes up dramatically but the exact formula I forget right this minute.
Martin Leduc
Certified Marine Engineer and Webmaster
Martin's Marine Engineering Page
http://www.dieselduck.net

User avatar
JK
Enduring Contributor
Posts: 2697
Joined: Tue Sep 04, 2007 2:29 am
Currently located: East Coast, Canada

Re: fuel consumption VS speed change

Postby JK » Sat Mar 05, 2011 7:41 am

I played around with it while I was suppose to be working on something else and like Martin says, there must be something missing. Then again, in my job we don't buy the fuel so I don't worry too much about it.

User avatar
Sébastien
Engineering Mentor
Posts: 97
Joined: Mon Oct 01, 2007 5:06 am
Currently located: Québec

Re: fuel consumption VS speed change

Postby Sébastien » Mon Mar 07, 2011 1:10 pm

Reed's volume 4 chapter 7
It can be assumed that a major portion of the designed operational speed range is proportional, and that for any two points within this range the specific fuel consumption is constant. On the same trip, it can be assumed that the ships' displacement is also constant. You are left with cons1/cons2=(v1/v2)3. In your example cons2= 8* (21/15)3 = 8*2.744 = 21.95 tons

QAMER
Bilge Dweller
Posts: 9
Joined: Sun Oct 12, 2008 6:58 pm

fuel consumption VS speed change

Postby QAMER » Tue Mar 08, 2011 6:13 am

Thanks to all of you specially SEBASTIEN.

User avatar
The Dieselduck
Administrator
Posts: 2749
Joined: Sun Jul 22, 2007 1:41 pm
Currently located: Nanaimo, British Columbia, Canada (West Coast of Canada)

Re: fuel consumption VS speed change

Postby The Dieselduck » Tue Mar 08, 2011 10:02 am

very sharp indeed sebastien, thank you. Its so simple I feel stupid.. ehehehe
Martin Leduc
Certified Marine Engineer and Webmaster
Martin's Marine Engineering Page
http://www.dieselduck.net

KWOBGUS
First Time Poster
Posts: 1
Joined: Sat Sep 01, 2012 10:28 am

Re: fuel consumption VS speed change

Postby KWOBGUS » Sat Sep 01, 2012 10:41 am

Hey I was just curious where you got 3 as a multiplication factor. Thanks!

User avatar
JollyJack
Fleet Engineer
Posts: 1130
Joined: Wed Mar 24, 2010 3:57 am
Currently located: Eastern Canada

Re: fuel consumption VS speed change

Postby JollyJack » Sat Sep 01, 2012 6:34 pm

3 is not a multiplication factor, it's cons1/cons2=(v1/v2) cubed
Discourage incest, ban country "music".


Return to “Training Room”

Who is online

Users browsing this forum: No registered users and 1 guest