Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 6th January 2015, 09:44   #121
BHPian
 
Join Date: Nov 2014
Location: New Delhi
Posts: 57
Thanked: 47 Times
Exclamation Re: Engine size inversely proportional to Fuel efficiency?

Quote:
Originally Posted by Aromal View Post
In that case How does Jet engine start? At least from what I know, there are no electric motors like cars in aeroplanes
How does the engine get initial air for starting? How is the fuel delivery timed? What about the working cycle & different stages of combustion?

Sorry for too many questions & I'm asking this to you since, I find you very comfortable to answer to queries of novice like me.
In jet engines first an electric motor starts rotating the main turbine shaft, hence the fan. Once sufficient compressed air flow is generated, igniter generates sparks and then fuel is introduced into the chamber, after that air thrust from exhaust of combustion takes over the function of rotating the turbine, and electric motor is shut off. Now fuel flow is increased slowly to achieve operating speed.
There are no pistons and valves like that of a normal car engine so it has different working cycle. In jet engines fuel combustion is almost continuous as compared to car engines where fuel is ignited at intervals.
Experts kindly correct me if I'm wrong!

Last edited by rev_rohit : 6th January 2015 at 09:49.
rev_rohit is offline   Reply With Quote
Old 6th January 2015, 15:23   #122
Senior - BHPian
 
mallumowgli's Avatar
 
Join Date: Apr 2010
Location: Palakkad/Coimbatore
Posts: 1,101
Thanked: 704 Times
Default Re: Engine size inversely proportional to Fuel efficiency?

Quote:
Originally Posted by DerAlte View Post
In a jet engine, the gases exiting the jet exhaust apply a force to the whole assembly which moves the aircraft forward. In a Turbo-Prop engine, the GT (it is not a jet engine) rotates the propeller.
Oh my! I went off on a tangent didn't I? You were talking about Jet engine and I was going blah blah on Gas turbines. I don't know from where this GT got embedded into my head. Right now let me look for a hole to bury myself. Apologies!
mallumowgli is offline   Reply With Quote
Old 6th January 2015, 16:57   #123
Distinguished - BHPian
 
Join Date: Oct 2012
Location: Delhi
Posts: 3,067
Thanked: 6,234 Times
Default

Quote:
Originally Posted by rev_rohit View Post
In jet engines first an electric motor starts rotating the main turbine shaft, hence the fan. Once sufficient compressed air flow is generated, igniter generates sparks and then fuel is introduced into the chamber, after that air thrust from exhaust of combustion takes over the function of rotating the turbine, and electric motor is shut off. Now fuel flow is increased slowly to achieve operating speed.
There are no pistons and valves like that of a normal car engine so it has different working cycle. In jet engines fuel combustion is almost continuous as compared to car engines where fuel is ignited at intervals.
Experts kindly correct me if I'm wrong!

Just back from a very successful fishing trip.10 Barracuda's and a King Fish, so dinner will be fish tonight!

Correct, in addition to electrical starters many jet engines on commercial jets can be started by means of air, supplied externally or via the onboard systems. in the latter the plane's APU will provide electrical and pneumatic power. There is also often the possibility to cross bleed start them. So if one engine is running it provides enough air to start the other engines.



Here is an interesting link to various starting options for various engine types: http://en.m.wikipedia.org/wiki/Aircraft_engine_starting

And an interesting Video talking about various (bleed air) system on a jet engine



Enjoy, Jeroen
Jeroen is offline   (1) Thanks Reply With Quote
Old 7th January 2015, 17:10   #124
Senior - BHPian
 
mallumowgli's Avatar
 
Join Date: Apr 2010
Location: Palakkad/Coimbatore
Posts: 1,101
Thanked: 704 Times
Default Re: Engine size inversely proportional to Fuel efficiency?

Quote:
Originally Posted by Jeroen View Post
Correct, in addition to electrical starters many jet engines on commercial jets can be started by means of air, supplied externally
We had a fellow member kkr2k2, who used to work for such a company (mfr of Jet engine start up units) - but he doesn't seem to be active of late
mallumowgli is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
What is your Actual Fuel Efficiency? normally_crazy The Indian Car Scene 5058 4th December 2017 12:40
Why the heck do we care ONLY about Fuel Efficiency GTO The Indian Car Scene 118 4th July 2012 15:00
Fuel efficiency of Chevy Aveo 1.4 narasimhan Technical Stuff 1 2nd May 2006 00:51
Swift ZXi Climate control_improve fuel efficiency pranil Technical Stuff 21 13th March 2006 18:16
honda city (new) (old) and mitsubishi lancer fuel efficiency devarshi84 The Indian Car Scene 3 19th July 2005 12:39


All times are GMT +5.5. The time now is 07:07.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks