Exhaust
02-25-2005, 11:27 AM
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Exhaust
Folks, fellow turbine enthusiasts,
In the interest of saving myself some money I really didn't have, I made a spot welder and taught myself a significant amount about building a bifurcated exhaust system for a helicopter. I would be interested in knowing any special needs of the aircraft aspect of this as I am considering making exhausts for not only helicopters, but for airplanes as well for financial gain.
This link has some pictures of my earliest attempts, tho not as successful as what I don't have any pictures of:
http://www.scalerchelis.com/gallery/album46
At this time I feel that helicopters are more difficult as most turbine mechanics require a double change in redirection (at a minimum) of the exhaust gasses and thrust is not desired in these, contrary to aircraft. Tolerances for multiple wall exhaust systems within a closed fuselage are not that significant if the exhaust system is properly designed.
I would appreciate education in the airplane field and the needs of aircraft running turbines. Obviously, you folks use the thrust whereas the helicopters diffuse it and redirect it as much as possible.
Do you decrease the diameter of the internal exhaust tube to increase the thrust? Does this cause heat issues?
Do you use single, double, or triple wall?
What kind of clearance tolerances are necessary in aircraft?
Is this an item you feel could be built and fit without having the fuselage and turbine present? (virtually impossible in many helicopters)
Are you looking for another source for exhaust systems, in other words is there a market for a second fabricator?
Thanks for the time
Jack
In the interest of saving myself some money I really didn't have, I made a spot welder and taught myself a significant amount about building a bifurcated exhaust system for a helicopter. I would be interested in knowing any special needs of the aircraft aspect of this as I am considering making exhausts for not only helicopters, but for airplanes as well for financial gain.
This link has some pictures of my earliest attempts, tho not as successful as what I don't have any pictures of:
http://www.scalerchelis.com/gallery/album46
At this time I feel that helicopters are more difficult as most turbine mechanics require a double change in redirection (at a minimum) of the exhaust gasses and thrust is not desired in these, contrary to aircraft. Tolerances for multiple wall exhaust systems within a closed fuselage are not that significant if the exhaust system is properly designed.
I would appreciate education in the airplane field and the needs of aircraft running turbines. Obviously, you folks use the thrust whereas the helicopters diffuse it and redirect it as much as possible.
Do you decrease the diameter of the internal exhaust tube to increase the thrust? Does this cause heat issues?
Do you use single, double, or triple wall?
What kind of clearance tolerances are necessary in aircraft?
Is this an item you feel could be built and fit without having the fuselage and turbine present? (virtually impossible in many helicopters)
Are you looking for another source for exhaust systems, in other words is there a market for a second fabricator?
Thanks for the time
Jack
02-25-2005, 12:33 PM
#2
My Feedback: (24)
RE: Exhaust
Hi Helijack,
If you want to exploit this area of the market - there is actualy a void. Currently Wren is ("are" in the British vernacular) the only company to make "thrust augmenter" tubes instead of the traditional tapered units. I remeber seing the technical write-up on this in an open-forum newsletter of the Gas Turbine Builder's Association. Remarkable simple formula for building these animals if I remember right. There's no patent that I know of- as that was the idea for pubishing the design publicly I beleive. There's no thrust augmenter type set up for bifurcated pipes, which could theoretically compensate for the losses due to the bifurcation, if even possible. There also isn't too much available for thrust augmenter tubes for larger turbines - actually none I know of. Another advantage of augmented tubes (again if I rember right) is that you taper out for a distance, then the cross section is constant, allowing you to cut the tube down to size. Kind of nice for single pipe installations - you just size it for the turbine and cut down for the airframe.
All the current mass-production technology pipes I know of are dual wall. Can't answer about clearances as that would be real dependant on the airframe venting capability in each instance.
I say - go for it -the market always needs competition. It only makes us stronger. Good luck!
If you want to exploit this area of the market - there is actualy a void. Currently Wren is ("are" in the British vernacular) the only company to make "thrust augmenter" tubes instead of the traditional tapered units. I remeber seing the technical write-up on this in an open-forum newsletter of the Gas Turbine Builder's Association. Remarkable simple formula for building these animals if I remember right. There's no patent that I know of- as that was the idea for pubishing the design publicly I beleive. There's no thrust augmenter type set up for bifurcated pipes, which could theoretically compensate for the losses due to the bifurcation, if even possible. There also isn't too much available for thrust augmenter tubes for larger turbines - actually none I know of. Another advantage of augmented tubes (again if I rember right) is that you taper out for a distance, then the cross section is constant, allowing you to cut the tube down to size. Kind of nice for single pipe installations - you just size it for the turbine and cut down for the airframe.
All the current mass-production technology pipes I know of are dual wall. Can't answer about clearances as that would be real dependant on the airframe venting capability in each instance.
I say - go for it -the market always needs competition. It only makes us stronger. Good luck!
02-25-2005, 12:57 PM
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RE: Exhaust
Interesting Chuck. In researching your term 'augmentor' I discovered that is what I call an accumulator secondary to my A&P buddy. I see wren sometimes uses titanium, which is not necessary at all. Stainless is more than adequate for these applications, just as the real thing is. Anyway, the augmentor/accumulator does significantly decrease the EGT, especially in my application on the helicopters.
So, lets add a new question or two.
If you were looking for someone to build you an exhaust, how would you go about locating them? Website? Word of mouth? Advertisement on a forum?
Jack
So, lets add a new question or two.
If you were looking for someone to build you an exhaust, how would you go about locating them? Website? Word of mouth? Advertisement on a forum?
Jack
02-27-2005, 04:08 PM
#10
My Feedback: (24)
RE: Exhaust
Found the original write up:
To give credit where it's due - John Wright and Mike Murphy (MW/Wren fame) are the ones who came up with this and published in the January 2003, GTBA Newsletter.
If you want the article you could get it directly from the GTBA. Good stuff and is certainly an area where we need to improve.
To give credit where it's due - John Wright and Mike Murphy (MW/Wren fame) are the ones who came up with this and published in the January 2003, GTBA Newsletter.
If you want the article you could get it directly from the GTBA. Good stuff and is certainly an area where we need to improve.
02-28-2005, 02:56 PM
#12
My Feedback: (24)
RE: Exhaust
The GTBA is run out of England, but there's an American segment of it. They are located at:
http://www.gtba.co.uk/
You'll have to join, but the cost is like nothing - $20-30??? You gat just a whole ton of information from it - enough to write a serious book on the subject.
You might even just be able to buy the newsletter.
Good luck
http://www.gtba.co.uk/
You'll have to join, but the cost is like nothing - $20-30??? You gat just a whole ton of information from it - enough to write a serious book on the subject.
You might even just be able to buy the newsletter.
Good luck
