Prettiest FWE (?) - the 'Lady Anne Boleyn'

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milisavljevic
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re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by milisavljevic » Fri Sep 01, 2006 2:24 pm

Mike Everman wrote: I like the new intake transition location.
Larry Cottrill wrote:
Only if someone will build it will we know for sure. But if I'm just wrong, how could my original design have run so well? And I think this layout is FAR closer to proper tuning!
Hello Larry --

Wow! Go away for a couple of days and look what happens! I want to run this new layout through the model;
however, someone else is ahead of you in the queue. I hope to be able to model the revised layout Saturday.

I know you have your reasons for moving the intake transition forward, but this would seem to reduce thrust.
If I come up with anything different, I will mark up your drawing, and post it to this thread for comparison. You
are welcome to take whatever dimensions I provide and then test how well they survive the 'UFlow challenge'.

Best regards,
M.
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Re: re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by Graham C. Williams » Fri Sep 01, 2006 3:22 pm

Eric wrote:Werent Grahams 07 fwe's linear types?

Eric
Like M. I've been away for a few days and found these developments. In answer to your question, yes our Type07 was a linear motor produced as a study piece looking at velocity and massflow ideas.

Dear Larry.
I think that the induction pipe can go towards 29 - 30mm dia. with some profit.

Dear M.
Many thanks for the enlightening discourse; I think I better understand the Chinese motor for it. I have not forgotten the reply I owe you. The subject of unpacking and subsequent repacking was giving me some hardship. Your ideas are interesting.

Regards
Graham.

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Re: re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by larry cottrill » Fri Sep 01, 2006 5:06 pm

Graham C. Williams wrote:Dear Larry.
I think that the induction pipe can go towards 29 - 30mm dia. with some profit.
Thanks. Increases massflows considerably, though some velocity gets traded off for it, of course. I have to shorten the pipe a bit to maintain the end corrections, then pull it considerably farther out to get the velocity node back to the front plane (i.e. the intake would shift rearward on the folded engine). Seems fine once I'm done manipulating, though - it still runs out really well, and the pressure wave viewed over several cycles at the front plane is still practically a sine curve. I'm guessing it weakens maybe 2 to 3 percent per cycle.

These are the best-looking UFLOW runs I've ever seen. Of course, because of M's goading, I know more now (or think I do) than ever before. I even developed a little UFLOW model of the intake viewed as an open pipe in isolation, which I can tweak until its natural frequency is what I think is right to sync it up. This is very useful to get a "first cut" of the pipe to set up in the unfolded model (being careful to get the temps the same).

James' pics have been very useful, too. I've attempted to adjust the interior temps of the middle cone and choke to more realistically reflect what seems to be happening there. If you like, I could work up a little sketch of what I use for temps in the model, so you could judge how much of it is wishful thinking, or even pure hogwash. For temps, I really have nothing to go on except "TLAR" and what I've used in previous examples. Errors in judgment are thus perpetuated ad infinitum.

But, I get running engines. They just always seem to cycle a lot faster when built and tested than predicted by my crude modelling.

L Cottrill

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Re: re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by larry cottrill » Fri Sep 01, 2006 5:30 pm

milisavljevic wrote:Wow! Go away for a couple of days and look what happens! I want to run this new layout through the model;
however, someone else is ahead of you in the queue. I hope to be able to model the revised layout Saturday.
I can hardly wait!
I know you have your reasons for moving the intake transition forward, but this would seem to reduce thrust.
Would I gain an understanding of this by going back to the graph Mike published early on? (You know, the harmonics and how they sum together) - Or, does it need to be looked at differently? The location I landed on is entirely based on how far forward (leftward on Graham's sketches earlier) I have to pull the intake in the unfolded model to get the velocity node back to the front plane of the chamber cone where I want it. What happens when I achieve that is I get a velocity at that plane that is virtually dead flat over several cycles, while the pressure curve at that point is 'smooth as a gravy sandwich' and runs out amazingly well through the first few cycles. Once the UFLOW 'data point' for the intake end is then adjusted to coincide with the new location, the speed and flow curves look really good, too (though not as smooth, of course).

The foregoing can be considered a basic synopsis in how I work up the 'unfolded' model. It looks just like Graham's sketches early in this thread, except I orient it the other way round (to make manipulating the intake dimensions and location easier in UFLOW). Naturally, you are most welcome to criticize this method to any degree you would like. (Others may chime in, too, of course, as they feel led.)
If I come up with anything different, I will mark up your drawing, and post it to this thread for comparison. You
are welcome to take whatever dimensions I provide and then test how well they survive the 'UFlow challenge'.
I wait with bated breath (not "baited" breath, as I am no fisherman).

L Cottrill

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re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by Al Belli » Fri Sep 01, 2006 8:04 pm

Hi Larry,

Don't You ever eat sardines; and get " baited " breath. :)

"Bated breath" has been around a long time. Here's the first cite in the Oxford English Dictionary: "1596 Shakespeare, Merchant of Venice i. iii. 125 'With bated breath, and whispring humblenesse.'"



Al Belli

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Re: re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by Dave_G » Fri Sep 01, 2006 10:43 pm

Larry Cottrill wrote:

If you like, I could work up a little sketch of what I use for temps in the model, so you could judge how much of it is wishful thinking, or even pure hogwash. For temps, I really have nothing to go on except "TLAR" and what I've used in previous examples.

But, I get running engines. They just always seem to cycle a lot faster when built and tested than predicted by my crude modelling.

L Cottrill
Larry, I'm not sure if this was an offer to one person or the forum-at-large, but as someone who is just gettiing started with Uflow I'd love to see your sketch of what you use for temperatures in the model. Any sample Uflow files you'd care to post would be much appreciated also. If this was not your intent; If I've mis-read your statement above, no problem.

Dave

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re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by milisavljevic » Sat Sep 02, 2006 12:54 am

Graham C. Williams wrote: Dear M.
Many thanks for the enlightening discourse; I think I better understand the Chinese motor for it.
The subject of unpacking and subsequent repacking was giving me some hardship. Your ideas are interesting.
Hello Graham -- You are very welcome.

There was an episode of Dr. Who featuring two characters named "Enlightenment" and "Persuasion";
it would be sweet if my posts proved to be both enlightening and persuasive. Only time will tell! ;-)

I am uncomfortable wrt. the business of folding and unfolding motors that are intended to built in the
now-classic "FWE style". Depending upon their relative dimensions (not those found in the TARDIS),
many such ducts will behave as closed-pipe resonators; however, unfolding them results in what will
typically behave as an open-pipe. The unfolding also creates other problems. It is an interesting idea.

Best regards,
M.
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ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

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re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by milisavljevic » Sat Sep 02, 2006 1:19 am

Larry Cottrill wrote: Of course, because of M's goading...
Hello Larry -- "It is better to serve as a goad than a gadfly." Come to think of it, maybe not! =)
James' pics have been very useful, too. I've attempted to adjust the interior temps of the middle cone and choke
to more realistically reflect what seems to be happening there. If you like, I could work up a little sketch of what
I use for temps in the model, so you could judge how much of it is wishful thinking, or even pure hogwash.
Please post the temperature profile that you are using for the "Lady Anne". After I model the new duct layout,
I will post the profile with recommended temperatures (this should bring you closer to real-world frequencies).

Best regards,
M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
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re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by Eric » Sat Sep 02, 2006 1:53 am

The notsowonderful thing about U flow is that sometimes if you put the temperatures as they should be, it crashes, often consistently. I dont know I just never had any luck with uflow and stability.

Maybe it doesnt like my 64 bit archetecture, though I never had any luck with intel space heaters, i mean pentiums.
Image

Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

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Re: re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by larry cottrill » Sun Sep 03, 2006 9:23 pm

milisavljevic wrote:Hello Larry -- "It is better to serve as a goad than a gadfly." Come to think of it, maybe not! =)
Both are fine in my book - they are things that can suddenly get tired or lazy beasts moving - or, effect a sudden change in direction ;-)

Your friends are not always the people who immediately make you happy.

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Re: re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by larry cottrill » Sun Sep 03, 2006 9:31 pm

Dave_G wrote:Larry, I'm not sure if this was an offer to one person or the forum-at-large, but as someone who is just gettiing started with Uflow I'd love to see your sketch of what you use for temperatures in the model. Any sample Uflow files you'd care to post would be much appreciated also. If this was not your intent; If I've mis-read your statement above, no problem.
I am now at the age where I am so used to looking stupid that I just accept it as an integral part of being here. I will be glad to post the layout of temps for all to see. However, it will take a little time because I think it will be most clearly done as a sketch showing the actual UFLOW layout I use. That will be more useful to the critical eye of my "research staff" than a table of numbers, anyway. I can probably have it posted in a couple of days.

L Cottrill

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Re: re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by larry cottrill » Sun Sep 03, 2006 9:45 pm

milisavljevic wrote:I am uncomfortable wrt. the business of folding and unfolding motors that are intended to built in the
now-classic "FWE style". Depending upon their relative dimensions (not those found in the TARDIS),
many such ducts will behave as closed-pipe resonators; however, unfolding them results in what will
typically behave as an open-pipe. The unfolding also creates other problems. It is an interesting idea.
Though this was in response to Graham, I'd like to comment on it, since I generally follow his lead on "how to do it" with UFLOW1D.

My own feeling is that it is impossible to "unfold" or "unpack" classic FWE type engines (or Chinese, or Thermojet, or concentric engines, or ...) in a way that makes a linear model that is truly equivalent. A linear engine (I mean a real one, like Graham and Nick's Type 07) is literally describable in one-dimensional terms (except for very minor effects at exit flares, which can be ignored for basic analysis), but any engine that excites the intake by reflecting wave energy back through the chamber (or any other part) is inherently multi-dimensional. You can figure out how to model them as APPROXIMATELY acoustically equivalent or APPROXIMATELY flow equivalent, but not both at the same time.

I don't believe the UFLOW1D model of a "folded" engine is EVER realistic; I only hold that it is still useful for design, if its inherent limitations (which are many and varied) are kept in mind. In general, the most important consideration is to get the resonances "locked in", and UFLOW1D will help you do that, at least approximately. There is probably no modelling technique that will achieve a perfect simulation, unless all the temperatures in the actual running engine could be measured to high accuracy (and if you could do that, why would you need to model it? ;-).

L Cottrill

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re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by milisavljevic » Mon Sep 04, 2006 12:05 am

Larry Cottrill wrote:Your friends are not always the people who immediately make you happy.
Have you been talking to (my freshly skewered friend) Mike Everman? :ducks:

Evil M.
Last edited by milisavljevic on Mon Sep 04, 2006 12:06 am, edited 1 time in total.
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an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

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Re: re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by Graham C. Williams » Mon Sep 04, 2006 12:05 am

Larry Cottrill wrote: My own feeling is that it is impossible to "unfold" or "unpack" classic FWE type engines (or Chinese, or Thermojet, or concentric engines, or ...) in a way that makes a linear model that is truly equivalent. A linear engine (I mean a real one, like Graham and Nick's Type 07) is literally describable in one-dimensional terms (except for very minor effects at exit flares, which can be ignored for basic analysis), but any engine that excites the intake by reflecting wave energy back through the chamber (or any other part) is inherently multi-dimensional. You can figure out how to model them as APPROXIMATELY acoustically equivalent or APPROXIMATELY flow equivalent, but not both at the same time.

I don't believe the UFLOW1D model of a "folded" engine is EVER realistic; I only hold that it is still useful for design, if its inherent limitations (which are many and varied) are kept in mind. In general, the most important consideration is to get the resonances "locked in", and UFLOW1D will help you do that, at least approximately. L Cottrill
Dear Larry.
I hold you in the highest regard, your imagination and industry. Though I do not hold all the answers by any means I'm happy to help you as some small recompense for that you gave me in my early days with these motors.
I've been playing with some changes to this basic design, the most radical of which would please Mike (and possibly M. and Bill) greatly and I'll post all of them in the coming week. I cannot get way for two or three facts: the first you have stated above, the second is that increasing the induction dia. tends to equalise the induction and exhaust thrust contributions (so that as a linear motor thrust tends towards zero) but as a bent motor total thrust increases. My Thrust calculations do not yet take into account the location of the bend in the motor, here I’m looking at a motor that is bent near its front but the calculations always assume a bend in the middle. This problem is becoming a priority that I must work on as soon as time allows because I just cannot say what the internal momentum contribution (or correction if you like) will be in this example. The third, rebound pressure. As this builds or as changes in the design increase this value the massflow zero crossing point (the velocity zero crossing) moves about a lot and can move outside the CC - this is not good in the early stages of pressure build as combustion moves away from the optimum location for wave reinforcement etc. All the type 07 motors seem to display an inverse relationship between induction dia. and length O.A. Eric’s suggestion of putting an advanced tail on the end may be a very good idea when coupled with a large induction diameter. The last observation of interest is that this little pipe can stand relatively long induction pipes 16.25% and beyond. Even with a 30mm induction dia and a 16.25% long induction pipe this motor still displays +ve breathing characteristics (the best I've seen is probably the k-pt_07x motor and some of Bills) but yet again the Massflow zero point tends to wander a long way.

Regards
Graham.

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re: Prettiest FWE (?) - the 'Lady Anne Boleyn'

Post by milisavljevic » Mon Sep 04, 2006 12:15 am

Graham C. Williams wrote: I've been playing with some changes to this basic design, the most radical of which would please Mike
(and possibly M. and Bill) greatly and I'll post all of them in the coming week.
Hello Graham -- I am looking forward to seeing your changes. Your posts are always interesting...and food for thought.

Btw., do you have a word or phrase that you use to describe the modified section(s) (of the tailpipes) in these motors?

Best regards,
M.
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for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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