FWE From Outer Space - Revised Lady Guinevere

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larry cottrill
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FWE From Outer Space - Revised Lady Guinevere

Post by larry cottrill » Thu Sep 14, 2006 2:14 pm

This has not been the Year Of Valveless Pulsejets at our house; it has been the Year Of Animal Husbandry. However, a few days ago I was able to pick up for a little while where I left off back in February with the Lady Guinevere. I had marked up the sheet steel for the cones and the oddball intake back then, and the sheets had been lying around in the basement gathering a thin film of rust ever since. But, Saturday morning I grabbed the sheets, hauled them out to the garage along with my air shear, and in about half an hour had the cut pieces ready to form. A later trip out to my cone-forming tool in the horse barn (i.e. freezeless water hydrant) got the cones basically in shape ready to weld. Astoundingly, less than a half hour's work with the bench vise and a large (3/8-inch) twist drill got the intake shell formed (except for flaring) in good shape; I couldn't believe how well that went, considering I had never shaped anything like it before. It took longer to carefully hammer the inlet flare than it did to basically form the piece.

Unfortunately, after forming the cones, I naturally decided to change the design to bring this pipe more in line with the apparent success of the much smaller Lady Anne Boleyn engine (recently built and run by James D of the UK). I say 'unfortunately' because I don't want to re-design any of the cones I made, and I naturally want to keep the 32-inch overall length so as to still have a contender for the proposed "32 inch Chinese" engine cookoff. Graham and M at least will recognize that this imposes a set of constraints that aren't necessarily conducive to creative design: an engine whose front and rear sections are already "cut in stone", with only the middle piece to play with. In the case of this particular engine, the middle section is particularly short, as well. But, I decided to blunder on ahead, anyway.

What I came up with is shown in approximately scale form in the drawing, below. The dome, chamber cone and the two rear cones are the same as on the original drawing. However, all cylindrical parts are eliminated. The very short cylindrical section in the 'dilutor/augmentor' tail section was dropped (even though clearly shown in the famous SNECMA drawing) in order to allow lengthening the center section of the engine as much as possible. The center cylinder is replaced with an enlarged mockup of the Anne Boleyn 'mid-cone / choke cone' combination (which again is based on Graham's Type 07 tailpipe mid-section). The tail end of the choke cone extends slightly (5mm) past the front end of the 'dilutor/augmentor' intake cone, as in the SNECMA drawing. This engine reminds me of some kind of shoulder weapon from the 1930s Buck Rogers books.

It is impossible for UFLOW1D to correctly model the 'gap' in the middle of the pipe (by this I mean the extra intake at the 2/3 point), and also impossible to model the 5mm 'overlap' in the two sections at this location. Of course, I'm not about to let mere details like this stop me: In the model, I shoved the intake rearward a few mm (shortening the tail cone by the same small amount) so that the mid-cone and choke would be unaltered. (The choke and intake are designed so that they are "parallel" segments of identical cones, giving a constant 12 or 13 mm "width" to the intake gap all around.) Then, the opening is simply replaced with a very flat conical wall. This unsavoury detail is admittedly a totally artificial device, and will not be elaborated upon further; it is not good, but is the best I could do under the circumstances. The idea is to make the basic acoustics right (at least approximately); the flows will just have to take care of themselves. The extremely low temperatures in the tail cone are wild guesses, based on the supposition that in real life, the augmentor section will suck in vast quantities of outdoor air.

It is also impossible for UFLOW1D to tell us what the effect will be of the emerging pressure waves from the front intake and dilutor/augmentor intake making their (relatively slow) cool air traverse between the two locations. (Working out this detail will be left as an exercise for the reader ;-)

Anyway, here it is. All I need now is another little sheet of steel to make the extra cones from (I'd have needed it for cylinders, anyway). Time is still hard to come by, so I have no idea how soon this will get finished up and test run. I may publish a few construction photos later. How the model runs is basically shown in the graphs below, which can be compared to the ones I published for the Lady Anne; keep in mind, however, that there is a big size difference in the two engines.

All comments welcome here.

L Cottrill
Attachments
UFLOW1D_Guinevere_running_out_01.jpg
UFLOW graph showing how the revised Lady Guinevere 'runs out' over time (from the starting condition shown above) - dark blue = exhaust plane; light blue = inlet plane; yellow = rear of chamber dome. Graphic Copyright 2006 Larry Cottrill
UFLOW1D_Guinevere_running_out_01.jpg (83.01 KiB) Viewed 5463 times
UFLOW1D_Guinevere_best_press_01.jpg
UFLOW1D depiction of moment of best pressurization following the starting condition shown. This is basically a picture of Kadenacy action performance. Note the low velocities throughout! Graphic Copyright 2006 Larry Cottrill
UFLOW1D_Guinevere_best_press_01.jpg (66.21 KiB) Viewed 5465 times
UFLOW1D_Guinevere_starting_cond_01.jpg
Starting condition for the UFLOW1D run. The density curve is almost entirely a reflection of the assumed gas temperatures in the model. Graphic Copyright 2006 Larry Cottrill
UFLOW1D_Guinevere_starting_cond_01.jpg (64.04 KiB) Viewed 5465 times
UFLOW1D_Guinevere_temps_01.jpg
Revised Lady Guinevere UFLOW1D model layout and assumed temperatures. The temps throughout the tail cone 'dilutor/augmentor' are wild guesses, based on the assumption that it will take in air very freely. Graphic Copyright 2006 Larry Cottrill
UFLOW1D_Guinevere_temps_01.jpg (267.4 KiB) Viewed 5465 times
Lady_Guinevere_Rev_01.gif
Approximate scale drawing of the newly revised Lady Guinevere FWE valveless pulsejet. No cylinders left - just cones and the weirdly shaped intake shell. Drawing Copyright 2006 Larry Cottrill
Lady_Guinevere_Rev_01.gif (12.63 KiB) Viewed 5465 times

Eric
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re: FWE From Outer Space - Revised Lady Guinevere

Post by Eric » Thu Sep 14, 2006 2:58 pm

Glad to see someone else is actually trying this type of motor. How much thrust do you expect from it?

Eric
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Re: re: FWE From Outer Space - Revised Lady Guinevere

Post by larry cottrill » Thu Sep 14, 2006 3:14 pm

Eric wrote:Glad to see someone else is actually trying this type of motor. How much thrust do you expect from it?
Why, at least 20 lb, of course ;-)

More seriously, thrust is something I've never understood how to estimate properly. In this case, the built-in 'feedback loop' between the two intakes makes performance practically unknowable, it seems to me. Actually, this is probably a pretty hard geometry to get exactly right - especially when you have to apply so many "simplifying assumptions" just to get it into a form that can be modeled one-dimensionally.

I figure I will be very lucky just to get this one to start and run.

L Cottrill

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re: FWE From Outer Space - Revised Lady Guinevere

Post by Eric » Thu Sep 14, 2006 4:28 pm

Well you could use the other 2.5 lb thrust engine thats similar as a base line, except for the tail augmenter is a variable, and estimate thrust based on the scale up.

The air in the augmenter section is going to be very cool durring part of the cycle, especially if there is any forward motion, but hot durring part of the cycle, so you have to adjust things acordingly. Basically the timing is going to be different for each part of the cycle.

I would really suggest at least looking into the chinese style tailpipe layouts for a future competition chinese contest FWE. With the normal FWE sized combustor you should be able to get 4 lbs easy.


Eric
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re: FWE From Outer Space - Revised Lady Guinevere

Post by milisavljevic » Fri Sep 15, 2006 6:28 am

Larry Cottrill wrote: I figure I will be very lucky just to get this one to start and run.
Hello Larry -- I wish you lots of luck* with this one!

With respect to UFlow temperature profiles, please consider raising the maximum gas temperature to 2000 K.
I should also point out the wall temperatures do not necessarily mirror internal (gas) temperature trends. ;-)

Best regards,
M.

*Given your recent choices in pulsejet names, you may be needing "lady luck"! =)
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re: FWE From Outer Space - Revised Lady Guinevere

Post by larry cottrill » Fri Sep 15, 2006 7:21 pm

Here are cone sheet patterns for the middle cone and choke cone which I added in this revision. This should print full size on a single 8.5x11 inch sheet, using a 96DPI printer. The cone sheet dimensions are:

Middle Cone:
R1 = 543mm / R2 = 368mm / Angle = 20.5 degrees

Choke cone:
R1 = 152mm / R2 = 103mm / Angle = 73.4 degrees

L Cottrill
Attachments
Lady_Guinevere_Rev01_cone_sheet_3.jpg
Lady Guinevere Rev 01 Cone Sheet Pattern 3 - the new cones added in the middle. Prints full size at 96 DPI. Drawing Copyright 2006 Larry Cottrill
(165.52 KiB) Downloaded 442 times

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re: FWE From Outer Space - Revised Lady Guinevere

Post by larry cottrill » Wed Sep 20, 2006 3:50 pm

For the few die-hards that have hung with me thus far:

Here are full size versions of the cone sheets given in the original Guinevere thread. The dimensions have not changed (except that the intake port was widened slightly), but IF you have a 96 DPI printer to print these, they should be MUCH more accurate to cut from than an enlargement from a tiny scale drawing. I have also included the full size intake plan (which includes the sheet pattern) from the original Lady Guinevere thread, so that the complete set of patterns can be found here.

If the largest you can print is an 8.5x11 inch sheet (US standard), then you will have to print the files with -A, -B, etc. suffixes on the filenames, then cut them out on the match lines and paste them together. If carefully done, you should still get VERY accurate templates for cutting.

NOTE ON MATCH LINES:
The way I draw the match lines is so the match lines on adjoining partial drawings FULLY OVERLAP. The match lines are drawn two pixels wide. What you will do is cut and paste them so that the Match Line 1 on PART B exactly covers the corresponding Match Line 1 on PART A. Another way of saying this is that the two-pixel width of the match lines on the two drawings are the SAME TWO LINES OF PIXELS on the final drawing. The match lines do NOT butt together; they EXACTLY overlap! I hope this is sufficiently clear for all to understand.

L Cottrill
Attachments
Lady_Guinevere_intake_plan.jpg
Full-size intake plan, including sheet pattern. This was brought over from the original thread for the sake of completeness. Drawing Copyright 2006 Larry Cottrill
(266.42 KiB) Downloaded 362 times
Lady_Guinevere_Rev01_cone_sheet_2B.jpg
Lady Guinevere rear cone sheet pattern, Part B. Prints full size at 96 DPI. Drawing Copyright 2006 Larry Cottrill
(115.51 KiB) Downloaded 380 times
Lady_Guinevere_Rev01_cone_sheet_2A.jpg
Lady Guinevere rear cone sheet pattern, Part A. Prints full size at 96 DPI. Drawing Copyright 2006 Larry Cottrill
(154.44 KiB) Downloaded 345 times
Lady_Guinevere_Rev01_cone_sheet_2.jpg
Lady Guinevere rear cone sheet pattern. Prints full size at 96 DPI, but larger than 8.5x11 inches. Drawing Copyright 2006 Larry Cottrill
(214.98 KiB) Downloaded 365 times
Lady_Guinevere_Rev01_cone_sheet_1D.jpg
Lady Guinevere front cone sheet pattern, Part D. Prints full size at 96 DPI. Drawing Copyright 2006 Larry Cottrill
(85.27 KiB) Downloaded 350 times
Lady_Guinevere_Rev01_cone_sheet_1C.jpg
Lady Guinevere front cone sheet pattern, Part C. Prints full size at 96 DPI. Drawing Copyright 2006 Larry Cottrill
(99.89 KiB) Downloaded 341 times
Lady_Guinevere_Rev01_cone_sheet_1B.jpg
Lady Guinevere front cone sheet pattern, Part B. Prints full size at 96 DPI. Drawing Copyright 2006 Larry Cottrill
(101 KiB) Downloaded 372 times
Lady_Guinevere_Rev01_cone_sheet_1A.jpg
Lady Guinevere front cone sheet pattern, Part A. Prints full size at 96 DPI. Drawing Copyright 2006 Larry Cottrill
(181.74 KiB) Downloaded 351 times
Lady_Guinevere_Rev01_cone_sheet_1.jpg
Lady Guinevere front cone sheet pattern. Prints full size at 96 DPI, but much too large for 8.5x11 inches. Drawing Copyright 2006 Larry Cottrill
(288.33 KiB) Downloaded 383 times

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re: FWE From Outer Space - Revised Lady Guinevere

Post by larry cottrill » Fri Oct 06, 2006 2:40 pm

Just a brief progress report:

All the cones are welded up. The mid cone and choke cone are fully welded together, and the front dome is fully welded onto the chamber cone, with the spark plug mount welded in place. I wanted to use a larger plug on this engine, but couldn't find a metric nut to fit even the smallest chain saw or leaf blower plug I could get, so I went back to the tried-and-true M10x1.0 format that fits my customary CM-6 plugs. Oh well.

There are minor problems of fit with joining the chamber to the mid cone and the tail skirt to the tail flare. There are two reasons for this: (a) I cut the chamber and tail cones from enlarged copies of my earlier small-scale drawings (since I cut them back in March or April, before I had the full-scale patterns published above), and (b) my air shear cutting technique is not as precise as I thought. Probably, what I'll have to do is resort to hammering slight flares in the pieces so they will 'socket' together slightly. This will cost me a tiny bit of overall length, but I should still come in within Mike's 32-inch contest criteria. The intake should fit perfectly, the only potential problem there being the hammering down of the wide front edge where it welds into the front of the rectangular hole in the chamber.

I'm sure there's not a perfectly circular cross-section anywhere, but it should be close enough. No pictures yet, unfortunately. Thought I'd be farther along by now, but what I've done so far looks pretty good, so I'll not complain. I should have a few pictures later on, maybe late next week.

L Cottrill

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re: FWE From Outer Space - Revised Lady Guinevere

Post by leo » Fri Oct 06, 2006 7:46 pm

I hope you get it running, would be something new.
If its impossible to start, (but only after serious attempts) you can always closed the gap in the tail.
I’ am waiting on the results of this experiment with much interest.

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re: FWE From Outer Space - Revised Lady Guinevere

Post by steve » Fri Oct 06, 2006 9:14 pm

wow, I leave for awhile and when I come back to visit, I see this!

my god Larry- what has become of the FWE? it used to be so lovely and simple! there was only one cone in the entire thing, and now look at it! I can't, its too frightening...

just kidding~ looks awesome! hopefully it will run well

good luck to everyone involved in its production
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re: FWE From Outer Space - Revised Lady Guinevere

Post by milisavljevic » Sat Oct 07, 2006 12:35 am

Larry Cottrill wrote: This will cost me a tiny bit of overall length, but I should still come in within Mike's 32-inch contest criteria.
Hello Larry --

As an aside, the contest criteria allow for a maximum physical length of 33 inches, excluding the spark plug.

Good luck with this one!

Best regards,
M.
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re: FWE From Outer Space - Revised Lady Guinevere

Post by larry cottrill » Sat Oct 07, 2006 3:48 pm

Steve -

Good to hear from you at last! Hope all is well with you.

Eric has also bemoaned the seemingly lost simplicity of the FWE series. To see where this new shape comes from, check out the much earlier 'Lady Anne Boleyn' thread:
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=3271

L Cottrill

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re: FWE From Outer Space - Revised Lady Guinevere

Post by Eric » Sat Oct 07, 2006 11:58 pm

Seemingly lost?! :)

Its definately not something the beginner can take on in a few hours and wind up with a beautiful simple little engine.

The linear FWE is even more simple, the least work of any engine design, except perhaps for the kazoo's but a lot of time goes into making the press equipment and such.

But who am I to complain, all I seem to make are chinese and crazy valveless contraptions with umpteen different segments and cones.

Eric
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Re: re: FWE From Outer Space - Revised Lady Guinevere

Post by larry cottrill » Sun Oct 08, 2006 1:42 am

milisavljevic wrote:Hello Larry --

As an aside, the contest criteria allow for a maximum physical length of 33 inches, excluding the spark plug.

Good luck with this one!

Best regards,
M.
M -

Correction noted; however, I am concerned about cutting short rather than long. At this point, everything (re parts dimensions) is pretty much cast in stone.

Thanks! We shall see. The proof of the putting is in the heating. Ha ...

L Cottrill

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re: FWE From Outer Space - Revised Lady Guinevere

Post by milisavljevic » Sun Oct 08, 2006 2:40 am

The proof of the putting is in the heating.
Hello Larry --

Does this mean that if the "Lady Guinevere" is unsuccessful as a pulsejet, that you will use it for GOLF???
This "little lady" of yours seems just a tad short to make a good putter... =)

Good heating! =)

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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