Any major flaws with this valve design?

[TonyG]

Hi, I am still working on my large pulse jet, 200lb of thrust, and well am working on the valve design. I know that one person said that 30 degrees was a good angle for the valves, but I can't seem to get enough valve area into that angle. The set of valves I am looking at making will be at 60 degree angles. There will be 32 valves total, with a total cutout intake intake area 60.375 inches before I put the spring steel vavles on.
Also, I have not been able to find much on spring steel thickness, but am thinking that I will probably need somewhere in the area of .010 thick, or will this be too thin/thick?
Also, are for attaching this to the engine, I am debating about either drilling holes about every 1 inch around the circumference and bolting it the engine, or I could weld it on. The valve plates will be made out of 1/8 inch thick stainless steel. The spring steel will be mounted on the inside of the valve plates, each peice held in place with a retainer and 2 screws which will come in at a 45 degree angle to the valve plates.
I would have loved to have gone with a valve grid like was used on the argus engines, but it is going to be too much trouble to deal with, as the person who is going to cut these for me is doing them by hand.

Here are some links to my design:

http://members.cox.net/tgi/pulsejet/Val ... te%201.jpg
http://members.cox.net/tgi/pulsejet/intake.jpg

Almost forgot, the diameter of the intake is 11.625 inches, total length of engine is 81.25 inches and the exhaust diameter is 8 inches.

The peice of stainless steel I have to build the valves out of is 48 inches long by 13.75 inches wide and .125 inches thick. So I have quite a bit to play with.
Thanks,
Tony Ithaca

[TonyG]

I plan on trying to get the design to the machinist this evening after work, so if anyone sees any problems with the design please let me know.

[Mike Everman]

The only suggestion I see is that the corners on your passages will be rounded, you should accept something like 1/8 to 3/16 radius fillet, so your machinist can use a 1/4 to 3/8" dia end mill to do the cutting. don't be shocked at the price of doing this, if it's the 1/8" stainless you were talking about, it's going to take quite some time to cut.
Having a freind with a laser or water jet cutter is good advice for anyone, but mostly hard to find. either would make short work of this, as would a programable sheet metal punch (then you could keep the sharp corners in the openings).
good luck with the beast.

[TonyG]

Thanks for for tip, I will talk to him and see what he says. He will probably do the work for free, and what he can't do with his own equipment he can take to work with him and cut it there if need be. Fixing to head over to his house in a few minutes so we will see what he says.
Thanks,
Tony Ithaca

[jmhdx]

Hi, glad to see plenty of folks still building the external combustion engine, but dissapointed too see so many valved models. Anything that obstructs the passage of air through the engine for even a percent of the cycle is defeating the object; to accelerate passing of same air; and is a fundemental inefficiency. With so many possible forms for a valvless engine I hope you can design a component free intake for your big engine. I will upload some designs I've worked on when I have time.

[jmhdx]

Hi, glad to see plenty of folks still building the external combustion engine, but dissapointed too see so many valved models. Anything that obstructs the passage of air through the engine for even a percent of the cycle is defeating the object; to accelerate passing of same air; and is a fundemental inefficiency. With so many possible forms for a valvless engine I hope you can design a component free intake for your big engine. I will upload some designs I've worked on when I have time.

[Mark]

Let's see you make a svelte light-weight short streamline pulsejet without using valves.
Mark

[Bruno Ogorelec]

Anything that obstructs the passage of air through the engine for even a percent of the cycle is defeating the object; to accelerate passing of same air; and is a fundemental inefficiency.

Well, I'd say that 'obstructing the passage of air though the engine' is the name of the game in pulsejets. What is dumping of ingested air into a broad chamber, with its attendant strong turbulence, but an obstruction of flow? What is the stopping of incoming flow when the engine is refilled with fresh charge but an obstruction of flow?

In fact, talking of flow in pulsejets, one must be aware that the term is to be taken with a pinch of salt. Instead of flows, we should really be talking of pulses. That's what makes pulsejets so different from other jet engines, what makes them function with few moving parts or even without any, and what adds a lot of frustration to the process of their design.

Yes, valves can be seen as a kind of obstruction, but -- as a rule -- they still make for greater efficiency. It is difficult to match that efficiency with a valveless design. If reed valves were as durable and reliable as poppet valves are in piston engines, few designers would even think of making valveless pulsejets.

[TonyG]

Hi, just thought I would mention that I was finally able to get a hold of the guy that was going to cut these for me, though it seems he doesn't have the needed equipment to do something like this.

I am now looking at ordering it through emachineshop.com. It looks like from them it will cost around $150 to have the parts made and about $180 for two sets. If I go this route, I will have to go with .197 thickness stainless steel.

Does anyone have any comments on their work?

[jmhdx]

Thankyou Bruno for extrapolating the details of pulse combustion and the flow of air through an engine, you are correct that some obstruction is inevitable, but I have included augmentation and the passage of much air through my latest design and some obstuction of some of the passing air is the best I can do. I also agree that the closed end approach does provide, by far, the greatest amount of thrust and have included this principle in my designs. On a personal note "Valves Have Got To Go!", I will not build an engine that has moving parts. It was your excellent page on valveless engines that started my unstoppable obsession with this goal.
Thankyou and I hope I haven't disheartened TonyG from completing his design, you learn a lot more from a working valved engine than a hollow tube.

[Bruno Ogorelec]

the closed end approach does provide, by far, the greatest amount of thrust and have included this principle in my designs. On a personal note "Valves Have Got To Go!", I will not build an engine that has moving parts.

Sounds very interesting. I hope you will keep us posted on developments.

[Mike Everman]

Dear jmhdx, planet earth, milky way galaxy:
I'd like to propose that you introduce yourself, and perhaps start a thread with the general design of your engine. there is a lot of good opinion and resources to help here.

[Mike Kirney]

Also, are for attaching this to the engine, I am debating about either drilling holes about every 1 inch around the circumference and bolting it the engine, or I could weld it on. Thanks,
Tony Ithaca

The longest the valves have lasted on ANY pulsejet ever is about half an hour so you are definitely going to want a valveplate that you can remove and refurbish as need be. I used bolts on mine. One every inch seems a little excessive but what do I know, my jet didn't work and nobody wanted to buy it either. Incidentally, the Tundra-Jet will be back on E-Bay in a few days, this time with new pics and another price rollback. I'll even throw in a box of 'Turtles' and a couple of back-issues of Penthouse if that's what it takes to get this thing out of my house.

[dynajetjerry]

To Mike Kirney, I must say "Tain't so!" His statement in 2004 that pulsejet reed valves have never lasted longer than 1/2 hour in any design was not true in 1951 and I have evidence to that effect.

Aeromarine's 8 in., 205 lb. thrust pulsejet was developed to power a USN target drone. After several modifications, one example ran for 10+ hours before the reeds began to leak and need replacement. If that company had stayed in business, it is entirely probable that, eventually, other improvements would have been incorporated that would have provided greater efficiencies and working lives from their pulsejets.

At a time when the most efficient of small turbo-jets usually had a specific fuel consumption of about 2.0 lbs. fuel/hr./lb. thrust, the 8 in. pulsejet equalled that figure and at a vastly lower fabrication cost. These days, of course, high bypass turbos are much, much better and pulsejets have improved little or not at all. Very little research is being done on pulsejets because of their inherent noise, vibration, and limited "throttlability." A few modifications can improve the above characteristics but at higher costs and reduced efficiencies.

Jerry

[hinote]

At a time when the most efficient of small turbo-jets usually had a specific fuel consumption of about 2.0 lbs. fuel/hr./lb. thrust, the 8 in. pulsejet equalled that figure and at a vastly lower fabrication cost. These days, of course, high bypass turbos are much, much better and pulsejets have improved little or not at all. Very little research is being done on pulsejets because of their inherent noise, vibration, and limited "throttlability." A few modifications can improve the above characteristics but at higher costs and reduced efficiencies.

Here I go again! This should probably be on the Valveless Forum, but what the heck!

Current iterations of valveless pulsejets are capable of TSFC's in the range of 1.5-1.8--or even better. This is for the raw, core pulsejet duct, with no external improvements.

Add-in the improvements that can be made with augmentation and pressure-sensing fuel injection, and the TSFC goal of 1.0 should be easily attainable.

That disregards the current potential developments, which will raise the "compression ratio" of the engine--and open up the possibility of directly competing with current fanjet engines.

All with no moving parts. Ya just gotta believe!!